Campaign for low-voltage N-Gauge motors

[Robin2]

It would be much easier to convert locos (and EMUs/DMUs) to battery powered radio control if the manufacturers built them with 5v motors rather than 12v motors,

 

If the locos were factory fitted with 5v motors it would only require the manufacturers to build in a cheap resistor so that, out of the box, it would run on 12v.

 

To use the loco with a battery it would just be necessary to remove or bypass the resistor.

 

How would we go about starting a campaign to convince manufacturers to include low voltage motors in new designs?

 

...R

[StuartM]

It would be much easier to convert locos (and EMUs/DMUs) to battery powered radio control if the manufacturers built them with 5v motors rather than 12v motors,

 

If the locos were factory fitted with 5v motors it would only require the manufacturers to build in a cheap resistor so that, out of the box, it would run on 12v.

 

To use the loco with a battery it would just be necessary to remove or bypass the resistor.

 

How would we go about starting a campaign to convince manufacturers to include low voltage motors in new designs?

 

...R

Same way we convince them to fit batterys and a RC chip,

Persistance I guess 

[Robin2]

Before persistence can be applied there is a need for an effective way to open a line of communication - which is what I'm looking for advice about.

 

In what way as this website access to the ears of influential people in Bachmann, Hornby or Dapol - or any other big or small manufacturers?

 

Are there other lines of communication separate from this website which would be more effective, or which could be used in a complementary way?

 

And I hope we can show several people pushing the matter in this Radio Control group - one or two isn't enough.

 

...R

[Suzie]

It is more than just adding a resistor to make a 6V motor run on 12V. A motor in a Heljan 00 loco for instance uses 750mA@12V, which would be 1.5A@6V. If a resistor was used it would need to be a 9W 4R7 resistor (at least) which is a big one, and to operate this loco on DCC with a low voltage motor would require a large scale decoder.

 

I think a more practical solution will be required before approaching loco manufacturers.

 

It would probably be easier to approach RC manufacturers and get them to make a voltage doubling speed controller - this is not rocket science and some of the early FET based speed controllers for 1/10 and 1/12 scale cars included voltage doublers to give good drive for the FETs which could not be turned on properly at even 8.4V.

 

RC tends to make do with low voltage rather than low voltage being ideal for it. For the most part it is just the radio that runs well at 4.8V or 6V. Higher voltage often helps if you can arrange it.

[fallen]

When thinking about motor voltage and current requirements, voltage equals speed and current equals torque. So low voltage equals slow running.

 

But don't forget that a lot of volts are lost on a traditional layout in the resistances of the wires, the track, the track joints, the wheel/rail contact and the pickups. Also some RTR locos on 12v run faster that you might want for realism. The net effect is that quite a lot of locos, especially in the smaller scales, will run fine on lower voltage applied directly to the motor by the R/C system.

 

Maybe a quick look as various loco mechanisms would find the ones that are easy to use for R/C at lower voltage. You can easily test them by temporarily connecting some flexible wire to the motor and using this to feed directly to the motor sfrom a variable power supply or a DC controller with a voltmeter connected. See how fast they run at say 3v, 6v etc.

 

I model in 009 using mainly n gauge mechanisms. Kato tram chassis are ideal in this scale, they run very nicely with a single cell supply. Used on a normal DC layout at 12v they tend to run too fast for realism or easy control.

 

Frank

[Robin2]

It is simply not true to say that low voltage equals slow running. Also it is much too simplistic to equate voltage with speed and current with torque.

 

For a given performance a machine needs a certain amount of power input. Power is measured in watts and watts = volts x amps. You can deliver 9 watts as 12v x 0.75 amps or as 6 volts x 1.5 amps. The machine wouldn't care which it got.

 

I agree with Suzie that a 9w resistor would be necessary and impractical in the scenario she paints. However I suspect there is considerable scope for using more efficient motors that require less watts. And I guess my mind was focused on N-Gauge where the power requirements are smaller.

 

While I understand the argument for higher voltage it is not practical if there is only space for a single LiPo cell. And voltage doubling isn't really the answer because there will be a higher current draw from the battery - little attention having been given to choosing an efficient 12v motor.

 

Neither my Grafar Crab or Class 101 DMU will run from a single cell so I have to change the motors - because I want all my Locos to work at the same voltage for charging convenience. I did consider squeezing 2 cells into the Crab tender but I concluded that the current draw would be too high using the standard 12v motor.

 

DCC decoders that can handle 1.5 amps aren't unusually expensive, and with a DCC decoder the software could match the DCC input voltage to the motor requirement.

