Adams "O2" - Calbourne

[Cro]

Does building a patio count? I've engineered the radius of it to suit a potential garden railway...?
Adam

[springcrocus]

Bunker bulkhead

Ive now made the bunker forward bulkhead along with the two seat boxes, the shovel plate, coal hole door, door rails and the ledge which extends back to the rear spectacle plate. As can be seen, it's all simple cutting and drilling. The brass angles are riveted to the platework with the heads on the inside. On the visible side, they have been hammered flat into decent countersinks and filed flat.



I've added extra angles around the base so that the bunker assembly can be screwed to the rear soleplate. This is the bunker assembly screwed together with the coal hatch sitting in the runners and the top ledge attached to the bulkhead.



With the rear spectacle plate set in position, I can now mark out and fix the other angle to it. The angle will rest on the ledge when in display mode but will not be fixed to it. The spectacle, door arches and roof will be removed as a unit when it is on the track. I can also replace the two temporary side angles with narrower ones to match the crossways angle.



I wasn't happy with the spectacle plate - it was a little out-of-square - so I've remade that. The replacement angles have been made and are mitred to the crossways angle, and this time I've riveted them to the spectacle plate. This is a simple setup for creating mitred ends.



I've also made the locating arrangement for the fronts of the doorway panels. A section of plate has been silver-soldered to the inside of the panel and a catchplate made for the lower section, held in place by the stanchions for the exterior handhold. It's basically an adaption of the permanent fixing that DY had drawn. The tab needs to be marked and cut to fit the slot milled in the back of the catchplate



With the tanks and the bunker bolted into position, I was able to make the tab to size and there is also a little movement available in the catchplate holes to allow for fine adjustment.



And one more photo showing the bulkhead with the coal plate and hatch in position. The spectacle plate looks better now, as well, with the narrower angle. I just have to drill a couple of holes and solder a pair of locating pins to the crossways angle.



My wheels should be arriving early next week so I will probably get those done next.

Regards, Steve

[springcrocus]

The wheels arrived today and that will keep me busy for a day or two. So to keep the thread momentum going, and in time-honoured fashion, here's a little something I did earlier.

Window Guards

Calbourne has two protective covers over the rear spectacles to stop coal breaking the glass. There are a couple of ways one could make these but I chose to make mine from a solid billet rather than try to solder bars onto the cover plate. DY suggests the same in a note on the drawing and Nigel has made his in a similar fashion.

Two billets were cut from 2" diameter mild steel bar, each about 5/16" long. This is a job that lends itself pefectly to soft jaws and a set were machined to suit. The jaw recess is only 45 thou deep but plenty enough to get a good hold on the material.



The billets were faced on one side and the o/d turned to 1.850". Then the billets were reversed and the other side faced to leave them 1/4" thick. Again, the o/d was turned to 1.850". Next, the inside of the billets were bored using two different boring bars and finishing with a third boring tool with a large radius.



The billets were reversed in the chuck and the outside turned first, followed by the external radius which was blended in by eye. The flange thickness is 1/16", hence why the jaws are only bored 45 thou deep.



From here, it was over to the mill with the chuck and the waste milled away to leave the protective bars. The drawing is wrong because DY shows six bars over the windows but Calbourne only has five. It may have had six in earlier times but that's not what I'm modelling, I'm representing the loco in it's current form.



Four slots were cut using a 1/4" diameter end mill, working down in 25 thou passes until the cutter just touched the flange. By moving over 5/16" on each slot, I finished with bars that were 1/16" thick.



The final two sets of passes on the outside formed the outer bars. Some additional filing was required because of the underside radius but they've come out looking not too bad. These will be cleaned up properly later and, once painted, should look quite respectable.



