99 3462 Build diary

[mbrown]

Coupling rod joints

As a break from making the brasses and wedges, and with only a couple of hours of workshop time today, I have finished the joints between the three sections of each coupling rod.

Nothing fancy - the pins are 3/16" silver steel, with a 5/32" shoulder to fit the front of the forked section of rod, and a turned washer and 4 BA half nut complete the job. The middle sections are bronze bushed with a No.70 oil hole. Bog standard stuff, but another step forward.


20221119_172051 by malcolm brown, on Flickr


If I get any workshop time tomorrow it will be back to the brasses....

Best wishes

Malcolm

[mbrown]

The Joys of On-Line Research

I commented in an earlier post that 99 3462 is currently having a major overhaul at the Dampfkleinbahn Muhlenstroth, including the provision of a new boiler, and how much I would like to be able to get out there and see her in stripped-down condition. However, funds and time - plus the rather frosty response by the DKMB to my initial enquiries - make that impossible at present.

Browsing the DKBM website the other day I spotted some photos of the overhaul in progress - and found a small goldmine! The shot below of the chassis from the rear is, like all locomotive workshop shots, a bit cluttered with parts laying around, but it does resolve a question I had not answered in my initial exploration from the pit at Weisswater on the WEM in 2019 - what does the rearmost row of rivets on the top plate connect to? I had noted that the frame stretcher below extended only as far up as the longitudinal stay, so there was a gap of some inches with nothing, apparently, to rivet the top plate to. Now all is clear - it seems to be some sort of stiffening angle, about 100mm deep on the prototype, with short legs connected to the frames. A simple piece of machined-down 12mm angle will deal with that on the model. This photo has all sort of other useful details when blown up on screen.


IMG_5828_big by malcolm brown, on Flickr


Incidentally, the long tubular arrangement lying on top of the frames to the right and resembling a rather limp steel tulip, is a silencer for the blowdown - but this is a post-preservation addition which I won't be copying.

But the real gem was this superb shot of the ashpan. There is so much clutter between the frames at the back that, when I was down there, the ashpan shape was hard to discern and impossible to photograph. Now here it is in all its glory. Those of us used to ashpans on Britannias, A3s and so on will need orienting - this is looking at 99 3462's ashpan from the rear, with the big damper door visible. There are some interesting angles that I will need to reproduce, somehow, in a small fabricated version. The big loco has water jets directed into both the smokebox and the ashpan to wash ash down to where it can collect properly. That may explain the obviously rotten sections at the bottom. No doubt 99 3462's new boiler will get a new ashpan too. I won't be reproducing the water jets, but I will still make mine of stainless if I can.


IMG_5540_big by malcolm brown, on Flickr

So, thanks to the excellent photography of the team at Muhlenstoth, I can get some of these details right without trekking over to Germany.

Best wishes

Malcolm

[mbrown]

Slow progress on the Side Rods


A further six hours or so in the workshop this weekend, and the intermediate side rods now have their brasses, wedges, adjusting screws and oil box lids.

The brasses are solid at this stage. I will set the rods up on the mill table and bore them to DRO dimensions, hoping that I have maintained enough accuracy all through the construction to enable them to fit nicely. The frames were CAD-drawn and laser cut with the horn openings 89 mm apart, the horns were assembled and then finished on the mill at 89 mm apart and the axle boxes were all bored in the lathe on a jig, so the axles should also be 89 mm apart. We shall see....


20221127_181258 by malcolm brown, on Flickr


There is a small crescent gouge from the milling cutter on one of the brasses - we all make mistakes.... But it should disappear when the brasses are faced to thickness and have the shallow boss turned on them.

Only another four sets to do, on the end sections of the rods. The continental approach to loco design seems to be to make as many things adjustable as possible. The British approach (bore a hole and press in a bush) has a lot to recommend it, I reckon.

Best wishes

Malcolm

[stevep]

A friend once said "If you can't make it accurately, make it adjustable".

