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Old 18-01-2015, 19:40   #1
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Accessory drive shaft

Does anyone have experience of an additional drive shaft for accessory pumps, generators and the like. I can recall seeing one only. Obviously useful to take lateral loads off the engine bearings but presume there are downsides. Noisy? Direct transmission or belt driven?
Any reports appreciated.


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Old 18-01-2015, 19:48   #2
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Re: Accessory drive shaft

I've seen HD bilge pumps run off a mag-clutch from the front crankshaft damper. And some of the Yammers have a second mounting bracket for another alternator.

Wouldn't it be great if marine trannys had a PTO shaft, like on tractors, for running extra accessories!
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Old 18-01-2015, 20:42   #3
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Re: Accessory drive shaft

These are commonly used in fishing boats where you want a transfer point away from the engine. I used one which had a magnetic clutch on one end which was belted to an extended shaft pulley on the engine. The other end drove a hydraulic pump. They are usually available at commercial fishing supply stores.
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Old 18-01-2015, 22:56   #4
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Re: Accessory drive shaft

Good to know. And if memory serves, there may be a bit of info on them in the Dashew's book. Plus, I'd imagine that shops which work on industrial engines which have to "work for a living" would know about such things.
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Old 18-01-2015, 23:04   #5
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Re: Accessory drive shaft

I believe it is available with Beta engines. Might be worth checking.
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Old 19-01-2015, 08:33   #6
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Re: Accessory drive shaft

There are two ways of pulling power off of the front end of the engine. Belts are one way, straight out shafts (axiel loads) are the other. Both are good, but both can introduce problems if done incorrectly.

Most engines have limitations to the amount of power that can be pulled from the front of the engine. This may be limited by key or taper strength on the front hub, torsional considerations within the crank, bending load on the crank, etc.

Belt drives can introduce bending into the crank, so there can be limits to the amount of power pulled off and also limits to the distance the pulley overhangs the front main bearing. Also there can be restrictions on the direction of pull of the belt, or combinations of belts.

Axiel loads don't introduce bending issues, but there might still be power limitations, and there might be torsional vibration issues introduced as well. Normally torsional issues are resolved by the use of a rubber "damper" element between the driver and the driven element.

In either case it's a good idea to consult with the application engineers employed by the engine manufacturer or importer before getting in too deep.

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Old 23-01-2015, 22:43   #7
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Re: Accessory drive shaft

I'm 66. When I was young, some of the older commercial boats still were using power takeoffs to run winches. The boats would have a shaft going to the anchor winch and another going aft to gurdies or seiner winch. But in those days even small diesels were heavy duty. Except for Cat or Cummings most smaller diesels today are light duty. You can only take so much power off the crank pulley without having other problems. And it isn't free power. The closer you get to peak HP the more fuel and oil will be used. The best way to take power off the crank is a front power takeoff in line with the crank (no side loading).
You can run an aux shaft parallel with the engine with roller bearings with a large enough diameter to handle the horse power you're going to pull off. An open shaft is dangerous. It can wrap line, clothes or people around itself with all the horse power of the engine. A lot of farmers get wrapped in PTO shafts.
If running a AC generator is your goal, a better way is an inverter and bigger alternator. That's how I run w/o running an ac generator. Another choice would be to add hydraulics.
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Old 23-01-2015, 23:41   #8
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Re: Accessory drive shaft

Quote:
Originally Posted by Lepke View Post
I'm 66. When I was young, some of the older commercial boats still were using power takeoffs to run winches. The boats would have a shaft going to the anchor winch and another going aft to gurdies or seiner winch. But in those days even small diesels were heavy duty. Except for Cat or Cummings most smaller diesels today are light duty. You can only take so much power off the crank pulley without having other problems. And it isn't free power. The closer you get to peak HP the more fuel and oil will be used. The best way to take power off the crank is a front power takeoff in line with the crank (no side loading).
You can run an aux shaft parallel with the engine with roller bearings with a large enough diameter to handle the horse power you're going to pull off. An open shaft is dangerous. It can wrap line, clothes or people around itself with all the horse power of the engine. A lot of farmers get wrapped in PTO shafts.
If running a AC generator is your goal, a better way is an inverter and bigger alternator. That's how I run w/o running an ac generator. Another choice would be to add hydraulics.


That sounds all very reasoned. I think you are right - hydraulics and bigger alternator maybe safer, easier and more flexible.
Thanks


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