Gyroscopic Stablizer on M-4 series tanks

Excerpts From M-4 Sherman at War by Michael Green and James M.Brown:Improving the Odds of Hitting a Target:To assist the gunner in combat,the 75mm main gun along with the .30 caliber coax machine gun featured a stabilizing system for both the gun and the sights.It allowed the gunner to fire his turret weapons when the tank was moving by keeping them at a predetermined vertical elevation accurate to within 1 mil of the target.The stabilizer had no control of movement in the horizontal plane due to roll or any changes in direction or movement.Even if a second reference gyroscope had been added the technology of the time would not have permitted rapid skewing of the turret.Because the M-4 series single-plane gyrostablizer could not control azimuth,it did not allow for true shoot-on-the-move stabilization.It did however stabilize the gunners two sets of sights,so that he could see targets at longer ranges without the constant motion as the vehicle moved.An Army manual titled Armored Forces Field Manual(1943)stated"Firing on the move should be discouraged because it is inaccurate and causes an uneconomical expenditure of ammunition.Do so only in an emergency and at ranges under 600 yards" Jim Frances recounts that the stabilizer was useful only on even ground,but on uneven terrain it was next to impossible to use because the up and down movement of the gun made it impossible for the gunner to keep his eye glued to his sight and the loader to insert a shell into the breach.Earl W.Norris,who spent his time repairing M-4s for the 12TH Armored Division recalls that the gyroscopic stabilizing system rarely worked correctly and as a result very few tankers used it.(Sorry if this is not the correct format.I am new at this.)

 

"It allowed the gunner to fire his turret weapons when the tank was moving by keeping them at a predetermined vertical elevation accurate to within 1 mil of the target."

By 1 mil do you mean 1 mile, 1 millimeter, or some other unit of measurement? I'm confused. Also, I've heard of this on the M3 and M5 tanks, but never on the M4, probably since it didn't work well. Suspension was very inferior to ours, even Chrstie, and they had no range/trajectory computers, not on tanks at least. The porblem with the M3 and M5 was the 37mm gun. It was way too light to be an effective ATG. Thanks for the information.

 

The Sherman had it. I think I've read that General Abrams was a firm believer in it but that it took some training to use well.

 

Working from memory, but I think the M3 got gyroscopic stabilisation first.
Also recollection (and therefore untrustworthy), but a bell is ringing that the US tankies could largely live without the stabiliser on introduction as their doctrine was more one of halt-to-fire, (edit - ah, I see that's mentioned above) whereas the British had trained at fire-on-the-move since the early days so found more use for the system.

Like I say, I'm shooting from memory, but will have a dig. There's something at the back of my mind about a very positive UK report on M5s with stabilised guns.
Interesting things; stabilisers.

 

From Hunnicutt.

M3:
75 & 37 stabilised (elevation).
Initial problems with severe friction rendered unusable.
Corrected with counterweights.

T6:
M3 37mm system fitted to 75mm gun.

M4a4e1 (105mm).
Pilot fitted with Westinghouse stabiliser for elevation & traverse.

Experimental mount for M4 tested in August '44.

...

Paraphrasing from further text:
First results unsatisfactory - eqpt. modified.
Testing resumed March 44.
More changes necessary - new tests began in October installed in 75mm M4a3
IBM compared with Ordnance design based on Westinghouse parts.
Both azimuth systems compared with standard M4a3 fitted with elevation stabiliser.
Gunners rotated between systems.
Definite advantage from Azimuth system.
IBM superior but Westinghouse easier to retrofit to existing machines.
First 'standard' fitment to an M4a3 - tested at knox in June/July '45.
Tests declared success - accuracy improvements same as in earlier tests, though improvements required to reliability & vibration resistance.
Further tests postwar, including comparative tests Vs.British Vickers system.

Clint linked to a nice little article on what I think is the Westinghouse Stabliser a while back.
http://books.google.co.uk/books?id=AiEDAAAAMBAJ&printsec=frontcover&lr=&rview=1&redir_esc=y#v=onepage&q=stabilizer&f=false

Interesting little patent showing an earlier Westinghouse interest in stabilisers for boats:
http://www.google.com/patents/US7240630

Lone Sentry has some more on US troops & earlier stabilisers:
Lone Sentry - Tankers in Tunisia:

http://www.lonesentry.com/manuals/tankers/tankers_pp_54_to_60.html :

Hmm, sure I have something on Vickers/UK systems... somewhere.

 

Stabilized Gun for Yanks' Tanks


'Clinton Hanna' mentioned on there.
Led me to a comment that he received a presidential citation for his work on stabilisers:
http://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CDEQFjAA&url=http%3A%2F%2Fojs.libraries.psu.edu%2Findex.php%2Fwph%2Farticle%2Fdownload%2F7894%2F7667&ei=iGCIUeeLNabs0gXhhYDgDQ&usg=AFQjCNF1pcwKQG6uTiZKd-wMDUmJt5T_Jg&sig2=6QbtEUWyEvsMikJr_kFWwA&bvm=bv.45960087,d.d2k&cad=rja

View attachment 18774


Citation winners. Citation winner, Clinton E. Hanna, (right) of the Westinghouse Electric and Manufacturing Company

& 1942 patent:
United States Patent US2391965 - Position Regulated Gun mount

Brief Hanna Biog
Three Awards relating to the stabilisation system:
Presidential Citation.
Howard Potts Medal.
Lamme Medal of the AIEE

 

Welcome to the forum!

Outrageously good First Post! Wowzir!

A topic I had never given a thought to.
Now Iza about to lose and entire day researching this!

Fascinating!

===> Nicely Done! <===

Now... tell us all about yourself!
You've got a mind that I want to get to know! (Fingers crossed for more of this quality.)

 

From my interviews with M4 tank crewmen in the 781st Tank Battalion, the system was used (not disconnected) and helped reacquire a target after movement. The system kept the gunsight "close" to the target in the one axis, so the gunner could reacquire faster than when the system was inoperative.

 

I am sorry to take this thread off topic, but did the Sherman have (or all U.S. Tanks for that matter) a ratio of 60% HE, 30% AP & 10% Smoke as standard, I know that Tankers could fit as many rounds as possible into the vehicle, but by the book was this total right?

I apologise again for butting in.

Yan.

 

I have also seen it as 70%/20%/10%, but nothing official.

A lot would probably depend on the expected mission and what ammunition was available.

 

There may not have been an "official" one during the war or alternately there may have been multiple "official" ones. I believe today the US army a Brigade commander can set the load out but typically delegates it to Battalion which often delegates it to Company. It may end up being designated down at the plattoon or individual TC level and of course stock on hand and mission impact it as well. The ratios above sound pretty reasonable as an average.