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Rail Riding - "How To Guide"

Posted: Tue Feb 13, 2007 9:18 am
by gpraceman
I thought it would be good to include a "sticky" topic (one that stays on top of all threads in the forum) on rail riding, since many people have had such great success with the technique.

Is there anyone interested in taking the info available in several of the threads here and summarizing it? Once we have that summary, it will replace this post.

Anyone up for the challenge :?:

Re: Rail Riding - "How To Guide"

Posted: Tue Feb 13, 2007 2:06 pm
by PWD_addict
I'll start with posting Warp Speed's comments from the original "rail hugging" thread. The only credit I can take is that I was able to utilize the "search" function well. I was too new to try this with our Pack car (we won despite that) but plan to adjust it for District.
WarpSpeedINC wrote:We have found in our testing, that there is a fine line between rail hugging, and RAIL HUGGING. But the line doesn't seem to be as fine as one would think.
We try to build the rear alignment in to the car as good as we can (straight axles, rear axle slot square to car centerline, wheels as equal as possible ect..) We than have a slight bend in the front axle (.002-.003) with the bend marked. start with the bend up, then gradualy adjust to stear the needed direction. Running in the same lane, it is fairly easy to find the "sweet spot", and it seems a small adjustment either way (as long as the car doesn't come off the rail) doesn't effect speed much. We have found a LITTLE too much is a LITTLE better than not enough.
We found this during testing a couple of years ago, and have been trying to perfect it ever since. It is dependant on guide strip condition and wheel preperation, but as the older tracks get replaced with more modern (nicer) type tracks, and with better wheels and methods of modification, this becomes more effective.
As I mentioned before, you may also find this allows you to get more aggresive with other portions of car construction / set-up.
Warp Speed

Re: Rail Riding - "How To Guide"

Posted: Tue Feb 13, 2007 6:15 pm
by doct1010
Realize this may not be the summary format you sought, all I have time for at moment.

Joe started the topic with an observation:

*Looking for that last inch at the finish line...there could be an advantage to a 3-wheel car pulling ever so slightly towards the lifted wheel -- guaranteeing (almost) that the lifted wheel will not hit the guide early and cost precious time. Since it is very difficult to get even a perfectly aligned car down the track without bumping the rail -- too many uncontrolled variables I think -- why not bias the car ever so slightly towards that wheel, or is the cure worse than the disease? I only bring it up because my youngest had a very fast car at the district level and it did exactly that, maybe 1/2 to 3/4 inch off line towards the lifted wheel in six feet, one of those alignment jobs you give up on after an hour. And he beat my other boy's perfectly aligned car every time (same design, etc) What is the cost of that wheel hitting the rail early on?*

Which Warp confirmed with a :D and then added in response to a question *You want to strive for Perfect rear alignment, and Proper front alignment for track set-up and condition.
If you get this right, it may open doors for you in other areas! *

A bit from Warp on advantages: *Any time the lifted wheel touches the center guide, it has to start that wheel spinning, thus eating up energy with both having to start the wheel, and from friction of it sliding on the center strip. If it only touches the spinning wheel, you get a slight loss from the friction, and that is all.
Also, you get a slight advantage of the car going straight, instead of wandering back a forth a few times, effectivly lenghtening the path down the track.
If you look at the WIRL video's in slow motion, you can see all the fast cars moving to the guide strip soon after the pin drops.
It becomes a ballancing act, as to hard against the rail, and you loose time do to friction, not hard enough, and the car will wander, and loose this advantage.*

Joe confirms Warps' observation: * Since "perfectly" aligned cars will also oscillate because of track imperfections, it seems wise to hedge your bet towards the lifted wheel ever so slightly. Warp makes a great point, the trick is the ever so slightly. Too much and you will lose every race. If your car is dead-on aligned as a 3 -wheeler, this could account for time variations in your heats. Lane X might pull your car to the right, Lane Y might pull it to the left. If Lane Z is "perfect" than your dead-on alignment should be a rocket in that lane, provided it is staged correctly...but how would you ever know?
Hedge your bet, make sure your dominant front wheel hits first.*

