Stay alive and DC - silly question?

[kevinlms]

1 hour ago, Barclay said:

Had a quick look at the online index and got lucky - it was issue 109 - an article called 'The electronic flywheel' by Adrian Newson. Not at home at the moment but will check it out later.

Some more references for you. Note most are conflicting comments. Make what you will from them.

 

MRJ No.(109):52  

MRJ No.(111):159  

MRJ No.(115):319  

MRJ No.(117):78  

MRJ No.)120):198  

MRJ No.(121):239  

MRJ No.(122):279  

MRJ No.(123):318

[Barclay]

He worked in 7mm, used 2 x 470 microfarad capacitors, (36 volt, non-polarised) and with RG7 motors achieved a run-on of 1/3 of a loco length, which shows what you're up against. Having said that it's enough to stop it stalling that's for sure. I hope this helps the OP but I  don't think it's for me!

[OldTom]

Thanks for all the references! 

 

A keep alive could allow simplification of wiring at points, where the frogs are unnelectrified.

 

The main issue with current drives and controllers (including DCC ?) is the resulting motion is not smooth enough (ie is unrealistic) at very slow (ie at realistic) speeds.  It seems to me that improved bearings and increased real inertia through flywheels, of course with improved pickup, could be the answer.

 

I remember (1959\1960?} speaking to the late great Syd Stubbs at the Manchester model railway show where his locos crawled along so impressively smoothly hauling trains at very slow speeds. He used a high voltage (I think it was 24v) because he reckoned it cut through the oxidation and dirt on the track better than the then standard 12v.

 

Measuring the smoothness of motion is an interesting challenge!

[JohnR]

I think I am right in saying (but am prepared to be contradicted), that a conventiional "stay-alive" in the form of a capacitor wont work on DC for the simple reason that it will feed the motor with the full 12v - and in one direction only.

 

What this means is that your slow moving shunter will stutter on the point work, then suddenly shoot off in one direction (which may not be the direction it was going in).

[34theletterbetweenB&D]

1 hour ago, OldTom said:

...The main issue with current drives and controllers (including DCC ?) is the resulting motion is not smooth enough (ie is unrealistic) at very slow (ie at realistic) speeds.  It seems to me that improved bearings and increased real inertia through flywheels, of course with improved pickup, could be the answer.

 

I remember (1959\1960?} speaking to the late great Syd Stubbs at the Manchester model railway show where his locos crawled along so impressively smoothly hauling trains at very slow speeds. He used a high voltage (I think it was 24v) because he reckoned it cut through the oxidation and dirt on the track better than the then standard 12v.

 

Measuring the smoothness of motion is an interesting challenge!

Not including well implemented DCC. Any halfway decent mechanism combined with a sufficiently good decoder (Lenz, Zimo, CTE, top my list, applied as required) will run very smoothly indeed in HO and up, realistically replicating the high inertia of rail vehicles. (I have no relevant experience in smaller scales, others will need to comment about what can be achieved there.) I run my Lenz system so that the decoders have 15V available at the motor terminals, the on  track voltage will be significantly higher and pick up difficulties there are none.

 

I would not bother with attempting to measure smoothness of motion, what matters is perception. Your brain can pick it up, there's an easily perceived quality of a gliding motion when the running is sufficiently smooth. If you listen - if necessary via stethoscope or rod on the baseboard - to the difference between a 'gliding motion' loco and one that while reasonably smooth doesn't quite glide along, you will hear a smooth whirr or hum of constant tone on the first (stable pitch), and 'wow' or 'flutter' (slight pitch variation) on the second. (This audible trait was a big thing in mechanical high fidelity sound reproduction systems, and there was good evidence of large variation in perception between listeners. If you think we get a little rude over detail issues in model railway, try the hi-fi press of the 1970s to 1990s. Equivalence, 'Rivet Counter' = 'Golden Ear'.)

[Il Grifone]

The difference is 'rivet counter' is based on reality, whereas the 'golden ear ' is entirely subjective. (There was a test in the early 90s in one of the magazines in the States where a group of 'golden ears' selected a $200 Pioneer amplifier as 'best'!). Many years earlier one of the British pedants ne month was castigating digital sound and a month on two later saying how good the FM sound was. The problem was that the link to the Wrotham transmitter was already digital....

[34theletterbetweenB&D]

On ‎05‎/‎09‎/‎2019 at 14:01, Il Grifone said:

... Many years earlier one of the British pedants one month was castigating digital sound and a month on two later saying how good the FM sound was. The problem was that the link to the Wrotham transmitter was already digital....

Oh yes, I remember it well... How we laughed, especially at those apparently honestly of the belief that once the network distribution digital signal was restored to analogue for public broadcast that 'erased' the demon of digitisation. (I am waiting for cable sexing in DCC sound...,)

 

 

[kevinlms]

On 07/09/2019 at 06:15, 34theletterbetweenB&D said:

Oh yes, I remember it well... How we laughed, especially at those apparently honestly of the belief that once the network distribution digital signal was restored to analogue for public broadcast that 'erased' the demon of digitisation. (I am waiting for cable sexing in DCC sound...,)

 

 

I once came across one brand/model of fax machine, that specifically claimed that only the supplied line cable would work. Sadly it was about 600mm (2 ft, if you insist) too short, for the customers needs. His previous fax machine had a nice long cord, but no deal.

So I had to mess about, making an extension/adaptor cord, for it to work. I don't know what was special about this cable (it looked identical), but the fax most certainly wouldn't work, unless last in the circuit. Nothing but a PITA!