Regards, Steve

[GWR 101]

Steve, great work and a perfectly engineered solution. Regards Paul

[springcrocus]

Coupled wheels

I've managed to get a set of coupled wheels that were surplus to requirements from someone on the Home Workshop website and I'm pleased to say that they were quite decent castings with no chilling anywhere except on the edges of a few spokes. To start the ball rolling, each wheel was loaded to the independant 4-jaw chuck and the inside of the rim clocked as true as practical.



Then the tyre was faced off to leave about 3/16" clear of the spokes and the o/d turned to well-above finished size to give me a reference for the next operation. Luckily, there is plenty of material on these wheels. I am not making separate tyres but I will continue to use the term to refer to the wheel tread.



Next, the 3-jaw S/C chuck was mounted to the lathe and the wheels loaded into hard jaws. I need to take another 60 thou off the front so they were faced off at 0.600". I'm working to the profile and dimensions on the Britannia drawings, rather than Don Young's, because they tally with the GL5 standard. The o/d was also turned to 5.175" at the same time and the axle hole drilled 12mm diameter.



From this point on, I went to soft jaws and there were various operations to face the front, turn the maximum tyre diameter, bore and ream the axle hole, undercut the rim down to the spokes and form the radius at the root of the tyre. The soft jaws are only bored 1/16" deep so the centre is just for a bit of support in case of a dig-in.



The wheels were reversed once more and a 1/16" rim machined on the back of the wheel. Then the shape of the flange was machined on using a tool I keep just for this sort of job, a double-sided tool with approximately 1mm radii.



The final turning operation was the coning to the wheel and the axle bore. These were both done without removing the wheel from the chuck to guarantee concentricity. The compound slide was set to 2.1/4 degrees and the toolpost returned to square. The tyre was turned using the compound, running out at the root of the radius and the axle hole was bored, two passes for trueness, to 13.8mm followed by reaming at 14mm.



The coupling rod pins were next and a simple fixture was constructed with a 14mm dimeter peg for the axle bore and a screw to act as a locating lug for one of the spokes. With everything clocked out on the mill, each wheel was centre-drilled, drilled and reamed 8mm.



The last job was the keyway for the axles and I re-used a broach that I made about seven years ago for the Britannia wheels. I did have to modify the guide bush, though, and make a new alignment peg for the coupling pin hole. The setup can be seen resting on the drilling machine table and the timber baulk is there to support the front of the table, otherwise the pressure could break the casting. Three passes were needed to get the depth.



If anyone wants to see how I made the broach, I've just revamped the original article as a NEW THREAD in the Tools section. Meanwhile, here is a nearly-completed wheel.



Before I make and fit the balance weights, I want to get to Havenstreet and see the loco again. My instinct says that DY has got his left and right mixed up so I will check for myself.

Regards, Steve

[springcrocus]

Barrel and smokebox ring

The barrel has been machined to length by holding in the bore and supporting the other end in a steady. My steady wasn't large enough to use the rollers so I set some PTFE pads on the outboard ends of the arms and then reversed them. With a drop of lubricating oil, they worked fine. This isn't locked down yet but it shows the pads in place.



Although it had been sawn reasonably square and didn't really need to be cleaned up, I faced about 20 thou off the first end. However, for some unknown reason, I ordered an overlong piece and decided to part the surplus off. The ring will come in handy one day. I cheated, though, I only parted about three-quarters of the way through then hacksawed the last bit before finishing the face with the parting tool.



The barrel ring was made using the lump of bronze that I trepanned from the Britannia front ring. Once again, I started by trepanning out the middle, going half-way through then reversing the billet. Rather than just turning the outside into swarf, I cut a thin ring from the outside as well. I don't have a use for it yet but one day...



These are the three billets that were produced, the middle ring the one that is needed. I hate wasting material of this value.



The outside diameter and one face were machined square to each other, then the billet was loaded to soft jaws and practically all the machining done in a single operation; two bores, the front spigot and the o/d with it's radius. The radius tool is just in the picture. The offcut from the copper tube was used as a gauge.



