A early version Drop Centre in "O" scale part 2

Not much to report on but as I needed to take some progress photos I thought I would make another post anyway.

I have finished cutting out all the pieces and the first photo is of them all spread out on the table.
The score and snap method went much faster than cutting right through with cardboard. It only took a day but now I have a sore finger from pressing down on the knife. The edges needed much less cleaning up afterwards as well.

Like cardboard though I needed to resharpen the knife blade every few minutes and unlike card the first cut had to be very light so as to just score the surface otherwise the blade tendered to wander away from the straight edge. A bit like grooved rail the first cut provided a guide for the blade's second and heavier cut.

All the pieces that needed laminating have been glued together and were left sandwiched between two pieces of glass overnight. These pieces produce the window frames and doors etc. Only two of these pieces are handed and guess who glued them the wrong way round. It would have made the drivers doorway on the wrong side. So I had to make new ones of these. The next photo shows all the pieces in their approximate positions.

The next stage is the fun part. Assembling the model. It has been so long since I started the first one I have no idea what some of the pieces are for any more. Maybe I'll find out as I go along.

A early version Drop Centre in "O" scale part 1

My previous model was of a later version drop centre. This time I planned to model a very early version. These were built as handbrake cars from 1925 onwards and many still had not been converted to air brakes when the system closed although all the early ones had the open cabs enclosed. The museum's 231 is in this condition and still has it's diamond frame trucks which are part of another thread.


The main differences between the two versions by the 1960s was the lack of the metal skirt below the cabins and the drivers compartments and no side destination rolls. The drawing shows the general layout of these trams after the drivers cabins has been enclosed and the photo of 196 shows generally what they looked like by the mid 1960s.


All the converted ones had the diamond frame trucks replaced with plate frame trucks. So I will have to be careful that the number tram I choose still had the diamond frames in the 1960s.

Recently, I joined with a local model train club in the purchase of large sheets of polystyrene from a local plastics supplier. Armed with 4 sheets of different thicknesses I decided to try and make this model from styrene instead of my usual cardboard.

The styrene in some ways is not as versatile as card and I needed to spend quite some time on the computer altering and resizing where necessary all the different panels I needed. Where card can be bent when required styrene needs to be two separate pieces with the edges bevelled and then glued together.

I also did some experimenting with sticking printer paper onto styrene and found the best was spray adhesive sprayed onto the back of the printer paper only. When touch dry I pressed it onto the styrene and it stuck well but it could also be removed without too much trouble. So I have reorganised all the panel drawings to fit onto A4 size sheets.

It will be interesting to see how many mistakes I have made. The last photo is one of the sheets ready to be glued onto the styrene. And no, it isn't blue paper. My camera didn't like all the white and decided to make it's own adjustments.

Making maximum traction trucks. part 4

Everything stopped during the lead up to Christmas so not a lot has been done lately. The axles gears and wheels have been fitted to the chassis and the brass holders for the motors made. The driven axle is kept centred by the gear on the axle. I like a little sideways movement so the side frames were made a millimetre wider than necessary and a couple of brass washers threaded onto the axle along with the gear wheel which gave me just what I wanted. The pony wheels are kept centered with a piece of brass tube that is a sliding fit over the axle. The piece of tube has a hole filed in it at it's centre. When everything was lined up a dob of flux and a small amount of solder was used to lock the tube to the axle. Once the pick up springs are fitted and tensioned they will hold the axles centred but will also allow a small sideways movement if necessary while running.
The first photo shows a truck with the motor disassembled. I like to start off with the motor mounting set up so there is no backlash in the gears. Then I use cardboard shims to set the motor/worm wheel height so I get the correct backlash. Not enough and the gears will bind. Too much and the gears will jump teeth under load. Neither is desirable. I cut a square hole in the centre of the cardboard as well to make sure that the armature doesn't rub.

The brass tube in the centre is part of what will eventually hold the side frames in place. The top cover for the motor still has to have the pivot attached. Prototypically the pivot should be only about 2mm forward of the axle centre but I think I shall use a slightly more central position than that. Once the pivots are in place I shall be able to permanently set up the motors.


Now to get on with mounting the pivots and the pickup springs. Oh, and the sideframes. Seems there is still a lot to do.

Making maximum traction trucks. part 3

I have the side frames ready now so I thought I would share a couple of prototype photos with everyone.

I have to be careful what tram number I use on my new model that these trucks are being built for as most of the droppies had the diamond frames removed and replaced with plate frames as they were converted to air brake operation. Not many droppies remained as handbrake cars right up to the end and it is the last few years that I am concentrating on for my modelling.


