Marine engine - universal joint to prop shaft?

[peatrich]

Hi
The title says it all really. I wondered if it is common practise to tilt a marine engine down towards the stern of the boat so that some sort of straight coupling could be used, or mount the engine level and fabricate a universal joint to the propeller shaft?

If a universal joint is used, does anyone have a plan for one?

This is more from curiosity and the pleasure of making a working model, but I would like to see how it is achieved in miniature. My only experience of such joints is of much larger ones on cars and shaft driven bikes.

kind regards
Peatrich

 

[lennardhme]

Hi Peatrich,
Tilting the engine is common in both full size & models, but you dont give much info on engine or boat type etc.. Depending on the project you may be better off with a dogdrive & much easier to make. Also has the advantage of no load for half a rev when reversing - helps the engine get going. For smaller models a dogdrive with a rubber band between the driven spigots & a shorter driving arm that engages the rubber band 'gives' if you hit an obstical & can save damage.
Leonard

 

[peatrich]

Thanks Leonard
I'm building a single oscillator as a first engine and have plans and materials for a small vertical engine with a 4" flywheel, but for a boat I was thinking more of a small V twin/V four oscillator.
I like the fact that it would fit in a small space to power a boat about 4 feet in length.

kind regards
Peter

 

[waynes world]

preswitch models in your country does alot of marine parts they have an web site aswell. most boaters use flexible drive lines not solid shaft for racing aplication. for scale stuff like your doing has it own set of running gear to which is a lot lighter in construction as the is no demand on it in regards to performance. ready made items so you dont need to turn your lathe on just for them cheaper to buy them .

 

[Ed T]

I have a couple of old Bassett Lowke marine wobblers that my dad got back in the 1920's. They both use a very simple coupling where there is a disc on the propshaft with a radial slot in it and a pin in the flywheel that engages the slot. While it is generally good practice to get things reasonably lined up, this type of coupling is pretty forgiving and can easily handle the massive torque of most wobblers. I think some more modern offerings have used a small length of rubber tubing to good effect.

 

[peatrich]

Thanks for the comments. I hadn't considered the prop being obstructed under water and reading that a rubber coupling is used makes sense to prevent damage. I like the idea of a simple mechanical solution though and I suppose the simplest is tilting the engine!
Kind regards
Peter

 

[ELM6061]

The many normal sized inboard boats that I have seen, have all had tilted engines, the very few models that I have seen, have also had tilted engines.

One of the models had what was similar to a universal joint, On the end of each shaft there was a small U shaped coupling and these were bolted to a rubber ring (for memory, bike tube) 180 degree's opposed from each other.

Eddie

 

[tel]

Universal joints are not at all hard to make - just study a 'real' one to get the idea and whittle 'em out.

 

[peatrich]

I just love that whole set up Tel. Could you be persuaded to send me a plan of that engine, please?

kind regards
Peter

 

[tel]

Thanks, - it's just an Elmers no 52 with a few embellishments of my own. Bit of a photo essay of the build at http://entertainment.webshots.com/album/576272987AyhWNQ?start=0

Plans here; http://www.john-tom.com/ElmersEngines/52_vertTwin.pdf

 

[peatrich]

Thank You very much Tel.

 

[tel]

Up close

 

[peatrich]

Ha Ha - Now I can see it!

Brilliant picture, thank you Tel.

 

[Herbiev]

Jaycar Electronics have a few very good uni joints
Part #YG2782 $14.95
Part #YG2608 $49.95
Part #YG2604 $24.95
These are ideal for what you are looking for
WWW.JAYCAR.COM.AU
No connections- just a happy customer

 

[peatrich]

Thank you Herbiev
kind regards
Peter

 

[JohnLanark]

You mght enjoy browsing the installations on full size boats in the Steamboat Association's online Register. John.

http://www.steamboatassociation.org.uk/Default.aspx?pageId=1117882

 

[around]

Peter,

Another example.

Cheers,

Adrian

 

[sunworksco]

I use Graupner u-joints, when not machining from stock.
They hold up well and look appropriate for steam engines.