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[kiwimodeller]

Greetings all, I was looking tonight at how to mount a small engine in a hull and trying to decide whether to tilt the engine to line up with the propshaft and use a single U Joint or whether to mount the engine vertical and run double universals to take care of the fact that they were not in line. Any ideas as to which is best. With a vertical boiler I felt it might look better if the engine was vertical too but I am happy to be put straight (or angled for that matter)! Cheers, Ian.

[bogstandard]

Getting away from the UJ bit.

You might find that the engine won't be as efficient if you run it in a vertical position as opposed to the normal horizontal position it should be in.
This is because you will be setting up one side friction areas in the engine, say the sides of each piston, the crank webs rubbing against the bearing blocks etc. For an engine that has free running fits, as a steam engine is, it should always be mounted in the correct orientation it was designed for.

With regards to UJ's. I would always go for the double jointed setup on a steam engine, rather than a single one.


Bogs

[boatmadman]

Bogs,

Why would you prefer a double universal joint then? Enlighten us please

Ian

[Bunkerbarge]

I'm not sure if I read this differently to Bogs but I understood the question to be either angle the engine to line it up with the shaft or use a double UV joint and mount the engine vertically?

I think personally it is nothing more than aesthetics and the vertical engine looks better than the angled one.  However either way I would always use a double UV joint.  If you think about it a single UV can only allow for an angular misalignement but a double one can allow for angular misalignement as well as parallel offset.  My own steamer actually has a vertical 'V' twin double oscillator but I have still fitted a double UV joint.  It simply allows for any misalignement, which you may well end up with no matter how careful you are in the installation.

I would mount the engine vertically with a double UV joint.

[knoby]

Hi Ian, I personally always use double u j where ever space allows. On my current tug project I wished to mount the boiler as low as possible for stabilly & keep all the mounting plates at the same level. This resulted in the engine being 7 mm lower than the shaft, so I used a double U J to overcome this. The whole engine / shaft assembly rotates very smoothly & the extra movement allows easier removal of the engine for maintenance & cleaning.

cheers Glenn

[Circlip]

Wow, the pin and leather washer drives have really got lost in time then??   

   Regards  Ian.

[bogstandard]

Sorry I got myself a little muxed ip about the engine mounting.

If possible the engine should be mounted onto a horizontal surface rather then an angled one. This is because of what I mentioned, wearing faces. A horizontally mounted engine will have less uneven wear on it after a long running period than one mounted at an angle.

The double UJ is to take up the misalignmant between the horizontal engine and the angled propshaft. Whereas with a single UJ, you will usually find it will bind in certain places because of the larger angular offsets than is normally encountered in an electric motor installation, where the motor is usually aligned with the shaft a little better.

Bogs

[Steamer]

U Joints should always be used in pairs or you will have uneven rotational velocity which will cause lots of vibration.  Using two cancels out the rotational velocity changes during rotation

In addition, you should also make the angle between the engine crankshaft and the drive shaft equal to the angle between the drive shaft and the prop shaft, for the same reason.

Dave

[Circlip]

NO vibration with oiled leather      

[Steamer]

NO vibration with oiled leather      

YUUUUUP!


Horses for courses....if your propeller weighs a few grams and turns at several hundred rpm max.....I wouldn't get too wound up about 1 UJ ......several ounces on a 11000 rpm screaming nitro engine...you should.

[derekwarner]

"In addition, you should also make the angle between the engine crankshaft and the drive shaft equal to the angle between the drive shaft and the prop shaft, for the same reason"

Sorry Dave .......if bogstandard can get MUXED up so can I

If we had the engine crank in the horizontal plane and the prop shaft say 15 degree offset ....by fitting a twin UJ coupling would the assembly not automatically provide a 7.5 degree offset in each element?.......... Derek

[Steamer]

Ahh yes.....That is a good point and thankyou for pointing that out.  To get the angles even depends on the height of the engine with respect to the end of the propeller shaft and/or the length of the drive shaft.....it's a geometry problem.