[mbrown]

Centre Coupling Rods

Judging from the small number of constructional posts lately, I guess I am not the only one on this forum who is finding it hard to get any real time in the workshop these days. But I did manage an hour or two today and have managed to bore the brasses in the central section of the coupling rods.

These were done on the mill, using the DRO to get the centres exactly at 89 mm.


20221211_182159 by malcolm brown, on Flickr


Once drilled to just below the finished bore, they were reamed by hand - 3/8" for the driving crankpin and 5/16" for the second axle.

Reamed holes on unmachined silver steel make for a somewhat tight fit, but they went on with a bit of oil to help. And, although they are very stiff and it takes a good push to get the axles to turn, they go around with no noticeable tight spots. All the brasses except the ones on the driving crankpin will eventually be eased slightly to allow for rough track, but to get the wheels turning smoothly without that easing feels like an achievement. It is the result of (late in life) adopting modern methods by drawing the frames in CAD for laser cutting, machining the horns on the mill to the DRO readings, and boring the crankpins and quartering the wheels with jigs.


20221211_183405 by malcolm brown, on Flickr


The end sections of the coupling rods may be a tad trickier to get exactly right because of the joints. I'll have a go at them next weekend, all being well.

Bests wishes

Malcolm

[stevep]

If you try to run the engine with reamed brasses on silver steel pins (which is normally right on nominal size), you will almost certainly get binding when going over uneveness on the track. At least wobble the reamer around to create a bit of additional clearance. I actually prefer to drill the brasses with the next size drill up - metric or imperial, according to whichever size the silver steel is.

[mbrown]

Thanks Steve - I do indeed intend to ease the bores - but, to be honest, I was vain enough to want to see if I had made everything accurately enough to turn over without easing them! So, now that I have had my moment of feeling smug, they will come off and get opened up a little. I also need to face the brasses off and turn the fronts as on the coupling rods. Still some way to go before they are all finished.

Malcolm

[gwrfan]

Dec 11, 2022 19:17:04 GMT stevep said:

If you try to run the engine with reamed brasses on silver steel pins (which is normally right on nominal size), you will almost certainly get binding when going over uneveness on the track. At least wobble the reamer around to create a bit of additional clearance. I actually prefer to drill the brasses with the next size drill up - metric or imperial, according to whichever size the silver steel is.

Hi Steve. Been looking at my 5 inch Dukedog just lately. The original builder got something a bit out with the cranks and pins, and the coupling rods got very tight in one position, and as you will know, it's only 2 axles! I bought one, and then another 'next size' drill to open up the 3/8 reamed bushes, but it wasn't enough. I then bought a 3/8 inch expandable reamer and slowly opened it up until the rods eased somewhat. At least the wheels go round now, haha. And the reamer was new and only about £9 - cheaper than the 2 drills I bought!

Hope you are surviving the cold weather in Oke?

Geoff

[mbrown]

"If you can't make it accurately, make it adjustable...."


Steve's comment above has proved remarkably apposite.... I have now got the rear sections of the coupling rods fitted and turning over smoothly, but it took a lot of trial and error to eliminate the binding and I made full use of the adjustable characteristics of the wedge-adjusted brasses.


Because of the knuckle joint between the centre and rear sections, and because of the difference in thickness of the coupling rod sections, it wasn't easy to set the rods up accurately on the mill table so, this time, I didn't set out the holes on the DRO but used old fashioned methods. The trammel, below, is one I made for a previous loco and, with a new hole for one of the pins, it could be made to serve on the wheelbase of this loco. One of the centres is adjustable within a slot, and that enables them to be fitted accurately to the centres in the ends of the axles. As I had hoped, both sides were the same. The un-bored brass was then fitted into the rod, a plug with a centre in it was put into the adjacent crank-pin hole, and the other centre in the trammel used to scribe an arc on the un-bored brass. This was then centre-popped, set up in the 4-jaw with a wiggler and DTI, and bored for the crank pin. Here is the trammel....


