Armor tracks: "live" vs. "dead"?

You've got the main idea hammered down.
Live tracks refer to a vehicle equipped with return wheels, the rollers that support the upeer run of the track, like the M60, Abrams, Leopards, etc.
Dead, or slack tracks, refer to AFVs that do not have this feature, wherein the track rests on top of the road wheels or sags under it's own tension.
Both types have their pros and cons:
Dead tracks require less maintenance and don't gather that much mud, but can be thrown more easily.
Live tracks gather mud and generally take more maintenance to the entire suspension sytem and collect more mud, but have a much reduced propensity for being thrown.
Personally, I don't mind a few extra hours doing veh. maintenace if it means that while i'm jockeying out of  or into a fire position I don't throw a track, but tankers from different nations will all probably have a different view on this.
Through the mud and the blood to the green fields beyond.
Cade

Some of the tranny "forward" versus "in back," if I'm remembering right, has to do with the way the steering connected to the transmission. 

If you are using mechanical clutch levers and the like, having those linkages be short means not needing to amplify them.  That "wants" the transmission forward near the driver and the driver's controls.

Now, if you have a form of torque converter, you can use axle braking for steering, you can use cables for the brake levers (I'm likely wrong, but that's what I remember the Soviets using).

Hi,

"Live" track  is tensioned in it's design and will "curl" up on itself when not fitted to a vehicle and tends not to sag while "Dead" track is not and will just flops about, hense the track sag on dead track. The difference is not to do with a vehicle having return rollers or not, see the M113 which has live track but no return rollers. Tigers and Panthers didn't have return rollers while the Pz.III/IV did and they all use dead track. And the Russian KVs, JSs with rollers and the T-34 without again all with dead track.

This is why you don't see track sag of most US vehicles because the live track doesn't sag like dead track as used on German and Russian vehicles.

Hope this helps?

Cheers
Terry A

To add to the confusion...

Live track is under constant tension and is kept tight.  This is usually accomplished by a hydraulic piston that keeps tension on the idler sprocket by pushing it out from the vehicle and keeping the track tight.  The piston looks kind of like a shock and is kept "pumped up" with grease that is added to it to maintain the pressure.  As noted above, the vehicle can have returm rollers or not.  All US AFV's since WWII have been live-track systems.

 

Dead track is not under constant tension and is much looser on the vehicle.  It is usually held on with a fixed idler sprocket and the number of track links maintains the track on the road wheels, return rollers, etc.  As stated, it is easier to throw track with dead track, that is one reason Soviet/Russian tanks all carry an unditching log.  It is also used to put the track back on when it is thrown.  The Soviet Union used/uses the dead track system since it is cheaper to produce and easier to maintain.

So do British & other NATO forces all use live track then?

shaun68 wrote:

So do British & other NATO forces all use live track then?

 

Depends on the vehicle and the timeframe.  Most modern Brit/NATO vehicles use live track, like Leopards and Challenger tanks.  Older Brit vehicles such as Centurion tanks used dead track.  Basically, Christie type suspensions use dead track.  Soviet and older Brit tanks used Christie supensions.

Thanks Gino.

Cheers

To put in my , "live" and "dead" track refers specifically to the track / track blocks and has nothing to do with what vehicle/time period or how it is mounted. Its easy to discern the difference between the two when a section or whole length of track is "unbuttoned" or removed from the vehicle. "Live" track will have an upward curl on its ends, whereas "dead" track lays completely flat. "Live" tracks have rubber bushings inside the blocks that the track pins are driven through to connect them. Track pins are not round, rather they are octagon and require each block be attached at an angle from the ground to line up the bushings for the pin. "Dead" track lacks these bushings and are basically connected metel to metal with bolts and brackets. For example, the M1A1 (if I remeber correctly, didn't have any pics in the album) has "dead" track, and has no pins that are driven through the blocks. Instead the blocks are connected in the center and on the ends with brackets. Below is a pic of "live" track highlighted in red.       

