I'm using a hoop steering arm for my A build, and I'm also using a cowl steering setup, BMW 2002 box. The build is a 28/29 A highboy coupester. Currently, the hoop is stock from Speedway, and the pitman arm on the box is stock, too. There's about a 7" gap between the lateral height of the bottom of the pitman arm and the hoop on the backing plate. I figured I'd lengthen the pitman arm by 4" or so to make up over half the difference, but I also need to raise the mating point on the hoop. In essesnce I'd be using a dropped steering hoop, just flipped. I've never heated and bent anything like this, and seeing its from Speedway, I have my doubts as to its ability to withstand it. My question is, can I use a dropped steering arm usually meant for the bottom of the backing plate, on the top? The arm on these are pointed towards the back of the car and are meant for a standard cross steering setup; however, I thought I might be able to cut the arm portion off and move it to center of the arc...make sense? I can obviously get forged one, so welding it back shouldn't be a big whoop. I haven't found any stock 3" drop hoops, hence why I'm thinking about this.
I'd just get some 1/2" rod, bend up the hoop you need, thread the ends or weld on some 7/16" fine thread bolts, weld in a tapered eye and a gusset and be done. I have successfully heated and bent those spedway hoops into shape before, but with how much height you need, I wouldn't bother.
Whoa.. didn't notice that part! yea adding 4" to a pitman arm is probably going to result in some squirrely steering!
Well, ***uming the pitman's default position is perpendicular to the ground, wouldn't lengthening the arm only change the amount of rotations on the steering wheel needed to achieve the same amount of turn? I dont really have a choice on lengthening the arm, unfortunately :/ EDIT: REVERSE that....it would make it "quicker" to steer....too "quick" would likely result in the aforementioned squirreliness....but where's the breaking point in length added to squirreliness resulting? Also just read in the "book" to remember to make the drag link parallel to the bones to avoid bump steer. That should cut off 1-2" of length I thought I'd need.
You're quickening the steering by lengthening the pitman arm, for the same input on the steering wheel, the end of the pitman arm is travelling further when its lengthened, and "in turn" pushing the wheels further. I would start with a taller hoop and see where that gets you before making drastic changes to the pitman arm. The limited suspension travel of an early ford will often allow you to get away with imperfect geometry. Hell they weren't perfect from the factory.
Did you consider remounting the box a bit lower in the cowl? Or is it in the "perfect spot" steering wheel wise?
Yeah, good idea...I'll try the raised hoop/arm @ the wheel first. With the under-the-floor MC/pedal setup, it's kinda at the sweet spot at the moment.
Could always whip up some crazy concoction with some gears, or sprockets and a bike chain that lowers the pitman arm, but keeps the box in the same location. . . then hide it in the cowl, under the kick panel. I probably wouldn't do it myself (lol) but it's an idea. Or get some 1/2 rod like Andy suggested and do the Rolling Bone style hoop.
Can you compared the BMW box to say an F1 box to see how many turns lock to lock and the pittman arm stroke ? there may be a chance you could make it longer. Just an idea. JW
From what I'm reading here on my break, it's 3.5 turns lock to lock....can't find anything on the stroke.
If you make your new hoop longer than stock it will cancel out some of the added length in the pitman arm. Your best bet is to mock it all up and try it out, e.g. clamp an extension onto your pitman arm and make a steering arm out of sheet-metal and try them out with different lengths and bends till you get something that clears everything and has a good ratio. As long as the wheels are off the ground you should be able to run the steering box through its full range with the temporary parts.
You know you could do something like this for your steering drag link. http://www.jalopyjournal.com/forum/...79&highlight=lakester+or+dirt+track&showall=1
Just because the draglink has a jog in it, it doesn't mean the geometry it fixed. Also can you give us a good sideshot of the car so we can all see how far it's off?
I don't think there would be any drawbacks at all. As long as the drag link would not twist around when pushed or pulled, and as long as it was made from strong enough tubing to aviod flex. The whole point of the jog in the drag link is to avoid screwing up the geometry in the first place ! If the pitman arm is not lengthened and the steering hoop on the spindle is OK, then all that is needed is a way to make up the difference in the vertical height between the two. The jog in the drag link would do it. If I'm not mistaken that is what he is trying to solve.
If thats all you're after, why aren't you just running it straight from the pitman arm to the steering arm? Moving the steering arm up and/or the pitman arm down will affect your steering geometry. I just don't see what you're trying correct. Is the piman arm lined up or close to the rear mounting point of the radius rod? Is your radius rod and draglink at very different angles that will cause bump steer?
I have about 7" of discrepancy in height from the bottom of the pitman to the top of the hoop at the moment: And, so you can at least see the angle of the front bones (don't have a side pic of the driver's side handy):
I have about 7" of discrepancy in height from the bottom of the pitman to the top of the hoop at the moment: Ok. What angle are your bones running at? Your draglink should be parallel to that, not the ground. Your draglink needs to swing in a simular arc as your bones.
Can I suggest running a string from the pitman arm hole to the steering hoop hole and seeing what your geometry looks like?
It's a little faster, George. I've used BMW boxes since the '70s, preference was / is the Bavaria non-power. (bigger box, long secter shaft) I always made a pitman arm from 5/8" plate, new arm 6.5" center to center, and the familiar 'safety-pin' hoop steering arm. Little faster, much more drivable than that blasted P&J Mustang with its 4.5" pitman arm and 6 turns lock to lock...LOL
So I checked the angles of the bones and the draglink. The pivot point of the bones is about 5-6" behind the center of the pitman arm. The bones are at approx. 7 degrees, the draglink would be at about 15-16 degrees. That doesn't sound good based on what I've read. Posted from the TJJ App for iPhone & iPad
Whats needed to get a grasp on this issue is a drivers side pic with the wheel removed and drag link of sorts in place.The angles you mentioned don't sound to good.You will get bump steer with this. As for bending the drag link,this can not help as the centre of the link remains the same. JW
Take your string from the hole in the pitman arm and bring it out to where the steering arm is and bring it up in height until the angles are real close. That's how high you need to bend up your steering arm to get things right. Not too much work at all really. Much like the picture of the bent steering arm earlier in the thread.
Hey guys, my angle math was right. The draglink is about 15-16 degrees, and the bone is about 6-7. Here's the best pic I could get in the garage.... Posted from the TJJ App for iPhone & iPad
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