Straight runner - wheel canting?

[mozartk626]

I found out our pack's track does not have a center rail, so no rail riding is possible. Further, our rules state that the axles must be "firmly in the original slots" (which I'm pushing just a bit because every car building site seems to recommend pre-drilling the axel holes to sit right above the stock slots so that the slot "bleeds through" the bottom of the hole). Anyway, I was wondering - since there is no rail to try to ride, is it at all recommended to try to cant the wheels? If the car is a straight runner (not a rail rider), does canting the axles (a) reduce the friction on the wheels, and/or (b) aid in fine tuning the alignment?

[Vitamin K]

I've heard some speculation that canting the wheels helps to make them run more true, since you're focusing the axle contact on a smaller surface area, but I don't really have solid facts on this. When we camber wheels, it's to keep them off or on the rail (rear vs front, respectively).

That said, I've heard it is is possible to make a side-rail guided car, but this is a challenge I've yet to undertake. I'd sort of like to build a test car for it sometime.

[whodathunkit]

I have raced 18 wheelers on a no center rail wood track.

My recommendation for running on a track with no center rail.
Is to make a straight running car. No wheel canting!
You can lift one front wheel.
If the track is a plastic super track that has 1/4” high guides..
You might also want to bring the front wheels back.. to keep alignment and wheels intact between races. (No long wheel base.)
As the foam stop section for this no center rail track is brutal on front ends.

Tracks with no center rails are challenging enough.
And can be fun to race on with out over complicating it.

Best of luck mozartk626
And Welcome to DerbyTalk.

[FatSebastian]

...pre-drilling the axle holes to sit right above the stock slots so that the slot "bleeds through"...

You can't get more "firmly" in the slots than that!

does canting the axles (a) reduce the friction on the wheels, and/or (b) aid in fine tuning the alignment?

Slight canting (enough so that there is daylight between the outer tread and track surface) reduces wheel-to-track contact. Fewer imperfections from the track and tread are encountered when rolling slightly cambered. During the course of a derby we have observed a build-up of debris across treads making flat contact, so maybe there is a potential benefit as VitaminK suggests above...

Now - and this is pure speculation - but I am also a bit curious about the potential for static cling building up due to the motion of the plastic wheel along the (plastic?) channel. For example, some people have noticed that putting graphite on the tread offers a slight speed benefit on aluminum track, and this has been speculated as preventing electrostatic build-up on the wheels. (Others have said graphite on the tread has no noticable effect.) We have no personal experience with plastic channel track, so I would be curious if others think about electrostatic build-up with a plastic track... and if so, whether this might be another reason to minimize tread contact?

[FatSebastian]

...make a straight running car. No wheel canting! You can lift one front wheel.

I would guess it might be possible to still run fairly straight with wheels slightly cambered, but without any toe angle. Need to think about that... Camber should help keep the body from sliding laterally between the wheels and thus offer some directional stability even if there is no center rail to steer into.

If running straight, then the CoM placement also needs to be conservative.

There is no longer the constraint of being wide enough or high enough to fit over a guide rail. Can you make the car narrower and/or lower, and if so, is there any benefit with that (say, travel further before hitting side rail, or lower drag profile, or...)?

[whodathunkit]

We have no personal experience with plastic channel track, so I would be curious if others think about electrostatic build-up with a plastic track... and if so, whether this might be another reason to minimize tread contact?

FS, this is a very good question on electrostatic build up with plastic tracks .. Abs plastic is what I recall the super track made from.

Found a video of cars racing on a super track with no center rail.. and most cars are running with out canted wheels.
https://www.youtube.com/watch?v=YgxamUfxbnE

Could it be that the abs plastic super track has a slicker track surface.. that is not as porous than the aluminum or wood track surfaces.
So that more wheel tread surface is needed to hold the car if it bangs the side rail

[whodathunkit]

There is no longer the constraint of being wide enough or high enough to fit over a guide rail. Can you make the car narrower and/or lower, and if so, is there any benefit with that (say, travel further before hitting side rail, or lower drag profile, or...)?

With side rail tracks the benefit is the elimination of under carriage issues the super track also has a different starting ramp profile then wood or alum tracks.
As far as making the car narrower and or lower.. Id want to see the race rules.