That left nearly 1/8" to come off the back and the spigot for the smokebox backplate to be machined. A register was turned on the outside of the soft jaws and the work held in the front bore. Then it was faced to length and the spigot turned to finished size. Most of the machining was done at about 350 rpm and using the feedbox whenever I could.



This is the barrel with the smokebox ring fitted to the end. A few countersunk brass screws will be used to hold it all together and these will be concealed beneath the cleading.



Regards, Steve

[springcrocus]

Crank webs and journals

I am making my crankshaft from multiple parts fitted together rather than machining from solid. There are four crank webs to make, the two outer ones being thinner than the two inner ones. I am making the later version because that is what Calbourne has now. Four pieces were cut from a section of 38mm x 8mm black bar.



All four were cleaned up all round, albeit thirty thou overlength, with the two outer ones thinned to 1/4" and the 5/16" ones given a polish on the linisher. The holes were were put in next, working to a backstop, drilling each hole, then boring to near size before reaming with a 14mm reamer. The DRO allowed for very accurate positioning.



An old mandrel was re-used, turning the O/D to 14mm for a snug fit in the reamed holes. An M10 cap screw was used as the clamping bolt.



The webs were loaded in turn and the diameter turned until cleaned up, then a further fifteen thou taken to bring to finished size.





The various journals are simple turned items but the 14mm diameter spigots needed to be pretty accurate and run very true so they were machined using the independant 4-jaw chuck.



The first parts to be fitted together were the webs and con rod journals. They were supposed to be a 2-thou interference fit but they were nearer a thou. To keep the axle journals square, they were pressed together using the mill vice. The piece of ground flat stock resting on the moving jaw was placed on top of the work and the quill lightly pressed down while the vice was tightened.



Meanwhile, keyways were milled into the remaining journals and a 1/8" diameter hole drilled and reamed through each for later alignment but, because these are also only a light interference, they will be adjusted for radial position at assembly time. After final assembly, all the joints will be drilled and fitted with taper pins.



That's the mundane stuff out of the way, the next bit is where it gets interesting, in my opinion. Getting the keyways accurately into the eccentrics will be a nice challenge.

Regards, Steve

[springcrocus]

Keying the eccentrics

Before I start on this, a note to prospective builders of this locomotive. As far as I can see, Don Young failed to record anywhere on the drawings what angle to set the eccentrics at. He probably hadn't got a clue and expected the builder to tinker around with the angle until something worked. The only drawing that offers any insight scales out at about 245 degrees to the centreline but that isn't much help to a builder. Nor is it very accurate.

I asked Nigel Bennet what angle he had used for his "Ashey" and he very kindly sent me a drawing of his one-piece design for the whole eccentric assembly. This was a little too complex for my poor old lathe, better suited to CNC turning, but it showed that he had chosen an angle of about 260 degrees. I then spoke to Wilf (uuu) and asked for some help and he drew out the valve gear in his CAD program. We decided to aim for 10 thou lead steam in mid gear and this produced an angle of 261 degrees, so pretty close to what Nigel had done. This was the angle chosen and later references to 9 degrees are three-quarters of the way round (270 degrees), then back 9 degrees.

I'm probably missing a trick here but, as I see it, the hardest part about putting keyways into the eccentrics is an alignment issue as it's very difficult to accurately true up the offset bore. To get round this problem, I decided to drill a pair of accurate locating holes in the eccentrics and fashion a simple fixture to load them to.

The first job was to put the locating holes in so the eccentrics were loaded to a 3-jaw chuck on the mill and a pair of 2.4mm dia holes drilled on the centreline. With that job out of the way, attention turned to the fixture.

This was made from some 1.1/2" x 3/8" flat material, loading to the 4-jaw chuck and boring a recess at one end to be a snug fit to the eccentrics.



