Do you agree with this assessment of the Hammant and Morgan controllers ?

[AndyID]

 The H&M Duette has wire wound potiometers in reality.

 

That's a new one on me, but I'm pretty sure they were actually rheostats

[Crosland]

The big difference in practice between Variable Transformers and Variable resistors in where gradients change, 

 

As has been explained before, a simple variable resistor as speed control has very poor regulation.

 

Set if for a reasonable speed uphill. When going downhill the loco draws less current, the resistor drops less voltage so the loco gets a higher voltage and runs away.

[AndyID]

As has been explained before, a simple variable resistor as speed control has very poor regulation.

 

Set if for a reasonable speed uphill. When going downhill the loco draws less current, the resistor drops less voltage so the loco gets a higher voltage and runs away.

Just to add that "regulation" maintains the output at a constant voltage regardless of the current drawn by the motor. If the motor had no internal resistance and it was supplied from a constant voltage it would maintain constant speed on any gradient.

 

Unfortunately, even with perfect regulation the motor's internal resistance reduces the speed as the load increases while climbing gradients but it's not difficult to make a controller that effectively cancels out a motor's internal resistance.

[RJS1977]

As has been explained before, a simple variable resistor as speed control has very poor regulation.

 

Set if for a reasonable speed uphill. When going downhill the loco draws less current, the resistor drops less voltage so the loco gets a higher voltage and runs away.

 

But isn't that precisely what would happen with a full-sized loco? If the driver of a steam loco set the regulator in the same place going downhill as he would going uphill, his loco would run away too....

[AndyID]

But isn't that precisely what would happen with a full-sized loco? If the driver of a steam loco set the regulator in the same place going downhill as he would going uphill, his loco would run away too....

Not really. Even if he closed the regulator the train would keep on rolling and probably accelerate. Because model trains have so much friction they stop dead when the power is cut (unless they have serious flywheels).

[Junctionmad]

That's a new one on me, but I'm pretty sure they were actually rheostats

Don't think so , haven't opened the club one , but I have cit hit for a clipper and that's a pot

[AndyID]

Don't think so , haven't opened the club one , but I have cit hit for a clipper and that's a pot

 

You are right.

 

It's a pot that's used as a rheostat for low-resistance motors and as a potential divider for high-resistance motors. I think that improves the voltage regulation for high-res motors.

[AndyID]

You are right.

 

It's a pot that's used as a rheostat for low-resistance motors and as a potential divider for high-resistance motors. I think that improves the voltage regulation for high-res motors.

 

But I'm not sure why they bothered to include the switch!

 

If the pot can dissipate the power with no load when the switch is closed, what's the benefit in opening the switch? A small amount of current will no longer be shunted though the pot bypassing the motor, but that's about it. What am I missing?

[RJS1977]

Not really. Even if he closed the regulator the train would keep on rolling and probably accelerate. Because model trains have so much friction they stop dead when the power is cut (unless they have serious flywheels).

 

However you would not expect a train (whether model or full-size) to run nicely at the same speed down a gradient as you would up it without some form of manual intervention, which seems to be what people are expecting from their controllers. Agreed though that a controller and a regulator are not directly analagous.

[Junctionmad]

Not really. Even if he closed the regulator the train would keep on rolling and probably accelerate. Because model trains have so much friction they stop dead when the power is cut (unless they have serious flywheels).

The main reason it stops dead is the use of a one way worm drive , I once saw a helical gearbox engine plus train overrun quite spectacturly.

Edited October 9, 2017 by Junctionmad

[Junctionmad]

Then why doesn't somebody do just that ? I found that the old H&M gave much better slow speed control than anything made by Hornby or Bachmann. I am referring to DC of course as I have no experience with DCC. Perhaps the manufacturers have lost interest in improving their DC controllers now that DCC is everywhere.

Yes DC is a declining market.

 

But the fact remains , with a few basic components ,( for example a LM317, or a LT3081) you can make a controller with a regulated output , that's far better then the H& M stuff ever was. that still leaves even more sophisticated controllers with PWM and or feedback to consider , circuits for which are widely available

 

Gauge master still do a good range of dc controllers, and our club has a Morley dc one

 

There really nothing inside the H&M of any noteworthy value , it it a design from the 60s, I bought my first Duette from Millholme Models 1969 , I believe

Edited October 9, 2017 by Junctionmad

[AndyID]

The main reason it stops dead is the use of a one way worm drive , I once saw a helical gearbox engine plus train overrun quite spectacturly.

