Coreless motors v open frame.

[Chris Morris]

I made this bit of video today. It shows how the Dapol 45xx can be tamed with a feedback controller while the coreless motored Farish 2MT is fine with a non feedback controller ( a Gaugemaster W) but noisy and rough when using feedback. Hopefully this illustrates that it is not good to use a feedback controller with a coreless motor but feedback controllers have their place with older cruder mechanisms. Whilst the 45xx is not a really old mechanism it is renowned for being very poor at slow running. The feedback controller, a very old H&M Walkabout, is good for this loco.

[Dr Al]

Bear in mind the 45xx's can motor is very vulnerable to overheating if driven hard by feedback (e.g. it derails or suchlike) - the commutator will disintegrate if it gets too warm from excess driven current (and that level is not very high - something like 200mA). It's nowhere near as robust as some of the much older Farish for example which will only exhibit failure at 400mA+ (albeit this is usually a coil burn out).

Cheers,
Alan

[Dorsetmike]

For a DC controller I've yet to find a better design than one I found in an electronics magazine some years ago; I've not seen a commercial controller using the same principle. I've made a few modifications to the original circuit, at the time I did show it to the Tech man at Farish near Poole (that dates it!) his opinion was that it would not harm Poole Farish motors, I've used it ever since with no problems, slow running control is superb, 5 minutes to cover 12", it even tames Dapol M7s.

When using simple controllers the motors used in many model locos are reluctant to start until the voltage rises above a certain level, but once started this voltage is enough to cause them to leap away in most unprototypical fashion.

This circuit uses a narrow pulse, (about 3ms mark, 12V, 27ms space, 0volts)  that is just sufficient to make trhe motor start to turn, to increase speed the pulse is "mixed" with a DC level; as the speed control is increased the DC level is increased so at low speed the mark remains at 12V but the space rises to say 3v, this will increasethe average current and the motor speed rises, as the control is  increased so the space voltage increases, further increasing the average current, until with control at full the motor is getting a full 12 V.

The circuit uses transistors, diodes and a CMOS chip, it also has a good overload protection circuit.

The full circuit and full description is at

https://www.dropbox.com/s/xm6r72p27iqbqox/controller.pdf?dl=0

[Dr Al]

For a DC controller I've yet to find a better design than one I found in an electronics magazine some years ago; I've not seen a commercial controller using the same principle. I've made a few modifications to the original circuit, at the time I did show it to the Tech man at Farish near Poole (that dates it!) his opinion was that it would not harm Poole Farish motors, I've used it ever since with no problems, slow running control is superb, 5 minutes to cover 12", it even tames Dapol M7s.

When using simple controllers the motors used in many model locos are reluctant to start until the voltage rises above a certain level, but once started this voltage is enough to cause them to leap away in most unprototypical fashion.

This circuit uses a narrow pulse, (about 3ms mark, 12V, 27ms space, 0volts)  that is just sufficient to make trhe motor start to turn, to increase speed the pulse is "mixed" with a DC level; as the speed control is increased the DC level is increased so at low speed the mark remains at 12V but the space rises to say 3v, this will increasethe average current and the motor speed rises, as the control is  increased so the space voltage increases, further increasing the average current, until with control at full the motor is getting a full 12 V.

The circuit uses transistors, diodes and a CMOS chip, it also has a good overload protection circuit.

The full circuit and full description is at

https://www.dropbox.com/s/xm6r72p27iqbqox/controller.pdf?dl=0

Interesting concept Mike - essentially a straight mix of pure DC and pulsing.

Where's the soldering iron.... :-)

Cheers,
Alan

[Chris Morris]

Bear in mind the 45xx's can motor is very vulnerable to overheating if driven hard by feedback (e.g. it derails or suchlike) - the commutator will disintegrate if it gets too warm from excess driven current (and that level is not very high - something like 200mA). It's nowhere near as robust as some of the much older Farish for example which will only exhibit failure at 400mA+ (albeit this is usually a coil burn out).

Cheers,
Alan

My little 45xx (as shown in the video) has coped with many days at exhibitions using the feedback controller and runs the same as it always has.  She still has quite a turn of speed too...

