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Author Topic: Motor/prop shaft Alignment  (Read 13634 times)

Richard M

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Motor/prop shaft Alignment
« on: March 01, 2009, 02:08:20 pm »

Sorry folk, a basic question.

How do I align prop shaft and motor? I have seen articles proposing a temporary solid coupling which makes sense. Unfortunately I am retired and no longer have access to a lathe.
Are these couplings available commercially or will I have to end up going wallet in hand to a local machine shop? What else could I try?

Richard M
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maninthestreet

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Re: Motor/prop shaft Alignment
« Reply #1 on: March 01, 2009, 02:19:26 pm »

Styrene tube, just a little large than the coupling diameter???
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John W E

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Re: Motor/prop shaft Alignment
« Reply #2 on: March 01, 2009, 02:49:58 pm »

Hi there Richard M

When you say align motor with propshaft, I take it that you already possess a coupling.   What make of coupling do you have?

If its the coupling that has either the 2 brass inserts into a plastic housing; the plastic housing may be either red or black.   

The method I use for aligning these up - is to remove the 2 brass inserts from the plastic coupling housing; find a piece of solid tubing which slips over the splines of the brass inserts neatly - so that there is no slop.   This then replaces temporary the plastic insert and holds the 2 brass inserts in line.  So, you may now then proceed with the positioning of your motor and mounting of it. 

Obviously when you have mounted the motor and are satisfied with its alignment you then remove the temporary tubing which you had installed.

aye
john e
bluebird

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Richard M

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Re: Motor/prop shaft Alignment
« Reply #3 on: March 01, 2009, 03:07:30 pm »

Hi maninthe street and bluebird

Thanks for your comments. I have the red couplings with brass inserts and had tried to find tube in my local DIY store but without success. Styrene tube is a gret idea and I will look for some the right size.

Thanks again

Richard.
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craftysod

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Re: Motor/prop shaft Alignment
« Reply #4 on: March 01, 2009, 03:32:14 pm »

If you are going to align lots of motors,use this.
Got one and its great
Mark
http://www.mobilemarinemodels.com/acatalog/Protolign.html
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Richard M

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Re: Motor/prop shaft Alignment
« Reply #5 on: March 01, 2009, 04:02:30 pm »

Thanks craftysod. This looks brilliant. At the price it represents about 50p for every hour I spent in trial and error last time.

Richard M
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Martin [Admin]

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Re: Motor/prop shaft Alignment
« Reply #6 on: March 01, 2009, 04:33:11 pm »

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Marks Model Bits

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Re: Motor/prop shaft Alignment
« Reply #7 on: March 02, 2009, 07:44:02 am »

This is how I do mine and I have found it to be a good way of getting perfect alignment.
First, line up your motor and shaft by eye and make sure you have some movement on your motor mount to adjust your motor.
Then connect an ammeter into the circuit, power up the motor and make small adjustments until you achieve the lowest reading on your ammeter.
The pic below might explain it better.
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dreadnought72

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Re: Motor/prop shaft Alignment
« Reply #8 on: March 02, 2009, 09:21:38 am »

May I ask a question?

Clearly it is best to align the shaft-and-motor along one axis. And clearly it's best to firmly set the prop tube and motor into the hull.

So why do we use jointed couplings at all?

Andy, probably suffering from early morning bemusement.
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Colin Bishop

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Re: Motor/prop shaft Alignment
« Reply #9 on: March 02, 2009, 09:41:54 am »

Because however much care you use in originally setting it up, misalighnments creep in. The motor rotates and the bearings wear, the propshaft will have some play in its bearings and they will also wear in time. The supporting hull structure may flex and introduce thermal movement - when you put it in cold water for example. All these factors are small in themselves but will give misalignment, vibration and a degree of binding. The flexible coupling soaks up these movements and allows the motor and propshaft to run as freely as possible.

Colin
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chipchase

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Re: Motor/prop shaft Alignment
« Reply #10 on: March 02, 2009, 09:56:35 am »

Hi dreadnought  the coupling is the weakest point between motor and shaft, the coupling breaks first so there is no damage done to the more expensive bits.

