175 replies to this topic

[Rick Moore]

1241.2-Cd3 (1241-Cd3 revision)

 

Back To Basics, Season Finale…

 

The last of the revised 1241 builds, the “d” dimensioned (3.750” WB, 4.875” RAx-GPC, 1.125” GL) 1241.2-Cd3. Finally. This gets the 1241’s up-to-date with the 1254’s, 1256’s, 1259’s, and 1258’s, and keeps “c”, “d”, and “b” dimensioned versions of all five designs… Sheesh.

 

This 1241.2-Cd3 actually replaces three previous 1241-Cd3 chassis/cars in the active CMF3 CanAm slot car stable. After I built/tested the original 1241-Cd3 I decided to build two more 1241-Cd3’s to have three of the same chassis to try set-up variations (for those who get a “buzz” from the lack of blood going to their brain trying to figure out the CMF3 chassis ID’s, the two copies were the 1241-Cd3/2 and 1241-Cd3/3). They’ve served their purpose, and all three 1241-Cd3 chassis join the 1241-Cc3 and 1241-Cb3 originals in retirement from the active CMF3 slot car stable...

 

The “d” dimensioned chassis are by conventional-wisdom scratchbuild slot car freaks when looking solely at the unusually long GL (1.125”) with the atypical shorter WB (3.750”). However, ignoring those numbers leaves the more important RAx-GPC of 4.875”, which is fairly common, albeit in this case with the front axle/wheels a bit further behind than would be typical for that value. Is this a “better” dimensional lay-out for these cars? Don’t know. Probably subject to debate. What I do know is I’ve built a bunch of “d” chassis in the 1219-Series and 1237-Series, that I like them, and have yet to find a reason not to build them. Your results may vary…

 

Anyway, with an adieu to this phase of back-tracking in the 1237-Series, and without further ado, the 1241.2-Cd3:

 

 

 

 

 

 

 

More groans. And more of the same, with more of the not the same... In another vain attempt to mollify the repetitive boredom I posted up pre-roller pics this time. Please try to contain your excitement.

 

Pre-Pb off-the-build RTR mass for the 1241.2-Cd3 came out to 99.6 grams (with CR-102; versus original 1241-Cd3 with lighter JK-HR at 101.1 grams), post-Pb at 100.4 grams. Not sure why the 1241.2-Cd3 came out about 1.7 grams lighter than the 1241.2-Cc3; hopefully it’s not because I forgot to solder a lot of it together…

 

No Test Yet:

 

Planned to go to Fast Eddie’s today for some general testing and get the 1241.2-Cd3 on the track, but I weenied out. Two factors contributed to this: One, it’s been raining cats-and-dogs in Tampatown, and anyone familiar with the relationship between geography, meteorology, and demography of South Tampa where I live will understand most of the streets are flooding with every possible moron driving like they deserve that description. And, two, work at the hospital has been brutal of late and I’m pretty much exhausted, too many traumas while yet again the hospital fills with another wave of COVID patients. I’ll minimize any further statements regarding the latter part of reason two, sufficing it to say most healthcare workers are over all the continuing verbal support from a general populace that appears to have completely lost their marbles.

 

Besides, considering how the 1241.2-Cb3 and 1241.2-Cc3 fell right into place with testing it is a pretty safe assumption the 1241.2-Cd3 will also fall in line accordingly. Maybe confirm it next week; see how I feel then. If the 1241.2-Cd3 does not run as expected, I’ll make reference later, otherwise y’all can assume (we all know what that stands for…) along with me…

 

Hey, it’s not like it’s the first time a season finale was a dud.

 

Think I’ll get back on the drafting board and finish up the final draft for that next chassis, maybe even get the finger-burning phase started tonight…

 

Keep your boots on, it’s getting deep…

 

Rick / CMF3

 

[Tex]

beware... the OCD is strong in this one.  LOL

[Eddie Fleming]

 However, ignoring those numbers leaves the more important RAx-GPC of 4.875”, which is fairly common,

 

Rick / CMF3

 

I am using the Rax-Gpc as the starting measurement in all my newer builds. Then letting the front wheels fall where they need to for the body or the rules. 

 

I do enjoy your posts Rick.

[Rick Moore]

Hey there, Eddie!

 

The RAx-GPC dimension has been my starting point of any chassis design, even the Just-For-Fun cars, for many years now. I stopped building relatively long 5.00” RAx-GPC CanAm and GTC (“a” dimensioned, 4.00 / 5.00 / 1.00”) during the 1219-Series builds, and instead built first 4.750” (“b” dimensioned, 3.75 / 4.75 / 1.00”) and then 4.875” (“c” dimensioned, 3.875 / 4.875 / 1.00”). I had already tried shorter GL’s less than 1.00”, but that seemed to be the minimum that I found. But I hadn’t tried longer GL’s, so I got the idea to use the “b” 3.75” WB with the “c” 4.875” RAx-GPC, making the “d” dimensioned chassis with the resulting 1.125” GL. (Subsequent F1 chassis, with their minimum WB, would bring about the “e” dimensioned chassis, 3.875 / 5.000 / 1.125”, one I have not tried for a CanAm or GTC.)

 

All the 1237-Series CanAm and GTC frames have been “c”, “d”, or “b” dimensioned frames. What I’ve found is just about any dimensioned chassis will run well in ideal track conditions so it comes down to a matter of best set-up. As a generalization, with the right set-up, the “b” cars can be crazy fast, the “c” cars will just turn fast lap after lap, and the “d” cars are some degree of both (more “c” than “b”, more “b” than “c”, or pretty even) depending on the chassis design. But when track conditions are too little or too much rubber the “d” cars seem to rise to the occasion with little loss in overall performance more so than the “c” or “b” cars. I have no idea why. No doubt someone can explain this, or even explain this away. Could even be peculiar to the particular frames I build. But I’ve built a lot of these, and as I said before I have yet to find a reason not to build 3.750 / 4.875 / 1.125” “d” cars. I don’t know if others have tried building multiples of the same chassis design with typical (somewhere around 0.90” seems to be the “standard”) and longer > 1.00” GL’s, but my assessment is it is worth a try.

 

(That is, OCD notwithstanding. Tex, nice to see you’re development towards becoming an old coot stating aloud for everyone that which is plainly obvious is coming along nicely.   )

 

Rick / CMF3

 

[Tex]

lucky for you I couldn't find my cane to wave wildly above my head, shouting something about my lawn!  LOL

[Bill from NH]

Funniest old guy with a cane I ever saw was a man in the middle of a crosswalk in Manchester, NH. When an oncoming car didn't stop, as they're supposed to. the old man hit the car with his cane. The car stopped abruptly & an angry young driver jumps out. The old guy stood his ground & shouts, "Sonny, you better get back in that car because the next thing this cane is going to rap is your head."

[Rick Moore]

C'mon guys, we shouldn't be making fun of old guys. Fer cripes sake, this is a slot car forum. The vast majority of us are only a few credits away from being degreed curmudgeons. Instead of the grandkids we come on here and say, "Hey buddy, let me show you some pictures of my slot cars..."

