HST vs. gear drive for various types of work.

[mcmxi]

A lot of people feel that gear drives don't have a slow enough gear.

I think that with some of the older tractors that was-is an issue maybe?

I had the local dealer add the Creep range option on my M6060 soon after I bought it.

C1 > 0.21 mph
C2 > 0.30 mph
C3 > 0.41 mph
C4 > 0.66 mph

Those ground speeds are at the "rated engine rpm".

 

[mcmxi]

Lots of good info in this thread.

Only a couple things I would add / did not see mentioned:

1. IMO, I’ve felt a loss of oomph from time to time with an HST going up a hill (especially on the B but to some extent even on the Mx), especially if pulling or running the PTO. My bellyrub estimate is 15-20ish% loss…I don’t have a way to prove it but there is no question it luggs a bit….its not a big deal but it can be felt.

2. Also for a similar sized engines I think the geared tractor delivers more PTO power relative to HST…seems the specs even suggest/ support that. So I think geared would be more efficient for most pulling or PTO tasks.

Exception might be relative to size and scope of work. In a small garden though I think a HST would certainly be ideal. Not in all cases but in general. If you have something that you like to precisely control speed, maybe HST would be an exception such as tiller or something like that.

All that being said, I love the speed control lock on the MX. If it did not have that speed lock, the spousal unit would have already bought me a larger geared machine . With the speed control lock, for my scale of use / utility chores, in and out of the woods, in and out of garden, around fences and buildings, there is not a demerit with the HST.

Great points for sure.

I like the MX6000 with HST and am very lucky to have a choice when it comes to doing various tasks at my place or offsite somewhere. I've said this before, but if I had to sell a tractor it'd be the MX first, but I realize that I'd really feel the loss when doing certain jobs. There's no doubt that an HST is easier to live with day in and day out.

 

[rc51stierhoff]

Great points for sure.

I like the MX6000 with HST and am very lucky to have a choice when it comes to doing various tasks at my place or offsite somewhere. I've said this before, but if I had to sell a tractor it'd be the MX first, but I realize that I'd really feel the loss when doing certain jobs. There's no doubt that an HST is easier to live with day in and day out.

I think a better question would be if you were buying another M (same size or your choice of displacement) and HST was a transmission option and no cost difference, what would you buy? geared or HST?

 

[TheOldHokie]

Thanks - - I'm not savvy about CVT systems. Just have heard that some larger tractors have it.

I understand some passenger cars are CVT now also, but that's a tangent from the thread.

CVT is just another way to get the same "infinite" shiftless speed control that you get with an HST. It is mechanical rather than hydraulic and does not suffer from the power loss inefficiencies of an HST transmission. CVT has become the top line technology for large agricultural machines in the same way HST is in the compact tractor world. ALL of the big names offer it

DEERE
CASE
FERGUSON
AGCO
FENDT
CLAAS
CHALLENGER
VERSATILE

Dan

 

[N3BP]

CVT is just another way to get the same "infinite" shiftless speed control that you get with an HST. It is mechanical rather than hydraulic and does not suffer from the power loss inefficiencies of an HST transmission. CVT has become the top line technology for large agricultural machines in the same way HST is in the compact tractor world. ALL of the big names offer it

DEERE
CASE
FERGUSON
AGCO
FENDT
CLAAS
CHALLENGER
VERSATILE

Dan

Sounds like Nissan should visit those manufactures

 

[TheOldHokie]

Sounds like Nissan should visit those manufactures

My understanding of these systems is sketchy but I think agricultural CVTs operate differently than automobile CVTs.

My impression is agricultural CVTs are hydrostatic/mechanical hybrids while autos are purely mechanical.

Dan

 

[TheOldHokie]

Sounds like Nissan should visit those manufactures

Here's a pretty good explanation of the Fendt Vario CVT.

There are other designs but this one is the Grandaddy of them all. The video is 8+ minutes long and narrated by a guy with a heavy accent. So here is my Readers Digest summary to help you understand the narration and accompanying animation.

