Is the proper track tension in a slack track system, like those on a panther, tiger, t-34, t-44, t-54/55 and t-62 really lower than in a system where upper run of track is supported by return rollers?
If not, then "slack track' is a misnomer.
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Slack track tension
Chuck4
Joined: November 13, 2013
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Posted: Friday, November 25, 2016 - 11:21 AM UTC
RLlockie
Joined: September 06, 2013
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Posted: Friday, November 25, 2016 - 11:57 AM UTC
What is your measure of slackness? Surely the extent to which the top run sags is a function of its unsupported mass? If the same length of track is supported at several points, it will hang less low than if it is not. If it is too slack, it will be thrown a lot, which is why the manual contains guidance as to how tight it should be and crews are taught to check and adjust it daily.
Bravo1102
Joined: December 08, 2003
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Posted: Friday, November 25, 2016 - 01:42 PM UTC
Track hangs and is tight in different places as a tank moves. Remember that track is exerting so much pressure on the ground at the same time as it is grabbing and propelling the tank. You have acceleration via the sprocket and braking to stop and turn. The track has to have so much tension so it will stay on the wheels and not too much so that the pins break when the sprocket is engaged.
Watch lots and lots of film very carefully of moving tanks and how the track moves and tightens and loosens as the tank maneuvers. Pay attention to how the whole weight of the tank can shift while turning and realize if that.track has sloppy tension it's going to fly right off and too tight and it'll snap. Then get yourself two end connectors, a few coins and some string and I'll get the "little joe" adjustment wrench and you'll learn what tanking is all about.
Watch lots and lots of film very carefully of moving tanks and how the track moves and tightens and loosens as the tank maneuvers. Pay attention to how the whole weight of the tank can shift while turning and realize if that.track has sloppy tension it's going to fly right off and too tight and it'll snap. Then get yourself two end connectors, a few coins and some string and I'll get the "little joe" adjustment wrench and you'll learn what tanking is all about.
RobinNilsson
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Posted: Friday, November 25, 2016 - 06:05 PM UTC
It also depends on what kind of track that is being used.
A Pz IV and an M60 both have return rollers but the M60 uses "live track" and the Pz IV does not.
Many WW II Soviet tanks had return rollers just like many German tanks but there was a difference in track sag.
The easiest way to avoid getting ino too much technical details is to check images (videos or still images) of the real thing.
/ Robin
Edit 1.
Some variant of a Diehl live track,
Short sections that curl upward (i.e. inwards when mounted on a tank) It takes quite some weight to flatten such a track.
Edit 2
If the sections had been only three links long the curl would have been even more obvious. I once stood on the two outer links of a three link section and tried to press them flat using my weight (only 220 pounds or so) but the links didn't move down more than a a quarter of an inch. Such a track will not show a visible sag between the return rollers and will sometimes curl upward beneath the sprocket wheel instead of hanging down.
Links to videos posted by Mmeier below (edited after the post below was submitted)
A Pz IV and an M60 both have return rollers but the M60 uses "live track" and the Pz IV does not.
Many WW II Soviet tanks had return rollers just like many German tanks but there was a difference in track sag.
The easiest way to avoid getting ino too much technical details is to check images (videos or still images) of the real thing.
/ Robin
Edit 1.
Some variant of a Diehl live track,
Short sections that curl upward (i.e. inwards when mounted on a tank) It takes quite some weight to flatten such a track.
Edit 2
If the sections had been only three links long the curl would have been even more obvious. I once stood on the two outer links of a three link section and tried to press them flat using my weight (only 220 pounds or so) but the links didn't move down more than a a quarter of an inch. Such a track will not show a visible sag between the return rollers and will sometimes curl upward beneath the sprocket wheel instead of hanging down.
Links to videos posted by Mmeier below (edited after the post below was submitted)
mmeier
Joined: October 22, 2008
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Posted: Friday, November 25, 2016 - 06:16 PM UTC
The two "Panthers" of the Bundeswehr (801/Ulrike/Panther-G and 234/Ute/Jagdpanther) are quite well documentet in modern pictures since they drive/drove around post WWII quite a bit. I.e (and as a starting point)
https://www.youtube.com/watch?v=QCCCKiQWMRM
Since many pictures are "show runs" the running gear is quite visible.
Also searching for "Stahl auf der Heide" will give you some more. That is a yearly show of the Bundeswehr Tank Museeum in Munster with moving vehicles (Mostly post WWII)
And finally "Samur Carousel" will give quite a bit.
https://www.youtube.com/watch?v=QCCCKiQWMRM
Since many pictures are "show runs" the running gear is quite visible.
