Hydrostats in larger tractors

ironpen · Jul 30, 2012

Is there any reason that tractors in the TN or 4000 series don't (or can't) have hydrostat transmissions. I would love to have one on my TN75S. I am sure that there must be a reason, but I can't think of one. Any comments or thoughts would be appreciated.

jinman · Jul 30, 2012

I think the reason is two-fold:

1. An HST that can deliver the kind of power a TN75 or larger tractor has would be very big and expensive. It would probably add several thousand dollars to the price of the machine.

2. Since the TNs and 4000 series are primarily used for draft loads and earth engagement, the HST is not the most efficient type of transmission for those jobs. The shuttle transmissions with a lot of gears seem to be the most efficient way of getting power to the ground in all situations.

I agree that a large HP tractor with HST seems very attractive for doing loader work. However, a construction grade loader backhoe has a torque converter and shuttle transmission that make them very efficient for dirt handling and moving. A large HP tractor with HST might compete with the TLBs, and manufacturers don't want to build and sell products that compete with each other. I think HST transmissions on tractors in the 60 hp range are the largest we'll see in the near future, but certainly, larger tractors are capable of having HST drives. There are a number of bulldozers that now have HST drives.

WilliamBos · Jul 30, 2012

They are a totally different breed called CVT/IVT. You need to try a Powershuttle tractor for loader work. You wont ever want an HST ever again.

And with more gears to choise from in many powershift transmissions, the HST will be at a huge disadvantage.

boggen · Jul 30, 2012

shuttle shift with power reverser. perhaps the 555c ford TLB commercial unit i have. has spoiled me. i wish it had more gear options though. but for 1980's used tractor it does it job nicely.

HST peddal may be nice. but the 555c ford TLB, has a button on the gear shifters, to dis-engage clutch while shifting. so no need for foot clutch. it also has button on the forward/backward lever to dis-engage clutch. while switching back and forth. and then on the FEL joystick there is another button to disengage clutch. so i can put full power to the FEL.

ya i gotta reach over to shift gears, but generally like a lower gear going into a pile of dirt or rock. and then if i need to drive to another area with a full bucket. it is fairly easy to do so, since i am driving, vs trying to operate FEL or backhoe or something else.

not sure if i would even want a HST pedal for FEL work. i get into to many situations were i may hammer into a pile of dirt or rock and with HST pedal and foot would slam the pedal down in different directions, or foot would be bouncing all over the place as i went over little bumps and holes, causing tractor to speed up, speed down, speed up, speed down.

ironpen · Aug 1, 2012

I hear what you are saying....but 90% of my usage is for mowing for my TN75S. I sure would like to be able to control speed easier as I turn corners or hit rough spots. I use it for finishing mowing with a 100 inch deck and for a 10 foot bush hog. I have the Galaxy turf tires, so it sits low and looks funny to most, but I really have enjoyed it and that a/c is priceless on days like today. I guess I can always hope!! I was going to buy a loader for it, but my dealer had a 3010 with only a hundred hours on it with a Woods loader for almost the same money as a new FEL, so I bought it instead. As we all know, a man can't have too many guns or tractors, right? The 3010 doesn't have shuttle, etc. but I have really had no complaints having to shift forward and reverse. I do find that I use it a lot more than I ever thought I would, especially since I got some chain on forks for $130 out of Oklahoma that are absolutely fantastic.

jinman · Aug 2, 2012

Maybe one of these days they will offer a "dual-power" tractor model that will be HST for applications like yours and also have a feed-thru mode for the HST into a gear transmission similar to the way the PTO shaft currently works. That would sure raise the price of the tractor, but some people with dual applications would find that attractive enough to pay the difference. I just don't know how many they could sell, and the marketing would be the rub rather than the available engineering to build a machine like that.

JC-jetro · Aug 2, 2012

Jim,

On your HST TC45 will you kill the pto if you clutch?

JC,

jinman · Aug 2, 2012

JC-jetro said:
On your HST TC45 will you kill the pto if you clutch?

:laughing::laughing::laughing:

Good one! As soon as I find the clutch, I'll give it a try.

The HST models of TC35/40/45 have NO CLUTCH. The flywheel is directly coupled into the transmission with only a dampener in between to reduce shock. That's why we can have brakes on the left and HST pedals on the right where God intended them to be.

Edit: In addition, the gear models have the PTO drive on a concentric shaft inside the main shaft which gets clutched. Pressing the clutch has no effect on PTO operation. It is completely independent as I think your new Kubota will also be.

JC-jetro · Aug 2, 2012

jinman said:
:laughing::laughing::laughing:

Good one! As soon as I find the clutch, I'll give it a try. The HST models of TC35/40/45 have NO CLUTCH. The flywheel is directly coupled into the transmission with only a dampener in between to reduce shock. That's why we can have brakes on the left and HST pedals on the right where God intended them to be.

Cool

Indeed very interesting Jim:thumbsup:. I was going thru WSM (Work Shop Manual) for the Kubota I bought. You know mine is gear. Both HST and gear models have a single dry main clutch and they both are advertised as having Live independent PTO. Once I examined the pics in the manual it clearly shows the HST to have one solid input shaft and gear like it should with two splined shaft (Inner being pto and the outer to transmission). I could clutch with the gear and pto keeps spinning but can't see how HST with one input shaft can do. That was one test I did not do. Funny thing is I called my Dealer's service mgr and he said.. hmmmm, Really? I ought to check in to it, lol.

JC,

PS. time to go to NH website and check your transmission diagram... as they say " curiosity killed the cat"

Yankee Clipper · Aug 7, 2012

Harvester built many models and configurations of hydros in the 60s. 70s and 80s. The largest was a 1066 hydro at 125 hp - if I remember right. They were excellent but people used them in high draft applications which they will do for a while and also skimped on maintenence, which is bad news for hydros of any size. Case kept the H186 / H3288 for a while but the Magnum ended all that in '89 and the rest is history.

A hydro will work circles around a gear drive if the primary mission is PTO work as you can match the ground speed to the crop conditions / throughput.

For what it is worth, given reasonable care and correctly applied, I have seen hydros run thousands of hours without a failure.

YC