Fiddle yard adventures - Part 2
Entry posted by JRamsden in Addleford Green Blog
538 views
I recently lost my enthusiasm with Addleford Green. I realised that I just wasn't all that interested in running trains on it. After some thought I realised this was due to the fiddle yard. The thought of using my clunky cassette design filled me with dread and would ultimately break the careful illusion that I was running a railway. What I really wanted was a traverser. But I just didn't have space.... did I?
Long story short, I made space!
Another issue had always been the point at which track left the main board - it's about an inch from the back edge. For a traverser it needed to be central, otherwise the traverser itself would be crazy wide to give enough range of movement for all tracks to align with the leading line. I worked out the smallest possible space (using no tighter than 2nd radius curves) needed to curve the track to a central position and decided an additional board of some 20 inches would do the trick. With all this in mind and available space measured, I decided to bite the bullet and create a full traverser board.
I umm'd and ah'd over various designs. I liked the idea of using drawer runners for the sliding action as the ball bearings would make this nice and smooth. Initially I thought I would lay the runners flat on the bed of the board but ultimately opted for a side-mounted design instead, feeling this would be stronger. I came across an image of a traverser fiddle yard from May 2018's edition of Model Rail magazine. This looked just the business.
I started with a single sheet of 9mm ply as the base, 18 inch wide by 35 inch long. Onto this were screwed two 36m x 22mm batons leaving a 9mm gap for a plywood fascia. Sorry for the mix of metric and imperial, I was raised on both! 
After this came some hefty chunks of wood. 36mm x 89mm, perhaps a bit on the large side but I'd been reading that you can't over-engineer these kinds of things.
I cut a large hole in one using a jigsaw. This was to allow for electrics. Better done now than regretted later on! Perhaps a bit too large, but, hey!
Then some more 9mm ply for front and rear fascias. The front would be removed and shaped later to allow for the sliding tray to be pulled out from the front.
I selected drawer runners that were half the width of the board when closed. That meant that the tray would be at the full mercy of the ball bearings when fully extended. The other option was to use drawer runners which ran the entire width of the board, thus the moving arm would be supported at all times. However this would also lead to a large amount of protruding metalwork - not desirable. To compensate, I made sure to buy heavy duty runners which would hopefully negate any potential sag.
Bracing beams were added to the bottom.
A 12mm ply top was added at the far end. I went with 12mm because this would raise the 9mm sliding tray (30 inch by 9 1/2 inch) just clear of the frame at the far end, allowing it to overlap. The batons for the side of the sliding tray were attached to the inner part of the runner and offered up to the board. The top of the sliding tray was just rested on top so I could test for height and adjust accordingly before committing to a final fixing.
Aligning the runners was not easy. The main, fixed part had to be attached perfectly straight. The moving arm also needed to be fixed to the tray perfectly straight. Then the vertical height needed to be considered so the tray top was level with the board top. Thankfully the runners have multiple fixing holes, including some that are slotted to allow for adjustment before final fixing. Constant testing was required and there was one point where I got a bit overexcited and didn't check my work, leading to the tray binding when pulled too far. It's not impossible to achieve, but it does take time, thought and care. I highly doubt a carpenter would approve my work, but it seems to do what I want!
Sides were added to the top tray to provide stability and also act as a barrier for any falling stock. A central beam was added to the underside of the tray. This is what would accept the indexing system. Some cheap, plastic handles went on too.
I initially wanted to use a ball catch as the indexing method but ultimately went with neodymium magnets. These ultra strong magnets (also known as rare earth magnets) have sticking power like I've never seen and can also be used to lift incredible weights. They would provide a very firm connection and were a tidy and precise solution.
I decided to place a line of magnets underneath the tray at intervals that would represent the mid-point of each track. There were to be five tracks in total. I had to make sure both central beams on the board aligned.
Using a measured guide I printed from my computer, I was able to space the pilot holes for the magnets easily and accurately.
The magnets come in a countersunk variety, perfect for screwing into woodwork. I selected screws for their head size; it was important they didn't peek above the level of the magnet and impair their connection to the interface magnet. It was also important to make sure the interface magnet (the main one on the board itself) was an opposite polarity to these five as it would need to be attracted countersunk side to countersunk side. Luckily they come in two pole variants! This is usually the kind of thing I only realise after purchase!
I could have used a metal washer as the main interface, since we are dealing with magnets after all. But alignment was key and magnet-to-magnet alignment is near perfect, whereas a magnet will grab at any part of metal they can find.
Another template on the top of the tray helped me to get an idea of where my track centres would be. Amazingly they lined up almost perfectly first try! I will lay the actual tracks later so I can be certain of correct alignment.
The interface magnet was screwed to a spare piece of plywood which spanned several beams. This was so fixing screws could be placed well away from other magnets and not interfere with the indexing function. Several washers were used to gain the correct height. Rather pleasingly, the plywood had some flex to it, meaning it had the surprise benefit of being pulled slightly upwards in contact with the magnets, only to drop back down slightly when the magnets moved away.
The exact washers and screw used here were really just to test the theory; I need to replace these with slightly more suitable variants.
This resulted in a very definite and reliable indexing system. The tray required a bit of a pull to dislodged it from each magnet, but not enough that it would send stock flying... I hope! I haven't actually tested that theory! The handles also help to steady the transition, particularly when using both hands. It was also very good at finding a reliable centre each time, the template on top seeming to line up every time I tried it. I guess time will tell if this applies in the long run!
Next job will be making some legs, making some more space and getting the board in place so I can design the joining board. Then it's on to electrics and track laying! Watch out for more soon(?)
All for now,
Jonathan
Edited by JRamsden
-
6
-
2
4 Comments
Recommended Comments
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now