WW1 Thornycroft restoration

[Great War truck]

The Lathe now looks magnificent!

 

Readers may recall that the Thornycroft chassis had been built into a hut on the top of Penmaenmawr in order to use the engine to drive a water pump. Part of the conversion had been to remove the transmission brake and to roll up a 2” wide ring and weld it onto the end of the brake drum in order to use it as a belt drum. The job was done very neatly including the crowning of the drum to help the belt stay on.

 

Steve’s task was to remove the extra width and then skim the surface back to allow it to be used as a brake drum once again without tearing up the lining. The drum was measured and Adrian very kindly loaned a 16” four-jaw chuck from another DSG lathe. Unfortunately, it proved to have a slightly different back fitting and could not be mounted. Undaunted, he had another rummage and came up with a 12” four jaw, just right for the lathe and Steve spent some considerable time setting up the machine. The drum was so heavy, he had to stand in the lathe bed in order to lift it!

[Great War truck]

In the end, he had to grip the drum from the inside on the very narrow edge ring as it was the only way to hold it. As he wanted to part the excess off, at Adrian’s suggestion, he faced up a disc with a centre in it which he used with the revolving centre in the tailstock to keep the drum pressed up to the chuck.

 

 

With the job now secure, he turned his attention to the toolpost. This was solid and could not be adjusted so a quick strip down was in order where the reason for it’s seizure was discovered.

 

 

 

A clean and polish exercise then ensued whereupon the parting tool was mounted and the parting process commenced.

 

 

[Great War truck]

This was successful but very much a heart-in-mouth exercise, especially as Steve only had one cutting tip!

 

 

 

The remains of the ring were then faced off.

 

Next, Steve tried to turn the periphery but this proved troublesome. Big though it is, the DSG lathe was not quite big enough that the drum would clear the top of the cross-slide so to reach along the drum, the tool had to be severely overhung towards the headstock. Cuts were taken but the surface proved to be extremely hard and the tool just bounced off, losing its edge in the process. A slightly deeper cut caused the toolpost to rotate slightly and the tool to dig in causing the groove you can see in the edge.

 

 

They decided to call it a day at that point and Adrian took the toolpost away to service it further and see if he could find a better tool for the job.

[Great War truck]

A week later and they were ready for another go. Adrian had serviced the toolpost and found a much better tool.

 

This did the job satisfactorily but the drum was so hard that there were a lot of sparks flying! In the end, Steve stopped at the limit of the tool’s length which didn’t quite get underneath the crowning. He felt that there was enough good surface to do the job and he didn’t want to go any deeper as the drum was already down to a thickness of only 3/16”.

 

Whilst not quite perfect, the drum will still do the job it was intended for and is now with Father for painting.

 

Next job will be patterns for the brake shoes themselves.

[fesm_ndt]

I love the old UK built machines as with a bit of care last forever.

[Great War truck]

The Back Wheels were taken away and blasted and returned to us shortly afterwards. They are difficult things to “clean” and there is some more work to be done on them before they can be primed. Again, the old tyres were left on to protect the wheel surface under them so that when the new tyre is pressed on, it will not be a loose fit on the wheel because the old wheel circumference has been reduced by sand blasting.

With this game, it does seem that every stage and at every step we take, another conundrum or puzzle is thrown up. The cleaned up brake drums are badly corroded and will have to be cleaned up by skimming if they are to be used again. They are quite thin already.

 

It occurred to us to look at the drums on the two wheels that came from Mike in NZ, with the thought that they might be in much better condition and could be substituted. For the first time, we noticed only today that the two sets of drums are different from one another. The ones on the wheels just cleaned up have a plain surface whilst the NZ ones have a large rim around the outside. The two photographs will clearly show the difference.

 

The picture of the drum in the Parts Book illustrate the drum with rim – like the NZ ones.

 

But again things are not straight forward. When we took the NZ ones off the axle, we cracked one of the drums and there is a clear picture of this in posting no. 133 dated 26 December 2011. So if we decide to use those drums, there will be some cast-iron welding to do! As we mentioned earlier, nothing is ever straight forward – it would be boring if it was!

[nz2]

Just returned from a walk down back inspecting the bits here and three sets of wheels are the same. None have the additional band about the edge. Even the latter model J of what appears to to about 1924 has the single brake band.

The 1920 manual shows an illustration with the extra ribbing band in the parts pages.

