88 replies to this topic

[crazyphysicsteacher]

Dom, I can't wait to hear. I hope you like to put the body pins as far apart as possible.

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[Dominator]

O.K. so here we go into pin tube placement. 

 

Most racers use more than one chassis manufacturer.  That being said pin tube placement is not the same between manufacturers.  This makes swapping bodies between different chassis almost impossible.  Simple solution is take your go to chassis and measure from the center of the front axle to the center of the front pin tube.  Then measure the distance between the front and rear pin tubes.  Using a good ruler (I prefer a metal one in 1/32" increments) place the chassis on a jig and use the line on the jig for the front axle to measure to the center of the pin tube.  Next measure the vertical height of the pin tube from the jig to the bottom of the pin tube.  Usually you can adjust vertical height by adding a piece of .016 or .032 brass to the top of the pan.   Once you have these measurements you can adjust the pin tube placement on your other cars so bodies will be interchangeable. 

 

So is it better to have the pin tube placed higher or lower on the pan?  Higher is easier for those with difficulty handling small object to pin the body.  The down side is the higher the pin is placed the less side flex the body will have.  This is why I prefer to mount my tubes on .064 side pans or if building with .032 pans use a .032 spacer between the pin tube and pan.  I feel this is a good compromise for ease of mounting a body and handling.  Can you see a difference in lap times?  Possible on some tracks but may be less on others.  Remember than all the little things will make a bigger difference than one small thing. 

 

I'll use coupe/can am for a tube placement example.   Usually wider/longer supports are better.  These cars have pretty good down force but you still want the body to move freely.  I place my front pin tubes 26/32" (13/16") on center from the center of the front axle.  The rear pin tubes are 2-3/32" behind the front pin tubes measured from center to center.  What will moving the pin tubes towards the middle do?  Depending on the chassis design it could free the car up or tighten it up.  The body will have more vertical flex at the rear and nose.  This is where balance is key.  Moving the pin placement even a 1/16" can make a huge difference in how the car drives.  Smoother car can equal more consistent laps. 

 

This can help tune F1's also as these bodies have little down force.  When I designed the Snake with adjustable center weight it also created an option for the body to be mounted in different combination.  On higher speed tracks I use the standard pin tube placement (located at the further point front and rear).  While testing on a Gerding King and on an older Ogilvie King I did not find an advantage of moving the front pin to one of the three tubes behind it.  What did make a big difference was moving the rear pin to the next one forward.  On the Gerding king the car was looser coming up the donut.  On the Ogilvie it made the car smoother up the donut and on the exit of the turns.  This was .050 faster and more consistent.

 

 

Body placement is also big and moving the body even 1/32" front or back can change the handling of a car regardless of the class.    More on that when everyone is ready.

[SpeedyNH]

Thanks Dom!

[Jerry123]

Simple solution is take your go to chassis and measure from the center of the front axle to the center of the front pin tube.  Then measure the distance between the front and rear pin tubes.  Using a good ruler (I prefer a metal one in 1/32" increments) place the chassis on a jig and use the line on the jig for the front axle to measure to the center of the pin tube.  Next measure the vertical height of the pin tube from the jig to the bottom of the pin tube.  Usually you can adjust vertical height by adding a piece of .016 or .032 brass to the top of the pan.  

Wouldn't it be great if the chassis jigs had a slider on the side with an attachment that could adjust horizontally, lock in place, and vertically then lock in place, so that you could replicate every time without the ruler? Almost like an adaptation of the body mounting jig concept...

Maybe even scribe/machine in a ruler on the top side of the jig near the edge in 1/32 increments with the front axle being zero so you can easily take a measurement.

I'm sure Chicagoland or Precision could machine something like that up.

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[Shruska55]

Steve,

 

I bought a neat machined  body pin jig from MarkH. Send him a PM and he can give you the details.

 

It's been great for a guy who needs glasses on top of glasses to see up close...

 

ScottH

[Shiggy]

 
Body placement is also big and moving the body even 1/32" front or back can change the handling of a car regardless of the class.    More on that when everyone is ready.

Ready, Dom. My body placement tends to be limited by body shape clearances, chassis wheelbase and guide lead

[Danny Zona]

 
I think you missed my point. When a racer can't drive well enough to keep a fast but hard to drive car in the slot he's rarely competitive. He'll make more laps with an easier to drive car.

I'm not sure on your point because I've never experienced that point myself.

For me the car that is the easiest to drive is always my fastest car because it's the car that is easiest to drive. I've never had a hard to drive car rip fast laps like an easy to drive car.

Maybe it's different for other racers.

[crazyphysicsteacher]

I'm not sure on your point because I've never experienced that point myself.

For me the car that is the easiest to drive is always my fastest car because it's the car that is easiest to drive. I've never had a hard to drive car rip fast laps like an easy to drive car.

