Single Diesel Driving Twin Hydraulic Props

[Cheechako]

Originally Posted by a64pilot

Many earth moving pieces of equipment, farm equipment and now even zero turn lawnmowers use hydrostatic transmissions, which is really just a fancy way of saying hydraulic.
However I believe the monstrous stuff is all electric, maybe electric takes huge sizing to work the best?
Hydraulic works, but isn’t as efficient as direct drive, both trains and big Earth moving stuff the transmission is problematic as the power transmitted is so great, and electric and hydraulic requires no transmission, and I think that is why it’s used.
I suspicion that the US Navy actually paid for the development of electric trains, but perhaps the train came first

Yes, my buddy has a 4wd Kubota small tractor that is hydraulic drive at the wheels. Seems pretty good, but it isn't asked to turn much rpm on a tractor!

[a64pilot]

To put those numbers that sound horrible into perspective, a good Diesel engine is between 30% and 35% percent efficient, so a drop from 30 to 21 isn’t as bad as it sounds at first

[snoozy814]

Originally Posted by smj

I’m wondering if maybe it’s his hydraulic system that’s overheating?

yes. the water line that cools it wasn't put in large enough so the hydraulic system overheats. that is being corrected. However, it is still very inefficient even when cold due to power transfer.

At this point looking at a direct drive unit instead as we're making some changes to the boat to make her a better sailing vessel (they'd added a bunch of stuff which really increases her windage, lines not run right for single/double handing easily, different stack pack which works better, etc.

[snoozy814]

the idea w/the hydraulic drive is that it would give you much better turning (like a zero turn lawn mower in theory) which is great for docking. In practice, not as simple as that.

[snoozy814]

"We have a catamaran now with a single outboard on a sled and also a cat with twin outboards in lifting pods, advantages to both.
I believe you own a Kelsall? Have seen Kelsalls around 38’ with both a single centrally mounted outboard on a pod and also twin outboards. "

Yes, it's a Kelsall 38'. We did consider the outboards on sleds (double) and the drive system we're designing may work similarly in that we want to be able to lift it out. Good friend of ours is a mechanic up at Morris in Maine, was formerly at Hinckley, and said yes that should work well for us. Now it's to the engineering part of it. Thank you 3D CAD type software (Rhino is our friend)!