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Discussion Starter · #1 ·
Being a newbie to the hobby I thought I would reach out to the forum with the symptoms of a motor problem. Someone may know the answer or possible answers.
The car is a 1/32 revell corvette stingray '64.
On track for the first time after a rebuild the car runs noisily and slow. However it occasionally picks up and goes like a rocket!
I have taken the body off and with the braids touching the track, with the rear wheels lifted off the track, the motor runs perfectly smooth, fast, quietly and free spinning, perfect.
But under torque load as a rolling chassis - ie on the track with body off - something is happening with the motor.
I have never stripped a motor down, do they have internal bearings, thrust washers etc? Do they wear so that the shaft can have play in it?
Any thoughts would be helpful
Thanks
 

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Hi Ian,
Hard to tell without seeing it, but those symptoms sound like a bad connection somewhere.
These motors were cheaply made, and there's naturally a lot of play in the armature - plain oilite bearings, including a blind one on the can end and regular fiber or metal washers.
These are pretty easy to strip down, the only danger is breaking off the tabs that hold the endbell on. They can survive a bend or two, but no more in general, so depends if the motor looks like it's opened before.

First, remove the pinion (hopefully with a pinion puller), then springs and brushes - you might have to encourage the brushes by using an X-acto blade as a lever (hanging brushes might explain some of those symptoms, so remove and clean/lightly sand brushes, to make sure they slide easily in the endbell - if they stick, try putting them back in and test before disassembling motor). Use something like a pointed small punch to start unbending the tab, then finish with needle-nose pliers. If there are ridges on the shaft, file those off before removing the end bell (and if you think of it earlier, run the motor on low power and hold a file against the shaft to remove ridges).

Take apart the motor and clean it out; I usually wash out the endbell with lighter fluid and an old toothbrush; check that brush hoods are straight and allow the brushes to slide easily, while also keeping play to a minimum. They're riveted in, so you don't have much leeway there. The magnets are held in by bend-down tabs on the motor and a spring on the other end - check these to make sure they're evenly installed and the arm doesn't rub anywhere. The big speed secret at the time was to put a layer or two of masking tape on the backs of the magnets to move them closer in; this was later derided, with experts saying you didn't want to break the magnetic continuity, so use metal ships (old beer cans, when they were of steel, then bespoke parts).

Reassemble, using extra shims to remove excess play from the arm - while also keeping it centered in the magnetic field as much as possible. Bend the brushes out to about a 60° angle, instead of the usual 45° to give a little extra pressure - usually useful on these motors with not quite round commutators.

If a disaster occurs, I've got extra Revell motors! And let us know how it goes.

Don

PS: just saw you're last post, arghh..... So what was the error? Don't worry, we've all had a little too much wine on occasion.
 

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Hard to tell, but it may very well be the wiring or the pick up braids rather than the motor itself. Check first for a broken lead wire making occasional contact depending on the position of the guide, or a a dirty or misplaced braid, as this is far easier than stripping the motor. .

Good luck with it,
Eduardo
 

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Discussion Starter · #5 ·
Hi Ian,
Hard to tell without seeing it, but those symptoms sound like a bad connection somewhere.
These motors were cheaply made, and there's naturally a lot of play in the armature - plain oilite bearings, including a blind one on the can end and regular fiber or metal washers.
These are pretty easy to strip down, the only danger is breaking off the tabs that hold the endbell on. They can survive a bend or two, but no more in general, so depends if the motor looks like it's opened before.

First, remove the pinion (hopefully with a pinion puller), then springs and brushes - you might have to encourage the brushes by using an X-acto blade as a lever (hanging brushes might explain some of those symptoms, so remove and clean/lightly sand brushes, to make sure they slide easily in the endbell - if they stick, try putting them back in and test before disassembling motor). Use something like a pointed small punch to start unbending the tab, then finish with needle-nose pliers. If there are ridges on the shaft, file those off before removing the end bell (and if you think of it earlier, run the motor on low power and hold a file against the shaft to remove ridges).

Take apart the motor and clean it out; I usually wash out the endbell with lighter fluid and an old toothbrush; check that brush hoods are straight and allow the brushes to slide easily, while also keeping play to a minimum. They're riveted in, so you don't have much leeway there. The magnets are held in by bend-down tabs on the motor and a spring on the other end - check these to make sure they're evenly installed and the arm doesn't rub anywhere. The big speed secret at the time was to put a layer or two of masking tape on the backs of the magnets to move them closer in; this was later derided, with experts saying you didn't want to break the magnetic continuity, so use metal ships (old beer cans, when they were of steel, then bespoke parts).

Reassemble, using extra shims to remove excess play from the arm - while also keeping it centered in the magnetic field as much as possible. Bend the brushes out to about a 60° angle, instead of the usual 45° to give a little extra pressure - usually useful on these motors with not quite round commutators.

If a disaster occurs, I've got extra Revell motors! And let us know how it goes.

