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.

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

*5 J's*
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Re: Rail Riding - "How To Guide"

Post by *5 J's* » Wed Apr 06, 2011 12:28 pm

derbyspeed wrote: Can't tell you how to get a 1.5 or 2.5 bend, I just bend the axle enough to see the bend, someone else might be able to chime in and explain better how to get the 1.5 or 2.5 degree bend.
I'm sure there are better ways, but when I started making RR and wasn't sure what a 3 degree bend would look like, I made two parallel line in Microsoft word, then rotated one 3 degrees, making 3 degree angle. I printed this out, then once I bent an axle I would compare the axle to the printed angle. It is not critical to have exactly 3 degrees or exactly 1.5 degrees, I would however make sure that the rears have the same angle.



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Re: Rail Riding - "How To Guide"

Post by derbyspeed » Wed Apr 06, 2011 12:35 pm

*5 J's* wrote:
derbyspeed wrote: Can't tell you how to get a 1.5 or 2.5 bend, I just bend the axle enough to see the bend, someone else might be able to chime in and explain better how to get the 1.5 or 2.5 degree bend.
I'm sure there are better ways, but when I started making RR and wasn't sure what a 3 degree bend would look like, I made two parallel line in Microsoft word, then rotated one 3 degrees, making 3 degree angle. I printed this out, then once I bent an axle I would compare the axle to the printed angle. It is not critical to have exactly 3 degrees or exactly 1.5 degrees, I would however make sure that the rears have the same angle.
Excellent 5 J's! I ordered a pre-bent axle and have used that as a guide, never thought of using Word to check the angle. I agree that it's not all that critical on the degrees.


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Re: Rail Riding - "How To Guide"

Post by *5 J's* » Wed Apr 06, 2011 12:38 pm

Ynot wrote:I managed to locate both the Rail Rider and Axel Press by DW a few cities away, so I'm in luck.

My body is already 1 11/16, a 1/16 less than normal already. Will the additional 1/16, then 1/8 be to tight for the track?

Tony

Edit: *5 J's*, just saw your post.
Is the entire side 1/16" narrower? You want the DFW to be inset 1/16" to 1/8" relative to the REAR wheel directly behind it. This is what keeps the rears off the rail. If the entire body is narrower you don't have the required offset to keep the rear off the rail.



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Re: Rail Riding - "How To Guide"

Post by *5 J's* » Wed Apr 06, 2011 12:42 pm

derbyspeed wrote:Excellent 5 J's! I ordered a pre-bent axle and have used that as a guide, never thought of using Word to check the angle. I agree that it's not all that critical on the degrees.
Eventually I ordered a set of grooved axles, one bent, for a league car. I do use this axle as my gauge now, but the printed angle produced many first place cars. :D



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Re: Rail Riding - "How To Guide"

Post by Ynot » Wed Apr 06, 2011 1:51 pm

s the entire side 1/16" narrower? You want the DFW to be inset 1/16" to 1/8" relative to the REAR wheel directly behind it. This is what keeps the rears off the rail. If the entire body is narrower you don't have the required offset to keep the rear off the rail.
Yes, the entire side is already 1/16 narrower. I had to cut my own block and all I had at the time was just shy of an official size BSA block. Sorry to throw this out there, but what did I know at the time? Start over or continue on?



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Re: Rail Riding - "How To Guide"

Post by Stan Pope » Wed Apr 06, 2011 2:08 pm

Ynot wrote:Yes, the entire side is already 1/16 narrower. I had to cut my own block and all I had at the time was just shy of an official size BSA block. Sorry to throw this out there, but what did I know at the time? Start over or continue on?
Do something to get the rear wheel behind the DFW outside the DFW by 1/16 to 1/8". For instance, glue a small section of popcycle stick (or other wood) across that rear axle hole! (If there is already a drilled axle hole, drill the add-on first, then align the two holes with a spare axle as you apply glue and press the add-on against the body.)

You could simply extend the rear axle an extra 1/16", but most folks like to keep the hub-body clearance small.

You could force an offset by careful alignment of the rear axles, but the rear is narrow which makes the adjustment more critical.


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Re: Rail Riding - "How To Guide"

Post by Ynot » Wed Apr 06, 2011 2:51 pm

Stan,
Thanks for the fix. I had some scraps that were perfect for this. Glued and waiting.

