hydrostat vs gear hp loss

[dieselsmoke1]

going slower isn't going to compensate for the difference in horsepower

I can't quite follow you Keith.

Take 2 identical 40 hp tractors, geared if you like, and hook an identical 6' disk to both. Turn the fuel down to 35 hp on one tractor. Will they both pull the disk? I'm betting yes. The 40 may pull it in a faster gear than the 35, but they will both pull it. I'm thinking the same principle applies to a hydro with a 10%, 20% whatever drivetrain loss.

 

[Soundguy]

If a hydro has more than enough power to do the task you want to do with it then why do you need a gear with more power?

You may not need it... but you may be able to get it for the same price. The hydro tranny adds a small premium to the tractor price, and/or there may be a deluxe model line and an economy model line. especially in brands that have many different tractors of 'overlapping' hp regions.

Could be very easy to do away with a few bells and whistles and deluxe options.. and get more hp in a gear unit.. vs a more chromed hst model.. etc.

Either choice is valid.. depending on the buyer.

Soundguy

 

[Soundguy]

That's deffinately not an apples to apples comparison. For a valid comparison.. I would think you would need identical power units.. and have the difference int he drivetrain.. not 'detuning' one engine and then saying one does more work... etc.. ( That's like pointing at a hamburger and saying.. 'that's food'. .. etc.. )

In any case.. hp has a time variable inthe calc... Saying one unit pulls faster than another.. given same engine, and different drivetrrains. then.. I'd have to say the faster unit has more drawbar hp... which.. I think is what we all are agreeing on.. right?

Soundguy

I can't quite follow you Keith.

Take 2 identical 40 hp tractors, geared if you like, and hook an identical 6' disk to both. Turn the fuel down to 35 hp on one tractor. Will they both pull the disk? I'm betting yes. The 40 may pull it in a faster gear than the 35, but they will both pull it. I'm thinking the same principle applies to a hydro with a 10%, 20% whatever drivetrain loss.

 

[dieselsmoke1]

The example was to illustrate a point, albeit was a little far fetched.

Yes, I agree. Enough on this one. Thanks for the discussion, guys.

 

[yellowandbeige]

I'm sorry I have to add my two cents,

I don't think It's about being able to do the same work ( like moving a load ) faster or slower with gears vs hydro.
If you have two identicle tractors except tranny and are moving loads near or at thier limit the gear tractor will do the work abeit barely and the hydro's pop off setting will keep the tractor from moving the load. Thats the frustration with hydros. With a gear you either spin tires move the load or stall the engine.
With a hydro you might be working at the upper limits of traction and transmition and reach the point where the tranny won't move the load , won't spin tires and won't stall engine. Ask me how I know.
Y&B

 

[fish_wisperer]

I have a Mahindra 2810HST and if I remember correctly there was about 1.5hp lost to the pto vs gear. As far as drawbar hp, mines heavier than some others in it's hp class and with loaded rears it'll still spin the tires in 4wd if it meets an immovable object. What more could it do? I think soundguy might be onto something regarding relief settings, we've read about it before on TBN.

i think that sais it all, with loaded tires spinning anymore power is a waste.

 

[Soundguy]

Now that says it best.

Soundguy

I'm sorry I have to add my two cents,

I don't think It's about being able to do the same work ( like moving a load ) faster or slower with gears vs hydro.
If you have two identicle tractors except tranny and are moving loads near or at thier limit the gear tractor will do the work abeit barely and the hydro's pop off setting will keep the tractor from moving the load. Thats the frustration with hydros. With a gear you either spin tires move the load or stall the engine.
With a hydro you might be working at the upper limits of traction and transmition and reach the point where the tranny won't move the load , won't spin tires and won't stall engine. Ask me how I know.
Y&B

 

[art]

I've not seen a hydro that on a dead pull won't start a load that a gear drive will! That is when in the right range for the load! I've pulled 15,000lb tractors whith hydro shaft drive cadets like 129's 12 horse and I was able to spin the tires as well as not spin them. If a hydro won't spin in low range then it is to heavy and you will be burning a lot of extra fuel.

 

[Soundguy]

We have seen posts here, in the past few years where a tractor has crawled into an area that it would not crawl out of.. no tires spinning... I'm petty sure it was the relief valve opening.

Soundguy

 

[NewToy]

OK, I gotcha now but there's still not a 20% difference. Below is a link to some interesting reading. Although it doesn't go into HP loses, it's interesting. Look on page 4

http://www.eurageng.net/files/nl.pdf

I have a hard time believing that a hydro unit will give you a 74% efficiency increase in tilling applications and almost 50% mowing. Must be a magic tractor or the person operating the gear unit was completely inept.

John