Pitman magnet swap question ?


T.C.

T.C.

Active Member
For starters I only have and run DC and I have no plans to get into DCC.
That being said I am thinking of changing out the magnets in my Pitman motors as I have read they would perform much better if I did the swap.
I see that I can buy magnets that I would stack 4 to make one magnet.
My question is why not just use one magnet ?
Like the one in this link http://www.kjmagnetics.com/proddetail.asp?prod=B848
This company also has the others that could be stacked http://www.kjmagnetics.com/proddetail.asp?prod=B842-N52
Has anyone tried the single magnet type ?
Any advise or comment would be appreciated.
Thanks T.C.
 
There is no reason you can't use a single magnet IF 1) you can find one in the correct size AND 2) with the correct magnetic orientation.
 
Thanks for the reply Kevin
The first link in my post is to a single type magnet the correct size with the poles in the correct position
The second link is to magnets that are the same as Micro Mark where you stack four together to make one, also with the correct pole orientation.
The one piece would be easier to work with and the cost is much less.
I was just wondering if anyone had done this, before I go experimenting.
Thanks T.C.
 
Last edited by a moderator:
T.C. said:
I am thinking of changing out the magnets in my Pitman motors as I have read they would perform much better if I did the swap.
Click to expand...

My question is why not just use one magnet ?
Click to expand...
If one can find an exact fit, I don't know why stacking would be needed. What are the dimensions of the existing one in the Pittman? Is the Pitman's magnet only 1/2" tall.

Your original statement above is another answer. It will be a much stronger magnet and perform much better when stacked. Look at the difference in the Gauss ratings between the two examples you gave. Why go to all the trouble of swapping magnets; if, in the swap, one does not maximize the situation? On the other hand, these look like very strong magnets. Is it possible to get them too strong? I don't know.

If no exact match size wise or stacking, what material will be used to fill any gaps? Will need shims of soft iron.

Has anyone tried the single magnet type ?
Click to expand...
Sorry, I have never replaced the magnet in any of my motors.
 
Thanks for the reply
Both company's give pull force readings Micro Mark is aprox.6.5 lb. ea., the KJ is 5.94 lbs. ea. the larger KJ mag is 10.5 lbs.
I don't know if you would add them together though like 6.5x4= 26 lbs ? or will you still end up with 6.5, or is it split north to south @7 ea. way ?
Also the larger mag. is the same amount of material as the four stacked mags. but I realize that doesn't mean it has the same power.
As for gaps or to install you can use JB Weld as it contains metal and will fill any gaps, we used it all the time when we built high end slotcar motors for dragracing.
T.C.
 
I don't understand the "pull force" measure. I was looking at the Gauss numbers. Never done any real engineering with magnets, but I just glanced at the formulas, looks like with similar compound magnets that mass is the key. So total size (mass) is the determining factor whether it be from a single unit mass or the mass of several stacked together. The stacked are going to have slightly less since there is a "space" however small between the two (and that I do know - magnetic strength is exponentially weaker with distance).

I think I would just go with the one. Thinking of Pittmans, I thought I remembered their magnets were bigger more like a 1/2" cube.
 
Honestly I haven't taken one apart lately, but if I remember they have a slot down the center of the magnet to accommodate the bar or screw that holds them together.
But if you did get a 1/2" cube the bar/screw could be cut away and the new magnet glued in it's place and hold the metal parts together.
As for the size I looked for a size that totaled what Micro Mark magnets totaled overall in size.
I would think that as many different sizes this KJ company have they probably have a 1/2" cube, but on the other hand maybe MM researched it and a 1/2" cube is to much ?
I do know that mega magnets will cause your motor to draw mega amps on startup, we had slotcar motors that would draw well over 225A at startup, but they were only made to run 87.5 ft. at a time, so in this case more may not be better.
T.C.
 
Just to let you know, for other, non-model railroad, uses, I have ordered many, many magnets from KJ. They always promptly delivery a quality product. (No relationship - just a happy customer.)
 
Thanks Kevin, that's good to know
Looking through there list I did find a cube 1/2"X 1/2"magnet with a hole that could be used for the pin to go through making mounting much easier.
I will eventually try some of these and will post my results.
T.C.
 
Brakeman:

Instead on replacement magnets, have you considered replacing the entire motor with a new and improved replacement?

Just a thought
 
Yes I have and I have replaced a few. The thing is that with DC the low draw can motors seem to jack rabbit sometimes, probably due to my Old style MRC taper wound ceramic resistor rheostats.
My throttles seem to be matched more toward the pitman type motors, I have one that has HO windings and the other has N gauge windings, no transistors .
They are both tethered to the control panels using 4 wire Mic cord and a plug with a threaded connection. Simple and it works really well but there is always room for improvement.
Also a quality can motor is very expensive and Im not sure they pull any better than a good ole Pitman ?
T.C.
 
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