Are there any casting markings on the brake band you have had sand blasted?

Your could be casting be by a different foundry. Two sets I have here have JAC cast on them.

Doug

[Minesweeper]

Just returned from a walk down back inspecting the bits here and three sets of wheels are the same. None have the additional band about the edge. Even the latter model J of what appears to to about 1924 has the single brake band.

The 1920 manual shows an illustration with the extra ribbing band in the parts pages.

Are there any casting markings on the brake band you have had sand blasted?

Your could be casting be by a different foundry. Two sets I have here have JAC cast on them.

Doug

 

Steve and Tim will be with me over the weekend and we will turn the wheels around so that I can have a look! Too heavy for me to move on my own!

 

Tony

[Barney]

Hi Tony,

 

Please can you answer the following question?

 

Tim's post refers to brake drums. Are they full drums as per classic pre disc brake cars or are they just rings bolted to the inside of the wheel?

 

Thanks. John

[Minesweeper]

Hi Tony,

 

Please can you answer the following question?

 

Tim's post refers to brake drums. Are they full drums as per classic pre disc brake cars or are they just rings bolted to the inside of the wheel?

 

Thanks. John

 

They are just "rings" John with a bolting flange flared outwards on the bottom through which they are bolted to the wheels.

 

Tony

[Gordon_M]

Given the description, and the state of the originals, how about just turning up a new pair from forged steel rings? I'm sure that would be superior to making a pattern and casting a pair.

[8_10 Brass Cleaner]

It srikes me not only are they different, but also two different materials.

 

The upper ones are castings, likely iron. Hence the strengthening rib.

 

The lower ones are pressed steel.

[blastermike]

hi tony/tim and steve, I checked another set of rear j type wheels I have and there is one of those brake drums with the heavy bands on the edges, this chassis is around 1919, maybe it was a later design as cracking the drums was a common problem? just a thought, cheers mike.

[Great War truck]

We had the whole team in Devon over the weekend and were able to get on with several things. One thing that was very much on our minds after the recent discussion about Brake Rings was the condition of the second set that we have which Mike very kindly sent over from NZ on the set of wheels on the back axle. You will remember from a posting just one or two ago that the conditions of the originals caused some concern where they badly need skimming and that they are already thin.

 

The NZ set are a later pattern and are cast iron whilst the originals are steel bands. Well, there is much more “meat” left on the NZ ones and it is very much in our thoughts at the moment to go with those – despite the big crack that we knew about and which must be welded – but we then found that the second one has a small crack in the rim which appears to have been caused by a build-up of rust behind it and the pressure from that causing the crack. So both have to be welded up.

 

Anyhow, the next job is to get them off and eye them up properly before a final decision is made.

 

 

Doug was asking about foundry marks or part numbers on them but we cannot see anything at this stage – but they may show up after cleaning. We are not sure where to look for them – can you give an indication, Doug?

[42 chevy]

From a safety angle, have you considered using the the thicker drums as a pattern and having new drums cast. I do not know what the process is called to check for cracks (magna flux?) but I might recommend that be done on these drums if you decide to use them.

As always, your crew does superb work.

 

John G

[Minesweeper]

[QUOTE=42 chevy;417532]From a safety angle, have you considered using the the thicker drums as a pattern and having new drums cast. I do not know what the process is called to check for cracks (magna flux?) but I might recommend that be done on these drums if you decide to use them.

As always, your crew does superb work.

 

John G

 

Thanks John - something else to consider! As you will have gathered, we do like to use the original parts as far as possible so we will not give up on either set just yet. We will get them off first and have a good look at them before finally deciding!

 

Tony

[8_10 Brass Cleaner]

[QUOTE=42 chevy;417532]From a safety angle, have you considered using the the thicker drums as a pattern and having new drums cast. I do not know what the process is called to check for cracks (magna flux?) but I might recommend that be done on these drums if you decide to use them.

As always, your crew does superb work.

 

John G

Thanks John - something else to consider! As you will have gathered, we do like to use the original parts as far as possible so we will not give up on either set just yet. We will get them off first and have a good look at them before finally deciding!

 

Tony

 

If you were to use both types in service you will find the cast ones perform better.

 

The presseds steel ones will distort in use, which doesnt help efficiency.

 

The iron ones will be stiffer and will not distort to the same degree.