 

(Is this thread drift? Who are you anyway? And why did I come in here? What was I doing? I need a nap...    )

[Bill from NH]

Rick, I am an old guy, I past age 70 a few years ago. I'm also already a degreed curmudgeon.    Does that put a new bend in your wires? Besides, it was Tex who brought up swinging canes first..  Oh yuh, I use one to get around with, it's a Drive.  The story I told was a true one that happened in the 80's. Now don't ask me what I had for supper.   (It was chicken, a potato, & coleslaw.) Have fun building your slot cars. Isaac S. in IN also has an Align-O-Jig. A couple weeks ago, I sent him a copy of the instructions. Soon you two can have an Align-o-Jig war. Okay, this thread is now back on topic.  

[Rick Moore]

A228.2-c3

 

A break from the CanAm cars, but not the back-tracking, it was time for another F1 class chassis build. Maybe more of a lateral move than a back-track. The last F1 chassis was the A228.2-e3, and this new one was going to be a dimensional variant, the A228.2-c3, but for different reasons than the “c” rebuilds in the CanAm frames.

 

I had previously built one F1 chassis design in both 0.039” wire and 0.032” wire, respectively the A216-e2 and A216-e3. Those two builds of the same chassis design would confirm 0.032” wire as the preferred medium for the 1237-Series based F1 class chassis. However, at the same time the A216’s were my first “e” dimensioned F1’s, where the previous frames had been “c” dimensioned, being another one of those changes I had made back then on “a whim and a lark”. There was no one frame design built in both “e” dimensions (5.000” / 3.875” / 1.125”) and “c” dimensions (4.875” / 3.875” / 1.000”). It was time to rectify that oversight. (For those who might be paying too much attention to all this, you poor suffering souls, I have not built an “a” dimensioned chassis, 5.000” / 4.000” / 1.000”, since the 0.039” wire framed 1229’s, part of the 1219-Series, way back in 2013.)

 

Performance-wise either the A226 or A228 were prime candidates, and even after much blank-staring time I continued to waffle between the two…

 

One peculiarity of the A228 (or the unbuilt A227) is that the rear axle tube upright support wires are superstructure, wires added atop the chassis main frame, a novel approach I tried on the A401-01, which was an anglewinder but the concept was applicable to in-line rear axle tubes also. On all other builds the rear tube supports are main frame wires with upright bends, no doubt an engrained practice leftover from the 60’s. For the vast majority of scratchbuilders the difference is inconsequential, since the motor bracket is the major structural element of the chassis rear, and in many cases do not even use rear axle tubes. My designs and builds are bass-ackwards in this regard, again dating back to the 60’s where the structural and/or dimensional integrity of motor brackets were not always all that great, and upon my return to slot cars and scratchbuilding in the 90’s where in-line motor brackets, pre-retro craze, were largely non-existent and I just didn’t use them. So, as a matter of habit, I still build the frame supporting the rear axle tube first, with structural emphasis on this component, then add the adjunct motor bracket later (or I could even build them without the motor bracket if I wanted). The A401 and A228, using superstructural rear axle tube supports, take this a step further, allowing me more design possibilities and structural layouts for the rear motor/drive assembly of the chassis main frame, as well as more options for the rear axle tube supports.

 

I would find out the A228.2-e3 has excellent structural integrity. At the last GRRR event I attended I ran the A228.2-e3 in the F1 race on the Oval at Fast Eddie’s. These are some scary-fast races. Things happen quickly, and bad things even quicker. The front bumper on these F1 chassis has become my new best friend. During the race the A228.2-e3 would take, not one, but two open-wheel launches in the bank; you know, the ones where the tires of two cars interact in such a manner to send one spectacularly flying through the air, often with disastrous results. Despite the two launches with gruesome sounding landings the A228.2-e3 kept running and won. Post-race tear-down showed virtually no damage to the chassis, just one side pan pushed in slightly, and pulled it right back out with my fingers. My first thought was I need to build another one of these… Ding ding ding! We have a winner…

 

Another peculiarity of the A228.2-e3 is that it was built to fit under the Oleg Lotus 63 body (as was its predecessor, the A226.2-e3), but also has an interchangeable sissy bar so it can be switched to any of the various McLaren M7 bodies for comparison purposes. Since then I was able to get a few of the Oleg Brabham BT26 bodies. The Oleg Brabham has a shorter front end relative to the Oleg Lotus, so the Brabham will not fit atop the A228.2-e3 (or A226.2-e3). Since the plan was to build a slightly shorter “c” frame anyway, this A228.2-c3 frame would have a shorter front end also, and along with an interchangeable sissy bar would be able to again fit the McLarens and Lotus, as well as the Brabham.

 

The A228.2-c3:

 

 

 

 

 

 

 

 

 

The A228.2-c3 was set-up with the Oleg Brabham body only at this time. I’ll get around to trying other bodies at some point… Didn't screw up the paint job too bad.

 

As a matter of physical comparison between the Oleg Brabham BT26 and Oleg Lotus 63 bodies, for those of you who have not been able to get your grubby little slot car hands on both, besides the Brabham being about 0.125” shorter than the relatively long Lotus along the straight side of the body (rear of body to under forward aspect of front wing), the Brabham also has a slightly lower profile and a longer rear wing. And, like the Lotus 63, the Brabham BT26 looks great. Performance-wise I can only offer limited data, as the only comparison I’ve done is on the Oval track at Fast Eddie’s where the F1 body seems to be less critical; on the A228.2-e3 I was getting pretty much the same lap times whether I was using one of the McLaren dish-drainer bodies or the Lotus 63. (Limited testing on the Hillclimb also showed no difference, but the key word is limited.) I imagine on other road course tracks any differences might be more pronounced. But for my purposes on the oval there was nothing in the physical characteristics of the Brabham to indicate the result would be any different.

 

If I recall (equals “too lazy to look”) the previous A226.2-e3 and A228.2-e3 came out about 97 grams off the building slab before their mandatory plumbum addendum. I was expecting the slightly smaller A228.2-e3 in RTR trim to come in under that, though slightly offset with the slightly heavier new preferred pony power. Came out at 95.2 grams, before being loused with lead to 100.5 g, with only about 0.9g for the LTO bias…

 

Test Time:

 

In this case more like dorking around on the Oval, pre-SoRetRumble. All I needed to see was how the A228.2-c3 compared with its older and slightly bigger A228.2-e3 sister. Of additional curiosity for this test run, previously only having tried a few cursory laps with obviously insufficient teeth to chew up the footage, the F1’s now have two pretty even mediocre CR-102’s in them, with correspondingly ludicrous gear ratios, shoving them around the Oval.

