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Chassis development (one thing leads to another)


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#1 JimF

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Posted 10 January 2014 - 03:00 PM

Here are some of the cars I posted about in the "Tuning for SCR" thread. These are the cars referenced in the other thread but I decided to take a little different tack in the description so I started this new thread. This will show (in a "cliff notes" version) how these cars were set up, but also, sort of how they came about.

 

Here is the starting point for this story. This is a single .078 straight rail frame that is a standby. This frame always works on every track we run, is easy to build, and is nearly bulletproof. Also, no expensive kit parts are used except the JK bracket. All brass is .064. This car comes in at about 115 gr. all up. This frame works with just about any tire/body combination and is the easiest to tune of all.

 

 

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This is a newish version (6 months) of the single .078 old reliable with the addition of 'loops' in the main rails. This one was built from a JK kit and the major difference is a little more flex and a little lighter in weight. This frame is also very tolerant of tires and it, and it's brother below are the only cars I had at SCR yesterday that could run untreated tires. This car goes about 109 gr, but needed the little 2 gr. squares of lead at the rear of the pans. All up @ 113.5

 

 

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So.......straight rail became Looper1 which then became Looper2 with a little different weight distribution. The nosepiece was notched and a couple of little bits of brass added to the rear of the loops. This one is also slightly longer in overall wb/gl but basically the same as the one above. This was the car that I chose to run @ "the Cave" last month. At SCR yesterday, this car was best just as shown here. The tires are JK untreated but slightly narrowed and running weight is 112 with a bit of lead that I ran at the Cave. I'll probably take that off so this will probably run @ 109gr. Both Loopers like the O/S Lola T-160L.

 

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I built this about 8 months ago as an alternative to the single .078 frames and this is the frame that Gene Braham ran to whip us all the last time out @ Motown. This is 5 X .047 and all brass is .062. This frame has a fair bit more twist flex than the single .078 and has more bite. The single 'bite bar' is .032 and is not soldered to the rails. The up stops look like outriggers and are set to allow about. .005 free movement. When the .032 spreader rail hits the up stop, there is a bit of spring in the wire so it is not a hard stop. I really like this feature but I think it needs some reinforcement. This frame is always fast but needs more tuning than the singles. This was the fastest car @ SCR yesterday with a TSR @ 9-29. This car was running a Parma Lola T-163, JK treated and narrowed, and a running weight of 112 gr.

 

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So......that ^^^ car became this car when about 3 months ago, somebody asked me to build them a lightweight to run in SoCal. I made up the nosepiece out of .032 and then the guy decided not to go, so this sat around in the "to do" pile. I recently got around to finishing it and basically grafted the frame above to the light nose with 4X .047 instead of 5X .047. This car came out @ 98.5 gr all up and with the increased flex of the four small rails, was definitely too bitey for SCR as it was. This car was ballistic fast in a straight line and also in the wide radius turns but it was way too tippy in the tighter turns. Although I got a few faster laps than the car above, it would not be good to race as it stood.

 

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Here are the changes that I made last night. Added a 3.2 gr block of brass to each pan about 2/3 of the way to the rear. These can easily be unsolded and moved fore and aft. I also added about 2 gr of lead under the front axle, and changed out the tires to Koford Wonder softs. I had a TI-22 on this car and may switch out to a Lola. Running weight is now 107gr. If I had to guess, I'll bet that I eventually add another frame rail to this making it a 5 rail (western count).

 

 

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So, the 5X .047 Can Am combined with the nosepiece of the 4 rail........became this car........a new pro coupe. My old warrior pro coupe has raced probably over 20 races and usually won. Lat time out however, it was soundly beaten and aside from a freshened up motor, I decided to build a new one. I've built several Pro Coupes in the last 3 years that all worked but never built one that could beat the old one.....(no idea why).

 

This uses a cut up JK nosepiece and a Warmack AW bracket. This is 5X .047 with .064 pans and weight blocks for a running weight of 104.5 all up. The big dog motor is geared @ 8-40, the tires are Alpha treated and slightly narrowed and body tested was a Parma Lola T-70. This car was absolutely great and with no tuning at all this ran as fast or faster than my old car ever did. This won't get any changes at all until I try it @ Motown where our next coupe race will be.

 

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Finally, the single rail .078 and the loop rail .078 Can Ams led to this car........a 4.5" stock car. Also built with a JK kit and an R-Geo bracket, this car came in @ 103 gr w/out body or 112 all up. I knew this was way too light for these cars but wanted to try it as is. Surprisingly, this was pretty good as shown and ran competitive times with a Parma Cyclone body. My R-Geo warrior frame was running through the corners better than this so I have that to fall back on. I'll add about 4 gr to each pan about 2/3 of the way back and possibly some lead under the axle as well. I may also test a '68 Charger on this car as that body is sometimes easier to drive.

