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

[Junctionmad]

P1010002.JPGHi All

Attached is a pic of the rheostat of the Duette that I tried to load in my last post.

 

The Clipper uses a potentiometer , I presume the Duette is the same, a rheostat is a two terminal variable resistor 

[Nearholmer]

Rheostats are usually made from nichrome wire, which is very good for its temperature stability both mechanically and electrically.

 

This is in interesting discussion, but I do think that 'they are what they are', technology that was very good for its time, but has been superseded by more recent technology that can do the job better and/or cheaper.

 

I'm a great fan of old landrovers, having had a series one and a series three, and H&M kit is a bit the same: so well built that it still does what it was able to do when it was built, donkeys years on. But, if you inflated the price from, say, 1970 to now, you'd be astounded by how expensive they were at the time, and they can't do what the modern equivalent can do.

 

Kevin

[Crosland]

Don't ask me why we don't have potentiostats or rheometers

 

A potentiometer is used as a potential divider to create a variable voltage. What most people recognise as a potentiometer will be low power and require some form of amplifier to be used for controlling trains. You might (in very simple terms) use a pot to set the base voltage on a power transistor.

 

A rheostat is simply a variable resistor. You can turn a potentiometer into a rheostat by connecting the wiper to one end of the track.

 

Common usage these days seems to be that anything large, open and wound from wire is a rheostat and anything small and encased is a potentiometer, but it doesn't have to be so.

 

Andrew

[Dunsignalling]

H&M products (in good nick) are very good all-round controllers, but they do work best with locos of similar vintage.

 

This is from someone who still regrets doing a swap deal involving his virtually mint Duette about ten years ago............

 

John

[RJS1977]

Rheostats are usually made from nichrome wire, which is very good for its temperature stability both mechanically and electrically.

 

This is in interesting discussion, but I do think that 'they are what they are', technology that was very good for its time, but has been superseded by more recent technology that can do the job better and/or cheaper.

 

I'm a great fan of old landrovers, having had a series one and a series three, and H&M kit is a bit the same: so well built that it still does what it was able to do when it was built, donkeys years on. But, if you inflated the price from, say, 1970 to now, you'd be astounded by how expensive they were at the time, and they can't do what the modern equivalent can do.

 

Kevin

 

But using an old controller you already have is a lot cheaper than buying a new one!

[kernowtim]

I traded in my boxed h&m duette controller I bought new, h&m smooth hour power supply,a secondhand Hornby r900 with slave and a couple of triang controllers for the then new Hornby zero1 controller and loco decoders (chips). In retrospect not my best move!!

Did replace the duette with another one later on, but a secondhand gauge master controller did give far better slow speed control.

Zero 1 stuff went on eBay years later, didn't make much on it ;-)

[DCB]

There are two distinct breeds of H&M Controllers, the variable transformers, Safety Minor etc, and variable resistor such as the Duette.    Apart from the words "Variable Transformer" on the front you can tell which is which with a voltmeter. The off load voltage on the variable transformers varies from a few volts at minimum power setting to around 15 volts at Max.  The off load voltage of the variable resistor is around 19 volts irrespective of control setting. The variable resistors usually have 2 switches per control knob, half wave and high/ low resistance, the variable transformers just a Half wave switch or "Variwave" slider. I'll let Crossland explain how that works because I don't have a clue.

It is the variable transformer which earned the reputation for superb slow running but they were very expensive to make, I use three "Safety Minor"s and they are great for everything from a Hattons 14XX to a Triang Hall the only downside is limited top speed and power on gradients, They give very good speed stability up hill and down dale and allow double heading of most RTR including a Triang Hall and a Bachmann Hall, which a Duette will not, and also allow the Triang mechs to run smoothly down steep hills using the half wave, something their replacements, Morley and OnTrack electronic units will not.

So a Variable Transformer is a brilliant piece of kit while the Duette was ok in its day (1970s) it but which may well contain asbestos.   I scrapped mine.  Kept the transformer, binned the rheostats and rectifers.

[Junctionmad]

to be honest , a couple of bobs worth of electronic components , these days produces a controller thats better then the H&M stuff ever was. 

Edited October 6, 2017 by Junctionmad

[Nearholmer]

Well put.