 

The A228.2-c3 ran every bit as good as the A228.2-e3 I’m happy to report, both turning much better laps with what were fairly pedestrian motors when run on the Hillclimb. Curiosity got the better of me, so I put a better set of tires (as opposed to my default test tires) on the A228.2-c3 and it turned the fastest laps on Orange and Purple any of my F1’s had ever done. That was a surprise I can certainly live with. Considering I’d previously tested the A228.2-e3 with the Lotus and McLaren M7 bodies, I doubt there will be any difference with the Brabham as well. And the Brabham just looks cool. Dang good for right out of the box.

 

So that’s that for now. In the grander scheme of things I have to consider the possibility of a design/build of a 1237-Series CanAm frame using the A228’s motor-drive assembly with superstructure rear axle tube uprights. For sequential purposes this would most likely be a redesign of one of the existing “core” frames, 1241, 1254, 1256, 1259, or 1258, with some convoluted addition to the ID numbering system… When? Who knows. Eventually maybe would be the correct time frame.

 

Enough of this slot car stuff. Maybe we should all do something more meaningful… Yeah… right…

 

Rick / CMF3

 

[Eddie Fleming]

Some more detail of you Sissy bars (photos) would be interesting. 

[Rick Moore]

Sissy Bars

 

Greetings, Eddie!

 

There was a post way back on Page 2 / Post # 39 when I started adding the “sissy bar” (as we called them back in the 60’s) as a standard component to all the 1237-Series chassis, when I found it improved the performance of every car at that time. No doubt the functional value of sissy bars is debatable, but testing on my cars showed they were beneficial, so I use them.

 

Here’s a repost of the pic from that post showing a typical 0.024” wire sissy bar under a clear body:

 

 

 

The wire is just two 90-deg bends with the ends curled to attach to the rear axle tubes. Pretty simple. Variations of sissy bars have been around since the 60’s. Back then they tended to be heavier wire, but I’ve found the smaller 0.024” wire with two attachment points is sufficiently strong enough while adding a minimal amount of mass at the higher elevation.

 

On Stock Cars, with the long rear end on the bodies, I do not run the sissy bar all the way to the body’s rear spoiler, instead extending it to support the body about 2/3^rd’s back on the body’s rear deck.

 

For the interchangeable sissy bar the wire basic structure is the same except it is 0.032” wire. Then it’s just a matter of adding the 1/16” tubes. Here’s some close up pics of the A228.2-c3’s sissy bar set-up:

 

 

 

 

Using the lowest/shortest body to be used (mounted to the chassis without rear running gear and placed upside down), the steps to make an interchangeable sissy bar set-up goes like this:

 

1) Form 0.032” wire with two 90-deg bends (keep the wire side lengths longer than will be needed, but able to fit into the area you’re working);

2) Cut two 1/16" tubes to fit wire side lengths from rear axle tube to the top cross wire portion of the sissy bar (ensuring the tube will not drag on the body; if it does, trim tubes shorter, then using the cut off portions as spacers during set-up);

3) Remove the tubes and cut the wire sides approximately two-thirds the length of the tube from where the wire enters the bottom of the tube (at the rear axle tube).

4) Bend the two cut off lower wire ends to wrap the rear axle tube, and trim off any excess length.

5) Reassemble loose sissy bar component and tack solder lower wires / tubes to rear axle tube (solder will wick into the tube).

6) Check the fit, remove the body, and fully solder lower wires and tubes in place. (Optional: A cross-wire can be added between the two tubes for greater structural strength.)

7) Mount on other bodies and simply make taller/longer additional 0.032” wires that insert into the tubes to fit.

 

The only reason I use the quick-change sissy bar is so I can test different bodies quickly. Otherwise it really isn’t all that difficult to change a single piece sissy bar when changing the body to be used or the mounting position.

 

Of course, among other reasons the main purpose of the sissy bar is to apply whatever downforce created by the body’s rear more directly to the rear axle (and not the rear body mount pins). Sissy bars can still be used when there are no rear axle tubes or access to the rear axle tube is limited. Just keep in mind the attachment points for the sissy bar should be as close as possible to the perpendicular line from the rear axle to the chassis bottom.

 

And before anyone even considers it, especially all the curmudgeon-types, we have all already heard all the “sissy bar” jokes…

 

Rick / CMF3

 

[Bill from NH]

We ran those bars on open class wing cars during the 1970s too. We didn't call them sissy bars  & used .032  piano wire because that was the smallest diameter commonly available back then. Most hobby shops & raceways stocked foot lengths of K & S .032, .047, .055, & .063. It was all plated & each size was a nickel per foot.                      

[Rick Moore]

The “sissy bar” nomenclature was definitely a “60’s thing”. While sissy bars on motorcycles had been around for years, it was the advent and popularity in the mid-60's of the pre-BMX “wheelie bikes” with their high-rise handle bars, banana seats, and sissy bars that was the more familiar source of the name. Any typical picture of the outside of a slot car raceway of the day would include a pack of parked wheelie bikes kids rode to the track. Sissy bar as a tongue-in-cheek pop culture reference to its similar location and appearance contributed to its becoming part of the ever-changing and diverse slot car slang of the time, besides being easier to say than “rear body wire support”…

 

R...3

 

[Bill from NH]

I'm familiar with "sissy bars" on motorcycles. A brother had them on a Yamaha. In New England, we called body braces "body braces." Some were "U" shaped. others were "Y" shaped. It doesn't surprise me the body braces were called something else in other parts of the country. Do you drink soda, pop, coke, or something else? Do you use a bathroom, latrine, backhouse, or a tree? My mother-in-law is from Ireland, she taught me about flexes & flannins.

[Rick Moore]

Yeh, Bill, valid point on the geographical peculiarities of local parlance, especially back in those dim dark ages of the past, with three TV networks (four if there was a local PBS channel), AM radio, city-based newspapers, and magazines where the articles were typically at least three months after the fact, where influences tended to be framed by a range of miles instead of the high-tech global interconnected brouhaha we are wallowing in with our present day and age.

 

The slot car hobby was no less localized. Slot car periodicals would show an article of the “latest” slot car and by the time you saw it the thing was already obsolete, the pace of change in the hobby increasing this factor all the more so. My own point of reference in the at-the-time NW suburban hinterland boondocks of Baltimore (throwing dialect into the mix, you could tell which part of MD, and in many cases even which county and part thereof a person was from just by how they pronounced the name of the city and the state), and like any other slot car outpost we progressed into the hobby with our own oddities within the general timeline.

 

I have to preface this by stating at the local raceway (there were a lot of them all over the place then, two just in my small ‘burb-town alone) where I was a regular, albeit just a “kid”, we raced on a monster 240’ Mila Miglia “Glas-track”. That alone makes our minor participation and largely insignificant contribution to slot car history carry a big asterisk (as in: * not normal).