Also searching for "Stahl auf der Heide" will give you some more. That is a yearly show of the Bundeswehr Tank Museeum in Munster with moving vehicles (Mostly post WWII)
And finally "Samur Carousel" will give quite a bit.
Chuck4
Joined: November 13, 2013
KitMaker: 403 posts
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Posted: Friday, November 25, 2016 - 07:28 PM UTC
By tension, I mean when the tank is resting on even ground and the track tensioning idler wheel is properly adjusted, and the track is under the catenary stress of the upper track run under its own weight, how much tension is there in the tracks?
I think almost everyone uses live tracks these days. But during WWII I think the US was the only major user of live track. Live track is tracks that uses shaped elastic bushings in track pins to give the track a natural curl when not under weight or tension. Dead track is track that use rigid bushings and would flop any which way when not under tension or weigh.
Slack track is where the top, return run of track is unsupported and under catenary tension only along the entire length of the return run. The alternative uses return rollers to support the return run of track.
I think it is possible for a tank to use slack track system with live track as well, although I can't think of one that actually does of the top of my head. I think since the soviet T-62, every other modern tank had used live track supported by return rollers in most of their production versions, although I suspect some early T-72 may still use dead track.
The reason I asked the question is it has been proposed the abysmal service life of panthers and tiger track was caused by low track tension of the slack track design. This supposedly causes excessive wears the drive sprocket. I am not sure I buy that. The reason is I think the natural tension in slack track design is not necessary less than in a design with return rollers. Some pictures I've seen of panzer 4, KV-1, IS-2, show remarkable amount of track droop between return rollers. This suggest to me their tracks are not under any significant tension either.
I think almost everyone uses live tracks these days. But during WWII I think the US was the only major user of live track. Live track is tracks that uses shaped elastic bushings in track pins to give the track a natural curl when not under weight or tension. Dead track is track that use rigid bushings and would flop any which way when not under tension or weigh.
Slack track is where the top, return run of track is unsupported and under catenary tension only along the entire length of the return run. The alternative uses return rollers to support the return run of track.
I think it is possible for a tank to use slack track system with live track as well, although I can't think of one that actually does of the top of my head. I think since the soviet T-62, every other modern tank had used live track supported by return rollers in most of their production versions, although I suspect some early T-72 may still use dead track.
The reason I asked the question is it has been proposed the abysmal service life of panthers and tiger track was caused by low track tension of the slack track design. This supposedly causes excessive wears the drive sprocket. I am not sure I buy that. The reason is I think the natural tension in slack track design is not necessary less than in a design with return rollers. Some pictures I've seen of panzer 4, KV-1, IS-2, show remarkable amount of track droop between return rollers. This suggest to me their tracks are not under any significant tension either.
RobinNilsson
TOS ModeratorJoined: November 29, 2006
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Posted: Friday, November 25, 2016 - 07:52 PM UTC
Ah. Now we are getting somewhere :-)
The tension required to pull a slack track straight is significant (to say the least). To get a slack track completely straight would probably bend the axle of the idler and/or sprocket.
The required tension obviously depends on the weight of the unsupported track links. This depends on the number of unsuported links and the weight of each link.
To answer this, without getting into the realm af guesswork probably requires access to the instruction books or even design documents for the individual types of tanks. The instruction manual would either say that the track shall be tensioned to a specific reading on the torque wrench or, more likely: With the tank on flat ground, tension until the links hang down x centimetres between the return rollers.
I would be surprised if there was a general answer.
/ Robin
Proper track tension for a Tiger I is: hold on, drumroll please ...
four fingers of space between the track and the first road wheel
http://www.lexikon-der-wehrmacht.de/Waffen/Merkblatt/Die_Tigerfiebel_Handbuch_des_deutschen_Tiger_Panzers_.pdf
page 35 (my pdf-viewer claims that it is page 34 so your mileage may wary)
This instruction relies on a simple tool (the big wrench) and a readily available measuring instrument.
The tension required to pull a slack track straight is significant (to say the least). To get a slack track completely straight would probably bend the axle of the idler and/or sprocket.
The required tension obviously depends on the weight of the unsupported track links. This depends on the number of unsuported links and the weight of each link.
To answer this, without getting into the realm af guesswork probably requires access to the instruction books or even design documents for the individual types of tanks. The instruction manual would either say that the track shall be tensioned to a specific reading on the torque wrench or, more likely: With the tank on flat ground, tension until the links hang down x centimetres between the return rollers.
I would be surprised if there was a general answer.
