Motors and gearboxes, uses and notes.

Motors and gearboxes, uses and notes.

Postby Bertiedog » Sun Aug 16, 2009 2:37 pm

Part one

I think it must be worthwhile to post a few notes on motors and gearboxes, as so many opinions and queries are posted on RM during postings about loco building in general.

Having had long experience in modelling, both professional and private, I have gathered up a lot of experience with this and feel the notes should help both old hands and newcomers to the hobby.

Some basics first about motors

Our models run on DC motors, even with DCC control, and the basic requirement is a DC motor that runs on 0 to 12 VDC at a reasonable current, and the main type that for meets the requirements for this is the Permanent Magnet Direct current motor.

There are two basic types these days, Coreless and Conventional Multi Pole motors. The coreless DC motor was developed for instrument use, low current and light duty, but very well built. They have a disadvantage, despite all the plus points in that the main shaft usually cannot take an end thrust, and require special gearboxes to apply the power to the track.

The multi pole motor is usually chosen as it is simple to design and build and experience has shown that the basic design is very reliable indeed.

The first motor makers for model railways were Mantua in the United States, in the 1930's, who designed a range of small 6 volt DC motors, later altered to 12 volt DC in the 1940's.

In the UK the most popular of early 4mm scale OO locos were fitted with 6 volt motors, conventional designs for the 1930's period, later altered to 12 volts as it gave more reliable operation. Stewart Reidpath were the first UK dedicated motor maker, for his HO models in the 1930's.

AC operation, as with O gauge had been considered and used, but was not easy to fit to the tiny locos in 4mm scale. the motors need a reversing mechanism and there is little space in such a model. Marklin in Germany were the only maker to persist with the design.

With Direct Current the situation is easier all round, and Hamblings in the UK were the first to use 12 volt DC open framed motors commercially, built for them by the British Motor manufacturer Taycol. These were state of the art, and still a sound and very expensive design, ball raced, and the shaft was supported and both ends with an "in frame" gearbox.

This general style was adopted by Romford and Zenith, who introduced motors after the war along modern design principles.
Zenith made a seven pole motor with a brass frame that is still considured to one of the finest motors ever designed.

Rather regretably the cost was high, and Zenith were taken over by Tri-ang who used Zenith to make the XO series of motors, fine in their way, but cheaper to make and greatly simplified design and build quality.

Mantua's pre-war design in the States was adopted by Pittman, who was an enthusiast owner of an electrical supply company, with an interest in motors. His own models were O gauge US trolleys, but they developed a range of classic open framed motors, about the finest made at the period, and still a very sound design. They were also involved with Varney and Lindsay, making Lindsay's then unique ring field motor, which was copied by Meccano in the Hornby Dublo range later on.

By about 1950 all the designs were settled, and the conventional motor in it's open framed form remains the main type of motor used in conventional model railway designs, ranging from 3 pole to 7 pole types.

An early user of Pittman was Formo/Preen in the UK, ( Graham Farish), when Farish had troubles producing a good motor of their own design, succeeding only in designing a unique and ghastly Heath Robinson 2 pole motor. Not really their fault, it was the wartime restrictions that lingered on after the war that meant they were forced to use an odd design to get around the rules.

Meccano remained aside from the conventional designs , preferring to build the motor in to the Dublo chassis as a unit, or using the Ringfield principle as in the Castle motor. This was based on the Lindsay, but had not got full ballraces and only had a conventional 3 pole armature, to lower costs.

Now a major point, there is absolutely no difference between a cased motor, with a can cover, and an open framed motor, both have the same electrical characteristics and performance, The magnets may be a pair, but act as one and the same as a block magnet. The can motor can also have a ring field magnet, which again promotes smooth operation and efficiency, unless it is cheaply made by Lima of course!!!

The can motor was developed from the Toy industry in Japan, a simpler way to make a motor, by using a drawn steel case and cheap cast alnico magnets, cheap to make, but not better or worse than an open framed motor. Quality depends on cost, and vice versa.

The can motor was developed by Japanese makers, adopting ring magnets in some, and higher quality materials , until we have as an example today, in the Mashima Types. Most have powerful rare earth magnets like neodymium.

