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Author Topic: Interchangeability of Grafar UK 3- and 5-pole motors  (Read 599 times)

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Offline Dr Al

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Re: Interchangeability of Grafar UK 3- and 5-pole motors
« Reply #15 on: March 15, 2019, 12:32:25 AM »
As an aside, and for reference and interest - all of Farish's new tool models have 3 pole can or coreless motors.

Cheers,
Alan
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If Dr Al is online he may be able to provide a more comprehensive answer.

“We have also arranged things so that almost no one understands science and technology. This is a prescription for disaster. We might get away with it for a while, but sooner or later this combustible mixture of ignorance and power is going to blow up in our faces.” – Dr. Carl Sagan

Offline V72

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Re: Interchangeability of Grafar UK 3- and 5-pole motors
« Reply #16 on: March 19, 2019, 12:11:15 AM »
I will measure performance of the 3-pole and compare with performance after change to 5-pole, knowing that I can always go back to the 3-pole. I'll  use the same grey white-spot magnet and the same brushes for these tests. Probably, next week will be the first opportunity.
I haven't opened up a canned coreless motor but assumed them to 5-pole. It's really an eye-opener, Alan, to learn that they are actually 3-pole, since their low voltage performance is really smooth.

Cheers, Steve

Offline Dr Al

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Re: Interchangeability of Grafar UK 3- and 5-pole motors
« Reply #17 on: March 19, 2019, 12:19:26 AM »
I haven't opened up a canned coreless motor but assumed them to 5-pole. It's really an eye-opener, Alan, to learn that they are actually 3-pole, since their low voltage performance is really smooth.

Precisely the result of being coreless, so no cogging between poles.

I tore a dead one down a while back, which is why I know:


The size of the coreless motor is such that it would simply be impracticable to wind five coils in it, and even more to produce a robust commutator at that size - it's notable how small motors are all 3 pole - the Farish armatures and the Mashima 1015 are some of the smallest 5 pole out there.

Cheers,
Alan
Quote from: Roy L S
If Dr Al is online he may be able to provide a more comprehensive answer.

“We have also arranged things so that almost no one understands science and technology. This is a prescription for disaster. We might get away with it for a while, but sooner or later this combustible mixture of ignorance and power is going to blow up in our faces.” – Dr. Carl Sagan

Offline V72

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Re: Interchangeability of Grafar UK 3- and 5-pole motors
« Reply #18 on: March 29, 2019, 06:15:24 PM »
I did the 3-pole to 5-pole conversion on Grafar Castle class of 1980s vintage with brass gears:
My benchmark was  my recorded performance of the current model  Tiverton Castle with a 6-coach train on a 1/100 gradient at maximum scale speed of 102 mph (incidentally  equalling Drysllyn Castle's April '58 record at Little Somerford on the Bristolian).
The 3-pole Winchester Castle achieved  an incredible 178 mph under the same conditions. On conversion to 5-pole,  the maximum speed  reduced to 112 mph and the very slow speed limit was reduced from 6V to 4V.
I'm happy with the result of the conversion and can live with it, but have to admit that the coreless motors achieve the supreme accolade for faultless performance across the full voltage range.

Cheers,

Steve

Offline Dr Al

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Re: Interchangeability of Grafar UK 3- and 5-pole motors
« Reply #19 on: March 30, 2019, 11:24:06 AM »
If you have no further use for the 3 pole armature, do let me know - these are always useful for repairs.

Cheers,
Alan
Quote from: Roy L S
If Dr Al is online he may be able to provide a more comprehensive answer.

“We have also arranged things so that almost no one understands science and technology. This is a prescription for disaster. We might get away with it for a while, but sooner or later this combustible mixture of ignorance and power is going to blow up in our faces.” – Dr. Carl Sagan

Offline V72

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Re: Interchangeability of Grafar UK 3- and 5-pole motors
« Reply #20 on: March 31, 2019, 12:35:43 AM »
Thanks for your offer Alan but I'll keep it for my own spares or possible future loco build projects.
Cheers,
Steve

Offline Dr Al

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Re: Interchangeability of Grafar UK 3- and 5-pole motors
« Reply #21 on: March 31, 2019, 07:09:02 PM »
Thanks for your offer Alan but I'll keep it for my own spares or possible future loco build projects.
Cheers,
Steve

Good good - I hate to hear folk throwing these things out!

Cheers,
Alan
Quote from: Roy L S
If Dr Al is online he may be able to provide a more comprehensive answer.

“We have also arranged things so that almost no one understands science and technology. This is a prescription for disaster. We might get away with it for a while, but sooner or later this combustible mixture of ignorance and power is going to blow up in our faces.” – Dr. Carl Sagan

Offline V72

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Re: Interchangeability of Grafar UK 3- and 5-pole motors
« Reply #22 on: April 18, 2019, 07:17:32 PM »
Just to follow-up on this topic, I have gained the impression that the 3-pole motors were more powerful than the 5-pole replacements. Also, the 3-pole motor runs smoothly at low speed and the only problem with these was they were always mated with brass drive gears ( so the brass worm and brass drive cog needed frequent lubrication).

 

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