[s-cars] alignment Q

Thu Jan 15 07:12:41 PST 2009

If I read the web correctly, derby wheels have a square surface contact and
are hard. In that case, camber will reduce the contact surface and the
contact point will be very close to pinpoint contact, so scrubbing from
camber will be reduced to a minimum. Worth experimenting with at least.

As for toe, 0 toe will minimize the friction but will make the car change
direction at the smallest pebble especially with high camber. A slight
toe-in may be preferable for stability at the expense of little speed lost.

As for the wheel/hub genius idea, if I understand it well, having the wheel
rotating on a fixed hub will increase the contact surface and decrease the
linear speed. This, IMHO, will increase friction. I would rather go back to
the original design, with a slightly viscous lubricant, to create a liquid
bearing. Once more, experimenting will be required to determine which
viscosity will be enough so the liquid bearing can support the weight of the
car without slowing down the wheels. Since every pebble will kill the liquid
bearing effect, I would go with dry lubricant plus liquid lubricant so you
still have lubrication when the wheel hit the axle when the car goes over a
pebble.

Of course, this is all theory, so Reality Mileage May Vary.

Vincent

-----Message d'origine-----
De : s-car-list-bounces at audifans.com
[mailto:s-car-list-bounces at audifans.com] De la part de djdawson2 at aol.com
Envoyé : 14 janvier 2009 17:40
À : pkrasusky at ups.com; s-car-list at audifans.com
Objet : Re: [s-cars] alignment Q

 Toe would cause more scrub than camber.? I think the main goal for you is
to minimize lost energy.? There is an energy loss associated with camber...
look into motorcycle tire design.? High speeds, combined with a lean angle
(essentially camber) generates extreme heat = lost energy.

Normally, derby car wheels are more like a motorcycle tire than a car
tire... the contact surface has a radius instead of being flat.

Think of the pinpoint contact with the road surface.? Only at the exact
point of contact is where the ideal situation exists.? As soon as the tire
moves past that point of contact it is now "scrubbing" perpendicular to the
direction of travel.? It's a little like taking a turn in a vehicle with a
live axle... something has to scrub.

0 toe and 0 camber should provide the least energy loss.? I think wheels
wobbling on axles would be a major concern.

Nice to hear it will be a 930? ;-)

-----Original Message-----
From: pkrasusky at ups.com
To: djdawson2 at aol.com; s-car-list at audifans.com
Sent: Wed, 14 Jan 2009 2:20 pm
Subject: RE: [s-cars] alignment Q

?

I would think toe causes more scrub

?

if camber scrubs... is it better than the full friction of the wheel 
surface area created by having zero camber?? Just wondering 
aloud.

?

Thanks Dave - good to hear from you btw...

?

-Paul

  From: djdawson2 at aol.com 
  [mailto:djdawson2 at aol.com] 
Sent: Wednesday, January 14, 2009 4:19 
  PM
To: Krasusky Paul (WQQ2PXK); 
  s-car-list at audifans.com
Subject: Re: [s-cars] alignment 
  Q

I can speak to 
  camber...

Zero camber would be best.? Any camber causes a 
  "scrub."

-----Original Message-----
From: pkrasusky at ups.com
To: 
  s-car-list at audifans.com
Sent: Wed, 14 Jan 2009 1:23 pm
Subject: [s-cars] 
  alignment Q

NAC, in fact it's a Porsche.

So The Boy insisted we make a 930 (of course) for his inaugural Pinewood
Derby 

this year - could he pick a more bulbous car?  Oy.  We're nearing completion
and 

ready to mount wheels.

Question for the Geekdom here - what is the 'fastest alignment' for a car
that 

only has to go down a straight hill?  I'm thinking maximum negative camber
(to 

decrease wheel surface friction on track) and zero toe - F&R.

Am I right?

Also - rules state cannot add bearings.  I just got the genius (I think)
idea to 

separate the wheel from its integral hub via a cut, and then glue the 'hub'
onto 

the car, polishing both contacting surfaces of wheel / hub.  Think 1) this
would 

be effective and 2) think it's legal?  We're not 'adding' anything and using

what's provided.  I do have a note in the Cubmaster on it, I can pretty much

guess the reply of course but figured I'd ask anyway.

Any other hotrodder tricks appreciated - we're already polishing the axles
and 

wheels and hubs best we can, using graphite lube, etc.

Insight appreciated - by Tyler 8-).

We pretty darn well nailed the 930 look - esp. the rear flanks and profile,
and 

front nose.  Unfort. rules dictate must use OE axle locations and then they 

limit max width, result is a 930LWB.  Hindsight would have me approach the
front 

flares different and run them further into the doors - next time.  And the
front 

wheels are so close to the nose our ride height is more Rothman's 959 than
930 

(maybe I should strip the Guard's Red and go with the Livery heh heh?) as 

tucking the wheels any more up would hit them into the headlight area.  Ah
well.

But it came out pretty darn kewl.

TIA!

-Paul

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