I'm reading a book by a guy who was a tank driver in Vietnam.

He mentions "dead track blocks" but he never defines the term.

I assume that a track block is one of the "links" in the track, but what makes it dead?

A track block is "dead" if one of the integral pins is broken. You can tell by the sound it makes when tapping on it, and depending on where it was fractured it may be visible (and may just come apart). Crewman will tap track blocks that are suspicious during maintenance or when they are "walking track". Another failure is if the bushings that surround the pin are worn out causing the block to "stretch". This is checked with a manufactured gage. It's in the list of manufactured items in the TM but I have never actually seen someone use one.

Here is a pic of a "dead" track shoe from the PMCS checks.

I see. Thank you.

Kind of weird that the author of the book has a glossary in the back. He defines "LT" as "Lieutenant" for those of us who have never heard the term, but he does not define "dead track shoe," even though he uses that phrase multiple times.

All we know from the book is that it is something that needs to be dealt with during maintenance.

The book, by the way, is Boys for Men: A Vietnam War Memorial by Derrick Wolf.

It consists of alternating daily journal entries written by two enlisted solders: one from the post civil war army, and one from the journal kept by Derrick Wolf in 1969.

The Kindle version is free to borrow for Amazon Prime members. You don't need a Kindle to read it, there are free Kindle reader apps for smart phones, tablets, and computers. Probably 90% of my non-technical reading comes from this source, the other 10% from the digital material available from my county's public library.

Tanks for this thread.

LOL! Saw what you did there

quote:

Originally posted by jljones:
Tanks for this thread.

Just try to keep it on track, please.

quote:

Originally posted by V-Tail:

quote:

Originally posted by jljones:
Tanks for this thread.

Just try to keep it on track, please.

You deserve a PATTON the back!

Fixing broken tracks in the field sucks, in case you're wondering.

Just one side of an M1 track weighs about 2.5tons, and each section (about 8 pairs of blocks long, IIRC) weighs several hundred pounds.

I was almost impaled by a 4ft breaker bar/pipe that got away from the guys working the big come-along while wenching the two ends back together after inserting a new section.

quote:

Originally posted by 46and2:
Fixing broken tracks in the field sucks, in case you're wondering.

Complete agreement on this!


Adding to the great responses to the OP's question -

A "live" track has rubber bushings between the connecting pins. They are designed so the relaxed state between any two track shoes is actually angled, giving the track a predisposition to curl rather than lay flat.

When properly maintained, the track is actually stretched - for an M60 or M1 series, the crew actually has to stretch the track several inches to connect the ends. (they have a tool for this called a track jack, and yes, it is back breaking work)

A "dead" track, on the other hand, is like a series of door hinges.

If you look at this photo of a WWII Panzer IV, you can see how the track sags between the return rollers:



A properly maintained live track won't show this sag.

When the rubber bushings on a live track wear out or separate from the track block, then that tendency to curl is released, and the shoe is "dead" and needs to be replaced. The illustration that mblinky uploaded shows this - the dead shoe is being carried at a funny angle because that angular tension is no longer being applied.

Caveat - some vehicles, like the M113 APC have a "slack track" - no return rollers. The track, instead, rests on top of the road wheels. These can also be live tracks as well. The difference is just easier to see when there are smaller return rollers.

What is the MTBF for a track block on M1A1 or M-60, understanding that a lot has to do with terrain?

Honestly I'll have to look that up. The biggest issue is maintenance, i.e., rotating track, sprockets, etc, and what type of terrain you operate on. A full set of track costs around $110K, whereas a new set of pads (each block has two pads that can be replaced) costs about $5K. Crewman have a habit of running the track pads down below minimum spec and damaging the growsers necessitating full track replacement. A track that is maintained can go through two or three sets of pads before the end connectors and center guides need replacing. A code F pad still has about 5/8" of material on it so many guys run it lower thinking it is still good when in reality they should be replacing them. Well maintained track can go a long time.

quote:

Originally posted by mbinky:
Honestly I'll have to look that up. The biggest issue is maintenance, i.e., rotating track, sprockets, etc, and what type of terrain you operate on. A full set of track costs around $110K, whereas a new set of pads (each block has two pads that can be replaced) costs about $5K. Crewman have a habit of running the track pads down below minimum spec and damaging the growsers necessitating full track replacement. A track that is maintained can go through two or three sets of pads before the end connectors and center guides need replacing. A code F pad still has about 5/8" of material on it so many guys run it lower thinking it is still good when in reality they should be replacing them. Well maintained track can go a long time.

From the perspective of a former battalion maintenance officer (M60A3 tank battalion in Germany in the 1980's) one of the frustrating things was that we weren't realistically budgeted to support realistic track wear. The operating tempo of tanks in Germany was higher than stateside - long road marches into sector a few times a year, major exercises that involved long distance movement that you just can't get stateside. All of those things take their toll on the tracks. Off-road or unpaved road travel wears things differently, on-road the pads take a beating.

To kind of answer the question above, we could more or less expect to get somewhere in the vicinity of 800 miles on a set of track. That doesn't seem like much, but it is a lot of mileage for a tank. Again, these numbers may well have changed since 1985, and I think the newer track is a lot more robust than what we were dealing with.

Replacing individual track blocks is a ton of back-breaking work, even in the motor pool. According to the official specification, if there were more than three "dead" blocks on a side, the tank was "not ready." (which gets reported, and is a BFD to the Battalion Commander)

I was pretty happy to give them all of the individual track blocks they wanted, but you can imagine this wasn't very popular. The crews (and their company XOs) wanted a whole new track.

As mblinky points out maintenance is pretty much a continuous task on these machines - there are a lot of heavy moving parts under a lot of stress and things wear out.

I kind of miss those days, but then I tend to remember the parts that were fun and challenging and the memories of the times I was miserable tend to get pushed to the back.

Yes the older track (T156?) was actually a lot worse off than the new stuff. On that stuff you had to replace the whole block as the pads were integral to it (and directional, the M88 Herc is still this way). On the newer track (non-directional, T158 LL) the outer pads are replaceable, held on with one nut each. 78 blocks per side (Abrams) with two replaceable pads per. Changing pads is easy as long as you don't run them down so far as to begin to damage the growser. As mentioned tankers always wanted new track as it is easier to replace. Replacing pads is a little more work, especially if they were driven way past their life span. Honestly unless they could show me why the whole roll was code F I would buy pads, end connectors, and even new center guides before I would buy track. Huge difference in price and a few sets of track will eat up a companies quarterly class 9 budget in a minute.

Track work can be exceedingly difficult if put off too long so a good maintenance chief and his tank leader need to keep up on it. Unfortunately it is not one of the more glamorous tasks, and generally gets put off until it breaks as you are chasing more pertinent issues.

T156


T158 LL

jeeze. What a bunch of grousers.

Very interesting thread.

Pardon my ignorance, but are the road wheels and return rollers on a Panzer powered, or do they rely entirely on the drive sprocket?

What about on a Tiger's road wheels with its complicated suspension?