HST tranny details?

   / HST tranny details? #1  

davesisk

Platinum Member
Joined
Apr 18, 2002
Messages
862
Location
Raleigh, NC USA
Tractor
Massey-Ferguson MF 1220
Hi folks:

I'm a current Power-trac owner (<A target="_blank" HREF=http://www.ipass.net/~davesisk/tractor.htm)>http://www.ipass.net/~davesisk/tractor.htm)</A>, and it's completely hydraulic drive, HST pump and hydraulic wheel motors at each wheel, no gear lever, etc. One disadvantage is that you only half one speed range, although it's certainly nice to not have to shift between forward and reverse (you just press the right or left pedal).

I'm curious about how the HST tranny's work on a more traditional CUT. On the NH's, is it setup with a hydraulic pump that drives a single hydraulic motor which in turn drives a geared transmission/differential/etc? Do you have the right pedal = forward/left pedal = reverse deal (or similar) but also a clutch and gear range shifter? Any details appreciated...

Thx,
Dave
 
   / HST tranny details? #2  
My TC29D has a clutch on the left that engages/disengages the engine from the transmission. Somewhere in the transmission is a pump and motor that sends power to the wheels, there is not a separate motor at each wheel. It has a range lever with 3 ranges. The 3 ranges are definitely needed. I use mid range for mowing and most general work. I use low range for plowing, digging with rear scoop, and other heavy work. I rarely use high range, but have used it to travel on the road a few times. On the right is a single HST control pedal, push down on the front to go forward, push down on the back to go backward. I think the larger Boomers have the 2 pedal HST control, but I'm not sure.
 
   / HST tranny details? #3  
Dave, the NH Boomers use a combination of gears and hydrostatic speed control. The gears are the “range” selection of High-Med-Low. Not all Boomers have three ranges. The larger, Class III, Boomers have only two ranges. Like all hydrostatic transmissions, the continuously variable speed is provided by changing the angle of the swash-plate in the hydraulic pump to provide more or less flow to the hydraulic motor. The Class III Boomers have another range control (effectively making a total of four ranges) that is electrically controlled. Using a solenoid and low hydraulic pressure, the motor’s swash-plate is changed between 15º (low-turtle) and 9º (high-rabbit). This feature is built into the loader joystick and on the fender console also. Two places ensures that tractors with or without a loader have the turtle-rabbit switch. The Class III Boomers have no clutch at all. The brake pedals are on the left of the operator’s console and the hydro pedals are on the right. The inside (left) pedal is forward and the right is reverse. That’s the brief description of the NH CUT’s hydro tranny. I’m sure some of the other fellows will add more details for their specific tractor model. Hope this helps.
 

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