The basic commutator and armature remains the same design across the years, usually a three pole or more type, with seven being considered the best option, but rarely made due to cost these days.

The more poles the smoother the motor, as each pass of a magnetic pole causes cogging, a jerk in the rotation, so a greater number of poles will help with the smoothness. Lindsay invented Skewed or twisted slot motors, where the pole overlap smooths the operation.

The commutator and brushes work in exactly the same way in all motors, it is the application and quality that varies, for instance the Old K's motor used the same design basics as Mashima, but K's are awful, badly made and un-reliable, but the Mashima work due to the quality of the parts.

In the UK the next design changes in the late 1950's came from another use, in electric slot cars, and as these became popular they governed the design of cheaper motors. Many makers adopted the cheap and cheerful simplification of design, and quality suffered badly in the model railway field.

Tri-ang did make reasonable 3 pole motors, but only in the mass RTR market, and cheap design governed the quality. Romford and other's like MRRC keep making standard designs , but costs spiralled in the UK, and the comparison with imported designs began to finish them off in the 1980's.

Another deep problem in the UK was the gears, made by only a couple of makers, who simply could not produce concentric or accurate gearsets in the 1960's onwards.

Most open framed motors use a worm drive, a worm on the motor shaft and a gear on the axle, but if either are inaccurate then the whole thing is poor engineering and at worst, complete and utter trash.

The main changes in the UK came in the 1980's when can motors from Japan and the far east became more available, and gearsets were made to reasonable accuracy. It became popular to add a folded etched metal frame to act as a gear box, screwed to the end on the motor, which helps assembly of an accurate gear mesh.

This is the current situation, can motors, some times round, sometimes flat sided, occasionally semi open Far Eastern motors, fitted to etched frames which fit between the frames, sometimes allowing side play for axles that require it. There are several producers, and multi fit designs, all work well if assembled carefully, but some need great attention to detail in assembly.

In the States the design went down a different path, a motor separate from a gearbox, with a universal joint to the motor. This allowed a bit more flexibility of mounting, and application. The open framed motor remained popular a lot longer due to more space in larger models. The can motor has now taken over due to cost and design improvements,

As US made motors went off the market due to cost, etc, the Japanese motors took over, but the basic design remains the same and price is the main indicator of the quality.

Now all of this refers to scale models, not toys or RTR types like Bachmann, Airfix, Hornby, and a thousand others, who all have designed both good and bad motors and transmissions, mainly governed by cost, not design excellence.

There have been crossovers between the types, Tri-ang were used in scale models, but mainly because there were freely available, not by choice. In the UK the better makes like Taycol have long gone, and the better models use coreless motors, German and Japanese made.

Portescap in the UK combined a coreless motor with a Swiss gearbox, and got good results, but it needs care to fit and a very sound appreciation of the engineering to get the best from them.

A big source of good motors have been the Japanese electronic industry, like Canon and Aiwa (Sony), who have made small motors for other uses that have found their way into model designs.

Canon make fine motors especially for models as well, but mainly larger types that dual as mechanism motors as well. They pioneered the use of gearhead motors, where an in line encased gearbox is built into the motor. These are not much use as motors for trains as the gear output still has to be turned around at 1:1 by a worm gear to get the drive to the axles. But such gears are now available and this type of motor offers very powerful and silent operation..

As can be seen from the above notes, the variations are legion, but the principles of operation remain the same, despite the dozens of types of motors.

Motors should have a wide power characteristic, be well made, have serviceable bearings, be they plain or ballraced, decent brushes that are replaceable, and the vital point is that the gears must be top quality, the most important point of all.


You should not be able to hear a motor running on it own, and in the loco it should be smooth and quiet, no jerks, jitters, binding, slowing and pausing or any other problem. The loco should have enough power to operate a train, and under strain there will be a bit more noise, but no rattles or excessive mechanical noise.

