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.
No comments:
Post a Comment