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CMF3 1237-series design and build progression

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#126 Eddie Fleming

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Posted 27 May 2020 - 12:05 PM

Time will tell how well it works but I agree with you the Lotus looks a lot better. The best looking of the Mclaren M7C is the CL. But yes I like the Lotus.


Stay well stay safe and hope to see you in the fall at Fast Eddie's

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Eddie Fleming

#127 crazyphysicsteacher


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Posted 30 May 2020 - 10:26 AM

Rick, I will bet you find moving the pivot point for the triangles backward is a huge improvement to off the corner bite.

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#128 Rick Moore

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Posted 16 June 2020 - 05:06 PM



Another F1 build, as promised, or as threatened, depending on your frame of mind…


Over in the CMF3 JFF scratchbuilding thread there was the A401-01 Lotus 56B build, a cool looking F1 car that has no applicability to organized rules racing. But there were elements of that chassis design that are applicable to the 1237-Series that warranted investigation, in this case the rear motor/drive section. The A227 and A228 designs employ a modified version of that A401 rear motor/drive assembly, mostly changing the A401’s anglewinder drive to the A227/A228 in-line drive. The more notable shared feature, as on the A401, the rear axle tube uprights for the A227/A228 are frame superstructure, a change of the usual rear axle tube uprights which are frame wires with bends to attach to the tube.


For the A227 and A228 the front half of the chassis are, respectively, the “same” as the A219/A225 (with single center main rail) and the A220/A226 (with diverging main rails). And, again and for the same reason noted with the A226 build, I opted to skip the single main railed A227 and move directly to the diverging main railed A228 build.


The A228.2-e3:















First pic shows the completed chassis frame, and that it does not directly carry the rear axle tube.


The sissy bar for the A228 is interchangeable, consisting of two 1/16” tubes attached to the rear axle tube with 0.032” wire; the sissy bars on which the body rests are 0.032” wire (instead of the usual single 0.024” wire) that are inserted into the tubes. A set of sissy bars of differing lengths will allow me use different bodies, such as the Oleg Lotus 63 again, or any of the McLaren M7 bodies.


Some of you, or maybe very few if any, may wonder if there will be a retro F1 version of the A401. Well, it cannot be ruled out. And some new CanAm designs are making it even more probable… We’ll see…


Testing, Update:


I finally got to Fast Eddie’s Raceway a few weeks ago on May 27. DZ was there testing also (a warning to other GRRR racers…), so I tried to stay out of his way (LOL).


I was able to get some first test runs in on the new 1270.2-Cb3 and 1271.2-Cb3 CanAm cars, and some much needed additional test laps on the 1258.5-Cb3. All three showed potential, turning some of the best laps in the CMF3 stable for the evening, with the out-of-the-box 1271.2-Cb3 turning the best gutter lap times on both Red and Black. Not bad.


I only ran a few cursory laps with the A226.2-e3 F1 car, preferring to get this A228.2-e3 finished before doing a more proper shakedown, but it seemed to be fine.


(On an even more pointless note, I ran some of the newer JFF cars for a few quick fun laps. The A401-01 Lotus 56B is a fun little rocket, and looks great zipping around; thinking I might put a little faster pony in it. And the 1405-01 Chaparral 2D may very well have become my new favorite JFF car; it’s a kick to drive and handles surprisingly well, despite the utter mish-mash 1405 chassis; looks pretty cool too.)


Most likely skipping a trip to Fast Eddie’s this week, weighing the known PPE-protected exposure to COVID-19 at work (as the number of patients, and requisite X-ray exams, continue to rise…), and limiting myself going out in the general population with minimal face-mask protection… yeaahhhh… Maybe next week…


“We need to get this man to a hospital right away.”

“What is it, Doctor?”

“It’s a large building full of sick people…”


Stay safe, and have fun, to all you vectors.


Rick / CMF3


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#129 mickey thumbs

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Posted 16 June 2020 - 11:32 PM

And hands off the fomites!

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Mike Vernon

#130 Rick Moore

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Posted 25 July 2020 - 10:53 AM



As warned in the JFF thread, the poop is really going to hit the fan here… and a lot of it… I think we need a bigger fan…


Test runs of the 1270.2-Cb3 and 1271.2-Cb3, though limited, gave the green light for the next design builds in this 1237-Series “1270 sub-set”; in which there are four more designs: the 1272, 1273, 1274, and 1275.


