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WW1 Thornycroft restoration


Great War truck

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With boring out completed, the castings were then machined to their final external sizes. The bottom threaded hole is for a small length of 1/2” steel bar to act as a Pedal “stop”.

 

And for re-assurance, the two castings were stood on a true flat service so that a short length steel bar of the matching diameter could be slid through the two holes to ensure that they lined up without deviation!

 

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The castings were then returned to the Milling table so that the top holes for Greasers could be drilled and threaded – and the the two holes in the feet of each casting were drilled for the bolts which will secure them to the chassis rails. Those holes are still to be counter-bored or “spot faced” to complete the job.

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We are preparing for the Christmas blitz at the moment so that we can make some progress. One of the things I want to do is to finally fit the handbrake and gear levers. The handbrake requires only a key and some paintwork which Father is doing at the moment. The gear lever, you may recall, did not quite move far enough due to the quadrant limiting its travel. To allow a bit more travel, I have firstly filed another 3/16" from the end of the slot.

 

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Then I aimed to win another 1/16" by moving the bolt holes. I wanted to add 1/4" boss on the side anyway so I turned up some brass bosses with the locaing spigot offset.

 

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These were successfully silver soldered in but left the gunmetal filthy!

 

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After drilling the holes through and spending a good time polishing the casting, this was the result.

 

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Hopefully, this will be enough but if not, it has been suggested that I move the shaft centres. The right hand one is fixed but I could shim the one on the gearbox by as much as 1/8". As the selectors at the box end drop downwards and those at the lever end are about the same length but upwards, then the lever should move forward by 1/4" at the quadrant.

 

We shall see! (Thanks for the suggestion David!)

 

Steve :-)

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With planning the Christmas blitz and seeing as we have been working in the area of the various controls, our thoughts have turned towards the steering column and wheel. You may remember, from page 113, that we had two steering wheels cast from our pattern so that one could be finished off and fitted to the Coventry Transport Museum Maudslay lorry. This was musch earlier than we needed it so it has been on my living room carpet ever since!

 

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First task was to machine the hub of the wheels to suit the column. We had been fortunate to be given the top of a steering column and steering wheel centre from which the dimensions could be determined although, as you can see, they were a bit poorly.

 

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I cut through the column between the wheel and the hand throttle to see if I could work out how it went together.

 

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To be honest, it was not obvious! Then my pal Adrian kindly sand blasted it and it became a bit clearer. There is a 1 1/2" tube pushed up into the end spigot and brazed. You can see the spigot with a line of rust seperating it from the outer tube which does not rotate and which carries the hand throttle and advance mechanisms. Then you can see another line of rust seperating that from the bottom of the steering wheel itself which forms a shroud over the outside to stop the rain getting in.

 

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The spigot has a key into the wheel and a lrge nut on the top to secure it.

 

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Interestingly, the sand blasting also revealed that where the column tube had been completely corroded away, only the braze remained to protect the steel.

 

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The spigot was removed by use of heat and my hydraulic press. When it finally movved, it went off with quite a bang!

 

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From the spigot and photographs, I could work out what the replacement should look like and proceeded to make up the nut t go with it.

 

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The second nut is for the Maudslay.

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Onto machining the spigot. First job was to bore the end to suit the new steering column tube.

 

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Then turn it around and turn a taper to match the original and cut the thread for the nut.

 

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The Myford lathe is a wonderful flexible tool. However, to change the pitch of a thread when screwcutting, the gear train driving the leadscrew must be dismantled and the correct ratio gears selected and fitted. One day I will treat myself to a gearbox!

 

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The thread was cut using one of the cutters from a coventry die head, supported in a simple holder.

 

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Two complete spigots and the original. One for the Maudslay and one for the Thornycroft.

 

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Once the spigots were available, I could machine the wheel centres, using them as test pieces. Amazingly, I didn't take any pictures of the process. Suffice to say, they were mounted on the faceplate of Father's Colchester Student and this was the result.

 

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I have attacked the edges of the boss with a Dremel pencil grinder and sanding drums to blend them in and the result is quite pleasing. Father has volunteered to finish the job before black powder coating all over.

 

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I have turned a plug to the same taper to help the powder coater by being able to thump it into the bore to mask the surface and also give him something to hold on to.

 

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On to the column next!

 

Steve :-)

Edited by Old Bill
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Thanks Andy. That's a thought.

 

The steering column had been sawn off long ago. However, we do have the bottom half of the inner tube.

 

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This gave me the section (so I thought) so we bought some 1 1/2" x 1/8" wall steel tube to push over the 1 1/4" worm spigot. I then proceeded to cut the key slot in one side.

 

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The steering wheel spigot was then silver-soldered on.

 

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The bottom end has a clamp around it to prevent the tube from spreading when torque is applied and to grip the worm spigot. Ours was rusty but serviceable, until I tried to push it over the outside of the tube!

 

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What I had thought was corroded 1.5" dia tube actually proved to be 1.458" outside diameter! The simplest cure for that was to skim the outside of the new tube so, once again, the big Dean Smith and Grace lathe at the Echills Wood Railway came into its own.

 

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Another slot was cut up the rear face to give the tube some room to squeeze onto the spigot.

 

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Another Christmas job is now to cut the outer tube which, I believe, Father has in stock. He is pretty good at this advance planning lark!

 

Steve :-)

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The steeringwheel spigot was then silver-soldered on.

