Derby Talk

I’ve never quite been able to align my cars right. When I roll the car forward, the wheels suck in, and when I roll the car backwards, they gravitate out. I believe this is what I’ve seen Stan refer to as “toe-in”. But, nothing that I ever do seems to correct the problem. And, I’ve had this same exact problem on something like 10 different cars that I’ve built over the years.

Our Derby rules state that you must use the slits out of the box (we can’t drill holes). So basically, I’m simply just pushing the nails into the slits. I really don’t know what else you can do. I suspect that the problem may stem from the fact that I always apply slightly more pressure on the outer tread of the wheels when sanding them. This gives the effect of slightly rounded wheels, yet you can’t detect it with the naked eye.

Anyone have any suggestions on how to align the wheels?

Gavin Chafin wrote:Our Derby rules state that you must use the slits out of the box (we can?t drill holes). So basically, I?m simply just pushing the nails into the slits. I really don?t know what else you can do.

You can still use a drill press to get straight axle holes without actually drilling a hole. Take an extra axle, cut the head off, and chuck the axle in the drill press. Turn the drill press on and press the spinning axle into the slot. The block is now ready to shape.

The obvious advantage is that you now have straight axle holes, so when the car body is done, it's easier to get the wheels in straight. And even if you don't spend a lot of time aligning the wheels, the default "just stick the axles in" position is aligned better.

A less obvious advantage is that you've pre-stressed the wood, so designs that remove a lot of wood and leave only a thin strut supporting the wheel are less likely to break when you insert the axle.

We've provided drill presses at our workshops for several years now, and it's made a huge difference. Each year, we used to have several cars that came in a few feet behind all the other cars, and often a car or two that barely crossed the finish line. Now, everyone crosses the finish line easily, and almost everyone is "in the pack".

I do have one of those plastic alignment tools. With the exception of the last block of wood that I looked at, the slits alwasy seem to be very straight to me. Is a drill press always going to be exact?

A drill press will greatly improve the process.

Also check out Maximum Velocity.com, he has a tool to the job real nice.

RACER X wrote:A drill press will greatly improve the process.

Also check out Maximum Velocity.com, he has a tool to the job real nice.

OK, I think you're referring to the Pro-Body tool. I purchased that last year after the races and I intend to try it this year. But, I also have one of those “wheel alignment tool kits” and I always check the slits of the cars to see how the alignment is. In the past, I’ve always found the slits to be as dead-on as possible. Note- within the last few days, I did discover that one of the bodies had slits that are a tad off and not acceptable for racing.

So, if you have a car where the wheel alignment tool kit shows that the alignment is dead-on, it would seem to me that to then take the Pro-Body tool and drill through those same slits could likely cause more damage than good. For example, it could possibly widen the hole and make aligning the car to be more difficult than it already is.

I have every tool from Max-V. I love the Pro-hub tool and I’m looking forward to using the Pro-axle tool and the Pro-wheel tool. But, the Pro-Body tool is one that I’m quite sold on yet. I think it’s perfect for drilling new holes or slits, but I’m hesitant to use it to re-drill slits that I believe are already perfectly aligned.

Even if the slots are perfectly aligned for-aft, you should also provide a way for the nail to konw where to go so that it is well aligned up-down. An error in either will slow your car down.

If you drill through the center of the slot, you should not be removing enough material to leave the axle nail loose.

Remember, too, that up-down alignment is aided if the top of the slot (inside or outside end of the nail) is available as a leverage point.

Remember, too, that up-down alignment is aided if the top of the slot (inside or outside end of the nail) is available as a leverage point.

Stan, I didn't follow that one. Can you say that in a different way?

Gavin Chafin wrote:

Remember, too, that up-down alignment is aided if the top of the slot (inside or outside end of the nail) is available as a leverage point.

Stan, I didn't follow that one. Can you say that in a different way?

You will follow it easily after you read the procedure.

Gavin Chafin wrote:I’ve never quite been able to align my cars right. When I roll the car forward, the wheels suck in, and when I roll the car backwards, they gravitate out. I believe this is what I’ve seen Stan refer to as “toe-in”. But, nothing that I ever do seems to correct the problem. And, I’ve had this same exact problem on something like 10 different cars that I’ve built over the years.

This condition is one that you must accept. The wheels are going to find their way to a second axis. What is important is that the amount of force which the wheels find their way there is minimized and that the car runs straight down the track.

Gavin Chafin wrote: Our Derby rules state that you must use the slits out of the box (we can’t drill holes). So basically, I’m simply just pushing the nails into the slits. I really don’t know what else you can do. I suspect that the problem may stem from the fact that I always apply slightly more pressure on the outer tread of the wheels when sanding them. This gives the effect of slightly rounded wheels, yet you can’t detect it with the naked eye.

I'm glad you're following the rules. But a question here arises: do the rules say use the slots or do they also stipulate no drilling? In either case, any type of "drilling" or "slot modification" which you may need to do should be both accurate and minute. Also, I would never just push the nails in. This may cause more harm than good. And as far as slightly rounding your wheels - if your rules don't allow for it, don't do it. Nothing is worse for a Scout, Parent or Judge than to have to disqualify a car.

Gavin Chafin wrote: Anyone have any suggestions on how to align the wheels?

