Hobbyhorse Three Green Boxes


Western Thunderer
What's the next project be after the A4, well looking at the pile of unbuilt kits the three Finney 4-4-0's, Duke, Atbara and Bullbog have taken my fancy, mainly because of the similarities with them needing the wheels, crank axles, fly cranks, tender sub frames and bearings all needing machining. With the lathe setup for machining the wheels doing them together makes life a bit easier and saves a bit of time.
So building three at the same time could be daunting, but with the prep work on the above done before cutting out the etches it makes sense. And as I've not finished the research on the individual locos yet, times on my side with lots of machining to do which will keep me busy for a while.
So with panto patterns for the sub frames, crank webs and fly cranks and various jigs to hand, the build starts.
Starting with cutting the tender sub frames, cut from .9 brass these make life a lot simpler with using tender wheels without the extended axles. Using some square brass as frame spacers, these I'll make once I get to that stage in the construction.



Western Thunderer
Next on the list is the Fly Cranks, I had some already in stock from a previous model so only needed to make 11, which gives a few spares. Profile cut from EN1A steel flat, it does machine OK but does need some cutting fluid to improve the finish. The holes for the axles and crank pin are put in with the cutter when profiling, then over to the jig for final drilling and reaming the holes to size. Next is to relieve the rear on the lathe, fitted to a mandrel it's a careful process which doesn't need a lot of material removed, the photo of the process shows it fitted with the crank pin which is a bit out of order as I forgot to take it before fitting them. Last job was to press in the crank pins.



Western Thunderer
I've been working on the wheels this week, with the first two stages completed. These are trueing the spigot and machining the front face. The next stage is to work on the rear face, for which I need to do some work on the soft jaws to hold each size of wheel before this can commence.
Other jobs completed are the axles for the bogie and tender wheels, these are screw in type, and the horn blocks which have had removable keepers added.










Western Thunderer
This week I’ve completed the bogie and tender wheels. Following on from the last post the first job is to remove the spigot and machine the rear face and expose the spokes, this is done in the four jaw chuck using the soft jaws which have been machined to the wheel diameter, care is needed as it’s very easy to destroy the wheel.
Next is to make up the insulating bushes from tufnol and glue into place with an Epoxy type glue, then into the oven for one hour at 100 degrees, this sets the glue hard. Then the wheels are placed back into the four jaw chuck, then drill and reamed for the axles to be a tight fit. I’m double insulating these, but you can insulate one side and tap the other wheel for the threaded part of the axle to screw into, this works very well but I prefer double insulation these days. Once all the wheels are reamed these can be press fitted onto the axles, I fix the axle into the headstock and use the tailstock to press them on, starting with the threaded axle first then screw on the plain axle section and press on the remaining wheel, ensuring the spokes are in line and set the back-to-back with the gauge. The final job is to remove the excess axles and machine the centring hole in the axle to fit the jig to check if all is concentric.













Western Thunderer
Before completing the driving wheels I've put together the Flower chassis and basic inside motion parts, which went together with out any issues. This gives the opportunity to check all the dimensions for the cranks axle. The distance between the horn blocks is 19.5mm and the centre line for the piston rod was 15mm. Given these dimensions some adjustments would be need as the crank axle definitely wouldn't fit, so 60thou was taken off the cylinder block to bring the centre line down to 13.5, which was cut in half shown in the photo and reassembled with some brass strip to reinforce the joint and strip added to the edges to bring it back to width. 15 thou was also taken off the crank webs. This brought all the dimensions into line with a clearance of 15 thou between the horns and crank axle.
What this has taught me is it's probably better to assemble each chassis and not assume the other two kits will be the same and check the dimensions before assembling the crank axles.
Next the Driving wheels.











Western Thunderer
The final stage with the driving wheels is completing the plain and crank axle.

First job was to machine up the axle parts, the plain and crank one differed slightly because of the tapered pin positions. Both sets use the same jig for quartering.
The crank webs are reamed to size in pairs, with the the small ends machined to size with stepped down ends fitting into the webs, these also gauge the crank to the correct spacing, and a packing washer and bar fitted to the free end, this allows all to be kept spaced and inline during the silver soldering.
A similar process was used when soldering the axles to the webs, unfortunately I didn't photograph this stage.
After the soldering process the parts require some cleaning.
Setting the quartering was done on a jig I made up some time ago, once the centre line is established it's just a case of drilling and reaming for the tapered pins. Fitting the wheels and establishing the back to back measurement is slightly more difficult with outside crank locos, using a gauging sleeve that is pushed on with the wheel this sets the distance perfectly, once the mathematics have worked out with the sleeve size.
What this has taught me is it's probably better to assemble each chassis and not assume the other two kits will be the same.