The fixture was then taken to the mill, clocked up square in the vice and the centre of the recess found. I needed this to be particularly accurate so took my time and double-checked everything. A pair of 2.3mm holes were drilled at the same co-ordinates as the eccentrics and a 3/4" diameter clearance hole drilled and bored 5/16" from the centreline. An M10 tapped hole was also made for a clamping point.



After pressing a pair of 3/32" iron rivets into the 2.3mm diameter holes, the fixture was taken back to the lathe and loaded to the 4-jaw chuck, clocking out on the 3/4" diameter clearance hole (which was the reason why it was bored rather than just drilled). The eccentrics were loaded in turn and the offset hole drilled and bored to size. I could have done this on the mill but it's easier on the lathe; too many tools to keep swapping out on the mill.



It would have been easy to make a mistake with orientation when cutting the keyways so I printed off a screenshot of the Dockstader arrangement that I have been using and marked the crank webs and the slots with a felt-tip pen. With the con rod journal to the back, the eccentrics lean forward by 9 degrees. I've chosen to offset the keyway by 45 degrees because, otherwise, one of the keyways would be in the thinnest part of the eccentric and probably break out.



To cut the keyways in the correct position, I needed to be able to align the broach at 45-9=36 degrees to the perpendicular for two of the eccentrics and at 45+9=54 degrees for the other two. The fixture was modified with a pair of fences bolted to one of the sides and the front to become guideways. It was then clamped to my rotary table on the mill and the longest side clocked true. I don't need to bother about any other reference at this point.



The scale marker was zeroed and the table wound round 36 degrees. Now it was trued up on the 3/4" clearance hole so that I could mill a 3/16" slot in the first fence for the alignment peg. Then I had to repeat the operation at 54 degrees for the other one. I've wedged a piece of 3/16" thick ground flat stock in one of the slots for clarity.



With the fixture complete, I moved on to putting in the keyways. I had to make a collar for the broach guide to lift it from 14mm to 5/8" diameter, then cut away the slot area. I also made a couple more shims for the back of the broach. Here is the setup for the second pair of the keyways showing how the guide bush is supported. The front fence/guide has been removed as those ones are finished.



After all four were made, they were cleaned up and assembled to the eccentric journal. It took a few tries to get them lined up in the correct order and the right way round but I got there in the end. The inset shows an end view of the arrangement.



I've recorded the arrangement because I need to dismantle this again. The eccentrics need a locking screw to stop them moving sideways on the shaft and it will be easier to get the journal pressed into one of the webs first, then build up the journal again.

Regards, Steve

[jma1009]

Hi Steve,

Very much enjoying your description of the crank axle and eccentric settings etc and use of key ways.

Also very pleased you were able to acquire suitable driving wheel castings.

I am quite sure that Don Ashton would have approved of your eccentric key way setting, and also their angle of advance of 9 or 10 degrees.

Marvellous work backed up by a lot of stuff and research by yourself and others and with valve gear computer simulation.

Cheers,
Julian

[springcrocus]

Driving axle built up

Before I could commence the final build of the crank axle, I had to put the locking screws into the eccentrics. Once again, the fixture came in useful as a means of supporting them. I have drilled a 3.5mm diameter hole about 3/4" deep followed by drilling through 2.5mm and tapping M3 since I have a good amount of grub screws this size.



The eccentric journal has to fit into the first web at 45 degrees and an alignment aid was set up on the mill; a pair of angle plates set square to the table and a pair of fences at 45 degrees, a tight fit to the webs. It's a bit Heath Robinson but more accurate than it looks, even though I'm using a carpenter's angle for the webs.



With a length of 1/8" diameter silver steel through the reamed hole in the keyway, it's a simple matter to get everything in alignment. Without this, it would have been far more difficult to set up. Before I pressed the shaft into the web, I replaced the support packing between the two webs to ensure that I didn't bend anything.