[mozartk626]

That said, I've heard it is is possible to make a side-rail guided car, but this is a challenge I've yet to undertake. I'd sort of like to build a test car for it sometime.

So I'm not the first person to have the idea of making a "wall rider!" I was trying to work it out in my head, but the only two ideas I came up with were (A) bend the wheel that doesn't touch the track way out so that it rides the wall (which then makes contact with a surface and defeats the purpose of having one wheel that doesn't touch), or (B) canting the wheels opposite the way you'd make a rail rider so that one contacts the wall (which would push the wheel inward against the car body and create too much friction).

[exoray]

Could it be that the abs plastic super track has a slicker track surface.. that is not as porous than the aluminum or wood track surfaces.
So that more wheel tread surface is needed to hold the car if it bangs the side rail

Plastic tracks are 'slicker' than aluminum...

The friction coefficient of aluminum is about 0.6
The friction coefficient of ABS is about 0.4

So that is going to affect the wheels in all sorts of ways...

Plus there is the overall rigidity difference between the two types of tracks, cars rattle and micro bounce down aluminum tracks as the track is stiff, plastic tracks naturally damper a lot of that rattle and micro bounce, but on the flip side the plastic track (less a lot of extra supports) is moving and flexing just that much as the car goes down the launch incline so there is that effect to factor in... It would also be interesting to see how much micro side to side movement happens between the two track types as cars that are not rail riding bounce off the rails...

[exoray]

We have no personal experience with plastic channel track, so I would be curious if others think about electrostatic build-up with a plastic track...

The electrostatic build-up on plastic tracks is real, since graphite has anti-static properties it would be interesting to see if entirely buffing out the wheel surface in graphite has a positive effect when run on plastic tracks to negate this...

Foreign debris is the biggest concern (IMO) with plastic tracks, they suck dust, hair and fur right out of the air like a magnet...

But in the end, I'm thinking any electrostatic effect between the car and track isn't something that is going to factor in at most 'scouting' level races at any measurable amount...

[Vitamin K]

That said, I've heard it is is possible to make a side-rail guided car, but this is a challenge I've yet to undertake. I'd sort of like to build a test car for it sometime.

So I'm not the first person to have the idea of making a "wall rider!" I was trying to work it out in my head, but the only two ideas I came up with were (A) bend the wheel that doesn't touch the track way out so that it rides the wall (which then makes contact with a surface and defeats the purpose of having one wheel that doesn't touch), or (B) canting the wheels opposite the way you'd make a rail rider so that one contacts the wall (which would push the wheel inward against the car body and create too much friction).

What I've heard is that you put positive camber on the DFW and tune the drift so that the car steers into the wall on the DFW side.

Additionally, you need to narrow the rear side behind the DFW in order to make sure that the rear doesn't come into contact with the rail.

It sounds pretty funky, and if I were gonna try it, I'd build some kind of edge-guided test strip to test...but it could be fun!

[whodathunkit]

So I'm not the first person to have the idea of making a "wall rider!" I was trying to work it out in my head, but the only two ideas I came up with were (A) bend the wheel that doesn't touch the track way out so that it rides the wall (which then makes contact with a surface and defeats the purpose of having one wheel that doesn't touch), or (B) canting the wheels opposite the way you'd make a rail rider so that one contacts the wall (which would push the wheel inward against the car body and create too much friction).

What I've heard is that you put positive camber on the DFW and tune the drift so that the car steers into the wall on the DFW side.

Additionally, you need to narrow the rear side behind the DFW in order to make sure that the rear doesn't come into contact with the rail.

It sounds pretty funky, and if I were gonna try it, I'd build some kind of edge-guided test strip to test...but it could be fun!

Okay guys.. back in day some cars used spring type curb feelers.
So here's a wild /crazy that could be fun to play around with as well for the 1/4'' high out side guide rails.. "wall rider!"

https://www.maximum-velocity.com/pinewo ... imes-v6i7/
please read what Randy has to say in his conclusion .. Are feeler's legal?
Or can one call them decoration's to the car.. like an air jack system to there Indy car.

[philm63]

Paint the car like a cat and give it "whiskers".

No?