20221222_194530 by malcolm brown, on Flickr


Initially, the rods were binding quite badly, at least it felt so. Then followed a long spell of experimenting by dismantling each brass in turn and adding shims between the brass and the rod or taking off a little metal from the rod so that the brass sat deeper in the slot. By going back and forward, making a small adjustment on one rod, checking if it made a slight improvement, and then trying the other rod, I got there eventually. It needed a few thou off one of the rods so that the brass sat deeper (but that also meant making a new wedge as the original one had bottomed out) and a 3 thou shim in the other. But each attempt meant dismantling the wedges and adjusting screws and so it added up to an afternoon's work. But now the rear three wheel sets go around smoothly, with very little play at all. The rod bearings have been eased from their reamed condition but only by a few thou.


20221222_194426 by malcolm brown, on Flickr


The front rods, however, pose a much more difficult challenge - and all my own fault. When I first drew them out in CAD, I assumed the front and rear rods were mirror images of each other - but they are not as the shot below shows. This is because the wedges are always at the front of the bearing. Here is a front rod (top) and a rear rod for comparison.


20221222_194620 by malcolm brown, on Flickr


I redrew them once I had realised, but I neglected to note that the crankpin is not central within the oblong hole. As a result, my front rods are about 4 mm too short and the hole, when bored, will break out of the side of the brass. Oh dear....

The obvious, and probably the correct, thing to do is to redraw them and order new blanks from MEL. But it took a lot of work to get the blanks to the current position and so I have been thinking how to add 4 mm to the length in way which will be sound. I think I have a workable plan - and i may try it tomorrow and report the result. If it fails, it's back to the CAD drawing board....

It reminds me of a time in the 1970s at Tywyn when new rods were being made out of plate for either No.4 or No.6. They were all marked out - they may even have been cut - when it was found that the tape used for setting out was missing its first inch.... If they had been cut out, I know how the problem would have been solved - an extra inch would have been welded in. On No,7 today there is a visible weld in the eccentric rods where new, ball race, ends were welded on to replace the old grease bearings. But I suspect that my rods will be too small in section for welding, at least with my old fashioned stick welder.

More when I have a result!

Best wishes

Malcolm

[mbrown]

Sorted! (I hope...)

Here is how I solved the problem of short rods.

Taking my courage in both hands, I cut the rods through, chucked them carefully in the 4 jaw so that the rod section ran true, then drilled and tapped each half for a length of 5 BA screw. The two parts were then screwed together with a spacer of the correct thickness between them.


20221223_143611 by malcolm brown, on Flickr


20221223_143854 by malcolm brown, on Flickr


The reason the spacer is round is, firstly, so that it could be faced to the exact length (the missing few millimetres plus the thickness of the saw cut and the smidgen faced off each end) and so that, if it did move during the subsequent silver soldering, it wouldn't alter the section of the rod.

The 5BA screw had a flat filed down it in the hope that this would encourage the solder to flow along it. The joints were then silver soldered and, after carefully cleaning up with files and emery, looked like this.... Final finishing still to be done.


20221223_151752 by malcolm brown, on Flickr


I have set the light so that the solder joints are just visible, but it takes a keen eye to spot them and the front rods are largely concealed behind the crosshead etc. anyway. I am hopeful that this solution gives me a strong enough rod and will do the business.

Anyway, after trammelling the axle centres, transferring the dimension to the brasses, and boring them in the lathe, as with the trailing rods, all three sections went together and .... the wheels went around! There was a slightly tight spot which I eventually traced to one brass needing to sit a couple of thou deeper in the rod - and with that dealt with, the chassis pushes up and down with the wheels rotating smoothly - even without the weight of the boiler to give it extra adhesion.


