After several hours work I managed to clean up the remaining wheel castings despite stabbing myself in the hand several times with the very sharp ends of the needle files! The driving wheels were by far the worst and one had quite a few gouges in the spokes due to the 'fettler' at the foundry being none too careful with his grinder. Nothing that a bit of P38 filler won't put right though. P38 was also used to extend the balance weights for this pair of wheels. The wheels were then fitted to the axles and quartered as before. I had a nasty moment when gluing the second wheel on to one axle as the Loctite went off before I had got the wheel in the right place. Fortunately I managed to get it off again by some hefty twisting and after cleaning up again the second attempt went smoothly. As mentioned before, you can't afford to hang about once the axle is in the wheel.
Setting the driving axle
All four wheel assemblies were then fitted in the frames and I had a rolling chassis. Quite literally actually as the axles are so free that the chassis rolls down the slightest incline! Perhaps I should fit some brakes next!
The front and rear bogies were the next job. I decided to make these both exactly the same so all four bogie frames were produced at the same time by rivetting four pieces of 3/32" steel plate together and just marking out the top one. I wasn't keen on the simple design usually adopted where the axleboxes run in a square hole in the bogie frames as the only way to remove the wheel/axle assembly from the finished bogie is by taking one of the wheels off which seems a bit drastic! I therefore designed the frames with a slot open at the bottom and with a hornstay screwed across the bottom. The bearing surface for the axle horns will be increased by bolting seperate horn cheeks either side of the slots. The axles will be sprung using the usual equaliser bars and central springs. I am undecided at this point whether to incorporate side control springs on the bogies as most 2.5" gauge designs don't bother with it but I'm sure it wouldn't do any harm to try fitting some. They can always be removed if found to be unnecessary.
After rivetting together, the frames were roughly shaped with a hacksaw and then finished by milling and filing. I milled as many of the straight edges as possible to make sure that they came out square and true. Any angle on the edges would mean the four frames would finish up different sizes! The horn slots were finish milled the same way as those on the main frames.
,,,,,,,,,,,,,,,,,,,,,,,,,,Milling the edges of the bogie frames ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, Milling the horn slots
The finished bogie frames after seperation
The bogie centres were cut from 3/32" steel, again by rivetting both together while they were machined. Each has a rectangular slot milled in the centre to take a block which slides from side to side in the slot thus allowing the bogie to move sideways on curves as well as pivot. The usual brass angle was used to fasten the centres to the frames after maching it square as before. It really is a pain that the brass angle has to be machined square before you can use it! A simple round stretcher ties the ends of the bogie frames together.
I decided to fit side control springs after all as I am sure they will help the loco to negotiate curves. Two 1/8" dia. rods are mounted between the bogie frames and pass through clearance holes in the sliding block. Four springs will fit on these rods between the frames and the block and control the movement of the block. I think a bit of trial and error will be needed to get the right strength for these springs when the loco is ready for running. My assumption is that the bogie is designed to 'steer' the loco into the curves and it can only do this if the centre of the bogie can exert a force against the front of the loco frames i.e. through the side control springs. If the bogie is just free to slide from side to side without any restraint I can't see it doing a great deal except carry the weight of the front of the chassis. Perhaps there is normally enough friction between the bogie mounting stretcher and the bogie centre to have some effect?
Seperate horn cheeks were machined up from 1/4" brass angle and as 16 of these were needed, another production line job was set up. These are bolted to the frames with four 8BA bolts each. The bogie pivot pins were turned up from 1/4" dia. bar and two 1-1/4"dia. by 3/32" thick washers sliced off some brass bar to act as spacers between the bogie centres and stretchers.
I think it will be a long time before I tackle another 4-8-4 loco as there is so much repetition work involved! I've picked up a set of plans for the 4-8-4 4-8-4 Beyer Garratt loco but I don't think I could stand making two more 4-8-4 chassis's!
Part built bogies with side control spring pins
The axleboxes were machined in one piece from 3/4" square mild steel although it would have probably been easier to build them up as for the main axleboxes. Four lengths were cut and faced to length, drilled through a clearance size for the 8mm axles and then bored out each end to take the needle roller bearings. The centre section of each was then turned down for appearance sake although this was necessary for the front bogie axles in order to clear the middle cylinder and associated motion work. The remaining square sections at each end were then milled to fit the bogie horns, each axlebox being 'fitted' to its own horns.
Part machined bogie axleboxes
Last job on the axleboxes was to radius the inside flanges and this was done in the vertical miller using a similar setup to that used for the main axleboxes.
radiusing the axlebox flanges
The hornstays are simple lengths of 1/8" x 1/16" BMS held by 10BA screws.
One pair fitted and the other pair waiting
Some time was spent pondering on the best way to tackle the bogie equalising beams. Due to the size of the axleboxes the beams are quite deep and I don't think any available castings would have been suitable so I decided to try 'forging' them from 5/16" square brass bar. Suitable lengths were cut and milled to a taper at each end to reduce the machining required after bending. A former was cut from 1/4" mild steel plate and the idea was to bend the brass around this when heated with the gas torch. However, halfway through the first bend the brass just snapped like a carrot. Oh bother! (or words to that effect!). Obviously the bend required was too sharp and/or the brass too thick. Back to the drawing board.
I decided to go with one of my original ideas and cut the beams from solid brass bar. I had some 1/4"x 1-1/2" which I decided would be thick enough to take the holes for the centre springs. The beams were made in pairs by soldering two pieces of the brass together with the usual Carrs 188 solder paste. I thought it would be a bit much to try and cut all four beams together! Marking out the beams would have been quite a big job due to the various angles so I cheated by printing out the shape onto thick paper and sticking the patterns to the brass with double sided tape! The patterns had the centres of the various inside radii marked on and these were drilled with a small pilot hole. The outline of the frames was then cut out with a sharp knife. This marked the brass at the same time and meant that the paper could be removed for final machining work.
Brass blanks with paper templates
The pilot holes were then drilled out to 1/2" dia. to give the correct inside radii on the beams and the outline of the beams cut out with the hacksaw.
Blanks drilled and roughly sawn to shape
I didn't fancy finishing the beams by filing so I milled all the edges in the lathe. This involved some quite fiddly setups because of all the diffent angles but the job was finished without too much trouble.
..................................One of the milling setups!........................................Reducing thickness of beam ends
The remaining outer curves were finished by hand filing and after a bit of work with emery paper I had four quite presentable equaliser beams. Phew!
The four finished equaliser beams
The pins which pass through the middle of the equaliser beam springs were made from 3/32" stainless rod threaded at one end to screw into the bogie stretcher. The remainder of the pins were left plain so that the beams can slide up and down them easily. The beams were temporarily fitted to the bogies using some 3/16" diameter springs I happened to have but I think these will be too strong for the finished loco. Unfortunately it was not possible to fit the spring pins first and fit the beams afterwards so the beams were fitted in position complete with springs and the pins screwed in from the bottom. The threads were made a fairly easy fit so that the pins could be screwed in by hand and they are then locked with a nut on top of the bogie stretcher.
Equaliser beams, springs, and spring pins fitted
I'm off to Rugby tomorrow ( April 30th 2006) for the National 2-1/2" Gauge Rally so all being well 'Helen' will be making her first public appearance. There's a long way to go yet though till she moves under her own steam!
Helen's chassis behind my drawing and in front of a full size print of the original Josslin outline drawing