Warp makes it very clear why RR is the preferred method for him: *Even if the car has "Dead On" alignment, it will never make it down the track with out touching the guide rail.
Unless the track is an ancient piece with a terrible center rail, the rail hugger will beat that car every time.
This set-up also gives the car added stabilty, so you can go more aggresive with all other aspects. *

Then goes on to explain his method *We have found in our testing, that there is a fine line between rail hugging, and RAIL HUGGING. But the line doesn't seem to be as fine as one would think.
We try to build the rear alignment in to the car as good as we can (straight axles, rear axle slot square to car centerline, wheels as equal as possible ect..) We than have a slight bend in the front axle (.002-.003) with the bend marked. start with the bend up, then gradualy adjust to stear the needed direction. Running in the same lane, it is fairly easy to find the "sweet spot", and it seems a small adjustment either way (as long as the car doesn't come off the rail) doesn't effect speed much. We have found a LITTLE too much is a LITTLE better than not enough.
We found this during testing a couple of years ago, and have been trying to perfect it ever since. It is dependant on guide strip condition and wheel preperation, but as the older tracks get replaced with more modern (nicer) type tracks, and with better wheels and methods of modification, this becomes more effective.
As I mentioned before, you may also find this allows you to get more aggresive with other portions of car construction / set-up.*

Stan, as he is apt to do, raises the bar and inquires: * The next question is whether that dominant front wheel should act in a way that keeps both rear wheels off the rail. I think that the answer is yes. One way to do that is for the dominant front wheel to be offset toward the car center by a fraction of an inch ... not a lot, but enough. The reasoning is that the light front will have a small force normal to the rail, but that the heavier rear wheels would have a larger normal force, producing more friction losses.*

Which Warp again confirms with a big :D

Stan and Warp confirm in regards to trimming body width: *take it off the body, and keep the inner hub to body a constant.*

Warp offers this cautionary caveat regarding narrowing:*One thing to mention though. During the small amount of testing I have been able to do this year, I did find that any excessive narrowing of the front tread width (more than 1/16" or so) can slow the car by making it VERY (overly) sensitive to steering adjustments. This makes it almost impossible to find the "sweet" spot during tuning, and a minute adjustment can get you into left field..... As of now, I would stay with the 1/16" dimension and you should be good!! *

Stan offers this caveat: *One critical adjustment is that the back wheels MUST be kept off the rail or run-times skyrocket. Just offsetting the front wheels is not sufficient. The rear axle alignment must cause the rear wheels to stay astraddle the rail. A bit of alignment error can cause the car to "crab" to one side or the other. You might accomplish that on a shorter test surface, but it is tough to be sure.

The next "gotcha" is that if the track has rail imperfections on the side you choose to ride, your car's lightly loaded front will try to climb right up over. The saving grace of RR is that the rail-touching wheel is very lightly loaded ... the lighter the better ... to keep the braking force very low.

It appears that the rail-touching wheel gets twisted a bit to line itself up with the rail, causing the front of the car to lift slightly. If this, in fact, happens, then you must be sure that you aren't also trying to lift the wheel on the opposite side! *

Warp on reasons to keep lifted wheel off rail: *If the lifted wheel touches, you are losing energy two fold, from having to start the wheel rotating, and then from any added friction. The spinning wheel is already turning, so the losses are only from the friction.
This is my explanation, not sure if it is the right one, but I know which way is faster!! Allot Faster!!! *

Warp comments on Stans' observation on lifted wheel: *Again, Stan put's it into the correct words!
In our eye's, the lifted wheel is there because the rules say 4 wheels, and to keep the car from crossing over the center strip, in the event alignment gets disturbed during the race, or the track is set-up not being level side to side. Otherwise, the lifted wheel doesn't exist, and is just unnecesary weight!
As Stan mentioned, the lifted wheel needs to be canted up slightly, if any. This helps ensure that it never comes in contact with the track, and in the dreadful event that it does contact the center strip, it does it only on the top edge of it. *

