I am thinking of replacing the alnico(?) magnet in an open frame Pitman motor with the newer rare earth type. Would any benefit be had (the motor currently runs very well ) and if I do so should I use a few large magnets or many smaller ones. Thanks to any repliers.
Bruce22,
You need to know what model # your Pittman motor is. The Magnets offered on this site will work with a lot of Pittman motors and they will improve performance:
http://www.micromark.com/super-magnets-20-pieces,9966.html
Take Care!
Frank
bruce22 Would any benefit be had (the motor currently runs very well ) and if I do so should I use a few large magnets or many smaller ones.
I've had good experience replacing the magnets, the current draw is significantly less and necessary to use the decoders.
when i looked for magnets at K&J Mabnetics, i couldn't find a single magnet of correct size and polarity. It shouldn't make a difference using multiple magnets and the micromark magnets correctly fit the motors in their photo and i assume others.
greg - Philadelphia & Reading / Reading
bruce22 I am thinking of replacing the alnico(?) magnet in an open frame Pitman motor with the newer rare earth type. Would any benefit be had (the motor currently runs very well ) and if I do so should I use a few large magnets or many smaller ones. Thanks to any repliers.
But this is a pretty good site for a complete discussion of these motors and magnets.
http://sumidacrossing.org/LayoutElectricity/ModelTrainPower/DCTrainMotors/
My brother-in-law, who has some locos with Pittman motors from way back when, tells me that the newer rare earth super magnets do indeed work but, as he says, why bother if the alnico magnets are still performing well. A few large or many small magnets shouldn't matter as long as you fill the available space.
Rich
Alton Junction
richhotrainMy brother-in-law, who has some locos with Pittman motors from way back when, tells me that the newer rare earth super magnets do indeed work but, as he says, why bother if the alnico magnets are still performing well.
There is one reason someone may want to go ahead and replace the magnets with rare earth magnets. The US government has discussed banning sales to consumers of rare earth magnets because of the danger they pose if swallowed by children. This issue has been riding for several years now, so don't know the current status. However, might be good to at least have the suitable rare earth magnets already in your spare parts box if you anticipate a future need.
Mike Lehman
Urbana, IL
I have done the magnet replacement on Pittman DC 70 motors on about 20 Hobbytown drives. I think it is a worthwhile effort. I got even better slow speed performance, better control throughout the speed range ,maybe a little higher top speed. I also got an average drop of about 2/10 of an amp current drop. Hobbytown drives are very good performers anyway but there was enough of an improvement to make it worthwhile. Since motors on Hobbytown drives are easily accessible it takes 20 to 30 minutes to do the replacement. I used K&J magnetics parts http://www.kjmagnetics.com/proddetail.asp?prod=B842-N52&cat=168 or http://www.kjmagnetics.com/proddetail.asp?prod=B842 I did not detect much difference between grade 42 and 52 although grade 52 is rated as stronger. Not much difference in price both are under a dollar each. I used a stack of 5 of these . Some of the motors are the replacements fot Pittman after Hobbytown could no longer get motors from Pittman. I found a stack of 5 worked well with some motors they fit well and some had an air gap. This gap has to be filled with metal. I found that if you broke worn out Xcto blades in half and use the end that mounts in the knife it worked well for a fit. It inportant not to leave an air gap between the pole pieces and the magnets,so I have read.
I think the effort was well worth the time and money as it was low cost and minimal time for the Hobbytown drives I am very happy with the results.
Ron High
Just a heads up about the new consumer safety rules that will likely take off the market most magents used for motor rebuilds: http://www.nytimes.com/2014/09/11/business/agency-to-consider-new-safety-rules-for-magnets-marketed-to-adults.html?hpw&rref=health&action=click&pgtype=Homepage&version=HpHedThumbWell&module=well-region®ion=bottom-well&WT.nav=bottom-well
Sounds like magnets will either be required to be large enough a child couldn't swallow them or, if smaller, such magnets will face a limit on their power to roughly 1/50th of the present supermagnets. Neither of those solutions would seem to support our hobby's use of the present available product to modify electric motors.
Obviously, this only affects the relatively small number of models that presently are produced with such old school technololgy, as well as previously produced open frame motors. Presumably, the use of such magents in motors for Priuses and, I presume, small electric motors that represent a packaged end product will be permitted to continue.