Tom: Much thanks for that cutaway line drawing (it won't allow direct linking, so you will have to copy and paste the link into your browser to see it).

Something that I want to point out about this drawing, and that is this: It beautifully illustrates the access hole in question, and it is covered by a plate. Interesting that we have yet to see one on a surviving example.

Thank you for your insight on addressing the issue of dropping gears into the access hole. Your method would probably without quistion be the best way to approach this.

I'm really itching to make one of these in 1/6 in the future, one that you can take apart and view all of the internals...

Tom I am afraid I don't agree, if you look closely and work out the size and location of the drive wheel that is a direct drive cog to cog.

Anyway to throw more interesting pictures to you take a look at these pictures, especially the Mk IV Tadpole and you were concerned about grenades on a standard Mk IV. -It also clearly posseses the small hole between the two large ones. The captured Mk IV I believe also shows this hole, however picture quality may mean I am mistaken.
These are again from the Vanguard book.

Tom I wonder if the access hatch is for greaseing that chain that is shown in the cutaway drawing, which appears to transmit power to the cog shown in the close up of the hole.

Darren: Thank you for those pictures. The picture of the Tadpole directly correlates with the Emhar kit in regards of the holes (at least from what I last remember..) And your eyes are just fine, that is indeed an open hole just as we have been talking about.

Regarding the sprockets/gears that we are looking at, I hope that we aren't all talking past each other. What I put together from all of the images and the drawing is this (excuse my terminology if it is incorrect):
Starting from center and working towards rear
-Gear on end of transmission/transaxle making direct gear-to-gear contact with...
-Gear on first drive sprocket assembly, turns larger gear to drive the drivechain that connects to...
-Large center gear on second drive sprocket assembly, turns smaller outboard gears (one on each side) that make direct contact with...
-Drive sprocket, which of course moves the tracks

So what we are seeing through the access hole is the inner of the two outboard gears for the second drive sprocket assembly making direct gear-to-gear contact with the drive sprocket?

That is my thought as well, but that is one large hole for simply lubricating a chain or gear teeth.

I believe what you have said is correct as regards the drive. Ref the hole could it also double up as an inspection hatch for the final drive and chain? It may also have something to do with checking allignment of the final drive when using the tensioners.

That would most likely make more sense. I highly doubt that the drive chains were prestretched.

Here is another thought for you to mull over. We have been considering why a hole would be left in the bodywork of a tank without any obvious protection. There are no signs of there having been a bolted or sliding cover, what if it had been just a metal plug. With the sort of terrain and conditions they were used in I doubt very much if a plug would stay put very long after it had been removed a couple of times, or possibly lost due just to the conditions it is exposed to.

Interesting thought Darren. Normally I would think of a rubber plug, but the high expense and low quality of rubber back then would make that seem doubtful. It would be interesting to see what such a plug would have been made out of, and why it was even there in the first place.

Another thought had crossed my mind, and that is this: it is possible, although highly unlikely, that these holes were merely there to perform some function somewhere on the assembly line. I'm not used to holes being so large in this case, but the production of armor is not necessarily my forte..

Wow! I went to bed way too early, and missed an interesting exchange!

I think we're all finally talking the same on the drive layout. (The bigger round plates with the bolts around them incidentally cover the axle ends of the various gears...) The Tadpole Tail unit has a more complcated set-up with two of these cog-wheel gears because to get the extra length it has two loops of bicycle chain that meet in the middle, with the rear one directly turning the sprocket...

The hole could have had a bung (wood?) that was easily lost in use, or indeed they may have left it as a gaping hole simply because nobody thought to cover it up. Either way it looks to be just about big enough to stick a head in for visual inspection, and possibly even to reach in with a chain tensioner or grease gun?

