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Simple annalog single directional stay alive


Londontram
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Can you get a small single one directional stay alive unit for 12V DC just to stop stallingn on point frogs or just any bad pick up spots, something that gives a couple of seconds?

 

 Thanks for any help and advice

   Steve

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Quick answer: no, not really.

 

Longer answer: it sounds like there have been a number of attempts to make something that tries to achieve this aim; there was a recent thread involving supercapacitors which had some pretty good results, and as a bonus included a couple of links to other threads which might be useful or at least interesting.

 

 

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13 hours ago, Londontram said:

Can you get a small single one directional stay alive unit for 12V DC just to stop stallingn on point frogs or just any bad pick up spots, something that gives a couple of seconds?

 

 Thanks for any help and advice

   Steve

Best solution is live frog points and as many pick ups as possible.

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You said uni-directional so that is fairly simple i.a.w normal stay alive practice. It is when you reverse direction, hence track polarity the problems arise, meaning a more complex solution is needed.

As stated the forum has discussed this previously.

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I should have said it's for a proposed Trolly bus layout, the busses would be steered by the Faller road system but instead of using the Faller motors and rechargeable batterys I'd like to power it off the overhead in prototypical fashion that way you don't get the Faller 0 to 60 one second starts and the same with the stops along with the fixed top speed. Building the over head is no problem as I'm a Tram modeller of old but with just the single trolley pole pick up for both wires it would stall on the slightest gap in the over head wire which would be the frogs on points. With a loco there's usually at least two or more sets of wheels providing pick up points so they can "bridge" the gap but the trolley boom hasn't got that option.

 

As there buses they will only be running forward and no situation built into the layout that will require any reversing.

The buses will be the Corge London Q type Trolly bus as seen in these photos fitted with one of the motors shown with bevel gears as seen here with hand built Trolly booms with the components also seen here. I've ordered a spare Faller front axle but for future vehicles will most likely clone it. As you can see from the photos there's absolutely loads of room for and electronic gubbins

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Edited by Londontram
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Thank you Russ I'd thought that about DCC and there's an on going thread on there about it with the same question. Well you could fit a fly wheel but not with that motor gearbox option as there's no secondary shaft but there's enough room for a bigger motor if needs be.

 It's only got to bridge a 2mm gap 3mm at most not keep running for 4 or 5 inches.

 The drawing below shows the problem points that would need bridging

20210923_060229.jpg

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A cheap, simple, and crude method is a resistor (for charging) and big capacitor, probably plus a diode to protect against power accidentally applied the wrong way (which with many capacitors results in death to the capacitor, and sometimes a small explosion).  

 

The resistor charges the capacitor, if power is lost, the capacitor discharges through the motor, keeping it turning.  

 

Downsides:   

  • acceleration of bus is limited by the capacitor charging, even if power is turned on full, bus will only accelerate as capacitor charges through resistor. 
  • deceleration of bus is controlled by the capacitor.  It will slow as the capacitor discharges, even with power turned to zero.  
  • during deceleration, there is nothing to prevent the bus stopping when there is no pickup from the overhead supply.  
  • amount of stay-alive is a function of voltage, at low speeds there is very little.  

 

 

 

A totally different option would be to use on board batteries, and a Radio Controlled speed controller (eg. Micron , for Radio Controlled trains).   Thus, there is full speed control, but no issue with pickup.  Steering stays as the Faller magnet-following system.   It might be possible to arrange that the over-head could re-charge the battery, but that's a bit more complicated to arrange.    There is no issue on space - I've put full Radio Control (motor and steering) inside an N-gauge bus, so the size of those has plenty of space for batteries, radio receiver, etc..    Radio receivers would work easier with the 5volt versions of the N10 motor-gearboxes.  (The motors on the N10's are usually held on with a couple of screws, so one can swap 5volt for 12volt easily).   

 

 

 

 

8 minutes ago, russ p said:

Can you make space for a flywheel? 

 

Flywheels are difficult with the illustrated N10 motor gearboxes.   To be effective, the flywheel needs to be before the spur gears, attached directly to the motor shaft, not after the spur gears.  

 

 

- Nigel

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7 hours ago, russ p said:

Can you make space for a flywheel? 

There is room for a nose suspended motor with enough room for fly wheel up to 15mm by changing to a different motor like the Mitsumi as seen in the picture here laid roughly where it would go in relation to the body. 

20210923_181116.jpg.58c1a404df464cef7b49cc2ce8a8947b.jpg

Suspending the motor means I would also be able to drive both axles but there's no gear box. Having no experiance with fly wheels how far would a fly wheel be expected to move a vehicle of this size and weight - I'm looking at 3 or 4 mm max, would that be a feasible amount to expect.

  The other thought would be to have the frog totally live and isolated with a switch to change the polarity.

 Would welcome your views and any ideas please chaps 

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I think you may get a small jolt but I would think it should get through the gap.

The radio control would be good but DCC would allow you to have buses close together 

Great project,  I love trolleybuses and remember the teesside ones

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I think you need to stop worrying.   The reason we need stay alives is because we use low geared worm drives which are not reversible. The loco can't be pushed along the track. The gears would strip first. As power is lost the motor slows and the loco trying to drive the motor just loads up resistance and slows the motor more.  The old Lima spur gear drive locos sailed on for several inches when power was turned off from full speed as did the large wheeled Hornby tender drives and also for a few millimeters at a crawl.  Hornby Dublo pre WW2 mechs used very coarse worm drives which are reversible and likewise didn't stop dead on dead spots.    The Trolley bus has bevel gear drive which is reversible so it will most likely sail on regardless of the interruption.    You could use a flywheel like the Dyna Drive, but stopping might need a lot of reverse power.  In fact with any DC stay alive getting enough capacity to crawl a few millimeters  while still being able to do an emergency stop  in a reasonable distance from full speed is very difficult.   Batteries and Radio or Infra Red control might well be a better idea if you really want to make life complicated

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