64 replies to this topic

[Martin]

I am about to take this motor apart and see why it does not run. I will give it a good clean and fresh brushes and see what I get.

 

I have said this before, I am not a motor builder. But i would like to get this up and running for a future project.

 

Any advice would be appreciated.

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[Bill from NH]

If you pull the pintabs while cleaning, also re-true the comm. It might need new brush springs too.

[havlicek]

     I'm happy to see someone pulling a motor apart who doesn't feel all that comfortable doing so.  These things are basically very simple, so taking it apart can lead to some really good confidence-building.  You can look at a few things:

1)Assuming the motor isn't shorted-out (on a power supply, this would result in current draw and heat, but *could* result in no spinning), or completely "dead"...meaning no reaction at all after power is applied, you're right to look at brushes.  I've seen them worn to little nubs...so short that they no longer even make contact with the com.  You *could* just replace the brushes before digging-in deeper, just as a first test.  BTW, a short could be caused by the end bell hardware and bits of wire or whatnot...it *could* even be caused by the bushing strap on your motor shorting on the inside against the top of the com, but these motors used a com that has a non-conducting "cap" of black phenolic.  This would only be possible if the arm wasn't original, not likely in your case.

2)While replacing the brushes, don't assume the motor is dead if the new ones don't cure the problem.  The new brushes *could* still not be making contact with the com if they're "hung-up" on some obstruction.  After removing both of the old brushes, you should be able to spin the arm with your fingers.  The magnets alone will offer some "resistance" or "cog", but not all that much on this type motor.  Immediately after installing only one brush, you'll notice the arm doesn't spin so easily.  That tells you the brush is contacting the com and causing drag...a good thing.  After installing the second brush, that drag should become more noticeable...another good thing.  ***Still, with the new brushes installed and the motor hooked up to a power supply at low voltage, try pressing-in on the back of each brush with a toothpick to overcome any possible obstruction preventing *full* brush contact.  The motor may jump to life...or not.  In either case, you still want to move to the next step.

3)Remove the brushes and then the pintabs (*I feel your pain), and pull the end bell free from the can.  This can be difficult on some of the Muras, so holding the end bell "tower" firmly, try rocking it up and down to loosen it.  You should be able to pull the armature out from the can and end bell now.  If there was solder on the armature shaft, you'll have to clean that off BEFORE removing the arm so the shaft can slide out past the bushing.  There will most likely be a lot of "gunk" inside both the can and the end bell.  That stuff is a combination of the dust from worn brushes, old oil and whatever else got sucked up into the motor over the course of the last fifty or so years.  ***Be on the lookout for screws, pintabs and even parts of straightpins...whatever is magnetic could easily have found it's way in there and cause either a physical block to thew arm spinning, or a short...or even damage to the arm's coils.  The whole inside of the motor should be thoroughly cleaned...and that includes removing the magnets.  Denatured alcohol is a good solvent for this, and is relatively "safe" (*although it is flammable)...being basically the same stuff people drink *ALTHOUGH WITH AN ADDED POISON...SO DON"T DRINK IT!  Any solvent might harm the paint and/or decals, so be careful with those.

4)Time to look at the armature.  The arm CAN be cleaned with alcohol and a clean cotton rag, so you can see better what's going on, but usually the most gunk will be up around the com...and paradoxically...that's the last place you'd want the stuff.  Anyway, look at the whole armature...the coils and the com.  Any damage to the coils or the com could be the culprit.  For example, sometimes people will use screws that are too long to mount the motor, and as soon as you spin the motor, they wreck the arm (*usually back at the can end).  Look closely at the commutator and especially the little tabs where the magnet wire is connected to the com.  If any of the com segments seem "different" (*loose, cocked whatever), that's a major no bueno.  If the wires at the com tabs are broken...same thing.  Also look at the "gaps" or cuts on the com between segments, if they're full of gunk that can hamper performance and needs to be addressed...but it almost never completely stops a motor from spinning.  Lastly, look to see that the color of the three armature coils' wire is the same.  If one or two look noticeably darker, the arm is most likely toast from an internal short.  There's plenty of current at most commercial tracks to cook the insulation when a short happens.

5)Time to meter the armature, and a cradle is the easiest way to do this, but not necessary.  You first need to clean the com though.  A "0000" (super fine) Scotchbrite pad (available at most decent hardware stores) is a good way to do this.  Twirl the arm with one hand while pinching the com with the Scotchbrite only until the three com segments are all fairly clean.  This won't ruin the com, especially if you're going to have it cut afterwards (*a good idea if all the above works out in finding the problem), but it will make resistance readings easier and more informative.  Set a multimeter to the lowest resistance scale and touch the two probes to adjacent com segments, noting the meter reading.  You should get at least similar readings after doing this three times to read all three poles.  If the readings are a little off...no biggie.  If they are significantly off or way off, you may have an "internal" problem...armature coils can fail "on the inside".

I can't think of anything else offhand that might cause a motor to not function at all...as opposed to functioning, but poorly.  Of course, I could be forgetting something.