 

True. Worm drives produce a lot of friction, but they are not always one way. I have an ancient Tri-ang motor bogie with nylon worm wheels and I can turn the motor by rotating the wheels. Mind you, that's partly because it's a two-start worm so the reduction ratio isn't large. Also the magnet needs to be replaced.

[Junctionmad]

But I'm not sure why they bothered to include the switch!

 

If the pot can dissipate the power with no load when the switch is closed, what's the benefit in opening the switch? A small amount of current will no longer be shunted though the pot bypassing the motor, but that's about it. What am I missing?

Wasn't it a crude attempt at better resistance matching. The trouble with a simple pot is lower impedance higher current motors effectively shorted the pot out and largely in effect turned it into a rheostat anyway. Personally I found bigger difference with the switch in either direction

 

But yes the switch largely did nothing other then saving some dissipation in the lower leg, which is perhaps why they included it. Merely to prevent more loss of transformer regulation with larger motors.

Edited October 9, 2017 by Junctionmad

[AndyID]

Wasn't it a crude attempt at better resistance matching. The trouble with a simple pot is lower impedance higher current motors effectively shorted the pot out and largely in effect turned it into a rheostat anyway. Personally I found bigger difference with the switch in either direction

 

But yes the switch largely did nothing other then saving some dissipation in the lower leg, which is perhaps why they included it. Merely to prevent more loss of transformer regulation with larger motors.

 

Agreed. I think it's an "operator feelgood" switch.

[roythebus]

I've still got an H&M Duette in service that I bought in about 1966 from my first job at Patricks Toys in Fulham. It has the high/low resistance switch as well as half-wave rectification for very slow running. Some motors perform well at one resistance setting, others don't, hence the flexibility.

 

I lso have a 1950s grey box H&M power supply unit in service on my layout; that gives 16v ac at about 5 amps, so can pack quite a punch for accessories. I use it with a home-made diode matrix to run my Tortoise point motors.

 

Maybe the only duff units H&M ever made were their early transistor hand-held controllers which we tried on the MRC's New Annington layout in the early 1980s. They didn't last a week of exhibition use and were replaced by Gaugemaster hand-held units.

[Junctionmad]

The H&M resistance mat controllers, were very much a product of the times,  before being swept away by cheap and more effective electronic controllers.  I remember around 1977 replacing my Duette, which I had received when I was 9 years old in 1969!, with electronic controllers built from a kit ( and very nice they were too) .  MY mother threw out the Duette is a house move  many  years later !!  ]

 

Our club still uses theirs on the test track and it performs " adequately " , 

 

robust √

easy to use √

good on modern motors Ø

good slow speed control Ø

 

my old PYE valve radio also works too, but I listen to my radio via the internet today !!!, electronics have no nostalgia value quite frankly 

Edited November 6, 2017 by Junctionmad

[thestourbridgelion]

Interesting thread. Does anyone know anything about H&M the company? Surely they made other electrical items other than Model Railway controllers. When did they start out and when did they go bust (I assume they stopped manufacture before Hornby took the name)

[AndyID]

Interesting thread. Does anyone know anything about H&M the company? Surely they made other electrical items other than Model Railway controllers. When did they start out and when did they go bust (I assume they stopped manufacture before Hornby took the name)

 

There's a bit more information here http://www.binnsroad.co.uk/railways/handm/index.html

 

As far as I know they only made electrical equipment for model railways. I first became aware of them from ads in the RM in the 50's. I always wanted to buy one of their controllers but my pocket money wouldn't run to it

[roythebus]

Having just picked up on this thread again, I've recently replaced my original H&M Duette with a slightly later Duette, maybe an early 1970s model, almost identical to the original. Having recently acquired some very modern hi-tech locos like the Oxford Adams Radial, the Kernow Well Tanks and the like, I have to say they work remarkably well with this old DC technology. Nice slow running and a good turn of speed.

 

What I dislike about DCC is that to get anything to go I have to remember a series of numbers and buttons to press to make something go. I like to be able to look at switches on a panel, switch them on, turn the knob and the train goes. 

 

Having seen the wiring on a modern bus compared to the wiring on a vintage bus I've found that on a modern bus there's about 1km of wire; on a similar size old bus it's about 300m and no very expensive ECUs to go wrong. I though DCC was supposed to make wiring simpler.

