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collapsible steering column for 7 S2?


Timothy Keith-Lucas

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The solid steel steering column on my 1962 S2 scares me. Any frontal impact and that sucker is aimed at my  chest. I'm thinking of designing and fabricating a collapsible column, but am wondering if anyone has already got a design, or if there is a substitute column on the market.  Thoughts?

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It would be worthwhile with minimal weight increase. Borgeson double-D telescopic shafts could replace part of the column but it would rely on the driver's arms holding the steering wheel and the strength of the spokes as the column mount has minimal structure. The shafts should stay lubricated and also has a boot to keep the area clean. Oems do the same thing with an intermediate shaft. Miatas use injected plastic to hold the telescopic bits in position with no grease.

A greater effort would be a large flange on the shaft forward of the column mount (blocks the shaft from pushing through the chassis mount) and a diagonal to brace the chassis attachment (less easy to break/bend back). Again, another couple pounds added.

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I was able to update my S2 replica chassis to a later Caterham steering column to add just a bit of safety to the steering column. Probably the easiest option since it requires just the upper and lower columns and the clamping arrangement.

 

370849665_PedalBoxCover.thumb.jpg.6a94bc37cd694065c15052f3c4765058.jpg

Edited by 11Budlite
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Thank you muchly, MV8. I ran into no end of trouble mating the Borgeson shaft to my 9/16 shaft - adaptors are not available in those sizes and I don't have a lathe. I'm thinking of a 5/8" inch ID tube pinned to top and bottom stubs. I can get 12" of collapse from that. The available free shaft, from the splines at the steering pinion to the frame that mounts the master cylinders is (surprisingly) only 25". A collar around the shaft just below the mount for the master cylinders should make sure that it collapses, without transferring the  thrust to my hands or my chest.

 

Mr. Chapman certainly believed in simplification, but having the steering column anchored only at the steering pinion is impressive. Release that clamp, and the entire shaft slides out the back, with only a bend in the steering wheel as it goes over the seat back.

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Did one of these on my 7. Used a Triumph/Lotus Elans setup modified to fit by extending the outer "tube" part of the shaft. And while you are at it, get the solid type column to rack joint. 

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OK, I believe in simplification, too. Two square tubes, a 1" with an inside square of 0.76", and the other with an outside 0.75". Weld on the ends from the old column. Turning torque is taken up by their being square, and a little silicone between them will cushion it and keep the wheel from moving in and out. I'll let you know if it works.

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There were several changes from a series 1 like mine to a series 2. Not sure why the changes were made as I do not think the total weight dropped. The steering rack was farther back , behind the axle. The column has 2 universal joints with one at the rack and another about 1/2 way back to the steering wheel. Not sure if that makes a difference in a major crash. The rear suspension had 2 outer links on each side of the axle rather than the central pick-up and I assume that was when the cracked housing issue started, or was it better traction tires that caused the cracking? I assume the couple of diagonal frame tubes by the driver and passenger knees were removed to save weight but could not have been much. Any explanations that make sense?

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Even if the square tube were exactly the size listed (they never are imho), that's 0.010" clearance between them to rock back and forth and multiplied out to the diameter of the rim. Ideally there would be no clearance as there is now with a one piece shaft. It could be shimmed or blunted grub screws through nuts welded to the outer (no cushioning/compressing is the goal). The wall thickness of the square tubes should be 0.125" or more to help resist ovaling from steering input with a pot hole or bumping a curb. With these add-ons ("new" steel prices have increased greatly), the price is approaching DD, which is a solid inner and 1/4" or so wall outer and made to close tolerance specifically for this and probably a better, higher carbon alloy than square tube. Just wanted to share a little more about it than I had already.

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Thank you, MV8. I have some steel coming to play with. Ironically, this all started with my being annoyed by the play in the steering, which turned out to be the link between the steering shaft and the rack and pinion box having rubber bushings that were beyond repair. I have a new link coming from Moss. I certainly would prefer to use the professional collapsing shaft. At the moment I'm thinking that I could align the Borgeson shaft with the two ends of the cut off shaft and weld it in.  So, two possible designs, and fun pursuing the best answer.  It keeps my brain active.

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