[Clive Mortimore]

It beats me that railway modellers are happy to use 50 year old controllers. Would the same people be happy with a 50 year old electric shaver or electric bar fire? Think before buying or using old electrical equipment.

[AndyID]

It beats me that railway modellers are happy to use 50 year old controllers.

It beat me 50 years ago even when they were new

[sharris]

Not sure I've got anything quite that ancient, but my 30 year old CD player and 35 year old speakers still sound good.

[AndyID]

Blimey! This thread started a long time ago. Going back to the link referred to in the first post "Do you agree?" No, I don't.

 

The author of that link describes H&M variable transformers as "autotransformers". I never owned an H&M variable transformer controller but I'm pretty sure they never used anything as dangerous as an autotransformer. Like really old TV sets autotransformers provide no isolation and if you happen to connect them to the mains the wrong way, the track on your layout could be at a lethal potential of 230 volts.

 

I believe the variable transformer is really a sort of "multi-tapped" transformer. When you rotate the controller knob you are selecting different taps on the transformer's (isolated) secondary winding. That provides a reasonably well regulated voltage, but you can get much better voltage regulation with an electronic controller.

[Crosland]

It beats me that railway modellers are happy to use 50 year old controllers. Would the same people be happy with a 50 year old electric shaver or electric bar fire? Think before buying or using old electrical equipment.

 

SWMBO is still using a 32 year old hair dryer. I still have 30 yr old B&D power tools that I can't bring myself to throw away as they still work, and see occasional use.

 

When did rubber insulation stop being used? Must be getting on for 50 years. There's nothing inherently wrong with old equipment. It's how it's been used (or abused) in those years, and the quality when new, that needs to be considered.

[Crosland]

I believe the variable transformer is really a sort of "multi-tapped" transformer. When you rotate the controller knob you are selecting different taps on the transformer's (isolated) secondary winding. That provides a reasonably well regulated voltage, but you can get much better voltage regulation with an electronic controller.

 

I would have agreed until I read this from RS http://uk.rs-online.com/web/generalDisplay.html?id=infozone&file=electronics/variable-transformers "Variable transformers are a type of autotransformer, which is a transformer that does not have the dual-coil core design. " i.e. no isolation.

[locomad]

It beats me that railway modellers are happy to use 50 year old controllers. Would the same people be happy with a 50 year old electric shaver or electric bar fire? Think before buying or using old electrical equipment.

Yet most of my locomotive stock is well past 50 years old and I reckon will still going strong in 50 years time same for the controllers

 

Course I would be happy to use 50 year old electrical stuff because i think it's generally safer than this cheaply made poor quality poor standard juck we are sold or forced to buy now.

 

In the last 5 years I've had endless issues with new electrical stuff that's failed within a couple of months a couple of what could have been serious house fires due to mobile phone chargers over heating, and worse a kitchen fire due to a new b&q extractor fan catching fire only 3 weeks old. The old kitchen fan still works after 40 years only replaced cause it looked old.

 

Don't get me talking about vacuum cleaners, my lady friend just shown me a burned out pathetic 900 watt load of junk built in only 6 weeks old, she was never satisfied it worked just didn't seem to pick up anything. Yet my hoover constellation purchased by my grandma in the late 50's is still going strong and it's on its 8th house,feel far safer using that than anything sold today.

 

Then there's my grandads car battery charger at least 70 years old still working and I feel safer leaving that on all night than the last car charger I purchased, now a pile of melted plastic

[Nearholmer]

Not all variable transformers provide isolation between primary and secondary. This is a pretty good examination of the most commonly encountered ones, Variacs, and worth a read through http://sound.whsites.net/articles/variac.htm

[AndyID]

Yes, variacs are auto transformers and typically they provide no isolation.

 

I'm pretty sure H&M would never have put out a product that did not isolate the output from the line (mains). We'd probably have heard about the fatalities by now. If someone has a H&M perhaps they could test the isolation and let us know?

 

Andrew, the file in that link doesn't seem to exist. Possibly a geographic block?

 

Andy

[Crosland]

Andrew, the file in that link doesn't seem to exist. Possibly a geographic block?

It was a page, rather than a file, but the same google search (but on a different PC) no longer finds it, either. Sorry about that.

[N15class]

The duette has double insulation the control is through a wire wound variable resistor that is separated from the transformer.

