Where to start…! I guess the chassis would be a good start.
The chassis components were already in stock, having been done by the laser cutters some time ago so it didn’t take too much time to bolt them together, using angle iron in the corners. It’s not long before easily manageable components become one rather heftier item!
The bearing units are Mike’s favourite, ever dependable, TU 204 units with the bolt mounting point machined off and a recess milled in the top to take a spring. This way you can have shorter springs and a less deep chassis. The bearing itself is removed and a 2 or 3mm hole drilled through, the idea being that you can drop oil down so the bearing remains ‘free’ to rotate within the casting.
These bearings are superb; get hold of one and you will see why they are ideal for miniature railway vehicles. Not only is the bearing sealed, it comes within its own flanged casting so you can practically ‘drop’ it into your vehicle’s frames. The bearing itself is free to oscillate within the casting in all directions, so any side-to-side undulations in the track can be accomodated, less stress on the axles.
Next step is to sort the motor mountings and chain drive. Previous Drewry’s had the motor centrally mounted with the batteries positioned fore and aft. With the two Ffesties built between No 3 and 4, Mike decided to try a rear mounted motor with batteries placed forward in the bonnet; this gives the weight of the batteries over the wheels, giving excellent traction and stick and stone crushing ability! The gear reduction ratio is 6 to 1, driving firstly to the jackshaft and then to the rear axle.
Below is a good view of how the springs and axleboxes just slot into the frames, held in place by sockethead cap screws. You could make bars to go across these to restrain them if you wished, we find the cap screws do more than adequate job. The chassis is tapped with the appropriate thread and they just screw through.
The wheels are secured to the axles by drilling and tapping them through, more sockethead capscrews hold them firmly in place.
With all the gear in place, it must be time to test it all out. Temporary fitment of a 4QD controller enabled Mike to spin it all up and check/adjust chain tensions as required. As this would be the sixth chain drive loco Mike has built, he’s getting the hang of it now and all went well from the off.
Stuff does get rather heavy once the wheels are on, so the hoist comes in handy for moving the chassis between its carrying trolley and the outdoor workbench!
Once the chassis is rolling, its time to crack on with the bodywork. The laser cutters had already produced the bonnet ‘hoops’ and the framework was welded together. The bonnet ‘skin’ is made from 1mm sheet steel which is formed with the aid of some angle and a sash cramp! Spot welds hold it all together, a tricky job welding such thin sheet…!
The nose ends are the trickiest with their compound curves. Various methods had been tried in the past and the end results were mixed; fibreglass has been tried, planed wooden blocks worked out well… this time something different. More thin steel sheet welded to the nose end framework, snipped to fingers, bent over and the gaps filled with Isopon and JB Weld, sanded and smoothed to shape.
Looks alright doesn’t it!!
Fitted to the end of the chassis, the rest of the bodywork can start to take shape…
The laser cutters were rather booked up for the few months during with Drewry 4 was under construction, so Mike had to go back to doing things the old fashioned way; cutting from steel sheet using hand tools.
Fixing the bonnet side panels to the nose end… simple brackets.
Starting to take shape. Of note is that Drewry 4 is following the outline of the regular shunter Drewry, whereas Nos 1,2 and 3 (seen here) took the form of the earlier locos that became Wisbech and Upwell tramway locos, with their square windows, cowcatchers and boxed in wheels.
Brunswick Green, anyone?
Having access to a roller is a great help when it comes to forming the cab roof.
Construction of the cab is quite straighforward, using angle irons in the corners and bolted through. Miniature G clamps come into their own here.
The last cab side panel roughed out by hand and awaiting a trip onto the mill to smooth the edges off. This takes a couple of hours in an afternoon to make up the panel, the laser cutter would have had it done in less than a minute! A lot more blood, sweat and tears have gone into the making of this loco!
All made true, bolt/rivet holes all made ready to be fitted up…
An important extra to these locos, following the success of the two Ffesties, was the double heading option. The plastic six pin ‘Bulgin’ connector as available from 4QD is to be used for this function. The hole next door is for the more standard 9 pin metal plug socket for the hand held control unit.
A rough coat of paint to see how it all looks, yep, getting there nicely!
Time for some more decorative works. Panel lines have been scored in the bonnet side to represent the engine bay doors; and Mike’s louvre press has been in action again.
Now this is where Mike deviates from the true Drewry prototypes in that the wheels are solid items here. On the real ones they are cast with spokes and balance weights for the cranks; this engine will be fitted with cranks and rods in a similar manner to the two Ffesties have been.
The electrician has been, twin pole 100amp breaker fitted in the cab as the main on/off switch. The black plastic box with the toggles will become the lighting control unit; yes, Mike likes his bright LED headlamps!
The lights and horns relay box is fitted inside the cab; there are three relays; one for hi-horn, one for low-horn, the other is lights on/off.
Cab detail starts to go on, handrails and knobs. The doors apertures on this loco were cut out, and door panels made and fitted in behind to give some relief to this area.
The louvre press is back in action maing up the rest of the pieces! Who’s going to count them..!
Looking inside the chassis shows the full chain drive. Time to snip those bolts down a bit and start making the battery cradle.
More cosmetic works that add to the flavour of the finished loco, some steps for the front and rear. These are made from some U channel shaped bits of steel, amazing what you find in the skip at the laser cutters!
The channel test fitted for size…
Steps are an easy addition, some bits of plate or bar spot welded into position. Nice and easy!
Now we’re getting somewhere!!
The eagle eyed amongst you will have spotted a couple more additions; the horn and fuel filler caps have been turned up on the lathe and added on. These are bolted through the bonnet, with holes drilled and tapped into the underside of the piece.
Not forgetting the chimney pot of course!
A few more coats of paint went on to improve coverage on the yellow ends. Lamps have been made from small box section; these are to be fitted with LED lamps and some plastic lenses Mike obtained from the depths of eBay. He has managed to get hold of both red and clear; ideal for locomotives of this size.
Turning up the piece to hold the LED lamp… tiny little things!
Can’t see ever so well in the daylight, but the lamps are on!
The pair just about fit in the trailer together with an inch to spare!
The twins posing together, looking good I must say! It’d look better if the camera wasn’t dying at the time! New camera please…
Time to get cranky! Following the principles of the Ffesties, the laser cutters having cleared their backlog of work were able to crack on with our bits. The rods were cut as whole pieces, leaving Mike to bore out the holes for the needle bearings to fit.
We know this is not totally prototypical for a Drewry locomotive to have fly cranks such as this, but these are easy enough to fit up and negates the need for specially cast wheels.
Folks saying this isn’t prototypical for a Drewry loco should stop shaking their heads now… look what was found during a trip to Australia! One and the same… though 3 ft 6 inch gauge and outside framed.
Drewry No 4 was test run successfully in Spring 2012 and made a few visits out to the Lynnsport Railway in the years following, however the Gaffer’s attention was turning towards a petrol powered device that was to become the Sentinel!
Space issues forced the sale of Drewry No 4; it was advertised in the model engineering press and was bought by a chap from the Nottingham area, who is turning it into one of the Wisbech and Upwell Class 04s that Mike used to see when he was a child, the ones that inspired this whole project!