Four on the floor rail rider thoughts

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woodworx
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Re: Four on the floor rail rider thoughts

Post by woodworx »

Our pack rules are the ones are the official district rules. Our Com is 1 1/4 in front of rear wheels. We did pick up speed this year with a slight cant on wheels and COM moved back about an inch. I know this is conservative by most standards here but our track is rough, My sons car derailed twice this year with the COM moved back. I never got to see the car after the race since they are impounded till districts but I did notice it got faster and seemed more stable after the second crash. While thinking about it It is my best guess that it might of adjusted itself into a rail rider when it flew off on the floor. I see why they would impound the cars, to keep dads hands off or those that would build another car to perform better on a good district track. The down side is if you have a problem you cant fix it, I read in the rules that you need to relube before they are boxed because it cant be done at the race, which we were unable to do also for the same reasons.
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joe
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Re: Four on the floor rail rider thoughts

Post by joe »

Woodworx, you have those silly gestapo rules! I really don't see why cars need to be impounded. This is tantamount to saying "we expect some of you will cheat, so we're doing this so you can't cheat." Kids should be able to have their cars.

As for the four wheels down railriding. The problem as I see it again is keeping an equal amount of weight on each front wheel - IF you want to steer with the wheel opposite the railriding wheel. Imperfections in the track can easily cause the car to shift from one wheel to the other, making the steering inconsistent, especially if one wheel is aligned straight. I know 4-wheel railriding works OK toeing the dominant wheel and floating the opposite wheel, and it works well toeing the dominant in and the opposite out (floating or not floating). I don't know yet whether it will work by aligning the railriding wheel straight. Possibly, just haven't gotten it right yet.
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Re: Four on the floor rail rider thoughts

Post by PWD_addict »

joe wrote:Woodworx, you have those silly gestapo rules! I really don't see why cars need to be impounded. This is tantamount to saying "we expect some of you will cheat, so we're doing this so you can't cheat." Kids should be able to have their cars.

As for the four wheels down railriding. The problem as I see it again is keeping an equal amount of weight on each front wheel - IF you want to steer with the wheel opposite the railriding wheel. Imperfections in the track can easily cause the car to shift from one wheel to the other, making the steering inconsistent, especially if one wheel is aligned straight. I know 4-wheel railriding works OK toeing the dominant wheel and floating the opposite wheel, and it works well toeing the dominant in and the opposite out (floating or not floating). I don't know yet whether it will work by aligning the railriding wheel straight. Possibly, just haven't gotten it right yet.
What about making the dominant wheel the steering wheel, and the non-dom the railriding wheel? Seems like there may be less rail friction if there's less pressure/weight on the RR wheel. Sorry I'm being the idea guy and not the test guy. I wish I had a test track.
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Re: Four on the floor rail rider thoughts

Post by joe »

I don't think the non-dom would work as the riding wheel, as it doesn't work to rub it when it's the lifted wheel. It's considerably slower than the dominant wheel in that configuration, and even slower than a 4 wheeler that rubs dominant. But maybe you could configure it to work!
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Re: Four on the floor rail rider thoughts

Post by Derby Goes Bananas »

:idea: We drill the wheel bore on the non RR front wheel to an oversized diameter to allow the axle on that side to "travel" without contact. This prevents the nondominant, nonsteering, nonrailriding front wheel from bearing any weight, but it still meets the 4 on the floor rule requirements! The wheel rolls as "frictionlessly" as possible, as it bears no weight, and is essentially along for the ride. This may also have increased stability benefits, as that wheel will not be loading/unloading due to track imperfections. We tried this in 2008 on both of my sons' cars with great success. The 2008 cars also beat our previous year's with similar setups (excepting the new oversized wheel bore technique). Any thoughts on this technique? :wink:
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Re: Four on the floor rail rider thoughts

Post by Stan Pope »

"Four rolling" is not my primary experience, so can't tell you if my try at oversized bore a year or so ago is representative. It gave "okay" results but not up to "good" results.

In analysis, the free-rolling wheel is subject to track irregularities and may contribute to higher variation in run times if the irregularities cause side-to-side movement of the wheel.
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Re: Four on the floor rail rider thoughts

Post by *5 J's* »

Hmm, some interesting concepts here. Has anybody any of these in practical application. Right now I would feel safest using the DFW to steer into the rail. I like the other concepts but will wait for feedback from real world application.