 

...R

[Suzie]

Whether you use a high voltage motor with a voltage multiplier or a low voltage motor the current draw from the battery will be the same. The higher voltage motor will be taking less current from the multiplier to compensate and the power consumed will be the same. Any losses in the multiplier will be offset by the reduced losses in the speed controller which will be more efficient at higher voltage/lower current.

 

The Heljan motor is probably one of the least efficient currently on the market so is a worse case using 9W, but as an example will still use 9W as a 6V version and will need 1.5A from a 6V battery or 3A for a 3V version running from a 3V battery.

 

If you want to look at what a nightmare it is to use 3V motors, try building an efficient power supply to run Dapol signals which use a vast amount of current to drive the 3V motor from a 9V DC or 16V AC supply.

[Robin2]

Susie,

 

I understand about power and I don't disagree with your logic - if one assumes that the motor can't be replaced with a more efficient motor.

 

But my strong suspicion is that more efficient motors are available. If you are designing a product that for all practical purposes has an unlimited supply of electricity there is no need to consider efficiency - especially as the total cost of the electricity is trivial for the end user.

 

Separately from that, a low voltage motor is more convenient for battery power - there would be no need for the inevitable energy losses in a voltage booster.

 

Let's try and find the best examples of low voltage motors rather than dwell on the worst.

 

...R

[SHMD]

12v motors will be hard to dislodge!

 

There is the legacy and compatibility issues to contend with.

And peoples "familiarity" with 12v will provide considerable inertia to change too!

 

Every one, (except collectors), will have 12 compatible equipment.

Some of the controllers will not be compatible with a lower voltage motor + resister combo. Feedback controllers will suffer performance issues as they don't get the feedback they were expecting for example.

 

I'm all for RC but I think this is a none starter despite the initial perceived advantages.

 

 

Kev.

(Soon to start my own "RC adventures" thread! But now motor voltage choice will feature in the design stage so thanks for that.)

 

 

 

[Robin2]

Hi Kev,

 

It'll be great to have another BPR/C disciple. What size trains are you planning to use?

 

...R

[Robin2]

I have changed the title of the topic to "N-Gauge" motors as it shouldn't be a problem fitting 2 LiPo cells into an OO Gauge Loco in order to work with the factory fitted 12v motor.

 

...R

[SHMD]

Hi Kev,

 

It'll be great to have another BPR/C disciple. What size trains are you planning to use?

 

...R

 

Alas I will be 00 based, (and biased), and thus the only common criteria with your self will be RC and the yearning desire to have track independent power.

 

The prototyping stage will use my 2012 innovation entry - SDB.

 

 

Kev.

[StuartM]

Firstly, it seems to me as if there are now several threads all pointing in the same direction, i.e. battery powered Radio controlled locos, I'm not sure if this is a good thing, or if it dilutes the message?

 

 

With regard to low voltage motors...

My battery powered rc loco used a 9v pp3 battery (which is 6x 1.5v battery's all joined together in series and crammed into a neat box)

My Picaxe micro controller only required 5v as did the radio circuit, This required a voltage regulator to be incorporated into the circuit to drop the 9v down to 5v, which was an inefficient use of the limited power available from the battery.

The motor however required at least 9v to get it to move at anything nearing an acceptable speed, because the current supplied by a pp3 is limited regardless of how much voltage is used.

So I think Robin's idea of a low voltage motor is a valid one, but also a low current motor would be advantageous.

As to legacy and control issues....

A battery powered RC loco would be able to run on existing tracks, so no issue there

A battery powered RC loco would require a new rc controller, so again no issue

People could continue to put 12v through the rails if they really wanted to and, could continue running their existing stock while running the BPRC loco at the same time.

Think of it as duel systems, as an example it would be like running windows explorer and firefox on the same pc at the same time.

 

As to contact with the manufactures, write to them, phone them up, email them, they all have contact details on their websites

[Edwin_m]

To re-do Suzie's calculation for N gauge:

 

A typical motor will draw about 300mA at 12V, so 720mA at 5V.  The necessary resistor will need to drop 7V at 720mA which comes to 5 watts.  This is still a largeish resistor bearing in mind how much less space there is inside a N gauge loco.  It could be removeable to make space for some of the other equipment needed if the loco was converted to RC. 

 

With DCC there is less of a problem as long as the 5V motor can tolerate a supply which is a PWM peaking at 12V and with the mark-space ratio reducing this to an average 5V.  Pretty much any present-day decoder can step down the voltage in this way with appropriate CV settings.  This suggests that the best way to run a low-voltage loco on DC layouts would be to fit a DCC decoder which can perform the same PWM operation on DC, which they may be able to do already. 