The eccentrics were loaded to the journal and checked, rechecked and checked again to make sure I had them in the correct orientation as it would be difficult to dismantle after the second crank is pressed on. The next picture shows the setup, much easier than trying to explain. The lower crank is clamped to the table and all packing is in place.



I've been pinning each joint as I went along but held off on this one for a moment. I wanted the cranks to be as accurate as possible so the vice was clocked true, the pinned crank held in the vice and the side face of the other one clocked out. I needed to ease it round a tiny bit and my large adjustable spanner gave me enough leverage.



Afterwards, this joint was also pinned.



That just left the axlebox journals to be fitted and these were assembled, one at a time, in similar fashion to the earlier parts. Once again, the 1/8" diameter reamed hole, perpendicular to the keyway, allowed for accurate alignment. The coupling rod pins sit opposite the crank pins so the keyways were set towards the cranks. Early on, I decided to use Sellock pins instead of taper pins because it's a heck of a long way through for a taper reamer. These are 2.5mm diameter by 30mm long hard stainless pins, pressed in straight after drilling.



After putting the keys in, I had to remove them again as they wouldn't fit through the bearings. A trial run with the bearings fitted into the horns and all is well. The axle rotates freely and, even at maximum depression, just misses the stretcher to the rear. I was half-expecting a collision here but it seems the draughtsman got something right on these rubbish drawings.



A few more parts to make (or remake) and it will be time to assemble the full drive train.

Regards, Steve

[terrier060]

Bit late I suspect now Steve, but did you put oilways though your cranks? On my Terriers I have made reservoirs in the main axle that holds oil, and cetrifugal force oils both the cranks and the eccentrics. The reservoirs are filled through the centre holes in the axles which have spring loaded balls to keep the oil in!
Ed

[jma1009]

I personally very much dislike the use of roll pins.

A properly made press fit crank axle ought not to require pining anyway, but I am not adverse to a belt and braces approach, but I would never use roll pins in such a situation.

(I've had to repair 2 crank axles, and made 3).

I've pinned them with stainless rod loctiting them with Loctite 601.

[springcrocus]

Each to their own, Julian, I quite understand your personal aversion to roll pins. From my side of the fence (as a lifelong machinist), I have used them in industrial situations for a very long time and they do the job they are designed to do, and do it very well.

The risk of breaking a 3/32" taper drill or reamer over a distance of 1.1/4" is so high as to be considered foolish to attempt. Back in the old days, I learnt that eight times diameter was the maximum for a non-interrupted cutter, CNC peck-drilling being the only exception. My only 3/32" taper reamer is a smooth-flute type, although I do have 1/16" and 1/8" interrupted-cut reamers (a bit like roughing end-mills for those who haven't seen one).

It should be possible to construct a model locomotive without using any adhesive at all. Gluing pins into place sounds a bit of a "get-out-of-jail-free" card to me. If you make the hole correctly in the first place, why would you require an adhesive?

As I indicated at the beginning, we all have our favourite way of doing things. None of them are wrong if they work.

Regards, Steve

[ettingtonliam]

Julian - care to share with us the reasons for your intense dislike of roll pins? I like taper pins, but only in locations where, periodically, they may need to be removed, and IMHO, thats not in a crank axle. I'd have used 1/8" silver steel, largely because I've got some, and I don't have any roll pins. As Steve says, nothings wrong if it works.

[jma1009]

Yes, Richard, I will try.

But before, let me attempt to explain that Steve's initial proposal of the use of taper pins is not the correct starting point, and I agree with Steve as inappropriate. For crank axle webs.

I think the first time I encountered roll pins was in Jim Green's 5"g "Polly" when I reset the valve gear sometime in 1997. All the motion linkage had hardened steel roll pins that had worked loose. So as one example the weighshaft arm to the reach rod. They were deformed and loose and very difficult to remove.

I think we would all agree that a crank axle web has more pressure on it than a weighshaft arm linked via the reach rod to the reverser.

