435 Build

[marrt]

You guys may recall my thread, a few months ago, about the death of my Subaru. The root cause was gas in the oil. Seems to be happening a lot lately. I didn't bother tracking down the exact source of the leak. I suspect it was the carburetor but I don't know for sure. By the way, I still have the old engine if somebody needs a part.

After a lot of hemming and hawing, I finally ordered the 35 hp Subaru "Generac" engine. I decided to go with this approach because I like to "mod" stuff especially Power-Tracs. I ordered larger will motors too. Probably don't need them with the larger engine but it should make the VD pump's life a little easier.

I'm ready to put everything back together but still have some concerns about cooling. And, given KentT's experience with the plastic fuel tank during a fire, I'm thinking about fabricating a steel tank. Also, this would be a good opportunity to relocate the hydraulic filter out of the tub and up near the tank. This could probably be accomplished by fabricating a smaller fuel tank so I have room.

I'll try to take a few pictures along the way.

 

[KentT]

Sounds like a fun project! What size wheel motors are you putting on it?

 

[joshlee]

Since I'm sort of new with understanding hydraulics, I'm just curious about the bigger wheel motors on the Pt 425. So I take it, the bigger wheel motors don't cause engine power loss, or work the tram pump too hard?

 

[Gravy]

You guys may recall my thread, a few months ago, about the death of my Subaru. The root cause was gas in the oil. Seems to be happening a lot lately. I didn't bother tracking down the exact source of the leak. I suspect it was the carburetor but I don't know for sure. By the way, I still have the old engine if somebody needs a part.

After a lot of hemming and hawing, I finally ordered the 35 hp Subaru "Generac" engine. I decided to go with this approach because I like to "mod" stuff?specially Power-Tracs. I ordered larger will motors too. Probably don稚 need them with the larger engine but it should make the VD pump痴 life a little easier.

I知 ready to put everything back together but still have some concerns about cooling. And, given KentT痴 experience with the plastic fuel tank during a fire, I'm thinking about fabricating a steel tank. Also, this would be a good opportunity to relocate the hydraulic filter out of the tub and up near the tank. This could probably be accomplished by fabricating a smaller fuel tank so I have room.

I'll try to take a few pictures along the way.

My 435 conversion is still working so well that I sorta forgot that I promised details. Have fun!

 

[marrt]

Kent, I'll have to look. I remember you made recommendations. I recall taking those recommendations into account. More tomorrow.

 

[marrt]

Joshless,

It's just like gearing in a normal vehicle. Larger wheel motors are like a lower gear. The pump has to run "longer" to fill the displacement on each revolution..which results in more torque. The tractor will run slower...but will likely spin the wheels before it runs out of mojo and stalls the pump/engine.

Tom

 

[MossRoad]

Since I'm sort of new with understanding hydraulics, I'm just curious about the bigger wheel motors on the Pt 425. So I take it, the bigger wheel motors don't cause engine power loss, or work the tram pump too hard?

As I understand it, the engine will still turn at 3600 RPM (max throttle) and the tram pump will still turn at the same RPM at full throttle and the tram pump will still put out the same gallons per minute at full throttle. The only thing different is the displacement inside the wheel motor is larger, so it takes more fluid to turn it 1 RPM than a smaller displacement pump would. So the larger displacement wheel motors won't spin as fast as the originals, but they will apply more torque.

My guess is the larger displacement means bigger vanes, gears, or pistons inside the motor. Bigger vanes, gears, or pistons would be the equivalent to lengthening a lever. Longer levers apply more leverage but take longer to go full stroke. That's why higher displacement makes more torque, but turns slower.

Of course, I don't know how that works at all, I'm just guessing. Someone will correct me if I'm wrong, and I'll get a free education.

 

[KentT]

You're understanding is correct. And with the tram (hydrostatic drive) pump, using a larger engine does not increase the maximum volume of the output, since both engines spin at 3600 RPM, but it increases the amount of pressure that can be produced by the pump (at any tram pedal setting), also increasing torque...

 

[MossRoad]

Gotcha. Thanks. :thumbsup:

 

[joshlee]

I understand now, thanks everyone.