In the late 1950' and early 1960's, a regular so-called treat for me on a Saturday morning was to be taken around the large department stores in Glasgow such as Lewis's and Wylie Hills. No, like most kids I did not like shopping but I had to make the best of it. However, once in these shops I would always head for the toy department where I knew I would be rewarded by being able to admire the manufacturer's demonstration train sets on show. There were usually displays by all three major brands current at the time, Hornby Dublo, Trix Twin and of course, Tri-ang Railways.
Besides the array of trains to be seen in operation there was an item that always fascinated me and that was the operating mineral unloader and conveyor set on the Trix Twin layout. As this item was electro mechanical and relied on electric power for operation, it was therefore expensive and out of the financial reach of many of us. No doubt today it is still expensive on the pre owned market.
As always, the wizards at Margate were a saviour to me. They came up with an alternative and affordable accessory to provide a means of moving model coal about. This was the gravity unloading system. This accessory requires no electric power supply and in fact has no moving parts whatsoever. Gravity and the motion of the wagon make it all happen.
The 'Gravity Unloading Set' consists of a special bridge section of track with a grey moulded base to match up with the standard track system in use at that time. The secret of the operation of unloading is the two differing plastic cams strategically placed and shaped to operate the two levers on the hopper wagons. By the way, there are two small square holes in the deck adjacent to the right operating cam, anyone know what they are intended for?
The bridge stands on two special piers which are open to allow the insertion of another parallel track down at ground level. This permits the transfer of loads from the upper wagon to a bunker or another wagon waiting below. One wagon is supplied with the set, usually a four wheel ore wagon or a bogie hopper wagon. Also supplied are two standard high level piers and a plastic bunker for use instead of the lower wagon. A bag of plastic coal was included as well as an ingenious and useful little implement which doubles up as a shovel and a brush. This item is very handy to tidy up after any spillage if you are not too accurate in positioning the lower wagon or bunker.
Tri-ang made a number of hopper vehicles that were equipped to work with the gravity unloading bridge and the most popular seem to be the ore wagon and the bogie hopper wagon. Correct directional placement and motion of the wagon relative to the bridge is essential for operation. Assuming movement for operation from right to left, the wagon must be positioned so that the two operating levers on the wagon protrude towards the viewer. The bottom of the wagon has a metal trap door hinged from the left and a lever protruding from the flap hinge. The flap is held closed in place by a centrally sprung double pivoting horizontal catch attached to another lever protruding on the same side of the vehicle
Of course the real fun in this accessory is the operation and like all brilliant ideas, is simplicity and genius of design combined into one. To unload a wagon it is essential that you master the art of driving the train very slowly over the unloading bridge. Driving with exuberance results in derailment, spillage of the load and ample practice with the little shovel as supplied. You have been warned.
Now comes the really clever bit, closing the trap door. Continuing forward, the left cam now operates once again the right release lever clear of the discharge aperture. Subsequently, another part of the cam then lifts the trap door lever lifting the trap door slightly above the horizontal level of the wagon bottom and the normal position of the locking catch. Continuing on, the next operation is the release of the trap door locking catch to its central position. The last action is that the slightly elevated trap door is released to rest horizontally on the retaining catch and the empty wagon continues its travels with the trap door secured closed. It's actually dead straightforward and fascinating when seen in operation.
An additional feature of the unloading bridge is that if the wagon is moved through in the reverse direction or is positioned the other way around, no action takes place and the load remains securely in the wagon. This is why the release lever is designed to pivot in the opposite direction towards the trap door.
This accessory must be very popular as it continued in the Tri-ang Railways catalogue for many years, even lasting, off and on, well into the Tri-ang Hornby and even the Hornby Hobbies era between 1977 and 1982.
The gravity unloading set gets full marks for robustness, ease of assembly and use and most importantly of all, excellent play value.