Gears are vital, and all I can advise is go to a maker who actually manufactures them like Ultrascale, or source from a specialist maker to industry, expensive but worth it. The typical worm and gear drive sets in the UK now are not too bad at all, and with care fitting work fine. If you have a lathe and home workshop it is quite practical to make them yourself, but it is somewhat complex, but again worth it to get complete accuracy.

Part two will cover the types, mounting and gear frames and boxes, and Part three will cover universal joints and tender drive motor mounting, all simple home mechanics work, or easy application of commercial items.

Stephen.
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Re: Motors and gearboxes, uses and notes.

Postby Pannier Tank » Sun Aug 16, 2009 4:37 pm

Hi Bertiedog,

Some very useful information; looking forward to Part two. Will come in handy when I start Locomotive Construction. :thup
Regards,

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Re: Motors and gearboxes, uses and notes.

Postby Dutch_Master » Sun Aug 16, 2009 6:51 pm

Very interesting indeed. Mod's/Andy, can you put a sticky to this thread please?
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Re: Motors and gearboxes, uses and notes.

Postby bike2steam » Sun Aug 16, 2009 7:07 pm

Bertiedog,
Excellent :thup
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Re: Motors and gearboxes, uses and notes.

Postby ThePipersSon » Sun Aug 16, 2009 8:33 pm

Thank you - very interesting.
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Re: Motors and gearboxes, uses and notes.

Postby LNWRmodeller » Mon Aug 17, 2009 10:03 am

The EMGS manual has a considerable amount of information on the 12v motors readily available through the trade. This includes a mechanical assessment, power output, operating speeds, etc. They also provide information on motor mounts and gearboxes, useful to these of use that don't want to make our own gears. The information provided in the manual is worth the annual membership fee alone to 4mm modellers, even if you don't build to EM gauge.

The CLAG website also has some interesting information from their research into small drive trains for motor bogies and "unusual" small prototypes.
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Re: Motors and gearboxes, uses and notes.

Postby LNWRmodeller » Mon Aug 17, 2009 10:48 am

[quote="Bertiedog

Now a major point, there is absolutely no difference between a cased motor, with a can cover, and an open framed motor, both have the same electrical characteristics and performance,

Stephen.[/quote]


Stephen,

I don't share your opinion on this. Generally speaking, can motors develop their maximum power at lower speeds than open frame motors. Size for size, they are usually more powerful. As a result "lower" gear ratios, with less power losses can be used.

To the best of my knowledge, all the recent introductions of 12 volt motors (and not just for model railways) have been can motors. Why would manufacturers follow this path if they weren't better than O/F motors.

Jol
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Re: Motors and gearboxes, uses and notes.

Postby John_Hughes » Mon Aug 17, 2009 12:26 pm

I still have a bunch of old open-frame motors, including a Romford 'Terrier' (anyone remember those? they were designed for TT3 locos) and quite a few Japanese ones from the 1970s.

They all still work well (though the Terrier doesn't half run hot on anything but pure smooth DC from a battery) and I do have a few projects on the list where they might come in useful. However, the current draw on all of them is substantially higher than on a modern motor, which has obvious implications for DCC.
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Re: Motors and gearboxes, uses and notes.

Postby micklner » Mon Aug 17, 2009 2:40 pm

Good read :clap :clap .
Does anyone know why the Anchoridge motors I have, are running for about 30 seconds at full speed then die. Leave for a couple of minutes then the same happens again?? they have been in storage for about twenty years . I have five all doing this :wall :wall . I have cleaned the commutators but have been unable to find anyone who has new brushes for sale.
So far I have changed three for Mashimas etc, thought I would ask just in case anyone can suggest anything to save some time and money !!

cheers

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Re: Motors and gearboxes, uses and notes.

Postby hayfield » Mon Aug 17, 2009 4:33 pm

Bertiedog

Thanks for all the effort you are putting in to this thread, I am looking forward to the other 2 parts.
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Re: Motors and gearboxes, uses and notes.

Postby Bertiedog » Mon Aug 17, 2009 4:52 pm

Stephen,

I don't share your opinion on this. Generally speaking, can motors develop their maximum power at lower speeds than open frame motors. Size for size, they are usually more powerful. As a result "lower" gear ratios, with less power losses can be used.

