Hi!

Following the two separate topics regarding ball bearings and home-made stators, here is something that adds another idea.

I started of with: a 3-pole DCM that I am going to convert to DC, using the home-made stator method. I then added the ball bearing for the motor shield (brush plate).


(the stator has had the field coil removed and is still waiting for the magnet to be fitted).

Then it was time to do the bearing on the motor block side. I did the usual, removed the plastic bearing and popped in the required 4mm ball bearing. Threw in the DCM rotor, put it all together, pushed the bogie along the track, and it ran beautifully.

That's when I remembered I still had a 5-pole rotor left from a 60904 conversion kit. This rotor has 7 teeth and is normally used for converting some LFCM motors to high-efficieny propulsion. And the DCM 3-poler has 7 teeth as well.

So I wondered - could the 60904 7-teeth rotor be used to convert a DCM? And, of course, I still wanted to use the ball bearings...

On the motor shield side, the axle diameter of the 60904 rotor is the same as DCM (1.5mm), so no problems there. On the motor block side, however, the axle is obviously made to fit the old LFCM motor block, which is 2mm instead of the DCM's 1.5mm. A 2mm rotor axle means that a 5mm outer diameter ball bearing is required.

So we have to drill the motor block:

Centre hole widened from 4mm to 5mm.

And then the 5mm ball bearing is fitted:


Now then - does the rotor fit with the stator? It does:


Time to put it all together:


So here we have it: a DCM motor with the 5-pole rotor from an LFCM conversion kit and a (soon-to-be) home-made stator.

I wasn't crazy enough to try this on an actual loco; what you see in the pictures is a bare motor block that was bought off eBay a while ago because it came with a DCM HAMO magnet that I needed for a digital conversion. I'm glad I kept the block - I would not have dared try this on the beautiful 3034 that the above attempt may be applied to!

Whenever time allows, I will get the magnet and convert the stator and have a trial run. Then - and only then! - will I decide whether or not to butcher the motor block of the 3034... Wish me luck guys!

Hi,

Thank you very much for the pictures.

This is a very nice practical work.

I do think the motor will work and have enough torque output, even though if, for sure, the power will be less than it would if proper DCM-5 pole had been fitted. What laalves says is true, but in this case I think clearance value will be enough to get the engine torque moves the wheels.

I wonder if you could test-run it before with a coil stator, in order to check if it's worth the effort to fit the homemade magnet (provided you have a coil DCM stator around).

The reason explained by Laalves is the reason why I think that efficiency will improve with a stator precision machining for fitting the magnet.

Good luck, and keep us informed.

Best regards.

Richard hi,

I have the same "big gap" problem in a Hag motor with M* 5 pole rotor. Please keep us informed on this.

Cem.

Yes, the torque will drop due to the smaller rotor diameter from what it could have been, but if a neodymium magnet was fitted the the stator that was roughly the same size as a normal permanent magnet, I think the drop in torque will more than be compensated for. As for excess current draw, I think the combination of the neodymium magnet plus ball bearings will draw less current than the normal set-up, due to the much stronger magnetic field, and much less friction. I certainly, being as nearly broke as I am, can understand wanting to use a part I already had available.

Now, that said, the ball bearings, neodymium magnet, and the larger rotor would quite possibly be an amazing combination.

For me however, after having acquired a locomotive with an older C-Sine motor, and two newer ones with SDS, I would like to have a way to ECONOMICALLY convert as many of my other locomotives to this drive as possible. Not only can't the smoothness of the drive be beat for realism, NO other small electric motor comes close to competing with it for low-end torque. The torque-curve graphs that Märklin published when releasing the original C-Sine motor were NOT marketing hype at all! In fact, the way it was presented didn't play it up enough, because if you are not used to reading and understanding such data, you would have been tempted to think, "Yeah, ok, so what?"

Don Taylor

Looking forward to your testresults, Richard!

How hard is it to find the correct ball bearings? Internet source?

Ok, have it your way!
I have converted litterally hundreds of Marklin locos in my previous life (as a Marklin Service Station) and I can't see how this could work correctly. Plus you need the proper brush holder plate too, and often teh mounting screw length need to be adapted
But I don't think you are interested to learn about these vital details anyway...

Agreed! For some people (me included), tinkering around with parts and trying to adapt things for a slightly different purpose, or just trying to modify or "hack" things in general is simply part of the fun off the hobby!

Yes, most of us are aware of "the right way" to do something, but there's a certain satisfaction (for some of us) for trying to make another way, or another part, or an alternative part, or a part fabricated from scratch work successfully.

For instance, I'm still working on my crazy idea to double-head my two Br 85 locomotives by simply connecting the two motors together in parallel to the same MFX decoder (using a long thin jumper cable of course) [:o)]. It works, but for some reason I can't get the motors to turn exactly the same speed (yet)

Don Taylor

Update: the motor runs with the 5-pole rotor from the 60904 kit and the standard field coil stator. However, as predicted by Jacques, torque is almost non-existent. I am waiting to get a moment of time so I can convert the stator with the neodymium magnet and will then test both rotors again.

I did consider that myself. I'm sure it is possible, but I don't have a suitable piece to hand right now.