Firefly tank

[David Herbert]

Good question about what they are doing with the tracks of the Sherman in post 16.

I agree that they are removing them but it would be far easier to do one at a time as you can still move the tank with the other track. Also it is normal practice to break the track under the sprocket as that way when you put it back on you can use a rope round the sprocket as a capstan to pull the track forward and when the teeth engage the top run of the track can be kept in tension while you re-connect the track. Done right on firm level ground it is not too much of a job for two people, the worst bit is getting the end connectors off, made worse by the fact that the proper tool was designed to fit Stuart too and is realy not man enough for Sherman track.

David (another one!)

[David Dunlop]

Knowing nothing about tank maintenance, but a bit about UC's, I will just toss this out for review.

Would a brand new Sherman require a break in period for it's tracks, like a new Carrier does, necessitating removal of one or more links to maintain correct tension?

Earlier in this thread it was mentioned the regiment had only just received new equipment shortly before embarking for Normandy. Perhaps they needed to break in the new track as quickly as possible before going into action and if that was their priority, it would also support the lack of markings being applied to them: time spent being painted up was time lost for crews to get used to the new equipment.

David

[Bob Cohoon]

I read a bit in an M4 manual I am lucky enough to have, and it`s possible they were turning them around. Apparently, if they have a reversible type track,like the steel cleat ones on that one, they can turn them around which will extend the life of tracks with worn guide horns ( where the sprockets bear ).Turning them around gives brand new faces for the sprockets to bear against. They did that both sides at a time, doing half the track at a time, disconnecting and re-connecting below the drive sprocket, 16 " in front of the first bogie. They use another tank to pull the tank, being worked on, forward , and can use the drive sprockets, with a tow cable wound on it with a steel bar as the cross pin in the sprocket, to pull the tracks on when doing the other half of the job. The sprockets can be reversed, too. They say, also, to watch that the track tension doesn`t get too much slack, as this will contribute to throwing a track in tight turns .They probably put wheels in to help, as the steel cleat tracks must be very heavy

[motto (RIP)]

That all fits the picture Bob. I was going to suggest that this wasn't a track change but some other form of maintenance. There are no new tracks in sight and the close proximity of the other tanks would cramp the operation as the replacement track would need to be laid out and the tank towed off the old onto the new. I don't know any other way to do it in the field.

David M

[Richard Coutts-Smith]

Y'all forgot about the CMP up the back.
Nice "In The Background" photo.
Rich.

Just noticed it appears to have a mechanic crouching at the bumper, so that narrows it down to a Ford.......

[motto (RIP)]

In answer to your question about the possibility of requiring major adjustment after new track has worked a bit David, I don't believe so. From what I know of Sherman track the links or blocks were articulated using pins set in rubber, there was nothing to wear as the relative movement was allowed for by the flexing of the rubber.
The really clever part is that the links or blocks are set at a slight angle to their neighbours so as the track wants to roll itself up. To flatten it out flexes the rubber in one direction while going around a sprocket or return roller flexes it in the opposite direction from its null position. It's what is referred to as a 'live' track.
That's the track that I'm familiar with anyhow. I expect Sherman track all worked on the same principle but may be wrong about that. This type of linkage is still in use today on the M113 track and no doubt others.

David

[David Herbert]

Refering primarily to Bob's post (no.25), I think that he has come up with the most credible explanation of what is going on with the Sherman track in post 16. Alternatively it could just be crew training or even sadistic punishment!

Sherman tracks do not have a break in period of great stretching in the way that carrier track does. When a track is split or replaced, the end connector securing wedges MUST be checked for tightness several times once the tank is driven. They do not work loose but it is very easy to think that they have been properly installed when they haven't. Also if a new track has been fitted it will need re tightening at least once as the rubber bushes get used to being under tension. Once bedded in though it will not need the continuous tightening and removing links that dry pin tracks need. In fact you should never take links out of any 'live' track to maintain tension.

As Bob said, there are sugestions in some manuals about reversing the end connectors or whole tracks to even out wear on the part of the end connectors that the sprocket teeth drive. Apart from being incredibly hard work, it is more a theoretical benefit as they actually do not wear that fast and do wear on both drive and non drive faces, which is not really what you would expect. Depending on ground conditions the end connectors last much longer than most types of link and were expected to be reused when building up replacement tracks.

Actually the only type of Sherman track that could correctly be turned end for end was the flat rubber link type. The cast steel design in the photo in question is installed the correct way, with the larger single bar leading the two smaller bars on each link. Obviously it will work back to front but that is how it is designed to be fitted.

Another small point is that a Sherman tow cable is far too thick to wrap around the sprocket hub and use as a winch to pull the track on. If you tried it the cable would be a real pain to use and would never want to go straight again!

Motto is quite right in his observations about 'live' track, it can be single pin (like the original M113 track) or double pin with end connectors (like Sherman and most modern tanks) but the rubber bushes are usually made so that there is a curve to the track naturally. That way it actually pushes down on the ground between the road wheels and does not have to flex so much around the sprocket and idler. It is also much harder to work with as it has its own idea what it wants to do.

Of course the Canadian dry pin track that was used by them on Grizzlies and Sextons is the exception to all other Sherman track but it was designed to be robust and easy to maintain as the primary requirements (there is a very full account of its development in CWM).

Hope this is of interest

David