A crank axle if pinned requires solid pins either press fitted in or a sliding fit with loctite.

I don't have an issue with collars fitted with roll pins.

Cheers,
Julian

[ianholder]

I have built several crank axles over the years and have always used the following assembly method, so far without failure. This is probably just a personal thing but I do not like cross pinning the cranks. there is a lot of racking forces on a crank axle and if the fit of the axle in the crank is at all doubtful the crank can start to pivot round the cross pin. Instead I use pins in line with the joint usually two at 180 degrees. I use Loctite 638 High Strength when I assemble the axle. The axle parts and crank pins are turned to a close slide fit without shake in the cranks, I drill a hole through the axle parts so the whole thing can be assembled on a length of silver steel to keep it all in line. Each part is fitted in to a crank web and after cureing pins are fitted in line with the joint and loctited in. You could use threaded pins if you are a belt and braces man! You will realise that you need to plan the assembly so that you can drill for the pins in each joint. You will note that I use a close slide fit in my Loctited joints, there is no need for clearance to allow room for the loctite or to turn a 'cotton reel' as so many recommend. Loctite is designed to fill the microscopic crevices in the joint and enough will be taken in when you assemble the joint with a twisting motion. The reason this clearance requirement seems to have arisen is the tolerance in dimensions that Loctite give that will still allow a strong joint. The closer the fit the stronger the joint, but also the tighter the fit the quicker the loctite goes off and you don't have a lot of adjustment time.

[springcrocus]

Jun 23, 2022 23:53:47 GMT terrier060 said:

Bit late I suspect now Steve, but did you put oilways though your cranks? On my Terriers I have made reservoirs in the main axle that holds oil, and cetrifugal force oils both the cranks and the eccentrics. The reservoirs are filled through the centre holes in the axles which have spring loaded balls to keep the oil in!
Ed

No chance, Ed. All the oil would leak out of my alignment crossholes under the keys. Old-fashioned oiling for me.

Julian, I expect your "Polly" had poorly-fitted cranks in the first place. Mine have all been a very firm press-fit; indeed, most of them required that I hung my weight on the handle to get them home. The pins are probably not needed but, as you say, "belt and braces".

Wheel assembly

Before I could assemble the wheels to the axles, I had to fix the coupling rods pins into place. These were a light press-fit done on the drilling machine but, belt and braces again, I used a locking screw to keep them in place. The wheel was held on the pin using a collet block.



The block was then loaded to the milling vice and an M3 tapped hole made on the perimeter of the pin. There is an M3 grub screw down the hole.



Following on from that, I needed to fabricate the balance weight plates and these were cut from 20swg mild steel for the backs and 16swg brass for the fronts. I've also engraved the wheels as left driver, right driver, left coupled and right coupled so that they go back in the same place after any future dismantling.



The front axle was made at the same time as the bogie axles, so no need to cover that again. I did need to put the keyways in the end, though, and converted the fixture I made for the Britannia axles. It just fitted end-to-end which saved having to make a whole new block.



The wheels are kept in radial alignment with the keys and I have set a locking screw down through the hubs at 20 degrees to keep them pressed back against the shoulder. The wheels are a stiffish fit to the axles but don't need hammering on. No doubt I will get told off for doing this as well but I want my wheels removable.



The balance plates have been drilled and fixed with 8BA screws and the gullies between the spokes can be filled with some lead or printers metal, whatever low-melt material I can get hold of. Once cast and set, the fronts of the screws will be sanded off flush. The bolt-heads on the back will just be painted over.



The axles have been asssembled, set into the frames and the coupling rods fitted on. By some stroke of good fortune , the wheels turn with just the tiniest high-spot at one point in their revolution. This should work it's way clear after some running time.



Now I just need to make the eccentric rods and remake the eccentric link pivot with a slightly shorter offset. Then I can start building up the valve gear.

