Old Bill

The combustion will certainly start over the valve but the flame front will propagate across the top of the piston towards the exhaust valve on the other side. A Tee-head engine does give a very nice mechanical layout but it is very hard to get a compression ratio of much more than 4:1. This is fine for the early fuels but overhead valves allow a much better combustion chamber shape with higher ratios. Fortunately for us, ultimate performance is not an issue! Steve :-)

Now you are challenging my powers of descriptive English! Right. The valve sits on a nomal seat, stem downwards. Above it is the combustion chamber with the port sideways into the bore. Immediately above the valve head is another seat, just like that of the valve but a bit bigger. On top of that sits an iron disc with a lapped-in face to seal against its seat. In the middle of the disc is the tapped hole for the spark plug. Once those are in, the bayonet sleeve is dropped in on top and rotated to lock it. This has a big tapped hole in the centre into which is screwed another sleeve, this time with a hexagon end. That is screwed down with a tube spanner until it touches the spark plug disc. When screwed up tight, it holds the disc down against its seat but has the spark plug up the centre. Does that help? Perhaps we should get Father to lay all the bits out in sequence for another photo? Steve

When you look down the port, you can actually see two seats. The lower one is for the valve but the upper has a disc on top. The disc has a tapped hole in the centre for the spark plug and is pushed onto the seat by the threaded sleeve screwed down hard against it. The bayonet sleeve is just a way of providing a thread for the clamping sleeve. Screwed up tight, it shouldn't come undone but, as Father says, there is a steel strip screwed to the top of the block between the ports with the ends against the hex at the top of the sleeve. Goodness knows why Thornycrofts developed such a complicated arrangement! All of the other lorries we have had contact with just have a large tapped hole in the top of the block for a screw-in plug. Steve

Pleased to see you here, Paul and I am glad you are enjoying it! Steve:)

Hi Doug. I have a suspicion that Thornycrofts painted their engines grey as standard but neither of ours has any sign of top coat paint on it. I could easily believe that they painted everything army green for simplicity during the war years. I also think it likely that when a lorry went through shops, the engine was painted green, even if it had been grey from new. It makes our life easier to paint it that colour anyway! When Dad cleaned the flywheel back, the back of it had a very heavy coat of primer of a grey colour which took some shifting. There was no sign of top-coat however. When we first got the chassis in the 1980's it had a patch of black paint on the side. This was rubbed back with brasso to reveal the original khaki-brown. We had bought paint which Richard had mixed for the Imperial War Museum gun-lorry and it was a match so we have continued with the colour across the fleet. This may not be the correct shade for the US Army FWD but we have no evidence for that one at all. Tim has a photo of paint being mixed in the field in a barrel using a plank to stir with and shovels full of pigment being fed in. I think it likely that any shade of khaki-brown that we produce will have had at least one vehicle in service carrying the same shade! Steve

Ah! The ongoing debate! With the Dennis, and all of our vehicles, we have set ourselves a standard where we want it to look as if it has been cared for using factory parts. We don't mind original parts looking a bit 'used' as they are, after all, nearly 100 years old now but we try extremely hard not to deviate from the original design when we make new. The Dennis cannot claim to be an 'original' vehicle as we have put it together using parts from multiple sources. However as far as it can, it has been assembled from Dennis factory parts. Where parts were beyond repair, we have copied them as closely as possible. We have been very fortunate in that the original drawings have survived so we have been able to make parts to them. We don't consider these parts to be replicas but more 'further originals'! As to making repairs, the chassis frame should be entirely rivetted. However, we have used bolts in some places thus deviating from the factory specification. This we consider acceptable as it is a recommended fix in the maintenance manuals of the time. The aim was not to produce an 'as-new' example but one that is 'used but cared for'. At the end of the day we all look after our vehicles to a standard that satisfies ourselves and as long as we are honest about what we have done there is room for every approach. After all, we only do it for the pleasure that it gives us! Steve