Maybe it's different for other racers.

I think they are referring to that car that you hit the real fast lap with but is not consistent. It is not the fastest car but hits that one good qualifying lap and that's it. It either drops off or just has to driven over the edge to hit the lap. Like hitting the donut on the hill climb, car can do I t times in a row but you miss a hair and it jumps off.

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[Danny Zona]

I think they are referring to that car that you hit the real fast lap with but is not consistent. It is not the fastest car but hits that one good qualifying lap and that's it. It either drops off or just has to driven over the edge to hit the lap. Like hitting the donut on the hill climb, car can do I t times in a row but you miss a hair and it jumps off.

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I kinda get it I guess but I have not experienced that myself.

[Matt Sheldon]

Wouldn't it be great if the chassis jigs had a slider on the side with an attachment that could adjust horizontally, lock in place, and vertically then lock in place, so that you could replicate every time without the ruler? Almost like an adaptation of the body mounting jig concept...

Maybe even scribe/machine in a ruler on the top side of the jig near the edge in 1/32 increments with the front axle being zero so you can easily take a measurement.

I'm sure Chicagoland or Precision could machine something like that up.

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In the very beginning when Precision came out with their Deluxe retro jig, that option was available.

[Dominator]

O.K. body talk time.  For can am I'll use a Parma Ti22 NN (#1043) for the example.  The cut line that Parma provides is not a bad starting point but I usually ignore this.  I make my cut line measuring 1-3/16" down from the top of the body at the rear and leave about 1/16" for a front bumper.  This will allow for any trimming that might be needed.  Once I marked the body at the rear I use a piece of pin striping tape to create by guide. 

 

 

 

Once the body is trimmed I place it on a flat block.  Adjust the cut line until the line sits flat on the block and is at the desired height.  Next place your chassis on a block with cut outs for the wheels and guide.  Place the body over chassis and pick it up squaring the body to the chassis.  For Ti22's I usually start mount them 1/4" ahead of the guide.  This is based off a 15/16" guide lead and a Red Fox guide.  Carefully place the body and chassis together back on the block and pin the body to the chassis.  This step can be easier if you have a body mounting jig. 

 

Place the pinned body and chassis on a block and check to make sure it is level.  If the body is with 1/32" of an inch you can make the adjustment when reinforcing the pin holes.  Double check the front to back positioning is where you want it. 

 

For body reinforcement the simplest thing to use is body armor.  Some have been using parachute tape to give the body a little more flex.  Place a small square over each pin hole and push a pin through each hole.  Place the body on the chassis again and check for straightness.  This is the only reinforcement the body needs.  Cut out the wheel wheels with a pair of curved scissors.  You can use a round sanding drum to finish rounding out the wheel wells if desired. 

 

 

Rear spoilers are another huge thing to tune a car with.  Most use .004 or .005.  Attaching the spoiler to the body can be done is a number of ways.  I prefer to leave about 3/16" at the rear of the body and attach the spoiler with double sided scotch tape.  The tape is strong enough to last a race or two.  There are a number of manufactures, Chicago Land for example, that sell precut/bent wings with a stronger adhesion.  When mounting the spoiler you do not want to take away flex from the body.  I usually notch the middle third of the mounting surface of the spoiler.  One last tip for spoilers.  On higher speed tracks or tracks with high bit I usually have use a spoiler height of 15/32" instead of 1/2".  1/32" doesn't sound like a lot but it can make a big difference in straight away and cornering speed. 

 

 

 

If you using a Parma Lola T-70 coupe I use the same specs except I mount the body 1/8" ahead of the guide.

 

If you are using a Parma M7 F1 body mount the body 1/8" ahead of the guide and mount it just below the max height of 1-3/8".  The cut line on this one is pretty good.  I make my cut at the top of the cut line Parma molded in.

 

Don't be afraid to play with bodies mounted more forward or back.  I generally have 2-3 bodies per class.  All are mounted the same height but they are mounted more forward or back (1/32"-1/16" increments) to help with tuning.  At time this can make a bigger impact than changing a motor. 

[crazyphysicsteacher]

A masters secrets. Listen to Dom about the body height, changed my car by more than I can count with the ti22.

Jerry, I tried to make something like that awhile back but ran out of steam on it. I made the device to replicate spacing but never had enough time to make it reference to the front Axle correctly. With this extra time I may try again.


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[crazyphysicsteacher]

I just need to redesign to locate to the front Axle. I had put holes in to match up to I think the jk clip spacing front to back. Someone in the past had one made from metal.

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[Upfront slot cars]

Pretty nice unit ! I just have my jig marked with a dremel tool so I put the pins in the same location front and back every time. I use the same thickness side pans and pin tube supports on every chassis so the height stays the same. That little jig could be very useful at the track where you usually dont have the jig with you. Nice job !