Rail Riding - "How To Guide"

Secrets, tips, tools, design considerations, materials, the "science" behind it all, and other topics related to building the cars and semi-trucks.
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Have you had success with a "rail rider"?

Yes
93
50%
No
8
4%
Somewhat
12
6%
Haven't tried yet
73
39%
 
Total votes: 186

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Pinewood Daddy
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Re: Rail Riding - "How To Guide"

Post by Pinewood Daddy »

Stan Pope wrote:
mbb wrote:Thats how we do it mostly. axles are not round, they are oval as you approach head. so turning producess effects
Which part of the axle touches the wheel bore with the most force as the car sits at the starting gate?
... as the car is rolling a few inches past the gate?
... as the car rolls on the flat?

Not always the same, right? Maybe 30 degrees around the axle?

Does that mean that the car steers differently on the slope than on the flat?

Can you make use of that difference? Or does the difference hurt you?
OHHH!!!! THERE GOES THAT PAIN AGAIN!!! :shock: :shock: :shock:

As usual, great questions raised Stan!! More to think about!!!

Could that have something to do about our cars always being slow on the ramp and "accelerating" on the flat?? Possible increased steering into the rail on the ramp, since the alignment is done on a flat surface and higher speed testing is only done with a 5° (?) slope. I'm sure there are many other factors (too many!!) but that's something else to think about!
Grubartez
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Re: Rail Riding - "How To Guide"

Post by Grubartez »

I run 2.5 degrees negative cant on the rears and 1 degree positive on the front. All the axle holes are drilled at these various degrees. The front axle then has a very slight bend (0.5 degree maybe) to give me a little steer adjustability. When I stage the car, both rear wheels are centered to the rail and pulled to the axle heads. The FDW is staged 1/32" or closer to the rail and also pulled to the axle head.

Now when the pin is dropped (Best Track), does the positive canted wheel actually go in towards the body and rub until enough force or speed is obtained to push it out to the axle head? I have noticed that the closer I stage the FDW to the rail, the faster and more stable the cars run.

Makes you think, doesn't it?
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sporty
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Re: Rail Riding - "How To Guide"

Post by sporty »

Oval axles !!

:roll:
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Pinewood Daddy
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Re: Rail Riding - "How To Guide"

Post by Pinewood Daddy »

sporty wrote:Oval axles !!

:roll:
Exactly!!
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sporty
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Re: Rail Riding - "How To Guide"

Post by sporty »

I'm guessing what he was trying to say, is that the head of the axle can be out of round on the inside and the edge of the axle shaft that connects to the axle head.

I have seen this alot, they need work, out of the box.

But It also appeared by the post to mean that you should oval shape the axle to reduce contact with the wheel ?
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Pinewood Daddy
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Re: Rail Riding - "How To Guide"

Post by Pinewood Daddy »

sporty wrote:I'm guessing what he was trying to say, is that the head of the axle can be out of round on the inside and the edge of the axle shaft that connects to the axle head.

I have seen this alot, they need work, out of the box.
Yes, definitely! we do alot of filing of the shaft near the head with a diamond file.
sporty wrote:But It also appeared by the post to mean that you should oval shape the axle to reduce contact with the wheel ?
The axle shaft itself is not round, it's oval. So depending where the wheel bore contacts the axle surface, the alignment can be greatly affected, such as when the car is on the 30 degree ramp contact area is shifted 30 degrees back on the axles.
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sporty
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Re: Rail Riding - "How To Guide"

Post by sporty »

It is round, when I get done with them. :lol:

so you are saying, to oval them more ?

I have never done it, and right now in our local area we are the fastest and been the leader in pinewood derby cars and speed for the past three years.

We also won 2008 1st & 2nd at council, which adds to be about out of 2600 kids. 2007 a 3rd place at council.

So I would really have to do some testing to see if it got us any faster.

We are certainly at that point, where finding more speed is very hard.

And i'm sorry for get off topic in the how to guide. as this all likely is outside of rail riding.
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Pinewood Daddy
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Re: Rail Riding - "How To Guide"

Post by Pinewood Daddy »

Oval is bad!!! It can mess with your alignment on the slope. I wish we could use aftermarket machined axles. Then there would be a few less variables.
quadad
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Re: Rail Riding - "How To Guide"

Post by quadad »

I have only looked at our axles at modest magnification, and was usually looking for the burrs to be removed cleanly, etc., so I haven't noticed how oval the axles are. Is it accepted that by the time you sand them round, you have shrunk the OD too much ? That would go against Sporty's fine record. It seems you need 25-30 degreees of smooth area, and ideally would like to start on one edge - but, that control is not available if you are twisting the axles to get the alignment correct.
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Re: Rail Riding - "How To Guide"

Post by DerbyDoDo »

If someone were to use some speed prepped axles, they are probably more round than oval. So I imagine for those you would need to add a slight bend to them.
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Re: Rail Riding - "How To Guide"

Post by BlackLotus »

I'm putting this link here because it realy helped me understand the alignment for RR.

http://www.youtube.com/watch?v=9H96uufnygk
DerbyDoDo
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Re: Rail Riding - "How To Guide"

Post by DerbyDoDo »

That's a really good video. I had done so much reading on here and found many people said not to cant the rear wheels any. But I think it would actually help more since less will be touching the track.
BlackLotus
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Re: Rail Riding - "How To Guide"

Post by BlackLotus »

I don't have the ability to test if the car would have been faster without the canted rears, but we followed the video to the letter, had the car aligned in under an hour and had wonderful results at the derby.
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Re: Rail Riding - "How To Guide"

Post by DerbyDoDo »

Yeah, after watching that video, I'm thinking of canting the rear wheels now!
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Re: Rail Riding - "How To Guide"

Post by Fatdaddy »

OK, so this year was our first with a rail rider. Won the pack, fairly easily, now on to district. My question is, why run the car in forward and reverse when testing the alignment of the rear wheels? The car will only be travelling forward, if the wheels stay to the axle head, there shouldnt be a need to adjust, right? What does the running in reverse actually do for you? It's probably an easy answer, but I was curious about it.
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