Bad Track Guide transition

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chromegsx
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Bad Track Guide transition

Post by chromegsx »

Was editing my tribute video for my son's recent win...This is a snapshot series of 3 frames from video of our 2nd race. When I saw this I think I looked like this.. :jawdrop: We still won by .01 at 2.62 but I think this lane cost us .02... and maybe .01 on a fanals race. We're on the green track. In a matter of .06 seconds we were back on the straight and narrow.
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Stan Pope
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Re: Bad Track Guide transition

Post by Stan Pope »

Looks like the DFW hit the edge of the center guide and popped the lifted wheel against the rail! Did you have a chance to look at how the track was set up and verify the bad alignment of the lane guide?
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Re: Bad Track Guide transition

Post by Speedster »

I'm impressed with the pictures.
Did this same situation happen more than once? Was there Positive camber on that front wheel?
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sporty
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Re: Bad Track Guide transition

Post by sporty »

thats a pretty wild track. I wonder, how lever the track is. wider tracks like that, esp older ones, tend to have some amont of twist or warping in them.

It looks like a possible non professional built track. so if that is the case, then it might not have been built as well as it should. I wonder what type of wood was used. it looks a tan thin for a wooden track, or when that then, often a very high grade and quality of wood is used.


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chromegsx
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Re: Bad Track Guide transition

Post by chromegsx »

Yes, the DFW is hitting a guide edge. It's the only lane I noticed it on and the only race of 2 that the time reflected it. I noticed the same thing on test/tune night after reviewing video. and we did have extra positive camber on the front wheel to attempt to account for this possibility since I suspected a similar situation last year when RR on the opposite side. Apparently we don't have enough camber nor do I think we will ever have enough.

It's not a professional track that I know of. I think a volunteer that helps with the derby built it many many years ago. I know leveling is probably and issue too. and I know for a fact the curve to flat transition is raised (bottom of curve is lower than flat). the transition seems smooth but the curve just droops below the transition before leveling out... so there is a slight wheelie pop coming out of the curve. and it is worse on the red side than the yellow, but faster times seem to be run on the red and blue tracks by all cars. so I'm thinking that he curve section may have a twist in it than can't be taken out without some serious reinforcement. I'm told they tried fixing this but it seems it messes something else up when they do.

I thought about mentioning it before the race but I'm not one to nitpick volunteers to get something just perfect... plus I'm not sure any of them heard of RR and know how important those guide edges are. Unfortunately I didn't get a chance to check the track out post race either as they start tearing it down before everyone leaves and we were busy taking pictures of our winner and chatting with friends.
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Re: Bad Track Guide transition

Post by FatSebastian »

sporty wrote:I wonder what type of wood was used. it looks a tan thin for a wooden track, or when that then, often a very high grade and quality of wood is used.
To me it looked like painted wood lath fastened to Masonite panels, which is quite flexible (and generally inexpensive).
chromegsx wrote:Yes, the DFW is hitting a guide edge.
There is a major support structure directly underneath where the deflection occurs. That caused me to suspect that this might be an area where two panels abut. A little tapering of the guide rail before the abutment might help if that is the case.

RRing with the opposite wheel might be something to think about for next year.
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Re: Bad Track Guide transition

Post by Shawn Stebleton »

The uphill end of the lower section needs to have a small taper on the lane guide edges. Just 1mm narrower tapering to full width in about 1/4" is fine. The car should transition from the full-width lane guide across the joint to the tapered lane guide. This really should be done for all joints but only on the end the cars transition ONTO. Never on the end they are leaving. The taper "points" to the start gate. Look at the instructions for the Piantedosi tracks and scroll down to see how they do it as an example. I found it here:
http://www.pinewoodderbytrack.com/specs.html

Talk to your pack's PWD chair and let him/her know you saw this issue with several cars and know how to fix it. Offer to set up the track the next year. I've set up our pack's track the last 6 years and haven't had any issues. :bigups: Use your son's previous years' car to test it. Also have a railrider that rides on the other side for fairness.

The boys can accept getting beaten by another boy, but not with getting beaten by the track. It is an adult responsibility to ensure the track doesn't become another thing to try to beat (survive).
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Re: Bad Track Guide transition

Post by FatSebastian »

FatSebastian wrote:A little tapering of the guide rail before the abutment might help if that is the case.
Shawn Stebleton wrote:The uphill end of the lower section needs to have a small taper on the lane guide edges...
Thanks for finding that Shawn. I had looked for an illustration of what I meant by "tapering" but obviously not as hard as you did.

