On Fri, 02 Aug 2013 12:09:24 -0500, Tim Wescott
wrote:

On Fri, 02 Aug 2013 12:05:18 -0400, Ed Huntress wrote:

On Fri, 2 Aug 2013 15:49:25 +0000 (UTC), David Lesher
wrote:

Side topic:

I have read that the Wehrmacht's tanks, esp. the later ones that were so
large, suffered badly from final drive failures. So much so that a road
march of them for any distance would disable say 33%. This helped me
better understand Allied anti-railroad tactics...forcing them onto the
roads.

[They also lacked tank retrievers of enough strength to salvage
them....]

The failures were because of 2 basic reasons: they lacked sufficient
chromium to fully harden the gearing, and the second was my
question.....

This source (that I now can't find again...) said there was a way to
better design/machine the ring gears needed, but Germany lacked the
tooling/resources to use that approach, and instead used less strong
methods. I inferred the better way needed more time or a better mill but
beyond that, I don't know.

I'm curious about what that might have meant, and wonder if anyone can
speak to gear design issues...

Only in fragments. If the issue was an internal-tooth ring gear, as for
a planetary gearset, that wasn't a milling issue. That was a gear-shaper
issue. They also can be broached, but I don't see that as likely during
the war, on big gears. Perhaps that's the tooling that Germany lacked.
It requires very big pieces of high-quality tool steel, and chromium
shortages would be an issue.

Germany had some very good gearmaking capability but that of the US was
better at that time. Gleason was the world leader in making big, strong
gears of several types.

BTW, the US had power-transmission issues on some tanks at the time,
too. Caterpillar made a big 24-cylinder porcupine diesel engine that was
supposed to be the end-all for our largest tanks. But it had so much
torque that it twisted off driveshafts like they were swizzle sticks.

Steven Ambrose has some interesting comments in "Citizen Soldier" about
the Sherman tank. The allied soldiers in Europe reportedly disliked it
because it was so wimpy compared to the big German tanks -- but
Eisenhower could get three Shermans for every one big US tank (I can't
remember what we had), and a Sherman used less gasoline. The thinking
was that as soon as the allies broke out in Normandy and started for
Berlin that the mobility of the Sherman tanks would outweigh the size
difference.

It's hard to say who was right, but we did win using those little tanks.

Yeah, I've always wondered how we shot up Tigers with Shermans. Did
the Shermans have the high-velocity 90mm guns, our answer to the
German 88s?

--
Ed Huntress