This is my first build (I plan to make a thread with the whole project sooner than later) and I am at the point where I plan to put the steering box in permanently, but I wanted to get feedback before I do. I read a million articles, forum tech tips, and watched a million videos and I feel pretty confident I have it right. Any and all advice is greatly appreciated!! Here are the details I can think of: **All of my theory is based on an imaginary line from the center of the steering arm to the pivot point on a bracket permanently fixed to the bottom of the frame. -1931 Ford Sedan -Stock frame from the front to the rear just before the rear axle -4" dropped I-beam front axle (7* positive caster) -Reverse Corvair steering box sitting directly on the frame -Hairpin radius rods. The center of the axle to the center of the pivot point where they're attached to the frame is 34" -Drag link would be 26" if the pitman arm, some minor adjustments, is 90* to the imaginary line. The 8" difference is outside of the 10-15% someone mentioned is acceptable (not sure if those numbers meant my style of set-up). -Pitman arm is 5 3/4'' from center to center (although I will need to get one to bend around the radius rod while still keeping the stock distance eye to eye) -The column would be about 24-25*, but I'm ***uming I either need to move the whole box inward or just use an extra link to put the steering wheel where I would like it (I'd love suggestions for that too. The extra link seems easiest to make it all fit where I want) -Steering box is about as far back as I can go without interference from the cowl or firewall -Reversed firewall for space, which is about 3 3/4" from the end of the input shaft on the steering box (measured while using the planned set-up) -sbc -Not sure what exhaust yet, but I'd like some kind of header where I can uncap for noise/power or cap and run through some type of muffler About the pics: -The steering box is sitting directly on the frame -The bottom of the green tape is the imaginary line from the center of the steering arm to the center of the pivot point on the bracket attached tp the frame -The blue tape runs the angle of the pitman arm when its 90* to the imaginary line blue tape is 5 3/4" from center to center on the piman arm, which terminates perfectly on the imaginary line (green tape) -Black marker on the top and bottom of the blue tape is 5 3/4"
Your imaginary suspension line/tape should run from the middle of the spindle snout to the back wishbone joint. Looks like you are a touch high in the front. Knowing that, it seems your drag link will be very much parallel to this line. If the drag link was the exact same length as the wishbone, the geometry would be close to perfect. I think you are really close. If you can fit the drag link to the bottom of the spindle hoop, you might be a little better. Flip it and see.
That's a great idea, thanks! So if I understand this correctly, I can flip the ball joint at the front of the drag link so that it sits underneath the steering hoop and the castle nut would be above. I took a look and this would put that imaginary line from the center of the spindle snout to the back of the wishbone pivot point. The drag link is still shorter, but the wishbone and drag link would be on the same line! Quick question...the stock pitman arm is 5 3/4". Would I be better off getting a slightly longer pitman arm (if need be) or have the bottom eye of the pitman arm slightly higher than that imaginary line? Thanks again!
PLEASE , read the last line in the caption below the second picture . Perhaps that will keep some of you " experts" from proclaiming loudly & repeatedly ( with your hair on fire) about how critical it is trying to achieve perfection !
The hoop steering arm will have a tapered hole through it, so you need to flip the hoop over as well when the tie rod comes from below. Not really sure about the longer pitman arm. That might be something that could be changed later if you find its needed.
I didn't see it but what size steering wheel? That will affect your placement that you ask about. Also, it is highly recommended that you reinforce the eyelet on that hoop steering arm. Extra weld, brace etc....
I haven't figured out a wheel yet. I've been looking for some 40's or early 50's wheel. I will definitely put a gusset of sorts for extra strength on the hoop.
This was one of the articles I researched. It seems they are talking about the original wishbone style where the pivot point is under the car, but I don't see why this wouldn't work in my situation. I'm trying for the old "aim small, miss small" so that when it is all together I minimize problems. I've read some nightmare stories and those are the ones I'm hoping to avoid by following the proven methods. The last line is what gives me hope my p[planned geometry all works out!
I'm not sure the position of the wheel centre or the parallelity of anything has anything to do with it. The hoop joint, the pitman arm bottom joint, and the back wishbone joint should be on a line, or near as possible to, and the latter two as close together as practical on that line. The pitman arm bottom joint as it is now is above that line: to get it closer you'd want to raise the line, not lower it. Besides that, because the pitman joint and the wishbone joint are that close together, you'd have to raise the hoop joint a lot to get them in line. It should be easier to lower the pitman arm — or raise the wishbone joint. Or, as I understand from the original post, use a longer pitman arm, which should also give quicker steering (which I personally prefer.) The horizontality of the physical wishbone is purely visual; it's irrelevant for suspension geometry. The wishbone isn't a link; it's part of a complex ***embly which pivots as a whole. If you can live with a slight visual angle (or not — where will it end up with weight on the front end?) a higher wishbone pivot will give you more anti-dive under braking.
Big wheels like that do make it harder to fit everything in an early car. I prefer smaller, 14 or 15". In my GMC pickup I took an aftermarket wheel, cut down the stocker and grafted the 15" hoop to the factory center. You could do the same
The car is downhill a bit because it's on an uneven driveway, so I took a few measurements: The back of the wishbone is 8" off the ground, and the center of the front of the wishbone is 9" off the ground. The drag link is just sort of hanging in the back, so don't look at that. The engine/trans is in, so there won't really be any weight added up front. I'd like to keep the wishbone where it is bc it's final welded in. I couldn't move the steering box any further back, so I figure I can only play with the pitman arm length and make sure it's on the correct t line. (I agree I would rather have a longer pitman arm) So I guess the last part of that equation is if I measuring the line in the right spot? The steering hoop is 1 1/2" above the spindle snout and the center of the ball joint is 1 1/2" above that. The bottom edge of the green tape runs from the center of the ball joint to the center of the back of the wishbone (right down the path the drag link will follow) Thanks again!
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