To the best of my knowledge, all the recent introductions of 12 volt motors (and not just for model railways) have been can motors. Why would manufacturers follow this path if they weren't better than O/F motors


Er.. simple one there .....cost.... can motors are a bit cheaper than an open frame to make, using parts made for general purpose motors for other electrical goods, and have a lower part count.

Modern can motors do draw less current, as they are designed with modern magnets, which are better, making possible thinner wire on the commutator.

But it has nothing to do with whether the motor is enclosed or not. An open framed design could have a neodymium magnet used and the wiring could be altered to suit, and the motor would out preform a can version, due to the cooling, and it could have decent brushes fitted with adjustable springs, which a standard can motor can't.

I am not saying that all older motors are better, but that the best product these days could be an open framed motor, with ball races on both ends, a neodymium magnet, and a seven pole skewed slot armature, mostly features sorted out years ago and now not offered due to cost. It could also be offered in a can form, but it is not, cans tend to be cheaper designs.

Mashima motors are good, but do not have ball races as standard, and although replaceable, the brush gear is a bit small and not adjustable. Buhler are a bit better, and offer ballraces on some versions

There are lots of superb designs in can style on the market, notably Canon instrument types, that are so much better than offered for Model Railways, so we do not need to return to the older open frame, but it surprises me that people have so much trouble with open frames and then blame the type rather than looking at the design and build quality.
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Re: Motors and gearboxes, uses and notes.

Postby Bertiedog » Mon Aug 17, 2009 4:59 pm

micklner wrote:Good read :clap :clap .
Does anyone know why the Anchoridge motors I have, are running for about 30 seconds at full speed then die. Leave for a couple of minutes then the same happens again?? they have been in storage for about twenty years . I have five all doing this :wall :wall . I have cleaned the commutators but have been unable to find anyone who has new brushes for sale.
So far I have changed three for Mashimas etc, thought I would ask just in case anyone can suggest anything to save some time and money !!

cheers

mick

Sounds like the brush gear, I assume the Anchoridge have the tubular brushes with a spring on top, it may mean sourcing new brushes from another make. They might need filling etc to fit if larger, but most brush material is about the same composition and would work if it can be made to fit.

If the original brushes are soft, they are breaking up and shorting the commutator, which is not a good design on the Anchoridge. The gaps are large and not filled.

Also check the brushes can move freely in the tube mounting, they might be jamming with heat.

Apart from that the motors should be all right, I have used them over the years without trouble.

Stephen
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Re: Motors and gearboxes, uses and notes.

Postby micklner » Mon Aug 17, 2009 5:37 pm

thanks re Anchoridge problems , the brushes are free moving ,I will try a pencil lead and see what happens before they are ebayed


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Re: Motors and gearboxes, uses and notes.

Postby Bertiedog » Mon Aug 17, 2009 5:55 pm

Coreless motors

A bit extra on motors and this is about the Coreless type, which has a lot written about it and a lot of miss information.

The Coreless motor is an ordinary motor turned inside out!! it was developed from an earlier type, the Distler type, in which the wire coil magnets remained stationary, and a permanent magnet on a shaft rotated.

This was first used in the Model railway field with the introduction of the Graham Farish motor after the war. The design used two coils, on on the top of the motor, and one on the bottom, with a shaft and magnet running through the middle.

This only allowed the use of a two pole magnet, and therefore the motor was a two pole type.

This has an inherent problem in that it is not self starting!!!!! a major problem. Farish were electrical and radio engineers and the design was proceeded with despite this problem, as they came up with an ingenious solution.

The commutator was replaced with switchgear, on the end of the motor, which applied pressure to the armature to always stop in a position where the motor could restart.

However in a model train we have no idea just where the motors will have to come to a stop, and re-start, so Farish were forced to add a clutch, which allowed the motor to coast to a halt on it's own. But it also meant that the clutch had to engage abruptly as the loco moved off, hardly a plus point.

Also it was found that the contacts did not always return the motor to the correct position, wear and tear etc., got at it, and often the loco had to be pushed to start.

