Engine swap?

[MossRoad]

You could put an electric motor at each wheel and drive the steering and lift with hydraulics like our electric fork lift does... except it only has one electric motor on a differential that drives the two front tires...

I think you are re-inventing the wheel if you try to convert a PT to electric. Too much to change for little benefit.... unless you just like to make cool stuff!

[Gravy]

Gravy, you might want to mention some of your technical skills and what you are willing to change. Can you weld. Would you be willing to cut the tub and lenghten the engine compartment? Sounds like no, since you need it turned around quickly.
Some other issues - Will the pumps and wheel motors take the additional speed and torque without shortening the life too much. Somebody did an engine upgrade (I can't remember) and did extensive modifications to the machine, only to have it damaged by turning on the PTO without anything attached.

Good luck with this. I sure would like the extra power for my 422. Although by this time I have gotten use to it.

Consider buying a 1430 and making an adapter for your existing attachments.

Good questions and comments.

I can weld, fabricate and machine at a pretty basic level, but I don't want to get into anything like modifying the tub. Those kind of projects tend to spin out of control. I'm hoping to find something that doesn't require more than drilling a few holes and splicing some wires.

I'd love a 1430, but unless Santa leaves me a bag of 100's, that's not gonna happen.

[Gravy]

Well, a Kohler Command CH 25 will obviously fit in the pan...

Moss, I, and others are running them. Is your configuration with all three pumps on one end, or are there pumps on both ends of the engine. I haven't checked to see what the size of the new, larger Kohlers are....

Personally, I'd be tempted to try the 24HP Honda... quiet and reliable.

Kent,

I'm not entirely sure that the Kohler will fit. Mine has all 3 pumps in front of the engine. I think there was a pretty extensive redesign when PT changed engines and wheel motors (and maybe some pumps).

I'm very tempted by the Honda engines, but I REALLY want more power. Unfortunately Honda quotes net HP and Robin quotes gross HP. Apples & oranges...

[Gravy]

Some other issues - Will the pumps and wheel motors take the additional speed and torque without shortening the life too much.

I don't worry much about this. The relief valves should protect the pumps and motors from excess pressure. Higher speeds might increase wear rates, but I'm hoping to find an engine that makes more power without spinning faster.

[Gravy]

I would also love an electric version as an additional machine. It would be great for those quick hauling & loading jobs that don't last long enough to warm up an internal combustion engine. I'd probably convert a PT180 and change attachment plates to share buckets.

[MossRoad]

PJ's PT425 has a Kohler engine in the back and all three pumps in front of it, so a Kohler can be mounted in there. The hard part will be finding the correct mount for the variable volume pump to mount to the engine. You might want to consult Terry at Power Trac on that to see if it would be hard to swap a Kohler for the Robin.

[MossRoad]

Here are some observations I made about PJs machine back in 2006.


It was nice to see an updated model of the PT425. Paul痴 is, I believe, about two years newer than mine. Some observations I made were:

- His tractor is several inches longer than mine.
- It is much, much quieter than mine with the same Kohler engine. I believe this is due to the mid mount muffler and insulating wrap around that muffler.
- His motor is turned 180 degrees from mine and set at the very rear of the engine compartment so that the cooling fan is pointed out the back.
- In front of the engine is his tram pump, which is hydraulically operated VS my cable operation.
- In front of the tram pumps are his two PTO pumps. Mine are behind my engine.
- His fuel tank is in the hood. It was very easy to open the hood. I was very surprised as I expected it would take more force.
- The battery and hydraulic filter are mounted way up high, where my fuel tank would be. This looked like a much superior setup than mine. Everything was much more accessible.
- His treadle assembly is the hydraulic version and the foot pedals require a very light touch compared to mine, which I have to stomp down on due to the spring tension in my hydroback assembly.
- His wheel motors are mounted much diffently than mine, They are on individual brackets that are bolted to the frame, whereas mine are mounted on a different type of bracket that is welded to the frame.
- He also has the higher lift height. I noticed the front shelf of his model where the lift cylinders are attached is deeper than mine, with a large recess in the front.

[KentT]

Don't know if you're aware of this place -- Padgett's Small Engine Warehouse. They have some of the best prices I've seen on new engines. I've not bought one this size, but I did buy a 6.75 HP lawnmower engine from them at one heck of a good price.

They have 3 pages of different horizontal shafts in the 24-27HP range.

*Engine Search by Small Engine Warehouse

[Gravy]

I stopped by Power-Trac and talked to Terry and Keith. They encouraged me to stick with the 25hp Robin on the grounds of it being a direct fit and because of the horsepower input limits of the pumps. Terry did say that I could probably get away with 2 or 3 more HP without too much risk.

On the other hand, Honda has a new GX690 engine that looks like it might fit with just a little finagling. According to the drawings, the Honda looks like it is a little bit longer and a little bit narrower.The main engineering issue might be the bolt circle for the pump adapter. I haven't looked at that in detail. I need to find better drawings for the Robin.

Translating the "net" vs. "peak" power ratings, it looks like it probably would be called a 27 or 28HP engine compared to the Robin 25. The displacement is a bit less at 690 vs. 720cc's, but the compression is significantly higher at 9.3/1 vs. 8.3/1. It looks like it might make as much power at about 3200RPM as the Robin does at 3600RPM. I'd love to be able to get the job done at lower RPM's.

I've loved every Honda engine I've ever had - they start easily, run quietly, and don't seem to break as long as they have oil. The Honda GX690 seems to be priced about the same as the Robin EH72D. If it will physically fit and is actually available for the advertised price, I will probably try it.

[tracdoc]

Well, I'm sure impressed, Gravy. Even considering an engine transplant in a PT is leagues beyond what I would take on. The only "consideration" I could possibly offer relates to our going where no one had gone before in the missus' race car a few years back. We took a perfectly good full race prepped Mini Cooper S (supercharged), and for reasons that are thankfully cloudy now that time has passed, decided to twin-charge it by adding a turbocharger. The R&D was very hard on the pocketbook, since different race engine shops had radically different ideas. In hindsight---what a flail!!! We eventually realized that a car with front wheel drive and the aerodynamics of a barn door was not able to effectively deal with 300 wheel HP. Terry's advice may be the most sage of all....