Tony



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Re: Rail Riding - "How To Guide"

Post by Ynot » Wed Apr 06, 2011 6:12 pm

My body is dry and awaiting paint prep.The rear end is now 1.75", the front end I left alone and still less a 1/16. DFW is Left.

Meanwhile in the axle dept. I've been flashing and straightening. Can I put a groove in the axle for less contact surface and to allow for graphite or is this no longer a good idea. I saw this in Meades book. I've also seen multiple grooves per axle somewhere online. Is this better or worse? Should this practice not be combined with cantering for any reason?



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Re: Rail Riding - "How To Guide"

Post by *5 J's* » Thu Apr 07, 2011 5:30 am

Ynot wrote:My body is dry and awaiting paint prep.The rear end is now 1.75", the front end I left alone and still less a 1/16. DFW is Left.

Meanwhile in the axle dept. I've been flashing and straightening. Can I put a groove in the axle for less contact surface and to allow for graphite or is this no longer a good idea. I saw this in Meades book. I've also seen multiple grooves per axle somewhere online. Is this better or worse? Should this practice not be combined with cantering for any reason?
We are not allowed to grooved axled in our Pack so I have no experience with grooved axles and graphite. I would say if grooves provide an advantage it would be quite small and the risk for messing up the surface is too great of a risk. I would not do it.

In league racing I use Krytox oil and groove these axles - but I can tell you from experience it's real easy to mess up a good axle, and once grooved you have to be REAL careful to not bend an axle. A slight unintentional bend and you will lose any benefit gained from the grooves.

My two cents anyway...



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Re: Rail Riding - "How To Guide"

Post by Ynot » Thu Apr 07, 2011 6:50 am

Makes sense. Thanks



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Re: Rail Riding - "How To Guide"

Post by Duane » Thu Apr 07, 2011 9:31 am

*5 J's* wrote:
Ynot wrote:Can I put a groove in the axle for less contact surface and to allow for graphite or is this no longer a good idea. I saw this in Meades book. I've also seen multiple grooves per axle somewhere online. Is this better or worse?
We are not allowed to grooved axled in our Pack so I have no experience with grooved axles and graphite. I would say if grooves provide an advantage it would be quite small and the risk for messing up the surface is too great of a risk. I would not do it.

In league racing I use Krytox oil and groove these axles - but I can tell you from experience it's real easy to mess up a good axle, and once grooved you have to be REAL careful to not bend an axle. A slight unintentional bend and you will lose any benefit gained from the grooves. My two cents anyway...
According to Dr Jobe and other experts on the physics of these cars, total friction does not go up or down when the size of the instantaneous contact area is increased or decreased; the total friction stays contact. So there is no direct beneficial effect, contrary to intuition. The effect (if any) is indirect and secondary, from how it affects lubrication over time.

If the groove has sharp, right-angled shoulders, those edges could scratch the soft plastic of the wheel bore and mess things up badly.
If the groove has broad gently-sloped shoulders, that means that some of the active touching axle surface has a different diameter than the rest, which could add a kind of internal canting that you don't want; it changes as the wheel migrates left and right across the axle.
The groove makes it hard to do an even job of polishing the axle after cutting the groove; the shoulders will get eroded more during polishing.
Grooving could also send the wheel inward where it rubs continuously against the car body, or outward where it rubs continuously against the nail head.

If grooving is (sometimes) beneficial, I guess it is from leaving a thin ring of unwiped surface on the inside of the wheel bore. Loose graphite flakes can hide there until accidentally redistributed by the car handlers between races, or redistributed by left/right wheel wanderings during a race. But excess loose graphite is not good in the early races; what you want is worked-in graphite smoothly covering all friction surfaces (the entire bore, and the bottom edge of the axle).

In the past, I've re-applied graphite just before check-in, by dabbing in graphite with a small watercolor paint brush and then spinning the wheels manually while holding the car upright, and then knocking off the excess. I'm now thinking that it would be better to hold the car upside down while doing that manual spinning, so that the bores are rubbing against the same side of the axle that will be facing towards the track and bore during racing.



