Help needed with steering shaft
David Jenkins - 8/9/12 at 03:36 PM
I need a bit of advice...
The story so far...
I've just had an annoying day... 
Now that I've replaced the 2 chassis members following my little - er - incident a while ago, I'm trying to put it all back together
again.
First of all, I couldn't put the nuts back on one of my rod ends as the threads had suffered too much abuse over the years (they're quite
old, still with castle nuts & cotter pins). Even a jack under the ball joint wouldn't stop the taper turning. Took both off for a close
look - and found that the thread on the problem one is knackered, plus the rubber seals on both have degraded completely. So, that was one job I
couldn't complete (new joints ordered off ebay).
My latest problem...
My new problem is the steering shaft - before my ding the steering shaft _just_ cleared the FU chassis member, but now FU _just_ gets in the way. 
I've checked all my geometry and I reckon FU is in the right place (which makes me wonder if it was wrong before! 
)
So now I need to add an extra UJ - and I'm not sure about which bits to use.
I plan to mount a small spherical bearing on the new FU chassis member, to take the shaft that comes down from the steering column. On the front of
this bearing I'll fit a new UJ on a very short shaft to the steering rack UJ.
My question...
What's the most convenient UJ for a steering shaft?
I had a look on ebay, but just about everything I saw needs a splined shaft - for example, there's loads of Land Rover UJs on offer. A spline is
the best way for making a joint - but I don't think I can make one at home!
speedygonzales - 8/9/12 at 04:53 PM
Why don't you just turn the short shaft down so it fits inside the splined end of the UJ, then weld the UJ to the shaft. I doubt it will come off
then.
rusty nuts - 8/9/12 at 05:58 PM
Has the rack mounting be displaced David? Rally Design stock splined shafts that and U/Js to fit splined shaft and rack pinion
David Jenkins - 8/9/12 at 06:09 PM
No - rack is where it should be - I think! (I'll check tomorrow, but I'm fairly certain as my rack mount is VERY rigid)
We're talking no more than 5mm here, probably a lot less. Previously I had about 1mm clearance, now it's about -1 or -2mm.
The solution is fairly easy, just a PITA to implement - and more time too.
rusty nuts - 8/9/12 at 08:40 PM
What column does your car have David? I know there are at least 3 different Sierra columns , my first one had clearance problems
David Jenkins - 8/9/12 at 09:08 PM
I don't know what sort it is, but I doubt it's the column - it used to be OK, before I 'modified' the chassis.
[Edited on 8/9/12 by David Jenkins]
paulf - 8/9/12 at 09:20 PM
I think it is actually one of the errors in the book, I welded in the FU upright when I built my chassis only to find that the steering link wanted to
go through it by about half the diameter of the shaft, ie 10mm.I ended up cutting the upright back out and moving it to suit, but did consider adding
a bearing or else cutting the tube away to clear the shaft and then welding in a short thick wall tube for the shaft to pass through.
Paul
David Jenkins - 8/9/12 at 09:48 PM
One thing's certain - I'm not stripping everything off the chassis, cutting that tube out once more, and welding in another! Whether the
book's to blame (quite probably), the geometry of the wishbones is now correct so I'm not inclined to muck it about again.
I think a bearing and UJ will be the simplest option, hence my initial question.
However, I would appreciate any pictures showing how they've installed a UJ at this location.
RoadkillUK - 9/9/12 at 01:43 AM
I didn't install a UJ, but I did do this (yes it's safe, I'm no engineer, but 8 years on the road and 2 crashes, it's fine
still)
rusty nuts - 9/9/12 at 07:47 AM
What diameter is the lower link of your column David? I had problems with my first one fouling , I ended up finding another lower link which was a far
bit narrower to gain clearance. Rally Design do a splined shaft around about 14mm in diameter and also U/Js rather than the Sierra flexi joint,
that's what I'm using now
David Jenkins - 9/9/12 at 10:14 AM
Mel, the shaft itself is 20mm, and the bit of old Allegro steering link with UJ is 15mm. The join between them is alongside FU, and neither will
quite make it past.
RoadKillUK - I'd thought of doing something like that, but it scares me quite a bit! Even though yours has worked for 8 years or so, it would
always be a worry in the back of my mind. I was also wondering about doing something like this:
This would be another bit of 25mm square tube bolted onto the side of FU to compensate for the loss of rigidity. The length of the brace, together
with the size and number of bolts are up for debate.
What IS annoying is that for many years I had the other half of the Allegro steering link with its UJ attached, but then decided that I'd never
need it so I sold it... it would have been perfect for the job...
[Edited on 9/9/12 by David Jenkins]
David Jenkins - 9/9/12 at 10:43 AM
quote:
Originally posted by rusty nuts
Has the rack mounting been displaced David?
Mel - I've just had a look - and there's a chance that the rack mounts HAVE been displaced!
When I went round the chassis checking for alignment and straightness I didn't look at the rack mounts, mostly because I put a lot of effort into
making them rigid. Now I've looked a bit closer I can see that my reinforcing plate that used to line up very well now shows that the supports
have moved a small amount - not a lot, but certainly enough to move the rack over a few mm. The straps that hold the rack are also not quite at 90
degrees to the rack body, which also suggests that things are not as they should be. The chassis tubes the supports are welded to are straight,
fortunately, so if I remove the bracing plate I should be able to 'persuade' the supports back into alignment.
I can't have a go at it today as we're planning to go and admire the grandson after lunch, but I'll get at it tomorrow.
I really hope that this is the cause of my problem, as it's a relatively easy thing to fix...
[Edited on 9/9/12 by David Jenkins]
rusty nuts - 9/9/12 at 12:25 PM
At least you've found something that likely to be the cause of the problem, hopefully an easy fix
David Jenkins - 10/9/12 at 02:57 PM
Well, I straightened up the rack mounts with a generous dollop of brute force and ignorance, and now everything is lined up as they should be. Now
the steering shaft *just* touches the FU tube - I'm talking about 'scraping paint' here, rather than a total blockage. I need to find
a few more millimetres somewhere.
I could reduce the diameter of the shaft where it passes FU - currently it's about 15mm. I have no idea what the minimum diameter would be
(it's a tough grade of steel, not general-purpose mild steel).
Fred W B - 10/9/12 at 05:35 PM
If you are just looking for a few mm could you not brace a bottle jack with a few bits of wood to the other side of the chassis or other strong point
and "cold set" the tube a little to put a slight bow in it? Not very elegent engineerig wise but you will get away with it?
Cheers
Fred W B
David Jenkins - 10/9/12 at 05:51 PM
That could upset the geometry of the upper wishbone suspension joint... but I think a bent tube just looks wrong anyway!
I'll get there - I'm much closer to success than I was yesterday...
David Jenkins - 11/9/12 at 03:42 PM
Got there in the end... 
Re-aligned the steering rack mounts to where they should be (maybe a tiny bit further over), re-arranged the steering shaft so that the thinner bit
was alongside the FU chassis tube, and I now have 3 or 4 millimetres clearance.
I'm now a happy bunny...
Thanks for all the help/advice offered in this thread...