The mud was a real trial for us. The tipper came through the gate and stopped. The Dennis managed a few more yards after the film clip and then stuck outside the beer tent. Both were assisted in with the Land Rover. The FWD did quite a bit better with my approach of blasting in through the gate in second with my foot clamped to the floor. Tim says that it was very exciting but unfortunately, he didn't have his camera in his hand. I managed to get as far as the military vehicle section before I found a really soft patch and stuck. The military Autocar did best of all and went all the way on its own. All four had to be dragged out and we have spent the rest of the week getting the mud off. It was during this process that I managed to push the Autocar into the back of the Dennis, mashing a side light. Nothing we can't repair but another job I really didn't want to have to do. Probably the first ime that two Great War vehicles have collided in sixty years! Steve

Yes, all been a bit slow recently. This having to earn a living really gets in the way! Steve

Hi Barry. I am fortunate to have a bore micrometer (which I inherited from a Dunkirk veteran) and I have measured them all as 4.557" diameter in several directions and along the length of the bore. I then measured the mic with my vernier caliper and they agree so I am treating the dimension as gospel. I must admit that I am impressed with the consistency across them all. I have ordered the liners with a diameter of 4.555" + 0 -0.002" to give a clearance for the Loctite. In my limited experience, the bottom of the bore seems to suffer very little wear so I expect that he centered the boring bar there and relied on it being square to the bottom flange. The recess was milled on a CNC machine. The block was clamped to the table and the tool run up to contact one side, then the other and zeroed in the middle. This was repeated in the opposite direction and the recess machined out in two cuts using a carbide tipped tool. I have allowed a clearance of 0.005"-0.010" so the liner should just drop in. All I need now are the liners! Steve

Sorry, I don't know the location other than 'Northern France'. The photos came from our French dealer who assured us that it was 'British bomb'! Steve

Sorry to hijack your thread, Ben but here is a pic of the McCurd which we took to Bletchley Park today. (We got very wet on the way home!). Can anyone tell me how many McCurds were used by the ASC? I know that they had at least one but have never seen any documentary evidence other than a single photograph. Cheers! Steve

Now that is an exciting shed! Steve

Thanks Griff. I hadn't thought of EBay and that is the best price yet although they may be a bit cagey about posting it. Thanks Sean, that is the best price I have seen for the big bottle. Any chance they could supply a 50cc bottle instead? Sorry to be picky but I am going to have an awful lot left on the shelf otherwise! Many thanks for taking so much trouble. Steve

Thanks Sean. For some reason, 620 is harder to get than most. Dad is investigating leads at the moment but we may be back! Steve

Ian. From your pics, I would suggest that the damage is not caused by the bolt heads but by the flexible coupling itself. The radius of the damage appears to be outside that of the bolt heads. However, the flexi disc could be brought closer by pushing the magneto up hard, thus bending the coupling towards the pump. Thin bolt heads might be an option but I think that a bit of care in securing the mag is all that is required. I wouldn't try to repair the damage to the pump unless water is actually coming through as you are more likely to do more harm than good. That's my two pennyworth anyway! Steve

Sean is quite right. This is not a high performance high speed machine. If teeth are just marked, you could give them a polish with a needle file and emery and simply put them back. You probably won't even notice the noise! I would not put an old gear with a new one, however, as the new one will probably be spoiled fairly quickly. You could spend a lot of money on this job but you shouldn't really have to. I would think about what you are doing with the car too. If you are doing thousands of miles per year, then it is worth spending the money. A couple of hundred miles is a different game altogether. A nice challenge for you! Steve

Hi Alastair. That all sounds rather unfortunate but I am sure that it can be brought back for much less than that. You guys looking after it will be able to do all the stripping, cleaning and fitting so that will remove the bulk of the cost. You could also machine the gear blanks yourselves and just get the teeth cut. I would guess that they are all straight-cut so that shouldn't be too difficult either. The company I would recommend is Charles Leek and Sons of Leek in Staffordshire. (http://www.leekgears.co.uk). They made a half shaft and propellor shaft for our Dennis lorry and their service, quality and prices were all excellent. They are a small outfit, delightful to deal with and very happy to do one-offs. Have a look at their website and give them a bell. Let us all know how you get on! Steve :-D

I have just had a very nice chat with a gentleman at Westwood Liners and he suggests that we have finish machined liners a close sliding fit in the bore and secured with Loctite. He says that for a low performance engine (this is less than 6hp per litre!) we won't have any problems at all and it offers the least risk to the block. He can make 'wavy liners' which have 1/32" of intermittent clearance to give space for a special adhesive whose name he couldn't remember but which they use on early Rolls Royce motor cars with very fragile blocks. However, Loctite will be fine for us. He suggested that we only Loctite the lower part to give us time to get it into the block before it goes off so we will do that. I am going down to Devon this weekend so I will measure it all up and produce some liner drawings. All I need now is a source of Loctite 620! Steve

