HST vs. Shuttle Shift?

[RoyJackson]

I don't think that's correct, as I stated in post #31 above. HST's seem to "rob", or utilize, about 1.5 HP more of the engine's HP than non-HST machines.

The exact same tractor as my HST in non-HST format has 1.5 more PTO HP than mine, & I've encountered that same 1.5 HP difference many times.

Yep, if the specs show both engine and PTO HP ratings, and a tractor is available with both gear and HST transmissions, the HST is alway a couple PTO HP lower. I'd estimate around 5-8 percent, n the average.

 

[US American]

I should have said it doesn't degrade pto power greatly. The difference in drawbar power, on the other hand, is very noticeable. My misstatement.

 

[LMan1967]

drawbar HP?

 

[RoyJackson]

drawbar HP?

Yep...pretty common measure of pulling power. I've never seen this metric used with CUTs, but larger tractors are rated by drawbar HP.

 

[LMan1967]

Yep...pretty common measure of pulling power. I've never seen this metric used with CUTs, but larger tractors are rated by drawbar HP.

ack...theres just too much to learn... :confused2::laughing:

 

[jinman]

I think the reason the HST tractors always show a bit less HP at the PTO than non-HST tractors is that the HST charge pump always runs if the engine is running. Keeping the charge pump running and the HST pump flowing enough oil to lube and cool the transmission will take a small amount of HP even if the PTO power train goes straight through the HST transmission and the tractor is not moving. Of course the PTO HP numbers are maximum numbers anyhow, with the tractor not moving. When you are driving, the transmission and geartrain supplying power robs engine HP, and the PTO available HP drops. Even without a heavy load, you'll rob power from the PTO.

 

[jenkinsph]

ack...theres just too much to learn... :confused2::laughing:

Simple thing to do is try out an hst and you will find out how easy it is to use.