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Author Topic: replacement Motor for Minitrix 2-6-0 / 2-6-2 type loco (continental)  (Read 1199 times)

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Offline Dr Al

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Re: replacement Motor for Minitrix 2-6-0 / 2-6-2 type loco (continental)
« Reply #15 on: November 22, 2019, 11:46:12 AM »
If we take basic engineering there is a formula BP= T x Omega
BP = brake power
T  = torque
Omega (should be the symbol but it’s not on my iPad keyboard), is rotational speed measured in Radians
Taking a simplistic understanding it can be likened to Formula 1 engines where a small litres engine at phenomenal revs can produce great power figures.
Coreless motors have little torque yet at high running revs you get the power needed. Strip open a late model Farish and you find multistage reduction gearing allowing the coreless to rev high. The Minitrix doesn’t have such staged reduction gearing hence the N drive motor just replicates the Minitrix motor.

Oh dear, the armchair physics.

"Power" is largely irrelevant. A loco running at a constant speed will have basically the same power draw (mechanical power, not electrical, see later) no matter what motor is driving it. It is simply related to the kinetic energy which is the same for a given speed and mass. There will be tiny second order effects of the motor armature spinning faster, but these are totally negligible as the mass of this component is so small compared the loco as a whole. All motors have plenty enough mechanical power, and plenty enough torque (turning force at armature shaft, NOT turning force at loco wheels, that being 'tractive effort' I believe) to run model trains.

Actual power draw from the source is completely different. The vast majority of this is lost as heat in the coil winding (due to electrical resistance), heat in the mechanical parts due to mechanical friction (this again being small). Thus, the measured current (from which the total power draw can be derived), in no way gauges mechanical power.

Moreover, the hotter motors run the shorter their lifespan - so actually coreless motors are extremely good as they draw so little current compared other designs.

Coreless motors may have lower torque (turning force) but none I've seen actually stall (motor stall) which would indicate insufficient torque. Just the same as cars, you can have as much power as you like, but putting it down on the track is the challenge - and coreless motors just break traction at the wheel/rail interface like any other. I've not seen a loco that can't be made to break traction - as such they have ample armature torque with appropriate gearing, and the adhesion is the issue.

Bear in mind too that the gearing choice may have been made from the opposite design choice - nothing to do with torque, but instead to take the speed down to a range that prototypical and also enhance ultra slow creep running. You are jumping to the assumption that the gearing is there due to torque - but I've tried Coreless motors on existing geartrains in a few tests with no trouble. Moreover, tiny flat can motors generally run very high RPM also, so again I'm not convinced this has anything to do with coreless specifically.

The remaining issue with small motors relates very little to any of this - it's the problem of lack of robust commutation. Commutators and wiper brushes are what die first on the small can motors and coreless, and this has precisely nothing to do with them being coreless. The problem is that the brushes do not have long lifespan, and wear through relatively fast (some reports saying 100hrs), and being metal also tend to wear the commutator more than traditional carbon. Generally they are not replaceable (though to some degree it is possible, but not for most punters). This is the only part of concern - everything else will not wear out in anywhere near that timespan, and its why I'm still keen to see a longevity test from Sven's.

Even that is not an issue, if it weren't the fact that they are so expensive to replace - nobody complains on old style motor brush replacement (basically the same thing) because brushes are usually just a few quid, and last longer.

In every other way, coreless is better - smoother, quieter, do not cog between poles, draw very little current, do not get as hot, smaller (so fit in many more locos more easily and allow prototypes that would have been impossible in the past). It's just commutation that is the outlying concern. But this applies to standard flat cans too - including the N Drive - I've seen many Farish flat cans die as quickly - just repaired one on a Farish 03 shunter - motor wiper brushes worn through. Date of manufacture on the box? July 2019....so it lasted barely a few months.

Cheers,
Alan
Quote from: Roy L S
If Dr Al is online he may be able to provide a more comprehensive answer.

“We have also arranged things so that almost no one understands science and technology. This is a prescription for disaster. We might get away with it for a while, but sooner or later this combustible mixture of ignorance and power is going to blow up in our faces.”Dr. Carl Sagan

Offline Jfheath

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Re: replacement Motor for Minitrix 2-6-0 / 2-6-2 type loco (continental)
« Reply #16 on: November 22, 2019, 12:19:52 PM »
Look on EBay item 182870714017
N drive are makers of 009 locos, this is their proven motor and its 12 volt.