For example.  If the end of the crankshaft is say at the same height as the end of the propeller shaft, the drive shaft will be parallel with the crankshaft and the U joint at the propeller shaft will be stuck with compensating for the whole angle. 
Here's a sketch...You can end up with the other extreme also.   Your choice is to adjust the length of the propeller shaft and the length of the drive shaft to suiite your engine's vertical position.   Or   You can adjust your engine's vertical position and the driveshaft length to suite your propeller shaft length.  Or move your engine front to back to compensate for the propeller shaft height and the drive shaft length
  Your choice.   
Make sure the drive shaft yokes are in line!.....or its all for nothing.  Keep you propeller and drive shafts as short as practicable.


 

Now to your point, a double UJ is nothing more than a short drive shaft.  The geometry can still get you if your not paying attention.

Some sketches of your situation on a piece of paper will show you the way.  Runout and balance at high speeds is also critical....every situation is unique


Dave

[kiwimodeller]

Well it is pretty much "UNIVERSAL" by the look of it that I need two U Jonints and I need to work on getting both of them to have a small angle in each, that is unless I can source some leather washers. I guess the problem is not so pronounced with an engine that is only doing a few hundred revs (which is what I like to load my steam engines down to) but perhaps the old set up on one of my older engines of two pins sticking out from the flywheel with pieces of plastic tube slipped over them and a cross piece on the prop shaft might not be so silly. There does not seem to be any way this would bind up. Thanks for all the discussion. Cheers, Ian.

[flashtwo]

Hi,

On my experimental flash steam vessel "Vital Byte", I'm using a simple dog-clutch to couple the Stuart D10 engine to the prop shaft, i.e. screwdriver in the slot method.

The shaft angle to horizontal is 3.9 degrees and the engine is shimmed for and aft to give the same angle and correct coupling height to the prop shaft.

The prop shaft (with its bearings) and engine are mounted on separate base plates and the plates have a couple of connecting bolts to maintain their relative positions.

For alignment, I position the prop shaft slot vertically, then rotate the prop shaft slightly either direction and check that there is equal play in both directions. I then position the slot horizontally and again check for equal play in both directions. If the play is unequal I then adjust the engine position. The slot and tooth are made with sufficient clearance to stop them binding and to give some play in the adjustments.

With this method I can remove the engine and boiler assembly from the model by positioning the slot vertically, undo the two bolts between the base plates and then lift the assembly out. To refit the assembly is lowered in and the two bolts refitted without having to re-align the shaft.

In use, I have found no coupling binding and currently the engine is being run up to 600RPM.

I'm exhibiting Vital Byte at the Guildford Steam Show this weekend - I hope to see a few Mayhemers there.

Ian.

[bogstandard]

What happened before the introduction of modern day couplings, about 40 to 50 years ago?

All you would have would be a pin sticking out of the flywheel and another on the end of the shaft, no more alignment problems.

This shows a high powered version, utilising two pins, for high power applications.



This could cope with REAL alignment problems.

It is only since we started to use 'proper' couplings that alignment became a major issue. You have to get everything in line BEFORE you fit the coupling. A little back to front if you ask me.

We do make life difficult for ourselves with all these new fangled ideas.

Bogs

[tobyker]

Don't forget the rubber tube on the pins!

[Bernhard]

hi.........in my African Queen,,,and ,,my big launch with the proteus in,,,and the Hemmens Diana Max2...And a graham engine,,,,i use a pulley and a rubber o ring,,,,,,
 just work great with no problems.

Regards Bernhard

[Steamer]

It makes no difference to me which you use....the pin an bar arrangement has worked for thousands of models......I just commented on how to use a UJ correctly.

What gets the "boat the to float" for you is entirely a personal decision on the part of the builder.

Dave

[flashtwo]

Whoops.....

Hi Bogs,

I've over-engineered yet again!


Ian.

[bogstandard]

Just a bit of light humour I am afraid, but it does go to show, that sometimes, being too technical can get in the way of common sense, and make life more complicated than it was before.

I use an old saying when I build something, 'what isn't there can't go wrong'.
 
We British are renowned the world over for making things too complicated for their own good. We will use a dozen components to make something that only really requires a couple to get the job done.

Bogs

[derekwarner]

"We British are renowned the world over for making things too complicated for their own good" ......well yes & no Bogs  not many will ever get to see a pre WWII warship mechanical gun director computer 

Yes MECHANICAL - they used low voltage high frequency [200 Hz] motors with antibacklash fitted.....but all of the computations are via linkages + arms + cam disks & lots of UJ couplings    Derek