RTV900 Hydostratic TIP(?)

[lloyd123]

Here’s a tip that’s posted on the Kubota Canadian website:

"Are there any 'operating methods' on Hydrostatic transmissions you can share?

With a hydrostatic transmission (HST), as your traction load increases (i.e. pulling a heavy load, operating with a loader in a dirt pile, pulling a trailer up a hill or operating in soft soil conditions), remember to maintain or decrease the HST pedal pressure as the load increases. Do not 'give it more gas'.
The hydrostatic transmission operates on the principal of hydraulics using a pump and a motor. Under heavy load conditions, pushing down on the pedal causes the pump-to-pump more oil, thereby increasing oil flow, which the motor may not be able to accept. In this case, the HST will 'stall' as the HST relief valve temporarily opens, or the engine may stall if the hi/lo range lever is in high range.
The increased oil flow from the HST pump gets dumped off as the relief valve opens. This causes the HST motor to slow down or even stop rotating. Maintaining the HST system's oil pressure within its operating range allows the hydrostat's motor to do the work more efficiently. When operating in heavy load conditions, it is recommended to gear down to 'lo' range, which also allows the HST to be more efficient."

There's nothing in the RTV900 manual about this but I assume if it works the same for all hydrostatics.

 

[Bird]

</font><font color="blue" class="small">( There's nothing in the RTV900 manual about this but I assume if it works the same for all hydrostaics. )</font>

Yep, at least all of them that I'm familiar with.

 

[lloyd123]

"Bird",

I'm wondering if the RTV900 is a different animal than a Kubota tractor when it comes to the HST. I located a couple of articles that seem to indicate that the RTV900 won't "stall" like a tractor when given too much pedal - that it will just divert power to a second motor:

From:
http://www.equipmentworld.com/apps/news/articleeqw.asp?id=42392

"The variable hydraulic transmission or “VHT” developed for the RTV900 is actually a unique, two-stage hybrid of a tractor transmission and Kubota’s load-sensing wheel-loader transmission. 'Our tractors are designed for lugging and pulling, but at a top speed of 15 mph,' Burnside says. 'In a utility vehicle you need to go 25 mph. So we gave it a second hydraulically driven motor that kicks in to give you a little extra power when the load reaches a certain point.' As a result the RTV900 can run at 25 mph and not lose its lugging capability.

And from:
http://articles.findarticles.com/p/articles/mi_m0FZX/is_3_70/ai_114698577

"In order for the HST to provide the same low-end torque as Kubota's tractors, a second variable displacement motor is driven off the main pump. Hydraulic flow is provided to this motor through a swashplate that automatically opens when the system senses the HST is beyond its limit, the company said. Hydraulic flow can also be manually directed to the second motor by selecting the low gear range. A foot-operated pedal controls gear selection by changing the gear ratio in the trans mission through a clutchless gear shift. Vehicle operation is also available in mid- and high-speed modes."

I'm a novice at understanding the HST (or VHT). Do Kubota tractors have this auxillary motor?

 

[MessickFarmEqu]

Our factory rep told us that its very simular to their tractor transmisions with the exception of that extra gate. Good articles, that was actualy one of the better explinations of this that I have heard.

 

[Bird]

George, I said "all of them that I'm familiar with" /forums/images/graemlins/wink.gif and I'm not familiar with this one. It does sound as if it might be considerably different. Thanks for the additional information.

 

[Ricochet]

</font><font color="blue" class="small">( "Bird",

I'm wondering if the RTV900 is a different animal than a Kubota tractor when it comes to the HST. I located a couple of articles that seem to indicate that the RTV900 won't "stall" like a tractor when given too much pedal - that it will just divert power to a second motor:

From:
http://www.equipmentworld.com/apps/news/articleeqw.asp?id=42392

"The variable hydraulic transmission or “VHT” developed for the RTV900 is actually a unique, two-stage hybrid of a tractor transmission and Kubota’s load-sensing wheel-loader transmission. 'Our tractors are designed for lugging and pulling, but at a top speed of 15 mph,' Burnside says. 'In a utility vehicle you need to go 25 mph. So we gave it a second hydraulically driven motor that kicks in to give you a little extra power when the load reaches a certain point.' As a result the RTV900 can run at 25 mph and not lose its lugging capability.

And from:
http://articles.findarticles.com/p/articles/mi_m0FZX/is_3_70/ai_114698577

"In order for the HST to provide the same low-end torque as Kubota's tractors, a second variable displacement motor is driven off the main pump. Hydraulic flow is provided to this motor through a swashplate that automatically opens when the system senses the HST is beyond its limit, the company said. Hydraulic flow can also be manually directed to the second motor by selecting the low gear range. A foot-operated pedal controls gear selection by changing the gear ratio in the trans mission through a clutchless gear shift. Vehicle operation is also available in mid- and high-speed modes."

I'm a novice at understanding the HST (or VHT). Do Kubota tractors have this auxillary motor?
)</font>

Kubota HST tractors do not have 2 motors...they are 1 pump 1 motor. The RTV900 VHT is unique and has 1 pump 2 motors like the well written article(s) points out.