adrian
Flying Squad
Having spent the couple of weeks before Christmas finishing off a few projects I now have a little room in my erecting shop to start a new project and new projects are always much more fun.
The New Year heralds a new start and the new build started is as per the title a Finney7 4200G Std Tender. Now given the number of LNER builds on WT I was sure I could find a 4200G build but I have to admit I couldn't find any. If someone knows of one then please point me in the right direction.
I'll pose the first question for people. I was intending just to cover the details where I deviated from the instructions but given my inability to find another build then I'm happy to cover a complete blow by blow account of the build - what would you like to see - just the off off piste stuff or all the gory details?
Lets get onto the build. The first thing to mention is that if you speak to them nicely the Finney7 mob are willing to supply their kits in nickel-silver for a small markup. The small increase in price over the brass version is well worth the cost for the ease of construction. Nickel-silver is far superior to brass for soldering, painting and construction etc. it really isn't worth opting for etched brass.
I started with the wheels - these are Mark Wood's castings. I build in Scale7 so if I bought Slaters wheels I'd still have to skim them and reprofile them so it was just as easy to go with the cast wheels. I also wanted to explore what could be done with insulated hornblocks and split axles.
So previous efforts with split axles used @Steph Dale 's published solution with 2mm fibreglass rodding for insulation. This worked well for tender axles but I felt it was slightly lacking in torsional rigidity. The fibres in the glass fibre rod are all aligned longitudinally and so it was possible to twist them a little, as I say not a problem on a tender but on a loco with coupling rods I was looking for something a little stiffer. Using the castings allowed me to use 4mm diameter steel axles (for reasons covered later), with a steel telescopic section (7/64" as that was the reamer I had!). The insulated side was also drilled 7/64" and a length of tufnol rod turned to be a friction fit.
A spot of loctite on the tufnol and then popped in the lathe and with a thin parting tool an insulating groove cut in the axle.
Then pressed on the axles and then drilled for a taper pin to lock them together.
Now onto the first deviation - the tender chassis. As usual I tend to go my own way! As supplied the kit is designed to build a compensated chassis and it will do that very well. However I'm not a great fan of compensation as there is always a rigid connection between axle and tender (or loco). I much prefer a sprung chassis but in this scale the usual miniature coil springs are fiddly to setup and balance. So my preference is the "continuous springy beam" (CSB) suspension which to my view is the best of both worlds - a compensated sprung chassis. Yes this is a CSB conversion - I used the existing chassis frames to mark out the cutouts so that I replace the fixed axle and compensated bearings with the Finney7 hornguides.
Using the Scale7 spacers supplied in the kit. The photo above also provides a clue as to why I went for the 4mm axle diameter.
The hornblocks are actually 3D printed items - printed in a nylon for insulation they include a vertical tab for the CSB arrangement and crucially with a 7mm bore so that I can fit a ball race within the hornblock. 7mm ball races having a 4mm id hence the axle diameter. Hopefully my cunning plan becomes more apparent as the build progresses.
Once the hornguides had been soldered in I could assemble the chassis on a glass flat plate to build it flat and square.
The other light-bulb moment was trying to arrange the fulcrum points for the CSB on the chassis. On my previous builds I've soldered on L shaped brass angle with a hole drilled in them for the spring wire. I realised that this was unnecessary - all that was required was a fixed fulcrum for the spring wire to act against. So to keep it simple I have just used a length of 1mm n-s wire across the chassis to act as the fixed fulcrum points - these are the two rods that can be seen between the horn guides in the photo below.
Hopefully the arrangement will work and become clear in later posts as the chassis is assembled.
So full gory detail of the build or just the off piste diversions?
The New Year heralds a new start and the new build started is as per the title a Finney7 4200G Std Tender. Now given the number of LNER builds on WT I was sure I could find a 4200G build but I have to admit I couldn't find any. If someone knows of one then please point me in the right direction.
I'll pose the first question for people. I was intending just to cover the details where I deviated from the instructions but given my inability to find another build then I'm happy to cover a complete blow by blow account of the build - what would you like to see - just the off off piste stuff or all the gory details?
Lets get onto the build. The first thing to mention is that if you speak to them nicely the Finney7 mob are willing to supply their kits in nickel-silver for a small markup. The small increase in price over the brass version is well worth the cost for the ease of construction. Nickel-silver is far superior to brass for soldering, painting and construction etc. it really isn't worth opting for etched brass.
I started with the wheels - these are Mark Wood's castings. I build in Scale7 so if I bought Slaters wheels I'd still have to skim them and reprofile them so it was just as easy to go with the cast wheels. I also wanted to explore what could be done with insulated hornblocks and split axles.
So previous efforts with split axles used @Steph Dale 's published solution with 2mm fibreglass rodding for insulation. This worked well for tender axles but I felt it was slightly lacking in torsional rigidity. The fibres in the glass fibre rod are all aligned longitudinally and so it was possible to twist them a little, as I say not a problem on a tender but on a loco with coupling rods I was looking for something a little stiffer. Using the castings allowed me to use 4mm diameter steel axles (for reasons covered later), with a steel telescopic section (7/64" as that was the reamer I had!). The insulated side was also drilled 7/64" and a length of tufnol rod turned to be a friction fit.
A spot of loctite on the tufnol and then popped in the lathe and with a thin parting tool an insulating groove cut in the axle.
Then pressed on the axles and then drilled for a taper pin to lock them together.
Now onto the first deviation - the tender chassis. As usual I tend to go my own way! As supplied the kit is designed to build a compensated chassis and it will do that very well. However I'm not a great fan of compensation as there is always a rigid connection between axle and tender (or loco). I much prefer a sprung chassis but in this scale the usual miniature coil springs are fiddly to setup and balance. So my preference is the "continuous springy beam" (CSB) suspension which to my view is the best of both worlds - a compensated sprung chassis. Yes this is a CSB conversion - I used the existing chassis frames to mark out the cutouts so that I replace the fixed axle and compensated bearings with the Finney7 hornguides.
Using the Scale7 spacers supplied in the kit. The photo above also provides a clue as to why I went for the 4mm axle diameter.
The hornblocks are actually 3D printed items - printed in a nylon for insulation they include a vertical tab for the CSB arrangement and crucially with a 7mm bore so that I can fit a ball race within the hornblock. 7mm ball races having a 4mm id hence the axle diameter. Hopefully my cunning plan becomes more apparent as the build progresses.
Once the hornguides had been soldered in I could assemble the chassis on a glass flat plate to build it flat and square.
The other light-bulb moment was trying to arrange the fulcrum points for the CSB on the chassis. On my previous builds I've soldered on L shaped brass angle with a hole drilled in them for the spring wire. I realised that this was unnecessary - all that was required was a fixed fulcrum for the spring wire to act against. So to keep it simple I have just used a length of 1mm n-s wire across the chassis to act as the fixed fulcrum points - these are the two rods that can be seen between the horn guides in the photo below.
Hopefully the arrangement will work and become clear in later posts as the chassis is assembled.
So full gory detail of the build or just the off piste diversions?