 

When I started scratchbuilding the minimalistic main framing used 1/16” brass tube with 0.032” wire inside, with the Lotus 40 immediately becoming the hot body when it appeared. Rules at our local raceway had a maximum width of 3”, but required front and rear wheels to be covered by the body, with no flaring allowed. Unfortunately many sports car bodies were more to “scale” and were often less than the max width, so we started building open-wheel Indy/F1 bodied cars that were exempt from the body covering criterion, the chassis framing being comprised of steel wire; slot car missiles, basically; great fun. Shortly thereafter we went back to sports car bodies when the raceway rules changed to allow flaring and add-on rear spoilers; about that time bodies were starting to get wider as well. When the brass wire frames first came along (the term “jail door” never used in our small niche), the majority of us, myself included, tried building these, but there were a few holdouts who built the same style of chassis frames still using steel wire instead, like we had on our open-wheeled cars. Me and the other brass wire chassis builders would learn the error of our ways, as the high-speed crashes on the Mila Miglia would invariably make our brass rod creations FUBAR (or in our local slot car vernacular, “defunct”), and we all went back to steel wire frames, even though the brass wire chassis would continue in the majority of slot car elsewhere.

 

It was during the early part of my brass wire brain-fart period, on my latest chassis with a new McLaren M1B body (erroneously labeled a “McLaren Mk 2”) I copied one of the other local builders, as did just about all of us, who had added a two-bend 0.062” steel wire with the ends attached to his motor bracket that ran up to the rear spoiler of his Lola T70. Which of us used the term “sissy bar” first I couldn’t tell you, but it stuck within our raceway group.

 

I’m getting thirsty. Think I’ll go get a soda…

 

Rick / CMF3

 

[old & gray]

Thread drift – 

In Jan 2005 my wife and I took a few day vacation to Dublin Ireland. Being off season prices were down: flight was $110 and the $275 a night hotel was $70 with the full breakfast. As we stood in line to have our food cooked to order while we watched, we realized it was food and a show. Based on the accent when you placed your order for eggs and meat the chef was guessing the location and TOWN where each guest came from, (primarily from England). When we ordered he hesitated a moment and said “northern United States, eastern, possibly Canada.” Local parlance and dialect still go a long way in identification. 

End of drift –

 

I remember the sissy bars back before 1971. At that time the rear panel on the body had a minimum length which I remember as being below the axle height. The sissy bar would not only transfer downforce from the spoiler but also deter the back panel from “sucking in” on the tires and gear.

[Rick Moore]

1243.2-Cc3

 

My previous schedule (translation: vague idea) of builds after the 1241 revisions came to an abrupt halt. Any thought of building “c” dimensioned versions of the 1270-Subseries and 1277-Subseries chassis got put on hold. Instead I decided to continue with variations of the 1256.2-Cc3 and 1258.2-Cc3 chassis. Besides the design sequence variations still possible, these two chassis are always top performers, regardless of track lane or conditions, making for an easy change of direction for the next builds.

 

A quick 1237-Series refresher, so you don’t have to do all that looking: When I designed the 1254 (single center main rail) – 1255 (diverging main rails) – 1256 (diverging main rails with iso-guide) sequence I incorporated a re-design of the rear motor/drive assembly that made the motor/drive assembly longer and effectively shorten the length of the main rail compared to the 1241 design; a similar design of the motor/drive assembly for the 1259 – 1257 – 1258 sequence was applied but with a shorter motor/drive assembly and longer main rail, though still shorter than the main rail on the 1241. The thought at that time was those revisions would make the two 4x 0.032” wire main rails on the 1256 and 1258 (compared to the 8x 0.032” wire single center main rails) more structurally viable.

 

Left out of this mix at that time, and until recently, was the notion of ever building a diverging main rail / iso-guide version of the 1241 design, based on the presumption the diverging main rails would be too long, my concern being the amount of vertical bending (or flexure) the main rails might exhibit (not so much the amount of rotation, or, more properly, torsion, which I figured would be fine). While building the recent 1241 revisions and playing around with them at various stages of the builds, I began to consider that this presumption just might have been wrong, and that a “diverging main rail / iso-guide 1241” might be a possibility after all.

 

Also influencing this revision in my thinking was some fiddling around with the layout of spine wires (wires placed atop the main framing to add strength/rigidity) on some JFF builds, and the revision of the spines I had already done on the 1241 revision builds. The step-wise addition of superstructure to the main frame is such that the spines are added after installation of the rear static pans, buttress articulations, and side pan restrictors; at that point in the build I can get a good look at the chassis frame to see what it is doing. My thinking was if the main rails did exhibit more vertical flexure than wanted I could probably counter this by adding some spines at the rear of the main rails. With some additional playing around and questionable mathematics I figured these additional spine wires would be at the most no longer than 0.5” long, which seemed more than reasonable. And that was only if they were needed at all…

 

This was definitely worth trying, so the 1243.2-Cc3 became the next build in the Series.

 

ID # Sidebar:

About these ding-dang chassis numbers I use to keep track of all this mess (and add more confusion for everyone else): Way back whenever, after the first rough drafts of the 1241, I drew up two drag chassis, the 1242 and 1243 that had little to do with the 1237-Series, and, though the designs are still around CMF3 Headquarters somewhere or other, they have long since faded into slot car chassis scratchbuilding purgatory. Subsequently I started throwing odd-ball chassis designs into the “14XX” numerical pile, because the 1237-Series was eating up way more 12XX chassis numbers than I’d have ever imagined (thus far 1237 through 1282) with the only exceptions being the aforementioned 1242 and 1243. For a little better continuity I’ve decided to reclaim the 1242 and 1243 monikers from those MIA drag chassis designs (they can always be given 14XX numbers if they ever get resurrected) so I can use them for the two 1241-based diverging main rail designs. The 1242 design (diverging rails without the iso-guide) will probably never be built, because its cousins, the 1255.2-Cc3 and 1257.2-Cc3 have already been retired. That’s how this chassis build became the 1243.2-Cc3…

 

And all this would lead to two more designs and possible builds. The 1243, 1258 and 1256 all have the same front spanner layout. The rear motor/drive assemblies vary on these designs such that the forward apex of the rear assembly is at different points on the center line forward of the rear axle line, and accordingly behind the guide pivot center. This point where the rear assembly apex and the main rails meet I reference as the “point of convergence”, or POC, for those rails. The 1243 has the shortest rear assembly and longest main rails, the 1256 the longest rear assembly and shortest main rails, and the 1258 is halfway between them. I have in effect a “minimum”, a “maximum”, and a “median”. Now with the unbuilt 1243 design along with the 1258 and 1256 in front of me I did a bunch of doodling and more questionable math and came up with two as-yet-unnumbered designs, one having a POC median between the 1243 and 1258, and the other having a POC median between the 1258 and the 1256. If I build “c” versions of not just this 1243 but also these two intermediate chassis it would give me five chassis with five different POC’s with five correspondingly different main rail lengths. Why? You see, this whole matter of main rail length in the 1237-Series, both for the single center main rail chassis and the diverging main rail / iso-guide chassis, has been one of those annoying questions one might tend to try to ignore but never goes away, and this plan might just afford me an opportunity to assess the amount and nature of any impact this factor of main rail length might be contributing... maybe… and that is, if I can stay on course, of course…

 

First things first; the 1243.2-Cc3:

 

 

 

 

 

 

 

Dang, those main rails still look long to me. In actuality they are about 0.25” longer than the main rails on the 1258.2-Cc3. Here’s a side-by-side-by-side pic of the 1256.2-Cc (left), 1258.2-Cc3 (center), and 1243.2-Cc3 (right)”

 

 

 

As it would turn out I did not add any spine wire extensions atop the main rails for the 1243.2-Cc3, sticking with the same spine wire layout I’d used on the 1241 revisions. The extensions can still be added, but every indication on the bench leads me to believe they will not be required. Of course, this can only be confirmed on the track. Besides, I really wanted to test the 1243 in its “natural” state before using any additional structural flim-flam.

