Military vs Commercial track sprockets

An Idle question: Why do military tracks drive the front sprocket while Dozers drive the rear sprocket ?

The Cat High Drive system aside (which allows better final drives vs track wear)

Front sprocket lets the track on the ground have less power on it, lets the suspension work better. Also approach angles to clear obstacles. Dozers have rear sprocket and high sprocket because of torque and layout of the machine,a whole bunch of things like balance etc. Tanks don't have a big blade hanging off the front.

It's partially just the logical layout for power flow, partially the physics of efficiency. Dozers are designed to push, tanks are designed to go fast. Dozers put the engine up front for balance, and to deliver power to the track to pull with maximum efficiency, you put the sprocket at the rear to pull the bottom of the track directly. On a tank they went with engine to the rear to protect the engine, allow the driver to be close to the front for visibility and to keep exhaust and heat behind the crew space. The natural power flow from a rear engine is forward and then split to either side.

There may be other reasons.

One thing I've wondered about is the difference in tracked vehicles with suspension, if you pull from the front you load the recoil and the suspension to a degree which probably gives a more comfortable ride at speed.

I remember a thread on the usenet about tank design. Posts by people in that trade.

*Everything* in tank design is compromised for armor and ordinance packaging. Suspension and transmission are necessary, but are secondary to gun and armor. Like lantraxco says; logical placement of components within the available envelope.

(Drivers prob don't mind having transmission and drive axels between them and the front armor and the enemy...)

Jim D said:

I remember a thread on the usenet about tank design. Posts by people in that trade.

*Everything* in tank design is compromised for armor and ordinance packaging. Suspension and transmission are necessary, but are secondary to gun and armor. Like lantraxco says; logical placement of components within the available envelope.

(Drivers prob don't mind having transmission and drive axels between them and the front armor and the enemy...)

Click to expand...

The case for mechanical components forming part of the protection package for the crew is taken even further by the Israeli Merkava MBT. These have the engine, transmission and final drives at the sharp end of the tank, thus offering the ultimate in protection. For a nation with a small population such as Israel, it is much preferable to lose a tank, but save a crew.

Most Modern Tanks and APC's have the drive sprocket in the rear
Russian T-34 of WWII was rear drive.
American tanks rear drive begin with the M-26 Pershing, late WWII
Another reason for the Merkava's front drive is it carries Infantry in the rear

OK, from a US Army retired Armor Crewman. Most armored personnel carriers have the engine up front and to one side with the drivers compartment alongside of the engine. That keeps armor protection against small arms fire between the infantrymen and the enemy as they dismount the vehicle. Kenh is correct about the Merkava andit's drive setup. On the M1 tank there is a lot of armor protection in front of the driver. The drive from the M26 onward for US tank design were all rear drive. Part of the design principal of a tank is speed of repairs. On the M60 and M1 tanks you can have the power pack (engine and tranny) sitting on the ground in about 15 minutes. For combat the power pack comes complete with little to switch over from one to the other. An engine of tranny failure can be fixed in as little as 1/2 hour.

And yes crew survivability is extremely important. You can draft a trained truck driver or cook off the street. It takes time to train a tank crew member. 6 weeks for a driver or loader. To be competent, about 18 months for a gunner and even longer for a tank commander. I don't know about today but for a very long time a tankers personal weapon was a pistol. The idea was that if the crew had to abandon a disabled tank they would make their way to the rear to get another tank. The brass thought that if they issued tankers rifles or sub machine guns that they would dismount and try to fight as infantry. The M60's did have 2 M3 sub guns but there again were for self defense while moving to the rear. When I retired in 1996 we had one M16 as a crew served weapon. It was there for which ever crewman was pulling OP in a defensive position for self defense so if needed they could fight their way back to the tank.

Now today the infantry guys have so many gadgets that they are no longer considered as expendable as they once were. Can't draft a trained GRUNT off the street either.

WFIW: GRUNT was an actual US Army acronym. Stood for "Ground Replacement Untrained". Prior to the US getting into WWII they ran people through basic training and with the exception of air crewmen sent them directly to a unit with GRUNT on their orders and they would learn their MOS (military occupation specialty) by on the job training. With the massive build up they quickly learned that under combat conditions units didn't have time to train these people. The first MOS's that received advanced training in their assigned MOS were mechanics and truck drivers. The last MOS to get stuck with GRUNT on their orders were infantry. They finally realized that new infantry soldiers were more effective and had a better chance of surviving combat if they had extra training past basic.

Rick

To all ... Thanks for posting your thoughts and experiences. :drinkup