99 3462 Build diary

[mbrown]

Making the Chimney


Having made the smokebox , it seemed logical to make a chimney to go on top of it....

99 3462's chimney is to a design used quite often by Orenstein and Koppel and although it was a casting, I felt it should be easier to fabricate it. Here is the real one,. I took dimensions when measuring her up in Germany. BTW, I got the diameters by measuring the circumference and doing the maths!


99-3462-im-Bahnhof-Friedland (3) by malcolm brown, on Flickr


I started with a length of thick walled steel tube. I had enough to do the chimney twice if I made a mistake the first time, but if I had cut it in two, there wouldn't have been enough for a chucking piece, so I started work on the whole length using the fixed steady, and only parted it into two when I was sure I had got things correct. The first operation was to turn the lower, parallel, section, part of which goes into the smokebox to mate with the petticoat pipe. The parallel section could then be held in the chuck while turning the taper.


IMG_20210404_180147 by malcolm brown, on Flickr


I incorporated the collar close to the chimney base, and reduced the very lowest section by a few thou so that the chimney base would later go on just the right distance. This steel tube is tough stuff and it isn't easy to get a decent finish. I found that very fine cuts with a fast speed got the best result, but in the picture, I hadn't got that far.

Next job was to turn the outside taper on the barrel - it is not very tapered at all and I found that 1.5 degrees on the top slide gave me the correct dimensions.


IMG_20210404_184825 by malcolm brown, on Flickr


The light is casting a shadow from the collar giving a rather odd profile!

Then, as I was happy so far, I parted it off to length and reversed it in the chuck to bore out the inside to a similar taper. Again, the steady came in very useful to keep everything true.



IMG_20210405_134720 by malcolm brown, on Flickr


Next, I bored the smokebox to suit the lower end of the embryonic chimney. This was so that I could try it in place and ensure the base was level. With the 1/2" boring bar running through the initial 1/2" hole in the smokebox top, and guided by a bush in the hole for the exhaust, the bore had to be truly vertical and aligned with the blastpipe. I double checked with callipers as in the pervious post.


IMG_20210405_163308 by malcolm brown, on Flickr


I forgot to take pictures of the base as it came together.... It started as a square of 3 mm steel plate, bent to suit the smokebox curvature. I did this on a longer piece of plate so that the bit with the most accurate bend could be selected. The actual bending was done in the vice between a length of 4.5" steel pipe (same as for the smokebox itself) and a section of 3" steel channel. With a bit of manipulation, I got a suitable piece which fitted the smokebox snugly. This was then centred and set up in the 4-jaw chuck to be bored to suit the chimney. With frequent checking, it slid on nicely up to the almost invisible stop I had machined into the bottom section of the chimney. Double checking, by trying it on the smokebox, showed a really good match.

The base was then silver soldered to the chimney. The prototype has hardly any fillet between the base and the barrel - although it is a casting, it looks almost like a weld. But it is still more of a fillet than I thought I would get with silver solder. So I took a piece of iron wire, about 3/64" diameter, and bent it around the join to fit snugly. This allowed the solder to form a kind of double fillet and, when filed down, gave just the effect I wanted.

I took the corners off the square base with a hacksaw (gripping it in the vice by the corners to avoid any possible distortion of the radius) then silver soldered it in place. Finally it was mounted in the lathe and the edge was turned down to the correct dimension.


IMG_20210405_172542 by malcolm brown, on Flickr


The steel tube was just too small to get the half-round rim out of the stock material, so this was turned and bored on an odd end of larger steel bar, and a rebate turned on the lip of the chimney. The ring was bored so as to just "not" go onto the rebate, then heated to blue at which point it dropped neatly into place and is firmly shrunk on. It was cleaned up to size in the lathe once in place.


After cleaning up carefully, here is the whole chimney in situ on the smokebox. The perspective makes it look taller and more tapered than it actually is - I must experiment with getting a photo from the same angle as one of the real loco!  Now I just need to mark out and drill for four small holding-down bolts and it is done.


IMG_20210405_181738 by malcolm brown, on Flickr


Back to work tomorrow, but more soon, I hope.

Malcolm

[mbrown]

Somebox Door - Part 1


Made a start today on the various bits of "furniture" that adorn the smokebox door.