 

Two other oddities were added to the 1243. First was the inclusion of tapped holes in the top of the side pan restrictors, giving me the option to change the amount of side pan deflection (I will not even mention how long it took me to finally get around to trying this, but I figure being able to stiffen the chassis further on the 1243 was the correct opportunity). Second was moving the gear guard attachment from medial of the motor box rails to lateral of the motor box rails; this makes the gear guard wider and allows more room between the motor box rails to more easily facilitate the use some of these big honking pinions that have come into play.

 

The RTR car came out to 100.5 grams. No dreaded-lead needed.

 

Test:

 

So, how was the 1243.2-Cc3 going to compare to the its center main rail 1241.2-Cc3 progenitor, and its diverging main rail / iso-guide 1258.2-Cc3 and 1256.2-Cc3 cousins.

 

Any lingering concern about the length of the main rails was completely dispelled. The 1243.2-Cc3 ran every bit as well as the 1256.2-Cc3 and 1258.2-Cc3 on Orange, and was particularly stable and fast on the gutters, Red and Black, which was no small accomplishment when compared to the 1256 and 1258. A relatively short test evening at Fast Eddie’s, it didn’t take long to make this initial assessment… and I just kept wondering why I waited so long to get around to building this thing… Oh, yeah… presumption. Better late than never, I guess…

 

Will there be a 1243.2-Cd3 and/or 1243.2-Cb3? They certainly can’t be ruled out. But, as I said before, next on the agenda, and without the 1243’s delay, will be the “1243-1258 median” chassis and the “1258-1256 median” chassis in “c” dimensions. After that, we’ll see…

 

Silly rabbit.

 

Rick / CMF3

 

[old & gray]

"POC" has had a different meaning for me. When we built a system out of bits and pieces from the engineering parts bin and it worked we called it Proof of Concept. 

[Rick Moore]

Has another meaning, nicer version of the better known acronym... I think I've spent my entire life dealing with some POC or another... 

[Rick Moore]

1247.2-Cc3

 

From the previous 1243.2-Cc3 post, this is the first of the two “1243-1258 median” and “1258-1256 median” chassis.

 

I initially intended to start with the “1243-1258” chassis build first for no better reason than to proceed in the sequence from longer to shorter main rails. Affirmation came subsequently at the last GRRR CanAm class race at Fast Eddie’s, admittedly taking an apathetic “just run whatever seems best in the box” lazy attitude, it came down to the 1256.2-Cc3, the 1258.2-Cc3, both of which have been raced previously, or the new 1243.2-Cc3 which only had some test laps on it. As such, it seemed like a good opportunity to see what the 1243.2-Cc3 could do and to get a better feel for it in “race mode”. The car was stellar, better than the guy driving it that day by far, and while getting TQ and the win I figure the idiot on the trigger cost the car at least another six laps. That nailed it for me to build the “1243-1258” tweener chassis next, which CMF3 ID-wise is the 1247.2-Cc3.

 

ID # Sidebar, again: I am certain no one understands this mish-mash ID system, but that’s okay, it’s really for my benefit. If you could see the stacks of manilla folders strewn around Team CMF3 World Headquarters, and the ridiculous number of chassis/cars, you’d at least understand the necessity; if I’d used names instead of a convoluted number system I would have run out of names a long, long time ago (and, besides, most of the names would have been considered offensive by those of more genteel demeanors). Anyway, the previously missing 1246, 1247, 1248, and 1249 were 1237-Series designs that were variations on the 1245, all of which got put on hold after the third-and-final version of the original 1241 was designed and built, and went completely bye-bye as far as ever getting built after the 1250. Since those 1246 through 1249 variations have been explored elsewhere in the 1237-Series, I have officially relegated those designs to oblivion and reclaimed the ID numbers to cover these four possible intermediate designs:

 

1246: 1241-1259 median, single center main rail

1247: 1243-1258 median, diverging main rail w/ iso-guide

1248: 1259-1254 median, single center main rail

1249: 1258-1256 median, diverging main rail w/ iso-guide

 

For additional reference and general confusion, based on main rail lengths:

 

SCMR    DMR/iG

 1241       1243       (longest)

 1246       1247             ^

 1259       1258             ^

 1248       1249             ^

 1254       1256       (shortest)

 

For the present I am only building the diverging main rail with iso-guide (DMR/iG) chassis, the 1247 and 1249, but I wanted to keep the option of being able to also build the single center main rail (SCMR) chassis, the 1246 and 1248, should I decide later on to further explore the relative lengths of single center main rail chassis as well.

 

That ought to keep me busy for a while… One chassis at a time. The 1247.2-Cc3:

 

 

 

 

 

 

 

As for the rear motor/drive section, I probably could have kept the forward aspect rails as single rails, as on the 1241 & 1243, and simply changed the angle, but this would lengthen the motor box rails which I try to keep at their minimum length, so instead on the 1247 (and if built 1246) I used the motor/drive assembly design using lateral and medial aspect rails, as on the 1254, 1256, 1259, and 1258.

 

The 1247.2-Cc3 all set up in initial RTR trim weighed in at 99.2 grams, Pb added to 100.3.

 

Test Run:

 

Of course this initial run of the 1247.2-Cc3 would be to see how it shakes out compared with the 1243.2-Cc3 and 1258.2-Cc3, along with the 1256.2-Cc3. While it might be noted there is a good bit of age disparity going on here as well, the 1243 one month old, the 1258 one-year eight-months old, and the 1256 over three-and-a-half-years old, the continued high level of performance of the 1256.2-Cc3 after innumerable test laps and a couple of races would indicate there is a high level of consistency and durability to these designs. I hope.

 

The 1247.2-Cc3 performed just as I expected, which is always nice. If it hadn’t that would have been news, and worth an even longer drawn out post, so we should consider ourselves lucky in more ways than one. Tonight the 1258.2-Cc3, 1243.2-Cc3, and the out-of-the-box 1247.2-Cc3 ran within thousandths of each other. (FYI, the 1256.2-Cc3 was about 0.04 behind, but its last set of tires just don’t seem to be hooking up as usual…) I was a little surprised with the new 1247.2-Cc3, as I was aware the motor I put in it was a little down on “oomph” compared to the motors in the 1258.2-Cc3 and 1243.2-Cc3, thinking I’d just swap out a motor from one of the other slew of 1237-Series CanAm’s after some test laps to find a likely candidate. But the 1247’s handling and performance was spot on, easily making up for anything lacking in the ponies, so the motor swap was easily dismissed for this first test run evening. You can’t beat that with a stick.

