Couplings
Historical
Ever since operating on Cottesmore West more than 40 years ago, I've been a fan of Kadees and I decided quite early that BQ was going to have them too. Indeed, early ex-skip wagons had O gauge Kadees specifically purchased and fitted straight away. However, when I fitted the under-track Kadee magnet to some test track and had a play, I wasn't happy. I don't know why, but they didn't quite suit my stock. It didn't help when the steel wheels & axles bound on the magnet - a doubt set in.
|
I was sure it could be solved, but thoughts returned to ExpoNG 2010 (a few weeks earlier), when I was taken by the simplicity of the Greenwich coupling. I decided that a smaller central magnet would solve the problem (it has an up-down action rather than the side-to-side Kadee), but it didn't have a delay feature. Could I do my own version?
|
After a lot of Googling I came across the Dingham Autocoupler. I quickly decided that an inverted Dingham type coupling set under a small Binnie buffer (which I used extensively on the garden railway), might just work. After some doodling, a sketch design emerged (below) - a hook with a keeper (stops the loop engaging when 'in delay') and a loop with a dangly bit pulled down towards the magnet. I'm sure you can figure out how it works.
|
The prototype worked well, but could it be 'mass-produced'? On the much later Belfield Engineering layout, an 0n3 Kadee was used on the 16.5mm gauge stock that also worked well, once the difference in magnet width/positioning had been resolved.
|
Revival
Kadees must be fitted at the correct height to be moved by the magnets underneath, so if fitted, all stock must be able to accommodate them physically and visually, and work properly. As I tried out different items of stock, I remembered that couplers were one of the issues that led to the abandoning of the layout last time. The stock I assembled previously (and again now) had considerably different buffer heights. The two loco's and the 5-plank wagons were similar, but the skip chassis wagons were much lower. Some serious thought and experimentation to establish some rules were needed to take the project forward.
|
Since the start-up days, neodymium magnets have become very popular and I've used a lot in many different ways. The Kadees had only been fitted to the skip chassis, but a quick test showed that a pair of magnets placed ON the sleepers worked well, so should O scale Kadees be progressed? Having a pair (rather than the single Kadee magnet) meant that they could be set apart at different widths to adjust the amount of throw. With a separation of 9mm, two fitted to a 2mm plastic base with a 2mm plastic spacer. The unit was tried at different heights and down on the baseboard still moved the coupling dropper without tipping the wagons. It was coming together.
|
A jig was made to fit the track and show the 'top of coupling box' height for O gauge (rather than 0n3) which the flat wagons were configured for. Placed against Vinny's shed, the coupling could be fitted immediately under the buffer beam. On the Simplex, the Kadee would be have to be fitted in a new hole in the centre of the buffer beam. Both were feasible.
|
Once the O gauge coupling had been fitted to the chassis, a second jig allowed the iron dropper to be adjusted correctly, to 1/16" above top of rail. 2 neodymium magnets were glued onto a 25mm square of 2mm plastic, with a 10mm packer in between. Initially, the units are stuck to the cork underlay with double-sided carpet tape - firmly, but removable. They can be lifted and packers inserted to have a greater effect on the couplings.
|