Rail Riding - "How To Guide"

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Have you had success with a "rail rider"?

Yes
90
49%
No
8
4%
Somewhat
12
7%
Haven't tried yet
72
40%
 
Total votes: 182

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woodworx
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Re: Rail Riding - "How To Guide"

Post by woodworx » Fri Mar 13, 2009 8:03 pm

If the wheels migrate to the body in reverse that means your rears are toed out and visa versa the other way around. If the wheels dont change forward or reverse then they are running straight. Now when you throw canted axles in the mix checking this becomes a challenge.



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Re: Rail Riding - "How To Guide"

Post by Fatdaddy » Fri Mar 13, 2009 9:41 pm

woodworx wrote:If the wheels migrate to the body in reverse that means your rears are toed out and visa versa the other way around. If the wheels dont change forward or reverse then they are running straight. Now when you throw canted axles in the mix checking this becomes a challenge.
Ok, that make sense. Could you not determine the same thing by holding the car on it's side and seeing if one side of the wheel is closer to the body than the other? I realize that only goes so far, as minute toe would be very difficult to detect that way, but if the car tracks well, and the wheels migrate forward, it seems like extra stress to try and get it to do the same backward. Perhaps I'm oversimplifying, I guess I'm just thirsty for knowledge tonight :)

Thanks for the info woodworx, I appreciate it!



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Stan Pope
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Re: Rail Riding - "How To Guide"

Post by Stan Pope » Fri Mar 13, 2009 9:55 pm

Fatdaddy wrote:Could you not determine the same thing by holding the car on it's side and seeing if one side of the wheel is closer to the body than the other?
Keep in mind that late steps in alignment are correcting errors of much less than half a degree! You are down in the range in which direct visual measurement doesn't cut it. What you get for the alignment effort is near elimination of "pinching between friction surfaces" that otherwise act as brakes. The "pinching" happens when the rear wheels follow paths that are not parallel.


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Re: Rail Riding - "How To Guide"

Post by Fatdaddy » Fri Mar 13, 2009 10:02 pm

Stan Pope wrote:
Fatdaddy wrote:Could you not determine the same thing by holding the car on it's side and seeing if one side of the wheel is closer to the body than the other?
Keep in mind that late steps in alignment are correcting errors of much less than half a degree! You are down in the range in which direct visual measurement doesn't cut it. What you get for the alignment effort is near elimination of "pinching between friction surfaces" that otherwise act as brakes. The "pinching" happens when the rear wheels follow paths that are not parallel.
Thank you Stan, that's what I was hoping for. MAkes sense, that's kind of what I figured.



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Re: Rail Riding - "How To Guide"

Post by Ten Thumb Tom » Sun Dec 27, 2009 5:31 am

I saw a rail rider that the RR wheel (the raised wheel) had been glued so it did not turn. What would be the advantages or disadvantages of this? Was this a derby-meister or a derby-dufus? :thinking:

I could not find an answer to this, so apologies in advance if I missed it.



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Re: Rail Riding - "How To Guide"

Post by Pinewood Daddy » Sun Dec 27, 2009 9:42 am

I wouldn't worry about it. When done correctly the raised wheel should never contact the rail.



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Re: Rail Riding - "How To Guide"

Post by Ten Thumb Tom » Sun Dec 27, 2009 2:38 pm

Thank you Pinewood Daddy, but I'm kind of the answer guy for the pack and I'm supposed to come up with an actual scientific response. So what would be the advantages or disadvantages of gluing the raised wheel on a rail rider so it doesn't turn?



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Re: Rail Riding - "How To Guide"

Post by Stan Pope » Sun Dec 27, 2009 2:46 pm

Ten Thumb Tom wrote:Thank you Pinewood Daddy, but I'm kind of the answer guy for the pack and I'm supposed to come up with an actual scientific response. So what would be the advantages or disadvantages of gluing the raised wheel on a rail rider so it doesn't turn?
Assuming that the raised wheel will never(!) touch the track or rail, you can analyze it by thinking about how you would attach it somewhere else, for instance, on top. Would you leave it loose to rattle around? Or would you lock it down?

If it rattled around, then it would be sinking energy that ought to go into your car's speed!

Is that what you had in mind for "scientific?"


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Re: Rail Riding - "How To Guide"

Post by sporty » Sun Dec 27, 2009 3:01 pm

Preventing vibration and osilation are the only real advantages I see to doing it.


Never heard of a cub scout pack allowing them to glue a wheel so it does not turn. Sounds like a real interesting committee discussion.

Is the pack very competitive ?


Not sure I would wanna do it, unless a test track and lots of time to dial it in, to ensure the wheel never touches the rail to slow you down.

I think it would have to be raised pretty high, to not risk being effected by the sudden down force at the start gate going down the slope of the track. Then a risk at transisition to the flat. must be a darn good track, to not worry of rug to the rail.

I see more cons than pros with with doing it. Someone doing it, likely is pretty savy with a test track and RR. Don't see many other scouts at the same pack doing it. Unless they all got access to a test track and timer and time to dial it in well.

