3139 replies to this topic

[Duffy]

"Inflection," huh?...Well, if it works...

While I synthesized a couple-three guys into the "pretty smart friend" I faux-quoted up there, most of the concept comes from long conversations with Rocky Russo, our Prof. Fate. He talked about hi-speed films he'd studied back in the day, of slot car chassis in corners & the like, and it's from him that that crucial concept that motion has to cease as the car's sorting itself out actually comes from. (I take credit for the "train" analogy.)

I'm interested by how many guys are trending toward less motion as tracks get smoother. There's a suspicion that we Retro guys sorta picked up at the point we'd left off in the late '60s, copying what we'd done then, but without thinking through what changed in the meantime. I wouldn't know: I wasn't there after '66.

Duf

[slotcarone]

Duff I find that Retro chassis need very little movement or work just fine as a torsion with no ninges at all.

[A. J. Hoyt]

This is a lot of discussion on theory in the scratchbuilt session. Just wanted to acknowledge that so I don't get accused of "hijacking" a thread but it seems relevant to scratchbuilding.

 

I have the opportunity to do "one better" than high speed film (imagine trying to "stage" a "just over the edge" deslot - not a total melt-down brain fart deslot like mine and being ready to film it). I have set up multi-body simulations of slot cars and found that there are just the three types of deslots that I mentioned above - the "pitch-out" (lifts the nose), the "roll-out" (bicycles on the two outside tires) or the "half-spin tug-out" (back end comes around and pulls the guide out).

 

The inflection I speak of is when you go from a straight (infinitely large radius) to a, more-or-less constant radius in an instant (where the turn starts). This is a large lateral impact to the guide, generally bouncing the flag (or pin) back to the inside, to the outside, back to the inside and "damps out" but usually not before 90 degrees of engagement (lots of turns are 180 degrees or more).

 

Then, it is another "inflection", transitioning from hugging the outside radius of the slot to a straight (how many deslots occur on the short section of straight AFTER the turn, sometimes to the outside, sometimes to the INSIDE!) that has to be "handled" by the motions of the chassis. One could actually make a case for a "loose" guide to take some of that motion, though I was always taught to set it as tight as possible to keep it as parallel to the slot as possible, avoiding the "ramp" that could lift the guide out. A little bit of lateral "flex" may do this...

 

Then, there is the "wrap-up" of the chassis rails while the tractive forces of the tires (forward bite in stock car parlance) try to "wheelie" the nose into the air. A properly "damped" set of rails can really settle down some cars while others need that stiffness right at the motor bracket to avoid the wrap-up (and subsequent chattering). I think Dennis Sampson has had this dialed in for decades by soldering on a brass rail along the steel rails to help damp out any resonant frequencies.

 

All for now - have to get back to work.

 

Keep it in the slot (or, let the chassis flex and motions work with you to that end),

 

AJ

[Duffy]

Thanx AJ, good points.

While there has always been a "Scratchbuild Discussion" thread intended for this stuff, it's often difficult to coordinate pics here with talk there and lotsa guys just blithely ignore it & post here. Figuring that since the pony's already out of the corral & there's more room for the plops, I've gone along with that trend.

Duf

[Gator Bob]

Great stuff... while I don't use a slide rule when I build, using the minds eye super-slo-mo...... perceiving the forces and dynamics while the car is on the jig is one of most enjoyable part of slot cars.  

 

Flashback ..... While mounting bodies I use a skill learned in the early 70s  ... seeing colored air coming off the bodies while watching AA/FC cars at the top end   amazing! 

 

Since then it's like having a personal and portable wind tunnel

 

Thanks....

[bbr]

AJ and Duf... this is some really good discussions on chassis dynamics!

[Tim Neja]

Im crazy I know... 

 

Flex Frames #20

 

.078 main rals 

torsion style movement 

 

I know torsion is a little out dated.. but i never built one, and it only took me 45 minutes.. so why not. 

I ran out of pin tubing, so that will be added once i get more. 

