Hot Rods Cowl Steering . . . just stop !

YEP!

 

Sure, pretty sure that is a Keith car not A Vern car

 

Question for the geometry experts.
Thoughts on this set up.
The upward curve of the split bone is interesting.
Good/bad/ no effect?

 

The geometry works off of the pivot points - the structure in between the pivot points can bend around in any sort of configuration, but the pivot points rule.

 

So this will set up would not cause bumpsteer?
Or at least not increase the chance of it happening?
I like the look. Generally that means a problem. seems like function often overrules form.

 

To eliminate bump steer on that old racer the drag link pivot needs to be in line and distance with the wishbone pivot. Seems the wishbone pivot is 6 inches too high. Still got bump steer (possibly).

 

Beat me too it...

 

The attachment point of the drag link to the pitman arm is not in line with the pivot point of the wishbone. There will be bump steer. According to Mr. Geometry

 

Any upward movement of the front axle more than a couple of inches will have the radius arm making contact with the steering box shaft/pitman arm.

 

The front set up on this probably never traveled much farther than that.


I was thinking the same thing.
Has a little clearance.
May check to see if I can tell if it has ever touched next time I see it.

 

Wow, check the scrub radius on that setup!

Not to mention the Ackerman angle.

 

Yikes! Thinking bump steer was nothing compared to steering through that scub

 

Yep.
Considering it doesn’t have front brakes those tiny wheels could have been moved in somehow

 

No, just a setup like Bishop and Tardell did for the blue roadster. Like I said, I got the project with the Ford box and column already

 

That might explain the crash test dummy wearing long johns...or not.

 

Never seen front brakes on a tractor before. lol

 

The more I see of vintage racecars of "the good old days" the more respect I have for those guys who drove them hard.

 

Obviously the car must have been raced at some point in it's life. Whether it was a track champion or not we'll probably never know. Very few were built back then to just sit in some barn waiting to be discovered. Builders were experimenting. They found out what worked, and changed it if it didn't. Probably didn't really give a shit what the local 'know-it-alls' thought about it down at the local diner over their coffee and donuts. Modern day race car drivers would shit their drivers suits if they had to climb behind the wheel of the old board trackers, Indy or F1 cars of yesteryear.

 

It amazing some of these old rides even made it around the track once.
No one knows what stage of learning the car builder was at or where he may have ended up.

 

Sometimes when I watch the old film clips of those circle track races I study not the front runners, but those at the back of the field trying to run nearly the same lap times while being pelted with mud and stones, breathing in copious amounts of dust and fumes, and driving on slick dirt or boards sodden with the drippings of what were tantamount to total loss lube systems on skinny tires likely to burst as not before races' end.

Hats off to you Boys...

 

Now that you got out attention can we see the rest of the car? Maybe a thread of its own would be in order. Quite a collection of parts in the front end alone. Austin / Bantam shocks, narrowed A front axle & brakes, Model T tie rod and steering arms Bob

 

https://www.jalopyjournal.com/forum/threads/neat-old-survivor-race-car.1218387/#post-13913448
I did. Got a little interest.
It belongs to my former boss.

 

No one has commented lately on cowl steering, and I just came across a picture in Hemmings of an early 60's Indy Roadster that illustrates one way to minimize, if not completely eliminate bump steer. If you could see this car without its body, you'd see that the idler arn is just slightly ahead of the rear pivot point of the right side link locating the axle. And the front drag link is the same length end to end, and parallel to it. This forms a parallelagram known in engineering texts as a 4 bar linkage. At any instant, the rear pivot points are the fixed pivots, and the front are the moving pivots. If the bars are the same length and parallel, they swing the same arc.

Lots of extra pieces to have flex, wear, bolts loosening, etc. So is it worth it?

 

That is what I plan to do on my Indy replica - change the one-piece drag link to a two-piece by adding an idler arm midway.

 

It will help but not eliminate bump steer like on a 4 bar front setup. I have a similar setup on the Whatever project, a hairpin on the passenger side. When the axle moves up or down a hairpin or split bones makes the axle roll, if you will. Not much, but a bit. So unless the split point of the drag link lines up with the pivot point of the split bones, there will be a difference in the arcs they travel thru.

I know, much better than the looooong drag link but still not perfect. Those old Indy car builders really knew their stuff. And by the end of the roadster era, had really taken the design to a very advanced state.

 

Do torsion bars add anything to this discussion?

 

It depends. If the bars are part of the locating system, think Watts link on the side front to back, then the axle center follows a straight line for the usable portion of the front suspension travel. However the axle also twists around its centerline. This means if the wheels are straight ahead, the steering arm also rolls. But the steering box isn't being turned. So the drag link swings in an arc around the rear rod end, and the steering arm is trying to move front to back. Causing bump steer.

Now if the axle is attached by a 3 or 4 bar system, the axle will follow a path described by the 4bar system. In these setups, the torsion bars either rest on top of the axle on rollers, not affecting the travel, or some sort of shackle again not affecting the travel.

If I was better with computers, I'd post a couple of drawings of systems that do and don't affect steering. I've been ruminating over this since Mr. Eastwood first posted this thread, and he's correct. The typical long drag link causes bad bump steer. It can be gotten around with a lot of extra linkages, so the question is, is it worth the effort to make a system with no bump steer but has lots of opportunities for slop, breakage, deflection, etc, or use cross steer setups as he's recommended.

BTW, my choice was cross steer, and I have a Schroeder champ car steering box that has only 10 laps on a dirt modified back in the 70's. And it would have been easy to use if I wanted bump steer problems.

Just my opinion, like he said don't hate on me! Pm me if interested in some possible ideas.

 

I have had this thread saved and earmarked to read for quite a while. I have just finished it in it's entirety, all the good info and all the horse shit. Thank you very much to @Pete Eastwood for his knowledge and insight, and to @dana barlow , @Ned Ludd , @HotRodWorks and others for painting the correct picture. Lots of good information for anyone willing to take it on board.............

 

Something that gets loss in theses discussions about bumpsteer is the amount. On lightweight cars with minimal axle travel ( in some cases perhaps 1 1/2" total up & down ) bumpsteer may be 1/16" or so , Are you going to feel that ? It takes place in milliseconds , in all likelihood , you won't feel it & it will have such a minor effect on handling , its not worth considering . This is not speculation , its real results experimenting with my T with hairpin locaters. Another hyped item is track bars on the front end . I think much of this is advertising driven by some folks to sell THEIR parts or systems . I'm not saying don't make every attempt to limit
Bumpsteer , just that the amount should be considered .

 

The subjects of suspension and steering are far more encompassing than most people realize. The working principles are grounded in basic geometry. There is a "right way" to do things, and the further you stray from this, the worse the result becomes. Absolute zero bump steer is rarely achievable, but close to zero is usually not too hard as long as the geometric principles are accepted and used. As you imply, a little bump steer is not tragic. What is tragic is the attitude of some to not make an effort to get their head around the correct information, even when it is handed to them on a plate. The theory does not change to suit anyone's particular opinion. Bump steer geometry is very basic stuff. Their is more to learn about suspension and steering than you will fit into a lifetime if you really want to get into it, but it is a progression of principles. If you don't take on board the basic stuff, you can't possibly delve deeper. It is very interesting stuff if you get right into it. And, by the way, the Panhard bar (or track bar as you call it) was not invented by a guy that needed a way to get rid of some extra steel tube. They work.... but only if you get the geometry right.

Again, thanks @Pete Eastwood and others for offering the basics for all (or some) to learn and use.