David Herbert

Speaking of happy owners, why has the guy in the upper middle of the last photo got another guy on his head? I do like the T though, great workmanship and attention to detail. Very nice! David

Yes but the M4A4s were never built with HVSS. They were also never built with radial engines, Cummins diesels or 105mm guns. Or with huge wheel excavators or logging yarders mounted on top. I think that it would not be right to refer to an Israeli 105mm, HVSS, Cummins engined 'Super Sherman' as an M4A4 even if that is what it's hull started life as. Similarly I do not think that the fact that a very large number of publications over the 40 years that I have been involved with Shermans have wrongly refered to M4A3E8 etc. makes that a correct designation for any but the very few experimental prototypes. But that is just my opinion ! David

Looks home made to me, the mix of crude structure and the rather over engineered reduction gearing makes me think it was put together, probably post war, out of anything available. This is only my gut feel though. David

Not a stupid question at all but HVSS is the ONLY correct term to describe the variant of Sherman family vehicles with that type of suspension. There seems to be common idea that adding "E8" to any Sherman designation is correct. It is not. The ONLY Shermans that have E8 in their designations were a very small number of M4A3E8s that were built to prove what became HVSS. They were an experimental project (oddly enough the eighth one, oh, and the E stands for 'experimental project'). There certainly were never any M4A1E8 or M4A2E8 built, but any M4A1,A2,orA3 built after a certain date were fitted with HVSS. The M4A4 was discontinued before HVSS came out. There were crudely speaking two generations of Sherman: the earlier ones with small hull hatches and the later (known as 'Ultimate series') with big hull hatches. These later tanks were somewhat heavier and what had been not very good bogie wheel tyre life got much worse. This was much more of a problem than the added ground pressure which could be addressed with extended end connectors. There were various projects to redesign the original suspension (VVSS) and the chosen one was introduced into Sherman production as an improvement, not an optional extra, completely replacing VVSS as the parts became available. In the manuals the tanks are ALWAYS described as 'with HVSS' or not. NEVER as E8 or 'easy eight' which seems to have no military origin that I can find and I have only ever seen in modeling orientated books. I hope this clarifies the subject. David

Those are really great photos ! How on earth did you synchronise taking them with the gun firing, or did you have a setting on the camera where it takes a burst of photos over a couple of seconds? (need quite a good camera to process so much info though). Do you need planning permission for a bang like that or can anyone have one ? Personally I have always wanted to make a bang that resulted in a 20 foot crater but my wife won't let me. David Ps. Yes I do know that we have explosive licensing regulations !

Why didn't they just reverse both the tram and the WOT6 untill they came apart and call it a draw? David

I have been away for a couple of days and had not realised that my initial curiosity about the engine in the Gama Goat would develop into quite such a diversion of the thread. Sorry. However.... Andy & Bob seem sure that the blower/supercharger as used on non turbo Detroits, and Chieftain and 430 series engines does not raise the inlet air pressure above atmospheric. If this were true there would be no point in the blower as it would not move any more air than a plain hole in the side of the engine. If you take a deep breath and blow the air out between nearly closed lips you can feel the pressure on the inside of your cheeks despite the fact that you are blowing through a hole with atmospheric pressure outside it. Bob quotes a pressure of 5.5 inches of mercury at 2100rpm. That is ABOVE atmospheric pressure, ie the blower does increase the intake pressure, so that there is fresh air in the cylinder for the fuel to burn in and not exhaust gas. The more that the inlet air is pressurised the more will go in and the more power the engine can be persuaded to make but if you use too big a blower/supercharger it uses a disproportionate amount of power to mechanicaly drive it so to get even more power Detroit added turbochargers which use the otherwise wasted energy in the exhaust to further increase the inlet pressure to the 30 inches of mercury that Bob quotes. Don't forget that a non turbo/supercharged engine runs with a significant vacume (negative pressure) in its inlet manifold. The reasion that the air still moves into the cylinder is only that there is a bigger vacume in the cylinder as the piston moves down. With a 2 stroke engine it is much harder to persuade the exhaust gas to leave first so Detroit and others chose to forceably blow the exhaust out by pressurising the inlet air. This does increase the power as without it the engine will not run. To make a distinction between increasing the pressure enough to make the engine run at all / better / with more power / with even more power seems to me to be pointless, the pressure is still increased above what it would be with no blower. I hope that I haven't upset anyone with this bit of pedantry but I thought it worth writing. I am not going to go on any more about it, or people will get grumpy with me! David

Bob, I think that we may have a small misunderstanding due to our alledged common language. In the UK the term 'supercharger' is usually used to mean a mechanicaly driven device that blows air into an engine, the Rootes blower being one of the most well known, and I thought used on all 2 stroke Detroits. The term 'turbo' (short for turbo-supercharger) refers to a centrifugal blower driven at high speed by an exhaust powered turbine. As you say some larger Detroits have these as well as the Rootes blower and got a 'T' designation after the normal no. of cylinders and displacement per cyl. It seems unlikely that you can blow air into a cylinder at all, still less use it to expell exhaust gasses, without it increasing the intake pressure. A Detroit with a worn out blower is very feeble because without the blower there is not enough pressure to get enough air into the cylinder for the fairly short time that the ports are uncovered, and against exhaust pressure which is still there because it is a 2 stroke engine and there is half the amount of time for this all to happen than there would be on a four stroke. The more air you can get in the more diesel you can put in and the more power comes out. My point was that the engine in that Goat had a turbo and did not look to me like a Detroit 3-53 so I wondered what it was and why anyone would change it. Gama Goats had many failings but the engine is usualy regarded as pretty good. David

