Rail Riding with four wheels

[sarge74]

Hi everyone!
I've just found this place! Awesome! I just bought the RailRiding tool the Pro Axle tool and Pro Body tool among other stuff here at DerbyWorx to get my son and I ready for our January PWD.
I've been studying what you've all been suggesting for speed and would like to try rail riding. My district however doesn't allow racing on only three wheels. All four must touch the track.
What do you guys suggest with rail riding if I can't float that right front? Can It be done or should I just go with canting all four wheels at 2.5?
Thanks

[evolution]

Does your district tell you the wheels must be across rom each other or that there has to be 4 wheels touching. If they do not have to be across from each other you could put the NDW to the read of the car.

[sarge74]

"9. All four wheels must touch the race ramp and be even- no three wheelers."

"20. Wheelbase (4.4") shallnot be modified and be square.)

Those are the rules that seem to be keeping me from joining in on the three wheel rail riding speed club! I'd like to still attempt to RR, but I've read that the FDW must be set in 1/16" from the where the back weele is. I might have trouble doing that due to rule 20.
Is rail riding still an option then?
I've also read that some guys who need to keep four on the track, have used weight to create a dominant wheel. In other words they have the weight set up toward the back and a bit toward the FDW. Then they can set the FDW to drift the 1" per 6 feet toward the rail.
Your thoughts?

Thanks for the reply! Any help I get is awesome. First Car with my Wolf scout! Race is in 7 weeks!

[Sappington R]

This is an interesting question. We have always used three wheelers. However, I made a few observations that may be of interest to you.

We drilled our axle holes on our EXT WB using the Derby Worx Pro-Body Jig. We did our very best to make sure that all four were drilled as good as we could. After drilling several car bodies, we tested each using the same combo of wheels and axles (non canted) and BTW the bodies had not been cut yet. In each car there was always a wheel that was slightly higher up than the rest, although each wheel did rotate when pushed on the counter top. So, were easily able to pick the "dominate " wheel. I suppose that the variance was due to the imperfections in the block of wood- If you read through the archives on this message board, you will find more of the same information- it is nearly impossible to have equal distribution on all four wheels (especially on a scout car).

Now, if you are looking to RR and must have four down, and are set up with the Rail Rider Tool to bend your axles consider the following: If you bend your FDW axle and keep you Non-Dom straight, it is possible that when the car is sitting still it will have the appearance that all four are touching, particularly if the DFW is in close to the body. But, if you have the axle set-up with Positive Camber, then as the wheel migrates to the head of the axle, wouldn't it in theory, since the bent axle is "down" lower, have the effect of raising the car slightly higher, that is, high enough to raise the NDW while RR'ng? As the FDW touches the center rail, it will cause the wheel to migrate out to the axle head.

BTW: This is just a hypothesis. I know that there are many others that post here that are much more knowledge about physics (3Cubb are you out there?).

In any event, I hope this has given you something to think about as you go about you wheel set-up.

Sapp

[sarge74]

ahhh, yes I see your point, Sapp. The RR wheel would cause some lift as the it rides the rail and the wheel heads out on the Pos. Cambered axel. That would lift the Non-dom wheel then. It wouldn't happen immediately but in theory would turn the car into a 3 wheeler as it raced down the track. That is something to factor in.
I really appreciate your input. Very very cool and helpful!

I think I'm going to try and make the non-dom front wheel set to "Barely" touch the tack. After reading other posts, I plan on setting the back wheels to 2.5 negative camber, the front dominant wheel to 1.5 positive camber, but not sure how to set the non-dom wheel. Should I make it negative 1.5 in case it touches so that wheel is off the body and only contacting the inside of the tapered axle head? Positive camber? No camber?
Also, how are you guys "steering" that front Dom-wheel so that it eases onto the rail at 1" per 6 feet? Do you rotate the positive camber forward a bit till it turns to the rail just so?

Thanks for any and all help! So extremely happy I found this community!

[Sappington R]

Before you start bending axles, I recommend a lot of table top testing. I am going to try to post a video of a recently built chassis on a test board. All of the axles are "straight" on this set up. You will see in the video how the car steers very straight with no "cant". The reason why I did this was to get a reference point or starting point before bending. If you can get the car to run straight with no bending then you know what you are working with.

If the car runs straight with no canting (and the wheels stay away from the body and axle heads in both forward an reverse) then you are almost there. Adding camber is tricky. It's easy to over do it. Sometimes less is more. Therefore, if you decide to cant your rear axles, try with small amount first. You can always increase as you go along. On the front: FDW Pos 1.5 on the NDW keep it straight.

