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MG MGB Technical - Energy-Absorbing Steering Column
|While replacing my steering rack in a 74 1/2 MGB (rubber bumper)I have discovered that it has an energy-absorbing steering column - which seems to have moved the steering column forward so I cannot get the new steering rack "up" far enough (the U joint is farther forward that before).|
How does the energy absorption work?
Am I correct that is to lessen the inpact of the driver's chest during an accident? Can you take off the U joint and softly hammer the steering column back up? There is a circlip and spring above the U joint but I do not see how this can be energy absorbing - it pushes down (toward the front). Does the energy-absorption action move the steering column downward? How can it move downward to absorb energy when it is solid (steering column, U joint, pinion) from above the U joint to the steering rack? If it not energy-absorption that moved the steering column down, what did?
|William, I mentioned the points you are asking in my post in your rack replacement thread. As I mentioned I have not worked on a rubber bumper column but I have disassembled several chrome bumper columns. I suspect the column for the rubber bumper car is very similar in construction.|
You are correct, the energy absorbing column collapses inward toward the steering wheel to prevent the steering wheel from coming into your face in a collision. The column shaft has two sections, lets call them the lower inner section and the upper outer section. The lower section slides into the upper section. The factory injected two plastic bands to keep the sections tight and in position for normal use, they are designed to easily slide/telescope in an impact. The column outer housing on 68-74 chrome bumper cars has a plastic covered basket weave section in the bottom near the floor designed to collapse during an accident. The upper part of the column is securely bolted to the frame under the dash.
As I mentioned in my post on your other thread, I have used a soft hammer to drive the lower column back in. The lower shaft slides out because the u-joints are usually difficult to remove and our prying and pulling will sometimes pull the shaft out a little. I assume the column on a rubber bumper car is very similar in operation. You should be able to drive the shaft back in without removing the column. It will not damage any internal parts as there is no shear pin, just two plastic bands that allow the lower shaft section to slide into the upper section.
I have some photos of all parts of a chrome bumper steering column in my Yahoo photos at;
I hope this helps. Clifton
Your expanded explanation of how it works is excellant and very helpful. I will be looking at your photos.
I didnt email a pic as yet since Clifton has the same on the site he mentions.
I did however push the column inner section into the main outer sleeve by a good inch or so and then push it back through from the other end.
It was under a fair bit or pressure and took some moving (my weight) so I can see how it could ping down and not seem to want to move easily back up.
The suggestion of the soft hammer might shift it, but not hold it in place.
I still think that removing the upper column, fitting to the UJ with the upper part still not fixed then use the 3 mounting bolts on the cone to tighten the thing back up (Down) might work.
|I completely stripped my 78B steering column which and it is pretty much the same as Clifton describes and his pictures show. On mine the lower bit also didn't slide too well inside the squared off tube. I pulled it all apart and cleaned and gave it a light grease coating mainly just so it wouldn't rust. I think the spring at the lower end of the column is just to stop and forward/backward rattling of the shaft in the normal position. The energy absorbtion is as Clifton says is due to the two shaft halves telescoping and the bottom part of the column housing with the weave pattern collapsing. Also the top mount where the three bolts go through has plastic inserts which look like they will break away in a collision and allow the whole top half of the column to slide forwards.|
This thread was discussed between 16/04/2006 and 17/04/2006
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