But the motor was surprisingly efficient, rivalling modern designs, low current and lots of power.

The related Distler type used some of the ideas, but solved the problems of the Farish. The first type had a multi pole magnet on the shaft, and multi coils, making a superb design, but the magnets were complex to make, and they then came up with the grand daddy of coreless designs, placing a permanent 2 pole magnet stationary in the middle of a rotating coils.

This type found it's way into model railways in early Joeff Trains, but was developed by the instrument motor industry into the coreless type. Having low mass they suited servo mechanisms in aircraft displays etc.

The main problem at first was the magnet got in the way of the shaft, and was solved by making the shaft come from one end of the motor only, but introducing the problem that coreless motors cannot take an end thrust.

The armature became coreless by potting the wire in resin, and using no metal at all to support it, with the close fit possible the magnetic field is far stronger and the motor more efficient. The coils are like a basket closely fitting over the magnetic core.

The number of poles can be increased as far as the design will take, and the design is naturally smooth as there is no magnetic cogging.

There is still brush gear attached to the coils via a commutator, but because of the delicacy of the coils, they design these with gold commutators and specialist brushes that do not need replacement in the motors lifetime.

Generally the motors are super efficient, low current, and because of the lack of cogging, very quite, and as most are designed for instrument use, they are ballraced as well.

If the coreless motor is single ended shaft type, then it cannot take end thrust, and prefers suitable spur gears or a universal joint to connect it to a gearbox. If it is double ended usually they can take end thrust, and have worm gears fitted direct.

There are no model railway designs as such, suitable motors are picked from other uses, which range from high end Hi-fi to instrument drives in aerospace uses. They tend to be expensive, but the smaller types are available quite cheaply as they are mass produced. A noted maker is Faulhaber in Germany.

Portescap in the UK marketed coreless on a Swiss gearbox, and very nice but expensive motor unit. I believe that they are not made now, or only in limited batches.

Coreless need care to use them, they do not like overloading, and on DCC need a special chip to handle the low current and different impedance of the motor. Performance on DC is superb, no type of motor can beat the slow speed operation and silence.

Stephen
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Re: Motors and gearboxes, uses and notes.

Postby LNWRmodeller » Tue Aug 18, 2009 12:52 pm

Bertiedog wrote:
Stephen,

I don't share your opinion on this. Generally speaking, can motors develop their maximum power at lower speeds than open frame motors. Size for size, they are usually more powerful. As a result "lower" gear ratios, with less power losses can be used.

To the best of my knowledge, all the recent introductions of 12 volt motors (and not just for model railways) have been can motors. Why would manufacturers follow this path if they weren't better than O/F motors


Er.. simple one there .....cost.... can motors are a bit cheaper than an open frame to make, using parts made for general purpose motors for other electrical goods, and have a lower part count.

Modern can motors do draw less current, as they are designed with modern magnets, which are better, making possible thinner wire on the commutator.

But it has nothing to do with whether the motor is enclosed or not. An open framed design could have a neodymium magnet used and the wiring could be altered to suit, and the motor would out preform a can version, due to the cooling, and it could have decent brushes fitted with adjustable springs, which a standard can motor can't.

I am not saying that all older motors are better, but that the best product these days could be an open framed motor, with ball races on both ends, a neodymium magnet, and a seven pole skewed slot armature, mostly features sorted out years ago and now not offered due to cost. It could also be offered in a can form, but it is not, cans tend to be cheaper designs.

Mashima motors are good, but do not have ball races as standard, and although replaceable, the brush gear is a bit small and not adjustable. Buhler are a bit better, and offer ballraces on some versions

There are lots of superb designs in can style on the market, notably Canon instrument types, that are so much better than offered for Model Railways, so we do not need to return to the older open frame, but it surprises me that people have so much trouble with open frames and then blame the type rather than looking at the design and build quality.


Stephen
You’ve ignored the question of can motors developing their power at much higher rpm than can motors (based on reference to the data sheets in the EMGS manual). Even the more recent small Mashima O/F motors display this characteristic.

