High track dozer

I would suppose the high drive sprocket not running in the dirt and muck would be a plus no drop box on the finals also longer rails would last a bit longer I suppose. just a visual assumption from a guy who only has standard track dozers.
 
Easier repair I think. take off tracks and pull trans and final drives from the outside. Newer hystat drive machines seem to be going back the other way.
Later Bob
 
The main idea behind the high track machines was ease of maintenance. With CAT, on a standard, low track machine, if you have final drive problems it is usually necessary to pull the track frame to do any kind of work. Too, if the drive pinion was screwed up you had to pull the seat, fuel tank, etc to access the steering clutch. With a high track the final drive is a planetary and it's all inside the sprocket assembly. Basically if there is a problem, you break the track, set the assembly out, and the repairs are easily handled from there, all without having to pull the track frame, etc.
 
Your right in that, there are a lot of mfgs making new, low track machines that are hydrostatic. In fact, Deere/Liebherr makes one. The bad thing about them is that the drive motor/planetary is located on the track frame, and the hydraulics has to get out to them. To get there everything runs through the shaft the frame pivots around. With that setup, when the bushings in the pivot joint go bad the track frame gets cocked, and starts hitting two plugs that are in the pressure ports. The plugs then start leaking, telling you that the bushings are completely worn out and need replacement. I really don't think the designers planned it this way, but that's what routinely happens.

The fun part is trying to pull the track frame to replace the bushings. The design of the machine that I worked on, a 650 Deere, is such that the 'upper' works sticks out to each side which puts the track frame back under a ledge. Talk about a royal PITA, try getting the frame to set, and stay level enough to go back on the pivot shaft when the cable on the crane hits sheet metal 6 inches before the frame hits the shaft....
 
The design was to allow better weight distribution for better traction and ground pressure. By moving the drive sprocket up higher it changes the ratios.
 
The rear idler on the high track machine only has to withstand radial loads from the track and can be really robust with having to worry about torque loads like a sprocket has. And no drop box like others have mentioned.
 
As I had it explained to me

With a flat track when the forst sprocket tooth meets the track bush it takes the load and the links behind it turn around the sprocket unloaded.

With a hitrack the chain around the back idler is turning with all the links under load and why they have to use SALT tracks. Even then seems to be stories about track life.

Interesting there seems to be a late series of D6 (maybe from Brasil?) that have gone back to flat tracks.
 

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