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victor miranda

Posted - 2008 January 30 :  11:03:04 AM  Show Profile
Hi chris333,

I read your post a few times
and I think I got this.

There are three kind of contacts/brushes we often see in our motors.
The idea is some how electricity gets into the armature.

one is a brush in a barrel with a spring pushing it.
most n-scale motors are like this.

There is another kind of contact where
a thin strip rides against the commutator
the thin strip is also lightly loaded(sprung)to the commutator.
I call it finger style, the finger-tips are on the commutator.

and the last kind is the same as the finger style.
except that there is a block of brush material
soldered to the finger tips.
The same kind of brush material as the barrel style.

I am pretty sure this last one is what you have in your mashima motor.
I want you to know this is an agreement with you,
I want to make sure.

I happen to believe the brush-blocks on the finger tips is how the current rating is raised.
The fine tips in the small motors get eroded by the electrical arcing.

I have seen blocks soldered to those fingers
and I think that is all that is needed to get some longevity.

I think Max's last attempt would have been good
if there had been a brush-block in place.

v









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mmagliaro

Posted - 2008 January 30 :  2:44:00 PM  Show Profile  Visit mmagliaro's Homepage
To clarify, the two motors I disassembled have (or HAD) finger wipers.
The end of each wiper, where it rides on the commutator, is split into three
fingers (presumably to give it more flexibility at the contact point, and
more reliable contact without excessive pressure on the commutator).
Onto those 3 fingers is a block of silver/whitish looking material,
which looks like the material that actually rides on the commutator.

In both cases, virtually all the block material was gone from both
brushses. One wiper was fairly intact (still had its fingers left) and the other had its 3 fingers
burned back to the "nubs" (the place where the wiper splits into 3).

There were 3 rather distinct grooves burned into the commutator where the fingers
were. It's safe to assume that all the block material wore/burned off,
and then the metal fingers started riding directly on the commutator, wearing
the death out of it and burning the grooves.

-----
In contrast, the Kato motor has the nice carbon slugs spring loaded in a holder.
I admit that "nice" is a personal viewpoint, but it's hard to argue with a motor that has run for over 20 years. :-).


-- Max

N Scale steam for the masses

Country: USA | Posts: 3890 Go to Top of Page

Rob de rebel

Posted - 2008 January 30 :  9:46:54 PM  Show Profile
If you notice carbon, gold, silver, soft metals in general are used as motor brush materials. Carbon being the cheapest.

Rob


Rob de rebel
Prototrack,
rdressel@gci.net

Country: USA | Posts: 5025 Go to Top of Page

alhoop

Posted - 2008 January 30 :  10:29:23 PM  Show Profile
Some info from MicroMo Electronics website on coreless motors with precious metal commutation:

"The performance lifetime of coreless DC motors depends on:

Operating point - torque, load, and speed
Operating conditions - duty cycle
Ambient conditions - environment, shock, and vibration
Method of integration into other systems - ie. how is the DC motor mounted into the system

It is advisable that the current under load in continuous operation should not be higher than one-third of the stall current.
The motor develops its maximum power P2MAX, at exactly half the stall toruqe MH which also corresponds to half the speed. For reasons of life performance, this working point should only be selected for intermittent periods. For exceptional long life performance, brushless DC motors are available.

On the average, lifetime of up to 1,000 hours for precious metal brushes, and more than 3,000 hours for graphite metal brushes can be expected when the motors are operated within recommended values indicated on the data sheets.
"

Duty cycle and intermittent periods. Lifetime up to 1000hrs.
I wonder if this means that they are not rated for continous operation.


Al

Edited by - alhoop on 2008 January 30 10:59:29 PM

Country: USA | Posts: 849 Go to Top of Page

mmagliaro

Posted - 2008 January 30 :  11:24:11 PM  Show Profile  Visit mmagliaro's Homepage
Well, they may not be rated for continuous operation, but they sure can take it as bad
as I can dish it out to them. I've run those MicroMo (Faulhaber) coreless motors
for many overnight torture runs, and I've run their 6v motors at 9 to 10 v for hours
and hours and they still hold up. They must be made of kryptonite. They list
the max operating current (not the stall current) for the 6v motor 1016 at about 170ma,
and even at 10v, it only draws 80-100ma.

Whatever I do with this, I want to end up with something you could plunk on an NTrak layout
at a show, for example, and just let it run all day and not worry that it would fry.



