Cheap ways to load and engine

[robbieg]

I have a 27hp Yanmar diesel in my garage and would like to test it by running it for a few hours under load without putting it in the boat and/or buying any expensive kit. Anyone any ideas?

I have looked at running a generator but to put a reasonable load on the engine would mean a big generator which I don't have. I have thought of a disc brake coupled to the gearbox with a couple of brake pad on a clamp arrangement to provide friction although would need to spray with water to keep it cool but may work and relatively cheap. Any other ideas?

TIA

 

[PabloPicasso]

add a prop running in a big bin of water. May have to leave a top up tap running or use a cistern type arrangement but no fire risk

 

[VicS]

A dynamometer is what you need but possibly not cheap

http://www.taylordyno.com/catalog/engine-dyno

perhaps you can get a cheapy for a few quid off ebay

 

[Bobobolinsky]

A big air mover, or a compressor running against pressure.

 

[aluijten]

How about a old airplane propeller from a small plane?
I think these need to be replaced regularly so a used one may be relatively easy to obtain.
But I know little about air crafts so I may be mistaken.

 

[Slowtack]

Driving a pump lifting water thru a height using energy comparable to driving your boat at cruising speed??

 

[William_H]

How about a old airplane propeller from a small plane?
I think these need to be replaced regularly so a used one may be relatively easy to obtain.
But I know little about air crafts so I may be mistaken.

I would not think this the answer. Most a/c props run at 2700 RPM max power and would not provide so much load at lower RPM. Plus of course incredibly dangerous having this noisy thing swinging around in your shed. No a/c props are overhauled regularly but not replaced unless they are unsafe. Which would make it unsafe in a shed.
My best suggestion is electrical generator. If you go to a wrecking yard (car breaker) you might find something big off a truck. 24v Alternator preferably. About 600 watts is one horsepower. At 12v is 50 amps or so. Load it up with lamps or electric elements (not 240v ) . good luck olewill

 

[Lakesailor]

What a lot of effort.
Stick it in the boat and test it under load there. If it's OK you done the next bit of the job anyway.

 

[Malish]

What a lot of effort.
Stick it in the boat and test it under load there. If it's OK you done the next bit of the job anyway.

+1 and a lot of risk / damage if you get it wrong

 

[prv]

I've seen parachute-simulator rigs which use a brake consisting of a sort of paddlewheel. A hub, 8 or 10 spokes, each with a panel about a foot square on the end of it. This rotates easily when going slowly, but quickly builds up air resistance when you try to turn it fast. Enough to let someone jump off a tall tower on a rope attached to a drum on the brake shaft, and descend slowly to the ground. There's generally a mesh cage over the whirling paddle blades.

That's what I'd build if I needed resistance, but unless you have lots of engines to test, I suspect Lakesailor has the right idea.

Pete

 

[jdc]

Some thermodynamics

Whatever load you use the output will be converted to heat unless you can use the work, such as transferring electricity to the grid, pumping water up hill or pushing a car or boat along (strictly this converts to heat as well, but there's lots of air or water volume involved).

27HP is about 20kW. The engine itself will be running at only 20 - 30% efficient, so that's another 60kW or so needed to be removed to keep the engine cool: a total of 80kW to get rid of - for 'a few hours'. Say a bit less than 2 hours, then that's about 0.5 Giga Joules. 0.5 GJ will boil away 220 kg of water! Alternatively it would bring to the boil, from 20 degrees C, 1.5 tonnes of water.

Your system, whatever it is, is going to get jolly hot. I'm not sure I'd bother, but if you do you'll need a serious truck radiator system and a big fan, not a 'spray' of water.

PS: Why for a couple of hours? Won't a couple of minutes do?

PPS: On second thoughts, if you have a swimming pool, then maybe you could absorb the heat and be useful at the same time.

 

[rogerthebodger]

"On second thoughts, if you have a swimming pool, then maybe you could absorb the heat and be useful at the same time."

He can heat my swimming pool if he likes, it a bit cold here at the moment, for us anyway

 

[robbieg]

Thanks all

Some interesting ideas but sadly none that seem particularly cheap! The engine is not for my boat-have a fine rebuilt engine in that that I spent a last winter putting in so not about to take it out again. On my travels I have picked up the 27hp engine which looks great and starts and runs well with no load. However, some faults only show up when an engine has work to do and gets hot-hence the question. Lot easier to fix and sort out an engine problem when on the bench rather than when buried in the bowels of the boat. Anyway today I set up the disc brake system and seemed to work ok-applied the pad pressure with an adjusting screw until it started to pull the revs down a bit and then throttled up to around 2000rpm. Cooled the disc with a old washer bottle motor and a bit of tube and ran it an hour or so-all good. Total cost about £30 and a few hours of my time fixing it up.