Freewheeling coach

[trevora]

Sorry if this is long winded but two questions in one

I am thinking of motorising a gwr slip coach

I would like it to run pulled by the train

Until it nears the station then power from its motor to run (coasting)

Into the platform

If I use geared motor/power train it  will not freewheel

So could I belt drive straight from motor to axel

And would the motor then feed power back into the decoder

Like back EMF but all the time its part of the train

 

Trevora

[Nigelcliffe]

Consisting may be part of the answer - run the train as a consist (loco plus slip-coach), so they drive together.  When you detach the coach (mechanism not defined, though I could think of some), they continue to run together.  Then, un-consist them, and slow the coach down, whilst the loco carries on.  

 

- Nigel

[trevora]

Not tried but can you / how to break consist on the fly

that would work

just did not know what damage the motor acting as dynamo would do

[pauliebanger]

Yes, I'm sure Nigel's onto the simplest way to achieve this.

 

I don't do much consisting but I know that ZIMO decoders can have an F key dedicated to switching between using the consist address and the decoder address which you might  find useful.

 

if I understand this correctly, you should be able to run your train with the specified slip-coach in consist at steady speed (possibly not coupled), press the dedcated key described to change the slip-coach address from the consist to the on-board decoder address. Use this new address to slow the slip-coach. ZIMO decoders have a manual brake feature which you can use to stop the coach precisely where you wish.

 

Meanwhile, if you have a ZIMO decoder in the loco, you can tempoarily engage the Speed Lock feature which removes speed control from the throttle. This will help to stabilise things whilst you concentrate on changing addresses and slowing the coach.

 

Best regards,

 

Paul

 

 

 

 

 

[markw]

There may be some ideas here;

https://model-railroad-hobbyist.com/node/37896

[Nigelcliffe]

The Caboose idea Mark Waters references is a good one.   

Add a big stay-alive inside it, to overcome the pickup issues, and its mostly there as a design.  And the Digitrax decoder selected is an old one, so cheap, basic, and lacking overload protection.    The article looks like a good "proof of concept" to get the idea going.  

 

Answering the "consisting on the fly" question from earlier.  Yes, can be done.  Depends a bit on handset, decoder, etc..  Some control setups make it a lot simpler to do than others.  

 

 

- Nigel

 

 

[AndyID]

A couple of other ideas:

 

Control the slip-coach as an independent, uncoupled "locomotive" via radio-control. You can have it gently push the rear of the train until it's time to detach. Power for the slip coach could be from batteries or from the track.

 

Or, put a flywheel in the slip-coach and make it all mechanical although you would have to have a method of uncoupling it at just the right time.

 

Or, add some weight to the slip-coach and use super-low friction bearings on the axles. You'll still have to devise some method of detaching it from the train at the right spot.

[KingEdwardII]

I really like the "powered Caboose" concept linked above. It allows the slip coach to be treated as a regular coach most of the time and then switched to powered mode for the slip operation. Very neat.

 

Regarding the mechanism for detaching the slip coach - if you're going to have a loco decoder installed in the slip coach, then you could use the Precimodels approach to uncoupling, linking the uncoupling unit to a function on the decoder:

 

https://www.precimodels.com/en/

 

Yours,  Mike.

[Guy Rixon]

It's certainly possible to have the coach run in under its own momentum. Plenty of weight and pinpoint bearings  will do it. There was a model slip-coach done like this on an exhibition layout decades ago (Yeovil?). That model just free-wheeled to a natural stop from the inherent friction in its bearings; it had no motor or brake. IIRC, the operators had to practice to get the right speed and release point to stop the coach in the platform.

 

It may be possible to give the coach a DCC-operated brake instead of a motor. This would make for more realistic operation and might be simpler than a motor bogie. It seems to me simpler to operate than the consisting and deconsisting.

 

It may also be possible to build the decoupling and braking into the track, not the coach. A ramp to release the special coupling on the slip coach might work, and the brake might be made like a retarder in a hump-shunting yard.

[Mike Buckner]

I wonder if you could have a short series of small weak magnets embedded in or under the track at intervals leading up to, and in, the station,  with one or two magnets under the coach, placed so as to attract each other. The slip could then take place at a speed definitely high enough to reach the  platform, with the magnets acting as a brake. Would take a fair bit of setting up.

[Mike Buckner]

The onboard coach magnets could also be used to trip a reed relay to switch a turnout, if the through train took a centre road, and the slip coach a platform road.

[Tim V]

I've done this, but on wagons rather than coaches. The plan was to do some proper loose (or fly) shunting.

 

In your case, quite easy to set up the loco and coach as a consist for normal running, but for what you plan, just have two drivers, one for the train, one for the coach. As the train approaches the slip point, uncouple using the onboard uncoupler, briefly slow the train as you slow the coach, then accelerate away leaving the coach to coast in. You could set the deceleration on the coach for very long, don't forget that the coach cannot accelerate - unless there's a downhill stretch.

[RAF96]

The idea of a slip coach was covered and demonstrated in the Hornby forum live steam section. Until we get the forum back I can’t give you a direct link to the topic.

 

Two ideas were mooted, one was to simply slip the coupling and rely upon friction to slow the coach, with experience dictating the slip point. The second was to have an active brake, whereby first selection tripped the coupling and second selection applied a brake. Inherent friction showed that unless a slip coach was running at main line speeds on a large layout, then there was little time to carry out both actions as the coach had virtually stopped itself before the brake could be applied.

 

Various activation methods were investigated for both decoupling and braking, from micro servos, micro solenoids, memory wire, motor braking by BEMF, etc.