A few pointers here. There are three basic geometries to be concerned with. CAMBER: This is the top/bottom tilt of the wheel and is a low wear angle (the better "tilt" of the two). This can and should be adjusted to a slight negative angle. You can accomplish this by tilting the head of the nails up after you have set your toe angle to 0. TOE: This is the forward/back tilt of the wheel and is a high wear angle (the bad one). This must be reduced to 0. This is the more critical angle and as such the more difficult one to produce. Basically, you need all four nails (notice I said nails because alignment is based upon spindle measurement, not wheel measurement and once you have properly aligned spindles any tracking problems the vehicle may have are from the wheels and must be corrected as such, not with spindle adjustments) to be aligned to each other and to the body. A sure way of doing this is with a jig. I'm not sure where you can purchase one, but simply you need something to guide each "modification" tool into the slots to assure proper angle. SET-BACK: This is how the spindles line up across from each other and is not a wear angle. This will cause your car to lead to one side or the other and can also be corrected with a jig.

The other thing you want to make sure of is that the vehicle is properly planed. There should be an even amount of downward force being applied to all the wheels (3 or 4).

Regardless of any modifications you are going to attempt, make certain they are within the rules.

darin_mcgrew wrote: You can still use a drill press to get straight axle holes without actually drilling a hole. Take an extra axle, cut the head off, and chuck the axle in the drill press. Turn the drill press on and press the spinning axle into the slot. The block is now ready to shape.

This is a "clever" idea. Here you are not actually drilling a hole, you're more or less pressing a hole.

Jungle Jim wrote:On Sat Nov 29, 2003 at 12:00 am, JJ said a lot!

Without arguing all the details, I don't see this "aligned" definition transferring to PWD cars. You are defining almost, but not quite, best target states for camber and weight distribution.

My observations indicate significant friction and tracking superiority when alignment is "dead-on", and significant time advantage when weight distribution matches track's geometry but stays just within the wheel's traction limits ("death rattle" avoidance).

However, I am happy for my opponents to follow your direction to the letter, so I won't argue vehemently.

darin_mcgrew wrote:You can still use a drill press to get straight axle holes without actually drilling a hole. Take an extra axle, cut the head off, and chuck the axle in the drill press. Turn the drill press on and press the spinning axle into the slot. The block is now ready to shape.

Jungle Jim wrote:This is a "clever" idea. Here you are not actually drilling a hole, you're more or less pressing a hole.

As I said, we've used this technique for several years. Using an axle instead of a drill bit is a little safer (both for fingers and for the block), and it's certainly cheaper (the right size bits are expensive and hard to find).

Originally, we didn't even turn on the drill press. We just pressed the axle into the wood. This works, but it's easy to bend the axle, and it's sometimes difficult to get the axle to come back out of the block. Turning on the drill press solves both problems.

With one of our cars, I'm putting a lot of pressure on my son to do the majority of the work (and it's a challenge to get him to attend for more than a few minutes at a time). I noticed that the axle slots did not appear to be exact. So, I pulled out the Pro-body tool and gave it a try. It took a few minutes to squeeze it on (had to sand down the block for a few minutes), but I was pretty pleased with the results. Not only should the slots be better now, but it also creates a slight guide hole where the nails will go in. I’m hoping this will ensure that all of the nails will be inserted at exactly the same height (which should help with alignment). Also, I figure that we might be able to salvage the top half of the car (the car is a wedge), use the Pro-body tool to drill new slots, and even make a second car out of it (talk about being thrifty).

Gavin, I used our Pro-Body Tool for the first time yesterday. We've had it for a few months now but the local Council Store hasn't had any pwd car kits. Strangley I found a few BSA kits while in a local clothing store yesterday and had to rush home to give it a try. I first checked to see if the slots were square and all for blocks were off the same - around 1/64 to 1/32 inch. So much for straight slots... Anyway, I used the Pro-Body Tool on one block and had to tinker with aligning it to best fit the slots that were there. I ended up with an axle hole on the leading edge of the slots on one side (can't remember which side) and an axle hole on the trailing edge of the slots on the other side. I guess all of the blocks were slightly angled when they were cut. I'm going to take everything to work and use the coordinate measuring system to check it all but it sure looks like your cars will end up hitting a rail/center guide if you don't use something to ensure the axle holes are straight. The Pro-Body Tool may not be the only way to do this but it is readily avaliable and even a young boy could use it.

Da Graphite Kid

Da Graphite Kid wrote:Gavin, I used our Pro-Body Tool for the first time yesterday. We've had it for a few months now but the local Council Store hasn't had any pwd car kits. Strangley I found a few BSA kits while in a local clothing store yesterday and had to rush home to give it a try. I first checked to see if the slots were square and all for blocks were off the same - around 1/64 to 1/32 inch. So much for straight slots... Anyway, I used the Pro-Body Tool on one block and had to tinker with aligning it to best fit the slots that were there. I ended up with an axle hole on the leading edge of the slots on one side (can't remember which side) and an axle hole on the trailing edge of the slots on the other side. I guess all of the blocks were slightly angled when they were cut. I'm going to take everything to work and use the coordinate measuring system to check it all but it sure looks like your cars will end up hitting a rail/center guide if you don't use something to ensure the axle holes are straight. The Pro-Body Tool may not be the only way to do this but it is readily avaliable and even a young boy could use it.

Da Graphite Kid

I had the same experience, except if appears that my back slots we're not aligned too well. The hole came out sightly in front of the slots on the car's left side and slightly behind the slots on the car's left side. I just hope that Pro-body too is accurate, though (alhtough, I guess I'll find out when I eventually put the wheels on). I noticed that when you run the drill bit through the Pro-body tool, there is a bit of "play". Before I first used the tool, I assumed there would be no play whatsoever.