Image
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Re: Bad Track Guide transition

Post by Shawn Stebleton »

FatSebastian wrote: Image
Please note that the image is NOT to scale. It's exaggerated to demonstrate the concept. Only 1mm narrowing is sufficient.
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Re: Bad Track Guide transition

Post by FatSebastian »

Shawn Stebleton wrote:Only 1mm narrowing is sufficient.
...unless, of course, the sections are misaligned by more than 1 mm. ;)
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Re: Bad Track Guide transition

Post by Shawn Stebleton »

FatSebastian wrote:
Shawn Stebleton wrote:Only 1mm narrowing is sufficient.
...unless, of course, the sections are misaligned by more than 1 mm. ;)
In that case, inspect the track and adjust your amount of taper as necessary. :o
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Re: Bad Track Guide transition

Post by Shawn Stebleton »

One other thing....

When setting up the track, I use a level as a straightedge and make sure the center rail edge of one section is inline with the center rail edge of the next. We have a Piantedosi wooden 3-lane track and checking the outer edge of each of the outer lane rails is sufficient, as it is very well designed and built. The level allows me to check the straightness of each rail edge transition. The best guide is looking at the track from the end to make sure all lanes are as straight as possible.

If, in checking your pack's track, you find that you cannot get all lane rails lined up simultaneously, then one or more lanes will have to be corrected. Short of removing and reinstalling the errant rail(s), you may need to essentially make a longer taper on one side. Maybe even both sides, if the downhill section the cars transition ONTO has a rail that is wider than what they transition off of. Use calipers to measure. You would have to use your best judgement as to how much length to taper, but I would still put in the additional taper at the very end like shown above to allow for some misalignment in setup.
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Curse You Red Baron!
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Re: Bad Track Guide transition

Post by Curse You Red Baron! »

My scout and I just endured the same thing this weekend. There was an obvious bad transition on lane 3, but nobody was going to fix it. This is our last half year in Cub Scouts, my son crosses over next month, but in prior years I had helped with the track and I always checked the transitions (sigh...). Luckily it was the very last track segment with the problem, but we had a rail-rider that was practically airborne crossing the finish line. It probably cost us between .01 and .02 on that lane, but frankly times were all over the place. Luckily we had a very fast car, so we won both Den and Pack by .011 second average (I have yet to post thanks to all the ST regulars for all the help over the years, I plan to post some pics and do that then.)
If you don't have a new aluminum track, I think the only way to do this is to be there and check those transitions yourself. Everyone is a volunteer and has places to be, so unless you know of someone else who cares as much as you do about PWD and a good racing experience and who is going to be there to check it, there is nothing like doing it yourself.
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Re: Bad Track Guide transition

Post by Stan Pope »

Shawn Stebleton wrote:When setting up the track, I use a level as a straightedge and make sure the center rail edge of one section is inline with the center rail edge of the next.
This is a pretty good test of the joints, but is time consuming and subject to some error. A very good test is to use a small block of wood with straight sides and sharp, squared-off corners on the ends. Place the block against the rail and track just upstream from the joint and slide it down across the joint. If it "catches" there is a problem. Repeat on each side of each rail at each joint.
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Shawn Stebleton
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Re: Bad Track Guide transition

Post by Shawn Stebleton »

Stan Pope wrote:This is a pretty good test of the joints, but is time consuming and subject to some error. A very good test is to use a small block of wood with straight sides and sharp, squared-off corners on the ends. Place the block against the rail and track just upstream from the joint and slide it down across the joint. If it "catches" there is a problem. Repeat on each side of each rail at each joint.
I use the straightedge (level) to help push the sections into alignment. I have the mounting plates loosened about 1 or 2 turns of the screws from being tight. They slip when "encouraged" but stay put when not. I grasp both the straightedge, which straddles the joint, and track pieces, one hand on each section of the joint, and squeeze them together so the track guide rails are flush against the entire length of the straightedge. I then go to the end of the track and visually note the straightness of the track sections. Once satisfied, I tighten, then check again.

With the taper built into the Piantedosi tracks, I slide my finger to verify the indentation I would expect. I do so on all 6 rails of the 3 lane guides on our track. It works for our track beautifully.

I've set our track up the last 6 years for both the pack's Fun Day and for the actual pack Pinewood Derby. With probably 1000-1500 heats run each year between the two events, only one car has come off, and that was due to the builder making a three-wheeler with no fourth wheel and no guide pin. No car has hit a misaligned rail.

It's not that bad, time-wise. I feel it is time well spent.
Shawn
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