First things first. The 1270, 1271, 1272, 1273, 1274, and 1275 all have the same new rear/drive assembly, along with the basic 1237-Series front spanner and “side pan” assemblies. For the main rails:

1) The 1270, 1272, and 1274 have the single center main rail;

2) The 1271, 1273, and 1275 have the forward diverging main rails, with the “iso-guide” mount in between.


I refer to 1270, 1272, and 1274 as “Inverted-Y Frames”, and the 1271, 1273, and 1275 as “X-Frames”, since that is what the center of the frames look like (viewed front-as-top to rear-as-bottom).


The final differences in these six designs comes with the buttress rails:

3) The 1270 and 1271 have the relatively same buttress rail configuration as all of the 1259-and-earlier chassis.

4) The 1272 and 1273 move the buttress rails to the extreme lateral, just medial of the side pans.

5) The 1274 and 1275 have both sets (four total) of full-lateral and medial buttress rails.


I have had some lingering questions about the location of the buttress rails. The 1270-thru-1275 chassis designs were created in part with the hope of investigating those questions to some extent. Of course, my expectation going in is that I’ll have more questions than answers going out…


The next step in this group of chassis was to move the buttress rails as far lateral as they’d go, right out to the “side pans”, so the next build would be the 1272 or 1273. I had recently built the JFF 1406-01 with full lateral buttress rails to help sort things out (under the Porsche 917K, a narrow frame with short wheelbase and big tires, despite which the 1406-01 runs extremely well). I’ve done enough testing between the 1254 vs 1256, 1259 vs 1258, and even limited test runs on the 1270 vs 1271, to know I have a definite preference for the chassis having the forward diverging main rails with the “iso-guide” mount, so I opted to skip the 1272 and build the 1273, in the current rage “b” dimensions, of course.


The 1273.2-Cb3:













And a pic of the chassis with an unpainted Parma 1050-B Ti-22 Short Narrow-Nose to show how it, my body of preference for these short “b”-dimension frames, mounts up on one:





Obviously, with the buttress rails and FAR’s moved laterally, the dynamic pans (0.024” wire framed 0.010” brass sheet) on the 1273 are significantly larger than on the 1271. This was inherent in the design variation, and had to be considered as such. My thinking (WAG) was they would help mitigate any negative effects of the more lateral placement of the buttress rails… who knows… Besides, since the 1270.2-Cb3 and 1271.2-Cb3 both came off the build block at about 97 grams, there would probably be plenty of wiggle-room in the overall mass for the bigger dynamic pans. The 1273 has 0.032” brass plate for the rear static pans instead of the usual 0.010” brass sheet pans, to offset some of the additional forward mass, and making the buttress rail articulations easier to attach.


However, I’ve not even bothered to get this one RTR yet because…


Testing? Not yet. Besides the pandemic pandemonium, I’m holding off until I get the next one in this series sub-set, the 1275.2-Cb3, completed ASAP… Get the 1273 and 1275 into RTR at the same time… I want to do a proper 3-way analysis of the buttress rail set-ups, and since I only have a limited number of laps on the 1271.2-Cb3, with minimal prior testing to skew the analyzer… which is me… and some say I’ve been skewed for years (still better than being skewered…)… Seemed like a good idea, or a good excuse, whatever… works for me…


Chris/Crazyphysicsteacher had asked in a post after the 1270.2-Cb3 about the medial versus lateral placement of the FAR’s for which I did not have a definitive answer, just an operating WAG. Possibly prophetic on his part, the comparison of the 1271.2-Cb3 and 1273.2-Cb3 (along with the 1275…) with their respective medial and lateral placement of the buttress rails with medially attached FAR’s should add some insight to this question… or maybe not… or add more questions… who knows… also seemed like a good idea…


Keep an eye on that fan…


Rick / CMF3


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#131 Rick Moore

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Posted Yesterday, 10:38 AM



More poop for the fan…


The next build in the 1270 sub-set is the 1275, which, as noted before, I wanted to have completed ASAP to make possible 3-way test runs with the 1271.2-Cb3 and the 1273.2-Cb3. As noted in the 1273’s post, the 1275 has two pair of buttress rails, for a total of four buttress rails, with two on each side, one pair fully lateral adjacent to the side pan rails as on the 1272/1273, and another pair medial running the same as on the 1270/1271 (and the 1259-and-earlier chassis).