/ Robin
Proper track tension for a Tiger I is: hold on, drumroll please ...
four fingers of space between the track and the first road wheel
http://www.lexikon-der-wehrmacht.de/Waffen/Merkblatt/Die_Tigerfiebel_Handbuch_des_deutschen_Tiger_Panzers_.pdf
page 35 (my pdf-viewer claims that it is page 34 so your mileage may wary)
This instruction relies on a simple tool (the big wrench) and a readily available measuring instrument.
Domagoj
Joined: June 04, 2016
KitMaker: 9 posts
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Posted: Friday, November 25, 2016 - 08:06 PM UTC
Every track has determined tension. But it also depends from surface conditions. My T-55 manual states at least three settings...normal one, for hard surface (very tight) and for mud( very slack). So for sure wear will be faster if improperly adjusted....
For example T-55 it says "if tenion adjustment can not be obtained due to wear remove one link. If during exploatation you remove 3-4 links from each track, you need to swap drive sprockets (left to right and vice versa) and install new track pins. You can use tracks like this untill again 3-4 links need to be removed to obtain tension.
So for T-55 if more than 6-8 links need to be removed from each track they are considered as scrap...
For example T-55 it says "if tenion adjustment can not be obtained due to wear remove one link. If during exploatation you remove 3-4 links from each track, you need to swap drive sprockets (left to right and vice versa) and install new track pins. You can use tracks like this untill again 3-4 links need to be removed to obtain tension.
So for T-55 if more than 6-8 links need to be removed from each track they are considered as scrap...
RobinNilsson
TOS ModeratorJoined: November 29, 2006
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Posted: Friday, November 25, 2016 - 08:13 PM UTC
So the proper number of links on scale model of a T-55 can be different by maybe up to 6-7 links ....
Interesting ......
Gives a whole new view on 'engineering for reliability'
/ Robin
Interesting ......
Gives a whole new view on 'engineering for reliability'
/ Robin
Domagoj
Joined: June 04, 2016
KitMaker: 9 posts
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Posted: Friday, November 25, 2016 - 08:16 PM UTC
Looks like that...manual says nominal number is 90 links for T-55, but obviously due to wear can be few links less than 90 per side.
Chuck4
Joined: November 13, 2013
KitMaker: 403 posts
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Posted: Saturday, November 26, 2016 - 03:12 AM UTC
Quoted Text
Every track has determined tension. But it also depends from surface conditions. My T-55 manual states at least three settings...normal one, for hard surface (very tight) and for mud( very slack). So for sure wear will be faster if improperly adjusted....
For example T-55 it says "if tenion adjustment can not be obtained due to wear remove one link. If during exploatation you remove 3-4 links from each track, you need to swap drive sprockets (left to right and vice versa) and install new track pins. You can use tracks like this untill again 3-4 links need to be removed to obtain tension.
So for T-55 if more than 6-8 links need to be removed from each track they are considered as scrap...
I assume all the stretch in used tracks comes from wear on the track pins, and the bushings. I am amazed the track pins and bushings can wear so much that the track stretches by 6-8 links. That's equivalent to the track stretching 10%, all from making the track pin and bushings thinner. Considering the diameter of the track pins and bushings are only maybe 15% of the width of each link, the track pins would have worn down almost to nothing before the track can stretch 10%
I would have thought if a track stretches by 1-2 links, the bushings and track pins would already be too worn for any further use.
RobinNilsson
TOS ModeratorJoined: November 29, 2006
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Posted: Saturday, November 26, 2016 - 03:29 AM UTC
Quoted Text
Quoted TextEvery track has determined tension. But it also depends from surface conditions. My T-55 manual states at least three settings...normal one, for hard surface (very tight) and for mud( very slack). So for sure wear will be faster if improperly adjusted....
For example T-55 it says "if tenion adjustment can not be obtained due to wear remove one link. If during exploatation you remove 3-4 links from each track, you need to swap drive sprockets (left to right and vice versa) and install new track pins. You can use tracks like this untill again 3-4 links need to be removed to obtain tension.
So for T-55 if more than 6-8 links need to be removed from each track they are considered as scrap...
I assume all the stretch in used tracks comes from wear on the track pins, and the bushings. I am amazed the track pins and bushings can wear so much that the track stretches by 6-8 links. That's equivalent to the track stretching 10%, all from making the track pin and bushings thinner. Considering the diameter of the track pins and bushings are only maybe 15% of the width of each link, the track pins would have worn down almost to nothing before the track can stretch 10%
I would have thought if a track stretches by 1-2 links, the bushings and track pins would already be too worn for any further use.
It's amazing.
But.
I think you forget some parts of the calculation:
1. 8 links out of 90 is slightly less than 9 %
2. After 3-4 links they swapped the sprockets so some of the stretch comes from wearing down one side of the teeth and for the second set of 3-4 links we take some of the stretch on the other side of those teeth.
