Engine mounting angle?

A special section just for steam engines and boilers, as without these you may as well fit a sail.
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Petel
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Engine mounting angle?

Post by Petel » Mon Dec 02, 2019 9:24 pm

I'm at the stage in my rebuild where I need to consider engine mounting.

My question is what are the pro's & con's of fitting the engine in line with the shaft (i.e. tilted back by some 8 degrees) or fitting it horizontally?

The thrust bearing is fitted to the shaft close to the prop end the engine flywheel connects to the shaft via an automotive CV joint, so bar a very small efficiency drop there is a good degree of articulation available. Is there anything else to consider?

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Lopez Mike
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Re: Engine mounting angle?

Post by Lopez Mike » Tue Dec 03, 2019 2:12 am

One small consideration might be that the closer to having the engine and shaft in line with each other, the less wear on the CV joint.
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cyberbadger
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Re: Engine mounting angle?

Post by cyberbadger » Wed Dec 04, 2019 5:40 am

Depends on whether you want to fit the engine to the boat, or you want to fit the boat to the engine. :)

If I could have told myself a bit of advice on the engine mounting at the beginning of building Nyitra it would be to add a clutch mechanism so you can decouple the engine from the propeller. The feature I also would like would be the the ability to run accessories: hypro mechanical pumps & DC Permament Magnet Alternator off my engine when I'm sitting at the Dock.

I think honestly with the availability of so many good bearing options, the question of the engine mounting angle does not have to be so important. There are certainly a lot of ways to skin a cat...

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Re: Engine mounting angle?

Post by steamdon-jr » Thu Dec 05, 2019 12:41 am

Many old books and even the Elliot Bay instructions suggest mounting the engine firmly on jack screws, dialing it in with an indicator to be perfectly aligned with the shaft, damming and pouring grout...this method is great if you plan on keeping the engine for your entire life. We chose to mount the engine on Unistrut so we could shift any engine forward or back, we then slid in the prop shaft as far as it could possibly go and then got 2 universal joints at Tractor Supply, bought a length of shaft to fit between, put in keyways and installed. we can change and try any engine we want with a simple 4 bolt swap and if needed a section of shaft to be longer or shorter between the 2 universal joints. There is a pillow block bearing mounted to a piece of steel angle iron we placed to act as a thrust bearing so the shaft will not yank out
Has run flawlessly for 8 years.
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Lopez Mike
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Re: Engine mounting angle?

Post by Lopez Mike » Thu Dec 05, 2019 5:43 am

My installation, which has worked for several years of hard steaming, is to mount the engine securely but only roughly in line with the shaft and have a single U-joint quite near the engine.

My engine takes the trust internally (ball bearing mains). You can add a single pillow block thrust bearing if needed but AT the engine. At any reasonable angle (less that about ten degrees) a single U-joint works fine without introducing any serious torsional oscillations. The U-joint will absorb any amount of thrust.

I don't know about other launches but my shaft packing is mounted to the stern tube on a short length of radiator hose so relative motion between the engine and shaft doesn't affect the function of the packing.

Not having to do a precision job of aligning the engine is great. I wish I had installed a U-joint on my sailboat years ago! Boats flex both between in the water and out as well as moving about to some unknown degree when trailering.

I've spent my last afternoon fiddling about with shim stock, feeler gauges and dial indicators!
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DetroiTug
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Re: Engine mounting angle?

Post by DetroiTug » Fri Dec 06, 2019 1:45 am

A billion +/- inboard speedboats, simply mounted the engine in line with the prop shaft and used a rigid coupler. That is how the tug is, no issue with it whatsoever. The engine is leveled and aligned with wood wedges under the motor mounts. Keep in mind there is some power loss going through a jointed coupler at an angle.

I made the one in the pic. For some reason, they are really expensive to purchase.

A little fussy to align using feeler gages, but once aligned, there is nothing to wear out or make noise etc.

-Ron
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Lopez Mike
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Re: Engine mounting angle?

Post by Lopez Mike » Mon Dec 09, 2019 11:00 am

Ah, but Ron, you have an extremely rigid steel hull. Every bit as stiff as your power plant. I envy you.

Both my previous hull and this new one flex a quite a bit between being on the trailer and off, loaded with rather generously proportioned (euphemism for lard assed) passengers or not and simple flexing in a seaway, said seaway being mostly caused by stinkpot I.C. engined speedboats (grump!).

Most of my boats have been set up as yours is in the traditional way and I never considered that there was any alternative until relatively recently. Using either a U-joint or some sort of flexible coupling has been an eye opener with much reduced vibration.

My first eye openers were a couple of limited class hydroplanes with fairly extreme amounts of power being transmitted through simple chain couplers. Easy to disconnect quickly for engine removal and totally reliable and quiet (unlike the engines).

I rejoice in no longer needing to stand on my head with a feeler gauge in one hand trying to remember which way to shim.
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