I was watching a video on Dunkirk and was told that soldiers would run truck engines dry to cause them seize and rendering them useless to the Germans. What is an engine seize? Can those engines be salvaged? Or would the Germans in this scenario know it’s hopeless and scrap the engine completely?
In: Technology
An engine is seized when it is mechanically impossible to rotate its crankshaft. In the scenario you described, seizure was achieved with excess friction because there was no oil to lubricate the metal-on-metal movement. The pistons probably expanded and warped, becoming wedged inside the cylinders. Besides that, connecting rods and crankcases usually break. When the engine is seized in this way, repair *might* be possible depending on how extensive the damage is, but usually it’s so severe that it is both not repairable in the field and more expensive to repair versus replacing outright.
Ok, let’s try this:
A seized engine is a broken engine. Normally, it means that the pistons have jammed within the cylinders (the two parts that contain the exploding fuel) and the engine is locked in place.
Yes, they are salvageable, but thats expensive, time intensive and difficult. An advancing army does not have any of these luxuries.
The Germans would have tried to fire up the trucks that got left behind and use them, only to find they won’t start. Knowing likely what had been done to them, they would have had to proceed without them, rather that waste resources and time on them.
Denial of surrendered equipment is always a good idea in wartime.
A seized engine is an engine which does not turn over any more. Even if you try hand cranking them or bump starting them the engine will not physically be able to turn.
In an engine there is a lot of metal components moving against each other with a thin film of oil between them to slide on. But if you remove the oil from the engine the metal will just scrape against each other “dry”. This will make a lot of heat and scrape up the metal. The heat weakens the metal causing even more damage and may also warp it. The end result is often that the metal pieces in the engine which is supposed to be a tight fit is now crashing into each other and the engine does not turn over.
If this happens to your car and you notice the oil pressure light turn on and immediately pull over and stop then you might not have damaged any components at all. And even if you did some damage it is possible to swap out those components of the engine and it will be good to go. And in the late 30s swapping engine components were a regular maintenance task so these components would have been readily available. The problem was that most of them were back in the UK as German and French cars were built with different engines then the British cars. In addition the cars were run dry as long as possible which would have likely damaged a lot of the internal components. They might even have damaged the engine block which is the biggest component of the engine. At that point it is cheaper to just get a new complete engine then to replace most of the components of the old one. In any case it would have been a lot of work for the mechanics. So I doubt any of the trucks that were run dry and left on the beach would have ever been operational again. They might have been used for spares to help maintain the trucks that were abandoned intact. It is also possible that some Belgian farmers would get a hold of a few of the trucks and spent a good amount of their spare time getting one of them working again.
An engine is usually seized when it locks up due to a number of reasons, but in this case they’d drain the oil and coolant causing major damage. First the engine overheats and causes the block and heads to warp making it pretty much unable to seal between the parts. The cylinders will warp and not allow for the pistons to properly move nor for the rings to keep the combustion chamber separate from the oil, which is now mixed with any coolant left in the system. Narrow clearance areas like bearings also warp and now provide much more resistance. I’m sure I left some out, but also the main forms can outright crack. Metal against metal needs lubrication. Things like main bearings and rod bearings are simply metal separating two other metals.
In short it’s not worth rebuilding versus new equipment and sometimes not even possible at all.
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