Hi, Low Med ranges when to use what?

[Hoosier_Daddy]

I mow a steep hill in Mid w/4wD without a problem. I use low for serious loader work. I use high to get to the beer or if Bathroom #2 comes into mind.

Cruise Control may not be a needed Item but I wished I had it with the old boomerang on the BX2200 when dragging a blade or box around.

Now I have it on the B26 and I expect I will use it one of these days and be happy. Of course if I am running down the road to the Local Legion Post then Cruise seems like a nice thing to have.

Tom...

 

[lawn_king]

When i owned a B3030 i used mid range for the most part, high range was useless for anything other than transport.

 

[slan]

I had to play with mine for the first while until I got used to the hydro transmission. I agree with most that high range is only for travel in 2wd. There seems to be a lot of drive line whine if in 4wd and would probably add more wear.

My thoughts on the loading of a hydro trans is not to load the pump and motor up by using a higher range than needed. It is like lugging an engine up a hill rather than downshifting. It just puts more strain on the hydro motor at the lower RPM's. Maybe I am babying it a bit too much because I am still at that "new tractor phase".

As for the cruise control, I love it for mowing the fields and chain harrowing. With the new hydro it automatically reduces speed if it gets into the tough stuff or going up a hill. You don't have to vary the speed with the hydro pedal. Just make sure the response dial is set to quick response and you are away.

This is from a relatively new owner with just over 100 hours.

 

[AndyinIowa]

Here's an interesting formula that will get people to lower their transmission ranges:

If Medium range doubles your tractor speed, it also doubles the pressure in the transmission motor circuit to operate at the same tractor speed. For instance, if your tractor requires 1200psi to mow at 3mph in low, it will take about 2400psi to mow at 3mph in medium.

Now for the interesting part. If you double the average pressure your HST sees in the propel circuit, you reduce the life of the rotating kits by 8-fold!

A pump that has a 10,000 hour approximate life at 3000psi, will only last about 3000 hours at 3500psi. The key is that small changes in duty cycle greatly affect transmission life.

SO in summary, if low range gets the job done, leave it in low. If medium gets the job done, leave it in medium. Always keep the tractor in the lowest range to adequately do the job. Transmission whine = high pressure = lower life.

IowaAndy

 

[slan]

Thanks Andy, that was what I was trying to say but you explained it much better.

It drives me nuts watchng someone mow in too high of a range with minimal pedal and low engine rpm.
Should make mental note, "dont buy that one if it comes up used"

IMHO

 

[BrierPatch]

Here's an interesting formula that will get people to lower their transmission ranges:

If Medium range doubles your tractor speed, it also doubles the pressure in the transmission motor circuit to operate at the same tractor speed. For instance, if your tractor requires 1200psi to mow at 3mph in low, it will take about 2400psi to mow at 3mph in medium.

Now for the interesting part. If you double the average pressure your HST sees in the propel circuit, you reduce the life of the rotating kits by 8-fold!

A pump that has a 10,000 hour approximate life at 3000psi, will only last about 3000 hours at 3500psi. The key is that small changes in duty cycle greatly affect transmission life.

SO in summary, if low range gets the job done, leave it in low. If medium gets the job done, leave it in medium. Always keep the tractor in the lowest range to adequately do the job. Transmission whine = high pressure = lower life.

I see most of your logic. I can't quite wrap my mind around it entirely. Could you help me understand how the variable displacement part of the pump works into your equations. Flow, Heat, stroke etc. I am not used to looking a hydrostat as a pressure pump. Are these equations linear or are you keeping it simple? Most pumps have an operation curve and are designed to operate in a particular range. If I understand your equations correctly then I should always run my tractor in the lowest gear so the HST will have the lowest pressure and thus last the longest?

 

[AndyinIowa]

I see most of your logic. I can't quite wrap my mind around it entirely. Could you help me understand how the variable displacement part of the pump works into your equations. Flow, Heat, stroke etc. I am not used to looking a hydrostat as a pressure pump. Are these equations linear or are you keeping it simple? Most pumps have an operation curve and are designed to operate in a particular range. If I understand your equations correctly then I should always run my tractor in the lowest gear so the HST will have the lowest pressure and thus last the longest?

I'm talking only about kit life, which relies on calculations of the pressure fatigue equations for the cylinder block, pistons, and slippers.

The equations are linear for speed of the pump. If you transmit the same torque through a pump, doubling the speed that the pump is spinning will reduce the fatigue life of the kit by half.

For pressure, the equation is to the 8th power. Some manufacturers use other exponents (I've seen 5th power on several presentations). Regardless, the pressure component of a life calculation is considerably more important than speed.

You are correct that heat, contamination, and stroke of the pump also affect life, but in a different set of calculations. I'm only talking about fatigue life of the pump parts themselves.

An interesting final comment: Virtually all pump failures I've seen in the past 5 years are due to contamination or viscosity related issues. If you keep cool clean oil in a piston pump, it will run a long long LONG time. As soon as you throw dirt in the oil, all bets are off!

IowaAndy