Thanks Fredastaire, and apologies - I confused your motor with the 9v motor mentioned by Railwaygun at the top of the thread.

In terms of resistance, a healthy one of these motors has around 30 ohms resistance when measured between two consecutive commutator segments.

Normally, a good one can be running on 125-150mA.

Check the commutator position also - if this has rotated relative to the windings the performance can be poor as the back emf generated is not as high as it should be, so the current consumption goes up.

I'd seriously question why 3 new motors appeared to fail. This should not happen - I've seen these run for long periods. Are you oiling the commutator or not cleaning out the slots periodically?

Yes - I seriously questioned it too.  It was a few years back and I did a bit of research at the time = the only feasible suggestion was that the motors did not like DCC.  But I have converted a few of my models to DCC, including the 9F which has a similar sized motor, without problems.

I checked the commutator position with other motors.  Typically these are aligned with one edge of iron core.  I would have expected them to be centrally aligned, but there is no room for movement where the windings are soldered to the commutator.  But the motors were all brand new, no sign of wear.  A very tiny spot of oil on the bearing and nowhere else, and my commutators and grooves are spotless !  Something was wrong, and too late to find out what - but it seems that these motors suffer more than any other.  Poor treatment perhaps.  Most ebay photos show them without the wire coils being visible.  That always rings alarm bells with me.

I measured my working motors at 32ohms.  But of course, that measurement includes the in-parallel connection of the other two windings (which are connected in series for this measurement).  So the winding of a single coil, I reckon would be 21.3 ohms.

For information , On the one I unwound, there were 220 windings of 0.05mm diameter wire - which I reckon is 44AWG.

My sample of locos is very much skewed as I have never had one of these from brand new.  And my 3 brand new motors looked new and came in the typical Trix polythene bags with a Trix part number sticker on.  I was convinced - perhaps wrongly.  I never checked the position of the commutator in relation to the centre of the core on these.

Offline Dr Al

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Re: replacement Motor for Minitrix 2-6-0 / 2-6-2 type loco (continental)
« Reply #17 on: November 22, 2019, 12:23:47 PM »

Yes - I seriously questioned it too.  It was a few years back and I did a bit of research at the time = the only feasible suggestion was that the motors did not like DCC.  But I have converted a few of my models to DCC, including the 9F which has a similar sized motor, without problems.

Ah - I missed these were on DCC. Feedback or pulsed control may be something these do not like. I'd be suspicious of DCC in this instance, as the motors themselves should be fairly hardy.

Cheers,
Alan
Quote from: Roy L S
If Dr Al is online he may be able to provide a more comprehensive answer.

“We have also arranged things so that almost no one understands science and technology. This is a prescription for disaster. We might get away with it for a while, but sooner or later this combustible mixture of ignorance and power is going to blow up in our faces.”Dr. Carl Sagan

Offline Jfheath

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Re: replacement Motor for Minitrix 2-6-0 / 2-6-2 type loco (continental)
« Reply #18 on: November 22, 2019, 03:19:44 PM »
Thanks Dr Al - I'll be trying anything that I can to get these little locos running again.

--------------

Regarding the gearing on the Ivatts - they have a reduction ratio of 16:1   (ie it takes 16 turns of the motor to produce 1 turn of the drive wheels).  This is achieved primarily through the worm gear driving a 13 tooth idler gear.  A smaller reduction is made by the idler turning a 16T brass gear fixed to the centre of each axle. 


Offline Izzy

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Re: replacement Motor for Minitrix 2-6-0 / 2-6-2 type loco (continental)
« Reply #19 on: November 23, 2019, 09:53:22 PM »

It’s interesting to note re the coreless/finger commutation concerns that while the diameter of Faulhaber coreless micro DC range start at 6mm, they don’t produce a graphite version until 13mm dia ( probably due to the space requirements), and that precious finger versions cease above 22mm dia, with that size having a commutator of just 1-1.5mm dia to keep surface speed rates as low as possible to extend life expectancy as much as possible. Graphite versions are classed as heavy duty/longer lasting.

Izzy

Offline Sven

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Re: replacement Motor for Minitrix 2-6-0 / 2-6-2 type loco (continental)
« Reply #20 on: November 26, 2019, 05:11:37 PM »
OK, worked hard to get it done. My fingers were itching to convert it. (it also cleans my desk a bit up, has been there for months :claphappy: )It's ready, tested and the manual is also up. Will shoot a video to show the incredible change. It all fits perfectly. You can order it here, where you can find a link to the step by step installation instructions as well: https://tramfabriek.nl/drives-n.html#ivatt

Hope you like it.

