The Steamboating Forum

I should have said Permanent Magnet DC brushed motor. Which is by far the most common type of small DC motor.
-Ron

Andy, those Converted GM alternators to PM Dynamos are really too large for the application. Most steamplants don't have an extra two or three horsepower to charge a flat battery. Even my little 120 watt 1/6th horsepower generator slows the boat down. The reason I only use it when needed.

DetroiTug wrote:I should have said Permanent Magnet DC brushed motor. Which is by far the most common type of small DC motor.
-Ron

Andy, those Converted GM alternators to PM Dynamos are really too large for the application. Most steamplants don't have an extra two or three horsepower to charge a flat battery. Even my little 120 watt 1/6th horsepower generator slows the boat down. The reason I only use it when needed.

That's a fair statement. I have thought about clutches. I'd like to be able to do this at the Dock. I'd rather not be able to disconnect the prop, because I fear that would introduce the possibility that a clutch could fail somehow and then you are adrift. In my case I may just use a small auxilliary like my stuart 4a.

-CB

Quote: "I have thought about clutches. I'd like to be able to do this at the Dock. I'd rather not be able to disconnect the prop, because I fear that would introduce the possibility that a clutch could fail somehow and then you are adrift.""

Don't really need a clutch, just some switching means to take the battery out of the circuit, then the generator is just free-wheeling. That is exactly how I'm doing it and with good ball bearings in the generator, there is very little power required to spin it. The Servo that I used (it's all coming back to me now) had a plain bearing on the pulley end which failed. I machined a counterbore in the motor endplate and installed a sealed ball bearing - problem solved.

-Ron

DetroiTug wrote:Don't really need a clutch, just some switching means to take the battery out of the circuit, then the generator is just free-wheeling. That is exactly how I'm doing it and with good ball bearings in the generator, there is very little power required to spin it. The Servo that I used (it's all coming back to me now) had a plain bearing on the pulley end which failed. I machined a counterbore in the motor endplate and installed a sealed ball bearing - problem solved.

I know if you disconnect the electrical load from the pma/generator it will provide minimal mechanical resistance.

I mean clutch to disengage the prop at a dock. If I want to charge at a dock and not be thrashing my prop to charge electricity.

However I am quite reluctant to introduce a clutch to disengage the prop, because of KISS.

-CB.

cyberbadger wrote:

DetroiTug wrote:Don't really need a clutch, just some switching means to take the battery out of the circuit, then the generator is just free-wheeling. That is exactly how I'm doing it and with good ball bearings in the generator, there is very little power required to spin it. The Servo that I used (it's all coming back to me now) had a plain bearing on the pulley end which failed. I machined a counterbore in the motor endplate and installed a sealed ball bearing - problem solved.

I know if you disconnect the electrical load from the pma/generator it will provide minimal mechanical resistance.

I mean clutch to disengage the prop at a dock. If I want to charge at a dock and not be thrashing my prop to charge electricity.

However I am quite reluctant to introduce a clutch to disengage the prop, because of KISS.

-CB.

a coupler with a shear pin you can take out?

lostintime wrote:a coupler with a shear pin you can take out?

Don't have a coupler or sheer pin installed.

My "coupling" is center sprocket of engine -> chain -> jack shaft -> Powergrip belt -> propellor shaft.

The belt I don't want to mess with, because that would change the tension which is an adjustment.

The chain I suppose I could swap to something else but It's not particularly quick to swap..

My "sheer pin" is the belt. I have a replacement onboard, but the Powergrip is pretty robust. It will skip and then you know the prop is stuck (has occurred with a rope wrapped around propellor, and also rock propellor constrainment" )

-CB

An idea for your drive system that would disengage. As lostintime points out a simple removable pin would work.

You have a timing pulley on the jackshaft, use a timing pulley (preferably steel) with a hub, bore it out or order one with proper bore size and press in an oil-lite bronze bushing, then drill a hole through the hub and shaft for a "shear pin" or bolt or whatever. That's not going to be overly complicated and problematic, none more so than the set screw securing the upper pulley now. A 1/4" .25" steel rod or bolt with self-locking nut would be ample for the load. Could even select a softer material and use it as an actual shear pin, saving the belt. In power transmission application, that is how it should be.

-Ron

Just like the shear pins on a snowblower, simple and effective.

I would be a little cautious about using a shear pin, if the engine does not have a flywheel, or if there is a fly wheel but it is not sufficiently large enough, there will be oscillations in the prop shaft that will continually be working at cutting/shearing the pin. In order to use a large enough diameter pin you will probably still need to make some significant modifications to your setup, and in order to reinsert the pin you will have to rotate the engine or prop shaft to the correct position each time which will become a nuisance, an even greater nuisance if there is any longitudinal float in your prop shaft . Remember to have a bag of spare pins and patience in your tool box. A commercial tapered tooth dog clutch would work well and be more user friendly, but would be more expensive. You may find suitable parts at a used machinery yard.

Cheers

Lionel

Lionel Connell wrote:I would be a little cautious about using a shear pin, if the engine does not have a flywheel, or if there is a fly wheel but it is not sufficiently large enough, there will be oscillations in the prop shaft that will continually be working at cutting/shearing the pin. In order to use a large enough diameter pin you will probably still need to make some significant modifications to your setup, and in order to reinsert the pin you will have to rotate the engine or prop shaft to the correct position each time which will become a nuisance, an even greater nuisance if there is any longitudinal float in your prop shaft . Remember to have a bag of spare pins and patience in your tool box. A commercial tapered tooth dog clutch would work well and be more user friendly, but would be more expensive. You may find suitable parts at a used machinery yard.

Cheers

Lionel

very true, torsional vibrations can destroy things quite quickly, any slop may cause problems. Ideally the shear bolt would pull together two surfaces, so their friction transmits the load