Loco gearing

[Stan]

Hello.
I've recently started modelling with N gauge. At the moment I just have a simple 2-track oval,connected by points, with a single (Bachmann) DC controller. I am gradually collecting some locos, and one thing I've noticed is that the gearing of N gauge locos seems to vary widely.

My latest purchase is the Dapol Class 122 bubblecar, it's a lovely model and has excellent low speed crawl, but with the controller at maximum it has a scale speed of approx 200mph, 3 times the max of the real loco!

There are 2 problems with this - if I have another model on the other loop, with the 122 at, say, 30% scale speed, the other loco will probably be below it's slowest running speed.

Also the lights on the 122 obviously need a certain voltage to operate. At slow speeds they do not illuminate. If the loco was geared lower the lights would operate at a slower speed.

Is there a good reason for this gearing, or is it just a design error by Dapol?

[ntpntpntp]

Solution: get a second controller for the other loop

Yes some locos do run a bit fast, others are beautifully geared to suit realistic running.  Early Dapol locos such as the little 14xx tended to be a bit of a "jack-rabbit" although my example's actually not bad. 

As for speed and gearing differences, I think it tends to be down to the motors available at design time which are within the physical size requirements and within the budget, and what geartrain can physically fit within the design and provide a usable speed range. Gears tend to be MOD 0.3 or 0.4 in standard sizes. Did you watch the "Hornby A Model World" series on TV? Brings to mind the episode where they found the original choice of motor just wasn't right for a new model being designed, and they had to change to a motor with a different speed range.  It's quite common for there to be motors with the same can size but different voltages and speeds, and of course different costs. 

The controller design you use obviously has an effect too - for example older PWM controllers can give old locos beautiful slow starts and smooth running, whereas the same controller used with a modern coreless motored loco may not be so smooth.  Feedback controllers may be even worse with coreless motors.   Recently I've tried and come to like the Kato SX controllers. So far they've given good results with everything I've tried from many brands and both old and new models.


Mostly I run European N models from the "quality" brands such as Fleischmann, Minitrix, Arnold, Roco etc. and I find there aren't so many "speed demons"  

Just this evening I dug out three old 1970s sets from my shelf just to give the locos a run and "stir the oil".  They're as smooth as silk, even an ancient German electric loco dating from the late 60s ran as beautifully as any modern model and I'd happily run it on my exhibition layout (maybe not the coaches though, they are old "shorty" toys )

[PLD]

Its absolutely NOT a "design error by Dapol"...
Not all controllers output the same power (voltage and waveform) so the same loco will perform differently on different controllers. It could be user error in choosing an unsuitably over-powered controller...


If the 121 runs faster than another loco for the same controller setting, its probably more an indicator of good design in the form of a more efficient motor and lower loss through resistance in the gear train.
If you want two locos running at the same time, normal practice is to have two separate controllers so that you can control them individually and adjust individually to suit the characteristics of each loco...

In any case, if the loco is running faster than you want, you don't have to run it at the controller's maximum - the clue is in the name - you adjust it as necessary to control the motion of the train. You could say it just needs the operator to apply a little self-control...

[tunneroner61]

The Bachmann controller is well known to provide 'too many' volts to the track. You can compensate for that by not turning it up too high. Or better still get a Gaugemaster unit. And as ntp says use two controllers so you can run each loop independantly.

[Bealman]

I have a Kato SX controller and must say I'm impressed with it - for what that's worth.

If you have two loops, you really need two controllers so you can emulate two track mainline running in different directions.

That would solve the speed problem too.

[Stan]

Thanks for the replies - all very helpful.

I am planning to get a dual controller soon, probably a Gaugemaster, although I will have a look Kato.

But that would still mean the lights would not work at slow speed, so I still think it would have been a better model if it was lower geared 

[ntpntpntp]

Not necessarily, again it depends on the controller. PWM controllers are better at getting LEDs to light at lower voltages due to the peaks of voltage in the pulses. 

You do have to accept that the move to LEDs instead of filament bulbs means that there needs to be a minimum voltage for them to light (let's say probably around 3V) but the advantage is a properly designed lighting circuit for LEDs will have a resistor and maybe a zener diode so that once that minimum voltage is reached the lights will remain reasonably constant brightness over the speed range.  Filament bulbs tended to need quite a high voltage to get reasonable brightness.

The Kato SX has PWM output and is marketed as allowing your lights to come on before movement.  I've not measured it but the PWM seems to be more gentle (or maybe higher frequency) than other PWM types I've used.

[Firstone18]

Thanks for the replies - all very helpful.

I am planning to get a dual controller soon, probably a Gaugemaster, although I will have a look Kato.

But that would still mean the lights would not work at slow speed, so I still think it would have been a better model if it was lower geared 

Do have a look at Morley controllers https://www.morleycontrollers.com/shopdisplayproducts.asp?id=8&cat=Controllers; many I know who have one rate them very highly, and they are UK made. not a flashy looking as others maybe, but very well designed electronics, and in my experience better included facilities e.g. 'walk about' handset and CDU. I have no connection to Morley, just appreciate their quality - I'm DCC throughout. HTH.
Cheers!

[tunneroner61]

If you want the loco lights to be on at a slow speed, or stationary even, then you should look at going to DCC control.

[Stan]

Some interesting info - thanks!

At the moment I don't intend to go to DCC, although that could possibly change in the future.

The Morley controllers look interesting. I will definitely be getting a dual controller, and although the Morley has a cottage industry look, I find the Gaugemasters to be a bit "industrial" looking for my liking.

The mention of PWM is interesting, I recently bought a low cost PWM controller (available on the usual sites and recommended by some on Youtube for model railway control).

I've now tried it and locos seemed to run well, and the lights on the 122 came on at very low speed.

Some doubts though - the Youtubers show it being powered by a cheap Chinese 12V wall socket. I don't like the idea of relying on that for isolation from the mains...

Obviously I could use an isolating transformer, or buy the Kato, but 2 of those plus PSU's would be an expensive option.

Also I've seen contrasting opinions on whether or not PWM is suitable for coreless motors.

So more research needed!

[ntpntpntp]

Also I've seen contrasting opinions on whether or not PWM is suitable for coreless motors.

Every DCC decoder uses PWM to drive the motor.  They can be used with coreless motors if the correct settings are employed.  It tends need a higher frequency PWM than you find in standalone model railway controllers, and also if feedback back-EMF ("load control") is turned on in the decoder it needs to be tuned differently to the settings for an iron cored motor.

I don't know what frequency the little PWM driver modules on ebay use.  I have used one to drive a funicular railway's capstan motor but not used one with a loco.   I'd be more concerned with what overload cut-out provision is possible with those PWM drivers? Do they have a cut-out? Do they rely on the power supply?

I'd suggest don't skimp on the controller(s).  Get something designed for model railways and N gauge in particular.

[Steven B]

I'd suggest don't skimp on the controller(s).  Get something designed for model railways and N gauge in particular.

Agreed. Too many people will happily spend £100s on locos but then want to spend next to nothing on a controller (and then wonder why their loco runs poorly).

Kato, Morley and Gaugemaster have good reputations for a reason!

Steven B

[Kaput]

Low frequency PWM is bad for coreless motors.

High frequency PWM (which most modern DCC decoders use) is fine for them.