20221223_163007 by malcolm brown, on Flickr


I took the crossheads and slide bars off to get at the front crankpin, and the next job will be to shorten the piston rod, fix the crosshead to it after "taking the bumps", and then put the connecting rods on. That may have to wait until after Christmas.

Merry Christmas everyone.

Malcolm

[springcrocus]

Dec 23, 2022 18:04:43 GMT mbrown said:

Sorted! (I hope...)

Here is how I solved the problem of short rods.

Taking my courage in both hands, I cut the rods through, chucked them carefully in the 4 jaw so that the rod section ran true, then drilled and tapped each half for a length of 5 BA screw. The two parts were then screwed together with a spacer of the correct thickness between them.


Malcolm

Interesting! The spacer had to be a multiple of the pitch (or half-pitch) of the 5BA thread or the two parts would have been mis-aligned when screwed together. I think I would have looked for a different solution but I'm glad it  worked for you.

Regards, Steve

[mbrown]

Thanks Steve,

Technically, the spacer needed to be a multiple of the pitch of the screw as neither half is symmetrical. But, in reality, it's surprising what a difference there is between "tightly screwed together" and "very tightly"... And there is a bit of leeway in the position of the bore in the brass, so the length is not critical to a few thou. In practice, both were in line when done up with only gentle pressure from a spanner - but that was probably a fluke.

Of course, the proof will be whether it stands up to the rigours of service - which I won't discover for a few years. It may not be a very good solution at all. I'd be interested in other possible approaches (apart from making new rods, which is always my fall-back position) if you had any ideas. I did experiment with welding some test piece of similar section, but couldn't get a good, let alone a neat, join.

Best wishes

Malcolm

[chris vine]

Hi Malcolm,

That is a most cunning repair. There's no real bending loads there, so I am sure it will be absolutely fine in service.

Chris.

[flyingfox]

Seasons Greetings Malcolm, I had a very similar problem when building my 5" GNR 2-8-0 (Nigel Gresley), when I made the front set of rods 1/16th too short. with a piece silver soldered in, just butt jointed, cleaned up, nobody has ever noticed, and that loco has done 2 IMLEC's, and hundred of hours passenger hauling. All that was 35 years ago.
I am sure your elegant repair will be fine.
Regards
Brian B

[mbrown]

Reverser Stand

After weeks of being, essentially, a fitter, getting the rods and bearings sorted, I decided a change of tack was needed and started fabricating something rather different - in this case, making a start on the reverser.

The reverser on 99 3462 is typical of Continental practice, having a long screw, operated by a single-armed handle, and bolted to the side of the firebox. I won't be reproducing the last factor, mounting mine on a bracket up alongside the firebox and fixed to the frame. When I was at Weisswatter in 2019, I took some photos but none of them capture the reverser as a whole, however these two shots give you the idea. Incidentally, the strange round thing in the foreground of the second shot is a preservation-era mug holder for the driver's coffee (I don't think they drink a lot of tea there....). I did take copious dimensions, so I should be able to get the reverser right...


DSC00423 by malcolm brown, on Flickr


DSC00422 by malcolm brown, on Flickr


I started with a piece of 12mm x 3mm x 3mm black steel angle, milled down to 2.5mm thickness and the legs adjusted to size. One leg was cut through and bent inwards as shown, blocks added for the pedestals that will carry the screw bearings (over long at this stage) and a piece jammed into a slot to make the angle bracket. Here it is prior to soldering.


20221224_151235 by malcolm brown, on Flickr


The bit of wire poking out from the back was laid along the join to get a decent fillet of solder - the saw cut wouldn't close up completely and was big enough to let the solder flow everywhere. The wire allows a fillet to form and is the cut away afterwards.

And here it is after soldering and cleaning up.


20221224_170613 by malcolm brown, on Flickr


The screw is 7/32" diameter, and will be a two-start left hand square thread. This is the same as I made for the Burma Mines loco, but unfortunately the tap I made broke on the last pass through the nut, so this time I have to start all over again. More once Christmas is over.