The first photo is of the museum's droppie No 231 which was built in 1925 and was never converted. The rather delicate nature of these trucks is clearly shown in the photo. Restoration was started on this tram some years ago and was stopped for one reason or other. Although drivable it remains in a partially disassembled state with all it's bits stacked inside.

The next photo is of our spare diamond frame truck which is tucked away in the back of a shed. The bearing that it pivots on is on the triangular hinged plate just in front of the motor. Only about 75mm in front, and this caused the pony wheels to swing outside the tram body on sharp curves. Hence the protective covers over the pony wheels.


The rubbing plates that the body sat on are much further forward, at about 45% - 55% spacing between the driving wheels and the pony wheels. I guess that with the one and a half ton weight of the motor hanging to the outside of the driving axle there would have been very little weight on the pony wheels with this light weight truck so the designers moved the location of the rubbing plates forward so that they got the correct weight distribution between the two axles.

On my model I'm hoping to set the pivot point at about the same place so I will be adding some lead weight over the pony wheels to insure good electrical pickup. But not too much. With a rigid chassis like this you can only ever have three wheels in contact with the rails at any one time. It doesn't matter how accurate the chassis is or how well the track is laid the tripod principal still applies and one wheel will always have marginal contact. I would prefer it was one of the pony wheels so there is always two wheels driving on each truck. A compensated chassis would solve the problem and I have built these before but I'm too lazy these days.


The last photo is the finished truck sideframes cast in polyurethane.

I hope to have the motors etc mounted in the next few days but Christmas is getting closer and closer and time seems to be becoming a premium item.

Making maximum traction trucks. part 2

The bore in the Romford/Jackson gear wheel is 1/8" as are the flanged bearings. The Romford/Jackson wheels come fitted to 2mm axles and gauged for HO. Ideally the axles should be all steel but without a lathe I can't do the machining that would be needed. So I use hard brass tube from the hobby shop. I reckon it's ok for my tram models because my models are lightweight, won't be pulling 100 wagon trains, won't be running continuously, run slowly and added to that I use the long axle bearings so the wear is distributed over a quite large area. Anyway so far hard brass has not shown any signs of wear. I just have to remember to keep a drop of oil on the bearings.

I am using HO scale wheels and the back to back dimension for HO is 14.55mm +0.05mm -0.15mm. I add 15.5mm to that to get the back to back for O scale using HO wheels. The difference between 16.5mm and 32mm. So I end up with a back to back that should be 30.05mm +0.05mm -0.15mm. 30mm is near enough and suits me just fine.

I use the nesting brass tubes you can get from the hobby shop. I started off with the 1/8" OD hard brass tube and selected the next tube down in size that nested inside the first. I cut 4 pieces of the smaller size to a length of 28mm as the insulated hubs on the wheels stand proud of the rear of the wheel by almost 1mm.


Then I cut the pieces of 1/8" tube to a length of 25mm and slid the smaller tubes inside the larger. I soldered the two tubes together on the ends. The top photo shows the stages of construction.


The bore on the inner tube is too small to allow the 2mm axles to be inserted so they needed to be drilled out. This is where a lathe would be handy but my method works just as well if a bit slower. The advantage of using tube here is provided everything is set up reasonably accurately a 2mm drill will track down the dead centre of the axle and give me a wobble free wheel.


The table of the drill press was checked to make sure it was still horizontal and a 1/8" hole was drilled through a piece of nice flat pine. Then I sawed a narrow slot down the pine and through the centre of the 1/8" hole. With an axle inserted into the hole I used a G clamp to close up the saw cut which grips the axle. This trick will hold the axle tight enough to drill out the centre but at the same time not mark the surface in any way which would interfere with smooth running.

I cut the wheel sets in half so I ended up with wheels and stub axles still attached. The fit into the axles was firm. Just too tight to do it by hand so I used the drill press as a wheel press as can be seen in the next photo.

All the wheels have been pressed into one end. The other end will be done after the axles are assembled on the trucks. Each unit was lightly clamped into the drill press chuck and given a spin to check for wobble. None so far. I checked the blackening on the wheels with a multimeter and the coating is conductive but I will polish it off the rear of the wheel where the pickup springs will rub just to be on the safe side.

Making maximum traction trucks. part 1

Am I the only one. I just received an order of gears and wheels from Britain. A lifetime supply probably and have just realised I forgot to order more axle bearings. I have just enough for one more tram and then....