I am now trying to figure out how much of an angle to drill the hole to get the desired toe with the new wheels. I'm starting with Stan's suggestion of .4° toe-in on the RR wheel and .2° toe-out on the other front wheel.

I am also assuming nominal measurements on the axle diameter (.087") and hub bore (.096") and bore length (.273"). (I didn't have any nominal data for bore length so extrapolated from multiple sources). This gives .009" of bore slop to be taken up over a bore length of .273", which gives an axle angle of 1.89°. This would me to achieve .4° toe-in I need to drill the hole at and angle of 2.29°, correct? I am just trying to verify my numbers and calculations.

Obviously once I get into aligning - I may have to shim or bend the axle as I am using notional numbers and theoretical perfect drilling. (Yea we all know this always happens).

(I know I had a similiar camber question in another post - but I'm trying to keep my questions in the post they are the most germane to - if this is bad forum practice - please advise)
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Re: Four on the floor rail rider thoughts

Post by Stan Pope »

*5 J's* wrote:... This gives .009" of bore slop to be taken up over a bore length of .273", which gives an axle angle of 1.89°. This would me to achieve .4° toe-in I need to drill the hole at and angle of 2.29°, correct? I am just trying to verify my numbers and calculations.
I'd not include "slop" in the toe computation. The axle will try to lie in the "valley" of the bore (or in the valleys", in the case of an axle with camber and toe) and that should have little "slop" error. Or so it seems to me.
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Re: Four on the floor rail rider thoughts

Post by Kenny »

*5 J's* wrote:Hmm, some interesting concepts here. Has anybody any of these in practical application. Right now I would feel safest using the DFW to steer into the rail. I like the other concepts but will wait for feedback from real world application.

I am now trying to figure out how much of an angle to drill the hole to get the desired toe with the new wheels. I'm starting with Stan's suggestion of .4° toe-in on the RR wheel and .2° toe-out on the other front wheel.

I am also assuming nominal measurements on the axle diameter (.087") and hub bore (.096") and bore length (.273"). (I didn't have any nominal data for bore length so extrapolated from multiple sources). This gives .009" of bore slop to be taken up over a bore length of .273", which gives an axle angle of 1.89°. This would me to achieve .4° toe-in I need to drill the hole at and angle of 2.29°, correct? I am just trying to verify my numbers and calculations.

Obviously once I get into aligning - I may have to shim or bend the axle as I am using notional numbers and theoretical perfect drilling. (Yea we all know this always happens).

(I know I had a similiar camber question in another post - but I'm trying to keep my questions in the post they are the most germane to - if this is bad forum practice - please advise)
I strongly recommend you consider going for slight bend in front axle(s) and adjust for exactly what you want by rotating. Second alternative would be shimming to achieve the slight toe and camber on the steering wheels. Shimming gives more precision, but bent is SO easy and fast and effective. Just sayin'

You're drilling pine wood which is inherently unstable unless you taken great pains to stabilize it and shield it from environmental effects. There is some good prospects that your car will change alignment anyway. So be sure to check just before race day to be sure it's rolling the way you intend.

GL,

K
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Re: Four on the floor rail rider thoughts

Post by *5 J's* »

Yes - I will give it some thought. Last year, though we didn't make a railrider, we did end up canting slightly to keep the wheels off the body. I tried shimming, but wasn't having consistent luck, so I resorted to bending the axle. I did find aligning a lot easier being able to rotate an axle to get the desired cant. However, last year I likely induced some undesired forces - such as differential friction- not fully understanding all the forces at work (Not that I am proclaiming that I do now). This year I will try Stan's method of aligning Cambered Rear Axles.

Anybody else on the pro's and con's of canting (either toe or camber) by drilling the block, or bending the axle, or shimming, or a combination? Love to hear others experiences with the different methods.
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Re: Four on the floor rail rider thoughts

Post by *5 J's* »

I'd not include "slop" in the toe computation. The axle will try to lie in the "valley" of the bore (or in the valleys", in the case of an axle with camber and toe) and that should have little "slop" error. Or so it seems to me.
Hmm - something to consider Stan - that would mean that there is a 1:1 correlation between the angle of the axle (if purely in the horizontal plane) and the toe. But if we are talking about the DFW, or the "steering" wheel, might the axle ride out of the valley (or at least up the valley) as you have one force driving the car to the rail (from the toe-in) and a perpendicular force pulling the car down the track (gravity). Please pardon my lack of the physics lexicon - I am trying to explain this so that all can understand what I'm talking about.

