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Another J Type on the way !

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Some progress has occured in the diff casing department. After a thorough clean up with celulose thinners, two coats of 'Glyptal' insulating paint were applied to the inner surfaces.  The r

Nearly done, bar a few finishing touches, it only remains to light the wicks for a grand finale. But first, I need to find some paraffin.

The steering wheel has come on leaps and bounds today. The arrival of the rolled tube coincided with Stan being rained off and I prepped all the parts and made two spiggots from a short boiler tube of

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Cleaned up the centre and did some remedial work on the paint. ( OK, I dropped it ! )  The wheel is now ready for a trial fitting which may even happen tomorrow.


The alterations to the diff casing have made themselves known,  via a photo sent to me recently.  Compare these two pictures of an early and a later build, both J type.



There was clearly a substantial build up of the lower arms, which was apparently instigated by the Army, after a number of rear axle failures.

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These modified rear axle cases began to appear from January 1916.( Auriga ) As 2393 was a 1915 build, It would have started out with the early type, which at some point was changed for the beefed up version. We shall be returning to the original, which is in better nick.

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The diff bracing strap had suffered substantial erosion at it's extremities and was barely hanging on.

Fortunately I had some 5/8 Whit. Pylon bolts from a previous find and with some skilful welding from Stan, the strap was restored to it's former self.

The strap itself is an early example, having the riveted collar very near the end. This makes a bit of a performance out of fitting it and later versions have a longer shank  (see previous pics.)

After a short battle the strap is back in place and tightened up, with a bit of luck it can stay there as well !



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I'm not sure of an official torque poundage, but thinking it might as well do something, I did it up to BSFT ( British Standard Fairly Tight. )  The strap has been relaxing unbridled in the colonies for many years, by the looks of it and is now back in harness for further employment.

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  • 2 weeks later...

Considerable excitement has surrounded the arrival of a parcel from Australia. The contents have been eagerly  fettled up and I present them here for your entertainment. 


As promised, Dave Rossington has produced a superb copy of the Oil Pressure Relief Valve, working from an original drawing. It is shown in position, but not yet screwed home. This is a real work of art and only requires the internal  spring to be fully operational. What a fabulous thing it is. Thanks Dave !


Also enclosed is what we think is a genuine oil filler cap. 


This has a part no. 13418 which doesn't immediately line up with Thornycroft's 'J' number,  however it looks correct and has cleaned up nicely. I have seen this same part on slightly later engines and it's possibly one of these.


Here is the underside, the central spiggot has a hole for a ring and captive chain. This item has been in a fire at some point and arrived fully annealed which helped me to gently get it back in shape.


The third bit of treasure is an original 'Whittle' fan belt which was lurking in the box like an arthritic rattle snake. I treated the leather blocks to some conditioner and worked all the metal links until it slithered properly again. This is the first part of the water pump assembly we have so far managed to gather.

Great finds, very much appreciated, original stuff is getting very hard to find now.888



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4 hours ago, Old Bill said:

Nice find, Tomo!

By the way, the lid is held on with a spring rather than just a chain as the air movement blows it off altogether. I need to fit a stronger spring to ours!

Steve   :)

Thanks Steve, I was not aware of the spring within. Does the odd shaped bracket on the rim support the lid in the open position ?

The mystery part no. has been explained by Dave, who tells me the lid came from a DB 2 Thornycroft  boat engine. It is basically the same item as fitted to the J type, with a different part no. 

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Now that you mention it, I think that bracket must do that. I couldn't fathom it out and didn't make one but the spring does hold the lid in the way whilst pouring oil in so it would be good to have a stowage position.  This is the filler on the original lorry at Carlton Colville.


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Some progress has occured in the diff casing department. After a thorough clean up with celulose thinners, two coats of 'Glyptal' insulating paint were applied to the inner surfaces. 


The remaining studs were  removed and the threads and sealing face cleaned up prior to a complete denture replacement, once eBay has provided. 