Sven



Coreless 12V mini motors at tramfabriek.nl

Offline Jfheath

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Re: replacement Motor for Minitrix 2-6-0 / 2-6-2 type loco (continental)
« Reply #21 on: November 26, 2019, 07:31:44 PM »
That looks really neat.

Well done, you win - you could have waited until my motor arrived !  But it looks like I jumped the gun - I'll have to fashion my own holder for the motor. 
I intend to do a direct comparison with the n-Drive motor that was also discussed in this thread.  I've got one of those on order too - I quite like experimenting - especially since I have quite a few of these Ivatts lying around with burned out motors.

(Anyone looking in - since my last post,  I ordered the various bits that I needed from Sven at his website address posted above, motor, sleeve, flywheel, gear puller, and I said that I might get my conversion done first.  He accepted the challenge.  I hope mine looks as good as his.  When the postie finally arrives with it !
« Last Edit: November 26, 2019, 11:34:52 PM by Jfheath »

Offline Sven

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Re: replacement Motor for Minitrix 2-6-0 / 2-6-2 type loco (continental)
« Reply #22 on: November 26, 2019, 08:19:40 PM »
I shall send you a free cradle to fit the motor. It’s good when someone else can confirm that the kit works on another model.
« Last Edit: November 27, 2019, 12:07:38 AM by Sven »
Coreless 12V mini motors at tramfabriek.nl

Offline Jfheath

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Re: replacement Motor for Minitrix 2-6-0 / 2-6-2 type loco (continental)
« Reply #23 on: November 26, 2019, 11:12:53 PM »
That's kind - many thanks.  I'll certainly feed back to you.  I'm looking forward to seeing these locos run again.

Online Bealman

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Re: replacement Motor for Minitrix 2-6-0 / 2-6-2 type loco (continental)
« Reply #24 on: November 26, 2019, 11:20:54 PM »
Fascinating thread!  :thumbsup:

I too have a couple of these locos that could do with a new lease of life.

Vision over visibility. Bono, U2.

Offline Fredastaire

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Re: replacement Motor for Minitrix 2-6-0 / 2-6-2 type loco (continental)
« Reply #25 on: November 27, 2019, 09:36:53 AM »
As I said earlier ‘the proof is in the pudding’
So Sven youve touched the tip of a tiny iceberg in that youve found a way to sort those few worn out Minitrix.
.
There is a huge iceberg out there.
.
Graham Farish Poole design including the Poole original production and the Bachmann Poole clones.
.
Can you come up with a replacement motor cradle to fit your coreless motor as a direct retro fit?
.
There is an amount of China Clone production with broken top cradles and more with exploded commutators in need of a repair solution.
.
Then there are all the old Poole 3 pole and 5 pole worn out locos.
.
How about it Sven?
« Last Edit: November 27, 2019, 09:38:47 AM by Fredastaire »

Offline Dr Al

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Re: replacement Motor for Minitrix 2-6-0 / 2-6-2 type loco (continental)
« Reply #26 on: November 27, 2019, 09:49:30 AM »
Graham Farish Poole design including the Poole original production and the Bachmann Poole clones.
.

Why? The old Farish design motor is reliable, smooth running, able to creep (particularly the 5 pole) and robust, spares are still obtainable new, and given the current concerns with commutation (still to be definitively disproved - if any tests are to be done, I'd urge this as a priority) on can/coreless motors, it'll almost certainly outlast them.

There are very few commutator fails I've seen on China production - indeed I've seen as many on English production. I have pulled old commutators from complete burn outs to act as a replacement supply to the very few that I do see. The armature cradles can be bought new, and replaced, and attached easily and appropriately.

I'm not sure there's a problem that exists here to be solved, but anyone chucking their 3 and 5 pole Farish motors - chuck them in my direction!

Cheers,
Alan


Quote from: Roy L S
If Dr Al is online he may be able to provide a more comprehensive answer.