-- Max

N Scale steam for the masses

Country: USA | Posts: 3890 Go to Top of Page

up1950s

Posted - 2008 January 31 :  12:02:59 AM  Show Profile
quote:
Originally posted by mmagliaro

Well, they may not be rated for continuous operation, but they sure can take it as bad
as I can dish it out to them. I've run those MicroMo (Faulhaber) coreless motors
for many overnight torture runs, and I've run their 6v motors at 9 to 10 v for hours
and hours and they still hold up. They must be made of kryptonite. They list
the max operating current (not the stall current) for the 6v motor 1016 at about 170ma,
and even at 10v, it only draws 80-100ma.

Whatever I do with this, I want to end up with something you could plunk on an NTrak layout
at a show, for example, and just let it run all day and not worry that it would fry.





That would be wonderful , keep us posted please .


Richie Dost Photos http://picasaweb.google.com/up1950s


Country: | Posts: 10219 Go to Top of Page

Caddy58

Posted - 2008 February 01 :  04:47:14 AM  Show Profile
Very interesting read.

For what it is worth an electronics superstore in Germany (Conrad) has 45 different gearhead motors in their program. Most are far too big for our use, but some are actually quite small and rated at 12V

http://www.conrad.de

Enter the following text string in the search field (called "Schnellsuche") to the left:

"modell-getriebemotoren"


Cheers
Dirk



Edited by - Caddy58 on 2008 February 01 04:58:13 AM

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mmagliaro

Posted - 2008 February 05 :  10:52:03 PM  Show Profile  Visit mmagliaro's Homepage
Hello, everyone. The latest incarnation is under test.
5:1 plastic Gizmoszone/TinyTot gearhead mated to a Mashima 10x12x15 5-pole motor.
The assembly went as follows:

Grind down, shorten, and flat the 1.5mm shaft so it is a 1.0mm half-round. Believe it or not,
this is not too hard to do with a Dremel cutoff disk and a caliper to make sure you
get the diameter right. Just run the motor while you do the grinding and you can keep the shaft
true.



A simple washer glued on the motor front around the bearing as a spacer so the gearhead has something
flat to rest on.


Now, glue the motor onto the washer/motor front (with ACC backed up with epoxy). Then, glue
the whole thing into the frame with some Walthers Goo. As before, you can snake the flexible
tube in over the worm shaft and nurse it into position through the frame access holes
in the sides without having to take the frame halves apart.


Since the motor/gearhead is 10g lighter than the original motor, I added all those tungsten
disks to get some of that back.

Motor performance:
Free running in my hand: max current 40 ma.
Free running with gearhead added: 50 ma.

Mashima spec nominal current: 70ma.

I inquired about maximum limits and Mr. Mashima replied (yes, there is a Mr. Mashima,
and he was very helpful and answered me --- pretty cool, eh?)
He conducted some tests and estimates the maximum current limit to be about 200 ma for this motor.

On the track, pulling a train, it hits a maximum of 70ma at 12v. So I am only at about 1/3 the
max current limit. This should be quite safe, but time will tell.
Right now, it is undergoing the usual overnight "sink or swim" test. I am running it at 10 volts.


Performance: Min start/run speed 1.7mph. And it's a darn GOOD 1.7 mph. Best I've seen yet.
Max speed at 12v is 16 mph. That's a little slower than I'd like. I was hoping for 25.
But 16 ain't bad. It's way better than 9!

Here's some video:
http://www.youtube.com/watch?v=jp_aeQ3z8I4

Everybody keep their collective fingers crossed! I hope I wake up tomorrow morning to
find it still purring around the layout.


-- Max

N Scale steam for the masses

Country: USA | Posts: 3890 Go to Top of Page

up1950s

Posted - 2008 February 05 :  11:25:52 PM  Show Profile
Well ain't that the cats meow .

Richie Dost Photos http://picasaweb.google.com/up1950s


Country: | Posts: 10219 Go to Top of Page

Chris333

Posted - 2008 February 05 :  11:44:56 PM  Show Profile
I hope she is still running...then I can finally put mine together.



http://www.trainboard.com/railimages/showgallery.php?cat=500&ppuser=3174
http://picasaweb.google.com/ErieChris333
http://www.youtube.com/user/Schmuck804
http://community.webshots.com/user/chris333333

Country: | Posts: 3958 Go to Top of Page

mmagliaro

Posted - 2008 February 06 :  11:26:57 AM  Show Profile  Visit mmagliaro's Homepage
12 hours - still goin' strong! Removing it from the track, I can put my
finger on the back of the motor at the rear of the cab,
and it ain't even WARM. This is a very good sign. Current draw is
still about 70-75 ma.