 

And that’s it on this front (or affront) for now. Assuming this “1258-1243 median” 1247.2-Cc3 would at least be a decent runner, I have already started building the “1258-1256 median” 1249.2-Cc3. The 1249’s build post should be much shorter and much longer. Consider this a warning. Please stock up on any emergency provisions at this time.

 

Rick / CMF3

[Rick Moore]

1249.2-Cc3

 

The Long, the Short, and the Ugly… This is The Short…

 

As explained in the previous 1247.2-Cc3 build post, the 1249 is the 1258-1256 median diverging main rail w/ iso-guide (DMR/iG) chassis design (as opposed to the single center main rail, or SCMR, cousin designs), finishing out this initial phase in the main rail length study. A repeat from that previous post, the reference list of relative main rail lengths:

 

SCMR    DMR/iG

 1241       1243       (longest)

 1246       1247             ^

 1259       1258             ^

 1248       1249             ^

 1254       1256       (shortest)

 

Rather than bore you further, at least for now, let’s get right into it. The 1249.2-Cc3:

 

 

 

 

 

 

 

And it just wouldn’t be complete without a side-by-side of all five “c” dimensioned DMR/iG chassis. From left to right; the 1256.2-Cc3, 1249.2-Cc3, 1258.2-Cc3, 1247.2-Cc3, and 1243.2-Cc3:

 

 

 

The 1249.2-Cc3 all set up and RTR (light “race” set-up) came off the work bench at 98.6 grams; with Pb 100.0 grams.

 

Test Run:

 

A rare Monday evening at Fast Eddie’s, possible by having this past weekend off from work at the hospital for some much needed R&R, and necessitated by having to negate my anti-social tendencies for holiday obligations to be in the presence (tis the season for giving presence) of others this Wednesday evening thereby missing Test-n-Tune. Besides, I like getting to Ed’s on Mondays to hang out for the races on the Oval, always good fun, whether I get in enough test laps or not.

 

Main comparison for the 1249.2-Cc3 will be with the 1256.2-Cc3 and 1258.2-Cc3, but the 1247.2-Cc3 and 1243.2-Cc3 are in play too as this is just the beginning of testing between all five “c” DMR/iG chassis.

 

Again, as on the 1247, I had some questions as to the pony I’d put in the 1249, and this time it was definitely a step behind the others. A quick motor change, with another I wasn’t so sure about in another car, and bingo. No surprise really, the 1249.2-Cc3 fell right into place with the other “c” DMR/iG chassis. That I can certainly live with. (And then spent as much time playing with a bunch of the JFF cars; pointless, but the smiles and laughs are more than worth it…)

 

Side note: Is it just me, or has anyone else seemed to find having anti-brake on your controller appears to be advantageous with these new CR-102 motors with their much stronger braking? I couldn’t see that it mattered at all with the JK HR’s, but it sure seems to offer a greater range of brake setting for the CR-102’s… Necessary? Probably not. But definitely not a hindrance.

 

And that’s that for The Short.

 

And just the beginning. I’ll need to do quite a bit more “variables” testing of the 1243.2-Cc3, 1247.2-Cc3, 1258.2-Cc3, 1249.2-Cc3, and 1256.2-Cc3, ponies to start with, to sort through their subtle nuances, and try to see what differences this whole main rail length thing has, if any. As for a next build in the 1237-Series, I’m considering building an updated version of the three-and-a-half year old 1256.2-Cc3, with the revisions to the wire layout sequence and spine rails, to eliminate any, again if any, contributions these structural and age factors may be exhibiting in any comparison observations… Subject to change, of course… We’ll see…

 

As for The Long, as well as a matter of needlessly eating up more bandwidth, and boring some into a permanent coma, I’ve already posted a build sequence thread for the 1249.2-Cc3:

 

http://slotblog.net/...build-sequence/

 

As for The Ugly…

 

Rick / CMF3

[Rick Moore]

1256.2-Cc3.v2

 

There was really little question as to what the next build would be… In the last post I had noted the age disparity among the “c” dimensioned diverging main rail / iso-guide (DMR/iG) chassis. Three, the 1243.2-Cc3, 1247.2-Cc3, and 1249.2-Cc3 had been built in the November and December; the next oldest, the 1258.2-Cc3, had been built earlier in 2021, back in the beginning of April. That’s an acceptable time span between chassis. Then there was the 1256.2-Cc3; not only was it the first of all the DMR/iG chassis, it had been built back in May 2018… making it almost five times older than the next oldest 1258.2-Cc3… In fact it is the second oldest active 1237-Series chassis in the CMF3 stable of active cars (just behind the 1254.2-Cc3). And I was aware the 1256.2-Cc3 had a ridiculously greater number of laps on it than the other four…

 

That was just too much of an age difference and a variable I wanted to eliminate to do a study comparing the main rail lengths of these five chassis…

 

So a new build was in order for the 1256.2-Cc3. If I just made another one exactly the same as the first (1256.2-Cc3/2) I wouldn’t even have posted it up here. That would not be the case. For this new 1256.2-Cc3 I would be including a few of the build revisions that have been incorporated since the original. First is the revised wire layout of the buttress rails and side pans; simplified, it used to be buttress then sides, now it is sides then buttress. Second is the revised spine wire layout for the rear motor / drive assembly; previously there was only a V-shaped 0.047” wire atop the medial forward aspect rails; the current layout uses 0.039” wires, with a V-wire atop the lateral forward aspect rails inboard of the buttress articulations, wires atop the lateral forward aspect rails from the buttress articulations to the side pan restrictors, and wires atop the lateral rear axle tube support rails from the buttress articulations to the rear axle tube uprights. And last, and of least consequence, the revision of the rear motor / drive assembly gear guard from medial to lateral on the medial rear axle tube support / motor box rails. Granted, judging from the 1258.2-Cc, all current indications are these revisions make little if any difference in the chassis design’s handling characteristics and performance.

 

But that was enough revision to make this chassis the 1256.2-Cc3.v2:

 

 

 

 

 

 

 

No apologies for the “repetition”. Everyone should be used to this necessary evil at this point in the 1237-Series… “used to it” like going to the dentist to get your teeth drilled over and over again…

 

Off the bench the 1256.2-Cc3.v2 weighed in at 98.6 grams, leaded to 100.0.

 

Test Run:

 

All that mattered was to see if there was any difference between the old 1256.2-Cc3 and the new 1256.2-Cc3.v2. The two motors for these cars I chose had run very even best lap times in the 1258.2-Cc3 and 1249.2-Cc3, so I didn’t think that would be a factor. As well as the original had been performing all this time, my hunch was there would be little if any. At the same time I am still testing/studying all the “c” dimensioned DMR/iG chassis to ascertain the effect of the main rail lengths.