Don

PS: just saw you're last post, arghh..... So what was the error? Don't worry, we've all had a little too much wine on occasion.
Thank you Don. I am going to strip down a spare old motor just to see how it all works so your comments are not wasted.
I had put the two chassis crossmembers in upside down - tricky to see with wine onboard!. Also I reversed the spur gear as this was on the wrong way around according to images of other similar cars.
and the learning continues...
So under load the motor was going out of line - much like my eyesight. Seems to run great now.
 

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Ok Ian, not a big deal, not always obvious with the Revell chassis. And their system with the two small tabs to prevent the motor rotating isn't exactly an elegant solution.

For the crown gear side, don't depend on pictures. Connect the motor to a transformer, at 6V or so and listen, then reverse the leads and listen again. One direction should be higher-pitched than the other, thus faster, and that's how you determine which side to put the gear on!

Most of these early Mabuchi cans were supposedly zero timing, so the same speed in both directions, but in practice they always ran faster in one direction. And the later cans were advanced timed on purpose, so it's even more important to check the direction. Mura and other period rewinds usually had an arrow on the can to show which way to go.

Don
 

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Discussion Starter · #8 ·
More rookie questions...
I have just renovated a Policar 1/24 Alfa Periscopa. The first run proved 2 things - it is very pretty - and it's also slow!
I will try various things but my question is: can you tell from the pics what motor the car has currently and its RPM - and what would be a good motor to replace it ? (has to be pre 1970).
The gearing is very short, but can't be changed without breaking the regs, so I need more rpm .
Vehicle Car Wheel Hood Motor vehicle
Food Eyewear Wood Musical instrument accessory Bag
 

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How much oil are on the brushes? Too much will make the motor run slowly.that looks like a 16 d and should be able to push that car at a good rate of knots . Not sure what the RPM is but I'm guessing 25-37 000. Does the axle and crown have a little bit of free play? If the gear mesh is too tight that will make it slow!
Cheers,
John.
 

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Discussion Starter · #10 ·
How much oil are on the brushes? Too much will make the motor run slowly.that looks like a 16 d and should be able to push that car at a good rate of knots . Not sure what the RPM is but I'm guessing 25-37 000. Does the axle and crown have a little bit of free play? If the gear mesh is too tight that will make it slow!
Cheers,
John.
Thanks John.
The gear mesh is to tight I think (and noisy) but the spur gear seems to be a press fit item by the manufacturer. I am nervous about trying to move it on the axle as it may loosen? Or maybe I could move it and glue It ? Dunno as its all a bit new to me !
Thanks
Ian
 

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You were saying that it was short geared, maybe someone's put the wrong size pinion gear on the motor or replaced the motor . Take the motor out and see how much movement is in axle-crown gear if that feels all right try smaller pinion gear one tooth should be enough as long as the diameter is smaller too . I'm not sure , but check out the pitch of the gears being that age it should be 48 pitch most of the new stuff is 50 pitch , don't mix ! Buy the looks of the wear and shine on the pinion I think that's the case!top slot sell parts for those old Polistil you should be able to find out what pitch that Polistil ran and the correct gearing, they have a good range of parts!
 

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Hi Ian,

That's just a standard 16D or the equivalent, and it's a pretty slow motor originally! Just saw one of these cars in italy, very nicely painted, but not very fast! Any standard motor with this configuration should be able to replace it. If it's for the Thingie race at Champagne, you could indeed replace the gears, don't think there's anything against that!

Joel, you're right, I wasn't very specific: it's mostly the later can rewinds that definitely have advanced timing, and these days you can get motors with a 35° advance, pretty much on the limits! But I still say that, in practice, the earlier ones tended to be faster in one direction.

Don
 

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Discussion Starter · #13 ·
Thank you Don.
Yep - it may just be the way it was designed i.e. for home tracks and not with our champagne mouton monster track in mind!
I bought it because I just liked the look of it, so I may just experiment and learn with it.
Anyway - I have rediscovered my airbrush - so all is well !
Cheers
Ian
 

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Ian, I would try running the motor a bit longer to see if it gets quicker. Look what happened to the SP500 in the 1:32 Revell Corvette; like a snail compared to my Cobra when I lent it to you then you smoked everyone in the Confolens Classic having practised with it a good while!

If not, Garage Coeur de Lion chez moi will have a suitable replacement. Nothing too radical though because the chassis won't take it. For serious racing we could plonk the body - very pretty as you say - on a period chassis to worry the likes of Don and Joel next year ;)
 

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Discussion Starter · #15 ·
Hi Richard, I will certainly try all options to get this diva to go quicker. I may even try cleaning the motor in water (which seems counter intuitive to me - but has to be done for a giggle at some point !). Also I like the idea of dropping the body on another chassis and creating something scratch.
I have a feeling I won't be worrying Don and Joel, or others in 2022. Still on my learning curve.
2023 however...god willing!
(And I thought learning how to renovate old french buildings was a challenge - Mind you, I cracked that - so why not bring on vintage slot cars for a new challenge?)
All good fun.
 
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