Best wishes

Malcolm

[mbrown]

Reverser Screw


Fitting, fabricating, and today machining.... The reverser screw is 7/32" dia (almost perfectly to scale for the 50 mm dia screw on the full size loco) two start and left handed. On the big engine, it is 11 turns from forward to backward gear, and with a 1/8" pitch thread, mine should be similar.

The tool for cutting the thread is ground from a broken 3/16" centre drill - the tip is exactly 1/32" wide and the tool is mounted in a holder which allows it to be adjusted to the pitch angle of the thread. One of the screws on the QC tool holder had to be replaced with a grub screw to clear the travelling steady.


20221226_190146 by malcolm brown, on Flickr


First, I made a blank for the tap which will (I hope) cut the thread in the nut. This was in silver steel and here it is with the first thread just starting to take shape. The feed is set at 1/8" pitch, Left handed.


20221226_164018 by malcolm brown, on Flickr


When the thread was at nominal depth, I did 6 or 7 more passes to take any spring out of the workpiece. Then, to put in the second thread, I advanced the top slide by exactly 1/16" - I used a DTI to get this exact. Then the threading was repeated with the second thread fitting exactly between the grooves of the first one. Having made the embryonic tap in silver steel, I did exactly the same in mild steel for the screw itself - and after cutting silver steel, a couple of thou at a time, it was a doddle. Here is is with the second thread about half way to completion.


20221226_175842 by malcolm brown, on Flickr


And here are the silver steel tap - yet to be fluted and hardened - and the reverser screw. The latter is deliberately over-long but will be made to place later.


20221226_190014 by malcolm brown, on Flickr


From past experience, making the nut is the hardest part of the job. But I picked up a tip from the thread by miken on his wonderful Webb Dreadnought Compound - which is why the tap hasn't been fluted yet....  I am not sure what has happened to miken and his compound - there haven't been any posts for some time and all his pictures are down. I hope all's well as the thread was inspirational.


Best wishes

Malcolm

[mbrown]

Reverser Nut


I can report that the method of making the 2-start nut used by miken on his Webb Compound works a treat.

The embryonic nut was made from two lumps of cast gunmetal (intended, I believe, to be Tich axle boxes) placed together with two locating pins and drilled through on the join a wee bit over the core diameter of the thread.


The two halves were then placed over the silver steel threaded rod and squeezed in the vice. I found that it helped to leave the metal to "settle" for a few minutes and then squeeze again, each squeeze closing the two halves a little closer together (or maybe the break gave my muscles a chance to recuperate...). This is what the nut looked like on opening the two haves up.


20221227_154803 by malcolm brown, on Flickr


The silver steel thread was then converted into a tap by giving it a taper lead and four flutes.


20221227_205228 by malcolm brown, on Flickr



The two halves of the nut were silver soldered together, aligned by the pegs and using as little solder as possible.

Miken said that he managed without hardening and tempering his tap, so I thought I would try the same. When I have made similar two-start threads before, the hardest bit has been getting the tap to start cutting. But with the "pressed" thread to guide it, it began to cut straight away and needed very little force. The unhardened silver steel did the job fine, although if I was doing more than a one-off I would harden it.

And here is the result - fitting very nicely onto the screw intended for the reverser. with no discernible back lash. The nut is rather like a small crosshead operating between two slidebars, so the grooves for the bars were milled in and the pintles for the reach rod turned on each side. The bosses at each end of the thread have been left over-long so that can adjust the travel of the reverser when the valve gear is all erected.


20221227_191605 by malcolm brown, on Flickr


All in all, a very satisfying couple of afternoon's work.

Best wishes

Malcolm

[ettingtonliam]

Thats a clever trick, squeezing the halves of the nut onto the unfluted tap blank. I must try to remember that for future.