 

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OK......so......not exactly "six degrees of Kevin Bacon" but you can see how each frame concept tends to lead to something else and also how things can come almost full circle.

 

Off to the races.


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Jim Fowler




#2 Pappy

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Posted 10 January 2014 - 04:05 PM

Those chassis are beautiful. Hope the bodies look that good.


Jim "Butch" Dunaway
 
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#3 TG Racing

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Posted 10 January 2014 - 04:40 PM

I like how you run your leadwires. So simple!


Thom Greene

#4 JimF

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Posted 10 January 2014 - 04:44 PM

Those chassis are beautiful. Hope the bodies look that good.

 

Ummmmm... welll... uhhhhh...   :rolleyes:


Jim Fowler

#5 JimF

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Posted 10 January 2014 - 05:08 PM

I like how you run your leadwires. So simple!

 

Thanks, and yes it IS simple but with a couple of cautions. This system usually works best with medium stiff lead wires such as the pink Alpha stuff. With the really flexible wire like the 20 ga S-7, it can sometimes manage to drop through the rails and drag. If you look at pic #3 you can just make out a "floor" of .007 lexan that is super glued to the main rails in order to keep the wires from dropping through.

 

Lead wires are SUCH a PITA sometimes.


Jim Fowler

#6 Pappy

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Posted 10 January 2014 - 05:48 PM

 

Ummmmm... welll... uhhhhh...   :rolleyes:

The body in the first picture looks pretty good. I've got a feeling they are all way better than average.

 

I quit running the Ohio Valley Retro series for a number of reason's. One of them was how bad the bodies looked. I just couldn't stand passing them through tech anymore. One guy had a driver that was painted all white with a red dot on the top of his head because the rules stated the driver only had to be two colors. A lot of guys can't even bother to paint the exhaust pipes. That is not what Retro was all about to me. Retro is about the cars looking like cars. But that's just me.

 

Great job Jim, you should be proud of those cars and I know you are or you wouldn't have posted them here.


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Jim "Butch" Dunaway
 
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#7 JimF

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Posted 10 April 2014 - 02:12 PM

Here are some developmental steps regarding a couple of tuning fork cars pictured in the "GVP" thread. The cars pictured below were just tested on the King Track at Eddies Slot Car World in Vallejo. This is our next stop on the Nor Cal Retro circuit. This is what passes for a fast King track (relative only to Nor Cal) But it is old and has issues with braid etc and has a heavy rubber build up. Eddie keeps the bite up so we never have traction issues here but it is tough to get a car perfect b/c of variations and all the old rubber.

 

  • This is a fixed fork car with .062 forks soldered solid at front and with a limiter at the crux of the forks.
  • Main rails are single .062/side.
  • This is a light car for Nor Cal @ 97 gr but it is surprisingly good.
  • After tuning bodies and tires, this car is not tippy but it is jumpy.
  • On the rough conditions at Eddies, I think it's just too light, and maybe a little short @ 4.950 overall.
  • The two brass weights are 2.5 gr ea.

 

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  • The weights will be tried both inboard (red arrows) and outboard (blue)
  • Nothing I can do about the short part but this will in turn lead to my next build.

 

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  • This is a GVP "heavy" @ 107.5 gr and a flex limiter at the crux (blue). This was built up from an R-Geo kit.
  • This car is good the way it is but has a cornering limit a little lower than the lighter car above.
  • Even after tire tuning etc, this car feels great to certain point then just "lets go" whereas the fixed forker doesn't do that.
  • So.....the fixed fork car had led me to try and tighten the front forks on this car (red)
  • But! I don't want to solder up the front tubes b/c that is irreversible.
  • The device I'll use is right below the front tire and is just a bit of .062 wire soldered into a 3/32 box tube.

 

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  • The front limiter is in place and is soldered between the front fork arms (blue).
  • This will be a limiter in twist between the two front arms. It will get run this way first.
  • If this is not an improvement, I'll just take it off. If it is, then...........
  • I'll solder the forward end of the wire to the top of the front tubes (red) without soldering up the tubes.
  • This will then in effect become a fixed fork car.

 

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Both of these cars show a lot of promise. The combination of ideas from these two will lead to my next build which will be a fixed fork car with an overall length of maybe 5.050 or so and it will be more in the configuration of the top car. The next car will be built light but with provisions for weight experimentation. I may also replace the single .062 main rail with a double .055 OR leave a provision to add the second rail later just to see what happens.

 

One thing leads to another................................


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Jim Fowler

#8 Gator Bob

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Posted 01 May 2014 - 12:54 PM

Beautiful builds Jim!

Outstanding attention to detail and quality of construction.  :good:

 

You found the Fixx  :D


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