Direction Finding

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Spacenut
Posts: 1205
Joined: Thu Feb 20, 2014 9:43 pm
Location: Hampshire

Direction Finding

Post by Spacenut »

So I have been slowly improving the calibration accuracy of my speedometer and Nav odometer, zeroing both and using an 8.7 mile test loop to check both the absolute calibration and the relative difference between the two. I had got it down to a 2.5% error, but as I pulled into the drive on full right lock the steering wheel suddenly felt “odd”, with lots of lateral movement pivoting around the upper steering column support.

A quick look in the drivers side footwell confirmed my worst fears – the plastic bush that supports the steering column as it goes through the bulkhead had broken up. In fact, I only found half of the bush intact, the rest of it was reduced to plastic shavings on the floor.

As I knew I would have to replace the bush before I could use the car again, I ordered a replacement from Rimmer Bros at 11:30am on Friday morning, and the part arrived exactly 24 hours later! Amazing service, you can understand why there are so many classic Triumphs and MGs still on the road…

The new bush appears to be made of a material similar to urethane, quite hard but with a bit of give in it. Rather like a bodywork grommet, it is intended to be pushed through a hole in a retaining plate, which is then bolted to the bulkhead. The splined end of the steering column then passes through the bush and into the UJ on the other side.

So the plan of action was simple – disconnect the steering column from the UJ, withdraw the column from the support plate so that the latter could be removed, press the new bush into the support plate and reassembly is the reverse of removal, as all the best manuals would say.

Sounds simple, but the reality was a long hard slog. First the dashboard had to come out (top cover, RH closure panel, centre support moulding, instrument panel and wiper contact plate), then undo the UJ pinch bolt from inside the front wheel arch, then pull the splined shaft out of the UJ from the drivers footwell. Here’s a few images I took along the way...

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Front brakes. (ATE) M16 calipers with Ferodo fast road pads and my new anti-rattle springs installed, courtesy of Bigg Red. Solid grooved rotors from Burton Power, alloy hubs from Hi-Spec. Only the upright betrays its Ford origins and even this has been modified for screw-in spindles courtesy of Randall Motorsport, who modify Ford uprights for stock car racing.

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My old SPAX dampers will soon be replaced with AVO double-adjustable dampers with spherical joints top and bottom. I have the same same set-up on the rear suspension. Wishbones are from Lee Noble, fully Rose-jointed and still holding up well after all these years…

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I can’t show you a picture of the upper UJ because I just couldn’t get the camera in there. Here’s a picture of the fuel flow sensor instead :D

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Actually, you can just about make out the UJ pinch bolt above the roll-over valve on the fuel tank. Accessibility is poor because the steering column was one of the first components installed in the chassis and hasn’t been removed since :(

Part of the problem is that the Rover SD1 steering column is designed to collapse in the event of a head-on crash, so the splined shaft is only held in place by a sacrificial plastic pin designed to shear on impact. So even though the UJ was loose I couldn’t simply pull the column out without breaking the shear pin. Plus there is a fair amount of wiring attached to the column as well…

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So after 4 hours of teasing, cajoling, tapping and wiggling, the splines finally gave up their grip on the UJ and the column was free! Now onto the support plate – this lozenge-shaped piece of steel is held in place with two bolts, but one of them was glassed over. A bit of surgery later, and the support plate was free as well. The plate was quite badly distorted, so I bashed it back into shape before pressing in the new bush. Then it was bolted back into place on the bulkhead, the splines were well-greased and popped through the bush and into the UJ behind.

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Yes, it’s that little bit of grey plastic. What a lot of effort for such a seemingly insignificant part...

More cajoling was required to get the splines to fit completely into the UJ, but eventually the pinch bolt was reinserted and tightened, the wheel was roughly aligned and the re-assembly could begin.

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First I thought I better clean up the carpets a bit. This is the passenger side. All the plastic shavings were vacuumed out of the drivers footwell and then it was back on with the main dash panel, followed by the instrument panel…

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The black box on the right of the panel is the SGI-5 signal converter. The speedometer is just in front and has 2 DIP switches for calibration. I left the top cover unsecured so I can change the calibration settings more easily.

Finally all back together, a quick test drive confirmed that (a) the steering was back to normal (maybe even a bit more direct than before) and (b) the wheel was off-centre by a couple of splines. Fortunately I had greased the steering wheel splines after all the trouble I had removing the wheel last time, so getting it re-aligned was straightforward.

Phew! Back on the road, and only 30 hours after the problem had first manifested.

Lauren

Kegsti66
Posts: 2849
Joined: Fri Sep 26, 2014 7:20 pm
Location: Northamptonshire

Re: Direction Finding

Post by Kegsti66 »

Fantastic work Lauren, what a nightmare of a job. Your drive and energy is inspiring. :D

junior
Posts: 1189
Joined: Fri Dec 19, 2014 7:43 pm

Re: Direction Finding

Post by junior »

Kegsti66 wrote:Fantastic work Lauren, what a nightmare of a job. Your drive and energy is inspiring. :D
Yep that job would have had me cussing away for a long time. Interesting to see what your up against with a fibre glass car. Keep posting. Ta.

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KevJTD
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Joined: Thu Sep 26, 2013 8:48 pm
Location: Lincs

Re: Direction Finding

Post by KevJTD »

You assume that a rear engined car would be a doddle to do stuff in the footwell but as you have described and pictured, the reality is far from simple!
Handy that you know the car so well Lauren, that would have driven someone less educated in the ways of the car to despair.
We'll done 8-)
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Spacenut
Posts: 1205
Joined: Thu Feb 20, 2014 9:43 pm
Location: Hampshire

Re: Direction Finding

Post by Spacenut »

Thanks guys - it was a bit of a struggle, but nice to have a process/procedure for this job too. Worst one is still the steering rack, which hides under the fuel tank and cannot be removed without taking the tank out first. Fortunately I have only had to do that job once, when I bump-steered the steering geometry...

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