Not wishing to re-invent the wheel, I used Doug Hewson's design for a ground level 5" truck as featured in 'Engineering in Miniature'. I bought 8 slices of 4" free cutting EN1A steel at £3.44 each, which turned into nice neat wheels, although I now think they ought to be a bit bigger.
Time will tell. The ballraces came from Ebay in a pack of 10 for a silly price. The framework
for locating the wheels and axles is a bit fiddly but I managed to make a simple jig using the drawing and panel pins
as shown in the photo, which is enough to hold the bits for tack welding.
Welding is rather crude, but black paint hides a lot of sins! The completed job looks quite nice with the polished
brass end caps against the black. Note the nylon rollers.I always have the problem of how to carry both engine and tender together on a trailer. The trailer I made was quite big enough to take both, but I decided the engine being that much heavier than the tender, would put too much load on one side. Talking to a friend about this problem when he said he'd solved the problem ages ago. He made his tender in two parts so that the body could be lifted off and put in the car boot and the tender chassis could be turned on its side and put in the trailer broadside on. So that is how I'll build this one.
When it came to deciding on
suspension, I considered springs, but found when I'd used them before, the truck was easily turned over if I leaned
to one side. So I've used rubber blocks as on my last one. The rubber comes from car exhaust supports cut to a
convenient length. I finished them to size on a linisher; somewhat smelly! It makes a stiff suspension but does
take out most of the shocks. The nuts are 'loctited' and the bolts have free movement in the holes to take up
any movement.
I thought a long time about brakes. The ones on Doug Hewson's are vacuum operated but really I wanted parking brakes
which can be used when the engine is not in steam. Putting brakes on to bogies is not difficult but to set up a lever
system to operate them is not easy due to the movement of the bogie.
One of my club members always makes his brake
blocks from a cast aluminium ring but I can't help thinking ally on steel doesn't have much frictional grip. Aluminum
tracks are notorious for poor traction. Anyway, I made one and clamped it to a wheel as best I could and found I
could still turn the wheel quite easily. I don't like the idea of any metal rubbing on another metal as a means of
braking. I would have liked to have used cycle brake blocks, but there isn't enough depth in them to cut a curve to
match the wheel. So I'm trying 'tufnol'. I've no idea whether it will work; the friction seems OK and they look just
like wood which means I'm about 50 years out of date!
The next problem I have design wise, is the lack of space for the hangers and the method of pulling the blocks on. I hope I'll come up with a solution.
I did make up a system but there just isn't enough room between the wheels, so I abandoned the thing and started all
over again and this is why I haven't done much.
I reverted to cycle brake blocks and a system I've used before.
The inside of the wheels is a perfect flat and ideal for a block to rub on. I've made a 5" driving truck with this
system and even wrote an article for EIM on it. It works well until it gets contaminated with oil!
This time, I've made a more substantial job without the play in the pivot points which I had on the original. I'd used
a bowden cable as a means of pulling the brakes on. I think I've improved on that by using just rigid components.
When the rod on the right is pulled, the brakes are expanded onto the wheels' inside faces. Any natural forward motion
tends to tighten them even more. To cope with the movement of the bogie, there's a compensating bar across the 'A'
frame, so that no matter how much the bogie moves, equal pressure is applied to the blocks. - I hope!
Still to
consider is where to place the spring to pull off the brakes. This is essential as the blocks only have to touch and
the forward motion makes them grab on. By coincidence, when fully off, the compensating bar comes up against the main
cross member and stops the whole lot wobbling about and in danger of touching. A good strong return spring somewhere
should help this.
The 5" truck had brakes on both bogies connected with the bowden cable, but this time I've only
got brakes on one axle. This is enough for a parking brake. The vacuum system operating brakes on the carriages will
do the main braking anyway. It should be sufficient to have parking brakes on the engine and on the tender. The surface
area of the cycle brake blocks is about the same as four conventional ones and have a much better grip.
It took me a while to come up with a way of making the handle so that the top could be lifted off without having a
large hole in the floor. To avoid this large hole, I've made the handle a screw fit into a block welded on to the
upright. It's a bit of a dog's dinner but seems to work. There is a simple ratchet on the inside and to release it,
the rod with the black knob on the top is pressed down and the spring is strong enough for the handle to fly off.
The main problem lies with the ratchet. The teeth have to be big enough to take the load, but the bigger they are the
less the adjustment. As it is, the main fault with this system is the lack of movement of the handle. It would be so
much easier if the brake blocks were softer and had a bit of 'give' in them; they'd also grip more firmly. Being new,
they are not a flat fit on the wheel and need bedding in. They remind me of the car I learnt to drive in; Hillman Minx
1933 and fitted with Bendix brakes. Worked well going forwards but tied the car in knots going backwards. This
is the opposite, the brakes grip tighter as the truck moves forward. Had I used both axles, I'd have had one of each.
I've removed the single buffer-coupling from the engine because it put too much distance between the tender and the
engine. I've replaced it with a simple block and I can get the space between sorted with a connecting bar cut to length.
As can be seen from the picture, I've put it on the back of the tender instead. I now have to consider how the top
bodywork is to fit, also, what sort of water tank to fit. Plastic might be a possibility; certainly cheaper than brass.