FENT VARIO TRANSMISSION

1. The engine is directly coupled to a planetary gear set that acts as a power divider and has two outputs
2. One output powers a conventional HST transmission that in turn powers the wheels via a set of range gears
3. The other output mechanically couples the engine to the wheels via those same range gears
4. In neutral the planetary is sending all engine power to the variable displacement HST pump which is positioned for zero oil flow. The direct engine drive is disengaged.
5. When the operator calls for forward movement the HST pump is activated which sends hydraulic flow to the HST motor and sets the tractor in motion. In this mode acceleration is regulated by a combination of HST flow and engine RPM just like your Kubota HST.
6. Once the desired ground speed is reached the HST motor returns to neutral which causes the planetary to redirect all engine power to the range gears and the drive becomes purely mechanical. In this mode the HST drive is disengaged and ground speed and tractive power is controlled by adjusting engine RPM

Pretty slick....

Dan

 

[mcmxi]

I think a better question would be if you were buying another M (same size or your choice of displacement) and HST was a transmission option and no cost difference, what would you buy? geared or HST?

That's a great question. So would I rather have and MX and M with both having an HST or would I stick with the current configuration if an HST were an option in an M6060/M7060. I would probably lean towards having HST in both since it is an easier transmission for the vast majority of the tasks that I do.

I don't really use the M6060 in the winter moths since the MX is such a good tractor with the snow plow and blower, in large part because of the HST. At the moment, the M is mostly used for pulling cutters around larger, hilly areas or pulling the box blade, disc harrow or land leveler since it's way better at doing those tasks compared to the MX.

 

[Smokeydog]

Wife is competent operator of the HST B26. Handy when I need help on the M59 for FEL basket work or other jobs. HST sure helps other operators less familiar with tractors. My Dad had a tractor before I was born but he sure scared me and him too sometimes with geared tractors.

 

[SDT]

My understanding of these systems is sketchy but I think agricultural CVTs operate differently than automobile CVTs.

My impression is agricultural CVTs are hydrostatic/mechanical hybrids while autos are purely mechanical.

Dan

Indeed, they do. No metal belts, tapered pulleys, cones, balls, etc.

Some (most?) such CVTs used in high HP AG tractors and other applications, use harmonic drives driven by small, variable speed hydraulic motors to provide variable speed.

Thanks - - I'm not savvy about CVT systems. Just have heard that some larger tractors have it.

I understand some passenger cars are CVT now also, but that's a tangent from the thread.

Yes, High HP AG CVTs are completely different from the CVTs used in IC automobiles. No metal belts, tapered pulleys, cones, balls, etc.

Most (All?) CVTs used in high HP AG tractors and other applications, use harmonic drives driven by small, variable speed/reversable hydraulic motors to provide variable speed.

 

[TheOldHokie]

Indeed, they do. No metal belts, tapered pulleys, cones, balls, etc.

Some (most?) such CVTs used in high HP AG tractors and other applications, use harmonic drives driven by small, variable speed hydraulic motors to provide variable speed.

Yes, High HP AG CVTs are completely different from the CVTs used in IC automobiles. No metal belts, tapered pulleys, cones, balls, etc.

Most (All?) CVTs used in high HP AG tractors and other applications, use harmonic drives driven by small, variable speed/reversable hydraulic motors to provide variable speed.

As I said I am not sn expert but none of the agricultural CVTs I have explored use harmonic drives. They are all designed around the Fendt developed hydrostatic/mechanical split power drive principle I described above.

Fendt (Agco) transmissions are stepless. Two ranges and zero to full speed with no gear shifting in the selected range.

Others (e.g ZF) use that as a first stage which feeds a conventional powershift gearbox and shuttle reverser. The result is power transmission that is not as smooth and continuous as the Vario style. Here is a video showing the ZF design

I would be interested in seeing an example of the type you are describing.

Dan