[Junctionmad]

SWMBO is still using a 32 year old hair dryer. I still have 30 yr old B&D power tools that I can't bring myself to throw away as they still work, and see occasional use.

 

When did rubber insulation stop being used? Must be getting on for 50 years. There's nothing inherently wrong with old equipment. It's how it's been used (or abused) in those years, and the quality when new, that needs to be considered.

Never said there was anything " wrong " with old H &M controllers. One does sterling work in our club ( Duette ")

 

What I said was basically you can make a far better controller these days with a handful of cheap electronic components.

 

Personally my modern day electronics lasts very well for the low prices we pay.

[brian777999]

Never said there was anything " wrong " with old H &M controllers. One does sterling work in our club ( Duette ")

 

What I said was basically you can make a far better controller these days with a handful of cheap electronic components.

 

 

 

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.

Edited October 8, 2017 by brian777999

[DCB]

I have somewhere in the back of my mind the idea that H&M had to cease selling the Variable Transformers due to a change in regulations, probably in the 1970s so they could well be Autotransformers with the attendant dangers if connected backwards.  It would be good if someone (else) could have one apart and check with a multitester.

 

It may be technically incorrect but for me a Rheostat is wire wound and has a number of steps in its variable resistance as the wiper moves across the winding, several hundred perhaps, while a Potentiometer (pot) has a carbon track giving a seamless change. Some of the old wire wound rheostats are so coarse you can be stuck between too slow and too fast.

 

The big difference in practice between Variable Transformers and Variable resistors in where gradients change, Set so my trains climb my gradients on a Duette or similar the the trains race back down the other side like a rocket, set to run down the gradients they stall when confronted with the climb.  On the Variable Transformer the track voltage stays much more constant and the speed remains reasonable downhill when set so the trains climb the gradients.  Morley and OnTrack electronic controllers also display this feature plus have very light 3 wire handheld slaves so that why I use them.  

For shunting I prefer a Minic hand throttle as my super low geared Gronk only really has two speeds and goes everywhere flat out.

[Junctionmad]

I have somewhere in the back of my mind the idea that H&M had to cease selling the Variable Transformers due to a change in regulations, probably in the 1970s so they could well be Autotransformers with the attendant dangers if connected backwards. It would be good if someone (else) could have one apart and check with a multitester.

 

It may be technically incorrect but for me a Rheostat is wire wound and has a number of steps in its variable resistance as the wiper moves across the winding, several hundred perhaps, while a Potentiometer (pot) has a carbon track giving a seamless change. Some of the old wire wound rheostats are so coarse you can be stuck between too slow and too fast.

 

The big difference in practice between Variable Transformers and Variable resistors in where gradients change, Set so my trains climb my gradients on a Duette or similar the the trains race back down the other side like a rocket, set to run down the gradients they stall when confronted with the climb. On the Variable Transformer the track voltage stays much more constant and the speed remains reasonable downhill when set so the trains climb the gradients. Morley and OnTrack electronic controllers also display this feature plus have very light 3 wire handheld slaves so that why I use them.

For shunting I prefer a Minic hand throttle as my super low geared Gronk only really has two speeds and goes everywhere flat out.

It is as you say , incorrect, a rheostat is a 2 terminal variable resistor whereas a potentiometer is a three terminal component. ( which can be wired as a rheostat ). The H&M Duette has wire wound potiometers in reality.

 

But hey rule 0 applies , it's your railway , you can call LEDS transistors and your uncle your aunt.

Edited October 8, 2017 by Junctionmad

[AndyID]

I have somewhere in the back of my mind the idea that H&M had to cease selling the Variable Transformers due to a change in regulations, probably in the 1970s so they could well be Autotransformers with the attendant dangers if connected backwards.  It would be good if someone (else) could have one apart and check with a multitester.

 

What you are referring to is the requirement for double-insulated transformers which is entirely different from isolated versus non-isolated transformers. H&M's earlier products didn't use double insulated transformers and the chassis of their controllers were supposed to be earthed.

 

Later models were double insulated, but I don't know whether or not they produced a double-insulated variable transformer version. They may well not have.

 

Here's a link that shows many of their controllers. You can see that the newer models are clearly marked "CLASS IIB DOUBLE INSULATED" and "NO EARTH REQUIRED".