99 3462 has a standard DR-style smokebox door and, like many locos, its smokebox doors have a bit of a history. The original O&K door had a central dart and wheel fixing although, unlike UK practice, the handle to align the dart was on the outside and the wheel to tighten it was against the door. But at some time shortly post-War, she acquired a door with the standard DR fittings - five wedges and levers (or dogs) to hold the door tight, a small handle near the top and another, longer handle at the 7 - 8 o'clock position. In the 1950s, the handles were rivetted on but about 1960, a new welded door was fitted. The one now carried in preservation is almost identical but the wedges are a little further from the periphery of the door so it was probably replaced again in the 1980s.

Around 1966, she was given a horseshoe on the door as an ornament. In DR days, it was fitted with the ends pointing down. In preservation - I think whilst at Boston Lodge in the 1970s - the horseshoe was refitted the other way up which is how it is today. I don't know if this was because the tradition that the luck runs out of an upside down horseshoe is a peculiarly British thing... perhaps one of our German members can say why it didn't seem to bother the DR crews. Maybe, as this horseshow has the lower ends joined up, the luck can't run out of it anyway!

Here's the door as it was in service on the WEM a few years ago.


2257572-1463301416 by malcolm brown, on Flickr



The wedges are small - scaling at 7/16" long and 11/64" wide with the thick end about 1/16" thicker than the thin end. They all need to be the same if the dogs are to line up reasonably. I went about making them like this....

First, I milled up a piece of BMS to 7/16" x 11/64", chucked it end-on in the lathe and drilled a 3/64" hole through it (actually, going in from both ends as deep as I could - the holes didn't have to meet. Next step was to set the milling vice over to the correct angle (achieved by trial and error) and mill the angle on each end.




IMG_20210410_160305 by malcolm brown, on Flickr


Then over to the vertical slide on the lathe and each end was cut off with a slitting saw.


IMG_20210410_162750 by malcolm brown, on Flickr


Repeat three times and I had six wedges, all the same size, each with a small hole through the centre. With the positions marked on the door, it was easy to drill the centre points and fix the wedges in place. I had intended to use 3/64" rivets but I had run out so they are fixed with 12 BA screws from the inside. The wedges don't all face the same way - they are arranged so that gravity and vibration tend to tighten the dogs against them rather than loosen them. There are five wedges as there is no fixing adjacent to the hinge. I made six because I knew I was sure to drop and lose one - so, because I made an extra one, naturally I didn't drop anything. Such is life.

The handles were bent up from 2 mm BMS rod and pushed into drilled holes.


IMG_20210410_175938 by malcolm brown, on Flickr


IMG_20210410_175920 by malcolm brown, on Flickr


The light is giving a strange effect to the domed centre, but in fact it is a smooth and continuous radius.

Hinges next, and then it will all be silver soldered up.


Best wishes

Malcolm

[lennart]

Very neat work as always.

Here in Germany some people think that a horseshoe needs to be fitted with the ends facing up (A) and some say that they should face down (B).

(A):

As you have written, with the ends facing down the luck would fall out.

(B):

The ends facing upwards resemble the devil's horns. The ends need to face down to enable the luck to fall into your hands when you stand under the horseshoe. As they are usually placed above doorways, this could actually make sense. Aside from that, the down facing horseshoe may resemble a protective cover that is put over your house.

I myself don't believe in horseshoes bringing luck and probably the DR crews back then didn't bother either.

I'm looking forward to read how you made the little locking levers. I consider these parts to be one of the most fiddly parts imaginable on a locomotive.

[mbrown]

Thanks for that information Lennart. I don't believe in horseshoe luck either, but someone on the MPSB in the mid-60s obviously thought the horseshoe would be a nice mascot for the loco. A bit like the stars and other polished decorations that drivers on the Caledonian and some other pre-grouping railways here put on their smokeboxes, perhaps.

Local variations in folklore are fascinating. I had not heard the option B version before, but when I read out your post to my wife (who knows more about folklore than I do) she said that it is uncommon but not unknown in Britain.

The little handles on the dogs may indeed be tricky to get just right. But I took photos and measurements of the prototype and I am having the basic lever shape laser cut as part of a batch of parts that are currently with Ed and Holly at MEL. I will then have to fit them to their bosses and find a way to make the studs robust enough but not too obtrusive.... I'll share the result in due course.

Best wishes

Malcolm

[mbrown]

Smokebox Door - Cont:


A long session in the workshop today got the smokebox door finished - just the locking dogs to do, and they will have to wait for my order to arrive from MEL.

