Re: Collapsible Column Impact Clamp
Posted: Sat Dec 21, 2013 3:29 pm
Technical Data, no section letter, right at the front, Torque Loading figures, Front suspension, Steering Column Clamp. I believe the earlier manual only refers to the earlier style of clamp.
That line is simply not there in my copy of the later Service manual (36/T 327), the other detail for torque for the front suspension steering etc is there. It must have been added in a later printing.
Anyway what torque figure does it give? Does it differ from that in the Plus 2 manual.
I've been looking up stuff on collapsible steering columns, but nowhere have I actually found any figure of what initial and sliding friction forces are desirable in a collapsible column; there may be figures buried in research papers but they cost money to read.
What I did discover was that Lotus seemed to be ahead of most manufacturers in installing collapsible columns quite a few years before big name ones. There seems to have been a big fuss about the issue in the late 60's (Raph Nader etc) and I suspect it was then that Lotus included that torque figure in the Manual. But when you talk of 'Expert Advice' Where did Lotus get their advice for the setting?
Later systems seem to rely on pre-known strength of materials rather than obscure torque figures setting friction, for example plastic shear pins joinin the two portions of the column, or the zig-zag lattice crumple zone (made of steel ?) on the upper portion of the steering column.
Incidentally from the info I found on the net, it is pretty clear to me that the outer column is supposed to slide, with friction in the clamp to the dashboard, absorbing energy while it does so if the column is being pushed towards you due to frontal chassis collapse; The dashboard clamp should probably be tight enough to initiate the shortening of the column at the clamp being discussed from the Original Posting.
The ideal of course is that the steering wheel jumps towards you in a crash and then relatively slowly collapses forward so that the force on your body is never excessive... (they cal these Air-Bags ).
Bill, That clearly isn't what I wrote. But it was intended to illustrate that we have no idea of the mechanics involved - What heavy weight were you going to drop?! Why?
Aye, I know but what you wrote "In a crash at 30 mph your body weighs about 1 1/2 tons ." doesn't actually make any sense in Physics.
Since I reckon my body & head would start to crumple at around 100-150 lbs I would like to think that the intial collapse friction force was about 125 lbs, dropping to 100 lbs sliding friction for the few inches of the flat part of the steering column. Personally I would prefer if Lotus had made that flat portion longer because I am a little fella so my seat is fairly far forwards, so my steering wheel is far forward so there is only about 2 to 3 inches of flat part left for the column to collapse.