For no extra fee visitors to the Bristol 7mm show yesterday were treated to an animated discussion between Peter, myself and a bushwacker's hat masquerading as Steph Dale - in spite of Cynric's information I can confirm that Steph had neither pipe nor slippers. Said discussion concerned the fun awaiting those foolish enough to consider the new sport of "motorising a R&R 36T crane". So that those eager to play the game can experience the joys of the challenge here are some of the rules (noting that rules are changeable without notice and are not necessarily agreed by Steph, Peter or myself).
[1] required motion includes... travel, slew, derrick and lift. Crankshaft to rotate whenever any other motion is apparent (but excluding crane topple which ends the game).
[2] all motion to be DCC conrolled with interlocking to prevent conflicting motions (R&R did not design the crankshaft in such a way that all dogs can be engaged at the same time).
[3] Sound desirable although non-implementation until completion of restoration of GWR No. 2 is accepted (yet to be approved as a WT strategy for Mornington Crescent).
[4] working propping girders warrant immediate certification and a new, yet to be defined, WT-title (maybe Jordan could consider an Honorary degree of "Naughty Corner Monitor"?).
So how are we progressing? Not very well when we set off to the show although ideas were bubbling. Here are some photographs of the progress until we realised that following the instruction sequence was of minimal help in planning the installation of the motors. Current plan is to place motors for travel and for slew under the bed of the carriage with remaining motors in the cab / crab. However, space in the carriage is at a premium as can be seen from these photographs.
The first photograph shows the bed of the carriage (from underneath) together with the left hand and right hand sideframes for the rigid axles. The two small sub-assemblies are the housings for the propping girders. Attached to the carriage bed are three transoms which affix the bogie and the frame for the rigid axles. There is very little space, for a gearbox, between the crab pivot centre and the middle transom!
The second photograph shows a side frame / solebar bottom plate in place (temporarily) ... and overlapping the three transoms. Soldering the side frame into place rather locks the transoms into the carriage underframe.
The third photograph shows both side frames in place (temporarily) with a propping girder housing resting on the solebar - there is one housing at either end of the side frames. The more that is added.... the less space there seems to be.
At least Steph, Peter and I agreed on a plan of action. First step is to move the transoms for the fixed axle frame to the outer ends of the side frames, this lengthens the space between the transoms by around 3cms. If necessary the centre portion of these two transoms can be removed although that requires a change to the method of attaching the fixed axle frame to the carriage. The reason for this change is to gain extra space for a worm drive gearbox and motor to provide slew drive (via a vertical shaft upon which the crab can rotate).
As the prototype is thought to slew at a rate of between 1 and 2 rpm then the reduction from motor speed to slew rate is considerable. All useful suggestions received.
After the slew motion the travel may be somewhat easier. The fold-up etch for the bogie frame was shown to Brian Clapperton (ABC Gears) with a request for a solution - favourable reply suggests a single motor lying parallel to the axles and with gears to drive both axles. I have to provide dimensions of the bogie so that Brian can confirm his "back-of-an-envelope" sketch. Fingers crossed.
regards, Graham