Why do i ask why

[AceMontana]

I know ive had alot of post very close together so i apologize if my long winded ramblings (and poor spelling and grammar)are getting old...ive been reading this forum pretty much nonstop since stumbling upon it recently....a response i got to a previous post lead me to another question to ponder...hold tight its gonna be lengthy ....its been said to make a car fast riding the rail is a good idea...makes perfect sense...i mean the line of the rail is alot shorter than zig zagging around it....to do this we make a DFW steer into said rail ...again makes perfect sense take the heaviest wheel and steer the car with it....the trade off is friction on the rail ( overcome by rolling a straight line) and the friction of the DFW pushing on the body ...now here is where my mind goes squirly....in my test at home when the rear wheels migrate towards the body its bad news bears...a real time killer right? So my mind goes to how do i steer the car to the rail annnd keep the DFW off the body? So i start thinking about things i know about front end alignments in real cars....and "caster "comes into the playing field along with its atributes on spindle (or in this case axle) pressure....sooo the more positive caster...the more axle pressure....more axle pressure =more friction...more friction is bad. How do i reduce it? Give the oposite front wheel negitive caster my mind fires back in this battle with itself...hmm thats not going to work... that wheel is floating in space so onto solution 2. steer it away from the rail and let the NDFW ride the rail.....bad juju acording to this board...so here i am again durring the wee hours of morning asking if anyone can tell me why to not run negitive caster on the DFW , allowing both front wheels to run on the axle head? I mean the physics of it...not " just because its faster the other way" my actual question is WHY is it faster?...and does this stuff keep anyone else awake at night?

 

[DerbyDad4Hire]

The wheels ALWAYS hit the body no matter how the axle is canted. Just make sure the body is slick and hard. Make sure on a slow roll the rear axles migrate out evenly.

 

[B_Regal Racing]

The DFW has a negative cant so the wheel rolls over the seems/bumps/imperfections in the track while riding the rail. If it had a positive cant like the rear wheels, yes, the FDW would migrate away from the body, but the FDW would slide over the seems/bumps/imperfections in the track. It is far better to prep the body as DD4H said above and have the FDW roll over bumps...

 

[AceMontana]

The DFW has a negative cant so the wheel rolls over the seems/bumps/imperfections in the track while riding the rail. If it had a positive cant like the rear wheels, yes, the FDW would migrate away from the body, but the FDW would slide over the seems/bumps/imperfections in the track. It is far better to prep the body as DD4H said above and have the FDW roll over bumps...

I was refering to caster not camber or "cant" as it is called here caster is the adjustment of the tire contact patch in relation to the axle center line....contact patch forward is postive caster ( like a motor cycle front wheel)....contact patch rearward (like a shopping cart wheel) is negitive caster the relationship of these points will make a wheel drift one way or the other ...so what im saying is its possible to have negitive camber or "cant" and have the caster steer the car ...in my scenario the car would be held against the rail without the FDW touching it ...i hope im making sense in some way....i guess forgoing the physics of front suspension geometry can someone tell me why the NDFW cant touch the rail and be as fast or faster?

 

[bracketracer]

again makes perfect sense take the heaviest wheel and steer the car with it

If your DFW is the heaviest loaded wheel on your car you need to read more here. Maybe you meant "lightest"?

We don't let the NDFW touch the rail because it takes energy to spin any wheel. Spinning three wheels takes less energy than spinning four wheels. At best, you're going to lose about .010 with four touching vs three touching. A small amount, sure, but "all other things being equal" three touching always wins.

 

[AceMontana]

If your DFW is the heaviest loaded wheel on your car you need to read more here. Maybe you meant "lightest"?

We don't let the NDFW touch the rail because it takes energy to spin any wheel. Spinning three wheels takes less energy than spinning four wheels. At best, you're going to lose about .010 with four touching vs three touching. A small amount, sure, but "all other things being equal" three touching always wins.

I was implicateing the heaviest front wheel....i think youve answered my question though...thank you

 

[TRE]

kiss