Ride ON rail?

Secrets, tips, tools, design considerations, materials, the "science" behind it all, and other topics related to building the cars and semi-trucks.
Post Reply
tjeffrey
Journeyman
Journeyman
Posts: 46
Joined: Wed Mar 11, 2009 7:45 pm
Location: La Grange, IL

Ride ON rail?

Post by tjeffrey »

We just completed our Indian Guides derby and it was run on a 49ft BestTrack. We had set up our cars as RR cars. It struck me after the event that the center rails on the BestTrack would actually allow you to build a grooved or notched wheel that could run ON TOP of the center rail. Our rules don't prevent such a thing. I'm curious if anyone has ever tried this idea?

It seems like a way to keep a straight alignment down the track without any friction loss of the RR wheel rubbing the side of the center rail. Thoughts?
User avatar
gpraceman
Site Admin
Site Admin
Posts: 4926
Joined: Fri Jun 20, 2003 12:46 am
Location: Highlands Ranch, CO
Contact:

Re: Ride ON rail?

Post by gpraceman »

Most rules do state a minimum distance between the wheels of 1-3/4", so that would preclude such a car. That would be interesting to see, though, if it was allowed by the rules.
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.
User avatar
Stan Pope
Pine Head Legend
Pine Head Legend
Posts: 6856
Joined: Sat Jul 05, 2003 7:01 pm
Location: Morton, Illinois
Contact:

Re: Ride ON rail?

Post by Stan Pope »

gpraceman wrote:Most rules do state a minimum distance between the wheels of 1-3/4", so that would preclude such a car.
Good observation!

I think that both front wheels could be offset 3/8" in the same direction, keeping the car within the separation rules and within the inspection box limits.

The equivalent of offsetting both front wheels is to align the rears to "dog trot", i.e. to run about 1/4 to 3/8" offset from the front.

You might run afoul a rule requiring a "flat tread". In that case, you would have to combine two front wheels to make a "V" over the ridge of the rail.
Stan
"If it's not for the boys, it's for the birds!"
tjeffrey
Journeyman
Journeyman
Posts: 46
Joined: Wed Mar 11, 2009 7:45 pm
Location: La Grange, IL

Re: Ride ON rail?

Post by tjeffrey »

Our rules are very wide open. No minimum distance, just a max width, length, and weight. No rule against groved wheels, just need to use the kit wheels.
User avatar
gpraceman
Site Admin
Site Admin
Posts: 4926
Joined: Fri Jun 20, 2003 12:46 am
Location: Highlands Ranch, CO
Contact:

Re: Ride ON rail?

Post by gpraceman »

tjeffrey wrote:Our rules are very wide open. No minimum distance, just a max width, length, and weight. No rule against groved wheels, just need to use the kit wheels.
If that is the case, then it would be cool to give that idea a try.

Any wheel that rides the rail should have a rather deep V or H shape so as to help it stay on the rail.

My concern on riding on top of the rail would be how well the tops of the rails line up section to section. Any little bump may cause your car to derail. Maybe just have the front wheels ride on the rail, to minimize the risk of the car jumping out of its lane and interfering with other cars.
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.
tjeffrey
Journeyman
Journeyman
Posts: 46
Joined: Wed Mar 11, 2009 7:45 pm
Location: La Grange, IL

Re: Ride ON rail?

Post by tjeffrey »

That was my thinking. Just one, or both front wheels. Leave the back on the track.

You make a good point about the joints. I don't know how rough those may be and if it would cause the car to jump off.

Do you think the benefit of a straight run on the rails would outweigh having the 4th wheel versus a 3 wheel RR.
User avatar
gpraceman
Site Admin
Site Admin
Posts: 4926
Joined: Fri Jun 20, 2003 12:46 am
Location: Highlands Ranch, CO
Contact:

Re: Ride ON rail?

Post by gpraceman »

tjeffrey wrote:Do you think the benefit of a straight run on the rails would outweigh having the 4th wheel versus a 3 wheel RR.
Unless, the tops of the rails transition smoothly section to section, I would think you would get better performance with a 3 wheel RR car. Typically, people worry about how smoothly the normal wheel running surface and the outsides of the rails are from section to section and likely don't worry about the tops of the rails.

