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Richard A-J
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There seems to be a general policy in model railroading that inertia is not required when switching (shunting in the UK). Can anyone tell me, what on earth is that all about?

I see videos of realistic operations but when it comes to the switching … it's back to being a kid again! It is even advertised in the instructions for controllers, for instance "But while simulated inertia is good most of the time, it can be a problem for shunting operations. So we've added a front panel switch to disable inertia when you don't need it" - "While inertia is for simulating heavy trains, in the scale world of models, we normally want to stop or slow down trains much more quickly than would be possible (or safe) in the full-scale world" (these are instructions for a self build controller but all controllers with simulation mode will make similar comments).

Am I missing something? When does a model not need inertia? When in the real world can you eliminate inertia? Everything has inertia, even a bicycle, even you, not just heavy trains; a single locomotive weighing some 100 tons or more has inertia all on its owny pony. Surely, a true model should have a motorisation system that models that of the real thing? In other words its performance specifications should model the prototype's. Operators should have no choice in the matter. An engineer of the real thing cannot flick a switch and make a locomotive accelerate or stop faster than its performance specifications just because they're behind in the timetable.

I bet the real railway operators wish they had such a switch, trouble is their engineers would then have to be strapped in tight like racing car drivers and be trained like astronauts and fighter pilots in order to survive the G forces involved. If a timetable requires that inertia be switched off in order to get the switching done on time then does that not mean by definition that it cannot be a realistic timetable?

I agree that an operator should have the ability to easily adjust inertia whilst operating i.e. to simulate different weights of train, but zero inertia should not exist for a model because zero inertia does not exist in the real world. The lowest inertia setting should simulate that of a 'light' engine i.e. one with no train.

Right, I've had my rant. As you were folks :Salute:
Rich

Last edited on Thu Oct 26th, 2017 09:38 am by Richard A-J

W C Greene
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Howdy Rich, inertia in a scale model locomotive is (I suppose) a cool thing. But the facts are probably this: flywheels/inertia control are believed to overcome the age old problem of a tiny locomotive running on track which has the power supply sometimes losing contact with the wheels and the electric motor and causing the loco to stall or just stop until the layout is whacked or the "giant 0-5-0" reaches in and moves the loco along. In other words, bridging the gap between specks of dirt on wheels or track or both.
I know modelers who swear by flywheels and inertia control and they have their opinions, mine are different but then that's what makes the world go 'round.
Does any of this crap make sense? It does to me but then that's why I am known as the original Outlaw Troublemaker.

Woodie

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Hello Rich,

Your last paragraph also answers your question - variable inertia.
 
What most operators require from a model is the ability to instantly stop at the point of touching up to the wagon(s)/cars i.e. no loco inertia for precise 'spotting'. But some model 'drivers'/engineers like the idea of a train/loco gently coasting to a halt after cutting the juice.

This is totally unlike the prototype where it is very difficult JUST touching up to a wagon (a wagon whose end & buffers/knuckle you cannot even see from the footplate and a real loco that itself cannot stop instantly, no matter how slowly moving. It's terribly easy to send the wagon rolling off, especially with spring/shock absorber buffers.

This is where DCC offers the best of both with multi step motor control. For ultimate model realistic experience, leave the inertia 'On' & learn to judge your model loco's exact deceleration rate to a fixed point. Then repeat that all day long in rain, wind, heat & frost etc. etc.  

Regards,      Michael



Richard A-J
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Hi Woodie - oh I am a great believer in flywheels, and they have to be bigger than the motor. I have converted to battery powered radio control so the dirt problem does not bother me but I still believe in flywheels because their main function is in modelling inertia. Yes inertia is 'cool', that's because it models the real thing. The way I see it, to not give a model 'scaled' inertia is like not giving it wheels .... eeeek!

Michael - I think I am beginning to see the problem. Is it true that DCC controllers only allow an on / off facility for inertia whilst driving? You can't adjust it easily whilst driving? You have to go into the CVs. Therefore if you've got the inertia set for a heavy train you are, in effect, stuck with it even when your engine is light. It seems to me that this is a failing of DCC controllers. They need to add a means of adjusting inertia easily whilst driving, but I repeat, there should be no zero inertia available because zero inertia does not exist. Here's my radio transmitter which I posted in another thread:-

http://www.freerails.com/view_topic.php?id=7104&forum_id=45&page=5

As I mention in the accompanying blurb, the top right dial is the inertia dial. As bought the dial was able to be turned anticlockwise to take that white dot to the 7 'o'clock position, but that gives zero inertia. I have therefore adapted it with the screw so that the lowest inertia setting is now at 12 o'clock, which represents the inertia of a light engine. So now, at its lowest setting (12 o'clock) it can buffer up more realistically as a light engine and stop relatively quickly (remember it still has inertia - light engine inertia). When the loco is then pulling a load it is easy enough to then turn the dial clockwise to represent the now changed inertia using my own judgement dependant on weight of train.

I recommend DCC users badger your DCC suppliers for an inertia dial on your controllers so that inertia can be easily adjusted whilst operating rather than being stuck with whatever the CV is programmed to. Actually, I remember my NCE controller had a button called Option and I recall I used that as my emergency stop button because it gave a modelled emergency stop rather than a 'toy' stop. Perhaps that could be used for light engine buffering up in the meantime if your DCC controller does not have easily adjustable inertia.

Rich

Last edited on Fri Oct 27th, 2017 08:38 am by Richard A-J


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