 

Don't know why "torsion" would be out of date! It's a great way to go on some flat track!!   Plus my newer King Track Can Ams--are ALL FLEX cars--NO hinges!!! And they work well.  Just ask the Tokyo crew!!

[Jim Lange]

Here's some of my latest creations. Looking forward to trying the .032 car this weekend at the CP cup.

[slotcarone]

 All beautiful chassis Jim!!!  Good Luck Racing!!!

[Greg VanPeenen]

Very nice,

like the 20 rail tripod and the center (in the group picture) retro pro.

Great work. Good racing at the CPC.

Greg VanPeenen

[Tex]

Nice lot of chassis'!

[Duffy]

Second in the "STG" series commercial stocker chassis protos, Duffy 67 "Lester W. Polfus."



Six rails of.055" and amazingly, only one has more than one bend. Brass .050" & guide tongue as well. And so on.



Bottoms're boring.
While this is supposed to be a classic shaker sled, I was forced into tying the rear together with a Duffy Tailgate, & now I'm insisting it's because I'm trying to transfer mass to the rear. That't my story and you're sticking to it. This one masses 83gr. now, targeting 130 all-up.



We decided to let the body have a little shake too. It's a trade-off - you don't want this massy, high-centered bod lifting up and pulling even higher above the CG, but maybe give it a litttle delayed play...so, rear pintubes're very limited shaker-style, two R-Geo 1/16" grommets over the tube, inside a 1/8" square tube.

We'll see. Hope to be turning this loose on the Jersey Devil this Sunday, up against my more-conservative #47 "Gravy" stocker.

Duf

Duf

[Tex]

Good luck, Duffy! Drivin' a stocker on that Jersey Devil looks like it'd be a handful.

[Tim Neja]

GEEZ JIM,  you're a building fool!!! Looking forward to seeing how those babies perform!! NICE!!!

[Jim Lange]

Thanks Tim, wanted to build one more but I'm running out of time and my fingers need to heal. LOL   See you tomarrow

[ejgehrken]

3D Racing Chassis #008

8-Rail GT Coupe Chassis

8 rails of 0.047" wire

4" wheelbase, 0.940" guide lead

1" Hanada Motor Bracket

 

I used this chassis to make my first ever Retro East "A" Main at this past weekend's race at Slots-A-Lot Raceway.

I qualified 7th and finished 6th/29 overall in my first race on the S-A-L King and only my 2nd Retro East Winter Series event.

 

 

 

 

[slotcarone]

Nice job Eric and congrats on making the A main!!!   Glad to see you braced up the bracket!!

[John Streisguth]

I can attest his car was working very well...nice job!

[ejgehrken]

3D Racing Chassis #007

8-Rail Can-Am Chassis

8 rails of 0.047" wire

4" wheelbase, 0.940" guide lead

1" Hanada Motor Bracket

 

This is another chassis that I built using the 8-rail concept. I performed very well in testing on the Hudson Valley Raceway King.

 

 

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[macman]

First completely new build in a while. After see all the multi-rail builds (thanks Preston) I decided to jump on the bandwagon; 4 x .047  solid. Nosepiece & bracket are from a pre-Samurai R-Geo stocker kit. 4.5 wb .75 flag, just the way Rick designed it. Two piece .062 pans; the inner pans can both be removed if necessary for weight reduction, or just the right for oval duty. Solid raised body mounts this time with very little pan movement: will be testing tonight, possibly racing w/ Torino body. I did clean this one up some with a new Dremel wire brush, hope you all are satisfied  .

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[Tex]

Good job, Ben! Let us know how it works!

[Dominator]

It's been a while since I posted a chassis so here is my latest custom fun build. 

 

.063 brass

.078 main rails

JK 3/4" motor bracket

Front axle supports where sacrificed from a FSF motor bracket

Slick 7 guide tongue

Total weight with parts 129 grams

Body was painted by the owner of the car Bob Hughes "The Witch Carver".

[John Streisguth]

Now that's what I call "Heavy Metal" 

[Tex]

That's just too cool! Bravo!

[slotcarone]

A real Lead Sled!!!!