Landracing Forum

Tech Information => Steering - Suspension - Rear End => Topic started by: bob on August 21, 2018, 10:58:14 AM

Title: caster
Post by: bob on August 21, 2018, 10:58:14 AM
what would be correct amount of caster, I know more is better for straight line stability, but how much is more, and is to much counter productive  thanks
Title: Re: caster
Post by: 7800ebs on August 21, 2018, 12:57:43 PM
I have less than 10 degrees as I remember..

too much and you will get a wheel wobble.. been there, done that

bob dalton
flashpoint
Title: Re: caster
Post by: Stan Back on August 21, 2018, 02:22:58 PM
We've got 13ยบ.  Never a wobble, but won't keep you out of the spin cycle.
Title: Re: caster
Post by: hotschue on August 21, 2018, 03:38:23 PM
Built axle 13 degrees (same as a funny car) machined spindle, hub and wheels to achieve "0" scrub radius.   You can just about take your hands off the steering wheel......
Title: Re: caster
Post by: bob on August 21, 2018, 06:51:19 PM
thanks for the input , sounds like about 13* is about right. I better not listen to my expert buddy who kind of knows about alignment, and not set it at 24*. dangerous combo.
Title: Re: caster
Post by: kiwi belly tank on August 22, 2018, 01:13:59 AM
There are lots of variables to the correct answer & that includes what your car is, what type of suspension (if any), what the other geometry of your front end is, how fast is it going & where,..........
  Sid.
Title: Re: caster
Post by: revolutionary on August 23, 2018, 09:39:40 AM
I built my spindles with 14 deg KPI and set the caster at 13. Ended up with about .5" scrub using 25" tires. Going to a taller tire I could take some scrub out, but I never felt it make any moves during SW this year.
Title: Re: caster
Post by: Bob Drury on September 07, 2018, 11:24:30 PM
  Back in the sixties most of the fuel dragsters ran 25 degrees + or - and when they pushed down to the starting line to make the tight U-turn to stage the wheels would flop over like some of the "Ladies" in Wells, Nevada.
  Enter the funny car era around 1966 with steel bodies and straight axles they ran darn near that much and into the early to mid seventies even with torsion bar suspension or coil over independant suspension, a lot of funny cars still ran a ton of caster. The results were often not pretty.
  I watched Twig Ziegler (who was one to back up reeeal fast) end up looking like a turtle after the wheels flopped on the Pizza Haven Plymouth Satellite.  It's pretty hard to look graceful when hanging upside down waiting for a dozen people to roll You back over so You don't break Your fu*king neck getting out.
  p.s.  How in the hell do I remember that when I don't even know what day it is anymore?
 

                                                                                     "One Run", out................................................ :roll: :-o :mrgreen:
Title: Re: caster
Post by: Stainless1 on September 08, 2018, 07:39:09 AM
One Run... it is easy to remember what day it is....if you remember there are only 3 days of importance to you... Yesterday, the last day you remember....Today, this is today, and Tomorrow, it is.... well tomorrow...  :roll:  :-D
Work on it, there will be a test tomorrow  :cheers:

Edit: I guess I should comment on the subject... we ran a flopper front on the Bockscar for many years... about 36 degrees, no scrub.  A couple of years ago I changed it to 12ish.... no scrub.... it is easier to back up, and we lost that pressure area in the steering that you could tell you were about to steer the car.
Title: Re: caster
Post by: floydjer on September 11, 2018, 01:48:45 PM
Might be worthwhile to place scales under each wheel and see what effect the various caster angles have on camber gain/loss and weight jacking.
Title: Re: caster
Post by: SPARKY on September 12, 2018, 11:55:17 AM
Costello runs 0  ZERO 
 I run three----

What we both are trying to do is not have steering inputs weight jack the car when you are down course---Caster with scrub radius definitely will induce the rear tires steering the car.
Title: Re: caster
Post by: floydjer on September 13, 2018, 07:14:31 AM
careful Sparky.....You`re getting dangerously close to agreeing with me.... :cheers:
Title: Re: caster
Post by: Rex Schimmer on September 13, 2018, 10:10:50 PM
Solid suspension cars, like Sparky's, are especially sensitive to jacking caused by wheel offset and caster. There is effectively zero suspension compliance and if the chassis is stiff in torsion, which Sparky's certainly appears to be, small vertical movements of a wheel can cause large amounts of cross chassis weight transfer, i.e. jacking. Pretty easy to understand why Sparky wants to minimizing caster and wheel offset.

Rex
Title: Re: caster
Post by: SPARKY on September 14, 2018, 01:22:19 PM
careful Sparky.....You`re getting dangerously close to agreeing with me...

And that would be a wonderful thing right  :-D
Title: Re: caster
Post by: manta22 on September 20, 2018, 04:44:43 PM
I run 7 degrees of caster FWIW.

Regards, Neil  Tucson, AZ