Hydraulic driven jet drives question??

Very unlikely. Hydraulics is a good way to take energy from one prime mover and operate lots of motors/rams. Eg a JCB, where one diesel engine operates lots of actuators and hence does all the lifting and steering. Hydraulics are also useful if the prime mover and actuator need to be some distance apart

But hydraulics are noisy, inefficient and expensive. So if you just want to do just one thing, namely drive the impeller of a jet unit by a nearby diesel engine, it would (in general) be crazy to insert hydraulics into the food chain as the means of transfering the power. Much better to use a shaft and bolt the impellor straight to the engine, so minimal efficiency losses

Hence, I dont think you'll find what you want being mass produced. You're into bespoke territory I think. Although, you could just take a standard hamilton-like jet drive, and bolt it to a standard hydraulic motor??

But your project sounds interesting! What are you making/building/refitting/repairing??
 
thought as much. there are several ways of doing what i want to do, hydraulics would be one, but like you said we're into bespoke areas (which ultimatly mean cost).

can't say too much about the project as it is still firmly mounted on the drawing board. a case of watch this space.



regards, steve
 
Yup, you're looking at 20 - 30% energy loss through heat and mechanical efficiency losses depending on the type of system so definitely better to have mechanical drive but maybe aztec is thinking about multiple drives from a single prime mover?
 
Sounds interesting!

The Vetus catalog contains quite a lot of hydraulic motors and pumps. They have enough bits in there to set up a yacht with one diesel engine located anywhere, driving a propshaft via hyraulic pump/hoses/motor. And I think they have valves so you can use same diesel engine to drive alternator (genset) and maybe bowthruster/winch. Worth a look, but all v expensive and much easier in a sailboat just to get the jigsaw out and wham a saildrive in. Also I think they're only transmitting 35bhp or something of that order. Maybe worth a look though?

Catalog is online. www.vetus.co.uk. Click "sales program" and scroll down to "hydraulic marine propulsion"

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you may be on the right lines there...

but to do what i want to do, i could use a hydraulic pump mounted to the engine, and leave the shaft intact.

the idea was to use one pump for everything. but that wasn't the prime concern.

thanks for your input though, explains why it's not a common drive system.
 
Power take off you mean? Thing is, unless the auxiliaries you want to drive by hydraulics and PTO are very big, it's easier and lighter just to have an electrically powered hydraulic pump
 
Also hydraulic motors are good at low revs / hi torq applications wheras water jets are hi rev/lo torq operators, so to get one mated to t'other wd need a gearbox which 1 costs, 2 saps power and 3 needs to be fitted somewhere.
 
All the above. I reckon the friction losses alone in the pipes would make it non-goer. To move enough hydraulic oil at a rate fast enough through small pipes would be an achievement in itself.
 
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