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Bulletproofing the Cheetah 7 for a 220' Engleman


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#1 gotboostedvr6

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Posted 03 August 2011 - 09:26 PM

I raced slotcars from 1997 till Speedzone raceway called it quits in 2005. Recently i was reintroduced by chance at a birthday bbq by a long time friend Mike Spisak jr.

I am running both the Monday night class at speedzonenj on a 220 foot Engleman and the friday night class at Doms Raceway on a 150 foot hill climb without the crossovers so it is very fast too. Competitive lap times on the engleman are between 5.1 and 5.3 seconds, some A main guys can reach into the 4.9 second range. The A main guys that are competitive all run .025 Cheeta 7's with a few pushing the .030 Cheeta 7 and even the cheeta 21. I plan on sticking with Cheeta 7's for a good long while as i now have a fleet of them including a few NOS 025's.

Competitive lap times on the hill climb are in the 4.2 - 4.4 second range with most guys running the Cheeta 7.

I'm looking for help with where to add bracing to these chassis to deter bent frames and possibly improve/increase pan movement to improve handling.

Keep in mind we are running American 16d's and high downforce bodys.

Rules for the class regarding chassis at speedzone:

Chassis may be braced with no more than 3" of up to .062" diameter piano wire.;
MAY ADD GUIDE TONGUE REINFORCEMENT;
TAPE MAY BE APPLIED;
LEAD WIRE RETAINER MAY BE USED.
PIN TUBES MAY BE ADDED IN THE ORIG. BODY MOUNTING HOLES (CAN BE FLOATING OR FIXED TO THE CHASSIS)
Rear axle vertical location may be changed

Each track will have its own car as the straights and braid depth are very different.
Any tips are appreciated :)

-Dave
David Parrotta




#2 Prof. Fate

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Posted 04 August 2011 - 11:05 AM

Hi

The important brace in my never humble opinion is an "L" brace from the motor to the bushing on the side AWAY from the gear. This is because with use, the chassis will start to "chatter" coming out of corners without it. similarly, with the 7, check to make sure the motor is well soldered into the frame. The common failure is a hit taking the motor out of the car.

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#3 gotboostedvr6

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Posted 15 August 2011 - 08:55 AM

Fate,

Thanks for your reply. I took your advice about reinforcing the rear of the chassis, also added braces to the wings and picked up a rear upright brace and rerouted the power wires to look like this: (pic borrowed from different thread)

Posted Image

I also went with 5 degree pinon and 14 degree spur to help with the angles.

Just need to get the new body painted up einforced and mounted
David Parrotta

#4 gotboostedvr6

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Posted 15 August 2011 - 09:26 AM

I have been averaging in the 5.4 to 5.5 second range during the race with the occasional 5.3 lap. I use retail bought treated tires but plan on switching over to donots to help offset costs and to make it affordable to run the smallest tire possible to tech. Not sure if the donots being untreated will help our hurt my times, only time will tell.
David Parrotta

#5 Randy Tragni

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Posted 15 August 2011 - 09:45 AM

I use to race a 220 foot Engleman here in San Jose with the C7 chassis. Assuming we are talking about the 4 inch chassis, this is what worked for me was (in order of importance):

Bluepprint the chassis (they are usually straight except for the side pan adjustment).
Gear mesh (a must).
Rear upright brace (a must).
Bite bar (try some different thicknesses and see which hooks the car up better).

Other things to try:
Reverse the pans and eliminate the front wheels.
Aluminum side pans Can help get you a little more speed.



If you can run the C11 instead go for it. It's much faster.


Good luck,

Randy.

#6 gotboostedvr6

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Posted 15 August 2011 - 11:40 PM

Randy,

Thanks for the reply. I plan on flipping the pans on a practice car and running some laps soon. I have only run .047 wire but will play with some different sizes.


This thread may very well turn into a weekly log of sorts to track my progress.

We raced tonight, while i placed 5th in the c main i was able to run consistent 5.2-5.3's In almost every lane with a best lap of 5.10
I only placed 5th due to a jumpy finger. The car is capable of winning b main, i just need additional track time to get it under control. Over all it felt alot faster and really turned well. It looks like some good headway is being made.


