Cars jumping 1 lane only

General topics of interest to racers and race coordinators alike.
Post Reply
jimsz
Apprentice
Apprentice
Posts: 3
Joined: Thu Feb 12, 2009 11:33 am
Location: Western, New York

Cars jumping 1 lane only

Post by jimsz »

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.
User avatar
Vitamin K
Pine Head Legend
Pine Head Legend
Posts: 1246
Joined: Sat Apr 20, 2013 7:26 pm
Location: Spotsylvania, VA

Re: Cars jumping 1 lane only

Post by Vitamin K »

jimsz wrote: Thu Feb 28, 2019 8:43 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
Apprentice
Apprentice
Posts: 3
Joined: Thu Feb 12, 2009 11:33 am
Location: Western, New York

Re: Cars jumping 1 lane only

Post by jimsz »

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.
User avatar
Darin McGrew
Pine Head Legend
Pine Head Legend
Posts: 1825
Joined: Fri Jul 18, 2003 1:23 pm
Location: Knoxville, TN
Contact:

Re: Cars jumping 1 lane only

Post by Darin McGrew »

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.
User avatar
gpraceman
Site Admin
Site Admin
Posts: 4926
Joined: Fri Jun 20, 2003 12:46 am
Location: Highlands Ranch, CO
Contact:

Re: Cars jumping 1 lane only

Post by gpraceman »

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.
Randy Lisano
Romans 5:8

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.
jimsz
Apprentice
Apprentice
Posts: 3
Joined: Thu Feb 12, 2009 11:33 am
Location: Western, New York

Re: Cars jumping 1 lane only

Post by jimsz »

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

We will be webcasting our derby live via facebook - March 5th, 7pm. https://www.2047.org
Speedster
Pine Head Legend
Pine Head Legend
Posts: 1972
Joined: Sat Feb 18, 2012 1:48 pm
Location: Toledo, Ohio

Re: Cars jumping 1 lane only

Post by Speedster »

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?
User avatar
gpraceman
Site Admin
Site Admin
Posts: 4926
Joined: Fri Jun 20, 2003 12:46 am
Location: Highlands Ranch, CO
Contact:

Re: Cars jumping 1 lane only

Post by gpraceman »

Speedster wrote: Thu Feb 28, 2019 2:11 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.
Randy Lisano
Romans 5:8

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.
Speedster
Pine Head Legend
Pine Head Legend
Posts: 1972
Joined: Sat Feb 18, 2012 1:48 pm
Location: Toledo, Ohio

Re: Cars jumping 1 lane only

Post by Speedster »

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.
User avatar
gpraceman
Site Admin
Site Admin
Posts: 4926
Joined: Fri Jun 20, 2003 12:46 am
Location: Highlands Ranch, CO
Contact:

Re: Cars jumping 1 lane only

Post by gpraceman »

Speedster wrote: Thu Feb 28, 2019 3:12 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
Randy Lisano
Romans 5:8

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.
Post Reply