Engine alignment ---HELP !!!

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adelaidem

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Quote : 'Using a feeler gage constantly after every little move,shuffle the engine according to demand until no greater error or misalignment than 0.030mm per 25mm of flange diameter is apparent.'

My engine is hard mounted

My flange diameter is reading 125mm (5") Therefore i assume that i can have an acceptable misalignment of no greater than 0.15mm. This seems to be hard to achieve. Can anyone elighten me on this as i have spent all day trying to achieve this .. advice will be greatly appreciated
 
Get the top to bottom gap right first by adjusting the front engine bearers only. Then move all screws equal amounts to achieve the right height without changing the angle. If you have screw adjusters this should be fairly easy otherwise use packing. Only when you have the height and tilt angle of the engine right should you attempt to swing the engine sideways (usually there are slots in the feet bolt down screws to facilitate this) to get the side gaps equal.
If you are a long way out go through this sequence twice or more but don't try to make all adjustments at the same time.
 
Ok that may be the problem I only have Up and Down adjustments which i use shims on the front feet which works fine,its the right side of the flange that im haveing trouble with.wondering what tolarance i can get away with.The quote I have posted allow very little tolarance is this correct?
 
No one said it was easy but here is a simple method:
measure the gap between the flanges at 12 O'clock and 6 O'clock the adjust the shims until these measurements are with in (in your case 0.15mm) or less. Actual shim thickness can be calculated or you can do it by trial and error.

eg difference in measurements = 1.5mm, distance between front and rear engine mounting points = 450mm > shim thickness required = (1.5/125) X 450mm where 125 is your flange dia at the point of measuring. If the 12 O'clock reading is the larger then the shims need to be placed under the front engine mounting.

Now with a dial Gauge mounted on the driven flange measure the vertical misalignment at 12 and 6 and add the appropriate shims to all engine mounting points.
eg if total dial reading between top and bottom is 3.4mm (with the engine flange lower then the driven flange) you need to add 1.7mm worth of shims under all mounting points.

The engine should now be aligned in two axis, Finally "jiggle" the engine left and right to obtain equal gap between the flanges at the 3 O'clock and 9 O'clock positions. Tighten the mounting bolts and recheck all measurements , adjust as needed and repeat until correct alignment is achieved. If after a couple of re-adjustments you still cannot achieve correct alignment then something is wrong and you should seek the services of a "professional".

Alternative is to fit a flexible coupling to take up any minor misalignment or even an "Aqua Drive™" which will absorb considerable misalignment.
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"Artificial intelligence is no match for natural stupidity"
 
OOPS missed the other post but yes your figure of 0.15mm seems correct although I would aim for much less like 0.03mm max.
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"Artificial intelligence is no match for natural stupidity"
 
.305 seems the best I can get from on top bottom and port side this feels good .030 seems as if i need paper style gauge 360deg. radial around the flange.
 
Sounds more like you have a damaged flange, you should be able to get the variation in the gap within 0.03~0.05mm relatively easily. If it is within tolorance at say 6, 9 and 12 and way out at 3 then you have a problem with the flanges.
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"Artificial intelligence is no match for natural stupidity"
 
Answer posted under other post titled 'Help'. O.15 mm tolerance is fine. 0.03 - 0.05mm is certainly preferable but not essential. As stated in previous post, most flexibly mounted engines will move quite considerably when underway - a combination of initial torque and weight of the engine.
 
Thanks for the help, From what I have read it seems as i should crane the diesel out AGAIN then elongate the front mount holes so that i can get better side ways alighnment. makes me wonder how the orginal builder managed to alighn the donk with the setup she has at present.
 
A flexible coupling will allow you a degree of safe error, especially as you are not using rubber mounts. On my yanmar's the mounts are pretty soft and thus it is possible to move the engine and it wont come back to the original position, so trying to get tolerance down to 0.05mm is just not going to happen.

I have flexible couplings on each engine and am comfortable with that. They are single cylinder engines and the vibration alone when running makes the whole 0.05 feeler gauge a bit of a joke.

Just thought I would add this as a different perspective.
 
Fenner's rubber tyre type flexible coupling produced in flywheel and shaft mounted versions is very long lasting and will tolerate considerable misalignment.

This is not to say that couplings should not be carefully lined up.

A problem with boats is that they flex as the sea moves so that close tolerances which can be achieved on land with a rigid steel baseplate or with machinery bolted to a concrete foundation are achieved only whilst the ship is motionless.
 
When installing the 3GM30 in Aeolus I deliberately planned to install a flexible coupling. While I still tried to align the engine and shaft up a close as possible, the presence of the coupling simply gave peace of mind that nothing unexpected would happen if it wasn't quite right.

Taking the coupling and shaft out of the boat a couple of week ago showed no obvious signs of stress in the coupling, so it must all be working OK. They are not that expensive (the simple ones that is), and if you've space, I'd consider putting one in.

However, this doesn't relieve you from the effort of ensuring the center of the shaft and engine coupling line up. For this you need an expensive bit of kit.

Regards, Jeff.
 
If it's only to cut ovals into the mounting bolt holes, couldn't you support the engine and just lever it up enough to get the mounts in and out?

IMHO, if not, fitting a flexible coupling is likely to prove less hassle than removing the engine - and probably little if any dearer if you have to pay for craning in and out.

If you've already got some sort of coupling between the flanges, I reckon you should have room for a Bullflex. You remove the old Prop shaft flange and the bullflex slips over the shaft and grips the round part of the shaft. The tip of the shaft could an inch or less from the grearbox flange if necessary. All you need is the shaft/hull clearance, which needs to be about 80mm from memory, over about 150 mm back from the flange. I had plenty of room in my 24, so I doubt you'd have a problem
 
Engine mount feet are now removed and the holes slotted once removeing the front mount bolts i was able to move the front of the engine about 4mm which was enough to alighn the coupling,suprised she had been alighned for 20 yrs the way it was!
 
Cliff and I are saying the same thing. He with more detail.
I would only add that it is important that you do indeed ensure that the flange on the shaft and engine run true when rotated before you start. Have seen people spending many happy hours lining up an engine to a bent shaft..... Assuming that is OK, yes the tolerances you are working to are fine and should be adhered to regardless of the fact that you have a flexible coupling. The main purpose of the latter is to allow some engine movement on its mounts when running, not to take care of misalignment.
One more thing. All measurements should be done (or at least double checked) with the boat afloat not out of the water. On some boats the difference can be considerable.
 
You will probably find thet once you put the boat back in the water and tension the rigging you will have to move the engine back the 4 mm. Alignment on the hard means SFA, is a waste of time, and frequently is "miles out" Get her back in the water and redo the alignment.
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"Artificial intelligence is no match for natural stupidity"
 
Slighty drifting away from the problem in hand. Why did hydraulic drives never make themselves popular? Some systems negated the need for gearboxes as the reversing was done in the drive pump using valves, and some systems varied the output speed using valving rather than engine speed.
Alignment wasn't an issue, and engine placement was made more flexible.
Was it a cost thing?
 
I think it was originally because the hydraulic drives were relatively inefficient. Modern hydraulic motors may have overcome this inefficiency to some extent. <span style="color:brown"> </span>
 
Correct. They are also often noisy. The big advantage of them is
that you can put the engine anywhere which is often an advantage on a shallow draft inland waterways vessel.
 
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