Some things i changed this time around;

1) I'm running angled gears with a Smooooth mesh.
2) I ran virgin 765 treated tires PN/JK8761PT (these tires are very large and caused the car to ride high)
3) I used a diamond brush radius tool to prep the Golddust brushes for breakin.
4) Ran a 42 degree Pro Slot arm in a factory "Blue printed" proslot can
5) broke the motor in for 1.2 hours at 3 volts
6) Had Jay at speedzone balance the arm and cut the comm
7) Made sure the chassis was 100% straight after i soldered the motor in
8) i lowered the body a bit

Very happy so far

-Dave
David Parrotta

#7 W. J. Dougherty

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Posted 16 August 2011 - 09:10 AM

I used to run the C7 chassis when it was the hot lick. I raced on a 180' Engelman in Manchester NH. I don't remember using .047 wire but did use .055 for the bit bar.

What are you tire clearance rules- 1/16"? We ran JK Treated at Speedzone for the Retro Enduro and had no real trouble with tire wear on that track. Unless you're on a tire budget, grind them down until you barely make tech. You will find that the chassis handles soo much better. You can also try larger hubs which will decrease the rolling resistance of the car.

If your car is geared for the taller tires, you may have to take the pinion up a tooth to keep the ratio the same (i.e.- 8 @ .750; 9 @ .720).

What body are you running? A good rule of thumb is to cut it no higher than 1 5/8ths above the track block. Also, push the body as far back as possible.

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Yortuk & Georg Festrunk

#8 gotboostedvr6

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Posted 16 August 2011 - 06:54 PM

Tech is .047
this past race I used .765 tires and the same ratio most others used. My car appeared to be the fastest in my heat (based on my eyeball radar gun) and fastest lap times. It was not so productive in the turns.
I plan on running much smaller tires next time around to fix the turning but would like to retain my straighaway speed. Ill have to drop a few teeth on the spur gear, just not sure how many.

What effect on turning does flipping the pans have on exit speed, turn in speed, and stability?
David Parrotta

#9 Guy Spaulding

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Posted 16 August 2011 - 08:41 PM

I offer these braces on ebay. They're custom made, with different sizes for the Turboflex, C7, or C11 series. They're available in .047" and .055.

They help protect your rear uprights, stiffen the rear of the chassis, brace the motor, and protect the spur. - A lot from one little piece of wire!

BothBraces.JPG

#10 W. J. Dougherty

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Posted 16 August 2011 - 10:03 PM

It definitely aids in stability by placing more of the weight of the car towards the front. It should keep the nose of the car better planted. Like I mentioned before it is easier to change the pinion up 1 tooth than to try to adjust with the spur gear. What gear ratio and what body are you using??
Yortuk & Georg Festrunk

#11 gotboostedvr6

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Posted 17 August 2011 - 10:56 AM

Guy,

I caught that brace on ebay, do you sell them to raceways?

Wj,

Body is a O/S Mercedes, 12/37 765 tires, the rear is braced with a commercially available spring steel unit..

one tooth up on pinion brings the ratio from 3.0 to 2.8... a bit too low imo. Plus my brakes are bad now and would only get worse.
David Parrotta

#12 W. J. Dougherty

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Posted 17 August 2011 - 12:58 PM

I am very familiar with the OS Mercedes. I now run the Parma Storm, but may switch to the Redfox Starfighter.

I only suggested to change the pinion if you decide to cut your tires lower, like to .740 or smaller. How does the car run with a 38 or 39?

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#13 Bill from NH

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Posted 17 August 2011 - 01:46 PM

The Mercedes in the first photo looks like a Jim Stinnet paint job. :)
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#14 W. J. Dougherty

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Posted 17 August 2011 - 02:08 PM

Good eye Bill!! He painted that for me for the ROC. Between that one and the one below, I won like 4 concours awards over 2-3 years...

Jim has aways done a great job for me...

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#15 gotboostedvr6

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Posted 17 August 2011 - 02:09 PM

This motor has been around. It started life on a 10 year old Champion geared 10 35. It was heavy @ 138 grams and ran around the 5.47- 5.65 range.

