how much power does hst use vs gear

[1pizzahead]

Ive been told a hydro transmission steals 12-15hp on a 30-40hp tractor. I'm looking at Kubota L3800 and NH Boomer 40 tractors. Does anyone know if this is true. I've also heard about a Boomer 30 hst not being able to pull a 2 bottom plow and the guys old junker gear 12 hp could. Any help? thank you

[texasjohn]

I don't believe that there is any science behind the kind of power loss you have been told.

I have an HST and believe maybe one HP is what it takes. Yes, HST takes a small % of HP, but nobody these days using a 55 HP or under tractor puts a plow in the ground for sufficient hours in a year for that to be a factor in fuel saved. As far as traction and pulling power, a properly sized tractor/implement match will get the job done...gear/gst/HST does not matter.

HST is IMHO easily the winner when it comes to reduced operator fatigue and extreme precision operation and back/forth operations.

[crazyangel]

When I was shopping last year the data sheets I remember showed a 2-3 hp debit for HST.

EDIT: I went back and looked at some of the literature I have for a Kubota MX5100, and the published loss is 1.5 HP on a HST vs a geared transmission. YMMV.

[MHarryE]

The 2 - 3 HP debit for the HST is only for the extra power required for the HST charge pump which is always running to supply control pressure for the HST control plus make sure the piston pump always has a pressure oil supply and also oil to cool exchange in the high pressure loop so the hot loop oil can be cooled. The HST efficiency varies with pressure, pump swash plate angle, motor swash plate angle among other things. Hydros gain their efficiency in speed and direction control.

[crazyal]

People come up with information based on what they heard, not fact. The hydraulic pump for the HST drive does require HP to operate it, the numbers I've seen are anywhere from 1hp to 3hp. Then there's the issue with pressure, but the pressure is a direct result of traction and resistance to moving. The same is true for a gear tractor though. If you lift the tires off the ground then it will require no HP to turn the wheels but if you hitch it up to a large load then it will require a lot of HP.

The fact is that you are not going to run out of HP with a boomer 30 trying to pull a 2 bottom plow. You're either going to loose traction and spin your tires or you are going to pull it so slowly that the plow will not turn over the soil because you're not going fast enough. I've never tried to pull a plow but I'm guessing that pulling a 2 bottom plow with any 30hp CUT is going to be at it's limits. With the right soil it could be done. My best advise is if you are thinking about a Boomer then go to the New Holland section and ask specific questions. Tell them what you want to do. If plowing tell them the type of soil you have and the last time it was worked. Stop worrying about numbers on a piece of paper.

[jeff9366]

Does your tractor, or your proposed tractor, have an FEL?

If you will be doing a lot of forward/reverse work, as in operating an FEL, you will want an HST.

If you will primarily be pulling dirt engaging implements in straight lines over large fields, requiring minimal reverse time, a geared tractor may be appropriate.

[jeff9366]

I've also heard about a Boomer 30 hst not being able to pull a 2 bottom plow and the guys old junker gear 12 hp could.

Plow and other pulling capability is a factor of tractor weight, tractor horsepower, and tractor traction. Tractor weight is a considerable factor. A Kubota L3800 is a medium weight tractor, around 2650 pounds, and should be capable of pulling a 2-12 two bottom plow, which would normally be adjusted to plow 6" deep. Keep in mind it is easier to plow after a good rain when the soil is less resistant.

I am less certain an L3800 would pull a 2-14 two bottom plow satisfactorily.

Traction is a factor of tires, 2-WD or 4-WD and the ground you are pulling over.

Older tractors did not have much horsepower but had heavy frames and were universally outfitted with aggressively ribbed agricultural tires. The Ford 8N was 24-hp, I believe. Plowing was a high priority then, less so today. Today I believe more PT0 powered tillers, rather than plows, are used for soil preparation with compact tractors.

A high proportion of compact tractors sold today are purchased with FEL's; tractor/loaders are usually sold with industrial tires which are wider to support front end loads in the bucket and are more puncture resistant but provide less traction in the field than R-1 ag tires.

[alchemysa]

I have no idea of the HP loss of a HST but I'd suggest the stats are coming from the tractor manufacturers themselves and apply to brand new HST's in perfect condition. So I'd take those stats with a grain of salt myself.

Geared tractors don't lose power as the transmission gets 'older'. On the other hand, a tired HST can barely climb over its own shadow.

[Baby Grand]

Ive been told a hydro transmission steals 12-15hp on a 30-40hp tractor. I'm looking at Kubota L3800 and NH Boomer 40 tractors. Does anyone know if this is true. I've also heard about a Boomer 30 hst not being able to pull a 2 bottom plow and the guys old junker gear 12 hp could. Any help? thank you

Actual increased loss to hydro vs gear is probably closer to 1.2 - 1.5 hp on a 30 - 40 hp machine.
13.5 hp/hr would require a radiator capable of handling an additional 34,350 btu per hour (btu/h) heat rejection, forcing immediately noticeable design changes between the two machines. Since profit is improved by commonality through a product line, this wouldn't fly well with the business people.

[Ted Summey]

According to tractordata.com the loss is less than 2 hp at the PTO on the L3800. It varies from band to brand and model to model. In most cases the loss for HST is less than 3 hp at the PTO.