Cars jumping 1 lane only

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jimsz
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Cars jumping 1 lane only

Post by jimsz » Thu Feb 28, 2019 9:43 am

We replaced our old Best Track this year with a new one. It's a great track except we have a problem with cars jumping on the outside lane. Most of the cars jumping are more backloaded with weight. If we run the cars backwards they are fine.

All seams on the track appear to be flush and tight, nothing on the lanes such as nicks/imperfections, etc. Track sections are help together with a vice style clamp.

Track details - 4 lane, 42 foot, manual release. StocKar kits (the old Shape N Race design), weight on bottom of cars. The lane jumping is the lane of the lever release side with the release being operated manually.

We have our races next week and then host the regional races for this part of the state- anyone have any suggestions on what the problem could be? I'm really stumped since it is only happening on this lane.



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Vitamin K
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Re: Cars jumping 1 lane only

Post by Vitamin K » Thu Feb 28, 2019 10:11 am

jimsz wrote:
Thu Feb 28, 2019 9:43 am
We replaced our old Best Track this year with a new one. It's a great track except we have a problem with cars jumping on the outside lane. Most of the cars jumping are more backloaded with weight. If we run the cars backwards they are fine.

All seams on the track appear to be flush and tight, nothing on the lanes such as nicks/imperfections, etc. Track sections are help together with a vice style clamp.

Track details - 4 lane, 42 foot, manual release. StocKar kits (the old Shape N Race design), weight on bottom of cars. The lane jumping is the lane of the lever release side with the release being operated manually.

We have our races next week and then host the regional races for this part of the state- anyone have any suggestions on what the problem could be? I'm really stumped since it is only happening on this lane.
Hmmm.

Don't know the problem offhand, but a few other questions:

- Is the track jumping consistently at the same spot along the length of the track? If so, where?
- How aggressively backweighted are the jumping cars?



jimsz
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Re: Cars jumping 1 lane only

Post by jimsz » Thu Feb 28, 2019 10:59 am

About half are In the same general area just after the curved section, the rest all all past that point.

The ones that jump soonest are heaviest in the back with lesser weight if any in the middle or front.



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Darin McGrew
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Re: Cars jumping 1 lane only

Post by Darin McGrew » Thu Feb 28, 2019 12:08 pm

Without examining the track, all I can say is that there's something different about that lane that causes the cars to jump. If you can't figure out what it is by watching cars jump, then maybe you could video a car jumping and watch in slow motion.



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gpraceman
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Re: Cars jumping 1 lane only

Post by gpraceman » Thu Feb 28, 2019 1:54 pm

1. Check the section joints. The running surface of the downhill section should be the same level, if not a tad lower than the uphill section. You don't want it to be any higher, as that will cause a speed bump. If you have a speed bump, with a mallet and a scrap of wood, you can tap it down. Take the wood block and run it along the running surface. It should not catch on the edge of the downhill section.
2. Check the lane guides. You don't want the edge of the downhill side lane guide sticking out any for a wheel to catch on. I use a fine file on the uphill end of the lane guides to taper them at about a 30 degree angle to make sure there will not be an edge for a wheel to catch on. Use the wood block to check the lane guide joints and make sure that it doesn't catch at all.
3. Check for burrs along the running surface, lane guides and section end edges. The aluminum is very soft and easy to get dinged up. A fine file can address any burrs.


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jimsz
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Re: Cars jumping 1 lane only

Post by jimsz » Thu Feb 28, 2019 3:06 pm

I'll give it a try. I didn't think of the wood to check. Thank you!

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Re: Cars jumping 1 lane only

Post by Speedster » Thu Feb 28, 2019 3:11 pm

What's the COM on the cars that are jumping? Are the jumping cars all rail riding? Positive camber on the dfw?

Just for Fun, pull the section out and turn it around. Now what happens?



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Re: Cars jumping 1 lane only

Post by gpraceman » Thu Feb 28, 2019 3:19 pm

Speedster wrote:
Thu Feb 28, 2019 3:11 pm
Just for Fun, pull the section out and turn it around. Now what happens?
The joiner alignment pins would be an issue with trying that.

Once sections are fine tuned, the track should always be assembled with the sections in the exact same order. Really just and issue for the middle straightaway sections.


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Re: Cars jumping 1 lane only

Post by Speedster » Thu Feb 28, 2019 4:12 pm

Yep, he'd need to knock the pins out. It's interesting that something that can cause a car to jump the track and yet happen in only one lane. I wonder if a single Burr didn't get corrected.



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gpraceman
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Re: Cars jumping 1 lane only

Post by gpraceman » Thu Feb 28, 2019 6:09 pm

Speedster wrote:
Thu Feb 28, 2019 4:12 pm
Yep, he'd need to knock the pins out. It's interesting that something that can cause a car to jump the track and yet happen in only one lane. I wonder if a single Burr didn't get corrected.
It's not so surprising to me. After tuning several of these tracks for Ford and Subaru races, there can be burrs that are the issue or even the extrusions can be bent ever so slightly convex or concave at the section ends. See http://www.derbytalk.com/viewtopic.php?t=6109


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Awana Grand Prix and Pinewood Derby racing - Where a child, an adult and a small block of wood combine for a lot of fun and memories.

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