Crank axle parts

Reaming the Webbs

Ready to solder


Quartering, drilling and reaming for the tapered pin

Axle quartered and ready to remove the axle between the webbs

Gauging sleeve ready to push wheels on

Axle split

Checking the completed axle, ready for the eccentrics to be fitted


Western Thunderer
Next job is the bogies and as these kits are designed to use extended axles some modifications are needed. I’m not that keen on captive wheels as it makes construction a little difficult, so as my wheels rely on inner bearings I’ve made some simple sub frames which screw to the main bolster. I’ve inverted the bearings to allow the frames to be reduced in width, this keeps them clear of the loco main frames.
Also adding a bit of shape to the sub frames reduces the visibility of them when looking from the front of the loco.








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Before starting the other two chassis I wanted to have a go at improving the bogie springs and axle boxes, those supplied with the kits are rather delicate and prone to damage. So using some brass and white metal castings and machining up the triangular mounting plates, these are substantially more robust. I’m not fixing the spring assembly to the bogie’s until these are painted.







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Good progress with the Duke and Bulldog frames with no issues assembling them, very similar to the Flower.
Silver soldering the two cranks and the cleaning process is something I always enjoy, the bit I always have a bit of trepidation with the final assembly, drilling and reaming for the tapered pins. Having reamed countless cranks and axles over years I managed to snap the reamer, thankfully in the last axle and not the crank web which would’ve been a disaster. It was easily removed from the axle, and was to the correct depth thankfully, it's replacement isn't cheap unfortunately so time to raid the piggy bank.
With the axles pined together a trial assembly in the frame proved all square with enough clearance around the cranks and the rods revolved without binding.








Western Thunderer
Quite a bit of progress this week.
First job was getting all the driving wheels mounted on their axles, and checking all was square and the quartering was OK.
Next the outside frames for the Flower, Duke and Bulldog was assembled onto the main frames, it's a little bit fiddly getting the buffer beams square to the frame being slightly higher.
The last two bogie frames again fairly straightforward in assembling, other than modifying them to accept the new sub frames.
One problem I did encounter was the Duke and Bulldog was riding a bit high, the instructions are a little bit ambiguous about the compensation beams, so after working out the correct height I milled off the top of the bearings to lower the frames.








Western Thunderer
A bit of a diversion this week, making an adjustable back stop for the guillotine.
I've had it for over 20 years and seeing a friends guillotine fitted with one on a recent visit, the time has come using the design on his one. All the bits I've had in stock so it was just the case of adapting the design as it came together. Nothing to complicated other than ensuring good fits on all the sliding parts, with reamed and bored holes and ground stock for the bars. The DRO didn't have any locking mechanism, this was an easy fix adding one.











Western Thunderer
Back onto locos after the guillotine.
First job was modifying the motion brackets and cylinder faces to allow the con rods and eccentric rods to all run parallel with the new centres on the crank axles. This was achieved by removing 1.5 mm from the central section of both and then packing out the edges to be a snug fit in the frames. The valve glands was an easy fix by soldering on to the central cut in the metal and re drill the various holes, and opening out the central hole to allow the valve rods clearance.
Next the con rods needed modifying as the design makes them captive, having them removable makes life a lots easier. As the etches are handed it was straightforward to file what was the bottom to represent the top details, and to fix them after painting I'll makeup a small bearing plate which will solder onto the bottom of the rod.
Getting the eccentric rods to run parallel needed some packing washers between the eccentric pairs and to separate them. Adjusting the widths of the washer has allowed a fiction fit for the eccentrics between the cranks, which seems to hold them in position.
Not sure if I'll permanently fix them onto the crank axle yet as it's very useful having them removable.
Quite pleased with the progress but it did take quite a bit of time with the various mods, but pushing the chassis along with no tight spots is good news.





This shows the con rod tops, one modified to show the details.