Still, that would be cool to give your idea a try. You just may have to bring a file or honing stone to dress up the top rails (if the race coordinator will let you do that).
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.
Davhamm
Pine Head
Pine Head
Posts: 85
Joined: Tue Mar 13, 2007 9:38 pm
Location: Novi, MI

Re: Ride ON rail?

Post by Davhamm »

Lets take this a step further. What if you make a 3 or 4 wheeler for this plan it wont matter.

Lets add a 5th wheel of somekind somewhat in the middle of the car at a large camber. This "Wheels" tread is at the height of the rail sitting between the rails. Race start car tracks side ways (hard?) middle wheel hits rail, car raises slightly and is now riding on 3 wheels, 2 back and this middle wheel. Could even put this middle wheel forward, since its not part of the wheelbase at check in.

Pushing the rules here in everydirection. wonder if this would work?
tjeffrey
Journeyman
Journeyman
Posts: 46
Joined: Wed Mar 11, 2009 7:45 pm
Location: La Grange, IL

Re: Ride ON rail?

Post by tjeffrey »

Interesting twist! You may not need to have the fifth wheel, just put the fourth in the middle position you described and push the car in that direction.

Let's face it, everyone agrees that a straight run down the track would be the fastest. We compromise with a RR because it limits side to side and bumps against the rail, but we intentionally add friction all the way down the track.

I've set up a low angle test track with a couple aluminum saw guides to simulate a BestTrack rail. It's only 8 feet, but it gives an idea of what's happening. At the low angle the run is anywhere from 4.5 - 6.0 seconds depending on the cars tested. I've set up one car to run as a 3 wheel RR. When I run it as a RR is avg. 5.90 per run. The same car I replace the DFW with a V grooved wheel and run it on top of the center rail. The same car is now averaging 5.45.

I've not spent any time trying to graphite the side of the wheel or improve the 'rub' against the center rail which would surely reduce the RR time. But the test does demonstrate the idea - Stop rubbing the rail and go straight down the track!
Davhamm
Pine Head
Pine Head
Posts: 85
Joined: Tue Mar 13, 2007 9:38 pm
Location: Novi, MI

Re: Ride ON rail?

Post by Davhamm »

The reason I was suggusting add a 5th wheel (bearing?) is to get around the wheels must be 1 3/4" apart.
tjeffrey
Journeyman
Journeyman
Posts: 46
Joined: Wed Mar 11, 2009 7:45 pm
Location: La Grange, IL

Re: Ride ON rail?

Post by tjeffrey »

Got it! We don't have a minimum, just a maximum. I wasn't thinking about that constraint.
tjeffrey
Journeyman
Journeyman
Posts: 46
Joined: Wed Mar 11, 2009 7:45 pm
Location: La Grange, IL

Re: Ride ON rail?

Post by tjeffrey »

Anyone willing or able to test this idea?

I just confirmed with our race co-ordinator that it would be legal.
ScoutAndDadTeam
Journeyman
Journeyman
Posts: 39
Joined: Wed Apr 25, 2007 9:34 am
Location: North, Carolina

Re: Ride ON rail?

Post by ScoutAndDadTeam »

One of the potential problems may be the stop section. I think if the wheel spacing is narrow enough to ride on the rails wouldn't the standard stop section (like on a besttrack) not work at slowing the car down? I think it would ride on the stop strip or worse half of the car may slip down between the rails and flip over.
User avatar
pack529holycross
Master Pine Head
Master Pine Head
Posts: 555
Joined: Wed Dec 26, 2007 4:25 pm
Location: Dr. Phillips, Florida
Contact:

Re: Ride ON rail?

Post by pack529holycross »

Has anyone taken int consideration the fact that the rail wheel will lose contact during the transition if mid-mounted, or worse raise the car up if mounted outboard of either wheel?
Davhamm
Pine Head
Pine Head
Posts: 85
Joined: Tue Mar 13, 2007 9:38 pm
Location: Novi, MI

Re: Ride ON rail?

Post by Davhamm »

Dont follow your thinking on this one.

Other note. You would have to use one of the wheels as anything else other than wheels that moves (spins) might be considered a violation of the rules.

One last thought that just popped in my head. Why not just start with the "center" wheel on the top of the rail?
Post Reply