Lotus Elan

Steering column

PostPost by: Baggy2 » Thu Mar 31, 2011 10:05 pm

Hi
I have an early plus2 with the solid one piece steering column designed to crush your chest in the event of a front end crash. For some time I've had a (second hand) colapsable column in stock for me to fit 'one day'. I was going to ask the forum whether the newer column could be a direct replacement for the old one still using the same interior cowl / indicator switch etc. Before asking I thought I should check the archive and was horrified to find the collapsable columns seem to have a habit of snapping. So the dilema is do I keep the solid column with its dangers if I do hit something - or - do I change to the newer column with an increased chance of steering failure? All opinions welcome.
Thanks
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PostPost by: alaric » Thu Mar 31, 2011 10:27 pm

Hi. Mine has the later collapsable type and I went through the same horror when I read through the threads. I concluded that the design was fine as long as there is no evidence of a crack starting near the corners of the cut out, and as long as the inner is pushed far enough into the outer. I think that's what it came down to. So I put mine back together and fitted one of the universal joint couplings onto the steering rack. That's an extra half inch or so in length so you can take up the adjustment by pushing the inner part slightly further into the outer part - hope this is making sense. So anyway it all looked sound once together. There's only a finite length of cut out in the inner part of the column but it was enough for the adjustment. Also, when fitting the column into the car I recall having to be careful to ensure there was no stress on the column that could weaken the joint. I do agree it's a scary design though. It's up there with the brake master cylinder non return valve as one of the single points of failure that would be catastrophic.

If anyone else has an alternative solution it would be good to hear it.

I hasten to add however that I'm not an automobile designer, and messing with the steering is not something that I'd want to do or advocate without some verification that the end design was sound. I hope the mod that I've done with the universal joint is ok - it's a common one as I understand it.

Regards.

Sean.
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PostPost by: Craig Elliott » Sat Apr 02, 2011 8:41 am

Hi,

Having experienced the delight of a snapped steering column, it's very important to check the column for the beginnings of any cracks before fitting it. If possible using a proper crack detection process - I've had a second hand column that looked OK but the beginnings of a crack were already there (where the clamp holds the inner and outer together). The other thing that I think is really important is to make sure that the column has no sideways forces acting on it once fitted - i.e. the line from the point at which it links to the rack and the steering wheel is straight and the brackets don't force a bow in the column. It may also be worth strengthening the outer column in the area in question (e.g. sleeving it in some way).

You really don't want to find that you've got no steering when trying to turn right (in the UK) or left (in Europe or the US etc) across the path of fast moving traffic.

Craig
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PostPost by: Elanintheforest » Mon Apr 04, 2011 5:18 pm

I think that I'll stick to the risk of the steering wheel doing me harm rather than a snapped column doing me...harm.

You have a good chance to avoid a front impact by using the steering wheel...but not if the column is broken.

Also, given our vulnerability in a side impact, I don't think that a front impact is too much of a worry in the scheme of things!


Mark
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PostPost by: davidj » Tue Apr 05, 2011 12:18 pm

Hi,

I was worried about the solid steering column on my car so one of the first jobs I did was fit a later collapsible type. It is a Triumph design, and I think mine came from a spitfire.

However, reading all the horror stories about them breaking I wish I had not bothered. It was not a straightforward job. I too fitted one of the universal joint couplings onto the steering rack. However, because it is longer the inner part slid further onto the outer part and virtually bottomed out, resulting in it not collapsing in the event of a crash! I work at an Engineering company and had the slot lengthened by the extra length of the UJ.

The Cowling and the indicator switch also had to be modified, because the later tube is a bigger diameter than the earlier one, and brackets made to hold the column in place. As mentioned before these have to be true and solid so no extra stress is applied to the column.

However, in saying all that, it is a still a significant diameter steel bar so I think failure is more due to the high stresses caused by the clamp on a very small area rather than the shaft bending. I would have though the fibreglass mounting is more likely to flex than the column.

D.
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PostPost by: Craig Elliott » Tue Apr 05, 2011 4:57 pm

David, I (and some friends/family who are qualified engineers) have checked this fairly thoroughly and while the turning force does have a part to play (the columns only seem to snap when turning the wheel when the car is moving slowly or standing still), I'm more or less certain that the sideways force also has a part to play. It is possible to generate flex in the column if the steering clamps aren't lined up properly. The fibreglass mounting points are strong enough to do this.

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