The hinges took a long time to get right. They are just under 3/16" wide and cut from 18g steel. Bending the ends around a 2 mm rod was surprisingly easy - a combination of pliers and the vice....


IMG_20210411_154948 by malcolm brown, on Flickr


Fitting them to the smokebox door, the correct distance apart and parallel, took forever... Got there eventually after much trial and error. Then the whole lot could be silver soldered together - wedges, hinges and handles. Heating it all up evenly was difficult as the handles overheated before the door itself was up to melting temperature. The little top handle came out OK, but the solder for the longer handle didn't "take" as the flux had burned off, so after cleaning it up I loctited a new one in place.

Not very visible in the shots below is a small bracket attached to the lower hinge. This will line up with a similar bracket to be added to the lower hinge block when the door is open and a pin drops through a hole to stop the door swinging shut. It may be a bit flimsy in practice, but no harm putting it in.

The hinge blocks on the door ring come out as 7/32" cubes - there is not much space so positioning them had to be just so.

Finally, I wanted a base for the numberplate. The prototype has it fixed onto two small brackets welded to the door, but the plate itself is quite flimsy and the etched plates I got from Beckert Modelbau in Germany are spot on for size and detail but only 0.5 mm nickel silver. So the base plate was made in steel with the ends thinned down a bit, and it locates in a shallow slot milled in the face of the door. It attaches with a 6 BA screw from the inside so that it can be removed for fitting the actual number plate.

I was too busy trying to finish this all off to remember to take photos as I was doing the job, but here are a couple of shots of the finished door in place on the smokebox. She's gradually getting her "face"....


IMG_20210411_194238 by malcolm brown, on Flickr


IMG_20210411_194249 by malcolm brown, on Flickr


That's all for a while now - as lock down eases, I am getting back to something approaching normal life and model engineering will have to take its place alongside a number of other interests and activities!

Best wishes

Malcolm

[mbrown]

First steps on the boiler

Now that lock down is easing and life is getting back to something a little more normal, workshop time is getting encroached upon by other aspects of life. Last weekend, I was able to get to Wales for the first time since last summer and delivered some air pump cylinders and refurbished valve gear parts from a friend's workshop here back to Pendre works on the TR. In the course of this I managed to gash a knuckle on a protruding grease nipple as I pushed the barrow past the big lathe and so I have been avoiding dirty work in the workshop while that heals. Nevertheless, 99 3462 continues to progress slowly and I have spent some time drawing the boiler details ready to discuss with a boiler inspector.

It is quite a long boiler with a broad but shallow firebox. I wanted to avoid the problem I had with LYN's boiler which has similar proportions, where I didn't get enough tubes in and she goes completely off the boil as soon as the bottom two tubes clog up. On 99 3462, the barrel works out at 4" diameter and tubes at 10.5" long. The challenge, therefore is to get in enough tubes of a decent diameter relative to the grate area.

I followed the formula in Martin Evans's book on Model Locomotive Boilers to get the tube diameter in relation to length, where the length divided by the square of the internal tube diameter should be between 50 and 70. That suggests the tube diameter should be between 7/16" and 1/2" and I have gone for 7/16" although it is at the constrictive end of the acceptable range. I used the formula in K N Harris's book, Model Boilers and Boilermaking, to calculate the total free area through the tubes in relation to the grate area, aiming for something in the range Harris recommends of between 1:6 and 1:7.

Anyway, here is the boiler drawing in full. I used old fashioned pencil and T-square for this rather than CAD - schoolboy Technical Drawing skills can be retrieved more easily than new computer skills can be gained! (Sorry, it's not easy to get the light right across the whole board).


IMG_20210424_132424 by malcolm brown, on Flickr


And here are two possible tube arrangements - one using two 3/4" flues each with one 1/4" spearpoint superheater element, and one with a single 1" flue carrying both superheater elements.


IMG_20210424_131533 by malcolm brown, on Flickr


The latter gives me one more small tube and a somewhat better grate/tube ratio. Taking account of the cross sectional area of the flue(s) minus the superheater elements, the single flue + 15 small tubes arrangement gives me a free gas:grate ratio of 6.26. The arrangement with two smaller flues and 14 small tubes give a ration of 6.5. Given that the tubes are a bit smaller than the ideal diameter, my instinct is to go for the single flue arrangement.

