Reconstruction work at Dunalistair

[tedp]

They hold back the stone setts.

Track inset in a road takes many forms, sometimes using double-headed tram rail, or using a second rail or even a piece of steel flat to keep the flangeway clear from stones going astray. In some cases a wooden fill piece made up of sleepers is used. As long as the flangeway is kept clear.

[tedp]

Today I'm running a trial service to test the new track under normal operating conditions. The points are set by hand - I have to avoid throwing the point levers on the panel!

Here are Brutus and the Darjeeling 'B' which have double-headed a down passenger train. These two run together very well by the way - the old Liliput chassis and the old Arnold seem perfectly tuned.



Up to now it works all right. Few problems have surfaced, but I have some tools standing by to correct anything going wrong.

[clayliner]

The running over the new pointwork looks gratifyingly smooth - you must be very pleased with the result ( and maybe even a touch relieved!) Your experience shows, but then it would all be wasted if it didn't!

David.

[tedp]

Thanks, David. I'm glad to see it is very smooth indeed. I had tested the pointwork after I built it, and made some tiny adjustments at the time, but you never know what happens when you fiddle the units in and out of place.

Up to now I have tested almost every type of wheel over it (especially that diamond crossing) and they all go through without bumping.

A big improvement over the rough riding of the old one.

[Stan Williams]

Like good wine and good Scotch, you get better as you get older.

Stan.

[tedp]

 ;D

Depends on the quality of the original, which wasn't too good to start with.   ::)

[tedp]

Another upheaval!

Being satisfied with the track, I took Dunalistair apart and set the station unit on its end so I could access both sides. I screwed an angle iron to the layout and the framing behind to keep it upright. Unfortunately, the cable and connector needed to power the circuits are fairly short (they can be seen stretched diagonally), so I'm forced to work in a cramped space to the left of the vertically positioned unit.



Now is also the time to show something of that turntable I built about 40 years ago, which is still working reliably after all that time. This was made using a primitive Supraphon 8" record player. The table shaft is still true with very little play. I oiled the motor bearings as it was very noisy



At the bottom is a weighted lever which presses a roller on to the edge of the steel turntable. In this I filed notches for the roller to drop into. As soon as it does, the microswitch is released and the motor stops. In addition, the table is locked mechanically - it has automatic indexing, stopping at each approach track. Pressing a button powers the solenoid and lifts the roller, switching on the motor.



The visible part of the turntable (the bridge) is fixed permanently to the table well, which turns with the bridge. Note one of the rail contacts on the side of the table, bottom right. There is another at the other end, so the polarity of the track on the bridge is automatically
reversed using contact springs in the frame.



The ancient Fischer Technik drive, which is still faithfully doing its job. The big worm is the final drive.





The purpose of removing the unit was to get at the slot for the release point at the headshunt. I made a copper strip with one pin sticking up through the slot, a pivot in the centre and another pin sticking through the hole in a standard Peco point motor adapter slide. I tested the motor using the capacitor discharge unit, and it slams across positively. I was glad about the slack I left in the lever, or the full force of the point motor would have come on the point's tie bar. The point has a throw of about 2mm, the point motor has 4mm, so you need to leave some slack.





To be continued!

[Harry Mantheakis]

My mind is starting to boggle...

[Hugh Norwood]

Seconded!
Remarkable work there, Ted.

[tedp]

Thanks, both! It is a lot of work and it involves some athletic moves on my part, but it seems to move forward, one step at a time...

Today I installed the point motors of the release crossover at the platform end. Points nrs 5/6, worked in tandem by one point lever. They have been connected up and tested, and all seems to be OK.

Here is a short video, part of which was made in bad light, but probably the points can be seen to work in unison. Note the multi-pole switch seen halfway the film - this will be connected to the tail end of the operating pin on the motor. It will be glued down on the block of wood so it's at the same level.

https://www.youtube.com/watch?v=wCyxIoifF7Y

The adapter slide for the second point motor proved to be different from the first - it's almost impossible to first fit the adapter under the baseboard, then insert and lock up the point motor. The pinholes to fit the adapter in place cannot be reached to drive a pin in, as the motor is in the way, and locking up the tabs on the motor can only be done before fitting the adapter. Chicken and egg. But I found a way to do it.

Why use adapters? I didn't cut large holes in the baseboard to fit the motors directly under the points, and since one motor was fitted with one, I decided to fit the other one as well to ensure they would work together. To reach the point's tie bar, I fitted a thin screw about 1.3mm diameter, with the end filed down. I think it must be a 12BA screw.



I had the devil of a job to get the motors to throw. They are much smaller than the huge ones I used to have, so they need more power. I had to change the operating capacitor (C1 in the diagram) from 220uF to 1000uF. Probably they will work at about 470uF but I didn't have one.

Warning: diagrams ahead!

For the electronics buffs, you will see that the switch charges the capacitor over one coil of the point motor, and discharges it over the other. So the position of the switch shows the setting of the point.



However, I don't simply connect the power to 12VDC as shown in the diagram, it is fed from a huge capacitor discharge unit and a voltage multiplier. This charges a big 3500uF (not 2000 as in the diagram) storage capacitor with 38 volts:



The charge of the storage capacitor is used to load the smaller point motor capacitors. This helps especially with the charge cycle as you throw a point motor - there is a huge charge available to do the job. To make them work with the CDU, this takes the place of the resistor (R1) and capacitor C2 in the first diagram.

[tedp]

And in addition, I just installed and connected up the polarity switch. This is an old radio chassis switch, DPDT, with the latching mechanism and spring removed. It was already present in the old layout and I just reconnected it. Note the switching action in the photos below.





