I have been an avid reader of much subject matter on RMWeb in the past so I thought it was only right that I try to adjust the balance and post my experience to possibly help or guide others.
Before I begin my effort, many thanks to those who have taken the time to write about their experiences with J71s, Bogie Van Bs, B1s, point construction and almost everything else…….my post won’t be as accomplished as theirs but I am sure that there will be those who can guide me as I publish instalments. Please feel free to comment/advise/criticise/praise if you feel the need. I will try to respond to any comments as and when I can.
My specific interest is 7mm around the start of the 1960s with a slant on the railways of Hull around that time. After years of thinking about it, I have eventually started to build a layout, a loco and some rolling stock. Slowly but surely I believe I have managed to improve…….
There has been a huge amount of dialogue within the Gauge 0 Guild about the future of the hobby. Costs are one of the usual concerns and the problems of younger modellers finding enough disposable income (as well as space) have been discussed. It follows that lower cost kits and ready to run locomotives have a possible role in ensuring the hobby continues to flourish. PR Model Railway Products (PRMRP) are one manufacturer which provides low cost kits. (It is another matter if younger persons can develop the skills to build them!)
This series of posts are about the PRMRP Class 50. I know it’s not Hull in the 1960s but I am building this one as a gift for someone………
There isn’t a great deal of information on the construction of PRMRP 7mm diesel kits so after starting, I thought I’d share my progress. I have built etched brass stuff before but I am a long way from being proficient so what follows is not how to do it: just a journey.
I know that PRMRP get a lot of criticism in the railway blogs, and I am well aware that the kits are not top dog…..but I am not a top dog builder so it seemed a reasonable project…..relatively low cost and if I improve my skills (and patience) I can always go back (if necessary) and upgrade the basic build with, say, cab details and other accoutrements?
It’s a long story but I already have a Class 31 for which I have bought specialist motorised bogies so I have the necessary bogie etchings which are common to all the PRMRP kits, as well as motors and gears etc. I asked Peter Besant if he could supply a Class 50 without etched bogies and he kindly offered a discount and brought one to Telford where I picked it up.
The kit comes as a number of etched brass sheets with a body in one piece. The body is pre-shaped. Mine had a number of creases which proved difficult to remove satisfactorily despite Peter’s advice to tweak them out using a round metal bar. All other bits and pieces are in sealed polythene bags. Unfortunately, I decided to write this after I started so there are no photos of everything as it was in the box……sorry!
The instructions are sparse so it’s a bit of an adventure sorting everything out and making sure it’s in the right place. The drawing is small and poorly reproduced so I scanned some from Diesel Rail Main Line Diesel Locomotives by Colin J Marsden and Graham B Fenn. (I found a brand new copy recently at my local railway (Mid Hants) and paid the princely sum of £1 for it). I enlarged them on Photoshop so that they are near as damn it to scale, before printing them off. I also have access to a Class 50 on the railway. 50027 Lion is one of the preserved locos there so I was able to add a load of close up detail photos to the file.
An example:
So much for the introduction. On to Part 1! The bogies………and apologies for the varied quality of the pictures.
The inner bogie frames are flat and must be set to the right length before being bent to shape. The sheet is marked with half etched lines parallel to the ends and these are used to set the correct length of the frame. (If I hadn’t already started the frames this would be a little clearer). The following picture shows a couple of the lines on the right after the excess length was removed. The instructions give the dimensions for each class of diesel, and show which half etched line where the break must be.
The frame is then bent into a ‘U’ shape which is reinforced with spacers.
As I said earlier, the frames are universal for all diesels so each frame has different axle spacings depending in the class you are building. The distances are set by utilising sliding saddles with the axle holes in. Once the distances are set, the saddles can be soldered in place giving even more rigidity.
Here are the separate pieces bent to shape. Notice the shape of the spacers which have an inset to allow for Delrin drive chains. (More of this later). I fixed the spacers in place before the saddles.
I found setting the correct axle centres (relatively) accurately to be quite difficult. The saddles can’t be fixed in place until this is done. I set the distances on my Hobby Holidays loco frame jig. This fixed everything in place at the right location and I soldered everything using a gas torch.
The end result. The bearings are still to be fixed in place.
I have read a lot about Delrin systems and although I have no personal experience, while (whilst?) I was at Telford I came across some 7mm belt drives on the M&M stand. They are supposed to be quieter so I decided to give them a go. After fiddling around for a while I found that they were an exceptionally tight fit and as well as setting the saddles on the jig, I also checked the belt drives to make sure they would go on before everything was set in stone. I’ll find out when I fit the axles into the bearings).
The belt…..
The belt drive check set up…….
The axle centres are set to the correct distance but the belt is very tight and I’m slightly worried that there will be too much friction and also the possibility of distorting the bogie frame. I’ll test the drive as soon as the bearings are soldered into the frame to make sure the motor can drive the axles smoothly without overloading.
The white metal bogie outer frames are in two pieces which need to be soldered together. In the photo, the lower pairs are in two halves, the top pairs are assembled. The spigots on the bottom part locate into half round slots in the rear of the top half.
I almost always solder white metal parts together with low melt solder and a gas torch. With care it is much easier than trying to get heat into large parts with an iron.
The finished article (except for some minor flash still to be removed and the blue tack holding the two parts together).
Day 2
I put the bearings into the frames and fitted the axles. The pulleys slipped and I added the worm wheel to the driving axle. With the belt fitted, I pushed the axles through the opposite bearings and was about to fit the motor when I noticed that the worm wheel was off centre by some distance.
I contacted Malcolm at M&M and he immediately agreed to send me two of his narrow pulleys in exchange for the oversize ones so thanks to him!
The next job is to solder the outer frames to the stretchers, and fit a plate onto the inner frame, then drill the relevant holes so that the outer frames are removable..........
