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Are there any 'rules' about coupling two motors?

I've got two identical 3,5 kW series motors (from one fork-lift) to drive one prop-shaft in a small boat.

I can connect them front to rear so they both turn the same direction, or couple them rear to rear wich is easyer to do because of matching axle sizes and endplates.

The motors won't be over-revved and will be fed 48v as they got in the forklift, brushes on 0 degrees.

Will it be a problem if they turn opposit directions?

I'm planning on using flexible jaw-couplings.

Electricity fed via a single controller and two reversing switches.
 

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Re: Coupling two motors, jaw-coupling?, fw / rev

As long as the motors have separate field and armature terminals then you can run them either way without advance.

You should be able to drive them DE to CE or CE to CE and the DE to the prop. I can't see it making much difference unless the CE shaft is much too small to take the torque.

The Lovejoy type coupling is usually not up to a road going EV but it might be ine here if it is sized properly.




Major will probably spot something worth noting.:)
 

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Discussion Starter #3
Re: Coupling two motors, jaw-coupling?, fw / rev

My website is up again, so I can ad some pictures:


We had to lose the fan's, and will be adding external forced cooling. (motors will have to withstand hours of 80% power)







Just a little bit of cleaning will be enough.


Bearings were shot, good thing we took them apart.


The subject of the conversion, black one behind it is Diesel-Electric :)
 

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Re: Coupling two motors, jaw-coupling?, fw / rev

I am officially jealous of your shop. Me want.
 

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Re: Coupling two motors, jaw-coupling?, fw / rev

Hi boekel

How much power does that hull need?

I think you are going to be able to throttle your twin 3.5Kw motors down when cruising at hull speed
This is good - it means that cooling is not going to be an issue

On a related note how are you designing your prop sizing?
with electric direct drive I would be going for a nice big prop to improve the efficiency

If you are thinking about replacing an IC direct drive engine with similar size prop - don't - the IC engine will be running with a small prop to get the engine speed up and its efficiency will suck
 

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Discussion Starter #7
Re: Coupling two motors, jaw-coupling?, fw / rev

Hi boekel

How much power does that hull need?
Not much, hull speed is about 6,5 knots or 12 km/h
I'm aiming at a cruising speed between 10 and 12 km/h with 5 kW
I think you are going to be able to throttle your twin 3.5Kw motors down when cruising at hull speed
This is good - it means that cooling is not going to be an issue
I have some big heatsinks from a 75 kW industrial AC motordrive to cool the controller, motors via temp-controlled fan to replace the original fans that had to make room for a coupling.
On a related note how are you designing your prop sizing?
with electric direct drive I would be going for a nice big prop to improve the efficiency
I asked what I needed for 7 kW / 1350 rpm, and found a nice second hand prop, wich will have to be trimmed down to fit the boat. test driving will tell if it needs more trimming.
If you are thinking about replacing an IC direct drive engine with similar size prop - don't - the IC engine will be running with a small prop to get the engine speed up and its efficiency will suck
I sold the old prop together with the diesel engine.
 

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Re: Coupling two motors, jaw-coupling?, fw / rev

Hi Boekel

I have some big heatsinks from a 75 kW industrial AC motordrive to cool the controller, motors via temp-controlled fan to replace the original fans that had to make room for a coupling.

Do you need fans? - with all that lovely cold water I would be looking at some way of running water past the heat-sinks

Not much, hull speed is about 6,5 knots or 12 km/h
I'm aiming at a cruising speed between 10 and 12 km/h with 5 kW


I will be very interested in what you find - I suspect (with no real data) that with a big efficient prop you could be well below 5Kw
 

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Discussion Starter #9
Re: Coupling two motors, jaw-coupling?, fw / rev

Hi Boekel

I have some big heatsinks from a 75 kW industrial AC motordrive to cool the controller, motors via temp-controlled fan to replace the original fans that had to make room for a coupling.

Do you need fans? - with all that lovely cold water I would be looking at some way of running water past the heat-sinks
Using water means a hull-opening, pump, filter, etc. so with the big 'free' heetsink it's a lot easyer. (also no worry about freezing in winter)
 

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Re: Coupling two motors, jaw-coupling?, fw / rev

After some troubles with two couplings that were slightly different from the others and finding a fast and relatively cheap source of the right size ones (compatable with lovejoy, but much cheaper)...


