The Farish coreless motor - a teardown for interest

[Dr Al]

Hi Folks,

Given the decent performance of the Farish coreless motor design, I thought I'd tear down a reject (siezed up bearing) for my (and your!) interest.

Shows quite how different the internals are - the armature with no central iron/steel core, and much lighter and finer. Tiny commutator, something like half the diameter of one from a Farish can motor and more like 1/3 that of the older Poole armature.

Brushes are not carbon, instead they are the metal wiper style. I wonder their longevity - hopefully fairly long as the current draw is so low (therefore arcing less). The bearing is only at the worm end of the motor, no bearing at the brush end, which is also nice in reducing friction further.

Hope it's of interest to folks.







It is worth noting that these are basically sealed units - to get it apart needs a lot of force as the circular can is crimped and glued around the end cap. It can't just be levered off. This one came apart eventually, but it probably would never go back together (the armature does not clear the crimping on the outside of the can!).

Cheers,
Alan

[Newportnobby]

Thanks for that, even though I hope it's something I never have to see!

[belstone]

What do you think to the thrust bearings on it? Back in the Portescap days, putting a worm gear on a coreless motor was regarded as bad practice as the bearings weren't designed to handle end loadings. If these follow usual Chinese design methods they will be "inspired by" Portescap designs.

Richard

[Izzy]

Thanks, very interesting. Looks internally much the same as the 8x16 coreless motor Nigel Lawton sells. I put strip-down shots of that on the 2mmSA VAG Yahoo group site some years back. The only difference being that is 5-pole while these seem 3-pole. For their size those I have in the Farish Jinty and 4F seem very powerful.

The Nigel Lawton one was re-built and runs in my Class 15. The trick - as such - is to fit the commutator into the end plate/brush fingers (twisting it into position between them) before putting it all into the motor housing. Akward at the second stage as the motor magnet wants to pull it hard into the can. You have to put your finger over the end bearing hole and slowly let the shaft come through. This is also how I put the Farish/2mmSA can motors back together which also use just finger brushes.

The small single shaft Farish cans do have end thrust plates but most coreless types don't as I think most are made for applications where axial thrust from spur gears or belts is allowed for in the long internal main bearing but end thrust isn't because they aren't used with worm gear drives.

There has been some debate over this aspect over the years, but I believe it depends on the level of end thrust they are subjected too. The danger being the 'spring fingers' can be distorted by excess pressure/movement of the armature core/motor shaft. There are makes/types of coreless motors that have circlips fitted on the outside of the motor shaft to restrict movement and absorb end thrust. It will be interesting to see how the Farish coreless motors get on in this respect. Time will no doubt tell.

Izzy

[Les1952]

I had a few reservations over Farish moving to coreless motors having two failures out of three Minitrix locos with Falhauber motors. 

However I've been well pleased with the loco-driven Farish locos I have, at least in the motor department.  Now all we need is for consistent milling of the tyred wheels so that the power of these motors can be put to good use.

It is a little disconcerting when my 2MT can walk off with over twenty coaches in tow when my 5MT struggles with six and none of my WDs will even take that many....

Les

[belstone]

This looks too good to be true. 7 x 16 coreless motors, 12 volt, £2.50 for four, post free!

http://www.ebay.co.uk/itm/111995148610

[Dr Al]

This looks too good to be true. 7 x 16 coreless motors, 12 volt, £2.50 for four, post free!

http://www.ebay.co.uk/itm/111995148610

Very interesting find - looks just about identical to the Farish unit....

....might be the ticket to fixing the loco the motor I tore down came out of!

Cheers,
Alan

[belstone]

Very interesting find - looks just about identical to the Farish unit....

....might be the ticket to fixing the loco the motor I tore down came out of!

Cheers,
Alan

Well I have ordered 16 of them! What else can you buy for a tenner these days? Same seller as the Mashima 1015 clones that are somewhere between China and here at the moment.  Presumably production surplus from somewhere at that price - could be bad news if they are Farish production surplus...

[Bealman]

I'm following this with interest, cos I'm  from the old school of "you get wot you pay for" 

[belstone]

I'm following this with interest, cos I'm  from the old school of "you get wot you pay for" 

True, but Farish aren't making these motors in house.  They are buying them from one of the Chinese motor manufacturers.  The trick is to find out which one. 12 volt micro motors (8mm diameter or less) are pretty uncommon, as they don't have many applications apart from model railways. I'm not convinced by the 24 volt specs on these motors - it looks like they have just taken the 12 volt figures and doubled them, and on a motor this small, at 24 volts the life of the brushgear can probably be measured in minutes. It will probably take about a month for them to arrive, then I'll have a play with one, fit it to something (probably the poor old 2P) and report back.  They're cheap enough that I can pull one to bits and see what the bearings are like.

Richard

[trkilliman]

Interesting...this could open up a whole can of worms.

[Snowwolflair]

I'm following this with interest, cos I'm  from the old school of "you get wot you pay for" 

If that was the case our politicians would be polite kind geniuses. 

[Bealman]