Firefly tank

[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]

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

[Bob Cohoon]

Here are a couple of photos from the 1942 manual I will try and attach. They mention the puller is a Simplex , a well known manufacturer ,and they used chain to adapt to the track ends

[David Herbert]

Thanks for posting those pictures Bob. As you see they have broken the track under the sprocket and run it off backwards, much easier.

As you say the jack they are using in the photo is made by Simplex and is actually a standard multi purpose jack of the day. I got mine from a non military autojumble here in the UK. They very quickly realised that the use of chains was a bit ackward and supplied adaptors that hooked into the track and the jack but that scheme didn't last long either.

Next came specially designed track jacks (also made by Simplex) that were used in handed pairs and were designed to be a universal tool for all WW2 US tracked vehicles. In theory they would also pull the end connectors which would have been a great help but they were not really up to that job on Shermans once the track had been in sevice for a year or so and gone a bit rusty. They were long enough that you could hook onto links that were either side of a damaged link, take the tension with the jacks, replace the link and remove the jacks, all without un tensioning the track.

Don't forget that the manual that you are quoting from is the first attempt at a TM on Sherman and was written before any real experience had been gained in service. Later editions are a bit more realistic.

David

[Lynn Eades]

With reference to Motto's and David's posts about "live track", I don't have too much knowledge about tank tracks, and I agree they are "live" tracks, but not because of the way they are made, but because a tank track or "live" track "soaks up" what it travels over,(the bottom rollers move up over objects, and allow smooth passage over them) as opposed to a bulldozer that climbs up on to an object and when it passes its balance point it flops down the other side This is not a "live" track because it has a fixed track frame with fixed bottom rollers.

[David Herbert]

Sorry, Lynn, but you are wrong.

What you describe is a tracked vehicle with suspension. Live track is most definately the track itself. Instead of each link being completely free to hinge to its neighbour (it just lies there as if dead) it is hinged with rubber bushes so that each link not only pulls the next one but also tries to even out the angles at the pins. When working on this type of track it very much has a life of its own and stores up a lot of energy when folded over onto itself which can result in it suddenly flipping over as it tries to resume its built in curve.

Just to be really pedantic "bottom rollers" is the term used in construction plant. In tanks and similar military vehicles they are known as "road wheels" if they are big ones as on Cromwell probably because they are really too big to look like rollers. On Shermans and even Churchills the manuals call them "bogie wheels". In tanks that have small rollers to carry the top run of the track the terms "top roller" and "support roller" are normal. You will certainly find variations on what I have just written but my point is that "bottom roller" is not a term used officialy with tanks.

I hope that I havn't offended

David

[Lynn Eades]

No David, not offended. I just had an adjustment made to my data storage system.
BTW this reply has been severely altered, after a quick circuit of google.

[Robert Bergeron]

Guys,

The Shermans in the picture are so new there are no machine guns mounted on any of them. No co-ax, bow or crew commander MG.No towing cables , Jerry cans , antennae , no nothing . Looks they were just dumped or driven on the side of a road somewere in England to be seviced , equiped and readied for action.

That there be no markings is not suprising as more important stuff needs to be done first like loading the MG's and radio equipment .

Nice , colour and stenciled markings is the stuff you do when in garrison not when you are about to embark on history's most important flotilla or Armada to date .

On the LCT's we see embarcation markings in chalk . It did the job.

The silly stars our allies insisted on us painting on the sides of our Shermans were just so nice to the Jerry's as aiming marks. Just like the nice standing MG mounts on US Jeeps. Better targets , soon jettisoned pieces of bad and ill conceived in garrison equipment.

I see a barrel of grease and a wooden box in front of the first one . Would that box contain a Browning MG ?

My two cents as an amateur history buff and modern military man.



Cheers . Salute a veteran and thank him today and every day of the year.

Robert