What engine is that? I thought that they had a small two stroke detroit with a supercharger on the side (3-53?). Those sound great untill your brain gets mushed by the noise. David

Jamie, The 'W' in WM tells you only that it is a wide gauge machine, ie the track assemblies are further apart. A standard narrow gauge machine is just designated M. Dozer kits were made for both by several manufacturers as at that time none of the crawler tractor manufacturers made their own dozer kits and quite an industry developed converting crawler tractors into dozers, graders, cranes, etc. The US military had almost every model of crawler tractor made, quite often identical to civilian ones except that they were green, but there were also heavily modified versions such as the ones that were designed for pulling artillery that had front mounted winches, extra seating and military towing arrangements on the back. Otherwise standard tractors used by engineer units tended to have full lighting and guards on the front and in the track frames (to keep mud away from the rollers) but both of these features tend to get removed in their later lives. Similarly machines that were equiped originally as dozers often lost the dozer kit when they were used for agricultural purposes post war but it is usually possible to tell as the holes where the bits were bolted on have the burned off remains of the bolts or are left open, whereas they would have been plugged with wooden plugs when new, if not needed, to protect the threads. I think that it would be most unlikely that your tractor would have been used in combat as it is hard to think of a role for it that could not have been better filled by a proper military vehicle but you can be sure that one found itself being shot at somewhere. Still it is a nice tractor and relatively rare, most Ms in the UK are narrow gauge as they were used by the War-Agg for ploughing. David

You now have the challenge of wether to weld up the crack and lose the chassis number or keep the number and the crack. Have you got a set of punches with the really old style font with which to re stamp it? Is it possible that the army stamped that little essay onto that very accessable part of the truck to save people having to look in different places on different trucks? I can't believe that Thornycroft would have done such a crude job. Also I can't help but wonder how the crack got there without the edge piece being displaced and no obvious other damage. Great to have its identity though. David

Before we decide about which way up to look at these characters stamped into the chassis, can someone confirm that this is actually where Thornycroft stamped the chassis number? If it is not the chassis number it could be any sort of a code, part number or inspectors mark and any or indeed both ways up. Was it stamped by someone who was dyslexic ? David

I don't think that the character before the 791 is a '1' as the top is not sloping as it is on the clearer '1'. However it is not a very convincing '4' either and certainly not a '7'. So could it be something other than a number? Also is that a 'H' after the 791 ? Can you tell anything about what range the chassis number must be in from the build standard? It would be nice to know it's identity, especially when you are this close. David

Antar, When I found this photo a couple of years ago when trauling through Google Images, I then spent a long time trying to find it on www.m201.de (the watermark in the image seemed to point the way!) but could not see it anywhere. I made enquiries with several Dutch friends but drew a blank also. Like you I think that it is in Germany or Belgium possibly. There is what looks like an M47 next to it which might suggest that it was taken some time ago before the conventional weapon reduction disposal rules started to bite. I also have this type on my 'when I win the lottery' list and have collected what photos I can, also have the TM. PM me with a phone no for a chat if you want. I had hoped that your post would turn up some new info but those that know are keeping quiet. David

I have seen people go to great lengths to avoid a bit of welding but never thought of peeing as a substitute ! Very creative. Mind you, I have found that a couple of weeks 'campaign' sorts out stinging nettles quite well. David

Brilliant ! Does anyone recognise any locations, how about a then and now video ? There seemed to be little interest in driving on any particular side of the road but as they seem to have Hounslow to themselves it probably didn't matter. As for creating a skid pan on a public road.... Mind you, my late grandmother told me about LGOC buses using the (rear only) brakes and the camber of the road to slide sideways to get into bus stops if there was something parked too close to the stop. I suspect that the idiot soldier happened to be the most gifted actor in the unit - he forgets himself sometimes and does things right. Or was he a known actor of the day? Best bit is demonstrating emergency stops with a group of children as the target. Now that is the good old days in action! You would have thought that the IWM could tell the difference between a piston ring and a main bearing though. Are there any more of these films ? David

Steve, I have just looked up manuals that I have on engines with roughly the same bore as yours but built rather later. It seems that for iron pistons the 5 thou figure is the one to use. Engines with aluminium pistons used 9 to 10 thou. Can I suggest that you final machine the crown of the piston quite late in the process at the same time as you do the ring groves and outer dia.. It is critical that the distance from the gudgeon pin hole to the crown is the same for each piston so one must be measured from the other. Untill you machine the bottom of the skirt and drill the gudgeon holes you can not hold the piston in the lathe dead square to the lathe axis so you need to do that so that the crown of the piston is square to the axis. If you try to hold the unmachined outer dia in a three jaw chuck, even with the bottom machined, it will be difficult to get it square and you will be squashing the weakest part of the skirt. Good luck David