Perhaps the "can" format allows smaller magnet/pole to commutator clearances. This would give higher efficiency and lower current for a specific power output.
Are O/F motors more expensive to produce? Based on the price list of one importer of Japanese motors, they are definitely cheaper to buy. But that may be down to the fact that the O/F motors on offer are slightly older designs without the latest magnet technology, etc.

While ball bearings are undoubtedly "better" than plain bearings, are they necessary and do they provide sufficient benefits for the extra cost. I can see that they are probably worthwhile in larger, high power R/C aircraft motors equipped with potentially poorly balanced propellers, but don't think that they are definitely required for our applications.

You have referred elsewhere to adjustable brushgear. Why is adjustable brush gear required? If it is properly designed and manufactured in the first place, then adjustment shouldn't be necessary. Lower speeds and currents give longer brush life. Correct and accurate adjustment might be too difficult for some modellers, and would certainly be a no-no on RTR models.
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Re: Motors and gearboxes, uses and notes.

Postby alcazar » Tue Aug 18, 2009 1:11 pm

Putting that argument aside for a moment, I'm sure I've read an article, some years ago, in which someone took apart an o/f motor, removed all the windings, then split the laminations and skewed them, then rewound it to make it a better, smoother motor.

Or did I dream it?
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Re: Motors and gearboxes, uses and notes.

Postby James » Tue Aug 18, 2009 2:52 pm

Bertiedog wrote:unless it is cheaply made by Lima of course!!!


Hmmmm...

I do think that if you care for Lima locos, certainly their products from the 90s, you can make a decent runner out them.
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Re: Motors and gearboxes, uses and notes.

Postby Bertiedog » Tue Aug 18, 2009 3:04 pm

The modern motors are higher power at all revs, due to the magnets, close gaps, and also better grade steel in the armature, but also tend to have a high end peak, and that is not actually what is wanted for Locomotives.

The motors does work as soon as it starts rotation, and this is from zero, requiring the current supplied to be converted to mechanical effort right from the first application of voltage.

The most efficient of the motor designs is the coreless, with no metal core losses, and efficiency is remarkable at low revs, with motors able to idle at very low revs. There is no cogging to overcome like a conventional motor, so the start is easy, all electrical power is converted to mechanical, bar usual mechanical losses.

All conventional motors have magnetic cogging over each pole, magnetic drag, which is overcome by the applied electrical power, but tends to come on in a burst, leading to jerky starting. More poles help here, and seven should be the minimum, five are acceptable. Skewed slots help as well, these cause an overlap of each transitions of a pole, making it smoother, and easy to start to get moving. Windings also make a difference, star winds are better for our uses, but are rarely supplied as it is more costly to wind and connect up in production.

The art of design of the components is to reduce starting effort being applied to soon, or too late.

What a motor returns in fractional horsepower at higher revs is of very little consequence( unless it falls), as the gear ratio is in full play, and if the motor has enough power to get moving, all others things being equal, does not acquire an increase as the revs get higher. Measured via a gearbox the measured horsepower increases with revs due to mechanical advantage.

All motors have theoretical max output, at a given current curve as the voltage is increased.

Ballrace bearings are much more efficient than plain, especially at the vital low revs as the loco starts moving. Figures vary, but anything from 10% to 20% can be gained, the highest figures for high speed rotation. Also they remain quiet, no wear, so no increase in noise.

It is not for the user to adjust the brushes, this is not needed. but it makes the motor serviceable later one in it's life. It can help to slacken brushes on a new motor, if a loco is say a shunter, as the friction will be somewhat lower and slow running better.

There is no one solution that fits all, different motors are needed for different uses. The Mashima range covers about all requirements, but could be improved, at a price, with ball races.

I have modified several Mashima tube can motors with Borden instrument ball races, added to the ends externally, with the bronze bearings removed. It also makes the motor suitable for a flywheel on the motor shaft, risky with plain bearings.