I have seen shafts weighing 52 ton shearing their coupling bolts like butter. :embarrassed:

Brian

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Re: Motor/prop shaft Alignment
« Reply #11 on: March 02, 2009, 11:37:01 am »

Also, if anyone that finds motor / prop shaft alignment difficult, consider using double couplings (Cardan type couplings) as the alignment process is a lot less difficult / critical.
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tobyker

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Re: Motor/prop shaft Alignment
« Reply #12 on: March 02, 2009, 11:45:00 am »

There is a size of brass tube available from the Metal Centre rack which fits the splines on the brass couplings exactly. Just cut a piece the right length and Robert is your father's male sibling.
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lozvik

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Re: Motor/prop shaft Alignment
« Reply #13 on: September 12, 2009, 10:20:17 am »

This is how I do mine and I have found it to be a good way of getting perfect alignment.
First, line up your motor and shaft by eye and make sure you have some movement on your motor mount to adjust your motor.
Then connect an ammeter into the circuit, power up the motor and make small adjustments until you achieve the lowest reading on your ammeter.
The pic below might explain it better.

Im just trying out this idea in the pic but cant understand how to get the motor to turn to be able to get a reading, is it just me being a bit dim or am i missing something here? how is the motor powered with a lead off the positive from the battery?
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swampbug

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Re: Motor/prop shaft Alignment
« Reply #14 on: September 12, 2009, 10:57:25 am »

Isnt it good when you think of a question but afraid to ask because you think its a bit daft to ask and we should know the answer, then someone else asks lol  :-))

I wasnt sure why we bother to align the engines when we use swivel joints too lol

Martin love your write up about the way you do it, made me smile  :D
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malcolmfrary

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Re: Motor/prop shaft Alignment
« Reply #15 on: September 12, 2009, 11:27:06 am »

Im just trying out this idea in the pic but cant understand how to get the motor to turn to be able to get a reading, is it just me being a bit dim or am i missing something here? how is the motor powered with a lead off the positive from the battery?
The black wire between motor and negative solves the problem nicely.  I would prefer to use the minimum amount of battery to turn the motor - it turns more slowly and variations are easier to spot. 
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lozvik

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Re: Motor/prop shaft Alignment
« Reply #16 on: September 12, 2009, 11:50:42 am »

erm no, it still makes no sense to me im afraid, how can the motor turn if theres only the negative wire connected?? can anyone shed a bit more light on this please, sorry im a bit of a novice with this kinda stuff
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aestus57

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Re: Motor/prop shaft Alignment
« Reply #17 on: September 12, 2009, 12:04:54 pm »



 :-))

  Neg terminal on battery to neg terminal om motor, pos termoinal on motor to neg lead on ammeter, pos lead on ammeter to pos terminal on battery, ... hence ammeter is commected in series in the circuit.

Hope that explains it.

Peter
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aestus57

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Re: Motor/prop shaft Alignment
« Reply #18 on: September 12, 2009, 12:07:36 pm »

Just noticed all my spelling mistakes !! it's attrsious!!!  sorry, ... awful !! Qh well I guess it can be understood !!!
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lozvik

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Re: Motor/prop shaft Alignment
« Reply #19 on: September 12, 2009, 12:48:48 pm »

I must be missing something here, or im not explaining myself properly, once I have attached the ammeter etc how does the motor turn so that I get a reading?  by just connecting the motor, battery and meter up as explained does not seem to power the motor? im confused???
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Greggy1964

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Re: Motor/prop shaft Alignment
« Reply #20 on: September 12, 2009, 01:49:21 pm »

Try this,

The sketch might make it clearer
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aestus57

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Re: Motor/prop shaft Alignment
« Reply #21 on: September 12, 2009, 01:58:40 pm »

You also need to make sure that the ammeter will handle the likely load, ie up to 10 amps, some multi meters will only measure up to 250 milli amps, thats only 1/4 of an amp  :-))
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malcolmfrary

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Re: Motor/prop shaft Alignment
« Reply #22 on: September 12, 2009, 01:59:54 pm »

To help with the sketch, if you start at the battery + terminal, through the ammeter, through the motor, back to the battery negative, thats all you need for a circuit.  Current will flow round the circuit described through the motor which will then do its best to turn.  You then tweak the alignment for lowest current drain and/or highest RPM.
This is all assuming a normal brushed motor.  If the assumption of a brushless motor has been made, then this is another case entirely.
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lozvik

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Re: Motor/prop shaft Alignment
« Reply #23 on: September 12, 2009, 02:15:56 pm »

well guys ive read all yr replys 10 times over but i still havnt had a single turn from the motor! perhaps i have the wrong type ammeter or something {:-{
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aestus57

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Re: Motor/prop shaft Alignment
« Reply #24 on: September 12, 2009, 02:28:12 pm »

You may have blown the fuse in your multi meter, open up the back of it and check that, but don't put a bigger fuse in it than that which was in originally as you will fry the circuit board!!  Can't see what else it could be. Good luck and let us know how you get on.
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