 

There is clearly a cost issue here.  DC modellers object to paying more for a decoder they "don't need", DCC users might want to replace the supplied decoder with one having more features, and using a more efficient motor would increase costs further if that was necessary (which it may not be with a decoder-based approach). 

 

I would also question whether the motor voltage makes a big difference to the feasibility of RC conversion.  I don't know anything about RC but I do know that N gauge locos have very little solid metal in the chassis block or airspace around it, and the motor and drive gear as presently configured won't leave many convenient battery-shaped spaces.  Could it be that fitting RC to a N gauge loco requires such drastic internal modification that the existing motor can't be re-used in any case?  If this is so then there is no benefit in fitting a lower voltage motor - instead you would need to be lobbying for an internal re-design to produce something with similar cost, reliability and haulage but more space for batteries etc (and a 5V motor too). 

[StuartM]

To re-do Suzie's calculation for N gauge:

 

A typical motor will draw about 300mA at 12V, so 720mA at 5V.  The necessary resistor will need to drop 7V at 720mA which comes to 5 watts.  This is still a largeish resistor bearing in mind how much less space there is inside a N gauge loco.  It could be removeable to make space for some of the other equipment needed if the loco was converted to RC. 

 

With DCC there is less of a problem as long as the 5V motor can tolerate a supply which is a PWM peaking at 12V and with the mark-space ratio reducing this to an average 5V.  Pretty much any present-day decoder can step down the voltage in this way with appropriate CV settings.  This suggests that the best way to run a low-voltage loco on DC layouts would be to fit a DCC decoder which can perform the same PWM operation on DC, which they may be able to do already. 

 

There is clearly a cost issue here.  DC modellers object to paying more for a decoder they "don't need", DCC users might want to replace the supplied decoder with one having more features, and using a more efficient motor would increase costs further if that was necessary (which it may not be with a decoder-based approach). 

 

I would also question whether the motor voltage makes a big difference to the feasibility of RC conversion.  I don't know anything about RC but I do know that N gauge locos have very little solid metal in the chassis block or airspace around it, and the motor and drive gear as presently configured won't leave many convenient battery-shaped spaces.  Could it be that fitting RC to a N gauge loco requires such drastic internal modification that the existing motor can't be re-used in any case?  If this is so then there is no benefit in fitting a lower voltage motor - instead you would need to be lobbying for an internal re-design to produce something with similar cost, reliability and haulage but more space for batteries etc (and a 5V motor too).

Hi Edwin,

regarding the space issue, my idea was to replace the chassis with a chassis shaped battery.

This has all been discussed in the original thread http://www.rmweb.co.uk/community/index.php?/topic/64616-battery-poweredradio-controlled-locos/

We're just repeating ourselves on this one

[Robin2]

I understand and agree fully with Stuart that a Loco designed from the start to be BPR/C could have all sorts of optimizations - including specially shaped batteries. This sort of optimization is what has made the tiny (and cheap) R/C helicopters possible.

However I'm not prepared to wait indefinitely in the hope that model train manufacturers will have a change of heart and I am looking for a step by step approach that will make BPR/C easier to implement without discommoding other users who aren't even interested in DCC.

Edwin suggests that an NGauge loco draws 300mA at 12v. My converted Large prairie draws about 100mA at 3.7v - that's equivalent to 30mA at 12v. Even allowing for a desire to have more power 60mA at 12v  (or 120mA at 6v) should be plenty if some attention was given to having an efficient motor. A resistor dropping 6v at 120mA only wastes 0.72watts (after correcting my maths, courtesy of Edwin).

Edwin also raises the question of space in an NGauge loco for a battery. This is a very valid issue for tank locos but there should be plenty of room in a tender or in a DMU/EMU. And, if I can get a motor and battery into a tank loco Bachmann or Hornby could do it more easily.

...R

[Robin2]

I'm making a separate post about this so it isn't lost in other comments.

 

While thinking about the various comments that have been made so far another answer to the low-voltage motor has occurred to me.

 

Could we persuade the manufacturers to power their locos with a 12v can motor of a size for which there is a low voltage alternative? 

 

This would mean that there is no compromise in 12v performance yet those of us who want a 12v conversion could easily replace the motor with its low voltage counterpart.

 

...R

[Edwin_m]

I understand and agree fully with Stuart that a Loco designed from the start to be BPR/C could have all sorts of optimizations - including specially shaped batteries. This sort of optimization is what has made the tiny (and cheap) R/C helicopters possible.

 

However I'm not prepared to wait indefinitely in the hope that model train manufacturers will have a change of heart and I am looking for a step by step approach that will make BPR/C easier to implement without discommoding other users who aren't even interested in DCC.