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Re: Rail Riding - "How To Guide"

Post by *5 J's* » Thu Apr 07, 2011 9:55 am

Duane wrote:According to Dr Jobe and other experts on the physics of these cars, total friction does not go up or down when the size of the instantaneous contact area is increased or decreased; the total friction stays contact. So there is no direct beneficial effect, contrary to intuition. The effect (if any) is indirect and secondary, from how it affects lubrication over time.
Perhaps many smarter then I, Dr Jobe included, have concluded that science dictates that grooves provide no direct beneficial effect - but I can tell you that real world application proves grooved axles are faster when using oil. I'll leave it to the experts to figure out the why.



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Re: Rail Riding - "How To Guide"

Post by derbyspeed » Thu Apr 07, 2011 11:08 am

*5 J's* wrote:Perhaps many smarter then I, Dr Jobe included, have concluded that science dictates that grooves provide no direct beneficial effect - but I can tell you that real world application proves grooved axles are faster when using oil. I'll leave it to the experts to figure out the why.
5 J's I would have to agree with you, it seems real world application is the final law of the land, if it works it doesn't matter if science agrees or not. Compare grooved axles with thinner wheels, if the theory on grooved axles doesn't allow for a faster car then why would a thinner (meaning not as wide) wheel make the car faster - both have the same load but distributed in a smaller area. Or maybe I'm in left field on this one. :scratching:


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Re: Rail Riding - "How To Guide"

Post by Duane » Thu Apr 07, 2011 1:32 pm

derbyspeed wrote: if it works it doesn't matter if science agrees or not.
Yes. Better said as 'if it works, it doesn't matter if theories agree or not'. Science is more about the repeatable experiments than the theories. The theories are added, just to have some way to predict the results of the experiments, and maybe understand them too.
if the theory on grooved axles doesn't allow for a faster car then why would a thinner (meaning not as wide) wheel make the car faster - both have the same load but distributed in a smaller area. Or maybe I'm in left field on this one. :scratching:
Good question!

If the wide and thin wheels have identical outer diameters, bore diameters, total weight, moment of inertia, and axles, then it is fair to compare them for wide vs thin effects.

The thin wheel will have significantly less wind resistance than the fat wheel. In the sleek slab cars with standard BSA wheels, the wheels give over twice as much wind resistance than does the body of the car. Using thin wheels, their total wind resistance is less than that of the thinnest car body.

The tread edge and sidewall profile of BSA wheels are not ideal for gliding along the guide rail with minimal friction and minimal steering-correction bounces.

People have gotten faster results with BSA wheels when they lathe the tread surface into an H or V profile so that the track contact is on just a thin edge of plastic rather than the full width of the tread. Meade says this helps by reducing inertia of the wheel, and by reducing friction by reducing contact area. But the area-doesn't-count theory claims that reducing contact area doesn't reduce friction directly. And yet it helps!

I've read elsewhere, people's theories that narrowed wheel-to-track contacts help by avoiding most of the hard-to-see bumps of the track surface. If the car has wide wheel treads with full contact, it will get jolted upwards by running over any hairs or other junk particles on the track surface, within the tread footprint. Each jolt causes some diversion & loss of kinetic energy. Also, the junk can stick to the wheel and cause jolts for every revolution thereafter. If the wheels have narrowed ridges of track contact, there is much less of the track surface that can affect the wheel and fewer pieces of junk will be rolled over or acquired. These differences are hard to see but can be heard.

One advantage of canting wheels is that the wheel touches on just one edge, not the full tread width, giving the same benefit of steering around most junk without carving the wheel itself.

For axle-to-wheelbore contact, the analogous thing would be if the wheel bore had scratches or lumps in only one spot, and the sculpted (grooved) axle avoided that spot. But it is easier to polish the bores and axles to ideal cylinders than to leave bumps and avoid them by luck.

You could also imagine if the grooved-axle methods & materials were applied to the wheel/track contact. What if our tracks were made of soft plastic, and our wheels were made of knife-edged metal? How many races would it take, until the track was permanently damaged by scratches? Would graphite or thin oil help much with all those scratches?



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Re: Rail Riding - "How To Guide"

Post by derbyspeed » Thu Apr 07, 2011 1:57 pm

I would think (for what it's worth) that when you polish a grooved axle that you are also going to polish that edge as well, whether you are trying to or not, therefore the bore would ride smoothly or possibly not at all on that edge, depending on where you put the groove - persay in a position where the groove would be in the middle of the bore and the wheel would ride on both sides of the groove.

This would be of course if you had canted wheels and were able to pull the wheels out at the starting line, otherwise some in and out movement may cause some scarring, but I would think it would be minimal.


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