I purchased a reversed corvair steering box on eBay new. Anyway, installed it with cowl steering on my coupe. The pitman arm on the cowl from center to center on tie rod is about 5 1/2”. The arm coming off brake drum is 4 1/2”. I’ve got about 1 1/2 turns on the steering wheel lock to lock. Seems like it’s way too quick for the street. When I look at all the corvair boxes for sale, looks like all have the same ratio 20:1. Could I have some how gotten a box with a different ratio? The box I bought looks just like every other one I have seen for sale. Thanks in advance, Ed Sent from my iPhone using The H.A.M.B. mobile app
I know there are quick ratio sprint car boxes, but don’t know if corvair had them Sent from my iPhone using The H.A.M.B. mobile app
Steering ratio is determined by two factors— steering-linkage ratio and the gear ratio in the steering mechanism. The relative length of the pitman arm and the steering arm determines the steering linkage ratio. The steering arm is bolted to the steering spindle at one end and connected to the steering linkage at the other. When the effective lengths of the pitman arm and the steering arm are equal, the linkage has a ratio of 1:1. If the pitman arm is shorter or longer than the steering arm, the ratio is less than or more than 1:1. For example, the pitman arm is about twice as tong as the steering arm. This means that for every degree the pitman arm swings, the wheels will pivot about 2 degrees. Therefore, the steering linkage ratio is about 1:2. Most of the steering ratio is developed in the steering mechanism. The ratio is due to the angle or pitch of the teeth on the worm gear to the angle or pitch on the sector gear. Steering ratio is also determined somewhat by the effective length and shape of the teeth on the sector gear. In a rack-and-pinion steering system, the steering ratio is determined largely by the diameter of the pinion gear. The smatter the pinion, the higher the steering ratio. However, there is a limit to how small the pinion can be
I understand the basic principles of leverage based on length . I don’t really think that’s my problem after looking at the length of pitman arms used on existing hot rods I’ve seen. I just disconnected my tie rod and I have about 5 turns lock to lock on my box when it’s not connected. Wondering if this box is 20:1 or something quicker. Like I said I bought it on eBay a while back, and unknowingly bought a quick ratio Sent from my iPhone using The H.A.M.B. mobile app
I did one on my 34 three window coupe in the seventies and it was great. It was a cast iron one and it took a ford 30s splined pitman arm . The only thing I had to do was file the flat spots to center the box and have the arm straight down. I welded a plate on the inside of the chassis and had it coming out of the stock hole. It steered like power steering. I put a steering damper on it to give it some feel. Just my way .
O.K., disconnect your pitman arm and calc the degrees of turn you have on the sector shaft with the 5 turns of the mast shaft. (steering wheel). Or simply disconnect the drag link at the pitman arm, marking the sweep (total length of movement) from front to rear. (easiest way to do this is with a plumb bob; string tied thru pitman arm link bore, attached to a pointed weight, above a yardstick on ground running parallel to direction of 'sweep') By the way...What kind of spindles do you have? If early Ford, just what kind of steering arm up there is 4-1/2" long???? I've never even heard jokes that short...
Not having ever done this before, I copied this after seeing it done on quite a few cowl steering applications. Measures appropriately 4 1/2”. Sent from my iPhone using The H.A.M.B. mobile app
Going to take your advice and redo the spring mount, wasn’t very happy with the way it turned out, and like most of the stuff I do on this project, I wind up re doing till it’s as good as I can get it. I found my info from when I bought the steering box on eBay, and it was listed with the same part # as all the other boxes the equipment dealers sell, so I’m pretty sure it’s 20:1 like all the others. Plus I have 5 turns, lock to lock when it’s not connected to anything, and the pitman arm swings real close to 1/4 of a complete revolution. So if I could turn the wheel 20 turns, it would complete a full circle, thus it would be 20:1. Once I redo the spring set up, I intend to extend the arm on the front wheel, and that should slow it down to where it’s streetable. Thanks to all for input. Sent from my iPad using The H.A.M.B. mobile app
You also want to put a jam nut on that Heim Joint where it's threaded into the steering link or it will soon be wobbled out and stripped.
I like that 'wrap' bracket perching the spring shackle. This is a critical spot that sees failure from lesser 'well planned methods...' As SheepDip pointed out, any time a long threaded shank is used at the end of a link, put a jamb nut on! It keeps constant tension on threads otherwise destined to compress-and-pull, over and over. (Fixed a few 'cool R-Rods', so I've seen it.) Looks like you're on the right path...Yeah! I just got my frame with title for my tub. I'll be joining you at the assembly stage!
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