[42 chevy]

Tony;

This is a follow up to what I previously posted. I assume that the brakes on the lorry are mechanical, rear only and the parking brake is on the output shaft on the transmission. With that in mind, making sure the rear brakes are in optimal order is paramount. I have had cast iron welded before (it uses a special rod), and if there is a high nickel content in the iron, the better the weld. In your braking situation, you will be dealing with heat, vibration etc, so special attention needs to given to check the integerity of the drums.

 

John G

[Will Grime]

Gentlemen,

 

while I really appreciate and admire your dedication to the finest principles of restoration, I think you could be justified in replacing dodgy brake drums on a number of grounds:

 

1 They're consumables. Had the truck remained in service it would be on its fourth set by now...

2 it's reversible. Remove and retain - that is, preserve - the present drums, and wear away a set of replacements instead, and if you want to you can always reinstate them. BS7913 recognises this as an entirely acceptable conservation approach.

3. Look after yourselves. Brake failure through a cracked, broken or even simply distorted drum won't do you any good, and frankly I want to read about the next restoration rather than reports of broken limbs, or worse

4. Look after your public and fellow enthusiasts. Brake failure could conceivably result in collision with nasty consequences...

 

Your choice of course: just setting out an option that might be further consideredi. Keep up the great work

 

cheers

Will

[Great War truck]

With everybody here in Devon over the weekend, there was enough muscle available to pick up the old rotten spare front axle and put it into the back of the Land Rover to take to the local Garage where there is a 60 tonne Press. You will recall that we wanted to take one of the swinging arms off this to replace a much more worn one that came out of the axle that we plan to use.

 

The pressure was taken up to 40 tonnes but the King Pin refused to move.

Heat will often cure this sort of problem, so Neil at the Garage very kindly put some oxy-acetylene heat on it after which we tried again – but still no movement.

 

The King Pin started to bend, - there was no alternative other than to cut the top off it. We then tried pressing again, but still no movement and we decided then that there was no alternative other to cut out the old Kin Pin. We had to do this on the Dennis and once that King Pin had been cut into more manageable portions, it became plain sailing to get the bits out although still tedious work.

So we took the axle home again and using the back of the Land Rover as a bench, two through cuts were made in the King Pin in the narrow gap between the swinging arm and the axle end and the arm was knocked off the axle. All that remained to be done then was to knock out the two ends of the King Pin left in the arm – was came out very easily and the other will follow today.

[fesm_ndt]

From a safety angle, have you considered using the the thicker drums as a pattern and having new drums cast. I do not know what the process is called to check for cracks (magna flux?) but I might recommend that be done on these drums if you decide to use them.

As always, your crew does superb work.

 

John G

 

There are a couple of NDT methods to do this. Magnaflux is a brand but the method is called MT (Magnetic Testing) or MPI (Magnetic Particle Inspection). I started a thread on this ages ago as it is not that hard to do. http://hmvf.co.uk/forumvb/showthread.php?16151-Ndt&highlight=destructive

 

PT and penetrant testing also shown in the link above is an easy option also. As you guys like it old school you could try soaking it in auto trans fluid, wipe clean then dust with some type of white dust powder :-D. Times like this I wish I was in the UK as I would come around and do it for a beer :-D

[flandersflyer]

Thanks John - something else to consider! As you will have gathered, we do like to use the original parts as far as possible so we will not give up on either set just yet. We will get them off first and have a good look at them before finally deciding!

 

Tony

 

If you were to use both types in service you will find the cast ones perform better.

 

The presseds steel ones will distort in use, which doesnt help efficiency.

 

The iron ones will be stiffer and will not distort to the same degree.

 

 

Iron will soak the heat away better....

[nz2]

Do the brake drums show the casting marks of the Catton Foundry?

Also are there cast numbers on the top of the axle. Not all axle housings have these which could be casting dates.

Doug

[nz2]

I'll try again with the photo of the brake casting.

Doug

[Minesweeper]

I'll try again with the photo of the brake casting.

Doug

Doug - there are no markings at all on our cast iron ones - and in fact yours are quite different from ours with no flange or lip on the outer edge of the "ring" away from the bolting flange. I would have expected the number cast in on yours to have been the "Part No." - but it is not - the Part No. is 54482 - nothing like! So another mystery!

 

However, all of this discussion has helped us make our minds up about what to do with the drums - and that is to replace them with newly cast ones! Yet another pattern for Steve to make and to join the queue.

 

Thank you, chaps, for your input into this - all of your comments make sense!

 

Tony