Whats the real debate with the pack ? allowing it or excluding it ? i'd allow it. If they are that fast and good, not gonna much matter what they do !
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Re: Rail Riding - "How To Guide"

Post by Ten Thumb Tom » Sun Dec 27, 2009 11:08 pm

Unfortunately, this took place before my watch and I did not see the car; it has only been described to me. At this time, my goal is to make certain that I understand the physics that would take place rather than pass judgement on the practice - and your insights are very helpful.
Stan Pope wrote:Assuming that the raised wheel will never(!) touch the track or rail, you can analyze it by thinking about how you would attach it somewhere else, for instance, on top. Would you leave it loose to rattle around? Or would you lock it down?
sporty wrote:Preventing vibration and osilation are the only real advantages I see to doing it... Not sure I would wanna do it, unless a test track and lots of time to dial it in, to ensure the wheel never touches the rail to slow you down.
If I understand correctly, the scenario you are both describing is a car that is not a rail rider, but a three wheeler with alignment so dead on that the raised wheel would not touch the rail, and that under these conditions, the car could benefit from less vibration by gluing the wheel down rather than allowing it to rattle.

I suspect the situation was more likely one of the following; 1) a car that is dead on alignment, but the raised wheel occasionally touches the track and 2) a car that is a rail rider with the alignment such that the raised wheel lightly touches the rail.

Has anyone ever testing the impact to friction and enertia of a fixed raised wheel versus a free-wheeling? Could the motive have been to force the angle of attack of the raised wheel to touch the rail with only the front edge of the wheel and to prevent the wheel from "pancaking" against the rail with both the front and rear edge? If so, would this generate a positive result, or just bad science?



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Re: Rail Riding - "How To Guide"

Post by Stan Pope » Mon Dec 28, 2009 12:49 am

Ten Thumb Tom wrote: If I understand correctly, the scenario you are both describing is a car that is not a rail rider, but a three wheeler with alignment so dead on that the raised wheel would not touch the rail, and that under these conditions, the car could benefit from less vibration by gluing the wheel down rather than allowing it to rattle.
No, the car is almost certainly a 3-wheel RR with the dominant front wheel (DFW) toed in a bit to keep it against the rail. Dead-on alignment will almost always touch both sides of the rail somewhere along the run down the track.

Since the DFW is lightly loaded (almost always carrying less than one ounce), the friction losses from it rubbing are small. If you add a bit of positive camber to the DFW so that it touches below the top edge of the rail, the situation may even be better ... it will be rolling on both the track and the side of the rail, though there is also some sliding on the rail.

The value of glueing the wheel down is probably very slight. It was probably done to "show off."

If the DFW were sufficiently lightly loaded and if the car's inclination to "run to the rail" could be controlled through the rear wheels' differential friction, then you could probably get by with glueing in both front wheels and letting the DFW slide down the track. But that would take a whole bunch of tuning to get it right and fast. And, it would be showing off. Don't think we really need that. :(


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Ten Thumb Tom
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Re: Rail Riding - "How To Guide"

Post by Ten Thumb Tom » Fri Jan 01, 2010 2:54 pm

Okay, let me see if I've got this straight :thinking:
Assuming a theortical situation where there are no adjustments necessary for imperfections in wheels, axles, axle holes, etc, the alignment goals for a rail rider would look something like this...

REAR WHEELS
- negative camber
- zero toe

FRONT RAISED WHEEL
Option 1
- zero camber
- slight toe in (to minimize spin-up should the raised wheel come into contact with the center guide).
Option 2
- negative camber (to give it a little extra clearance).
- zero toe

FRONT DOMINANT WHEEL (DFW) -
- slight positive camber (so that the inner edge of the tread rolls against the rail as the outer edge rolls against the track).
- slight toe in (so that the DFW will steer lightly into the center guide).
- the light weight load on the DFW allows the light force of turning into the center guide to push the wheel slightly down the axle enough so that the wheel is not touching the car body.

WHEREAS CAMBER and TOE are defined as:
Image Image
Last edited by Ten Thumb Tom on Sat Jan 02, 2010 9:48 am, edited 5 times in total.



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Re: Rail Riding - "How To Guide"

Post by Pinewood Daddy » Fri Jan 01, 2010 3:20 pm

Ten Thumb Tom wrote:If so, how can a wheel have positive camber and not rub against the car body (the DFW in the description above)? Or it is the expectation that the force of turning into the center guide is sufficient to push the wheel slightly down the axle enough so that the wheel is not touching the car body? Of is it that the weight load on the DFW is light enough that it is not a concern? Or is it the EPR Paradox in quantum physics with all possible outcomes occurring in alternate universes at the same time? ...wait, scratch that last one, I think that was a Star Trek episode.
Your assumptions are correct.

We put negative camber on the raised wheel just to give it a little extra clearance, and no toe in.



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Re: Rail Riding - "How To Guide"

Post by Ten Thumb Tom » Fri Jan 01, 2010 3:36 pm

Pinewood Daddy wrote: Your assumptions are correct. We put negative camber on the raised wheel just to give it a little extra clearance, and no toe in.
Thank you P-Daddy! I updated the list with that option.



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Re: Rail Riding - "How To Guide"

Post by asatxj » Thu Feb 04, 2010 5:45 am

:thinking: A stock Awana wheel has about 1.5 degrees of positive camber built into it. The inside diameter of the tread is larger than the outside. In absence of a Lathe or the funds to buy MaxV's wheels ($30+) attempting to get positive camber in the front one must put approximately 3 degrees of bend in the axle. This could make alignment a very challenging operation. I will be doing one car with zero camber on the DFW this year, I could try the 3 degrees on the other. Has anyone tried it?


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