I also found  these signature items lurking in the stores and set to with the rotary whizzer to good effect.


The cast iron has once again avoided the rust bug and the machining marks are still visible.


They have now joined the queue for paint.


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  • 3 weeks later...

The diff casing is now sporting a new set of BSF dentures, the operation went well, although I had to extend the thread on the short ends to match the originals.


This has completed stage one of the diff project.

The Thorny plates are coming on well, but require careful attention to avoid the paint 'puddling' around the lettering.


Stan's experimental engine stand went back under the knife for some modification, to enable the crank case to sit either way up. 


This was rapidly achieved and the locating holes bored out with a very useful baby mag drill.

The crankcase was tried out for a fit and it did.


Swiftly followed by the crankshaft, which was dropped in temporarily  to test the water.


Now there's a fine sight to see !

Thanks to Stan, who gave up his day off to create This progress.




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  • 2 weeks later...

We have been 'forging' ahead with the crankshaft fitting and the main bearings slotted straight back into place. After a little detective work to sort out the shims, the crankshaft was nutted up and revolves freely, with Mike's dial gauge showing only a 10th of a thou play at the bearings.


The crank was timed up with the cam shafts, once the tiny numbers had been discovered.


The crank has useful tdc. position indicators.


This was slightly confusing until I realised the marks were arranged to be seen from above the engine and therefore I needed to be seeing the other marks from the underneath. Hope this is clear !


The odds were then reduced and after checking that No. one was on it's power stroke and not the exhaust, (from the cam positions, ) We are satisfied that the valve timing is now correct.




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The forging ahead has now sadly ground to a halt, due to the lack of No.4 con rod which was sent away to have its little end properly seen to, about 2 months ago. The reason given is a delay in the gudgeon pin hardening process due to 'covid'.

However, con rods one to three have been successfully fitted. No. 1 was a little reluctant at first, but it was trying to tell me something, which was that the upper bearing shell had become reversed in it's housing. ( Another trap for the unwary ! ) Even once rectified it was not quite happy and Mike Lewendon was called in for some blueing and light bearing scraping. This was successfully accomplished and the three big ends are now rotating smoothly and awaiting the return of No.4.



The mains have been pinned up and the big ends will need drilling for theirs, once the No.4 prodigal son has returned.

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The starting handle bracket was cleaned up and painted, but found to be unservicable due to serious wear on the main shaft. There are two annular groves which should allow movement between the two positions,  by means of a ball bearing and spring forming a detente. In fact the ball had been going 'off piste' for some time and had eventually escaped completely, leaving the shaft free to wander.



Stan took on the job, and swiftly built up the shaft with weld.



It was then turned down and new grooves formed on Mr. Colchester.



A spring has been codged up as a temporary measure, which works, however a slightly stronger one will be required before any future starting is attempted.





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The opportunity was taken to freshen up the paint on the sump and to temporarily replace it to protect the crank.


There was a problem with the valve springs, which didn't fit nicely. On further investigation one of the original springs turned out to be a replacement from something else and was slightly larger than the rest. As luck would have it this was the spring I sent off to Tested Springs as a sample, with the predictable result that in due course I received a beautifully made set, of the wrong spring ! 

Unfortunately they could not be altered and another set had to be made to the correct pattern. These have now been fitted and now look much happier.



Which just goes to show how careful you need to be !

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With some time on my hands at present, I went to fit the cylinder cover plates properly, only to find that some of the 3/8 studs had not yet been cleaned up. This was belatedly sorted out by rather unconventional means, due to the close proximity of the surrounding studs.


This rather tedious job was accomplished and the original nuts were cleaned up, a gasket made and the first cover fitted.


Just the rest to do ! Quite satisfying to be sealing something up for a change.

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25 minutes ago, Tomo.T said:

. This was belatedly sorted out by rather unconventional means, due to the close proximity of the surrounding studs.



Hi Tomo, I use a little trick of putting a hose clip on a die for situations like this, no chance of splitting the die with this method.

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