cowl steering geometry questions.

i think that 40's were the longest ones with the spring over axle. the 41-48 were probably longer but had the spring in front of the axle and also had a double bend in them about 8" behind the axle.

 

Keep in mind that we usually have half the suspension travel compared to a modern street car, so bump steer is not a big concern. Bump steer increases with suspension travel. When you get your car low, you will slow down for the bumps. Problem solved!

 

No bumpsteer here, and the long pitman arm makes the ratio just right.

 

That car is F**king beautiful! Great Job!!!

 

I agree, my Touring steers pretty good with less bumpsteer than my 2000 Ranger!

Side note, I did use A bones and they are aa tad short. But, they still perform well. They are 8-10" shorter than my draglink. If i had longer bones I would have used them.

 

That's why I prefer to mount the steering gear first.....then I build the 'bones to the length that works with the length of the draglink.

 

I'm using one that works well with my small Chevy powerplant. It's from a search function.

 

Would you mind elaborating on what was wrong with your friends steering set up? I may already have known that his set up was bad, but I also may not have known.

 

i have a schroeder box for my roadster. The plan is to use a long pitman arm to achieve better geometry. A steering ratio reducer may be used to slow the steering.

 

His car has several issues that all add up to his near wreck. First and foremost he was exceeding the posted speed limit.
Second- his car is 100" wheelbase.
Third- too much air pressure in the front tires- 6.70 X 15 Firestones with 25psi, the car weighs 1700 pounds.
Fourth- improperly adjusted friction shocks
Fifth- too many leaves out of the front spring
Sixth- worn shackles
seventh- 3 degrees of caster
eigth- no toe in
ninth- worn out steering box with near SIX turns lock to lock

he hit a "flaw" in the road at high speed. Bet you can imagine the result.

 

'35 to '48 all had the spring in front of the axle. I'm using '40 split 'bones in mine, they're 40 3/4" before trimming or welding in the bungs. Add 2" to 3" for finished 'bones with the tie rod ends in.

 

Thank you. I don't claim to be an expert, but I have to believe the low amount of caster and toe in wasn't helping anything stay on the straight and narrow path.

 

bump steer was the beginning of the ride, death wobble was the end. The car was tossed around violently enough that the frame cracked.

 

mopar,

how right you are. i had completely forgotten that i had cut off the spring mounts in front of the axle on my '40 bones. guess i was thinking about 40's being the last bones without the bend right behind the axle.

guess i'll slink off into the woods out behind the barn onw...

 

It was a simple question.

 

I have been reading lots of post on cowl steering, what box to use or not, bumpsteer vs no bumper steer theories but there was some good dialog in this post so I am going to bring this back from the dead as I have a question

what length do most of you consider to be adequate for a cowl steer. (I hear longer is better but how long are most of your bones or hairpins on your cowl steering set ups.

(not sure what the length of a model A wishbone is vs a 41-48.. I have a set of split bones but not sure what year and i am trying to figure out whether to use them or go with hairpins..

 

Boones, the picture of the yellow speedster in this thread is as close to "right" as you'll probably ever see regarding that geometry...

The arc length and angle of the drag link and wishbone should match as closely as possible. As far as what is "adequate", can't help you there...

 

Wow a thread thats 4 years old brought back to life! Its always good to get a refresher on cowl steer set-ups. If you have ever seen the Rolling Bones cars their cowl steer is about dead nuts right on. I to am going with cowl steer and different views on it always help!

 

I think most would agree that have the two travel in the same arc is the best.. set ups like the Rollin bones cars being parallell work I think because they have long wishbones and steering rods. but for those that are running cowl steering, how long is your wishbones and steering rods..>> my wishbones measure 36" from mounting point to mounting point but see speedway sells a pair that are 40".. so what are your length.

 

I don't know why Hillbillyhell chooses to be "like that" about his tech post, but I can fill you in. I wanted to copy his setup, so I spent a BUNCH of time at the salvage yards, and with the Hollanders, to figure it out. In his tech post he originally mentioned that it was from a Ford Ranger,the little 80's and 90's truck, and then later changed his answer to the full size 60's and 70's 1/2 ton Ford Ranger.

The box he used in the tech post is from neither. It's from a 80's Mazda. Versions of this box can be found in 70's Couriers with full length input shafts attached to the box, up to at least '96 in Mazda B series trucks.

I scored a box cheap, did the mods, made the parts, and installed it in a 27 coupester. Works great. Excellent tech

 

Mine are about 40" from center to center. I think mine are '42 wishbones... I think. They are the non-stepped type.

And I agree... The closer the bones and drag link are in length, the better.

 

I'm using model A bones with a cowl steer setup and they are short, i made mine longer by spinning up a tapered extension and welding it in. They are not finished here but you get the idea.

They are 46" long to the centre of the joint

 

I'm not surprised !!!

 

scooter and Langy, thanks for the input,

how about others. I was hoping folks would read this and post but I might have to start a few thread with a question in the title...

 

Boones.

Sitting inside at the moment so I don't have a measurement for you but mine are '48 bones with equal length drag link, running parallel. It drives nicely.



Pete

 

The only real way to get perfect geometry, is with SIMPLE geometry.

The theoretically correct way, is to fit the steering ball joint on the spindle arm at the exact same effective height as the front of the wishbone. Nobody does this, in fact it may not even be possible to do, unless you run bat wings and hairpins or a four bar.
Once you achieve that, the front of the steering push pull rod, travels in the exact same arc, as the front of the wishbone, when viewed from the side.

At the rear, we place the ball joint on the pitman arm (of the steering box) at the exact same height as the rear chassis mounting ball joint on the wishbone.

The third requirement is that the steering push pull rod and wishbone must be the exact same length, pivot to pivot.
The steering push pull rod will always be the exact same few inches behind the wishbone, at both front and back, but the arcs at both ends will always be identical.

The idea is simple, it is usually just never practical to build it that way. The steering box always ends up needing to go in an impossible location. Or there are impossible interference problems at the front.

That is, unless you design and locate the steering box and linkage first. THEN fabricate your wishbone a suitable length, and fit the rear wishbone pivot to the chassis wherever it needs to go. Unfortunately that may not be too pleasing to the eye, or look traditional, but at least it will not be wandering all over the road at speed.

People usually design steering geometry ass backwards.
They completely finish off building the suspension, then try to figure out how to fit some sort of steering linkages to it. The result is often very bad, and there is then no easy way to fix it.

Start off with the spindle and steering box, the locations of which cannot really be moved. Fit the two pitman arms, and steering linkages up to it. THEN start thinking about how long the wishbone needs to be, and where it ends up on the chassis for zero bump steer.

 

striper, thanks and love your ride. when you find time, if you could measure that would be helpful.

 

I'm on my 4th cowl steer project and on each one the wishbones have been longer and been better, I'm sure going to the long bones will make this one work the best.

My last one used 40 bones

 

It really is that simple. Simple geometry.

Unfortunatly I thoughtlessly listened to the "they've got to be parallel" crowd when I built my first car, and it had horrendous bump steer.

Mind you, the steering links were fairly short, which only compounds the problem.

My hairpins were mounted fairly far inboard, at the rear, as I ran a tube axle.

I also used quarter elliptics, just to be different.....

 

cool thanks for the pic and the info!