# Fray chassis selection



## christopher1968

Looking into "fray" type cars. What chassis works? Are they all new old stock (NOS) or can a Autoworld (AW), Johnny Lightning (JL) chassis be tuned? Thank you for your help.


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## alpink

pespiring minds want to know.


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## Boosted-Z71

A fray build is a process of testing top plates to chassis to determine the pairing that results in the best performance you can get, factors like chassis flatness, axle and armature / gear shaft holes all have to be near perfect alignment. Its really a process of blueprinting all the parts to the absolute best tolerances and fit.

As for building a fray car from a JL or Autoworld, I built 8 "Fray" style cars for some local kids to race from AW cars, I would consider this to be a nightmare if you were trying to build / campaign a fray style race car from these chassis, they are all over the place in regards to tolerances, and the gear sets / axles are awful to say the least.

Once I get the chassis picked out I then move to electricals, then magnets and armature, finally wheels / tires. Again its all a testing process with as many parts and tweak / tune as you go.

There is a nice sticky thread about tuning a t-jet here on HT, written by one of the HT members. This is a great place to start. Building a Fray car for fun is much different than building within all the rules for a competitive legal car. There are builders who swear by certain number plates and chassis, there are numbers that have well known with molding issues. I just start with a given chassis and work through my process, which can easily get into many hours of work before you get good results. 

http://www.hobbytalk.com/bbs1/showthread.php?t=350317

When I started building these cars I bought a test mule from KC-Jets, (Hiram Durant) it was my benchmark for all my work, I had to build a car to out perform the mule, handling and speed.

There also dozens of special tools to do a certain process on a chassis - top plate - armatures etc. 

While these builds are challenging to say the least, its also rewarding to have a t-jet that will fly.

I have about a dozen "Fray" Legal cars built over several years to specific rules, I enjoy them but there no longer daily runners, they have a purpose. What I really like are my Fray look-a-likes / Outlaw fray's that have mean green or custom wound arms and tweaked to no end, these are my favorites to run, screaming fast and handle great and they all have that t-jet fish tail. And I dont shed any tears when I burn these arm's verse the 17 ohm bullets for the real Fray cars, which are getting harder and harder to find good ones..

Boosted


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## alpink

that's what I'm talking about.
I bought one from Hiram too. but just to have one. i rarely race it


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## slotking

I have purchased a few over the years, but found that I could make all of them faster then how I got them.

I also found that my good cars I made are faster than any I have purchased.

As was already said, it about matching parts.

you can take the same chassis number ad gear plate numbers and build say 4 cars. all 4 most likely will run differently.

swap the gear plates around and the car may run faster, slower, or both.


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## Rich Dumas

If you plan on entering formal races you will have to check out the rules, if you are only going to run on an informal basis you can do what you like. Fray and ECHORRS SS cars are nearly the same and you have to use an original Aurora T-Jet chassis with copper electricals to build one of those. A Johnny Lightning/Auto World or Dash chassis could be used to build a Fray style car that would not be legal under Fray or ECHORRs rules. There are some clubs that allow all three types of chassis however.
I have written articles on tuning all three types, there are enough differences between them that trying to cover them all in one article would be confusing.
Aurora T-Jets: https://drive.google.com/file/d/0BzLR42NthGeCaDVSOEhLOVRybkE/view?usp=sharing
Johnny Lightning/Auto World: https://drive.google.com/file/d/0BzLR42NthGeCRzB0RXRwZkxMXzQ/view?usp=sharing
Dash: https://drive.google.com/open?id=0BzLR42NthGeCcTJVMXlfTk1KUjg


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## slotking

some of the videos suck
but you can get an idea of some things

http://www.ho-tips.net/forumdisplay.php?fid=80


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## Boosted-Z71

Rich, Thanks for posting those articles, I knew I had seen something like them somewhere, the JL /AW link goes to a 1/32nd scale page, great write up still useful info, but not directly related to JL/AW

Boosted


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## Rich Dumas

*Wrong Link*

Sorry about that! I corrected the link.
Here it is: https://drive.google.com/file/d/0BzLR42NthGeCRzB0RXRwZkxMXzQ/view?usp=sharing
This is the latest version.


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## slotking

Just completed a video on a very nice tool from RTHO

http://www.ho-tips.net/showthread.php?tid=2162


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## smalltime

christopher1968 said:


> Looking into "fray" type cars. What chassis works? Are they all new old stock (NOS) or can a Autoworld (AW), Johnny Lightning (JL) chassis be tuned? Thank you for your help.


Use original T-Jet chassis to start with. If you build a good one, it will be legal everywhere.