3. The pins get worn down but some of the material is probably also ground away from the pin holes (bushings ?) in the track links.
It's still amazing, maybe the pins et.c. are overdimensioned to start with. Still amazing ....
/ Robin
joepanzer
Joined: January 21, 2004
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Posted: Saturday, November 26, 2016 - 04:51 AM UTC
Huh, what?
I can't speak for all tracks, but I was on M-1 Abrams.
The track stretches over time.
I have no idea where the sprocket wear would have anything to do with it. and if your track is burning through a sprocket that quick, you ain't doin it right.
On the M-1s, like all tanks, the track is a loop. the front wheel is on a sort of threaded post, that you occasionally have to tighten down to keep tension so you don't throw track. That arm is only so long-when you have extended it all the way-and don't have a replacement track-you take out a track block or two. Then, back off the threaded ring, pop the grease, the arm shortens, track slackens to put it back together. Re-tension the track, then you're on the road again.
I can't speak for all tracks, but I was on M-1 Abrams.
The track stretches over time.
I have no idea where the sprocket wear would have anything to do with it. and if your track is burning through a sprocket that quick, you ain't doin it right.
On the M-1s, like all tanks, the track is a loop. the front wheel is on a sort of threaded post, that you occasionally have to tighten down to keep tension so you don't throw track. That arm is only so long-when you have extended it all the way-and don't have a replacement track-you take out a track block or two. Then, back off the threaded ring, pop the grease, the arm shortens, track slackens to put it back together. Re-tension the track, then you're on the road again.
Bravo1102
Joined: December 08, 2003
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Posted: Saturday, November 26, 2016 - 06:36 AM UTC
Think about this in terms of physics. This entire system is based on friction and resistance. Without it the sprocket wouldn't move the track and the track wouldn't propel the tank. Increasing tension increases resistance and that creates heat.
Ever nearly burn your fingers checking road wheels hubs? Ever see a sprocket ring just snap in half? Ever see an idler wheel catch on fire? There's a lot of heat and resistance in track and that stretches metal. So 9% over the life of a track could be barely visible to the naked eye.
Ever nearly burn your fingers checking road wheels hubs? Ever see a sprocket ring just snap in half? Ever see an idler wheel catch on fire? There's a lot of heat and resistance in track and that stretches metal. So 9% over the life of a track could be barely visible to the naked eye.
Chuck4
Joined: November 13, 2013
KitMaker: 403 posts
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Posted: Saturday, November 26, 2016 - 09:25 AM UTC
I don't doubt it is possible to wear away enough materials for a track to stretch 9%. What I find difficult to believe is the track can continue to function properly if enough has been worn away from the track pins and the bearing surfaces around it for that to happen. For one thing, instead of fitting snuggle, the track pin would rattle around and slop a lot. This would greatly reduce the track's torsional rigidity and let the track twist. Which presumably means it would easily come off of the driving wheel regardless of track tension. It was also magnify the the impact load the track pins and surrounding bushings are subjected to.
joepanzer
Joined: January 21, 2004
KitMaker: 803 posts
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Posted: Saturday, November 26, 2016 - 10:04 AM UTC
I concur with Chuck. Too much stress on the whole system with that much tension.
Burn your fingers on the hubs?
You need a 2404, cause you ain't doin it right
Burn your fingers on the hubs?
You need a 2404, cause you ain't doin it right
Bravo1102
Joined: December 08, 2003
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Posted: Saturday, November 26, 2016 - 10:07 AM UTC
That's why track maintenance is a full time job. Some tanks have little deflectors to knock pins back into the track. Other times the standard operating procedure is for crewmen to check the whole track run, hammer in hand to bang them back in. Even on live track tanks on every stop the loader was supposed to dismount and check for loose and missing bolts.
On M48 and M60 the tracks were ever so slightly wider than the fenders. You could check the end connectors and wedge bolts without dismounting.
Track maintenance is a full time job. Every long halt the driver and loader were supposed to dismount an M48 and M60 series tank to check for track issues. One was banging every end connector looking for "dead" blocks. If it moved or range wrong something needed fixing.
On M48 and M60 the tracks were ever so slightly wider than the fenders. You could check the end connectors and wedge bolts without dismounting.
Track maintenance is a full time job. Every long halt the driver and loader were supposed to dismount an M48 and M60 series tank to check for track issues. One was banging every end connector looking for "dead" blocks. If it moved or range wrong something needed fixing.
joepanzer
Joined: January 21, 2004
KitMaker: 803 posts
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Posted: Saturday, November 26, 2016 - 10:16 AM UTC
I agree with Stephen
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