You don't hang around, Dan. Nice job! Steve :thumbsup:

When I sent the notes to Tim to publish, I forgot the one which shows the made-up ring in the groove. It proved to be just too big to be installed and, as rubber is incompressible, I was on a hiding to nothing trying to fit it! The smaller ring I eventually used, had been rescued from a hydraulic system and has already seen some service. It is a pretty tight fit though so I expect it will be OK. We shall see! Regarding setting up in the four-jaw chuck, it is very much trial and error for me. I use a clock gauge where I can and keep adjusting the jaws until it is there. In this case, I simply brought the tool up close and rotated the chuck by hand adjusting the jaws until the tool kissed more or less all round. Good enough for this particular exercise anyway, if a bit time consuming. I haven't started on the piston patterns yet. I have a railway engine to build before I really start dedicating time to this project! Steve

Hi Mike. We are a long way off that yet. This is the current work list: • Rebore cylinders • Fit cylinder liners • Hone liners • Make piston pattern • Get pistons cast • Obtain new rings • Machine pistons • Finish valve caps • Get new valves made • Clean and repair drain taps • New exhaust manifold studs • New rubber seal for block connections • Make up new governor assembly • Fit timing gear to crankshaft • Clean up flywheel and drill out broken studs • Make new clutch spring studs • Inspect bearing shells and scrape to suit crankshaft • Fit crank • Clean up camshafts, check bearings and refit • Repair/replace tappets • Obtain new valve springs • Make pattern for new pump inlet spigot • Get spigot cast • Fit spigot to pump housing and have welded • Make up new flange for fan bearing carrier • Get flange welded and machine. • New gaskets all round • Inspect and repair con-rods as necessary • Scrape and fit big-end bearings • Make up oil pipes • Make up oil filler • Overhaul pressure regulator • Repair/remake oil level indicator • Make/obtain cylinder priming taps • Overhaul carburettor • Make HT lead tubes In my experience, lists like these tend to get longer before they get shorter! There is a way to go yet but we are making progress. Cheers! Steve

Not much to do but always something. Completely finishing a project is always hard! At the moment I am playing with the mountings for the side curtain as it will be much safer fixed to the lorry than rolled up in my bedroom! I want to make up a heel block for the throttle pedal to try to make it a bit more comfortable to operate. There should also be some steps on the side of the body to allow you to climb in over the back wheels. They are a blacksmithing job and were postponed when my anvil was taken. I now have a replacement anvil but have been too busy keeping the rest of the toys operational to get stuck in. Earning a living is getting in the way too! Steve

Regular readers may recall that we have been having some fun and games trying to start the lorry. I put this down to my driving a desk and simply not being strong enough to swing the engine at a good speed. A little while back, Father, whilst trawling the net, found an American magneto supplier from whom he acquired an impulse starter for the spare Eisemann magneto that we keep for the FWD lorry. As this magneto is also anti-clockwise rotation, I have made an adaptor plate to allow it to be fitted to the Dennis engine and today, we tried it. After a couple of pulls over compression, the engine fired and ran on two cylinders. However, even after a couple of goes and a plug clean it showed no enthusiasm for running smoothly so a further investigation ensued whereupon, I realised that I had fitted two of the leads to the wrong terminals. I swapped them over and Bingo! It ran properly after only a couple of pulls. I put the error down to having to connect the terminals from inside the distributor cap so it was reversed. That's my excuse anyway! It was super to hear it running again and have confidence that it can be started. The only downside has been that the vibration has unstuck the repaired oil float and it has sunk to the bottom again! Time for another outing. Steve :-D

Hi Mike. I used to design tooling for electrochemical (anodic) machining and should certainly have spotted that one! Thanks for reminding me. It is obvious now! More pattern making beckons I think. Steve :-)

Does he have the hub-caps? These might give a clue. My first reaction is Morris 1 tonner and the hub caps could confirm or refute that in short order. I would agree with your dating. I remain to be proven completely wrong! Steve