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Gremlinology


Ravenser

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In February I had the layout up after a couple of months and all was not well. Things stuck and stalled because they needed a thorough cleaning, the 128's body sat visibly too high, the NBL 21 needed a wheel adjustment, I was reminded that the NRX van needs one Kadee re-setting...

 

And most importantly, the point that leads into the fuelling point (and which forms part of one end of the run-round loop) stopped throwing . I tried adjusting the motor to release it with my fingers, tried adjusting the throw wire. And all I achieved was a motor that ground and whined without moving anything. 

 

There had already been a problem here - about 18 months ago locos with limited pickup started stalling on the frog when the road was set for the fuelling point. Checking wires, remaking screw connections didn't fix it.

 

In short - a new point motor required.  Because of the very constricted space under the boards in the throat area I had used a Hoffmann motor  on this point . And on searching the forum I found an old post from Dagworth reporting that he'd had problems with Hoffman /Conrad motors when the switch failed. Clearly that had also happened to me.

 

The Hoffmann motor was originally sourced from Finney & Smith, who have been gone for years. A cheap grey clone was available from Conrad, and one or two people swore by them; but on checking the Conrad website these motors are no lonnger available. A like-for-like replacement was therefore not possible.

 

The original installation is described in an old post here but here is an old photo of the relevant area:

 

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It is the upper board that concerns us,  and the Hoffmann motor is the little black and red thing in the bottom left corner of the board.

 

Here we are again - and the tightness of the location is obvious . You can also see in this shot that the point itself is located to one side , under the board framing , a piece of which has been chiselled away to allow the throw arm to operate. Dear reader - do not create this kind of situation, except from dire and compelling need. 

 

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Clearly a Tortoise was never going in here, and the best and smallest thing I could find was a Cobalt Blue . One has already been used satisfactorily for a good few years - the blue motor just below the Hoffmann.  So a Cobalt Classic Omega motor was ordered from DCC Concepts as the cheapest option. This now comes with 3 switches: one low-powered LED connection and two high power switches. The Hoffmann motor had only one switch, which is why the Erkon ground signal controlling movement off the fuelling point was never installed. Now, potentially, it can finally go in.  (I should say here that the colour-light signals on the main board have been a minor disappointment. Because the platform roads are not in line  with the board edge, the signals are slightly turned - so it's difficult for an operator to see the aspects without deliberately moving to look. As a result they don't really serve as an indication to the operator of what route is set)

 

There  is, of course, a catch. Cobalts and Tortoises are designed to work a point immediately above them. The throw wire is driven from a mounting in the centre of the casing, through a fulcrum hole positioned on the side of the casing. Making them work a point which is off-set to one side of the motor is  not exactly obvious. And quite clearly there is no way a Cobalt (or for that matter a Tortoise) can be positioned directly above that hole right up against the baseboard frame. Which is the whole reason [sorry, pun not intended] why I orginially used a Hoffmann motor in this location.

 

Fortunately there is a commercial solution, at least for the Tortoise. Exactoscale have for many years sold a moulded plastic mounting plate to which a Tortoise can be screwed, and which is then fixed to the baseboard by further screws. The throw arm then moves a thick plastic bar which slides from side to side beneath the mounting plate - and a secondary pin projecting up from this then throws the point. The arrangement should be pretty clear from the photos below.

 

I bouight a number of these adaptor plates when Blacklade was originally built, but only used one of them. Now a Tortoise won't go in this location - but the adaptors aren't designed for Cobalt motors. 

 

But they can be adapted to take a Cobalt motor - so this posting may be of wider interest to anyone who needs to use Cobalt motors in an awkward location. Details should be fairly obvious from the two photos below.

 

The recess in the Exactoscale mouldings is just too small to receive the lower flanged base of the Cobalt. But it will take the sticky pad supplied with the Cobalt. All that then needs to be done is to mark locations for new holes for the fixing screws inside the recess. Using the Cobalt as a template to mark the locations I drilled a pilot hole with a pin vice then opened it out with something much larger.

 

Several of the fixing projections have been removed from the Exactoscale moulding to get it to fit, and I also had to saw a sliver off the back of the moulding. The loss of these fixing points doesn't matter, as the fixing screws supplied with the Cobalt are long enough to go through into the baseboard , so the original fixing points are a little bit of a belt-and-braces exercise.

 

The sticky pad is then inserted in the recess in the Exactoscale moulding, and the Cobalt added on top - this holds it well enough for setting up. The throw wire needs shortening and fits into a hole drilled in the Exactoscale bar (I left the wire too long, drilled too deep and found I'd effectively pegged the bar to the underside of the baseboard when I tried operating the motor. Once the wire had been shortened a little more all was well)  

 

The photos were taken before the  main fixing screws had been inserted into the new holes, and before the wires had been connected up, but the details of  installation should be pretty clear.

 

The current design of Cobalt has 3 switches , compared with 2 on the original design (see the other blue lump in the picture). One of the high-current switches is used to switch the live frog. That leaves at least one switch available to control the Erkon ground signal that was originally going to be installed to control egress from the fuelling point. As there wasn't a contact available on the Hoffmann this never happened, but now it might. However now I am back at work time is limited and the list of  outstanding modelling jobs is long so don't hold your breath... (I am not quite clear how the low current LED switch works. Does it switch either DC feed to a wire , meaning that an LED will light up /not light depending on which way it is connected to the wire??)

 

The replacement point motor has been thoroughly tested through a full running session - it works reliably, and the frog is live and properly switched. Since it is part of a crossover it is connected to the same output terminals on the accessory decoder as the other point motor with which it works in conjuction. This ensures the crossover always throws together , and saves the cost of an extra decoder output. Since stall motors are low current devices the total current drawn from the output is perfectly acceptable

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Edited by Ravenser

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