Buying Advice Potential PT Buyer Questions

[SPYDERLK]

Well, all the pumps are always connected and all are pumping very cold oil. But you are correct in that when it is first starting, the pumps are not pumping at full pressure. How many engine cranks it takes for them to be at pressure and start bypassing, i do not know. But basically, i meant there is no clutch so the engine is not just free spinning. But from the way the engine runs after it even starts firing, i would say the load is significant.

Ken

You are seeing the viscous drag of parts moving in cold oil. The pumps are variable displacement I believe. If so they arent pumping anything unless you are trying to move. Even if they were fixed displacement the system pressure is never high unless the pumped fluid is required to do something. Overcoming viscous drag in a pipe flow is something - just not much at cranking or idle speed. Merely pumping it thru an open pipe from the sump back to the sump doesnt take much.
larry

 

[duane]

Your correct about the variable displacement pump, but the charge pump, PTO pump and steering/lift pump are gear style and moving oil during starting. Significant load when cold as any PT owner would attest to.

 

[BobRip]

On most systems the engines are totally disconnected from the mechanical load when starting. Here there is significant load.

On the charge pump, it pumps fluid at a 70psi (I think) pressure. Anybody thought of an easy way to decouple the pumps during starting. It looks pretty difficult and would require space the PT tub does not have.

 

[J_J]

Bob,

I believe the charge pump pressure is about 350-450 psi.

 

[SPYDERLK]

Your correct about the variable displacement pump, but the charge pump, PTO pump and steering/lift pump are gear style and moving oil during starting. Significant load when cold as any PT owner would attest to.

Odd that Kub BX HSTs dont show this to much extent at all. Try a higher Viscosity Index Hyd oil like SUDT.
larry

 

[MossRoad]

On most systems the engines are totally disconnected from the mechanical load when starting. Here there is significant load.

On the charge pump, it pumps fluid at a 70psi (I think) pressure. Anybody thought of an easy way to decouple the pumps during starting. It looks pretty difficult and would require space the PT tub does not have.

That would require two clutches on my PT425, as there are pumps in both sides of the engine. The newer PT400s have all the pumps on one end, so only one clutch would be needed.

 

[J_J]

I haven't seen the magnetic particle clutches used for much. Renault used a magnetic particle clutch for their clutch years ago. These clutches below, will handle up to 300 ft lbs. The torque is varied by input current.

Placid Industries - Magnetic Particle Clutches, Magnetic Particle Brakes & Hysteresis Brakes - Home page

 

[American Bulldog]

I haven't seen the magnetic particle clutches used for much. Renault used a magnetic particle clutch for their clutch years ago. These clutches below, will handle up to 300 ft lbs. The torque is varied by input current.

Placid Industries - Magnetic Particle Clutches, Magnetic Particle Brakes & Hysteresis Brakes - Home page

In electric industrial applications magnetic clutches were used to get variable speed, back in the 70's to mid 80's, in certain applications. They were called eddy current clutches. I worked on a lot of them back in the day.

 

[BobRip]

Bob,

I believe the charge pump pressure is about 350-450 psi.

Thanks for the correcton J_J.