“We have also arranged things so that almost no one understands science and technology. This is a prescription for disaster. We might get away with it for a while, but sooner or later this combustible mixture of ignorance and power is going to blow up in our faces.”Dr. Carl Sagan

Offline Fredastaire

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Re: replacement Motor for Minitrix 2-6-0 / 2-6-2 type loco (continental)
« Reply #27 on: November 27, 2019, 11:20:27 AM »
Why?
Because Sven is saying his motor is somthing different and better, thats if im reading his script correctly. So if we can fit his next generation motor and have significant gains then ‘why not’.
.
As an aside comment my ‘rebrush repair exercise’ on defective Farish coreless motors is  still proving to work,  all four locos ( 3 standard 5 and one Austerity), are still working fine.
.
Bob at BR lines said he only has a few cradles left and suggested in a phone call that it would be the end when the stock had gone.
.
China Clone exploded commutators ive had were as a result of gear failure and the motor spinning up to fast without load. Examination of the debris showed a previously propogated crack.
« Last Edit: November 27, 2019, 11:27:25 AM by Fredastaire »

Offline Dr Al

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Re: replacement Motor for Minitrix 2-6-0 / 2-6-2 type loco (continental)
« Reply #28 on: November 27, 2019, 12:32:25 PM »
Because Sven is saying his motor is somthing different and better, thats if im reading his script correctly. So if we can fit his next generation motor and have significant gains

Unfortunately, I see little gain - it's "fixing something that isn't broken in the first place" IMHO. Comparison performance of a well maintained and adjusted China-Poole with anything can or coreless, there isn't a huge difference, and certainly not enough to warrant changing them IMHO, especially based on lifespan. For example, I retain my original Chinese Poole derived Black 5's because the perform much better at low speed than newer tool ones.

Stuff like Dapol's 14xx, 45xx - absolutely yes, because there could be a real controllability improvement in these models with a more restrained motor, and Sven's is a candidate for this.

As an aside comment my ‘rebrush repair exercise’ on defective Farish coreless motors is  still proving to work,  all four locos ( 3 standard 5 and one Austerity), are still working fine.

This is the crucial point. People are not going to recover these motors in this way - it's just not practical for 99.99% of owners (whilst admirable that you achieved it). As such, they are fundamentally throw away when their (short) lifespan is up. Poole Farish armatures? Just keep on going - the oldest of these (original Arnold derived) is over 40 years young now. The Poole armature is also no more expensive to replace (basically the same cost as the coreless) but I would surmise that they will need replacement far less often (never if cared for).

That's still the crucial thing for me - the lifespan of all these motors, and if that is short the replacement cost.

Bob at BR lines said he only has a few cradles left and suggested in a phone call that it would be the end when the stock had gone.

There should be very few occasions where these need actually replaced. For Bachfar it's a case of cleaning the base surface at commutator end and re-bonding it. While the original Farish dovetail was better, the Bachfarish method works fine as long as done precisely, carefully and correctly.

There are so many cradles about - I've a box load.

China Clone exploded commutators ive had were as a result of gear failure and the motor spinning up to fast without load. Examination of the debris showed a previously propogated crack.

Rare. Little to do with China - I've seen English silver commutator ones do the same, but usually they are clearly damaged beforehand, by a previous 'owner'. The chinese commutators are the same as used in Bachmann's split chassis skew wound motors.

The armatures are perfectly capable of running full speed for extended periods - I do this to first run them in. I suspect the reality is that yours had invisible weakening or damage from previous ownership - I've certainly seen that in the past.

I get the impression the BR Lines is slowly starting to wind up - do you get that impression? All the original Dapol spares appear to have been dropped now too, and some possibly being dumped on eBay in recent times (at least there was some coincidentally similar stuff - 10s of Voyager Lighting, bagged and unused, class 73 driveshafts etc). I would hope he'd consider selling on or allowing the concern to be taken over by someone else when that happens, to keep our "old reliables" supplied and able to be mended.

Cheers,
Alan
Quote from: Roy L S
If Dr Al is online he may be able to provide a more comprehensive answer.

“We have also arranged things so that almost no one understands science and technology. This is a prescription for disaster. We might get away with it for a while, but sooner or later this combustible mixture of ignorance and power is going to blow up in our faces.”Dr. Carl Sagan

Offline Sven

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Re: replacement Motor for Minitrix 2-6-0 / 2-6-2 type loco (continental)
« Reply #29 on: November 27, 2019, 12:55:42 PM »
Let's end all doubt here.  :beers:

« Last Edit: November 27, 2019, 03:48:09 PM by Sven »
Coreless 12V mini motors at tramfabriek.nl

 

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