If you look on the bottom of the chassis, next to the crown gear, there is a number. This is the mold cavity number. This differentiates one chassis from another. There are numbers and letter used by the mold makers, you will find that there are certain combinations that are better then others. I prefer solid rivet, #3s or #1s

Some to avoid are #4, Letter G, those are the big ones, there are also certain gearplates to look for. I really like Letter H gearplates, but they all need to be matched to your build chassis.

after you have mastered the T-Jet build, you can move on to the JL or the racemasters, or Dash.
They are much more difficult to get smooth and fast.

Good luck.


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## slotking

just to note
the numbers are not the same between the open rivet and button rivet chassis.

for example
the open rivet chassis is not a good one as stated above, but I have some nice solid rivet #4 cars


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## smalltime

> just to note
> the numbers are not the same between the open rivet and button rivet chassis.


Yes they are.
They didn't have two #4 molds built.



> for example
> the open rivet chassis is not a good one as stated above, but I have some nice solid rivet #4 cars


They might be "nice", but they're not straight.


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## slotking

I have 2 solid rivets
never boiled
and flat Like I like them.

my open rivet chassis are far from being flat.


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## Boosted-Z71

Having seen both good and bad chassis of the same number, I think it came down to the molding processes used over the condition or build of the mold itself. 

From years of experience in a major automotive manufacturer tool room, where we designed, built, repaired and ran thousands of proto-type & production molds it was very easy to change the molding parameters, (heat, fill, pack, hold times, plastic moisture content) and easily cause changes to the part accordingly. While this may not be every case, I am sure its the cause in the majority of variances in chassis. 

For me if you want to build a great chassis you have to blue print everything, I find that the armature hole alignment, cluster gear shaft & Idler post are the most critical to a fast chassis. You also have to take into account your blue printing 2 parts together and the tolerance stack between them, in the short explanation, If the top plate or chassis is out of tolerances on any of the armature / gear train its costing you speed, even before you get started. 

Boosted


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## smalltime

> in the short explanation, If the top plate or chassis is out of tolerances on any of the armature / gear train its costing you speed, even before you get started.


But slotking has two of them that are great.

We're both wrong and we have to live with that.


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## slotking

what I am saying is that I have not seen a good open rivet chassis.
but I have seen good (used) good #4 solid rivet chassis.
I have had some number SR #4 that were slight;y not flat where 1 bigger front tire worked to fix the issue. not the case with the open rivet.
why is that a problem?

What I have always said, is to just test every piece!
I have match parts by the numbers and created a good car, then used the same numbers and the car is not hat great. try a different gear plate and the car wakes up.


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## slotking

> in the short explanation, If the top plate or chassis is out of tolerances on any of the armature / gear train its costing you speed, even before you get started.


so true
I made a little jig to help match them up

no idea where it now


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## slotking

just did a quick video on 3 #4 chassis showing 1 open and 2 solid rivet chassis.
I will post it here soon


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## Boosted-Z71

I find it real easy to determine if a chassis is worthy in 2 checks, put the top plate to the chassis, use a .064 or .065 - 2" long gage pin (just so its snug in the holes) and check the armature hole & cluster gear for perpendicularity and that they are parallel to each other at the tips of the pin, everything else on the chassis can be fixed to some extent. That's not everything but a great starting point. 

This cannot be checked accurately with calipers, you need it setup / jigged on a surface plate and use a .0005 indicator height check setup. 

If a chassis does not make the cut here, it goes into the runner pile.

I have several open rivet cars that are straight, so they do exist, but I will agree that straight closed rivet chassis seem to be easier to find.

The Buick GN I built that won Jim's Drag build off is an open rivet chassis, so you can build a fast car out of an open rivet

Boosted


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## alpink

there seems to be some preference for the "flame thrower" chassis'.
is that because of the extra plate increasing electric flow on each rivet?
or
because it gives the rivet a better grip/bite?
or
other?


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## slotking

you did not hear it from me!!!!!!!!!!!!!!

yes to what you said
but also
you can slide over as well and let the shoe make a little contact as well.
too much and it binds


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## slotking

video

http://www.ho-tips.net/showthread.php?tid=2164


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## Dyno Dom

SK, as usual another good video! :thumbsup:
What size drill blanks do you use for testing and would a different size front tire
help the chassis that's not flat/true???


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## slotking

at min .062 .064 would be best.
the tightest fit is the best.

I have had used one 310 and one 315 - 320 before.
some were good cars!
I prefer even front ends.
Thanks on the compliment


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## rholmesr

A buddy of mine had a super tweaked fray car and needed it for a race in 30 minutes. So I got right to work on getting it to sit on all four wheels. It ended up with a .305 on one front wheel and a .330 on the other. Man, did that look weird. But it actually ran pretty good!

But I agree with the king -- even front ends and flat chassis is a much better way to go.

For checking chassis flatness on a gauge block I usually use .065" (actually 1.65mm) drill blanks that you can get from McMaster Carr. They gotta fit snug in the chassis holes because slop can mask some of the out-of-flatness. 

Ron


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