 

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Somehow I don't think it would feel right to be pulling hard on the steering wheel when out on the road, knowing that there is only a film of silver solder between you and oblivion.

 

 

In your original description you used the word 'Brazed'. Perhaps brazing would afford more strength and peace of mind, although I would not have been adverse to screwing the parts together and pin'ning.

 

Barry

Edited by Asciidv
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Somehow I don't think it would feel right to be pulling hard on the steering wheel when out on the road, knowing that there is only a film of silver solder between you and oblivion.

 

I feel sure that it would take more than human strength to break that bond.

 

I found something on the internet saying "up to 135,000 psi in shear" so lets assume half that in this case. Area is about 7 square inches, so that is 500,000 psi. at a radius of 0.0625 feet. So 30,000 lbs-ft of torque capacity.

 

The shear are of the steel key is much less, I reckon that would fail before the silver solder.

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Hi Barry.

 

The original item was brazed on using a brass alloy. I have used silver solder because I am a lot happier that I can achieve a good joint and, as far as I can make out the strengths are very similar. The only downside for silver solder is the cost! The way the joint is made, there is plenty of contact area so I am quite happy that it will stand up to the use.

 

Thornycroft seem to have used brazed joints in quite a few places including the brakes and drag link so they must have had some confidence in the process!

 

Steve :-)

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Hope all your plans come to fruition over the Christmas period, as ever look forward to the next instalment of your brilliant achievements. Merry Christmas to all the family.

 

Thank you - that is very kind and of course we very warmly reciprocate your Christmas Greetings!

 

Steve arrived here today so the team is now complete - Tim arrived here on Thursday! Big Mark has delivered all of the prepared timber for the Thorny seat this afternoon so we are ready to get on with it! He has done a very nice job for us - as he always does - it is great to have such a skilled woodworker for a friend who is also so highly interested in the project.

 

And of course, a very Happy Christmas to all who read this!

 

Tony

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Well, as the festivities die away, we have made a start. As Dad said, Mark has delivered the timber for the seat box, all beautifully prepared, and I have been eying up the job to see how to approach it. I see that I did the drawings in March 1994 which shows how long this project has been in progress!

 

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Then we had a go at fitting the gear lever quadrant. As I mentioned before, the slots did not appear long enough and were too far forward so I filed 3/16" from the end of them and moved the mounting holes forward 1/16". This proved not to be enough but a suggestion that I received here, to shim the change shaft bearing forward was acted upon and I made a 1/8" spacer to go behind the inner bearing.

 

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That just tipped us over the edge and the lever fitted the slots just right.

 

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Unfortunately, the centring springs now proved to be 1/8" too tall! These were reduced by bending the tips over a bit further in the vice and success was achieved.

 

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The gear change is now finally installed and functions quite well. We will press on with the woodwork tomorrow.

 

Steve :-)

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A return to the fray! We have started on the seat box but the first challenge is where to start? I drew the thing 22 years ago and, quite frankly, can't remember how I planned to assemble it! We started by cutting the profile of the top edges of the sides where a doubler is screwed inside.

 

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Tim then sanded them to shape.

 

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Then it was a case of cutting out some rebates in the side panels fort the front and rear panels. A simple, if somewhat tedious job with a chisel.

 

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Success!

 

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A pair of seat end panels ready for assembly.

 

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The heel panel has ribs along the back to bolt the seat box down and also to support the seat. These were jointed and glued into place.

 

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Then assembly could begin! Screws through the end panels hold it all together. These are not visible in any of the photos we have so they will be deeply countersunk and then filled before painting.

 

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A cross-rail was added to support the rear of the seat.

 

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Tomorrow, in between receiving guests, we plan to add the remainder of the seat support and then glue the whole assembly together. We hope to have the whole lot ready for painting before the return to reality!

 

Steve :-)

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Yes, that is always a good way to do it. In this case though, the end panels are so heavy that I was having trouble just handling one and still being able to see the line! I did make a template to draw the curves so they match at least. As usual, we are stretching our equipment to the limit and the sander might not have handled the combined weight anyway!

 

Cheers!

 

Steve :-)

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We did a bit more yesterday between guests. First job was to screw the toolbox floor down. Unlike the Dennis which has the fuel tank under the seat, the Thorny just has empty space which is used as a tool box. Most useful!

 

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Then it was a case of jointing the rails which run across the back to support the seat surface itself. I knew that lesson I had at school on how to cut a mortice would be useful!

 

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Then it was a case of securing the uprights against the side panels, gluing all of the joints and cramping them up.

 

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Whilst the glue was going off, I fitted the arm rest pieces inside the side panels. Screwed and glued again, they should stop the side panels cupping.

 

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With the cramps removed, we started to panel the rear face. Good old Mark had already cut all the planks to length and left a couple of spares so I only had to plane the last one to width to fit. They were all screwed to the rear with proper slot headed screws. Non of those pozidrive things!

 

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We have more guests today but I plan to go outside shortly and make a start on fitting the seat itself.

 

Steve :-)

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Steve;

Fantastic work as always. That seat must weigh a couple of hundred pounds. It reminds of what a church pew looks like, not very comfortable on the backside for a long journey! Are you going to add some cushions?

 

John G

 

Happy New to your crew

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Steve;

Fantastic work as always. That seat must weigh a couple of hundred pounds. It reminds of what a church pew looks like, not very comfortable on the backside for a long journey! Are you going to add some cushions?

 

John G

 

Happy New to your crew

 

Jack may have a nice pink cushion...

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