You are correct in rotating the axle. Be sure to mark it with a sharpie. Many cut a groove in the head with a dremel like a flat head screw- it's a rather new "old trick"- K-House Groove it's called. Rotating small amounts will get the car to steer.

You may also want to experiment with shaving the NDW outer diameter with the DerbyWorx wheel shaver- decrease ever so slightly less than the FDW. It will touch the surface when not moving (barely)


One last thing- according to someone that knows far more than I, a RR set-up with POS CAMB on the FDW, the wheel will stay in the middle of the axle- that is, not quite on the head nor the body. It should give you the "lift" that you need.

[3cubdad]

Man Sappington,

There you go giving away one of my few remaining secrets!! ;D Sappington is correct. As the car is turned into the rail, the rear wheels are trying to drive a straight line, which causes the body to want to move away from the wheel which is limited by the rail. The lighter the front, the further towards the head the wheel will go.

We've found ourselves in a new district this year that also requires four touching. I was hoping this was going to remain my silver bullet! ;D ;D ;D

IF you're really trying to squeeze out that last 0.01 seconds, there's one more factor to consider. I run "hyper" cant on my league cars. (so that the wheels roll truly on edge). When that is done, a hyper positive front cant lifts the front of the car. To account for aerodynamics, you have the put the axles slightly higher than the rear, especially if the rear is hyper negative cant. For scout cars, ignore this. Use the derbyworx tool, 2.5 on front, (to get maximum lift) and 1.5 on rear. (I use 2.5 all the way around!)

If anyone's really interested, I can post a couple of diagrams showing the forces and how the car reacts..... more of that geeky physics stuff!

3cubdad

[sarge74]

Nov 24, 2009 13:45:26 GMT -6 3cubdad said:

If anyone's really interested, I can post a couple of diagrams showing the forces and how the car reacts..... more of that geeky physics stuff!

3cubdad

I sure would be interested!

Thanks a bunch, Sappington and 3cubdad!
Very much appreciated. I'm learning so much here! You folks are awesome!

[teamfreeroller]

narrow front of car 1/6 on both sides of car. cant dfw down just a little to steer car and it will lift the other front wheel .and that wheel push it in on car body so it can not spin up. that my 2 cents worth.

[clydesdale]

3cubdad, can you explain what the secret was the Sappington gave away. I am interested in any physics diagram that may further explain how to gain a little speed with all four wheel at the same axle height. THANKS

[2borggold]

Is CAMBER the same as CANT? Too many terms for me to keep straight....

[2borggold]

Nov 18, 2009 20:50:49 GMT -6 sarge74 said:

[b
"20. Wheelbase (4.4") shallnot be modified and be square.)

Those are the rules that seem to be keeping me from joining in on the three wheel rail riding speed club! I'd like to still attempt to RR, but I've read that the FDW must be set in 1/16" from the where the back weele is. I might have trouble doing that due to rule 20.

From that wording, I would read Rule 20 to mean that your wheels need to be directly across from each other.... i.e. Square to the BODY of the car. No off set axles. Therefore.... I think you could narrow the front end by your 1/16".

Just my interpretation....

[2borggold]

Nov 24, 2009 13:45:26 GMT -6 3cubdad said:

Man Sappington,

There you go giving away one of my few remaining secrets!! ;D Sappington is correct. As the car is turned into the rail, the rear wheels are trying to drive a straight line, which causes the body to want to move away from the wheel which is limited by the rail. The lighter the front, the further towards the head the wheel will go.

We've found ourselves in a new district this year that also requires four touching. I was hoping this was going to remain my silver bullet! ;D ;D ;D

IF you're really trying to squeeze out that last 0.01 seconds, there's one more factor to consider. I run "hyper" cant on my league cars. (so that the wheels roll truly on edge). When that is done, a hyper positive front cant lifts the front of the car. To account for aerodynamics, you have the put the axles slightly higher than the rear, especially if the rear is hyper negative cant. For scout cars, ignore this. Use the derbyworx tool, 2.5 on front, (to get maximum lift) and 1.5 on rear. (I use 2.5 all the way around!)

If anyone's really interested, I can post a couple of diagrams showing the forces and how the car reacts..... more of that geeky physics stuff!

3cubdad

I'd like to understand more about this. Diagrams may help.