I'm about to start an older version of the Brisbane droppie. These earlier models were originally mounted on 4' 6" diamond frame trucks. I like to build the trucks first as their the final height determines what I do with the floor. I prefer to use the Jackson/Romford gears but the larger diameter of these means the motor is mounted too high for a full under floor mech.

Over the years I have settled on my own method of constructing mechanisms that suits the tools I have. It's a combination of many other peoples ideas and it works ok for me.

I cut out the two side plates and two more pieces of scrap approximately the same size. The two side plates were stacked on top of each other and soldered together at the ends. Just enough solder to hold them. Then I filed the assembly to insure the plates were identical. This time I used printed circuit board for the scrap so I had to glue them to the side plates. One tiny drop of superglue at each end as they had to be removed later undamaged. The first photo shows the assemblies ready for drilling.


With everything stuck together I drilled the bearing holes out with a 1/8" drill in the drill press. This part of the job was critical because if the holes were not vertical the truck would not run properly. After removing the printed circuit board pieces I drilled out the bearing holes to take the Romford flanged bearings and then separated the two side plates carefully. I have found out to my annoyance in the past that if a plate gets bent separating them, even though it is easily straightened, it does not return to the same size. In a much longer wheelbase like a 6 wheel loco it causes wheel alignment problems.

The second photo shows all the parts ready for assembly. The small pieces of brass are my frame spacers. I made these my cutting a strip of brass and filing it to make sure it was a constant width. I then cut and folded the brass so that all the spacers were exactly the same width. The two sets of truck parts must be kept as sets. Very important.


Next I soldered three frame spacers to one side plate and using a square and a sheet of glass to position the second side plate I soldered it to the spacers as well. Up to this point, apart from drilling the holes vertically, accuracy wasn't all that important. The next bit squares everything up.

I have a couple of 1/8" rods about 50mm long to represent the axles while I solder the bearings to the side plates. I fitted the four bearings with the flanges on the inside and threaded through the 1/8" rods. This is where I used the printed circuit pieces which still have the original 1/8" holes. They were threaded on to the ends of the 1/8" rods and held the axles parallel. I then sat the whole assembly on two machined aluminium blocks I have which were in turn sitting on a sheet of glass. This made sure that the two axles will be in line with each other and hopefully all four wheels will sit on the track. I don't want one wheel sticking up in the air.


The third photo shows the setup. The bent piece of brass in the photo is a piece of hardened brass being used as a spring to hold the flanges of the bearings against the inside of the plates while I soldered them on the outside.

The last photo shows progress so far. Next I will have to get on with mounting the motor and the brackets for the polyurethane side frames.

A Card model of a drop centre in "O" scale part 5

Another model that has been sitting around for quite awhile has been finished, well almost. The final items. the window glazing and the adverts are done but as I was taking the photos for this post I realised that I haven't finished the headlights. The model sides and interior have been sprayed with a couple of coats of Testors glosscote and reflections on the model make it look as if it has only been half painted in places. I can assure everyone that this is not the case, The model was sprayed by airbrush.


Most of the roof ads are from photos I took of the ads on the museum's droppie and were modified, recoloured and resized using Paint Shop Pro. Printed onto photographic paper they were then given several coats of Testors glosscote before being cut out and glued to the brass boards.



I still call this a cardboard model but some other materials found their way into this one. There were some things that cardboard was just not suitable for, The roof ad boards for one as it wouldn't have been strong enough. These were made from shim brass with brass wire soldered on the back for the mounting brackets. After several attempts to make the seats I decided to make them out of Evergreen V grooved styrene sheet. The original seats were made up of individual slats and the V grooved sheet has worked out well.


I have drawn out the patterns already for the next droppie, an earlier model without the lower skirt and I think that this one may be a styrene version. The large number of cardboard edges in this model were difficult to finish off properly. Something that is much easier in styrene.

I shall soon have a number of different thickness, full size styrene sheets at the right price so I am holding off starting the next model for awhile. But I have been experimenting with different ideas in marking out the paterns on the styrene. More about that in a future post.

For now I'm happy to get this model finished and move on to a couple of other projects. A fellow museum member did masters and has lost wax castings for most of the sideframes that were used on Brisbane trams. With his kind permission I am about to start producing masters suitable for polyurethane casting from his originals for the diamond frame trucks used on the earlier droppies and the Brill trucks used under the centre isle cars. So there is plenty to keep me going for awhile.