Joe turns another page when wondering: *Bear with me a little bit and muddle through this. When I test roll our 3-wheelers -- slowly on our track with a very slight incline (this is the only way I can visualize what is happening) when the dominant wheel contacts the rail it "grabs" for an instant and the back end slides (pivoting from the dominant wheel) on the axles through the rear wheel bores towards the lifted wheel side, then the axle head hits the rear wheel and the rear wheel(s) also slides bringing the rear wheel on the dominant side into contact with the rail. This is at very low speeds, but happens consistently.
We cannot stop the rear axles from sliding through the bores when the body pivots. Will the narrower wheelbase reduce the impact angle and stop the body from pivoting? Or do we then need extra traction on the rear wheel treads to keep the sliding and pivoting body from pulling the rear into the rail? Or as Stan suggests, does the alignment of the rear wheels also HAVE to be adjusted to prevent them from sliding?*

Critical observation by Joe regarding angle of attach on center rail: * When the dominant wheel approaches and begins to rub the rail, it "pulls" so to speak the back end of the car in the same direction until the dominant wheel reaches an equilibrium on the rail, and is rubbing perfectly parallel to the rail. i.e. the car and the dominant wheel will not try to maintain the original angle of attack into the rail. The whole car, wheels, etc. will try to move toward the rail until the dominant wheel is rubbing "flat" or parallel to the rail. So if the dominant wheel is toed-in too much, the car keeps pushing the back wheel into the rail in an effort to bring the dominant wheel into this equilibrium -- BAD NEWS. If the dominant wheel is toed-in too little, you run the risk of track imperfections pushing the car towards the lifted wheel. When the dominant wheel is cheated in towards the rail by trimming 1/16 or 1/8" off the body at the axle insertion point, ala Warp's technique, then that allows a perfectly aligned car that same clearance between the back wheel and rail at equilibrium, and maybe gives you some room for error depending on how the rear wheel moves on the axle. So if there is no toe in at all, and your 3-wheeler is perfectly aligned, both front and back wheels are going to rub on the rail if it pulls towards the lifted wheel, unless you have less hub/body clearance for your front wheel. I think we are going to narrow the front end as Warp suggests, keep our toe-in moderate as is, and maybe leave a little extra clearance between the rear wheel (dominant side) and the car body, to account for that wheel floating hither and yon on the axle -- thus trying to guarantee it does not touch the rail.
You could of course, run a 4-wheeler and narrow your front end from one side, and accomplish the same thing. In fact, on a rough track, it might be safer to narrow your front end from both sides, and run a 4-wheeler so you don't run the risk of rubbing the lifted wheel on a 3-wheeler.*

Joe offers more insight: *I don't think you can hit the rail too late, but the trick is (I think) to go a little heavier on the pull so some other quirk in the track (bump, levelness, etc.) doesn't make your car go the other way. My gut feeling is within a couple feet your car ought to get over there. That's only about 1/2" of lateral movement. If your car goes too hard to the rail the back end will slide a bit as the wheel bites the rail and shifts itself to get parallel to the rail.*

Warps preferred method to toe in wheel: *We prefer to insert the axle in an old wheel (or a new #18!) all the way to the axle head. Then we mount the axle in a lathe collet, or a pro-axle tool (everybody has one, right?) mounted in a vice. We leave the normal inner hub to body spacing (plus about .020) between the inner wheel hub and the holding fixture (collet/pro body tool). Keeping the wheel against the nail head, we gently push in the direction of desired bend.
It doesn't take much!!
This all helps ensure the bend is in the proper place, and not in the middle of the working surface.
We then mark the direction of the bend with a sharpie so it can be used as a reference.
When installing the wheel / axle into the car, rotate the axle so the sharpie mark is at the 12 o'clock (straight up) position. This tells us the bend is up. Now if you rotate the axle forward, it will steer towards the rail. Rotate it backward and it will steer away. I use some special made pliers for the adjustments, but a standard pair with a little tape on the ends to protect the axle head will do the trick. Make the adjustments (rotation increments) very small, as a little will make a big change depending on how much bend you put in. You can almost feel a tiny "pop" when the axle rotates a touch, and this is enough for another run. *

