With the poor weather well and truly upon us the Diamond T had been wrapped up in its tarpaulin.

I say this in the past tense as the high winds of the past week have reduced it to a shredded mess. Still my method of tying it down was not in doubt as the ropes and rings were still there, even if the majority of the tarpaulin was not. Guess what I will be buying this week?

Now with the inclement weather has been the chance to concentrate on garage work. Since the last blog I have been looking at a solution to the damage on the steering column thread by which the wheel is retained. During the strip it proved almost impossible to remove the nut as it spun freely without reversing off the thread. Eventually some home made mini-pry bars were used to pull the nut off. The fact that the nut could move up and down the thread without turning was testament to the unserviceability of the thread. A bit of research determined the thread to be a 1" National Extra Fine (UNEF) with 20tpi. With the threaded protrusion being only 7/16” to re-cut with a standard thread would give very few turns as these threads were much coarser. If the original horn assembly was to be re-fitted there was little chance of extending the length of the thread as the well below the horn mounting step on the Sheller wheels is only 0.6”/15.3mm. An option had been to obtain a long shank bolt, bore out the centre and pin or weld it in place within the column. However, the retaining nut would have had to be turned or ground back to roughly the width of the original (3/8“) thus leaving insufficient engagement.

Damage to the column thread

The inside diameter of the column is 19.4mm, and the drill size for tapping out a 7/8 UNF is 19.5 so an option would be to tap the inside of the column, using the current threaded section to get the thread started and proceeding into the column just short of the end of the spline, and then part off the damaged section to enable the bolt to sit in the wheel well. My main concern was the effect on the shaft fatigue strength with a thread cut in the bore. As the shear load would be at the end of the spline I was eager not to extend the full thread beyond that point. However, a solution was at hand as one of the benefits of working for an aero engine manufacturer is that you are surrounded by very knowledgeable stress experts to put the mind at rest.

Of course another consideration is the hardness of the shaft. Due to the poor weather I have been unable to put my theory of cutting a thread, to the test but have instead assumed it will be possible and modified a 7/8” bolt. Shortened and bored out to accept the horn wire the head was also reduced to 7/16" to provide clearance in the well.

Drilling out the Bolt very carefully. You will note the bolt is being held by the thread. Not a good practice but gentle feed of the drill prevented it from spinning. I had tried clamping a scrap bolt in the chuck first to see if it damaged the thread.

Finishing off

Bolt bore has been radiused at both ends to prevent chafing of the horn cable

Bolt and Horn Assembly. Sill a bit dusty.

At the recent Malvern Convention I collected a new wheel from Jaap Rietveld. An original Sheller it has a few small chips but when the 60 year old grease was removed (3 hours with a bowl of hot soapy water needed) the finish is excellent. Not concourse but well in keeping with what I am looking to achieve with the restoration. At the show I also found a good set of original pedals, which means that all the main components are now in place to complete the cab.

On the subject of the cab the finishing strips are now in place. Top coat and assembly will follow shortly.

Last week a most enjoyable run was made up to John Webster (Roof Over Britain) with Edd to collect a load of Bar Treads. Of the ones collected there were sufficient to make a good useable set. Several were rejected with cracking and/or side wall damage. Problem is my garage is now very full indeed!

Don’t panic, I can still see the door!

Another task which turned into a bit of an eye opener was the cleaning of the winch control lever cross member. Upon removing the paint on the underside I found definite traces of light stone. Now I have been engaging with Michael Starmer on how these vehicles were painted and thought I had identified a definite paint scheme. However, I am now more than a little confused, so rather than get anal about it if I see light stone it will be painted in light stone.

Finally for this instalment, the ballast box hand rails have been refurbished with new tubing.

Thank you all for once again reading my blog.

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