23 replies to this topic

[Pablo]

.....is there any hard science here, or is it all black art/trial and error ?

Champion TFlex chassis have the clip holes pretty close together and they seem to handle pretty well

Then the JK C11 have their clip holes wide apart.     Looks like most retro F1 guys like their holes with a forward bias......

I'm sure it all depends on the bite bar locations, and design limitations regarding hinge wire placements, the skirts of the body, etc. etc......your opinions, theories, experiences ?  Is there anything inherently wrong with spacing the holes as far apart as possible within reason ?

[Jairus]

I just try to miss the rails and motors with the pin points as that tends to restrict movement.  Beyond that.....???

[Gator Bob]

.....is there any hard science here, or is it all black art/trial and error ?

Champion TFlex chassis have the clip holes pretty close together and they seem to handle pretty well

Then the JK C11 have their clip holes wide apart.     Looks like most retro F1 guys like their holes with a forward bias......

I'm sure it all depends on the bite bar locations, and design limitations regarding hinge wire placements, the skirts of the body, etc. etc......your opinions, theories, experiences ?  Is there anything inherently wrong with spacing the holes as far apart as possible within reason ?

I've had a black art idea rattling around in my head  on this topic ...

 

The only thing I can say right now is ..... much like a pin cushion voodoo doll it will not be within reason.

 

Until then ... about 3/8" from the leading and trailing edge of the pans.

[Bill from NH]

I doubt it really matters. In the old days, it was our practice to lay the pin tubes on the pans up against the .032 hinge piano wire where it crossed the pans. The pin tube/pan joints were stronger when reinforced with .032 piano wire.

 

Regarding flexi clips, just about every JK chassis seemed to require it's own length clip, yet the same clip fit all of Parma's chassis, except womps & the I-32. I don't recall what Champion did with theirs because I never set up the one 4.5" I have.

[SlowBeas]

Pablo,

 

I have no scientific foundation upon which to base my ideas. Mostly, I echo Jarius, with one addition: I've found that pin placement can affect how "well" the body will sit on the chassis. For instance, if the front pin is located too far back on the chassis, the front of the body can droop a little. It makes me wonder if downforce produced during racing would exacerbate the problem even further. The opposite would hold true for the rear downforce. Therefore, I try to mirror the placement of the JK chassis, when possible, by spreading them as far apart as possible.

 

All of the above is pure speculation on my part, of course.

 

Best,

jb

[Don Weaver]

Hell, I'm just lucky to get the holes in the body to line up with the pin tubes wherever they may be!

 

Don Weaver

[Noose]

All I know is I hate them on Formula 1 cars when they are at the back and you have to use teeny tiny ones since a normal one would hit the motor.  Some say having the rear ones that far back helps.  I don't think so.

[Tex]

Hell, I'm just lucky to get the holes in the body to line up with the pin tubes wherever they may be!

 

Don Weaver

 

LOL  I'm in the same boat. I have bigger problems to overcome before critical pinhole placement rises to the top of my priority list.

[old & gray]

When I raced flexy cars I tried a Parma One with a hot wing and put a pin tube in the holes on the hot wing and a pin on the rear body clip mount. I thought it made a differance. When I was at a race I handed it to a Parma factory driver to try as a blind test. His first reaction was "no it isn't your JK, it's not a Champion", then he picked it up loked at it and commented "why don't mine work like that".

 

Pin hole location is more noticeable the more areo you have. Ask the folks running wing cars about moving the pin tubes to tune the chassis.

[Ramcatlarry]

LOGIC says that the farther back on the pan, the greater the EFFECTIVE downforce of the body will be on any given chassis.  Too far forward and the rear of the body will droop - use bullet proofing to stiffen the rear wheel well - and the F-1 car nose.  Spacing them as far apart on the side pan should be the best that it can be.

One reason that I use the body CLIPS instead of pins is that rear short pin always fails for me.  The JK selection of clips will fit many of the existing retro kits...and you can always bend some custom ones.

[Rick Moore]

Pablo, funny you should ask…

 

Back in the mid-late 90’s I built a chassis that had 12 pin mount tubes. Six of the tubes were shakers, and six of the tubes were soldered solid to the chassis. Each location had one of each, shaker and solid; these pairs were located in front of the rear wheel (“rear”), behind the front wheel (“middle”, though this is typically the location of the front pin tube on the vast majority of chassis), and forward of the front wheel (“front”).