Keith, To save Adrian and Hanno saying this, no, your one isn't a dozer either ! It is a Caterpillar D8 (8R series) with a Hyster winch on the back. Used for general towing and pulling jobs. It can not pull a scraper box as that needs a compleatly different winch with two drums. Just to be realy pedantic, dozers come as either Bulldozers (where the blade is fixed at right angles to the tractor) and Angledozers (where the blade can be angled up to about 30 degrees either way so the dirt is gradually shed to one side only). As angledozers have wider blades than bulldozers, so that when angled they still cover the full width of the tractor (12' vs 10' in the case of an International TD18) they are not as good for very heavy work. During WW2 all crawler tractors were built as plain tractors. Some had blades and or winches added (also cranes etc.). So all bulldozers are crawler tractors but only some crawler tractors are bulldozers. OK ! David

Hanno, That is a realy nice photo of a wadeproof D8. Unfortunatly it reminds me of something that I did know which is that they were in fact fitted with a winch. I have corrected my previous post where I said that they could only tow things that they were recovering. Many years ago John Marchant had one with its armour still intact and decided to use it to pull down a tree that was in the way. He reversed it to near the tree, climbed up the tree to fasten the cable as high up as possible to get more leverage, and then discovered that he had not properly disengaged the (over centre) master clutch. As the tractor was still in reverse it chugged up to the tree and knocked it over with John still up it. He survived the experience and sold the tractor. Both the wadeproofed D8 and even more so the armoured D6 & D7 bulldozers were quite heavily armoured, in the case of the bulldozers to tank standards, as they were expected to work during an assult, not just be sniper proof. There was no real post war development of these as specialised versions of tanks were developed into these roles instead though the Americans used protected dozers of various kinds in Vietnam and later so they could work in insecure places. David

You then get blowback AND blown out!!! Or you could eat my wife's curry... David

Ben, I know this is off thread but how do you know it is a WW1 shaper? It looks rather too modern to me (more functional, less decorative detail) but I don't have particular knowledge of Ormerod products so am happy to learn. Nice find though in that condition. Do you want a small ( 1 1/2 ton) planer project to go with it? I also thought that 'war finnish' was WW2. David

[quote name=GeePig Maybe the condition of the gear teeth had something to do with the necessity to remove the lid to check the oil level, meaning it did not get done as frequently as required. Or a driver who couldn't change gear without loud crunching noises! Many years ago I had to dismantle a car gearbox and found that the reverse idler gear had lost about half the length of its teeth. Not knowing any better I built them up with weld and ground and filed them to shape by eye using the unworn part as a guide. I was always a bit gentle putting it into reverse but it lasted about 40,000 miles and was still fine when I sold the car! Interesting that on the Thornycroft the 'gate' is a simple H with the four forward gears as you would expect but reverse is an extension of the movement into first, so there is a neutral both sides of first. Was this common in trucks of that period? David

Several people have refered to the hardness of armour as if it is a good quality. In WW1 the only way to make steel plate tougher was to have a relatively high carbon content and to heat treat it in a way that left it relatively hard. This made it nicely proof against small arms which was the perceived threat but when hit by anything big it shattered. look at the WW1 tanks at Bovvy to see what I mean. Between the wars there was no money for development and no one could believe that there could be another war so we went into WW2 with almost the same technology as 20 years previously. In WW2 it rapidly became clear that tanks were required to fight other tanks and defend against anti tank guns, both of which fired relatively large, high energy projectiles. It was simply not possible to make the projectiles bounce off in the way that you could with a rifle bullet, and instead it needed to be 'bogged down' and stopped progressively before it penitrated the armour. To do this the armour needed to be very strong, but at the same time ductile. Hardness was a very negative feature because it lead to shattering in which very little of its strength was used. A high melting point was a good thing because when hit a lot of energy is turned into heat and it is better if as little of the armour melts as possible (not very strong when runny). We now have aluminium armour which provides perfectly good protection at the cost of being 2 1/2 times thicker than steel and is not at all hard. The ultimate in hard armour could be thought to be the ceramic layers in Chobham armour but actually they contribute almost nothing to the protection against projectiles as they just shatter, absorbing little energy. What they do very well is deflect the jet of very high temperature plasma from a shaped charge so that it does not burn its way in. In conclusion most WW2 and almost all later armour is deliberatly not very hard. However it is quite often made of alloys that work harden in the same way that stainless steel does, and that can make it very hard to drill and particularly to tap threads into. Also many people think that the nickle based welds are somehow much stronger welds than normal. The weld itself is actually not particularly strong but the point is that as it cools it does not contract and pull cracks in the surrounding armour plate as ordinary arc weld would. David

I have just looked it up on Wikepedia (the font of all knowledge) and was suprised to read that SG iron was invented in 1943. Steve, you say that you would have to put out the boring of the gudgeon pin holes but I thought that you had access to a Bridgeport or similar which is what I would use. The key is getting the axis of the gudgeon pin exactly square to the axis of the piston and the right distance from the top and on centreline. David