 

You never know what’s going to happen until you put the cars on the track…

 

The new 1256.2-Cc3.v2 ran every bit as good as the original 1256.2-Cc3 had been running over the last three test sessions, the key word being “had”. Maybe the old 1256.2-Cc3 “knew” I’d just built its possible replacement, but more than likely the motor/set-up and track conditions for that chassis just happened to be spot on for last night; in any case the “old” 1256.2-Cc3 turned its best laps ever, and for this session second best of all the DMR/iG chassis just under a hundredth behind the 1243.2-Cc3 which had an absolute rocket of a motor in it…

 

Adding to this confusion, only two other cars ran their best ever laps last night, curiously running in new motors, but even more curiously they were the 1256.2-Cd3 and the 1256.2-Cb3…

 

Three things can be hypothesized (“?”) from this…

 

First: Track conditions were near-perfect for the 1256.2-Cc3, 1256.2-Cd3, and 1256.2-Cb3. Maybe…

 

Second: There were verifiable improvements with the rebuilds of the 1241’s that would indicate the “chassis fatigue” syndrome may be a reality, especially with the 1241.2-Cb3 “test mule” which I’m happy to report is once again performing its job as excellently as ever. Their ages at rebuild replacement for “c”, “d”, and “b” were 4.5, 3.8, and 2.8 years respectively. There appears to be no “chassis fatigue” with the 1256’s, with all three turning their fastest laps at relative ages of 3.7, 3.6, and 2.1 years of age. The next year may tell the tale…

 

Third: This was only the fourth test session comparing the five (now six) “c”-dimensioned DMR/iG chassis, and it is definitely too early to hypothesize anything. At this point I’m still sorting through motors looking for a set of five, oops, I mean six, to run between all six cars. In the meantime, this is getting really interesting…

 

What’s to be the next 1237-Series build, that is very unclear at this point. While the 1258.2-Cc3 has the same wire layout and spine wire as the original 1256.2-Cc3, there is no reason that a revised “v2” new build is in order for it at this time… for now…

 

But there is a lot of testing to be done, that’s for sure… As DZ would say: Test, test, test, and test…

 

Keep your finger on the trigger and your eyes on the car.

 

Rick / CMF3

 

[Rick Moore]

1271.2-Cc3

 

Thrills and chills for all. Step right this way…

 

Finally getting around to the first of the “c” dimensioned back-track builds in the 1270 Sub-Series.

 

As a refresher, the 1270 Sub-series designs started with another redesign of the rear “motor/drive” assembly to give a desired overall symmetry I wanted for this sub-series design, giving less lateral mass while extending the center forward; this motor/drive assembly resulted in an increased length to the buttress rails and, to a lesser extent, the “side pan” assemblies.

 

First up will be the 1271.2-Cc3. This got the go-ahead because the 1271 is the 1270 Sub-series design most similar to the 1243 / 1247 / 1258 / 1249 / 1256 diverging main rail with iso-guide mount (DMR/iG) chassis I’ve been concentrating on of late.

 

While the 1271 looks like a DMR/iG, it is not, as the design of the motor / drive assembly and the main rails for the 1271 (also the 1273 and 1275) are such that these component structures are not as clearly differentiated structurally and functionally as with the DMR/iG designs and other 1237-Series designs; on the 1270 Sub-series the same rail assemblies act as the medial forward rails of the motor / drive assembly and the rear converging main rails (rearward of the point of convergence, POC). The diverging main rails forward of the POC running to the front spanner assembly are at congruent angles with those converging rails of the motor / drive / main rail assembly, making the main rails a true “X”. As such, the 1271, 1273, and 1275 chassis are what I call the “X-Rails”, the official CMF3 convoluted moniker being “X-main rail with iso-guide mount” or XMR/iG chassis. And you thought the numbers were confusing...

 

For a visual presentation of that confusion in the previous paragraph, two main frame pics for comparison of a DMR/iG and a XMR/iG chassis:

 

1249.2-Cc3 - DMR/iG main frame:

 

 

 

1271.2-Cc – XMR/iG main frame:

 

 

 

Looks a lot different to me, but...

 

Anyway, the 1271.2-Cc3:

 

 

 

 

 

 

 

 

Sorry, no refunds…

 

Of pointless note, the 1271.2-Cc3 is the 50^th CanAm class design/build in the 1237 Series progression...

 

Off the slab RTR mass was 100.0 grams; I’ll worry about adding any dumb plumbum if and when the 1271.2-Cc goes into race configuration.

 

By static appearances it looks like the XMR/iG 1271.2-Cc3 has “shorter” main rails than the shortest DMR/iG, the 1256.2-Cc3; however, dynamic examination of the X-rail versus the DMR shows this to be somewhat misleading, as the 1271 doesn’t “behave” like a shorter 1256. So I really have no idea where in the realm of chassis characteristics the XMR/iG 1271 might fall in the relation to the DMR/iG chassis, or even if in fact it is a completely different kettle of fish… One way to find out…

 

Test time:

 

Comparison is of course versus the “c” DMR/iG chassis, the 1243.2-Cc3, 1247.2-Cc3, 1258.2-Cc3, 1249.2-Cc3, and 1256.2-Cc3/v2. (Of note, any comparison at this time of this 1271 or any subsequent new builds of “c” dimensioned 1270 Sub-series chassis with the previously built “b” dimensioned frames is largely inconsequential, the goal being to establish a more empirical baseline with the “c” frames first.)

 

Two years ago I would have considered last night’s first test runs “successful”, but that’s relative, so instead I’ll qualify it by using the term “interesting”. The XMR/iG 1271.2-Cc3 is definitely a different kettle of fish compared to the DMR/iG chassis. Not surprisingly it exhibits some of the characteristics of the single center main rail (SCMR) 1254.2-Cc3 and the shorter dimensioned (RAx-GPC / WB) DMR/iG 1256.2-Cb3 chassis, both of which are still active (the 1254.2-Cc3 the oldest active car in the stable at about 4.5 years), so testing will continue. It will definitely be beneficial to reactivate the 1271.2-Cb3 at this point. I also thought the motor I chose for the 1271.2-Cc3 seemed a bit “torquey but flat” this time out, but, with all the other set-up tests, I didn’t have enough time to swap it out. In any case, testing of the 1271.2-Cc3 will definitely continue.

 

DMR/iG chassis comparisons, update:

 

This aspect of testing and observation is defying any possible theorizing so far, adding more hypotheses if nothing else. As far as the different main rail lengths while the data is curiously interesting it is also thus far inconclusive. One main culprit in all this is the 1256.2-Cc3, the original DMR/iG 1237-Series chassis built over four years ago and continuing to perform in testing (and racing) better than ever. The 1256.2-Cc3 has skewed all data for the chassis age / “chassis fatigue” factor as well. Sure, some chassis need a run-in period, but four years seems a bit much, especially when considering the number of laps, testing and racing, the 1256.2-Cc3 has on it, a conservative estimate is well over 4000 at this point (with some major crashes along the way). Other 1237-Series chassis have shown the exact opposite trend adding to the confusion. The 1256.2-Cc3 could be an outlier (freak) in this regard, one of those weird “slot car things”. But if not it bodes well for the other DMR/iG chassis. Time will tell...