Warp on degree of toe in: *It seems alignment may change slightly after initial set-up, a little more so with graphite type lube. Best case is to make a run or two (or as close to it as possible), then do final aligning with dominant front wheel.
I would say 1" in 5' is way light. 1" in 2' is closer, and the roll should be as fast as possible. *

Joe comments on degree of turn (toe-in): * Interesting! But that hard toe-in might just be what's needed to keep it on the rail. If you come off, a slight toe-in will put you back on the rail -- but if it's too slight, you'll come off again on a rough track; that's oscillation isn't it? I think a skewed lane or a dimple in the rail is enough to push it off.
The angle of incidence to the rail is not much here. The sounds like a lot, 1" in 2' but that dominant wheel only has to travel about 3/8" to hit the rail. It's not really crashing into the rail because it can't "free roll" long enough to start making a "sharp" turn relative to the rail. There must be some sort of trade off here between inertial startup that gets the wheels to speed, and the toe-in that guarantees it stays put. The early rub might slow it a bit...I guess the start would be faster if you delay contact -- but can your car stay on the rail will that lesser toe-in? Probably not.
Once it's on the rail, the back "moves over" a hair until the front wheel is pretty much parallel to the rail. I think this is going to happen more quickly with a light front end, but so could deflection. So I wonder if the lighter front end needs more toe-in.*

Re: Rail Riding - "How To Guide"

Posted: Wed Feb 14, 2007 10:40 am
by derbster
It can probably be found buried in another thread, but has the idea of setting a small diameter post of the utmost slippery material, from the bottom of the car, near the raised wheel (slightly in front), at the same height/depth of the wheel, to prevent the raised wheel from hitting the rail? It seems this would control and eliminate the potential of lost energy due to spinning the raised wheel in the RR design.

Re: Rail Riding - "How To Guide"

Posted: Wed Feb 14, 2007 10:53 am
by PWD_addict
Deleted since I misunderstood previous post. :oops: :oops: :oops: :oops:

Re: Rail Riding - "How To Guide"

Posted: Wed Feb 14, 2007 11:11 am
by doct1010
I believe he is referring to a whisker or roller bearing Sssnake documented and used on a potential WIRL mod. I would think they are illegal in all but open class racing.

Re: Rail Riding - "How To Guide"

Posted: Wed Feb 14, 2007 12:28 pm
by PWD_addict
doct1010 wrote:I believe he is referring to a whisker or roller bearing Sssnake documented and used on a potential WIRL mod. I would think they are illegal in all but open class racing.
Oh yeah--not the same. Sorry. I'll go back and edit my post. Doh!

Re: Rail Riding - "How To Guide"

Posted: Wed Feb 14, 2007 12:37 pm
by gpraceman
doct1010,

That is quite a summary of the discussion. I was looking for more of a boiled down summary like this:

Summary paragraph as to the benefits.

Step 1 do this
Step 2 do that
...

Conclusion paragraph.

What you put together is good reference to expand upon things, so I appreciate you putting that together. My apologies for being vague as to what I was looking for.

Thanks,

Randy

Re: Rail Riding - "How To Guide"

Posted: Mon Feb 19, 2007 1:15 pm
by hwsjr
Great work doct1010!!

Re: Rail Riding - "How To Guide"

Posted: Sun Feb 25, 2007 11:16 am
by PWD_addict
I will post this query here, instead of starting another thread as this is RR related.

Can anyone tell me how to do alignment on a Rail Riding three wheel PWD car? It seems that the front wouldn't matter much regarding alignment until you want to get it to rail ride. Do you just align the back wheels and then go for the front wheel to rail-ride?