Like you, I don't usually harden the tap, if its for a once only use, and I don't take the burrs off the flute edges either, that seems to give the right sort of clearance for the thread/nut assembly.

[mbrown]

Reverser continued...

More work on the reverser yesterday and today.

I didn't take many pictures as all the operations were pretty basic and straightforward. Maybe the most interesting was the locking wheel which has 16 notches, each 1/16" wide x 3/64" deep.

So, another small tool ground from an old centre drill to exactly 1/16" wide and mounted sideways. With a dividing attachment on the headstock, the 16 notches were planed into the blank. It took much less time than I expected about 40 mins.


20221229_122450 by malcolm brown, on Flickr


The other bits were time consuming but not special in any way. The guide bars, top and bottom, came out of some lengths of 5/16" x 5/32" BMS which I got from Whiston's many moons ago, It has nice sharp corners, unlike much steel strip bought today.

Anyway, it is nearly finished - just the brass scale along the top to do. As that will involve taking the whole thing to bits to mount it, I thought I would take some pictures of it disassembled to show the construction. It even has one refinement the original lacks, in that the locking trigger is spring loaded so that it doesn't drop into engagement at the wrong moment.


20221229_180200 by malcolm brown, on Flickr


More tomorrow, I hope.

Best wishes

Malcolm

[mbrown]

Reverser concluded


The brass cut-off scale on top of the reverser posed a few challenges. It is quite small, and in full size it has raised bars across the scale for each 10% cut off position, and for some reason, in four places, the bars only go half way across the scale and have grooves on the other side. After much reflection, I thought I could see a way to reproduce this...

It started as a length of 5/32" x 1/16" brass with a series of 1/32" holes drilled through the thick dimension at the position of each bar. As you can see, the drill wandered a little...


20221230_131705 by malcolm brown, on Flickr


The strip was then sweated to a more substantial piece of brass and carefully filed down until the holes started emerging on the top side. I was aiming to leave about 2/3 of the hole intact, but the wandering drill meant that this was hard to gauge. A 1/32" brass rivet was then inserted into each hole, with the rivets cropped to 5/64" length for the half-width bars. Some were a nice fit and stayed firm, but in some cases the rivet was loose and inclined to drop out. 1/32" rivets are easily lost once dropped! I should have taken photos of this stage really, as it is hard to describe verbally, but I was concentrating hard and forgot.

The rivets were then soft soldered into place using the smallest possible amount of solder. One or two leapt out of place as the flux boiled, so it was a bit of a caper getting them all in the their right places, but I got there eventually. One of the half-length rivets disappeared and I inadvertently replaced it with a full length one, so only three positions now have short bars.

At this point, I realised I was hoist with my own petard as I couldn't un-sweat the whole thing from its backing plate without the bars coming adrift. So I carefully cut around the outline, then filed most of the backing piece away until the overall thickness was about right. The original had the cut off at each bar stamped on - 80% through to 10% - I managed to get 80%, 70%, 60% and mid gear stamped on with 1 mm high number punches.

Here is the result - not as neat as I would have liked, but remember it is only a wee bit over 1/8" wide so the blemishes are less obvious in reality. It should mellow with age!


20221230_154341 by malcolm brown, on Flickr


To fix it in place, the whole reverser had to come to bits, so here is a chance to see the various components. The spring catch and detent for the locking handle are fitted in a hole drilled down into the front bearing support. The detent is 2 mm dia and the spring came out of a wrist watch strap pin - a good source of small but quite strong springs.


20221230_164701 by malcolm brown, on Flickr




20221230_171212 by malcolm brown, on Flickr


Now it really is finished. The final touch was a length of 3/64" brass wire threaded 12 BA and fixed to the nut as a pointer on the scale. I couldn't reproduce the original which is made from a piece of what appears to be bent tin!


So, another gadget to fiddle with while I get on with all the other bits and pieces. This may be the last post for a few weeks as the Christmas holiday is almost over.

Happy New Year to all.

Malcolm