 

Thank you for attending the freak show. Please follow the exit signs…

 

Rick / CMF3

 

[Rick Moore]

1243.2-D3

 

Remember Stock Car chassis? Obviously I didn’t...

 

The last Stock Car class 1237-Series chassis I built was the 1259.23-D3o three years ago back in July of 2019. And I honestly haven’t done anything with them for the past two years. So...

 

The CanAm class diverging main rail / iso-guide (DMR/iG) chassis got me wondering what a Stock Car class DMR/iG might be like. All the previous 1237-Series Stock Car chassis were single center main rail frames (SCMR). It was time to try one, but there were a couple ways I could proceed in this regard and had to consider.

 

First was the fact all five previous 1237-Series Stock Car class chassis were left turn only (LTO) oval track cars. I’ve wanted to build a 1237-Series road course Stock Car since way back when, and decided when was finally now.

 

This meant for this build the front axle rails (FAR’s) would be the same on both sides (12XX.2-D3), as opposed to having different FAR’s on each side (1254.23-D3o, 1259.23-D3o, or the 1244-D3o which in subsequently revised ID is really a 1241.23-D3o). On the LTO cars I’d been using FAR springs of 4x 0.024” wire on the left and 3x 0.032” wire on the right, but for this chassis I would make two sets of 4x 0.024” and 3x 0.032” each.

 

The so-called pans on the previous LTO’s were loaded to the left side, but for this road course frame would be the same both sides; I say “so-called” since they are wire framed 0.010” brass sheet pans, as such not adding much mass to the chassis, and are there to have somewhere to put lead to get the chassis up to the 120-g class minimum mass and as a tuning option. With any luck lead tuning might be accomplished for both road course and oval tracks with the symmetrical pan layout.

 

Next was which DMR/iG chassis design to use for this. I opted to throw caution to the wind, deciding to use the 1243 design which would have the longest diverging main rails, something that on a Stock Car class chassis gave me hesitation, but figured whether it worked or not I’d probably wind up building the shorter main rail DMR/iG chassis at some point anyway. As it turns out the 1237 Series Stock Car designs have a longer rear motor / drive assembly than the CanAm chassis, effectually making the diverging main rails on the 1243.2-D3 Stock Car chassis about the same length as the 1243.2-Cc3 CanAm chassis.

 

I know... shut up and just post the damn pictures...

 

The CMF 1243.2-D3:

 

The completed chassis frame:

 

 

 

The completed chassis:

 

 

 

For the 0.010” brass sheet pans, besides the usual two rear static pans forward of the rear wheel wells and the two 0.024” wire framed dynamic (slider/rattler) pans flanking the main rails, five more smaller static pans were added to the 1243.2-D3, three in the forward-center of the rear motor / drive assembly, and one for each of the two side pans. I made lexan templates of the usable space on the pans, then cut 0.040”-ish thick lead sheet to those full-size shapes for reference, balancing for the opposite sides, and giving a total of 18.25 grams. Seemed like a good range to work with, and I figured I could always cut some thicker 0.080”-ish lead if I needed more. (I always top my lead with blue tape to make it easier to mark for cutting.)

 

 

 

The usual roller pics:

 

 

 

 

 

 

I painted up three of the Charger bodies for this car, a Red Fox, a Kelly, and an old Parma, for no really good reason whatsoever, except that in my new retirement mode I can happily spend the vast majority of my time doing whatever the hell I feel like, in this case needlessly painting three bodies for one car on the vague reasoning I’d be doing some sort of comparison, when in actuality I just had all three and felt like doing it. (And, yes, if I’d had the Mid-America and Ralph Thorne Chargers there would be five bodies for this car... still a possibility too...)

 

 

 

Painted and trimmed, all three bodies came out to within 1.00 gram of each other, the short rear-end Kelly being the lightest, so I used that one to set up the RTR car. I assumed all along this was going to be a lightweight, my guess being on the low side of the 115 - 120 gram range...

 

Not even close...

 

It came out to 112.83 grams. This makes the 1243.2-D3 the lightest, by far, stock car chassis I’ve built, despite starting with the heavier CR-102 motor and a weighted guide, and being that far under the 120-gram minimum was something I was not particularly overly thrilled about. So I had to come up with over 7 grams of the previously noted 18.25 grams of lead, quite a large chunk, just to get this thing to 120. Oh boy. Anyway, some calculations later I came up with this array of lead for the pans that kept the original chassis balance and got it to the 120 gram minimum...

 

 

 

...just barely...

 

 

 

I figure as soon as the braids begin to wear it’ll be back below 120 grams.

 

I considered trying this thing out in its off-the-work-bench ridiculously low <113-gram weight without any added lead just to see if it would even get around the track, but, since it is supposed to be a class racer, threw that idea out the window for now.

 

Speaking of getting it around the track...

 

Test time:

 

I had very low expectations...

 

Jeff Bonanno happened to be at Fast Eddie’s last night (the Southern Retro Rumble is less than two weeks away, September 24 - 25, so this was not a surprise), and he is a lot better driver than myself, and has vastly more experience hauling these retro stockers around a road course track as well, so I had a willing test driver; Jeff has been after me for a couple years to build a 1237-Series retro Stock Car for road course tracks, so he was as curious about this thing as me. Cool!

 

First laps by myself were predictably tenuous, turn entry and exit iffy at best, but this seemed to be more tires than anything else. First thing I did was change the 4x 0.024” spring wires to the 3x 0.032”, and that helped. Changed the gear ratio and that was a major improvement. I started adding lead to the center dynamic pans and that calmed it down to run more consistent and predictable laps. Then I tried different tires, finally using big hub treated, and things started looking a lot better, getting Jeff to try it at this point (he was easily a tenth per lap faster than me). We tried the different bodies, the Red Fox performing best, the Parma surprisingly almost its equal, and the Kelly just a little less drivable up the donut. Added the lead to the side pans, bringing the total mass up to 127.78 grams, and it was better still. Finally Jeff gave me some soft wonder tires to try, and they seemed to be the ticket, Jeff turning fast lap about a tenth slower than his best lap ever on the Hillclimb with a retro stocker. Not bad at all. Even I could drive it.

 

Well, that was fun. Big shout out to my test driver; thanks Jeff! This car ran far better than I could have imagined, especially for a road course stocker at a relatively low weight. There needs to be much more testing of the added lead for total mass in relation to weight distribution, but at only about 128 grams there is a lot of room to work in this regard. And finding the right set of tires will most definitely be critical for this thing. Low expectations have turned into some serious curiosity.

 

Cool beans!

 

Rick / CMF3

[Eddie Fleming]

Beautiful build and cool report as usual.