Engineers and Tankers I need your help!!!

[Reagans Rascals]

Hey guys, I'm currently taking a Material Failures course and we've been handed a part, with no background information besides stating that it came from a U.S. Army tank, and have been asked to determine the type of material, specific failure mode, what possibly caused it to fail, and potential upgrades to the component to resist failure under similar loading conditions in the future.

The component is a rubber compound of some type, and it obviously failed due to torsional overloading.

I need your help to figure out what this part goes to. I was told, although I believe incorrectly, that this component is from the track of the tank. No further information provided to us. I do not believe, in anyway shape or form this is from the track. This is some type of knuckle linkage or roller. It is approximately 4 inches long.

If I can identify what part this is, it will greatly help me develop the possible loading conditions of use and allow me to create my boundaries for my FEA analysis.

So any of you guys out there with tank experience please help me figure out what part this is!

Failed Component.jpgFile_000.jpgFile_001.jpgFile_002.jpg

[trackmagic]

Is that a metal shaft through the center? Is it part of this block?

Normally if something is mounted on rubber it is to give vibration isolation. Maybe something to do with the optics?

ETA: Another possible use would be some type of coupling that needs to bend and transmit torque (like a CV or U-joint):
https://www.google.com/search?q=rubb...w=1327&bih=842

[Lefty223]

Looks to me like a typical urethane boat trailer roller used on the center tongue or bow stop on small boat trailers. These are made with 1/2" or 5/8" diameter shafts. Look up parts on Hamilton Marine or West Marine web sites.

I wonder if it somehow is maybe being used as part of a roller to feed the round or the next round to be fired into the breech, as part of the loading or round feeding process? Or if used for the track, maybe it isn't a 'drive' piece, but a service piece, as part of the tensioner system (like a come-along cable runs over it) when a track is replaced.

Tanks also usually have a travel support to rest the barrel on when transporting, so as to reduce stress on the elevation system, but I can't believe they'd use a $8 boat trailer roller ... unless of course they charged the Govt $210 for it!

See pictures of rollers here, made by C. E. Smith Company: https://www.westmarine.com/c-e-smith...17_513_002_004

[Lefty223]

FYI if your part rotates on the shaft you showed ... it isn't driving anything. I'd guess that it sheared as the mechanism jammed while the part rolling over it kept moving. Check the ID of the roller for drive features.

Or, maybe it wasn't rotational shear per se (is your guess or what?) but maybe the cap on one end came off, causing 1/2 the roller to be off its axle/shaft and while rolling the 'rubber' roller as unsupported by the shaft just couldn't hold the weight (without the axle/shaft support) and that's when it split.

[GH41]

I am with Lefty... Boat trailer roller adapted for some use on a tank.

[Averageman]

I'm pretty positive that, that isn't a piece off of a Tank, but bear in mind a lot of people who aren't "Tank People" call a lot of stuff "Tanks" that really aren't Tanks.
I've been on "Tanks" since 1981 and I still am, I'm not real familiar with where that might be located on either a later M48 series, a M60, or a M1 series Tank. I've served on each of those as a crew member or a trainee on the M48 A-5's, I'm not remembering that particular piece.
That may well feed a recovery cable/tow cable off of a vehicle I am less familiar with that is not a "Tank", but a recovery vehicle that might be called a "Tank".
If that is the case I have some ideas about why it failed, it simply isn't made of the correct material. The correct material would be a hardened steel.
Nylon or rubber may feed easier, it may actually be cheaper to replace, but it will wear at a much faster rate and be susceptible to increased wear under pressures required to recover vehicles in the 20 to 70 ton weight level. It will likely be susceptible to environmental conditions such as UV rays depending upon where in a vehicle it is mounted.
I'm fairly adept and familiar with recovering real Tanks, even light APC's. The pressures present when performing these tasks are pretty amazing and the equipment has to be highly maintained and regularly inspected in order to remain safe and viable for recovery operations.
The last time I operated a winch in order to recover a APC was two weeks ago, so I'm still fairly familiar.

[dwhitehorne]

Not a tanker but everyone is looking at it as a possible cable guide or roller that would wear easy. Any chance it is suppose to be vertical like the left photo as damper/bushing that is compressed between two objects. Maybe like keeping components from bottoming out. David

[Averageman]

Not a tanker but everyone is looking at it as a possible cable guide or roller that would wear easy. Any chance it is suppose to be vertical like the left photo as damper/bushing that is compressed between two objects. Maybe like keeping components from bottoming out. David

It's going to fail for the same reasons. Even a guide or a roller is going to be subjected to some pretty crazy pressures.
A Twenty ton vehicle in a ditch at a 40 percent side grade (tilt), might require a substantial amount of pressure on a guide that would require more that nylon or rubber could ever achieve.
One might think that, "It's only a Guide", but consider angle and pressures other than towing (such as maintaining the vehicle from tipping over) as the vehicle is being towed out of a ditch or hole.
Geometric pressures on angles that you might never as an engineer consider possible might likely happen when you have little or no experiance recovering vehicles under battlefield conditions.
As an example, on vehicle may be maintaining the vehicle from falling over on its side while a heavier and more capable vehicle may be pulling the vehicle out of a steep ditch, while even another towing vehicle may be applying pressures to one side and slowly releasing tow cable as the vehicles come out of the ditch.
Three vehicles, all pursuing the same result all releasing or pulling on the vehicle on different directions in order to keep it upright and reduce damage as it is recovered.
At some point it becomes an "Eyeball Exersize" rather than a math problem.
The last thing you want in this consideration is wild variables in;
A) damage to a tow/winch cable.
B) damage to some sort of winch component.
C) variables in just how solid or water filled the ground in the area might be.
You take all of these thing in to consideration, you wildly overestimate what you will need to do the job and hope like hell you dont do this stuff under fire.

[Rayrevolver]

Never worked on tanks but it could be part of the track system.

Possibly smaller than an Abrams track or maybe it is half of a track shoe, know-what-I-mean Vern?

https://www.iso-group.com/sustainmen...156-Track-Shoe

[Reagans Rascals]

Thanks for all the replies guys, I greatly appreciate it. The cable roller idea does seem to hold up really well. My instructor specifically stated it was from a tank track, however I know this to not be the case. After observing the FTIR Spectra its been determined the material is MSBR (Modified Styrene-Butadiene Rubber). I honestly thought it may have been the center section of a guide roller for the track, where the alignment jegs protruding out from the track follow the V-groove in the roller to help keep the track centered. This could possibly explain the torsional shear, even though its not a driven roller. Maybe something became stuck in the track, or maybe it was damaged, and as the track rolled over the roller it pulled the debris or damaged part through the roller causing it to catch and basically shear the roller. The shaft in the picture is part of the component. But I don't believe this part is big enough to be a track idler or return roller.

I'm open to any and all ideas of what it may be or possible loading conditions you guys might think up.

If it is a cable roller, and it was simply just made of the wrong material and being subjected to a very high load (40 tons) at an off-camber angle, would that cause grooving or like deformation in the rubber? As the part sits right now it doesn't show any signs of grooving or like tearing.

Thanks again for the help guys.