TIA-
Dave Oshman (no relation to Brian) :D

Re: Rail Riding - "How To Guide"

Posted: Sun Feb 25, 2007 2:15 pm
by doct1010
PWD_addict wrote:I will post this query here, instead of starting another thread as this is RR related.

Can anyone tell me how to do alignment on a Rail Riding three wheel PWD car? It seems that the front wouldn't matter much regarding alignment until you want to get it to rail ride. Do you just align the back wheels and then go for the front wheel to rail-ride?
True and yes. We have had sucess following Warp and Joe's advice. Get the rear as perfect as possible (no movement in or out ala Stan's technique) then align front dominant wheel. Now, if you want to get creative, a mild 2-3 degree cant to rear wheels (we shim as opposed to bending axle) will keep wheel at head of axle offering a little more insurance it stays clear of rail.

Re: Rail Riding - "How To Guide"

Posted: Sun Feb 25, 2007 7:39 pm
by PWD_addict
doct1010 wrote:
PWD_addict wrote:I will post this query here, instead of starting another thread as this is RR related.

Can anyone tell me how to do alignment on a Rail Riding three wheel PWD car? It seems that the front wouldn't matter much regarding alignment until you want to get it to rail ride. Do you just align the back wheels and then go for the front wheel to rail-ride?
True and yes. We have had sucess following Warp and Joe's advice. Get the rear as perfect as possible (no movement in or out ala Stan's technique) then align front dominant wheel. Now, if you want to get creative, a mild 2-3 degree cant to rear wheels (we shim as opposed to bending axle) will keep wheel at head of axle offering a little more insurance it stays clear of rail.
Interesting on the cant. Makes sense--especially if the wheels aren't lined up well by the starter. Is 2-3 degrees about one wax paper shim?

Re: Rail Riding - "How To Guide"

Posted: Sun Feb 25, 2007 8:19 pm
by doct1010
PWD_addict wrote:Interesting on the cant. Makes sense--especially if the wheels aren't lined up well by the starter. Is 2-3 degrees about one wax paper shim?
Don't know for sure what wax paper measures. I do recall reading and noting .017" for each degree of cant for a BSA axle, 3 degrees you would measure .051" for the location of the nail head. A check we use after alignment, slow roll forward and back wheels should NOT migrate toward body, but stay out on head. Careful with this, you could wind up in left field when also trying to steer it to rail. First be absolutely SURE rear wheel alignment is "dead on", before proceeding with above. You must insure rear wheels are not steering, that is for and aft alignment which can also push wheel to head.

Re: Rail Riding - "How To Guide"

Posted: Sun Feb 25, 2007 9:45 pm
by Stan Pope
My aged memory says that they measured about 0.001" and compressed some when used. I applied 3 layers (one piece folded over twice) to get nice RR results. One thickness produces much less than a degree change! And, the resulting car ran quieter than a mouse sneaking through a roomful of cats!

Re: Rail Riding - "How To Guide"

Posted: Mon Feb 25, 2008 10:14 am
by colopwdfan
"Warp offers this cautionary caveat regarding narrowing:*One thing to mention though. During the small amount of testing I have been able to do this year, I did find that any excessive narrowing of the front tread width (more than 1/16" or so) can slow the car by making it VERY (overly) sensitive to steering adjustments. This makes it almost impossible to find the "sweet" spot during tuning, and a minute adjustment can get you into left field..... As of now, I would stay with the 1/16" dimension and you should be good!! *"

OK,
Referring to Dr Jobe's Lecture #14, Page 10, og this pdf file:
http://www.pinewoodderbyphysics.com/pdf ... e%2014.pdf

I have some questions:
Is the illustrated way the easiest to accomplish RH?

Is the 1/16" the total indent?

Or 1/16" X 2 (each side) = 1/8th" total?

Better or easier to work one side or both?

And for ease of reference, (since the BSA blocks are not all exact in dimensions) what is the dimension of the guide rail width? Is there a standard?

The instruction insert in the PWD kit has a dimension. Is it accurate?

What is optimum distance between inside edges of the wheels?

TIA
John