lining up engines

[Guest]

The texts on this subject are all very glib. Is it really possible to achieve the tolerances stated? It might just be possible in the vertical plane where adjustment can be made with the screw threads on the engine mounts, but what about laterally? The only adjustment seems to be a lever and brute force. Does anyone have any tips?

A.h.

 

[stamfordian]

You can line up the engine in Horizontal plane by using a "clock" micrometer,this is basicly a mic with a dial and a follower which when pushed in or out registers a diatance.They usually come with a magnectic base or you can just fix it to a point on the engine ;rest the follower on say the shaft then turn the whole thing,engine and all adjust so pointer stays stable or near to it.Cruder idea is to just mount a simple pointer say a dot punch and do it by eye..depends how accurate you can accept and the tolerance required.hope this helps.ps will sort all directions!!

<A target="_blank" HREF=http://www.arweb.co.uk/argallery/stamfordian>http://www.arweb.co.uk/argallery/stamfordian</A>
<P ID="edit"><FONT SIZE=-1>Edited by stamfordian on 29/09/2002 21:42 (server time).</FONT></P>

 

[30boat]

Levers and brute force are probably the only means of moving an engine lateraly especialy a big heavy one.Since you probably need only very smal adjustments it shouldn't be to much of a problem however it is usualy hard work.

 

[vyv_cox]

It depends a little on the amount of space available, but I place a length of rod against the foot of the rubber mounting and tap it with a small hammer. This is enough to make minor adjustments. With a very heavy engine, take some of the weight with a hoist, get the lateral aliignment correct, release the hoist and do the verticals. It is certainly possible to get down to thousandths of an inch at the coupling.

 

[Robin2]

The more I think about it the more I asl myself "why bother?". It seems to make so much more sense to have a universal joint between the engine and propellor shaft to alleviate all of the issues connected with engine vibration.

Why is it the tradition to have rigid (or nearly rigid) couplings between engine and shaft? It can't save that much money.

 

[peasea]

Make some wooden wedges - gentle taps with a mallet can give controlled
movements. Make sure you can wedge against something substsantial that you
wont damage!

 

[yoda]

I agree

 

[Avocet]

I've never been able to understand the almost religious fanaticism with which people tell you to align your engine! I've got a nasty little single cylinder diesel and it hops up and down about 15mm on its rubber mountings at some engine speeds - so the idea of aligning it with a dial gauge is a bit, well, odd! I gave up after a while and made up something a bit like a Vetus / Halyard coupling with two rubber "doughnuts" from Centa Transmissions. OK, it only has to transmit 12 Hp but it seems to work OK. It did wonders for the vibrations through the rest of the boat and I've never bothered lining it up other than roughly by eye since I fitted the coupling.

 

[Guest]

Subject to the manufacturing tolerances of the gearbox and propsgaft couplings and with a solidly mounted engine on substantial engine beds in a properly built boat it should be easily possible to align the engine nearly perfectly. It may be hard work but the result will be worth it in terms of long term reliability and lack of wear. Even if flexible mountings and couplings are used this does not remove the need to do a proper job of engine alignment. Plastic couplings will not do any more than cope with very minor axial misalignment. They will not absorb properly the movement of most flexibly mounted engines. Any significant misalignment will take a toll on stuffing gland, shafting, stern bearing etc. If contemplating anything other than a properly and carefully aligned instalation then install an Aquadrive or Hardy Spicer shaft (with suitable thrust bearing of course). I have to say that the majority of yacht installations are frighteningly poor and clearly only survive on the basis that they are only lightly used.

 

[chippie]

The universal joint idea is ok if there is a thrust plate between the prop and the gearbox. Universal joints are not made to transmit forward thrust.
The proprietary marine CV joints on the market incorporate a thrust assembly when fitted.

 

[peasea]

the_bargee is spot on!

 

[vyv_cox]

Having installed an Aquadrive myself, I can advise that they are not the answer to a maiden's prayer. Installation is pretty straightforward but designing the thrust plate needs a certain amount of tedious shaping to make a pattern, followed by having this converted to a steel plate. That took most of a weekend. Then final shaping of the plate and glassing it in took another. When the completed job hit the water I was quite disappointed at the results. There continues to be quite a lot of transmitted vibration, far more than there was previous to fitting the drive. Knocking of the shaft on the stern tube, which the Aquadrive was fitted to cure, is less but not eliminated. Some further alignment will occur shortly which hopefully will progress things further.

Incidentally, I had a lot of trouble in sourcing the smallest of the units, the 20000 from memory. I see that a new unit has been announced, so maybe that will improve the situation. In UK the problem may not be so acute but Halyard will not export and in Holland supplies of some sizes are not easy to obtain.