What can cause the track to gouge the inside of car wheels?

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ziggysdad
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What can cause the track to gouge the inside of car wheels?

Post by ziggysdad » Sat Mar 10, 2012 5:20 pm

I am tossing this out to you experts - I worked pretty hard building a Ford GT car, starting from the plans in one of the threads here. It was slightly weighted to the rear, with maximum wheelbase, and carved from a solid block (unlike original the balsa skateboard design). It was tuned to run straight, with the left front wheel up, which was allowed by the rules. The COM was probably higher than most of the other "fast" cars, but the car still ran at around 2.79 - 2.80 sec. in 4 races, without any incident... which would have put it in 1st or 2nd overall. But on the fifth race, the car took a big hop around where the ramp converts to flat. On the sixth race, the car had two smaller skips heading to the finish on the flat. Those times were over 2.84, dropping us to 5th placer overall.

The race format did not allow the kids to touch their cars from the finish line until the whole think was over. When we collected the car, the wheels still rolled true, but there where three distinct gouges on the inside of the "up" wheel in front, and one gouge on the rear wheel on the same side. There is no question the gouges came from impact with the aluminum track.

I was less than impressed with the stopping zone they had this year, which consisted of a bean-bag pillow over the track, and the cars were hitting it pretty fast.

What I wonder is if this kind of gouge problem is because we didn't use a rail-rider setup to keep the moving wheel on the rail? Maybe the car drifted in harder from the start of the fifth race due to being being set down off center or askew, which then marred the wheel and led to the skips in the last race. Or was it more likely to have been gouged at impact at the stopping section from bouncing around when it hit the bean bag pillow? I've never had this happen to a car I've built so I wonder was there something wrong with the track, or is this a common risk when you build a car with one wheel up and not set it to rail ride?

Thanks.



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Re: What can cause the track to gouge the inside of car whee

Post by ziggysdad » Sat Mar 10, 2012 6:30 pm

Here's what the wheel looked like when we got the car back after the race. Before the race it was 100% flat and true on edge, although I did not actually check spin balance with any special tools like some do.

Image



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Re: What can cause the track to gouge the inside of car whee

Post by FatSebastian » Sat Mar 10, 2012 8:53 pm

ziggysdad wrote:is this a common risk when you build a car with one wheel up and not set it to rail ride?
Thanks for the pic! Was this an aluminum track? I am not sure of the type of kit from which you are building; some kits have wheels made from softer plastic, so that might also be factor.

I might guess this is impact damage from the stop section given its severity. Perhaps there was something relatively sharp under that pillow. We've never seen this before, so I can only speculate. I would be inclined to ask if others racing that day experienced similar damage, or inquire of the trackmaster; they might have their own insights.



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Re: What can cause the track to gouge the inside of car whee

Post by ziggysdad » Sat Mar 10, 2012 9:55 pm

The wheels came with the kit, which was made by Indy Products. Track was aluminum, every car had one run in each lane. This car was the only one that I noticed take a big skip at the transition, and at first I thought maybe there was something on the track that caused the car to skip and come down hard on the rail.

When it happened twice on the next run in the flat, I though this car might be "bouncing" up when hitting the bean bag, then landing hard on the rail edge, rather than nose diving down between the track and the bag, as a wedge car would tend to do.

I can't think of anything except the rail that would have made contact with the part of the wheel, but it's always possible... I know they had a padded stopping box last year that the cars coasted into at the end of the track. Why mess with a good thing??



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Re: What can cause the track to gouge the inside of car whee

Post by Stan Pope » Sun Mar 11, 2012 2:14 pm

Good advice from FS!

The wheels appear to be of a softer plastic, which gives a "fuzzy appearance" when sanded.

To create a ding like that the wheel must have hit a high, sharp corner. At least the top corner of the center rail at a transition and perhaps in the braking section where the corners are almost even wth the axles.

While the car was tuned to run straight, when it was running on this track, it was biasing toward bringing the problem wheel into the rail, although not nearly as strongly as if the car had been tuned to guide by the rail. (Or, perhaps, it was that the car was staged a bit off in direction.) A properly tuned rail guide wheel would probably not suffer such a wound on that track!


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Re: What can cause the track to gouge the inside of car whee

Post by arrell » Mon Mar 12, 2012 9:27 am

My two cents says that it was most likely the fault of the track sections being misaligned at the joints (which I believe was said before). I ran a race this weekend with an aluminum track. While we were setting up the track and testing out the lanes (before the racing) we had a very similar accident to what you are explaining. I wish I had pictures because we saw similar damage to the car. The cause was the track sections were misaligned just a little bit. The track we were testing on had 4 lanes and each lane was a individual piece (http://pinewoodderbytrack.com/specs.html" target="_blank). Note the first track joint is in the transition from ramp to flat, as it is on many tracks. One section was pushed out of alignment, on our track, just enough for the wheel to catch. Take a look at the included link and the image of the track cross section. Note this isn't completely a fault of the manufacture but rather a track setup problem. The track cross section allows for a pointed edge to protrude into the lane (inside of the wheel) when improperly aligned. Adding to the problem could also be the fact that the track sections may have been bolted together opposite in orientation to what they should be. Note the image on the included link (Car Guides). The finish side of the guide is often tapered at the joint. If for some reason the track section was reversed the track misalignment could cause a sharper point to protrude into the lane. Not to fault your track setup people either, as it even may have loosened during the race. A hard hit, your car hitting it, may have made it looser. My advice would be that if you haven't already been involved with helping your group run the race and setup the track, get involved and be certain the track gets aligned next time. I know from plenty of experience myself it takes a lot of time and people to get these races running smoothly and without track problems.
Last edited by arrell on Mon Mar 12, 2012 12:09 pm, edited 1 time in total.



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Re: What can cause the track to gouge the inside of car whee

Post by gpraceman » Mon Mar 12, 2012 11:20 am

arrell wrote:My two cents says that it was most likely the fault of the track sections being misaligned at the joints (which I believe was said before).
Or more appropriately, the fault of the person setting up the track. The center marks on that track make it very easy to see if the lanes are aligned with each other. If not, it is pretty easy to make an adjustment.
arrell wrote:The track cross section allows for a pointed edge to protrude into the lane (inside of the wheel) when improperly misaligned. Adding to the problem could also be the fact that the track sections may have been bolted together opposite in orientation to what they should be. Note the image on the included link (Car Guides). The finish side of the guide is often tapered at the joint. If for some reason the track section was reversed the track misalignment could cause a sharper point to protrude into the lane. Not to fault your track setup people either, as it even may have loosened during the race. A hard hit, your car hitting it, may have made it looser. My advice would be that if you haven't already been involved with helping your group run the race and setup the track, get involved and be certain the track gets aligned next time. I know from plenty of experience myself it takes a lot of time and people to get these races running smoothly and without track problems.
It is pretty easy to tell if a track section is reversed. Since each lane is tongue and groove, so the tongues of all lanes should be on the same side of the track and the grooves on the other side.

For the track that I use, I have colored the center of each lane with colored electrical tape, so it is even easier to tell if the track sections are laid out correctly.


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Re: What can cause the track to gouge the inside of car whee

Post by rpcarpe » Mon Mar 12, 2012 12:05 pm

Sorry you had a dinged wheel... I have limited experience with Freedom Track, but do know that it takes a good while to set it up perfectly.
If they allowed car owners to stage cars, perhaps your son would have caught it and alerted race officials.


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