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There's some details to take care of during reassembly I haven't mentioned.  The above is *just* for trying to figure out what might be wrong.

[Martin]

Great guidance John, thank you Bill too.

 

I carefully pulled the pin-tabs with a pull and twist. A lot of gunk and the old brushes were jammed and ugly. They actually looked split?

 

I wanted to clean the comm and put new brushes and springs in to see if would run.

 

It runs, It actually sounds good so I will continue to dissemble. 

 

The end bell bearing is worn and too loose so I will need to replace that,

 

Did this motor have shunted brushes?

 

The brush holders are soldered to there base. That's not stock, is it?

 

I did put a caliper on the comm and found the low spot to be .004'' low. it looked worse to the eye to me. But I think this will take a cut. Other that that it looks solid to me.

 

Is this a hard end bell to find? This one has been filed under the brush holders and has a nasty crack were it was weakened.

 

The can bushing has been filed on one side for chassis clearance at some point but does not feel lose, so it is functional.

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[old & gray]

What John said.

 

I started tearing down and rebuilding motors since I was 14, but then I started with HO T-Jet cars which were nothing but motor.

 

Comments I would add:

 

Make sure the arm turns over by hand without a "dragging" or scraping sound.

 

Look at the armature through the case holes to see if there are any marks on the OD which would indicate rubbing or rust build up.

 

I do not remember a brass mounting plate on the endbell (see picture from LASCAM). This maybe a reason for binding if it is out of alignment.

 

Pulling the pin tabs is a pain. You probably want to do this just to clean the accumulated gunk out. I found the best tool for this is a pair of nail clippers which grip the head of the pin; then pull and twist CCW to remove.

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[havlicek]

 

 

I did put a caliper on the comm and found the low spot to be .004'' low. it looked worse to the eye to me. But I think this will take a cut. Other that that it looks solid to me.

 

It's fine and could probably take more than one cut.  The shell material on these coms is fairly thick, so there's plenty of "meat" left.

 

 

 

The end bell bearing is worn and too loose so I will need to replace that,

 

The looseness is probably why the endbell bushing strap was added.  These bushings were MUCH better than the Mabuchis, but they are often heavily worn.  Not an easy thing to find NOS, but maybe.  Even if you do find one (*or can have one made), you will still need to address installing it solidly.  A loose fit will only make the replacement wear very quickly and lead to more/faster com wear and tear.

 

 

 

Is this a hard end bell to find? This one has been filed under the brush holders and has a nasty crack were it was weakened.

 

 

They are very difficult to find either NOS or even in good condition used.  The crack in that particular location (*if it's only under the brush holders) should not affect anything much...if at all.  The much more important detail to take care of is the end bell bushing and it's loose fit.

[Pablo]

I have a flower sticker if you need one

[Jairus]

This is the second gen Cukras 16D Mura sold.  The differences between the two are exterior paint and the tied com wires.  Other than that, they are the same as any other Mura motor.
Some of these also had black endbells. If you are looking for parts click below.

Ebay auction closes in 2 hours...
https://www.ebay.com...slot-car-motors

 

[MSwiss]

I do not remember a brass mounting plate on the endbell (see picture from LASCAM).

Me either.

 

Something the original owner added when the oilite spun or melted in the plastic?

[havlicek]

This is the second gen Cukras 16D Mura sold.  The differences between the two are exterior paint and the tied com wires.  Other than that, they are the same as any other Mura motor.
Some of these also had black endbells. If you are looking for parts click below.

Ebay auction closes in 2 hours...
https://www.ebay.com...slot-car-motors

 

 

 

I would just caution that the auction doesn't show any detail as to the end bells...either purposely or not.  Aside from abuse, the cans are basically "forever", it's the end bell that's most often toasted, especially on end bell drive motors.

[mark1]

I like the patina on that one. 

[dc-65x]

The end bell has been modified with a Champion hop up kit. The only Mura thing left is the end bell itself and it has been cut up to accept the kit components. A new stock Mura white end bell could be installed to put it back to stock. Or the modified components left in place to show period "updates".

 

[Martin]

The end bell has been modified with a Champion hop up kit. The only Mura thing left is the end bell itself and it has been cut up to accept the kit components. A new stock Mura white end bell could be installed to put it back to stock. Or the modified components left in place to show period "updates".

 

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Thanks for all the input guys. Thanks for the sticker offer Paul. The stickers are in good shape on this can. If I repaint the can I think the safest way would be to mask of the original stickers and sand and paint around these.

Rick did you ever find a pink rattle can that you were happy with?

 

Got to think about this choice Rick.  Would it be best to build back stock or as modified.?  Open to consensus.

[Bill from NH]

Martin, it depends what you plan to do with it. If you want it to be a collectible motor, build it back to stock. If you just plan to use it to power a car after the rebuild, go the modified route, unless the car too is highly collectible.