Regards, Steve

[jma1009]

Hi Steve,

I've never owned a 'Polly'. I sorted out Jim Green's example as described. 'Polly' doesn't have a crank axle.

I would like to think you would give some attention to the bosses on your driving wheels as these are very distinctive.

(I am happy for the Moderators to transfer my posts re roll pins to your other new thread).

[terrier060]

Hi Steve

You might find this interesting. This is the Craven Quartering Machine at the South Devon Railway. I am going to write an article about it when I can get down there when they are using it. The wheels are keyed accurately on the axles, but the final quartering is done on this machine, where the crankpins are machined with the wheels on the axles. Amazing piece of kit! Craven Brothers of Manchester made a lot of heavy workshop machinery for the railway works as well as cranes etc. The tools in the wooden box are the measuring equipment required for setting it up - they are French!

Craven Quartering Machine Details by ed cloutman, on Flickr

[springcrocus]

Eccentric arms

I decided to mill these from solid and silver-solder the fixing bracket to the arms so started by milling some 12mm black bar down to 3/8" square. Although I had enough 3/8" square BMS in stock, I was concerned about the possibility of them going banana-shaped after machining. The forks are offset from the main arm and the top and bottom arms have different offsets. The fork also finishes at 3/8" wide by 5/16" thick.

I milled the channel in each of the forks first using a 3/16" slot drill, finishing at 9/32" deep to prevent the sides collapsing. The arms were machined next, two milled to the first size and two to the second.



All four were then milled to 5/16" thick, removing the support web in the process, and the arms were thinned to 1/4" wide.

Four mounting feet were cut from 1/4" x 1/8" flat steel and a 1/4" wide slot milled by 1/8" deep to fit the arms. The 6BA clear mounting holes were also drilled at this stage.



Taking care to get them the right way round, each of the feet were silver-soldered to the arms. They are numbered 3 and 4 to match the drawing numbers, it's easy to get them mixed up.



I had deliberately made the arms 1/32" overlength and they were now trued up and brought to length as a single operation.



It seemed important that the four eccentic rods were all the same length but, because the arms get bolted to the eccentric straps, there was the possibilty of getting cumulative errors. Therefore, the arms were bolted to the straps first and the pivot holes in the forks machined next.

I used the base and pillar from my tapping fixture to act as a back-stop. Using the vice to grip the lower arm of the fork, the upper arm of the fork also needs support and a piece of 3/4" x 3/16" gauge plate was used between the arms. Loading to the vice with this in place sets them square in the both planes plane.



The packer was then be moved back to the end to allow the drilling to proceed. They were centre-drilled, drilled and reamed 5/32" diameter.



The forks needed to be thinned to 3/16" wide at the back and a fixture was made to support the eccentric rods. A 3/16" wide spacer was made to fit between the arms of the fork and an M4 cap screw used to bolt this end down. The other end was supported on packing and clamped over the top. An equal amount was milled from each side.



After this, it was all hand-work. All the fancy shapes were filed or linished, then finished off with sanding drums in the dremel. The four rods were temporarily assembled with the expansion links on the bench to check that all would go together correctly and to get an overview of the arrangement. To get the 7/16" spacing needed for the valve guide, there is only 1/16" spacing between the forks.



DY seems to favour tight-fitting, flush pins in the forks to carry the expansion links but I'm not in favour of this. I decided to make shouldered pins with a 1/32" thick head and to create a recess in the arm of the affected forks to set the head into. "E" clips were used on the outer ends to retain the pins because they are in fresh air. In the next picure, I'm setting up to cut the groove for the clips and using a tool inspired by one of our members. I'm pretty sure it was either Stevep or Gary L, I can't remember which, but I've shamelessly pinched their idea and made my own tool. Thanks, chaps, whichever of you it was, and apologies if it was someone else entirely.



The last photo shows one of the pins assembled and the recess on one of the other arms. I've just noticed that I also need to file the titty off the loose pin in the picture.



Regards, Steve