 

Edwin suggests that an NGauge loco draws 300mA at 12v. My converted Large prairie draws about 100mA at 3.7v - that's equivalent to 30mA at 12v. Even allowing for a desire to have more power 60mA at 12v should be plenty if some attention was given to having an efficient motor. A resistor dropping 6v at 60mA only wastes 0.36watts (hoping my maths is correct).

 

Edwin also raises the question of space in an NGauge loco for a battery. This is a very valid issue for tank locos but there should be plenty of room in a tender or in a DMU/EMU. And, if I can get a motor and battery into a tank loco Bachmann or Hornby could do it more easily.

 

...R

I think you've lost a factor of two here.  A motor the same size and efficiency as the one mentioned would need 60mA at 6V (ignoring 5V to keep the maths easier).  Double it for more power and you're up to 120mA, and the power dissipation is 720mW.  A bit more do-able as you say, but it's a question of the trade-off in cost and any other issues between an efficient motor with a resistor or any old motor with a DCC decoder or similar reducing the voltage by PWM. 

[Robin2]

Edwin, It certainly wouldn't be the first time I got my maths wrong, but I can't follow your logic?

 

And, separately, what do you think of the idea of being easily able to change the motor?

 

...R

 

 

I think you've lost a factor of two here.  A motor the same size and efficiency as the one mentioned would need 60mA at 6V (ignoring 5V to keep the maths easier).  

[Edwin_m]

Edwin, It certainly wouldn't be the first time I got my maths wrong, but I can't follow your logic?

 

And, separately, what do you think of the idea of being easily able to change the motor?

 

...R

 

You mentioned 60mA at 12V.  But if you are running at 6V you need 120mA to get the same power. 

 

The interchangeable motor sounds like a good idea. 

[Robin2]

Thanks Edwin,  I have corrected my earlier post.

 

I guess my original notion of a dropper-resistor was very impractical. Note to self - do the maths first next time!

 

Let's see if we can get support for interchangeable motors?

 

...R

[Robin2]

Time for more humble-pie, it seems ...

 

I have just successfully replaced the 12v motor in my new class 101 dmu with an identically sized 6v? motor from a servo. From the markings on the rear of the motors they may even have come from the same manufacturer. I must have the servo for 15 years.

 

The complex part was dismantling the class 101 chassis. After that I pushed the two motors out of their gear and flywheel respectively and pushed the flywheel onto the 6v motor.

 

...R

[StuartM]

Time for more humble-pie, it seems ...

 

I have just successfully replaced the 12v motor in my new class 101 dmu with an identically sized 6v? motor from a servo. From the markings on the rear of the motors they may even have come from the same manufacturer. I must have the servo for 15 years.

 

The complex part was dismantling the class 101 chassis. After that I pushed the two motors out of their gear and flywheel respectively and pushed the flywheel onto the 6v motor.

 

...R

Any photos ?

What is the performance like?

[Robin2]

It won't be running for a few days  - I'm waiting for the receiver to arrive.

 

...R

[NorthHighlander]

Hi everyone..

We've just come back from a very successful ExpoEM - our first time at that show and the response from the visitors to Acc+Ess Protocab was great. We were showing 1 x O gauge 'Terrier' (on and off hauling a wagon with a half kilogram weight in it!), a Hornby Dublo 3 rail 'Duchess' hauling 4 very rusty three rail coaches, a Mainline 'Warship' hauling four Mainline BR Mk1 coaches, a Heljan 'Hymek' and 'Crompton' both converted to P4, all operated without any wiring to the track and from three independent controllers. A number of young kiddies with their parents were taking the controls!

All the locos ran for the whole day on each day with the exception of the Duchess which, with its beefy motor tended to drain the battery after around 90 minutes of constant running.

The only calamity was that a length of rail on one of the Hornby Setrack circuits had come adrift in transit to Bracknell (it's a long way from Caithness!). Apart from that nothing untoward except at least two visitors begging us to have the system available for sale! Well, our answer had to be it won't be long, but we won't release anything until fully tested and emc compatible which is our next step. We're just in the throes of finalising and testing the security routines to make sure that one loco can't be controlled from an unauthorised controller and making some design changes to the LCU Interface Unit to simplify charging and on/off switching. There are still some throughput problems to iron out but they won't be too hard.

We had quite a few new members to Club Protocab, so there is lots of interest out there. Next newsletter coming out in a couple of weeks. Also the new website should be up and running before the end of the month.

 

Best regards

 

Tony Hagon

Acc+Ess Ltd

 

Developers of the Protocab wireless model railway control system

protocab.com