Again, I’m skipping the single center main rail 1274 and building the 1275 with forward diverging main rails with “iso-guide” mount.


This “dual buttress rail” configuration produced additional options for the front axle rails (FAR’s), of which three symmetric versions would be given designations (M, L, and D) at this time:

1275.2M: FAR’s attached/medial to the medial buttress rails only;

1275.2L: FAR’s attached/medial to the lateral buttress rails only;

1275.2D: four FAR’s, two per side, attached/medial to both the medial and lateral buttress rails.


I’ll leave out the other possible “alphanumerical” configurations, as well as the asymmetric variations; those three should be enough confusion for now. I opted to go with the “M” configuration on this first 1275 build so it would resemble the 1271.2-Cb3 in this regard, and make comparison between those two more meaningful. Depending on how the 1273.2-Cb3 fits into this mix will contribute to determining when and if the 1275.2L-Cb3 and/or 1275.2D-Cb3 get built…


During the previous 1273.2-Cb3 build I became aware what looked good on paper for the 1275 may not be so good when it came to the build. To assuage any misgivings and possible annoyances, I did a redraft of the 1275 layout, moving the medial side pan rails a little more laterally, narrowing the side pans, but ensuring there would be plenty of room for the pairs of buttress rails, along with any combination of FAR’s, and being able to get all the wires in the rails to go where they were supposed to go during the build... Once I started building the 1275 I’d see if I: 1) had made the right decision; 2) could have left things alone; 3) made it all worse, or: 4) it was all utterly hopeless and an exercise in futility. The joy of scratchbuilding.


As it turns out, the redraft worked. Better to be lucky than good, futility notwithstanding.


Poop/pictures. The 1275.2M-Cb3:













And a side-by-side-by-side of the 1271.2-Cb3 (left), the 1273.2-Cb3 (center), and the 1275.2M-Cb3 (right):





Like the 1273, the 1275 has 0.032” brass plate for the rear static pans, and, again, should help offset some of the additional mass from the additional buttress rails. But, where the 1273 has larger dynamic pans, the 1275 has dynamic pans (0.024” wire framed 0.010” brass sheet) that are the same size as on the 1271.


I put the previous 1273.2-Cb3 and this 1275.2M-Cb3 into RTR trim at the same time. Off the workbench the 1273.2-Cb3, from the previous post, came out to 100.6 grams, and the 1275.2M-Cb3 came out to 101.9 grams. Hunh? About a gram more than I guess-timated for both. In any case, there won’t need to be any lead added to these two just to make the 100g you-know-what…




To say the least, there is still a lot going on in the real world I have to take into consideration and make priorities for, which means test runs are still a wait and see thing, but at least I have these ducks in a row if/when the opportunity to get over to Fast Eddie’s Raceway to get in a few laps presents itself. I’ll update the testing as appropriate…


What’s next?


The 1275.2L-Cb3 and 1275.2D-Cb3 remain possibilities in this portion of the build sequence, but as I noted above they are contingent upon getting in some test laps on the 1271.2-Cb3, 1273.2-Cb3, and the 1275.2M-Cb3. However, I have two more designs on the drafting table, the 1276 and 1277, that are offshoots in the 1237-Series are not reliant upon any additional testing of previous designs / builds, including the 1270 - 1275’s, and are probable candidates for being next. Subject to change. Check your local listings for time and date…


Whole lot of poopin’ goin’ on…


And watch your step.


Rick / CMF3


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#132 old & gray

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Posted Yesterday, 11:33 AM



Given your occupation and the current state of the world I'm happy to see you posting and not mentioning having any health issues.


Keep on building, I'm trying to follow your logic.



Bob Schlain

#133 Rick Moore

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Posted Yesterday, 06:36 PM

Thanks, Bob. Your concern is much appreciated, probably more than you know. It’s been a challenge, and that’s as nice as I can state it… Knock on wood…  :dash2: 


Speaking of a challenge, good luck with that following the logic thing… even insanity has its own warped logic… 


Rick / CMF3


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