[DCB]

 

Having seen the wiring on a modern bus compared to the wiring on a vintage bus I've found that on a modern bus there's about 1km of wire; on a similar size old bus it's about 300m and no very expensive ECUs to go wrong. I though DCC was supposed to make wiring simpler.

 

 

DCC does make wiring easier, when used correctly.  Picture a typical American basement, about 20ft X 40ft, 100 ft of track per circuit, maybe looped round so there are 200 or 300 ft of track,  Several operators running different trains on basically a long single track various loops and sidings to negotiate while crossing other trains in the single track. Trains with up to.5 locos on the front of a 20 car train (representing a 100 car train).    Try doing that with DC.  Also busy loco depots, lots of Diesels idling. Try that with DC.  However for running trains and playing signalman it is probably more hassle than its worth.

 

As has been explained before, a simple variable resistor as speed control has very poor regulation.

 

Set if for a reasonable speed uphill. When going downhill the loco draws less current, the resistor drops less voltage so the loco gets a higher voltage and runs away.

But a variable transformer, Autotransformer, provides a largely constant voltage but amperage varies with load so locos with efficient motors more or less run at constant speed uphill, downhill and even when slipping at the end of a siding and trying to demolish a buffer stop. with inefficient motors they wont run smoothly downhill due to the worm drives but the half wave switch cures that by making the motor run rough which stops the worm drive winding up.

[brian777999]

Having just picked up on this thread again, I've recently replaced my original H&M Duette with a slightly later Duette, maybe an early 1970s model, almost identical to the original. Having recently acquired some very modern hi-tech locos like the Oxford Adams Radial, the Kernow Well Tanks and the like, I have to say they work remarkably well with this old DC technology. Nice slow running and a good turn of speed.

 

 

 And 12 o'clock is off.....reverse is to the left and forward is to the right : I find this so much more intuitive than the forward/reverse switch that most DC controllers have. 

[AndyID]

And 12 o'clock is off.....reverse is to the left and forward is to the right : I find this so much more intuitive than the forward/reverse switch that most DC controllers have.

 

Same here. It's not as if it's very difficult to make electronic controllers operate that way although it is a bit more expensive, but not much.

 

Might be interesting to take a poll to see how many others agree.

[DLT]

DCC does make wiring easier, when used correctly.  Picture a typical American basement, about 20ft X 40ft, 100 ft of track per circuit, maybe looped round so there are 200 or 300 ft of track,  Several operators running different trains on basically a long single track various loops and sidings to negotiate while crossing other trains in the single track. Trains with up to.5 locos on the front of a 20 car train (representing a 100 car train).    Try doing that with DC.  Also busy loco depots, lots of Diesels idling. Try that with DC.  However for running trains and playing signalman it is probably more hassle than its worth.

 

That is of course, precisely what DCC was created for.  It would be very difficult with conventional DC control.  But using that same control method on a "one engine in steam" branchline terminus to fiddle-yard seems over the top to me. 

But then if its part of a larger system, or your locos are already dcc fitted, or you want sound etc, then that's the way you go.   I'm certainly not against DCCC, but I see the choice as Horses for Courses.

 

 

 And 12 o'clock is off.....reverse is to the left and forward is to the right : I find this so much more intuitive than the forward/reverse switch that most DC controllers have. 

 

My personal preference is for a handheld with a speed knob and a direction switch, I use mainly Gaugemasters.  You can operate one-handed, and you don't have to look at them; you can't easily do that with the mass of buttons that make up many DCC controllers.

 

Back on the subject of H&M, my Duette (circa 1965) is now normally used as a power-supply, but I still occasionally run trains with it.  Set on full-wave and high-resistance it controls my Portescap and Mashima powered locos beautifully.

 

Cheers, Dave.

[Junctionmad]

 

Having seen the wiring on a modern bus compared to the wiring on a vintage bus I've found that on a modern bus there's about 1km of wire; on a similar size old bus it's about 300m and no very expensive ECUs to go wrong. I though DCC was supposed to make wiring simpler.

 

A modern bus has vastly more facilities  to control and power,  mood lightening , air conditioning , safety systems, environment systems, etc etc etc , in fact without can bus and other computer systems, there would likely be 10Km of wires in a new bus 

Edited February 21, 2018 by Junctionmad

[Junctionmad]

 

 

 However for running trains and playing signalman it is probably more hassle than its worth.

I respectfully disagree