Ideas welcome on how to attach 2 shafts of different diameters

[thor85]

TL;DR Summary

I have 2 different shafts, one goes into a motor and the other into a 3 phase generator. How to fix the two shafts together? Assume the motor and the generator will not be perfectly aligned.

I have a motor and a 3 phase generator which I would like to connect together, i.e. let the motor drive the generator and measure it's output.
Each have their own type of shaft which do not fit together. I would therefore like to get some proposals, preferably which do not require custom work at a machine shop, on how to connect the two together.
The motor and the generator will not be perfectly aligned.
What would be the easiest, or most low cost method?
The diameter of the generator shaft (on the left in the bottom image) is 30mm.
The diameter of the motor shaft is 25mm.

 

[Baluncore]

Welcome to PF.
That looks like the PTO shaft from a gearbox with a gear between two journals.
Why is there a gear on the generator shaft? Will that gear be used?
Is that a 6 tooth spline on the other end of the generator shaft?

 

[thor85]

Welcome to PF.
That looks like the PTO shaft from a gearbox with a gear between two journals.
Why is there a gear on the generator shaft? Will that gear be used?
Is that a 6 tooth spline on the other end of the generator shaft?

Thanks.
I removed the generator along with the generator shaft from a small electric vehicle. It went into a gearbox on the vehicle. The gears will not be used.
The end goal is to use the generator with some kind of wind propeller to generate electricity.
I have just started this process and I figured that since I have a 1hp,50rpm motor I will connect the two in order to make some initial measurements, i.e. what voltage it generates at 50 rpm and see if I can make DC power from the 3 phase to charge a battery or drive some other circuit.
It is a 10 tooth spline. That shaft is the only thing I have that fits inside the generator.

 

[Baluncore]

It is a 10 tooth spline. That shaft is the only thing I have that fits inside the generator.

You may find it easier to avoid the gear. Short splined shafts are stock items and can be purchased from PTO shaft and drive-line suppliers.

"Taper Lock" bushes are available for any diameter shaft. Google "Taper Lock".
There are several taper lock systems in different sizes available. Select a system that is bigger than either shaft to be joined. Then get two different bushes to fit the shafts.

There are also taper lock flexible couplings of different types.
Look at the taper lock HRC Couplings.
https://pineriversbearings.com.au/power-transmission/couplings/

And there are bigger, more tolerant systems.
https://www.ebay.com.au/itm/332854007597

 

[Lnewqban]

Is the last picture showing the actual arrangement of shafts?
If so, and the gear is not going to be used, how do you plan on transfer power into and simultaneously support the non-key end of the left shaft?

 

[thor85]

Is the last picture showing the actual arrangement of shafts?
If so, and the gear is not going to be used, how do you plan on transfer power into and simultaneously support the non-key end of the left shaft?

Not sure if I fully understand the question. But the last picture is indeed showing the actual arrangement of the shafts. The gear is not going to be used. The plan was perhaps to use bellows couplings or similar to attach the two together, but that is actually my question to you guys that are more familiar with such things than I. The generator (left) and the motor (right) would be approximately aligned (not perfectly) with each their supporting structure and therefore any support for the left shank would not be needed. How to transfer the power between the two shanks is the question of this post.

 

[Lnewqban]

I see.
My question was, how each shaft is supported?
I assume two bearings for each shaft.

 

[berkeman]

Maybe use a motor-generator to do the coupling...

 

[Rive]

I have a 1hp,50rpm motor

To be honest, I don't think that that RPM will fit well with any generator. And the RPM feels way too low for any motor I know about too. If that RPM is correct then I feel the smell of some future disappointments there.

The diameter of the generator shaft (on the left in the bottom image) is 30mm.
The diameter of the motor shaft is 25mm.
...
The motor and the generator will not be perfectly aligned.

I think you still may need to machine some 'shell' like diameter extender for the smaller shaft, and then you may use one of those thick, reinforced, multilayer high pressure hoses to connect the two shafts.
Though the large diameter shaft has only a limited depth for the connection... And since the shafts are smooth, if not done well then the hose might slip, though that might be even useful...

This kind of stuff:

(random image from the internet)

... well, kind of oooops: that picture is apparently not about shaft connection. Still, it looks the very same between shafts too.
I'll try to find a different pic.

 

[jack action]

How about something like this (from @Baluncore 's link):

Where you hold each end to its respective shaft with a bolt? (Both of your shafts seem to have a threaded hole at their end.)

The friction alone will probably be enough for your low-power application.

 

[anorlunda]

This kind of stuff:

Here's what you are thinking about, designed for the purpose. Some of them sell for as little as $10.

 

[thor85]

Here's what you are thinking about, designed for the purpose. Some of them sell for as little as $10.

View attachment 319987

Yes, where can I find them? And what are they called?

 

[anorlunda]

Yes, where can I find them? And what are they called?

They are called "flexible couplers". That picture, I found on amazon.com

Edit: Try this search
https://www.google.com/search?q=flexible+shaft+coupling

 

[thor85]

I ended up using the idea from Rive essentially using a garden hose and some clips. It works well since the speed is low and the load on the generator as of now is low. Thanks all for your responses.

 

[Rive]

It works well since the speed is low and the load on the generator as of now is low.

- Please, make a photo of it I could not find anything about this kludge online, though my parents had this for the pump way back.
- Just keep in mind, that you'd need to be more serious for anything more serious.

 

[thor85]

- Please, make a photo of it I could not find anything about this kludge online, though my parents had this for the pump way back.
- Just keep in mind, that you'd need to be more serious for anything more serious.

Of course!
Below is a photo of the setup as of now.
On the drive motor shaft (25mm outer diameter) I placed a smaller hose that has inner diameter of approximately 25mm and an outer diameter close to 28-29mm for diameter buildup.
The drive motor is on the left, rotating at about 62 RPM.
DC motor which I (plan to) use as a generator is on the right.
You were also right that the voltage that the generator generates is quite low, in the order of 30mV at 62 RPM. What I mentioned to be the drive motor on the left is actually gear output from said motor. The gear ratio is I suspect 24:1, so I could remove the gears and attach 1400 RPM motor to the generator directly to get more accurate measurements. That will surely test the quality (or lack there of) of the coupling.
Now I just have to figure out how to connect the generator correctly, i.e. S1, S2, S3, S4, A1, A2 as it just has 4 wires sticking out.

 

[Rive]

That will surely test the quality (or lack there of) of the coupling.

A cover (even just a temporary one) might be a reassuring addition.
If those screws which are locking the clips accidentally catch something, then...

Ps.: once you spin up that generator for higher RPM, you'd need to care for the electric shock hazard too.

 

[thor85]

A cover (even just a temporary one) might be a reassuring addition.
If those screws which are locking the clips accidentally catch something, then...

Ps.: once you spin up that generator for higher RPM, you'd need to care for the electric shock hazard too.

Both excellent points!