DREWRY 0-6-0 Diesel Mechanical tram project
This project was inspired by KLDSME member Trevor Cox using his own design and build Drewry Shunter, BR 04 class loco at our Lynnsport track. This 7¼ gauge loco provided effortless services hauling up to 3 trolleys on public operating services over the past couple of years. Built to a scale of 2.187, it is a little over scale but looks right at 4 foot long. Mike fancied building one of these, but as one of the Wisbech and Upwell tramway engines that he used to see as a child.
A trip to Embsay was schemed up, the loco here being D2203, an original Tramway engine. Up at the crack of dawn for the 150 mile journey to Bolton Abbey, suitably armed with tape measure and notebooks. A short cab-ride was allowed whilst the loco was positioned in a more suitable spot for our purposes.
A basic plan was drawn to 1.54 scale (7¼) but this had several drawbacks, it would not accommodate two leisure batteries and the space to fit the motor / driver unit was not adequate. A new scale size was needed, one that would give the required installation space and most importantly be easier to handle, although still too heavy to lift.
After a couple of sketches, it became clear that the nearest scale that would meet the requirements that allowed enough space would be to adopt a scale of 1.7 inches to the foot. (gives a loco length of about 40 inches). A determining factor is the size or footprint of the batteries, followed by the positioning of the motor drive unit.
It was proposed to design two versions of this loco, however, a simple tram version, with side plates and cow catcher was chosen as the initial loco. This would have 3 axles without the jack-shaft at the rear. The 3 axles be connected using a 17 tooth (duplex) gear wheel system. It would not have connecting rods since they won’t be seen anyway! The rear axle and middle axle will have duplex gears linked with ⅜ inch chain whilst the front one only required a single cogwheel. This design did away with the need for a auxiliary jack shaft.
A “Shunter” version of this loco would need both the connecting rods and the additional jack-shaft. The need to join or connect the other axles by cogs and chain drive not being necessary. The Controller, Batteries, Bearings and Bosch Motor are exactly the same for both versions. This loco requires 3 main axles, 6 TU204 bearings plus 2 FL204 bearings.
Tram Parts required for engine frames are:
- 2 no. Mild steel side frames
- 2 no. Mild steel end plates (buffer beams)
- 2 sets Mild steel angles for front and rear fixing brackets
- 2 no. Mild steel stretcher bars
- 8 no. 20mm bearing units
- Screws and nuts
- 24 no. Bearing retainer slips, 15mm x 3mm mild steel bar x 70mm long
- ms plate for the cab, ms plate for the bonnet and miscellaneous bits.
- 1 no Bosch 1 hp 24v motor. The 4QD controller items.
- 2 no 12v horns
- 2 no 85 A/hr leisure batteries.
- 1 no 12v. 7.5 A/hr sla battery for the horns.
The buffer beams are deeper than the longitudinal main frames.
The dimensions were made to suit the actual chain drive system to be used. This made the wheel centres distance, critical so where it stated 195mm, this had to be correctly made. If other alternatives are used then the dimensions given might not be accurate enough for fitting the chain drives.
What powers the engine? A single Bosch, 24 volt, 750 watt motor that delivers one horse-power. With the right gearing this should be able to reach a maximum speed of 6 or 7 mph, and be able to pull 3 or 4 carriages on a level track. Two 12 volt, semi-traction, deep cycle batteries are connected in series to provide the 24 volts that powers this engine and makes it perform, as designed. The 4QD VTX 75/24 controller ensures that the driver has the means to start, pull away and when required stop the beast. This controller also has the means to regenerate the batteries and provide braking if used correctly. This also needed a 4QD relay unit so that the horns (and lights) could be operated from the one hand controller.