On the attached pic of the "Duck", there appears to be large plates attached to the tracks - does anybody have any details on what these were, how many of them, and were there other things attached to aid propulsion?
A better resolution scan of this or a similar image shows these plates more clearly. Try going to the IWM site and looking at photo Q14624 or Q14625 (you can search on these numbers but leave a space after the Q). You'll see firstly that they clearly are intended to fall forward after they pass the foremost point of the tracks and so it's logical (a) to assume that they propelled the tank through water (b) that they somehow avoided getting smashed to pieces on land. There is no evidence of any other means of propulsion in the water. There's apparently not many of them, maybe six or seven per track, so progress must have been painfully slow.
Thanks, Gwyn. I thought along the lines you suggest but if the plates fell forward, they would be pushed back against the tracks by the force of the water. Furthermore, it would mean that the tank effectively would be walking on stilts on land.
There is an explanation of this in one of David Fletcher's books. The plates were hinged so that they acted as flaps in water but lay flat against the track when on land.
Yes - a very detailed "paddles were attached to the tracks"!!!! (The British Tanks 1915-19).
A spud-type attachment would have given some propulsion, but hinged plates - despite the photographic evidence - could not have worked on land - see attachment.
If you look at the video of the launching of the Duck, sprung plates should have been visible at the front after the track had gone over the sprocket, would still have been deployed until after they came out the water, and would have been destroyed on land as soon as they came over the sprocket and hit the ground. The only way this could have been avoided would have been to have sprung plates - but then they wouldn't have worked in the water.
Maybe the crew were meant to intervene at some point. If the plates were braced to act as paddles, they would have remained vertical to the track along the bottom and up the rear horns. Along the top face they might have remained vertical or fallen under their own weight if the paddle plates operated by gravity. The only part where the paddle plates would have lain flat would have been on top of the front horns. They would then have hung dowm as they passed over the front idler.
Perhaps the crew were supposed to clip or unclip them as they passed the "cockpit" and the vehicle moved from land to water or vice versa. That's the only way that I can think of.
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Looking at the video on You Tube (https://www.youtube.com/watch?feature=player_embedded&v=hb4J7CmlhKY) there certainly not plates as shown on that attachment on my previous post. Watching the video carefully, there are some kind of plate attached on both sets of tracks. The only thing that could work is a fixed plate with a small upstand giving minimal propulsion. There are hints of something like that on the video at the front end of the Mk IX as it is going in the water, but nothing shows about a large projecting paddle at the rear.
There's certainly not a "large projecting paddle at the rear". I don't think anyone here has suggested that. All there are are what appear to be hinged plates on the tracks, but presumably plates that will only hinge so far. I'd have though that as it moves through the water, the bottom run of the tracks are moving faster towards the rear relative to the hull than the hull is moving forward relative to the water and that therefore there is water pressure against the hinged plates to keep them unfolded whilst in the water. As the hinged plates are pulled up over the top run of tracks they fall flat and remain so until unfolding when they reach the front of the hull. On land, the hinged plates fall partly open but are then forced against the tracks as they lie on the ground.
My best guess is a shallow plate that falls/slides straight down out of the track under gravity. Looking at the not quite clear enough film, some of the plates appear to get stuck in the out position with mud.
In fact looking at the film, I can't see the plates "falling forward" as I thought, so perhaps there's a spring on them to keep them closed, but the spring is sufficiently weak to be opened by water pressure (as described above) so they're deployed when underwater, thus providing the thrust to move the tank in the water.
Found a better photo and the drawing looks like it's correct. I'm with Gywn with the possibility of springs holding them in place. If they're strong enough to pull the plate back flush-ish with the track, the water pressure caused by trying to push many tons of tank forward would be enough to open them up.
The spring might have been strong enough to hold the paddle in the extended position under water pressure, yet weak enough to give way when the paddle touched something more solid, like ground or an obstacle or debris in the water. That way, they could function in the water and fold out of the way otherwise. The spring could have been set loosely, so the paddle would drop into the water position as it passed over the front horn. It would also flop into the position shown above the rear horn.
Just ahead of the plate that is about to crest the rear port side horn there appears to be a raised growser. The other plates appear to have the same companion. The plate seams to have something running between the plate and the tall growser. I don't know if it's just debris. There is also a hook like thing on a track plate low to the ground on the port side centered on the track. debris?
-- Edited by Red truck on Wednesday 2nd of September 2015 12:49:09 AM
That seems to be the most practical solution to the problem, although I don't think the plate would "flop" when it cleared the mud - it would most probably have shot back with a large clang; this would help get rid of any mud starting to clog the spring. However, the video doesn't seem to show this. In fact the first half of the video would seem to be a different trip approaching the water because there aren't any plates fitted, whereas the second part of the video clearly shows the plates lying flat against the top run of the tracks.
Sorry, but I disagree. I go back to my earlier posts. The paddles on the tracks are connected to the track plates by springs that are strong enough to bring the paddles against the tracks when in air, but when underwater the water pressure produced by the movement of the tracks (as described above) overcomes the resistance of the spring and so the paddle moves to a position more or less perpendicular to the track. Obviously there is a limit beyond which it cannot reach, otherwise it couldn't act as a paddle. This seems to be the opposite of what Wayne is describing.
That line of thought is valid only in a water role - something would break if and when the tank reached a solid surface.
Furthermore, if there wasn't a spring, the plate would not lie flat against the track on the rear sloped section, as is shown on the photo and in the video, - it would stick up in the air until eventually falling forward. Wayne's idea of a spring of a certain strength would seem to be valid.
I agree the diagram. It shows what I was trying to express in words.
But would a spring be needed to keep the paddles more or less flat against the tracks so they don't come open when they come over the top run at the front, to save them from being damaged on land?
That line of thought is valid only in a water role - something would break if and when the tank reached a solid surface.
Furthermore, if there wasn't a spring, the plate would not lie flat against the track on the rear sloped section, as is shown on the photo and in the video, - it would stick up in the air until eventually falling forward. Wayne's idea of a spring of a certain strength would seem to be valid.
Tony
No, nothing would break. When the tank moved from water to land the tank moves forward but the lower run of track is stationary on the ground. The ground would simply push the paddles flat against the track as allowed for by the hinge. By comparison in the water there is insufficient friction between the track and the water to keep the track still so the track moves rearwards.
The paddle may lie flat against the track at the rear simply because of gravity, but I'm still attracted by the idea of a small spring just to keep the paddles flat against the track (or almost so) as they come over the top run at the front.
And not wishing to be picky, but I am sure I mentioned the involvement of a spring before anyone else.
Gwyn
-- Edited by Gwyn Evans on Wednesday 2nd of September 2015 10:21:03 PM