Can motors have fewer parts and therefore cheaper to make, as Johnson in Hong Kong found out, making toy motors for pence.
A open frame has better ventilation and easier to adjust brushes, but no actual advantage over a modern design, like Pittman instrument, Canon, or Buhler etc, and open framed have fallen from use, my point is that open framed does not mean a bad motor
Last edited by Bertiedog on Tue Aug 18, 2009 4:12 pm, edited 1 time in total.
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Re: Motors and gearboxes, uses and notes.

Postby Bertiedog » Tue Aug 18, 2009 3:17 pm

alcazar wrote:Putting that argument aside for a moment, I'm sure I've read an article, some years ago, in which someone took apart an o/f motor, removed all the windings, then split the laminations and skewed them, then rewound it to make it a better, smoother motor.

Or did I dream it?


Virtually any 3, 5 or 7 pole armature could be altered from straight slots to skewed slots. it reduced magnetic cogging, making the motor start easier and run quieter at all revs. There is no reason not to fit it, apart from cost.

An armature is easier to wind with straight slots, it is as simple as that. You can re- wind them at home, it is not easy with 7 poles, but you can easily do it with 3 poles. The problem these days is the epoxy resin used to stack the laminations, it needs heat to shift it and re- assemble. A lot of work to alter an old motor.

You can also Star Wind the armature, where the wires are taken from each segment of the commutator and not wire to the next, but to the tail connection of the next poles windings. The current return path is via the next poles windings, which is out of magnetic reaction at that point, reducing the over-all current, and smoothing the action of the motor, with a slight loss of power overall, but most motors can spare it.

Makers like the Japanese do not star wind, as it costs more with extra soldering and insulation, so costs more to do.
Last edited by Bertiedog on Tue Aug 18, 2009 4:12 pm, edited 1 time in total.
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Re: Motors and gearboxes, uses and notes.

Postby Bertiedog » Tue Aug 18, 2009 3:34 pm

James wrote:
Bertiedog wrote:unless it is cheaply made by Lima of course!!!


Hmmmm...

I do think that if you care for Lima locos, certainly their products from the 90s, you can make a decent runner out them.


I very deliberately left out of this thread most commercial RTR motors, except where they are good designs, and where a reference is made to bad design, RTR is another world entirely, not scale models with separate motors to be chosen by the user.

RTR designs are often integrated closely into the chassis, fewer parts, use a lot of plastic , and are not modifiable, or in the case of Lima, and to some extent Hornby, had an odd misunderstanding of why a Ringfield magnet should be used, and how to arrange one.

Lima made motors in a pancake form, with side magnets later moving to a ring magnet, but not a full Ringfield. Frankly they are made to a price, for train set use, and yes they run, but the standards are low. and the motors are not usable in scale models as a universal unit. Rivarrossi made almost identical motors in style, but better made, but again they are RTR to a price.

Now intrinsically the Lima design is not bad, just acres of plastic, and I have altered the motors to have ball races, and removed the armature and re-wound it. The wire they used was not potted with resin and the commutator was crude, requiring a replacement to gain long term reliability.

Even the German makers made mistakes, the Flieshmann pancake motors are not the best at slow speed running due to magnetic cogging, curable with skewing the slots and a star wind.

Most Lima runs OK, but could run so much better with attention by the designers to the details.
Stephen.
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Re: Motors and gearboxes, uses and notes.

Postby Bertiedog » Tue Aug 18, 2009 3:59 pm

As it has come up in postings, Ringfield should be mentioned. This is a type of motor, not a single commercial motor. As mentioned before the main problem with conventional poled motors is that they "COG".

With any kind of magnet the field is applied a two poles, and however many poles the armature has, each one has to force its way past the magnet. This jerks stops smooth starts, and creates noise at higher revs, it is the purr that you hear from running an un-loaded motor.

More poles eases the problem, but skewing the poles till they overlap is the next answer, along with star winding of the poles, a special trick way of connecting each poles wiring.

The next improvement is the can motor, the fully machined thicken steel type, where the magnetic poles are still concentrated to allow operation, but the case acts as a shunt and allows smoother operation.

This is not the same as a simple can motor, which may still contain two magnets, or a side magnet as with pancake motors.

The answer is the Ringfield, which was designed by Lindsay, and used by Meccano in Dublo locos. Now Meccano did not fully implement the design, using a plain armature, not skewed, although they did star wind some 1950's production.

