Does anyone know the definitive answer to this? I've seen it asserted that the tracks formed part of the underwater propulsion system. On the other hand I've seen it stated that the tracks were only engaged once the DD tank was on the beach.
Isn't it the other way round? I'm sure photos of the propellers indicate that the propellers are driven off the rear idler wheels....meaning the propellers can only rotate when the tracks are moving anyway. Of course, Herr Gruber I could be wrong. Edit: propellers driven off modified rear idler. Good video, the bit you need is just after five minutes into video.
As the top/return run of the track was also underwater (unlike, say, a Buffalo) the net effect would have been a nice round zero.
This is actually very useful information, as it confirms a suspicion I had about the original Tetrarch DD.
Good point....or just a slight overall forwards motion if you take into account the 'wall effect' of the top track being close to the hull overhang.
Thinking harder about it, they got it to work on CVR(T) and the like without shielding the top run so the 'wall effect' must have been fairly significant.
If by the wall effect you mean the front of the trackguards, I think the trackguards were removed on DD tanks, so that the bottom floor of the canvas screen could be fitted.
I mean the wall effect between the upper forwards moving track (which is creating a backwards force) and the underside of the hull where it overhangs the track which is effectively also moving forwards (due to the action of the propellers) and with these two forces thereby roughly cancelling each other out. That implies that the rest of the track (which is free moving with no wall effect) and moving backwards would generate a slight forwards force and thereby add to the forwards motion of the tank.
Ah thanks. I should know this because the Crusader tank fitted with the EBE side floats was driven by the tracks only, albeit that the tracks were given lengthened spuds to give a better paddling effect. These gave 3 knots, which was not quite good enough, but still not nothing.
I don't know how much it helps with the final form of DD propulsion, but trawling Straussler's many patents (or at least those that Google's Patent search finds) from 1920 onwards throws up a fair few on amphibious drives. It's cursory, as I can't claim to have looked at them all, and you have to be lucky to get a USPTO external link that includes the written concepts & claims, but he doesn't appear (so far) to have had any interest in including references to tracks in water propulsion terms. Like I say; sketchy, but - tracks, other than as a thing connected to the drive sprocket - he really doesn't seem to be filing stuff in a patentable way, and he liked patents, often for entire systems. Absence of evidence ≠ evidence of absence & all that, It's a narrow lens; but you'd think there'd be something if he gave a toss. All about the flotation, prop drive & steering. Google Patents Lord knows. I've gone patent blind.
The German clever clog again: As the name duplex drive alone indicates, the tanks had two types of propulsion: one for water (the propellers), one for land (the tracks): The tracks basically lack the necessary surface area to move enough water to produce a measurable forward thrust compared to the propellers. By the way, the details and peculiarities concerning only the track drive of main battle tanks have been meticulously broken down by Merhof and Hackbarth on no less than 547(!) pages(unfortunately only available in German language) Propulsion in water is not mentioned there in any way - I strongly assume this will have certain reasons. Who is interested anyway: https://athene-forschung.unibw.de/doc/111331/111331.pdf Since reading this book, I don't think that I really understand anything about real, professional tank design....one of those (sad) lessons in humility and modesty when reading reference books Regards Olli
Theory: You know how it works. But it does not work. Practice: It works. One does not know however, why it goes. Everyday life is when nothing works and no one knows why.