I have drilled holes in the chassis ready to take water and vacuum pipework. This completes the tender chassis and it's
now ready for painting.
I've made a start on the bodywork which is mainly plywood. Unfortunately, the woodwork shop/paint shop/welding shop/
store i.e.the garage, is unheated and freezing cold, so not a lot has been done. On top of that, I sold my Kerr Stuart
loco and with some of the money I've bought a bench top CNC milling machine.
There have been problems with the CAM software and it has taken me a while to get it to work. Anyway, that's my
excuse for not having done very much. I had quite a few false starts, but did cut this tiny handwheel. I thought
if I could manage something as small as this with a 1.5mm slot drill, then I'd have no problems with bigger stuff.
Now I'll be able to make the handwheels for the backhead.
One problem with using either, is that the end grain is very obvious, even when painted. To overcome this, I've
covered all edges with angle. It is thin, rolled steel and can be bought at the local DIY shop. It has very little
weight. The hardest part to make was the curved angle on the front leading edges.I've used round head, brass screws
which, when filled, will look like rivets, all 150 of them! I will fill all the screw holes of the main frame with a
filler of some sort. Then comes the job of rubbing down and priming. Lots of coats will be necessary to make the
wood look like a metal finish. The board with the hole in, in the photo, is the base of what will be the padded seat. This lifts up for access to the water tank and a tool compartment. The water tank may be a problem. I still haven't come up with a way of making it. I don't really want to go to the expense of using brass as the cost is now very high. I did think of lining the section with fibreglass, but thought the top might prove difficult. So at the moment, I'm looking for a plastic container of some sort, preferably with a screw lid.
The whole thing looks a little wide but is an inch narrower than the engine, although the buffer beams are the same size. There is space for two people as I'm thinking that when my grandchildren want to learn to drive, I want to be within reach of the controls! I'll need to fit some sort of foot rest for the rear passenger, while the driver has his feet in the well. It's a bit wide to sit astride but I've tried it out and I think it will be OK for an adult.
I brought the subject of the water tank up with some friends at a club meeting. I said I was thinking of using aluminium and caulking the seams as it was easy to work. It was suggested that there might be a chemical action with the water and affect the steel boiler. So why not line it with acrylic which is quite cheap. I got to thinking about that and I had a large piece left over from the cab windows. But why bother with aluminium; why not use wood, after all, it's only acting as a support for the plastic.
So I began by making a box to fit the space available. A marvelous adhesive for acrylic is cellulose thinners; it
dissolves almost instantly and sticks to anything even wood. But to be sure of watertight joints, I went over the
joins with silicone sealant; the type that can be immersed in water. The lid was a different matter as it needed
an inside lip to stop surges going through the gap. This I made of aluminium and screwed it to a wooden lid. I made
a bung from a lump of nylon. I still have to make the water tap connection.
The cold weather has not helped the drying process for the paint. Multiple layers of primer don't seem to have made
any difference to hiding the grain! Rubbing down between coats has given a nice finish, but it's plainly obvious that
the tender is made from wood. The MDF didn't have this problem. While all this paint work and waiting was going on, I
decided to have another go at the ugly firedoor. A sliding bar seems to be the solution. There is no fouling of the
handle against the brake handle support and the door can be opened right back on itself if necessary. The door is
still a good fit against the backhead. With this system I didn't need to have the blowdown tap right down as there
is plenty of clearance. This is what happens when "fag packet" designing as you go along.
While I've been waiting for the paint to dry, my little CNC mill has been working overtime and I've managed to make five
handwheels for the manifold. It has not been without its problems. Apparently the hardware needs to be connected via
the com port which the latest laptops don't have, so I'm having to use the USB port, which it doesn't like. Now and
again it decides to turn off the power for no apparent reason and starting again in the place where it left off has
so far been impossible and so it means starting again with a new chunk of brass! Still, it's early days.
These last two photos show the finished driving truck/tender. I'm not quite as happy as I'd like to be with regard
to the finish because of the wood grain but I suppose the full size trucks were made of wood though I doubt tenders
were. The angle round the edges proved to be a bit of a problem when lining because the white line tended to run on
to its edge. I've used another commercial ball tap for the water supply to the loco and the pipework is a bit complex
because I wanted the tap as far out of the way of my feet as possible. I also used 10mm tube which will feed into the
1/4" outlet giving maximum pressure to the injector. The hole in the ball valve is about 8mm.
Well that's about it until the boiler test day which is March 20th. In the mean time, I will have to get the new trailer ready with track and lock down points. I shall also be thinking about making a lamp and nameplates. I'll also be running the loco through a pressure test at home, just to make sure there are no leaks and also to get a rough setting on the safety valves. I'm not sure when the next update will be, but probably it will be straight after the boiler test when hopefully I'll have photos of it running on the track.
On the theory that if you wait long enough, it will appear on Ebay; I did eventually find a pressure gauge the right
size. There were plenty of 4" but none around 3". Then this 80 mm one appeared. It is new but not quite in keeping
with the loco as it is chrome plated, so some time I'll make a brass bezel which should improve the appearance.