Ready for assembly...


cleaned up.


mounting holes marked.


And made...hopefully without distroying all magnetic properties...


halfway...

Fresh bearings.


Nice machine for heating al kind of things (as long as it has a hole in it) also used for the bearings and the aluminium end-plate.


The 'wrong' coupling.


damaged because of cooling down to much before pressing on the axle.


Hmmm...
 

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Re: Coupling two motors, jaw-coupling?, fw / rev


This one is shrinked onto the turned down gear that was on the motor before.


High-tech drawing...


New coupling arrived.


Kelly-controller arrived.


Removing (other) wrong coupling (after heating with torch).


Almost right.


Complete drive-train.


I'll first make this fit in the boat, after that some adjustments are to be made for proper aligning.
 

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Re: Coupling two motors, jaw-coupling?, fw / rev

Some numbers:

250A 8 42v = 10,5 kW = 12-13 km/h (short bursts)
50A * 46v = 2,3 kW = 8 km/h (10 hours of cruising)
25A * 47v = 1,2 kW = 7 km/h (20 hours of cruising)

It works brilliantly! wish we had converterd years ago!!

Prop is still to 'heavy' so only 8-900 rpm = lower voltage on motor = more Amps than neccesary = something to do ;)
 
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Re: Coupling two motors, jaw-coupling?, fw / rev

That just plain rocks. That is one sweet conversion. I liked seeing you moving both boats. You got me thinking again of converting my ski boat to electric for the purpose of cruising and skiing. Much smaller and lighter. Anyway kudos to you and your crew for a fine job indeed.

Pete :)
 

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Re: Coupling two motors, jaw-coupling?, fw / rev

Hey boekel,

I watched your vid and the propulsion system turned out really nice. Great job :)

I then reviewed your thread and those armatures caught my eye. I was just this week talking about multi turn bar wound armatures on another post. And I swear, you have armatures with 2 turns per coil. I invented this back in 1979! The company gave me $1.00 for it, built a few prototypes but never went into production with it. Just wondering what brand of motors those are. Don't worry, patent rights are long expired ;)

Regards,

major
 

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Re: Coupling two motors, jaw-coupling?, fw / rev

Hey boekel,

I watched your vid and the propulsion system turned out really nice. Great job :)

I then reviewed your thread and those armatures caught my eye. I was just this week talking about multi turn bar wound armatures on another post. And I swear, you have armatures with 2 turns per coil. I invented this back in 1979! The company gave me $1.00 for it, built a few prototypes but never went into production with it. Just wondering what brand of motors those are. Don't worry, patent rights are long expired ;)

Regards,

major

Better image...


And the other side...I noticed there seem to be two 'layers', is that what you mean by multi-layer?

More Pictures: http://boekel.nu/ (look for 'sloep')


Regards,
Daniël
 

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Re: Coupling two motors, jaw-coupling?, fw / rev

And the other side...I noticed there seem to be two 'layers', is that what you mean by multi-layer?
Yes, that's what clued me in. It is a way in which 4 coil sides (conductors) can be placed in each slot (the path through the steel laminated core). Most all the DC EV motors have single turn armature coils where there are just two conductors per slot. The multiturn method gives higher generated voltage per RPM without resorting to very high comm segment counts or resorting to using round wire coils. In short, your motor will turn more slowly than the usual ones of that size at the same voltage, but give you more torque for a given current. Considering you say you have a course prop, I think a good match :)

Cheers,

major
 
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Re: Coupling two motors, jaw-coupling?, fw / rev

I should have kept this motor. It was not exactly like his but a damn nice motor. It has been banded to hold together under abnormal conditions. They guy who purchased this motor has one hell of a nice motor. Not the same as the GE I currently have.

http://greenev.zapto.org/ge/9"_GE/Welcome.html


Pete :)

Love the motor in that boat. Love the conversion. Nice photos in the photo album.
 

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Discussion Starter #20
Re: Coupling two motors, jaw-coupling?, fw / rev

In short, your motor will turn more slowly than the usual ones of that size at the same voltage, but give you more torque for a given current. Considering you say you have a course prop, I think a good match :)

Cheers,

major
Nice to know :)

A single bigger motor would have been so much easier to use... But the results are great, just have to take the motors apart once more to turn the communicator round (we forgot to check that, the brushes wobble on it)
 
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