Next - when the DFW contacts the rails - does it stayed toed-in or does it force the axle out of the valley to straighten the wheel against the rail. Hmm - I need a car with an adjustable toe such as Randy made for his Rail Riding test.

If indeed the axle stayed in the valley - then a 0.4° forward bend in an axle would result in a 0.4° toe-in. Can anybody verify this in actual use? I thought most were using a a higher angling their axle more than that.

I see you mention an axle with camber and toe. If I need to have all four wheels FLAT on the track is there a benefit to adding camber to the DFW on a railrider. I cannot the wheel on edge - and I would think that I cannot add negative camber to the the wheel out to the axle head given that the DFW is toed-in. What am I missing here?
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Re: Four on the floor rail rider thoughts

Post by Kenny »

I see you mention an axle with camber and toe. If I need to have all four wheels FLAT on the track is there a benefit to adding camber to the DFW on a railrider. I cannot the wheel on edge - and I would think that I cannot add negative camber to the the wheel out to the axle head given that the DFW is toed-in. What am I missing here?
While you may not "cant" your wheels to run on edge, you most certainly can align the wheel with very slight camber and toe-in while preserving 4 wheels flat on track. It may not be optimal edge runner in truest sense, but perfectly legit in my mind. I ran slight negative camber on my front dominant steering wheel quite successfully for a while.

Anything you can do to incent the wheel to refrain from oscillating from head to body is good. a very slight camber does that for you. In this case I'm not sure that a positive camber will be as effective as a neg camber. Perhaps you can try each and test it out to decide.

K
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Re: Four on the floor rail rider thoughts

Post by *5 J's* »

Kenny - if I have a car with a DFW that has toe-in and a negative camber - how does it "behave" when I get to the alignment process. Obviously going forward I want the car to steer in the towards the rail - and backward I assume it would steer away from the rail - but how does it act on the axle? IN/OUT? OUT/OUT?
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Re: Four on the floor rail rider thoughts

Post by Kenny »

*5 J's* wrote:Kenny - if I have a car with a DFW that has toe-in and a negative camber - how does it "behave" when I get to the alignment process. Obviously going forward I want the car to steer in the towards the rail - and backward I assume it would steer away from the rail - but how does it act on the axle? IN/OUT? OUT/OUT?
Good question. Since we are talking "slight" on the canting I'm not sure you'll be able to hold OUT rolling backwards on the alignment board. However for the fr dom wheel, I don't think that matters as long as you verify the rears OUT/OUT using a straight neutral front alignment first. After the rears are perfectly resonant then adjust in some toe and camber so your fr dom stays OUT going forward and drifts properly.

If you are shimming you could strive for neutral forward and backward, then OUT/OUT forward and backward with some neg camber, then finally inject some toe-in to get your drift.

If you are bending the fr dom axle slightly, things are weird since each rotation adjusts on two planes simultaneously.

I sure hope this doesn't confuse you. I'm not very good at describing this procedure clearly.

K
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Re: Four on the floor rail rider thoughts

Post by *5 J's* »

Not confusing - good explanation

Yes - definately would verify rear are OUT/OUT with a neutral toe, negative camber.

It sounds like I want enough toe to drive drift say 2" over 4', then enough negative camber to force the wheel OUT going forward. I guess I have to see this - as toe-in will try to force the wheel IN. (IN/OUT is an indication of toe-in for those that may be new to alignment), while negative camber tries to force the wheel OUT (OUT/OUT is an indication of negative camber).

The trick will be to find the balance. We tried aligning with shims last year and it became to frustrating so we went to axle bending. Last year we didn't make a RR so we just looked for OUT/OUT while tracking straigt down the track. Obviously this year we will have a bot more work - especially if we go with bending the axle as each rotation adjusts in two planes simultaneously as you note. Hmm- let me think out loud - what if I drill x amount of toe-in then bend an axle for y amount of camber. Then I can roll the axle slightly to tweak. I would still be adjusting in two planes simultaneously, but would it be an order of magnitude less....

Anyway - thanks Kenny - I wans't sure that I could get a forward OUT on the DFW with the toe-in.
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