The bigger holes in the Tadpole Tail must be for chain replacement (but why not on the standard Mk IV?), and I assume no effort was made to cover them because the Tadpole Tail didn't get used in anger. I know there were stacks of them sent to France, but they were not installed because they proved to be too weak for use. (The plan was they were a straight parts replacement to be fitted to existing tanks by the field workshop. There are photos of them stacked up in the yard, but the only tank seen fitted with them was being tested in England.) The Emhar kit on my shelf has all these holes in its Tadpoles, but I always assumed that was because they needed access for demonstration purposes and would have fitted some kind of cover if put in service. The Stokes mortar on the rear platform weas an interesting touch, as infantry refused to go anywhere near these bullet-magnets! If only they'd fitted it internally, firing through the roof...

Tom

Yeah, we had quite a discussion last night. I think we are all getting a better understanding of these behemoths, and I feel like we are on the brink of discovering what's up with those holes. Look forward to further discussion down the road

From memory the holes are not that big (about big enough to get a small hand inside) I will have to measure the hole now as well. I promise I will get an answer to the question from Bovington week after next, meanwhile I like the idea of them being corked or a tin lid being used. I suspect though it will be a case of no one considering it a weakness at the time, after all it was the beginning of a whole new weapons system and method of fighting.

Looking forward to hearing what you find out Darren, and I agree with you about the "unexplored territory" situation where everything was new to them.

Just wanted to let you guys know that I am going to be pretty swamped between campaigns and work for the next couple of months so I'm putting these two projects on a brief hiatus. Thanks for your support and look forward to picking these builds back up

NP I will still get the pictures placed here for you along with the size of those damned holes.

Much thanks Darren, I'll keep an eye out for your posts so that I can save the pictures asap in case the network here has another hiccup.

Very, very nice vonHengest!! I am currently building Emhar's kit...it's over in the Armor forum if you would like to take a look.

I am looking forward to seeing some more pictures!

-Andrew

Thanks Andrew, I'll drop by your build and check it out. I love these beasts but am just a little torqued at the lack of r&d that has been put into any of the available kits.

Once I finish up my first three campaigns I'll jump back to this kit and post pics ASAP

The holes that we have been discussing are access points for servicing the vehicle, and are present in all WW1 tanks up to and through the Mk V series of vehicles. The holes are in various shapes sizes and locations, with the worst one I have seen being a tri-angular hole on the outside of the sponsons on the Mk V** tank. The holes on the Mk IV are 6 inches in diameter and never had any type of cover present.

Another question I raised with the staff at Bovington was the door in/at the rear of the body of Mk IV and V tanks between the sponsons. I have been told that the door is correct and was the preferred method of access and escape from the tank, I was also informed that the tanks went into action with these doors open in a effort to clear the smoke and fumes from inside the vehicle.

I hope this information is of help.

This is of great help as always Darren. I shall begin formulating a plan to redo the detail on the inside of the rear areas to match what we have seen in the photos.

I am not surprised about the door being left open during operation. The older tanks/landships had a nasty tendency to pour noxious fumes from the engine(s) into the interior, effectively poisoning the crew and the foot soldiers who were riding along inside. At least this is what I have been told, but it does make a lot of sense given the design of the tanks. I am going to leave this door closed for now as it would require a lot of work to open it up in a convincing manner. However if I ever do build one of the styrene Mk IV/V's I will most likely build it in action with the rear door open.

The following picture on the Lanships site shows a Mk IV Female at the Aberdeen Proving Grounds with a cover in situ, I hope this is of use to you.

http://www.landships.freeservers.com/jpegs_new/number_20/P1010449.jpg

Paul

That is indeed of great use Paul, and thank you. I need to find out what's really coing on with these things, but this picture may indeed save me from a good amount of surgery

I have a problem with that picture as having looked inside the real thing and spoken to staff everything I have seen and been told says that there is an opening and it is not covered, if you look at the bolt in the centre of that plate what is it going to bolt too?

I don't know either Darren.. It appears to me that the plate on that particular tank is welded on, but that doesn't explain the nut or what it is attached to. There certainly isn't anything behind the plate for the nut to attach to as there are clearly just gear/sprocket teeth.