The Ringfield is a solid ring of magnetic material, with poles induced in to the ring, which act in the same way as separate magnets, but whole magnetic field is smoothed out in the transition between the poles, reducing cogging with little loss of power.

With a minimum air gap, Ringfield magnets, a skewed slot armature, with a star wind, and ball bearings, you have a perfect basis for a de-luxe design for a model railway loco.

Ringfield motors that work are Meccano's Castle type,( as long as not a Binns Road Friday afternoon job), and the types that are poor are Lima and Hornby, where the air gap is large, the materials plastic, and often with poor commutators and poor main bearings.
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Re: Motors and gearboxes, uses and notes.

Postby Bertiedog » Tue Aug 18, 2009 4:40 pm

star.JPG
star.JPG (15.1 KiB) Viewed 4580 times


The drawing shows the wiring for a DC motor with star windings, it does not matter about the number of poles, the principle is the same.

The wiring from each pole is not returned to the next pole but to the point x , all soldered together, and the current return goes in opposition along the next poles wires. This does not stop the motor, as the return pole is out of the magnetic field at that moment, the result is a reduction of current and less cogging, especially with a ring field magnet.

Do not confuse with star wound three phase AC motors, same type windings, different fields and phased AC operation.
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Re: Motors and gearboxes, uses and notes.

Postby Dagworth » Tue Aug 18, 2009 4:45 pm

Tortoise point motors are star wound.

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Re: Motors and gearboxes, uses and notes.

Postby James » Tue Aug 18, 2009 5:19 pm

Bertiedog wrote:RTR is another world entirely, not scale models with separate motors to be chosen by the user.


I'd say my diesels are very much scale models.

Bertiedog wrote:Most Lima runs OK, but could run so much better with attention by the designers to the details.


Older RTR mechanisms do have a look of being built 'to a price' but have their place for me - a sixty I have, for example, is Lima based with Ultrascales and plenty of lead - on a planned layout it will run through on the mains with no problems and be able to stop and start smoothly. Locos like this don't need to shunt; the prototypes aren't suited to this task either.
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Re: Motors and gearboxes, uses and notes.

Postby Bertiedog » Tue Aug 18, 2009 5:56 pm

James wrote:
Bertiedog wrote:RTR is another world entirely, not scale models with separate motors to be chosen by the user.


I'd say my diesels are very much scale models.

Bertiedog wrote:Most Lima runs OK, but could run so much better with attention by the designers to the details.


Older RTR mechanisms do have a look of being built 'to a price' but have their place for me - a sixty I have, for example, is Lima based with Ultrascales and plenty of lead - on a planned layout it will run through on the mains with no problems and be able to stop and start smoothly. Locos like this don't need to shunt; the prototypes aren't suited to this task either.



Your not reading the comments, I simply separated RTR, toy, and and Scale Models manufacturers motors and mechanisms, but this does not mean that RTR are not scale models. It does not mean all RTR are toy or toy like.

Lima have never been a scale model maker, they are an Italian, now owned by Hornby, toy train maker, and I fully appreciate that the expression TOY or TOY TRAIN seems to be like a red flag to a bull in the UK. It is not denigrating a particular model to describe it accurately as made by a Toy manufacturer.

Unlike the States, where there is still a thriving Toy Train market in H0 and 0 gauge, most British modellers react with horror at any connection being made between toys and models.

Most RTR motors cannot be used outside the loco they are designed to go with, although makers do use standard designs across the range.

A scale model is usually defined as a non RTR kits or Scratchbuilt model, or a type of RTR that meets scale standards. Kits are made to take any make of motor that could fit.

It is useless to go backwards and forwards saying this model, or that, is a toy or a model, they are both to different people, at different times, and many toy makers have made fine models, but that does not make them scale model makers. As you have done with the Lima it has been improved on making it nearer scale.

Meccano never claimed to make scale models, they made train sets, even more so with Tri-ang. Bachmann make both scale models and toy trains at one and the same time, as does Hornby these days.

Stephen.
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