Solid front axle mounting options

[JimL]

Wasnt it a stub axle that snapped off John Goodmans Lakester in Australia?

Memory gettin' dim, thought that was in the Thunder Down Under movie but cant remember where I put the tape.

[lsrjunkie]

Stainless, The reason I was using your picture was to illustrate the tube coming through a flange. Probably should have been a little more specific. As for the frame rails twisting I was thinking about a bolt in crossmember with a drop bent into it. Similar to Dyno's roadster picture. Hopefully that'll clear things up a little.

[Stainless1]

Junkie, that sounds feasible, would the drop be better going forward instead of down, don't know how much room you are working with but you need to aerodynamically hide everything you can.  That is why we cantilever so much, the suspension and the doubler are inside our 24 inch wide body.  If you are thinking of a 3 piece axle, with 2 pieces welded to the frame and the center section bolted in I think you have a working idea.
Make a drawing, take a pic of it and show us, then send it to the committee chair for official Okidoki 

[ggl205]

"after I got the scrub radius improved"

There's a comment more people should listen to.

OK, someone needs to offer solid proof why scrub radius ehances straight line stability. I used to modle road racing suspension where scrub was vary important for turning but could find little to no kinematic value in a straight line. I do suppose one could get scrub very wrong and see a negative effect but you would really have to work hard at it.

Also, what broke on my solid axle was the point of attachment weld between axle tube and plate. There was weld undercut present and if we had raced longer, the other attachment point would have failed for the same reason. Lessons learned.

[Stainless1]

While we are in the lessons learned mode... That axle in my pictures broke... again... lesson don't weld around a tube.... My ME buddy said I just moved the load path and actually concentrated the load with the doubler., promoting a failure.
So I built a new axle, 4130 this time, 1/4 wall, no welding between the kingpin holders, it is clamped to the suspension. 

John, update your profile... you are my neighbor now... you and Toto...

Scrub Radius.... Ours has always been 0, because we built it to hide the kingpin from the air.  So I don't know.  How about it smart guys?   

[SPARKY]

Scrub radius and caster make for weight jacking the car--- any time you turn the steering wheels---there is a reason "roadster herders" try to shepherd their rides down the track with very little steering wheel action

I now run 0 scrub with 3 degrees caster---now have very little change on the weight scales with steering inputs.

[ggl205]

Scrub radius and caster make for weight jacking the car--- any time you turn the steering wheels---there is a reason "roadster herders" try to shepherd their rides down the track with very little steering wheel action

I now run 0 scrub with 3 degrees caster---now have very little change on the weight scales with steering inputs.

I should have read previous posts before asking about absolute need for zero scrub in LSR cars. JimL gave a good explanation. It all depends on what the car needs.

Zero scrub is good no matter what you race but I actually used a little negative scrub in my Tiga Sport 2000 sports racer. A little negative scrub actually gave me more stability and along with about 1/16" toe out, the car was very stable under hard braking and turned in well. But given the small amount of steering input LSR cars experience, any weight jacking is almost not measurable (at least I can't. I use WinGeo3 to model suspension changes before cutting steel). That said, we used to increase scrub (positive) in go karts to lessen dynamic weight transfer, if excessive oversteer was a problem. Not so coincidentally, all these things worked on more sophisticated suspensions as well. My lakester used off the shelf front dragster spindles and wheels. I would like to say I measured scrub but didn't see the need, especially given the 12 degrees of caster the car enjoyed. With that much caster, the car nearly steers itself if aero is good.

John

[Avanti Kid]

For 15 years I have used a custom hot rod roadster solid 4" dropped axle bolted to the frame on my Avanti, it has 17 degrees of caster and 1/8" toe-in and has been very stable on dirt at El Mirage at 182mph, and good on salt at Bonneville at 216mph and very easy to drive, but some years when salt is too rough had to abort the run at 175 mph, front end of car was bouncing off the salt about 6" or more. This was the event when John (president of club) from the ECTA was killed in his race car. Later if I want to my normal Studebaker front end assy, can be bolted back in place. Rich Manchen did my axle installation, I love the fact that the aero-load on the front of the car does not change at high speed.