 

Back then I was using the chassis with 4” Nascar, 4” Truck and GTP bodies (most of which look little like they do now…), and the front wheel wells were not cut out. I was running it on either a King track or on Phil Neatherly’s short six-lane flat track. I was able to try all variations of using four or six pins…

 

What I found out was the chassis/car always worked best on either track using any body with the “front” and “middle” pin mounts in the solid-mounted tubes and the “rear” in the shaker tubes… Leaving out the middle tube pin altogether was almost as good and seemed to help with adverse track conditions; since the front wheel wells on the bodies were not cut out, this was easy to get away with…

 

So I just got rid of the other six pin tube mounts, and kept it with the solid “front” and “middle”, and the shaker “rear”…

 

As for the “exact” location of the pin tubes, nothing so definitive, because I was too lazy to build a chassis with either a boat load of pin tubes, or movable pin tubes…

 

Generally, depending on chassis design and the body to be used, I typically try to keep the “rear” pin mount as close to the rear wheel well as possible, the “middle” pin mount as close to the back of the front wheel well as possible, and the “front” pin tube at some more esoteric location on the forward chassis that makes the front of the body stable so it can sit as close to the track as possible without dragging on the track. That’s my WAG on the matter…

 

(Cue cheesy horror movie soundtrack music with background screaming…)

 

And that is why I still employ the dreaded “Six Pin Technology” to this day.    

 

(Cue thunderclap… and fade out…)

 

Rick / CMF3

[Gator Bob]

Before there were 'Hot Wings' and I wanted options up to six.

 

 

So I agree with Old&Gray and CMF3 on locations for cars without cut front wheelwells.

 

 

[Tex]

I HATE getting the front of the body ripped back and all crumpled up in a collision. I took a cue from Rick Moore(CMF3) a few years back and for the most part use 6 body pins now. I'll have to reassess my take on solid vs. shaker pin tubes/locations though. Or not.(I'm lazy)

[Dominator]

On most classes you want the nose of the body to have some give to it.  I experimented with this on a Can Am a while ago using 6 pins.  The first two sets on the pans and the 3rd set forward of the front axle.  I quickly found it worked better without the front pins.  The car had more give and made it smoother in the turns. 

 

On my Can Am and Coupe's I place the forward pin 1-7/8" behind the center line of the front axle and the rear pin tube 2-7/32" behind the forward pin tube.  Why

2-7/32" instead of 2-1/4"?  Because that's just the way it ended up and I have copied ever since.  Any area forward of the center line of the wheel well  you want to have flex to have the best handling.  Adding tape/bullet proofing to the underside of the fenders may save your body but you will sacrifice handling.

[MSwiss]

I agree, Dom.

You want the body to give up front.

Just make sure you keep trimming it up until it doesn't drag.

[Gator Bob]

While none of my 'serious cars' have pins up front ... yet... I do agree with Tex.

Then again, I'm one of those crazies that would rather build a motor than paint and mount a body.   

 

Flex? Yup that's for sure....

Can/Am .007/(.003?) Retro^TM  bodies sure have lots of 'give' up front and the sides too ... with the wheelwells cut out to 1/16th from the top of the fender.

 

Winning is that important   .. no tape, no bulletproofing, new body every race.

Hey, It's good for the economy and with 'watercolors' it's not as bad for the environment.

Hope you guys are placing the scrap from cutting 'plastic' in the recycle bin.

[Jay Guard]

Pablo:
I make all of my can am chassis exactly alike, and in this case that is the same as the jk retro chassis kit (which I use often). This way all of my bodies fit all of my chassis which makes checking out which body works best very easy. Of course this works for the f-1 and stock car chassis too.

Another neat trick is to put a small piece of rubber tubing over the the guide stem to support the front of the body.

[Pablo]

Thanks everybody, that gives me plenty to chew on......

Jay, thanks for your method of standardizing the pin hole locations to make quick body changes

F1 and Can Am chassis designs change so fast, and I build so slow, not sure if that will work for me.....

That is the beautiful thing about scratchbuilding, thinking for yourself

[Dominator]

Here is a picture of how I reinforce my bodies with bullet proofing.  What you can't see clearly is the clear packing tape I use to fold over the bottom edge of the body (about the height of the pin hole).  This helps to keep the body from tearing and extend to forward part of the fender.

 

[Pablo]

That's cool, Dominic, but I have no idea what type of car that is......

The pin locations look pretty standard to me, and I see how you stiffened up the sides of the body by extending the bulletproofing upwards.

[Dominator]

The body is a Parma T-70. 

 

The rear bullet proofing is something I used to do when I was racing GT-12/Eurosport classes.  When I first started retro I did not do this until my body got crunched in a race and literally put a bend down one side of the body length wise.  After that I started doing the angle bullet proofing again and no more bending since.  If I was to race it on a flat track I would probably not use this type of set up to allow more flex in the rear.

[Pablo]

I still have no idea what type of car that is......you avoided my question, Dominic.  I could do some quick research and find out what a Parma T-70 body is, but why ?  I appreciate your bulletproofing tips, maybe the newbies can learn, but it adds nothing to the topic.  You can bulletproof a body, thanks.

[Rick]

Pablo, you ask a question that has no definitive answer. Success has been achieved by many in different ways...............

[Pablo]

Thanks, Rick,

I appreciate an opinion like that coming from a successful chassis designer  !!!

Of course I knew there was no hard fast answer.  But I like hearing the theories !

I especially like hearing your reply :  "Success has been achieved by many in different ways..............."

That is an absolute classic for the ages, Rick.

Cheater, when you return from Europe, might as well lock this one up. I got the answer I needed

I'm off to my Rick's Jig land......