Model Railway Forum

You're not the first one to do that! I have a Tee shirt too!!! Problem was it was a SMD IC and unsoldering it caused the PCB tracks to lift and made the PCB useless (Kit 436)!!
Glad to read you have it working.

Video evidence!!!!!!!

7B8AA9B9-2D8A-41C5-819A-3C29AFB9810C by Steve Mumford, on Flickr

Just a rough and ready test rig as a proof of concept before I think about diving under the baseboards again. As you can see, I rigged the linkage to the balance weight although I suspect this introduces a little too much play in the system. I’ll likely replace the final pull with a single length of stainless steel wire running from the signal arm straight through to the servo crank.

I still think this area of modelling is more akin to witchcraft but at least I can now claim to the sorcerer’s apprentice.

Time to order and make a whole batch of driver boards and the signals for the other side of the layout.

Would you do away with the balance weight.

Walkingthedog wrote: ↑Sun Jun 19, 2022 4:28 pm Would you do away with the balance weight.

Possibly. I’ll probably just leave it as a cosmetic piece.

I think it looks fine as it is. Would be a shame to go to the trouble of operating the signals with the weights not moving.
Just my view.

Looks great, except its a lower quadrant signal!! Ha ha

Well done and keep the balance weight it looks good moving with the arm.

Brian wrote: ↑Sun Jun 19, 2022 5:16 pm Looks great, except its a lower quadrant signal!! Ha ha

Watch it Brian or I’ll have you banned.

I’m now in the not unusual position of waiting for deliveries before I can move this part of the project forward - I have a lot of little bits and pieces from all corners of the world.
I have used the time to home in on my final design albeit only on the test rig.

The signal post itself has a length of brass tube glued into a hole drilled in the base which in turn plugs into a slightly larger brass tube that passes through the baseboard. These are marked and cut flush with the underside of the baseboard. A second hole is drilled to allow the control rod set to pass through the board - I learnt the hard way that this hole has to be diagonally offset from the post hole.

I also took yesterday’s comments to heart and replaced the two control rods with a single wire (more on order) with a kink in it where it passes through the counterweight so that it moves with the signal arm but this setup provides a much more positive throw.

20220621_111404 by Steve Mumford, on Flickr

Under the board I have secured the signal post in place with a small machine screw and spacer (more on order) as I found that any resistance in the linkage resulted in the post lifting out of the hole. I a
So added a plate of thin plywood with a large hole in the centre to give clearance for the mounting screw. The plate also allows for the servo mount to be fixed on the workbench which is much easier than trying to do it under the board.

20220621_111457 by Steve Mumford, on Flickr

Once all in place, a bend is put in the control rod where it attached to the servo arm. I found it easier to put the arm on the wire then push the arm on to the splined output of the server. This also allows me to do a coarse adjustment of the signal arm position.

20220621_111804 by Steve Mumford, on Flickr

The start and finish positions for the signal arms will be adjusted once the whole thing is in place but this short video gives an idea of the improved action. Click the thumbnail to play.

20220621_111930 by Steve Mumford, on Flickr

Looking good!
Wondering.... Would the signal arm operating rod be better if it went to the rear of the arm rather than the front as now? Seems to "twist" around the post! It may not fit that way of course, just a suggestion.

It’s a good observation Brian and I did build them that way to begin with. I found then that running the wire to the back of the arm made clearances a bit tight, particularly when it comes to drilling the hole through the baseboard. I think any twisting is the the natural flex of the 0.5mm rod.

I will now play my ‘at normal viewing distances’ card.

I fell foul of the max order volume at MERG so I had to spread the orders over a couple of days - then found out that I had cleared their entire stock of one of the components.
Could be a long hot summer in the shed.

And there’s is always the option to revisit signalling on Low Ghyll. I’m going to need that straightjacket t’other Brian offered to lend me.