By comparison, the Nigel Lawton 12v coreless motor burned up running at only
7.5v (80 ma). So I think this clearly proves that the motor failures
are caused by the inherent design of those cheaper motors - they simply don't
have brushes that are very durable. Even if they aren't overloaded, they
just wear out fast. And if they are pushed hard, forget it - they burn up
in just a few hours.

The Mashima is running even better than it
did last night when I made the video. (As an aside - this is the first
Mashima I've ever used. I am impressed. This little bugger is a nice
motor! It reminds me a lot of the better 12mm Sagami cans from days of old.)

When I did the video,
it would start and run at about 5 volts, and that was good enough
to run under 2 mph. NOW, it will start and run at 4.25v and can creep
noticeably better. I'll measure the low-end speed again tonight.

It's back on the rails, runnin' at 10v, whilst I am at work typing this.
By tonight, it'll have another 10 hours under its belt. But I am
really hopeful about this one.

The trick on grinding that shaft:
1. Gently clamp the motor down (one of those hand-squeeze grippy clamps works well).
2. Clip on some clip leads and run it at medium speed.
3. Put a cutoff disk in your Dremel, and turn the Dremel on.
4. Swipe pass after pass of the disk against the turning shaft,
check it often with a caliper until you get close to 1.0 mm.
5. Then just hold the disk in your hand, laying it flat against the rotating
motor shaft, to get it down the rest of the way. The sheer fact that
the shaft is spinning, and the motor is clamped down, will act almost
like a lathe. The shaft will turn down nice and even.

6. Finally, use the dremel with the cutoff to grind a flat on one side of the shaft.
I did this totally by eyeball. It's not critical. Just keep taking some off,
and seeing if it will slip into the gearhead.

This whole job, start to finish, took about 90 minutes.
(Shell off, motor out, cut shaft, grind shaft, flat shaft, glue gearhead
on, install motor, solder leads, shell back on.... )
Of course, admittedly, I have a lot of practice with this one now. :-)


-- Max

N Scale steam for the masses

Country: USA | Posts: 3890 Go to Top of Page

up1950s

Posted - 2008 February 06 :  5:24:11 PM  Show Profile
Well if it ran all night and didn't get warm then its a winner in my book .

So I went to order a pair of them and there is only a eMail and fax . How does he accept payment ? I get weirded out by hard to buy stuff . What hoops are required to jump through to get his stuff in the mail ?


Richie Dost Photos http://picasaweb.google.com/up1950s


Edited by - up1950s on 2008 February 06 5:46:08 PM

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mmagliaro

Posted - 2008 February 06 :  8:28:51 PM  Show Profile  Visit mmagliaro's Homepage
I'm not clear on who you are talking about, Richie. Eldon? (motorman)
If so, the only way I have ever bought from him is to send him an email asking for
what I want (in this case, the Mashima 10x12x15) and a price. He replies telling me
the total, and I PayPal that amount to him (ask for his PayPal address too, so you'll
be sure he sends it.)

I have had something like 5-6 transactions with him, and he has always reliably delivered.

Update: We're now at 24 hours. Still runnin' fine. And the motor is really hitting its stride now.
It's down a full volt on starting (4v vs 5v last night). It starts and runs very reliably with a string of
9 cars at 1.3 mph. Top speed still 16 mph. Current draw still 75 ma.

Onward!

And Richie: don't forget, you do have to grind down and flat the mashima shaft to go in that gearhead.
But it wasn't all that bad with a Dremel/cutoff disk.




-- Max

N Scale steam for the masses

Country: USA | Posts: 3890 Go to Top of Page

up1950s

Posted - 2008 February 06 :  8:47:03 PM  Show Profile
So we don't go to Mashima directly like I did via eMail ?

We get the Mashima 10x12x15 that Mashima calls the MHK-1015 from the Motorman ?

EDIT ... Ok I sent Motorman an eMail also .


Richie Dost Photos http://picasaweb.google.com/up1950s


Edited by - up1950s on 2008 February 06 9:27:56 PM

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mmagliaro

Posted - 2008 February 06 :  11:38:42 PM  Show Profile  Visit mmagliaro's Homepage
I didn't know you could buy from Mashima directly. I found them at Micro-Loco-Motion,
so I bought mine there. There are a few other places on the web, like hollywoodfoundry.com,
that also advertise them.


-- Max

N Scale steam for the masses

Country: USA | Posts: 3890 Go to Top of Page
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