[ntpntpntp]

I made this bit of video today. It shows how the Dapol 45xx can be tamed with a feedback controller while the coreless motored Farish 2MT is fine with a non feedback controller ( a Gaugemaster W) but noisy and rough when using feedback.

It would be interesting to try the 45xx (and indeed the 2MT) on a PWM controller without feedback, to see if the pulsed power is enough to overcome the stickiness without actually needing to adjust the output rapidly via feedback.

Actually I think I've got a 45xx somewhere (was never very impressed with it), I'll dig it out and try it on my KPC with and without feedback.

[ten0G]

My little 45xx (as shown in the video) has coped with many days at exhibitions using the feedback controller and runs the same as it always has.  She still has quite a turn of speed too...

Wow!  Much more impressive than mine on my Kato controller. 

Can you tell me which model it is for comparison please, mine's 2S-014-002.

[Chris Morris]

My little 45xx (as shown in the video) has coped with many days at exhibitions using the feedback controller and runs the same as it always has.  She still has quite a turn of speed too...

Wow!  Much more impressive than mine on my Kato controller. 

Can you tell me which model it is for comparison please, mine's 2S-014-002.

I think the model number is ND-035. You model number suggests it is a later one which may have been geared more sensibly; the gearing was certainly well wrong on the early editions like mine.

[Dr Al]

I think the model number is ND-035. You model number suggests it is a later one which may have been geared more sensibly; the gearing was certainly well wrong on the early editions like mine.

They are all mechanically identical. Any difference will come from the magnetisation of the motor, and the wheelsets (quartering and wheel slippage on the axles is common on these).

Having said that on the ones I've seen there's little difference between batches in terms of performance.

Cheers,
Alan

[Old Crow]

Lots to think about for a newbie, quite happy with dc. I'm using a simple Gaugemaster Combi at the moment and all my stuff is open frame and pre-owned. Other than the odd rogue loco with issues I have pretty fair running even with an old clunker with brass gears. Interested to try a new loco, which I'd rarely run continuously for 10 -15 minutes anyway. Hopefully if a new loco ran ok during it's warranty period it should continue to do so?

[Dr Al]

Interested to try a new loco, which I'd rarely run continuously for 10 -15 minutes anyway. Hopefully if a new loco ran ok during it's warranty period it should continue to do so?

I think you are massively overanalysing this - these motors have been around in locos for a good few years with virtually no reported failures.

So just buy the loco you fancy, and run it.

Cheers,
Alan

[Chris Morris]

Interested to try a new loco, which I'd rarely run continuously for 10 -15 minutes anyway. Hopefully if a new loco ran ok during it's warranty period it should continue to do so?

I think you are massively overanalysing this - these motors have been around in locos for a good few years with virtually no reported failures.

So just buy the loco you fancy, and run it.

Cheers,
Alan

Agreed. The Gaugemaster should be fine for all.

[Bramshot]

One of my coreless motors in a Princess Coronation just developed a fault. It runs erratically at very low speed, so that when starting a loco, it gives all the symptoms you might expect from a loco with jamming mechanism, muck in gears and so on. Starts then stops, whizzes away, stops. After checking the mechanism for binding, I removed the motor and ran it with the worm disengaged, and the motor itself exhibited the same behaviour with no load. I suspected the decoder at first, as this loco had recently been converted to sound, but after testing with a spare Dapol A4 motor, it seems the decoder is fine. So I have a replacement motor on order. @Dr Al, can you tell me if the motors are supplied by Bachmann with the worm fitted, or do I have to take the worm from the existing motor? If so, how is it removed / replaced?

[Dr Al]

I'd check the motor on DC - DCC is a pain for diagnosing problems.

In terms of Bachmann - I'd presume they'll come with a worm. Mine didn't, but weren't bought from Bachmann, so a worm puller was needed to switch over the worm from the old motor.

Cheers,
Alan

[Bramshot]

In terms of Bachmann - I'd presume they'll come with a worm. Mine didn't, but weren't bought from Bachmann, so a worm puller was needed to switch over the worm from the old motor.

Where do you get yours from? £19 from Bachmann, but I didn't find any alternative source on line.

Hoping it comes with the worm as I do not have a puller!