I'm having issues with my steering on the roadster I'm building, I'm using a mopar box with the shaft turned down and a sprint car torsion bar slid over it with the splined end on the outside of the cowl, then I'm going to use a torsion bar arm on the for the drag link to hook on to and run to the front wheel. The problem that I'm having is it is very hard to turn with weight on it, how do I figure out what length arms do I need at the box and the steering arm to make it easier to steer? It is so hard right now that I can watch the axle try to twist and it will break my spot welds before the wheel turns. Seems like to me I need more leverage at the wheel but I have been told that shorter arms would be better. My arm on the cowl is a mock up so I can figure out where the hole needs to be on the arm before I machine the new one, so I can move the hole up and down on it, but I'm trying to keep it low to make the drag link run with the hair pins. Any suggestions welcome.
Mine was not that long (as yours in the pic) maybe 6-7" C to C. It would seem that if you have a longer Pitman, you would have more leverage from the steering wheel, thru the box, and out to the tires.. "BUT" what you end up having is the tires and their steering resistance is fighting against you, and using that long pitman's length against you. (my 2 cents)
There are a lot of things to consider besides length of Pitman arm. Weight of engine, width of tires, steering arms length and caster angle are just a few.
How straight does the drag link have to be to the hair pins? I can shorten it but I thought it should be pretty much in line Posted using the Full Custom H.A.M.B. App!
The problem that I'm having is it is very hard to turn with weight on it, how do I figure out what length arms do I need at the box and the steering arm to make it easier to steer? with a long pitman arm, you trade force for distance. The long pitman arm's drag link hook up point will travel a great distance, much greater than the steering arm could ever use - the cost of that distance is you need to apply greater effort. The other side of your current situation is any force coming from the road back thru the steering wheel is likely to break your arm. A longer steering arm would have the opposite effect. It would be very easy to turn, but the distance the hookup point needed to move would increase.
My 2 cents and I'll probably take some flak but it's dam hard to have the steering box where it needs to be and have any room left for your feet. I went through all this on my rpu and had the box mounted too high. With everything the correct length, the drag link angle would have been a bump steering monster. I studied picture ofs some famous cars like Doan Spencer's and came to the conclusion he must of had Gisha girl feet, not 13s like me. I cobbled mine up with a chain and sprocket drop to a second steering shaft and got all the geometry right but it's too many parts and I can't get all the slop out, at best about 1/8th turn on the wheel. It's all coming back out and a cross steer going in.
they make a 2:1 or 1.5:1 box, for ovaltrack stuff. You can use it to speed up or slow down the ratio, on a stock box. http://howeracing.com/p-7900-howe-basic-steering-quickener.aspx That would allow you to mount the box higher, with a long pitman arm.
Yep I moved the drag link up on my arm and fixed the problem now the drag link is at way to much of an angle.. back to the drawing board. .
31 /Vicky with a Hemi nailed in his post. It requires a lot more umph at the wheel to move the end of that long arm than it would take on equal length pitman and steering arms or if the pitman arm was shorter than the steering arm. I can't remember what grade we learned about fulcrums and levers and how they work but the theory applies here.
Could you fab up a steering arm that took up some of the distance without being too "up there" to cut some of the angle? Not all of it but maybe enough to cut the angle in half?
Longer arm at the wheel, Shorter arm on steering box. Move steering box as low as possible to get the drag link in line with the hair pin and still have room for your feet. Or the other option go to the doctor to have your feet shortened LOL. This is a persistent problem with cowl steering. Jim Ford
If you can make it better engineered by moving box down on frame or close,you can use a normel size arm. I just hate cowel steering,to start with it really screws up the look of cowel,always looks to me like builder didn't know how to build a streetible hotrod. But no matter what arm you use on cowel,the bumpsteer is going to be poor to very bad. Arm at box needs to be only a little longer *then the arm your using coming off spindle. How much longer depens on how EZ you wish it to steer. The close to same size the two arms are=the EZer it get.
From studying Doan Spencer's roadster I've learned why the steering arm is shaped the way it is and why in its time the steering arm was such a big deal. Wtf its just a steering arm right? Here's another way to get it clean. Probably wont work for you at this point, maybe on the next one
Thanks. I like the looks of the cowl steering that's why I'm building It that way, I will just have to lower the steering box. Posted using the Full Custom H.A.M.B. App!
If you use a long pitman, you need a long arm on the spindle. This is using a regular ratio box from a regular car like that Mopar. So, try a longer steering arm on the spindle (mock up a quick and dirty one) and see how it works.
Just try and stay within sensible limits if lengthening the steering arm at the spindle. If you're going to attempt to get the proper ratio with the 12" pitman arm (!) make sure your steering arm doesn't place the drag link in a 'scraping' situation with the radiator shell... Seriously, bend yourself a steering arm (upward) that will level the drag link with a 7" center to center pitman arm. Simplest solution.
Quick question to the OP: - You say "with the shaft turned down and a sprint car torsion bar slid over it ". How are you connecting the torsion bar to the steering box shaft? Picture looks like just a bolt going through. Can you provide more info & pictures? I like using a splined torsion bar to extend the steering box shaft and then using a clamp-on pitman arm, but I'd like to make sure the torsion bar and steering box shaft connection is bulletproof.
Yeah its going to be pinned and tig welded, I got the idea from the cars jokerr has built. . Posted using the Full Custom H.A.M.B. App!
Here is my set up. Duster box with a longer (maybe about 10+") arm connecting to an idler arm which gets the forward drag link at the correct angle relative to the hairpins. Works slick- no bump steer at all, very easy to turn. Here is the car in profile. Setup still appears like a standard cowl steering setup.
Hammeredt,has a neat n fairly clean way to get around the bumpsteer,thats a neat looking T-coupe. But every time you add a joint{in that case 3extra places to have some slop at some point,its not real good in the long run. Some seem to like cowel steering look ,just cuz they saw it in this or that rod,but repeting a bad design is not something that should be done,no matter how manytimes you saw it. Bad engineering is still bad,an I don't think it is cool to copy,if you know better,but thats me.
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