A steel wire was fitted between the tail rod of the point motor and a hole drilled in the switch stem. The wire was stiffened by a piece of re-used aluminium tube (hence the filthy exterior) threaded on to it and glued on the wire. The end of the wire was bent and bent back through the hole in the switch stem, and wound round a screwdriver to make an eyelet the other end. Then it was locked in place by supergluing a bit of brass pipe to the tail rod of the point motor.  I glued down the switch on the block of wood visible in the photos, after setting it to the correct throw.

Soldering the wires to the track proved it was mercifully the right way round. Otherwise a short circuit would have ensued...


;D

[tedp]

Just a short message saying I installed the point motors at the other end of the loop, at the loco siding end. I had to make up my own point motor bases from 4mm ply, and fit extenders to the operating pins. Getting them to drive the points took a bit of fiddling, as the pins tend to catch on the slot cut in the baseboard and you need to set the throw exactly right. I still need to fit the frog backup switch, which will be done the same way as the one of the other pair, on a block of wood.

Again, there are two Peco motors doing the job of a single home made one that worked the two Fleischmann points there used to be. This is because of the operating direction of the point mechanism - I cannot fit a lever under the baseboard to work two points from one motor.

As in the other pair, I needed to increase the driving capacitance from 470uF to around 1500uF. It might work with 1000uF but I hooked up a number of very old capacitors to get enough power. These may have deteriorated - I really have to install new ones.

Apart from having to drive two point motors of less power than the old ones, the Peco points take more effort as they need to be pushed through their over-centre springs. Luckily the driving circuit allows tuning the amount of power you need easily, by replacing a capacitor.

All very dull to read I expect, without photos - tonight and tomorrow I don't have much time to take photos and upload them, so I'm afraid you will have to wait. However, I am slowly getting there. The sidings from the harbour road can be driven from the old point motors as there is space to mount them at 90 degrees to the track. However, I will first need to restore the drive pins as these are all very worn.

To be continued!

[gtmspyder]

Thank you for the update Ted, it's all very interesting to us on the sidelines.

I have been installing reed switches at the short section breaks for holding a series of trains one behind the other, to indicate where a train is parked, but I might have made the short sections too short as sometimes the loco over runs onto the adjacent live section, it depends on the speed of the loco's approach to the mini-section of course.

Keep up the good work.

Kind regards,

BrianT.

[tedp]

Here is an update with photos of the work done on the entry points to the platform and the run-round.

First, a close-up of the plywood point motor bases I have made. These have a slot for the operating pin, and mounting holes for screws into the baseboard. The Peco motor is fitted into undersize holes drilled into the ply and glued down. I had to drill several mounting holes before it was lined up to my satisfaction. The throw of the motor has to be matched to that of the point, so there is no excess to either side which might overload the point's tie bar.

The thick solenoid to the left works the platform starter. This is held to 'danger' by the weight of the thick core. Applying 12VDC lifts the core and drops the signal arm. Now it is of course inverted!



Here is a similar point motor working in parallel with the other. This operates the entry point and the switch controlling frog polarity for both points. Note the radio switch which, again, is mounted on a block of wood and worked by the tail rod of the point motor. The spaghetti wiring has to be bundled neatly. The two photos show the switch in the 'in' and 'out' positions.

Note the scarred bottom of the baseboard, bearing witness to all the reconstruction work done over the years.





Finally, a return to the diagrams published before. I realise it might have been confusing, so here is a combined diagram.



The grey area contains all that is needed to operate a point with two solenoids. For every point, this is duplicated. The capacitor in the grey area is charged over one coil of the motor, and discharged when you throw the switch. So each time you flip the switch, the point motor will follow the switch.

The capacitor discharge unit (CDU) contains a voltage multiplier - it makes 38V DC out of 14V AC, and charges the storage capacitor. I notice I didn't change the capacity in the diagram - in my case this is 4700uF. At 38 volts that packs a lot of instant power, needed to supply the smaller capacitors used to 'fire' each point motor. However, none of this will ever burn out your coils - it's only a short burst of power that won't overload the solenoid.

All you need to watch for is the mechanical jolt produced by this circuit. The point motor should take up the slamming itself instead of relying on the tiebar of the point.

I hope this clarifies the system used at Dunalistair.

[tedp]

Today I started work on the old point motors that will be re-used for the harbour sidings.

As explained before, these were made of heavy duty industrial solenoids. Despite their rough appearance and the shabby state they were in when removed from the layout, they are still healthy and probably good enough for another 40 years' service. I decided to re-furbish two of them, putting them on a new base before installing. The third one was good enough - it has a brass tube for a driving pin, stuck fast in a well aligned pair of solenoid cores. I soldered in a piece of brass rod and glued it under the baseboard.



Again, note the very dishevelled state of the plywood the baseboard was made of, due to all the work done on it over the years.



The point motor was aligned so the tie bar takes the least possible load. And possibly due to the great efficiency of these solenoids, I could leave in a driver capacitance of only 300uF. The point goes across smoothly. The only thing I need to watch is what it does when I fit a switch for the point's frog polarity.

Here is one of the point motors being reconditioned - it was removed from its base and fitted on to a new one. The driving pin is new, made up of a piece of square brass tube and brass rod, with a collar on both sides to prevent it dropping out. Note the core lips are staggered - this makes for better stability of the driving pin. One of the solenoids has to be fitted on a thick card underlay so the cores will line up. I leave a throw of 5mm, about the same as that of the Peco point motors.