I was over reading The Historian's interesting and timely thread regarding a special TV broadcast regarding the discovery of some previously unknown German D-Day bunkers...Map Solves Mystery of D-Day Massacre

....anyhoo, in that thread, he posted a link to a page with this photo, which is a screen cap from Saving Private Ryan




Now, whenever possible, I try not to get my history from the movies, but I thought this photo was interesting because it shows some modifications to Sherman tanks that I have not seen before - specifically, the the big-honkin' risers on the back end.

Here's a detail



Now, I have heard of (but never seen) a Sherman duplex-drive, which were fitted with auxiliary propellers and a waterproof, canvas 'gunwale' to displace enough water to float the tank and, theoretically at least, make it to shore.

I've also, on this forum, read of the Sherman Fireflies, which, to my understanding, were British modified (i.e. upgunned) Shermans.

Now, bearing in mind that these are pictures of movie 'props', they are undoubtedly trying to represent something that has a basis in fact The risers appear to be either schnorkels or exhaust risers -

so, a quick, easy question to the 'big-iron' mavens on the board...


....whatupwitdat?????

-whatever

-Lou

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What you see is a "deep wading" kit on a Sherman. I don't think this was actually used on D-day. What it does is allow the tank to wade in from a fairly deep off-shore surf. The big trunks you see cover the engine intakes. The exhaust is fitted with one-way valves to prevent back flooding from that side of the engine. The tank itself is sealed and a bilge pump is installed to keep flooding from happening.

never noticed there was allied tanks in SPR besides the last bit.

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They were used on D-Day, as were the DD Shermans. The deep wading kits met with various degrees of success.

After moving inland, the deep wading kits and DD skirts were removed. One thing to look for with DD Shermans is the idler wheel.

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Okay.... let's pretend, just for a minute, that I'm really stupid.




....which one is the 'idler wheel'?

-whatever

-Lou

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Right there......

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Heres a pic of Some DDs in the water...


There was also a DD Variant of the Valentine...

I would have loved to see the faces of the German defenders on D-Day when the saw the DDs rising up from the sea.

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nice pics Joe!

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Scott

Okay .... so, borrowing Joe's siggy-pic (becuz it was handy!)



is this a DD because it has an idler-wheel?

Thanks for educating me, Jim!

And, Joe, I agree.... great pics!

-whatever

-Lou

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bigfun & Scarface...


never underestimate the power of Google!

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Lou mate, the 'idler' is the wheel at the opposite end of the track to the toothed drive wheel. It usually spins freely on it's axle as a handy place to hang the track on. Most all tanks have them.

The DD Sherman's ran their propellers off the idler wheel, hence they're of a slightly different form to usual.

The one's with the large scoops aren't 'DD' vehicles, they are 'just' prepared for deep wading.

DD refers to this 'Duplex Drive', running on land by track and in water by propellers. They're the ones with the big pop-up canvas sides that form a boat of sorts, designed by the rather brilliant Hungarian born engineer Nicholas Straussler. Unlike the mere wading kit (scoops) that allows the machine to run in a few feet of water without swamping it's engine or exhausts, the DD Sherman, Valentine, and Tetrarch trial model could swim properly in deep water.

Cheers,
Adam.

Thanks Adam.

Lou,

Here is the layout:

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Glad to know my sig was of use.

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It was handy at the moment. Sorry.

Here are some more shots of the deep wading trunks. They were also used in the PTO for obvious reasons. The first shot is of a Sherman lying in a flooded shell hole on a Normandy beach. The other two are I believe on Tinian.

Enjoy.

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Thanks, guys. So, not to beat a dead horse, (but, hey, he's dead anyway!), then on the DD the engine drove the toothed drive wheel, which transferred power to the track, which turned the idler which was connected to the propeller shaft.

Which takes me back to some war movie or other that I remember seeing in the distant past, where there were some tracked vehicles approaching the beach (although they weren't DD's and it was in the Pacific), and their tracks were kicking uip a big froth and I remember wondering how spinning their tracks generated enough forward motion to propel the vehicle to the beach.

Now I know. Thanks, gents.

And, Joe, your siggy-pic was invaluable.

Feel free to use my TRR anytime!

-whatever

-Lou

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I've got to get better at multi-tasking!!

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Scott

Lou,

Check out this site:

Google Image Result for http://members.shaw.ca/junobeach/images/juno-7%20sherman%20dd%20tank%20drawing.jpg

Go to the bottom

Lou,

What you probably saw were LVT's like these. They are tracked landing craft and some versions had light tank turrets mounted. Look at the design of the tracks. They were indeed designed to propel the vehicle through the water.

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So.... the DD's propellers were geared to the engine, instead of the convoluted drive train that I enumerated above.

OK.

Thanks

I think I'm just going to shut up now before everyone realizes just how ignorant I really am and kick me off the forum.

Thanks for all your help, Jim - but I have a LOT of Googling to do!

-whatever

-Lou

-Lou

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I need minions.

Don't worry Scarface, noone will say that, actually your DD theat is quite interesting and I'm certain many learnt from it, including myself. Thanks for those who contributed too.

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The Russians also had amphibius tanks...

T-37

T-40


And so did the Japanese...

Type 3 Ka-Chi


Type 5 To-Ku (Sorry, this was the only picture I could find)

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Some nice pictures of Bovington's DD, which uniquely (?) still has it's flotation screen here:
D Day Tanks and countdown to 60th anniversary of D-Day from the Tank Museum Bovington

And a very clear & concise explanation of Straussler's DD system:
Tank Museum Bovington-straussler DD
Including this excellent illustration of the drive, showing how an extra sprocket is fixed to the idler so it can be turned by the track and transmit power to the props:


And some pictures of the first DD based on the Tetrarch (taken from 'tanks') along with more on it's development from the Tank museum: Bovington DD





Straussler was indeed, a very clever man.

Cheers,
Adam.

Good stuff guys, thanks!

Adam,

That diagram sure is easier to see and understand than to explain.

Thanks again.

I just joined your excelent forum. I have a question myself concerning the DD tanks during Operation Overlord. I have put it on my pages of the Shermantank and I sure would like that you guys had a look at it and have your own thoughts on the matter.
The Sherman pages can be located here:
SHERMAN

and the question on the DD tanks here:
http://www.strijdbewijs.nl/tanks/sherman/barbaraeng.htm

Thanks,
Pieter