HST Power ?

[oldnslo]

A good HST at full load is around 80% efficient. Like someone else suggested compare drawbar HP vs engine HP

For example our 5600 Ford had 69 Engine HP & 50 drawbar HP and this was manual transmission

 

[Hilbilly]

You say you have it at PTO speed. Have you tried it at higher engine RPMs? My late 70s IH2500b was HST. It had a hand throttle (like most tractors) that I'd set at PTO speed. And it had a foot throttle that I could give it more gas if my engine RPMs started to drop or I needed more power to, say, climb up a hill. Of course, I could also set the hand throttle for max RPMs as well.

So, again, I'll ask if you've tried it at higher engine RPMs than PTO RPMs.?

On this tractor they are pretty much the same thing. PTO rpm's according to the owners manual is 2500 rpm (there is no marking on the tach like my previous tractor) and the max I can get with the hand throttle is about 2505 or 2510. But yes I have pushed it to the max when working it hard.

It seems to me that the power loss occurs faster on this tractor than on the gear tractor but that could be the extra weight. The power loss appears to happen quickly with only minor grade changes. But that could be my memory or just due to the different way the HST responds than the gear drive. With the gear drive you feel / see / hear the power tail off as the hill starts to get steeper. With the HST I can keep the rpms up but have to watch the HST pedal position in order to maintain the rpms and watch the speedo to see how much speed I lost. There is less of "hands on" feedback with the HST. Just part of the adjustment process I guess.

I'm pretty sure that a 20% hp increase in a gear tractor would be noticeable but not sure if it would be with HST. I know there was a noticeable difference when I went from a 35 hp gear tractor to a 47 hp gear tractor. Especially climbing up the driveway, pulling the boxblade and using the 3PTH snowblower.

 

[MossRoad]

On this tractor they are pretty much the same thing. PTO rpm's according to the owners manual is 2500 rpm (there is no marking on the tach like my previous tractor) and the max I can get with the hand throttle is about 2505 or 2510. But yes I have pushed it to the max when working it hard.

It seems to me that the power loss occurs faster on this tractor than on the gear tractor but that could be the extra weight. The power loss appears to happen quickly with only minor grade changes. But that could be my memory or just due to the different way the HST responds than the gear drive. With the gear drive you feel / see / hear the power tail off as the hill starts to get steeper. With the HST I can keep the rpms up but have to watch the HST pedal position in order to maintain the rpms and watch the speedo to see how much speed I lost. There is less of "hands on" feedback with the HST. Just part of the adjustment process I guess.

I'm pretty sure that a 20% hp increase in a gear tractor would be noticeable but not sure if it would be with HST. I know there was a noticeable difference when I went from a 35 hp gear tractor to a 47 hp gear tractor. Especially climbing up the driveway, pulling the boxblade and using the 3PTH snowblower.

Interesting. My old IH had several hundred engine RPMs available above PTO RPMs, but it was a gas engine, so maybe that's the difference.

 

[Hilbilly]

Anyone know where to find Drawbar HP info? I Googled it and came up with some hits but none give info for specific tractors. I even tried a search for Massey 1749 drawbar hp and looked at TractorData.com but no luck so far.

 

[s219]

I think 15-20% is the typical power loss in an HST.

 

[WranglerX]

Kick up RPM to max specified operational speed in owners manual... With HST the speed and power (if shift lever is in high or low range) to wheels is regulated by HST pedal pressure not engine RPM let the HST do the work, it does not drive like a gear drives transmission....

Dale

 

[Motorboatin]

On this tractor they are pretty much the same thing. PTO rpm's according to the owners manual is 2500 rpm (there is no marking on the tach like my previous tractor)

You should have a line indicating the rpm required for 540 PTO rpm

 

[rScotty]

One thing that HST and geared transmissions have in common is that more gear ranges you have, the better match you are going to get for engine power vs load.
Our powershift only has 4 ranges and it never does seem to be in quite the right range. The HST+ has six, and can match power to the job much better in spite of having less HP.
rScotty

 

[Hilbilly]

You should have a line indicating the rpm required for 540 PTO rpm


View attachment 598080

My previous tractor had the same thing. A band of green showing the PTO range but this one does not. I haven't had a need for using the PTO at speed yet so I wasn't concerned about it. I checked today and found that the PTO revs are shown on the digital display. There is a button to toggle the display between PTO speed and the Soot level. Not sure what the right engine rpms are to achieve a PTO speed of 540 but I will find out some time.

As far as the proper engine speed for the HST, the owners manual states that the HST works best at 2400 rpm and higher.

One thing that HST and geared transmissions have in common is that more gear ranges you have, the better match you are going to get for engine power vs load.
Our powershift only has 4 ranges and it never does seem to be in quite the right range. The HST+ has six, and can match power to the job much better in spite of having less HP.
rScotty

Agreed. This tractor only has 3 ranges but I could certainly see the benefit of having 6. My previous gear tractor had 12 forward and 12 reverse. 3 ranges with 4 speeds in each. Low range was a creeper range which rarely got used. Pretty much all operations were performed in high range. Mid range was used mainly for hooking up implements and for snow blowing.

 

[WranglerX]

My previous tractor had the same thing. A band of green showing the PTO range but this one does not. I haven't had a need for using the PTO at speed yet so I wasn't concerned about it. I checked today and found that the PTO revs are shown on the digital display. There is a button to toggle the display between PTO speed and the Soot level. Not sure what the right engine rpms are to achieve a PTO speed of 540 but I will find out some time.

As far as the proper engine speed for the HST, the owners manual states that the HST works best at 2400 rpm and higher.



Agreed. This tractor only has 3 ranges but I could certainly see the benefit of having 6. My previous gear tractor had 12 forward and 12 reverse. 3 ranges with 4 speeds in each. Low range was a creeper range which rarely got used. Pretty much all operations were performed in high range. Mid range was used mainly for hooking up implements and for snow blowing.

Try pushing engine rpm up to near maximum (just below red line) .... That is where the horsepower is....

Dale