[Pablo]

If it was mine, I'd:

-take the time to find an original Mura white endbell with Mura hardware

-check the arm shaft for straightness, then send it to a refurbisher for cleaning, a comm cut and dynamic re-balance

-also send in the can to have the magnets re-zapped (in the can)

-leave the can paint and stickers alone

-do NOT re-install the EB gizmo

-use brass post protectors, not chrome

-new-pre-radiused brushes, new springs

-I hate to say it, but I'd use the dammits to secure the new EB.

 

Make yourself a gizmo so the can won't get nicked when you hammer them in gently with a small brass hammer.

Maybe a piece of .032 brass sheet with a hole drilled slightly larger than the dammit.

 

Now that you have the arm out, what is the OD, and what is the ID of the magnet hole?

I'd recommend an airgap on that motor of between 10 and 15 thou per side.

In other words, let's say the arm is .513, the hole should be between .533 and .543

 

If you absolutely cannot find the proper Mura EB, a Tradeship would be perfectly acceptable as a substitute.

Approved by the Vintage Police, Electric Dreams still sells them at $25

[old & gray]

This is the second gen Cukras 16D Mura sold.  The differences between the two are exterior paint and the tied com wires.  Other than that, they are the same as any other Mura motor.
Some of these also had black endbells. If you are looking for parts click below.

Ebay auction closes in 2 hours...
https://www.ebay.com...slot-car-motors

 

Wowdid the bidding on this sky rocket in the last bit.

[Bill from NH]

The price doubled in the last 2 hours. $25 of that was someone's underfunded bid stealing attempt with 6 seconds left.

[Martin]

I checked the auction about a hour after Jairus brought to our attention and at that point it was already more than I wanted to spend. But thanks J for the heads up.

 

Paul, I will look and see what parts I can put together to make it stock. If I fall short it goes back together as built  "to show period updates". and I will use in a period build in the future.

On the dammit installer. Have you tried taking an old screwdriver and cutting off the blade then making a small cup shape in the cut end to match the dome of the dammit's. If there is enough friction between dome and tool it should allow a twist and push motion

 

knowing what you all know now, what do you think its value is?. I ask because I got this motor with an agreement to pay for it once I knew what I had. I knew it would have issues and could not offer a price until I could sort good from bad and estimate what it would cost to rebuild. Any help on value would be appreciated.

[Maximo]

That rusty Flower Power Cukras motor looks like it powered the Yellow Submarine!

 

 

maxiMo

[Martin]

It is a Crusty Cukras for sure, that would have been a good topic title.

 

What do think I should pay?

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[Pablo]

Impossible to guess the value, depends on the type and quality of the magnets, if the arm shaft is straight, and if the arm is serviceable. What you have is a motor that was modified, rode hard and put away wet.

The most valuable part of it may actually be the pink original paint and stickers.

 

Again, it depends on how well the arm cleans up. It may be a real sweet arm, or it may be gone.

My best guess is, IF the arm is still good, and IF mags are good, it's worth about $25

[Martin]

Thanks Pablo for your opinion. I just ordered a comm cutter (thanks John) so I can get a bit more involved with motor restoring. I did throw it together and it sounds good. So with a little more set up it should be a good motor.

 

Looking for a static balancer now. I know its not as good as dynamic balancing, I just want to check arms in house.

[proptop]

Mid America raceway has replacement Champion endbell hardware, like yours has...and I think Professor Motor might still have some in stock too? That would take care of your endbell bushing issue anyway, if you can't find a suitable Mura replacement endbell.

You won't be able to use an original Mura / Mabuchi style bushing because some material has been removed to install the Champion strap/bushing assy.

 

Getting the "Semi-Can" or can in a can magnet shim and magnets out, for through cleaning, will probably be a struggle, what with the rust and all..

 

If it were me, I would leave the "patina" as is because they're only original once, and the real value is in the Cukras sticker, and secondarily the flower power sticker...and of course, what's left of the original paint.

 

I agree with everything everyone else has said above, except maybe I'd value it as is a bit more $.

 

The magnets should be the original ones, because of the shim, but with a modified motor, and the passage of time, ya never know...

 

Maybe you could post a pic of the inside of the can so we can see if the mags are original?

[havlicek]

 

 

Looking for a static balancer now. I know its not as good as dynamic balancing, I just want to check arms in house.

 

See if you can get in touch with Rick ("Rgeo") about one of his static balancing jigs.  A couple of single edge razors later, you'll be in business.  Set it up level in both directions for whatever table you would be using it on and check before every use.  A simple and inexpensive string level will get you there by placing it across the two blades in one direction, for balancing in the other direction, just carefully place a suitably-sized piece of metal that is flat across the blades and then set the level on top of that perpendicular to the first direction.

* Warning strong opinion: Don't bother with the magnetic type balancers, they are basically useless.

[Martin]

Thanks John, does Rick ("Rgeo") post here on SB? could not find him with a google seach.

 

Made some progress today and found what I think are all stock parts? Looking forward to cutting the comm and firing this baby.

 

I took the Professor motor post protectors and turned most of the flange and chrome off so they look like Mura parts.

 

Also made that push tool for the "damits" although I may use the little screws I have and paint them silver.

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