Car Width

[Ohly]

I know this has been covered but can't find the answer on the forum... What is the ideal Car Width? Rules state that it has to be 1 - 3/4 Inches between wheels so it clear the guilds.

Should I just leave this alone or shave off as much as possible? I thought I read somewhere that the car should be as narrow as possible but looking at the other "Awesome" Cars they fit perfect in the Silver Bullet. Which might be my answer.

 

[DuckOfAllTrades]

I know this has been covered but can't find the answer on the forum... What is the ideal Car Width? Rules state that it has to be 1 - 3/4 Inches between wheels so it clear the guilds.

Should I just leave this alone or shave off as much as possible? I thought I read somewhere that the car should be as narrow as possible but looking at the other "Awesome" Cars they fit perfect in the Silver Bullet. Which might be my answer.

I will tell you what I do on my scout builds, but I admittedly am NOT a pro! I shave 1/32 off the dominant wheel side. They say you can get away with this, that it's not noticeable and will meet the 1 - 3/4 width. Depends on how and how closely they check and how well the shape of your car hides it. You may even take more off. The closer you get the dominant wheel riding the rail, the better your back wheels will stay off said rail. It is possible to go too much.

I'm always worried they will not pass my car for being to thin once I do this, so to get around it, I add 1/32 back onto the non dominant side wheel so it's still technically 1 - 3/4 inches! Perfectly within the rules. I've also heard you can shave off both sides.

 

[CFD Engineer]

My rules state 1-3/4" is the minimum spacing required for wheels, not the body. And the wheels inside surface sticks out about 1/16" from the car. So I bring my front wheels in (narrow the front body) 1/16" each side, which puts the wheels back @ 1-3/4"
For reference, the center guide rail is 1-5/8" on the best track. so there is wiggle room there. Also this 1-3/4" wheel rule is a difficult measurement to make due to the slop in the axles/bores and the hub/body gap.

 

[Ohly]

My rules state 1-3/4" is the minimum spacing required for wheels, not the body. And the wheels inside surface sticks out about 1/16" from the car. So I bring my front wheels in (narrow the front body) 1/16" each side, which puts the wheels back @ 1-3/4"
For reference, the center guide rail is 1-5/8" on the best track. so there is wiggle room there. Also this 1-3/4" wheel rule is a difficult measurement to make due to the slop in the axles/bores and the hub/body gap.

My rules state 1-3/4" is the minimum spacing required for wheels, not the body. And the wheels inside surface sticks out about 1/16" from the car. So I bring my front wheels in (narrow the front body) 1/16" each side, which puts the wheels back @ 1-3/4"
For reference, the center guide rail is 1-5/8" on the best track. so there is wiggle room there. Also this 1-3/4" wheel rule is a difficult measurement to make due to the slop in the axles/bores and the hub/body gap.

My rules state 1-3/4" is the minimum spacing required for wheels, not the body. And the wheels inside surface sticks out about 1/16" from the car. So I bring my front wheels in (narrow the front body) 1/16" each side, which puts the wheels back @ 1-3/4"
For reference, the center guide rail is 1-5/8" on the best track. so there is wiggle room there. Also this 1-3/4" wheel rule is a difficult measurement to make due to the slop in the axles/bores and the hub/body gap.

I will give it a try. We are making three cars, so we can experiment with different styles.

 

[DuckOfAllTrades]

My rules state 1-3/4" is the minimum spacing required for wheels, not the body. And the wheels inside surface sticks out about 1/16" from the car. So I bring my front wheels in (narrow the front body) 1/16" each side, which puts the wheels back @ 1-3/4"
For reference, the center guide rail is 1-5/8" on the best track. so there is wiggle room there. Also this 1-3/4" wheel rule is a difficult measurement to make due to the slop in the axles/bores and the hub/body gap.

You my friend are a genius! That’s how you win the Pinewood Derby!

 

[Wolfram Racing]

If your drilling using a fixture, keep it the width of the fixture or have one side be a reference edge that you KNOW is cut straight. The advantage you get from a slightly narrowed body isn't going to compensate for sacrificing alignment.

 

[Pinewood Outlaw]

I cut a 1/16 off dfw side and then sand the rest at a taper towards the rear. Makes it hard to tell just by looking.....and thats all they do around here is look. Of there is ever a doubt about clearance issues they place car on the track to make sure it clears.

 

[TRE]

I cut a 1/16 off dfw side and then sand the rest at a taper towards the rear. Makes it hard to tell just by looking.....and thats all they do around here is look. Of there is ever a doubt about clearance issues they place car on the track to make sure it clears.

Thats the way it should be done

 

[DuckOfAllTrades]

I cut a 1/16 off dfw side and then sand the rest at a taper towards the rear. Makes it hard to tell just by looking.....and thats all they do around here is look. Of there is ever a doubt about clearance issues they place car on the track to make sure it clears.

I want to try this! How exactly does the taper go? I’m assuming you must shave the DFW flat and not an angle the entire length of the car, how do you make it look so it’s not thinner without doing the entire side at an angle? Hope that makes sense.

 

[Wolfram Racing]

I keep the taper the whole way up the car, from the end of the weight section all the way to the front of the car. It looks funny on the track, yeah. I'm not interested in looking good just yet. Hell, I'd race a garbage truck down the track if I thought it would go faster..BUT, I'm firing up the CNC Mill this weekend to cut a little differently. Only the track will tell if it helps.

 

[Ohly]

I did the taper the full way down the car... BUT it was because of a poor power sanding issue.... Lucky I have the SBE and this forum, now able to save the car. Which I put some blood, sweat, and now tears into...

 

[Pinewood Outlaw]

I keep the taper the whole way up the car, from the end of the weight section all the way to the front of the car. It looks funny on the track, yeah. I'm not interested in looking good just yet. Hell, I'd race a garbage truck down the track if I thought it would go faster..BUT, I'm firing up the CNC Mill this weekend to cut a little differently. Only the track will tell if it helps.

Wish I had the know how to run a cnc mill....guess I could always go back to school.

 

[DerbyCrazy]

You guys are making me feel better for districts next week. We used a block plain to taper the dominant side after drilling, taking about 1/16 off where the front wheel is. I was a little worried about the our rule that there must be 1 3/4 inches between wheels....didn't think about the wheel gaps making up the difference.

 

[Wolfram Racing]

Wish I had the know how to run a cnc mill....guess I could always go back to school.

Outlaw...it's not super difficult. One of the guys at work showed me how to run it in 10 minutes. I draw the design in LibreCAD (freeware). Export the DXF file to another program that converts the DXF to G-Code to run the mill (software came with the mill). You have to modify the G-Code slightly, like 2 lines of code and that's it. The GUI on the Mill makes it easy to set the home position and you press go.
The difficult part (for me) is cutting fine structures without the vibration snapping them. On the mill I use, anything 1/8 inch or smaller seems to be an area of risk. I get about 50% yield for a body cut with 1/8 inch structures...but I have a plan to improve that. The other catch is to make sure you use the right bits for the depth of cut. For a 1/4 inch body, I used a 2mm bit and it hasn't broken yet. I recently ordered a set of 1.2mm bits to see if I can push that to smaller cuts. We'll see. I think I can get it to work ok if I slow the feed rate down, but that's also going to dull the bits sooner.
I also used a laser cutter, but found the CNC makes cleaner/more vertical sidewalls. I'm sure I could fix that on the laser with different lenses, etc. but I'm not cutting body's to sell...so the CNC works for me.
You can easily taper more than 1/16 inch and still maintain 1 3/4 inch between the wheels. Sometimes I'll taper 1/8 and still have plenty of clearance.