The motor then went into a JK C-7 with the stock axle and front tires that touched the track. Ratio was changed to 11 37 It ran a more consistent 5.4 but after the first wreak it slowed a bit due to front axle damage.

I then fixed the axle to the chassis and bent the tires up and went with a 12 38, in testing i found that the motor got very hot but laps were 5.3-5.45.

I then retarded the timing as far as the can would allow and changed the ratio to 12x37 but found that i had to run med heavy springs to get good speed. It was then recommended to me to have the arm redone

I had the mags zapped, arm turned and balanced, bought a brush radius tool to get the brushes right, broke the motor in at 3.3 volts for over an hour. Lastly i was careful not to get too much heat into it when mounting. The 12x37 angled gears also likely helped to get rid of some drive train drag.

Heading to the track now with a new O/S MB body mounted with light paint ;) and slightly smaller tires. If i have time ill throw in a 36 then a 38 tooth gear to see how if effects times.

-Dave
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#16 Randy Tragni

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Posted 17 August 2011 - 08:29 PM

track_big.jpg Dave,

Try 13/37 gears (angled). Use JK untreated, big hubs. I was running Nascar with this chassis and used the OS Malibu with boxed spoiler. When running the Cheetah X25 (same track) I ran the OS Mercedes.

Good luck. Have fun.
Here's picture of our old track (Gosh, I miss it!)

Randy

#17 Guy Spaulding

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Posted 17 August 2011 - 09:59 PM

[quote name='gotboostedvr6' timestamp='1313596614' post='358341']
Guy,

I caught that brace on ebay, do you sell them to raceways?

I've decided to entertain one request for a bulk purchase. Yes, raceways are encouraged to PM me. We'll see how it goes. The brace is not legal under National, or Mid-South rules, so it does not pose a conflict of interest to offer them to others. :)

#18 gotboostedvr6

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Posted 17 August 2011 - 10:30 PM

Well some news.. I remounted a new O/S MB body a bit lower and ran my first 5.0 lap, alot of them actually. The shop manager ran a few 4.9 laps with it and im confident it can be reproduced.
Same setup as before otherwise. Next quest is 4.9's :D
David Parrotta

#19 gotboostedvr6

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Posted 07 September 2011 - 11:57 PM

Randy,

What lap times were you guys running x25 and gtp body with the 13/37 gearing?

-Dave
David Parrotta

#20 JerseyJohn

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Posted 08 September 2011 - 07:09 AM

Well some news.. I remounted a new O/S MB body a bit lower and ran my first 5.0 lap, alot of them actually. The shop manager ran a few 4.9 laps with it and im confident it can be reproduced.
Same setup as before otherwise. Next quest is 4.9's :D

Dave did you mount the body pushed forward or back ?

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#21 Mike Mankin

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Posted 08 September 2011 - 05:57 PM

Here Dave i will give you the setup that i have used to win a few races there for the Cheetah 7

-38 degree Pro Slot Arm In Speed FX Can
-12/37 angled gears Set motor back as far as possible.
-.047 bite bar
-do not reverse pans
-Big Hub plastic if you want part number i use 8763pt they were once my retro tires that i cut down and run This track likes treated nothing else untreated bogs the car down run your tires around .750 will get couple races out of it
-Brace the guide tongue with one bent .062 wire bent and then the Slick 7 Guide brace
-Use Champion bushings the flat ones Jig at .765
-Use OS Caddy .007 body
that is the basic setup what i have used to win in the A Main with that car if you do all that correct and get a decent arm you are good for 4.8-5.1 on any night. and not always the speed stay on and you will win if you average a 5.3 on every lane you will get 181+ laps which is enough to win in the A Main some nights
PS all this info is available to those who ask at Speed Zone if you go up to any of the A Main people right after they will tell you what you need to do to your car to win
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#22 gotboostedvr6

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Posted 09 September 2011 - 05:00 PM

Thanks Mike for the info

John,

Right now the body is pushed back so the guide almost touches the front of the O/S benz. I will however be changing that soon.


-Dave
David Parrotta

#23 Bobby Dalton

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Posted 22 October 2020 - 01:40 PM

I have the track from San Jose, the one pictured in Randy's photo.  It is for sale if anyone is interested

 


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