Up until now it has been simpler and cheaper to just upsize the engine slightly to make up for any power losses related to an HST drivetrain. Pretty easy with tractors under 40 hp or so. But the demand for larger, heavier CUTs has been growing, and larger size brings other problems involving heat, durability, fuel efficiency and cost for making HST tractors. It looks like 60 hp is about where the manufacturers draw the line right now. We're seeing some innovations such as CVT and Yanmar's new transmission and someone will probably bring out a 70 hp HST model at some point.
Bigger hydrostat tractor?
- Thread starter Tobster
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jenkinsph
Super Star Member
I think it is more about sales and demand than technology. If the manufacturers think they can sell a larger hydrostatic tractor they will offer it and build it. I think it really is that simple and the smaller hydrostatic tractors have sold well and have gained acceptance. Doubt it will be long before the hydro's are offered in the utility size tractors.
MHarryE
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Higher HP hydros, International Harvester built the 1066 with 114 PTO HP. They later changed it to the IH 100 to avoid confusion with the gear drive 1066. The Hydro version was a great one around the farmyard - loader work, odds and ends, planting, row crop weed control cultivating. Problem in the field was power efficiency when doing tillage work - the reason IH split the name. But there you have your high HP full hydro with variable pump and motor. Loved by the owners who bought it for the purpose intended. Hated by those who bought it as a 1066 for tillage.
The Fendt is a hybrid so you really can't call it a hydro. The hydro motor spins a ring gear forward or reverse varying the speed infinitely, but most of the power goes through the main planetary. At Cat we introduced something similar with our differential steer dozers, I believe starting with the D8. Instead of declutching one side, the system reversed rotation of the final ring gear which slowed the track on that side. Highly efficient compared to older systems.
But for full hydro, I believe the IH100 or IH1066 Hydro remain the king of the hill as far as power. If you pull up the Nebraska test you will find the hydro version had a maximum 9576 pounds pull while direct drive had 13,000 pounds. They used about the same fuel at max pull indicating the inefficiency of the hydro at high drawbar loads. However around the farmyard where the hydro shines the amount of work done per hour made it a much more efficient tractor.
The Fendt is a hybrid so you really can't call it a hydro. The hydro motor spins a ring gear forward or reverse varying the speed infinitely, but most of the power goes through the main planetary. At Cat we introduced something similar with our differential steer dozers, I believe starting with the D8. Instead of declutching one side, the system reversed rotation of the final ring gear which slowed the track on that side. Highly efficient compared to older systems.
But for full hydro, I believe the IH100 or IH1066 Hydro remain the king of the hill as far as power. If you pull up the Nebraska test you will find the hydro version had a maximum 9576 pounds pull while direct drive had 13,000 pounds. They used about the same fuel at max pull indicating the inefficiency of the hydro at high drawbar loads. However around the farmyard where the hydro shines the amount of work done per hour made it a much more efficient tractor.