 

Concerning support and lack of support rollers. This makes no difference on "throwing" track, it can be easily accomplished with either type. Keeping from "throwing" track has more to do with the skill of the driver, avoiding sharp / continouous turns in loose gravel, mud, or soft terrain such as sand. It is the build up of such stuff between the track and sprocket or idler, allowing the track to roll off to the side since the guides on the track blocks will no longer run in the grooves of the sprocket or idler. Below are pics of an AAVP7A1 and an LVTP7 RAM/RS. Even though it looks very different, both styles utilize 85 blocks per side(new, eventually dropped to 83 after continuous wear and stretch of the bushings). The return rollers help with tension, but track tension is provided by "pushing" the idler wheel away.

  

 

                                                                                                                                     

Don't know if I contributed or confused, kind of hard to explain without drawings and pictures.                                      

Live track blocks are constructed with a "live bushing" around the track pins in the block. notched to . When the track block rotates off the sprocket teeth, this live bushed pin unloads and gives support to the next block, thereby reducing track slap, in conjunction with the support roller. This allows the tank to acheive higher road speed,  gives a smoother ride for the firing platform and promotes track retention. The sprocket is designed to propel the track by engaging the end connectors, outboard and inboard. This design has been used on US armor since the 40's.:

Dead track, usually associated with the Christie suspension, simply relies on a steel pin to secure block to block. Since there is no live bushing, there is no need for end connectors or support rollers. Therefore, the track is propelled by the sprocket teeth engaging the track block itself.:

As to the location of the sprocket, fore and aft, the design initiative is to move vulnerable drive components to the rear of the tank, thereby minimizing battle damage and allowing room for armor plate. US Army doctrine (as seen with the M1) is to maximize special armor on the front of the vehicle.

This advantage cannot be realized on personnel carriers for obvious reasons. Curiously, the Israelis purposely designed the Merkava with forward drive components, to accomodate infantry in the MBT.

 

regards,

Steve

Great info shared in this thread guys!  Kudos all around.  I learned lots!

deattilio wrote:

To put in my , "live" and "dead" track refers specifically to the track / track blocks and has nothing to do with what vehicle/time period or how it is mounted. Its easy to discern the difference between the two when a section or whole length of track is "unbuttoned" or removed from the vehicle. "Live" track will have an upward curl on its ends, whereas "dead" track lays completely flat. "Live" tracks have rubber bushings inside the blocks that the track pins are driven through to connect them. Track pins are not round, rather they are octagon and require each block be attached at an angle from the ground to line up the bushings for the pin. "Dead" track lacks these bushings and are basically connected metel to metal with bolts and brackets. For example, the M1A1 (if I remeber correctly, didn't have any pics in the album) has "dead" track, and has no pins that are driven through the blocks. Instead the blocks are connected in the center and on the ends with brackets. Below is a pic of "live" track highlighted in red.

 

 

Yes I can confirm this.  My grandfather was a tanker in the 50 and we've discussed in length the merits of dead/live track

M-60 series and the Abrams family all have live track. The end connectors are held in place by wedges that are drawn into beveled flat spots on the pins by bolts. This causes the ends of the track to spring up when it is laid out on the ground and properly positions the bushings inside the track block. The pros and cons have been pretty well stated already.

Yo, Spamicus,

You learn something every day! This explains the photo on p18 of the Verlinden Abrams book (Warmachines #6) -- early-build Abrams undergoing maintenance, one of them with a parted track. I've kept looking at it and wondering 'why is that heavy metal track curling up at the end, just like the vinyl ones on classic kits?!' Speaking of which, I've found a few modellers lately who look back on 'rubber bands' with fondness -- link and length may have crisper detail but the workload is heavy, and they don't 'roll' like the old ones. My new Trumpeter M1A1HA comes with both options, link and length on the sprue, or a pair of really heavy-duty vinyls that sure look the part.

TB379