The only other interesting feature of the boiler is the dome where I need to have two steam take-off points at the sides. Using a normal dome bush, these would be too high, so I have cribbed Ken Swann's arrangement from Jessie and Bridget and propose a fabricated dome base with a flange fairly high up. This allows the take-off bushes to be in the correct place and has the added advantage of being able to secure the inner dome to the flange by bolts and nuts rather than tapped holes in a gunmetal bush which I always worry about, having stripped a thread on another boiler.


IMG_20210424_131542 by malcolm brown, on Flickr


Otherwise the boiler is conventional. I have gone for rod stays for the firebox crown which I have never tried before but many designs, such as Doug Hewson's Y4 use them and I have based the size and spacing on that design which is a similar size but with a Belpaire boiler. This will be my fourth boiler, and compared to the Burma Mines loco, with Belpaire firebox, combustion chamber and sloping backplate and throatplate, it should be straightforward... Famous last words, perhaps?

When I have discussed the design with a boiler inspector, I will ink over the pencil lines for posterity. Meanwhile, any comments from forum members very welcome.

Best wishes

Malcolm

[mbrown]

Lucky Horseshoe


A bit of whimsey today. I mentioned the horseshoe on 99 3462's smokebox door a few posts back. I thought I would have a go at a small one...

It measures just over 1/2" high on the model. Here is a shot of the real one, mounted the opposite way up to how it was in DR service, and photographed on the loco's 80th birthday in 2014.


10256294_556235617814807_317386551027844937_n (1) by malcolm brown, on Flickr


I marked it out by eye on a piece of 1/16" thick soft aluminium, filed out the hole in the middle first, put in the nail holes (no.60) and then created the recessed areas with a couple of very small punches filed up from 1/8" dia silver steel. I left the outer profile to last so that I had plenty to hold while shaping it. It is fixed to the smokebox door with two 12 BA screws from the inside.


IMG_20210425_133455 by malcolm brown, on Flickr


I have put it the other way up to match the era I am modelling, but it can go either way.


I have also made the pin catch which prevents the smokebox door swinging wide and fouling the adjacent line. Here it is in full size:


DSC00452 by malcolm brown, on Flickr




And here is my version:


IMG_20210424_172825 by malcolm brown, on Flickr


The pin is a 1/16" rivet. In practice, I shall probably omit the pin as it is a nuisance and very fiddly. The average steaming bays are far enough apart to allow the smokebox door to swing as wide as one wishes!


I have been going back to my boiler drawing and am havering over the two different tube arrangements. Any thoughts from the forum?

Best wishes

Malcolm

[lennart]

Very nice work as always.

The horse shoe must have been very fiddly to make. Nevertheless it perfectly resembles the full size one.

I am not qualified to contribute anything to your boiler design re the tube layout. I will probably ask the same and even more questions, when I will make the boiler for my Chub.

The only thing I can say is that the modified dome bush looks like a very good and much safer alternative to the conventional one with tapped holes.

[coniston]

HI Malcolm, I guess the benefit of the two super heater flues is the super heater elements can be arranged side by side so both feed and return get the full heat from the fire where as the single flue with twin elements must have the feed or return above the other. Whether this would show any real difference is debateable. The additional fire tube would probably have more benefit. As a comparison the Simplex boiler has 1 x 1 1/8" super heater flue and 13 x 7/16" fire tubes in a 4 3/4" OD barrel. Martin Evans shows a single super heater element of 7/16" OD S/Steel. I think your idea of twin super heaters in the single flue would be preferable from a thermal point of view but the single bigger super heater will probably allow easier cleaning of the flue tube.

Sorry this is not a direct answer but maybe will promote some other thoughts?

Chris D

[mbrown]

Many thanks Chris.

I am torn between getting the maximum free gas area and the risk of cramming too many tubes in. The other possible drawback of the single central flue is that radiant elements could come quite close to getting in the way of the firehole so may have to be shorter.

I would be interested if anyone has experience of:

A. Four 1/4" superheaters (i.e. two return spearheads) in a 1" flue, and

B. What the effect is of having higher free gas area but with smaller diameter tubes versus better tube area/length ratio and less free gas area.

In short, how critical are the parameters I got from Martin Evans and K N Harris's books?

Best wishes

Malcolm

[mbrown]

Smokebox Dogs


A package of laser cut parts arrived from Ed at MEL the other day, including the basic levers for the smokebox dogs. These needed tapering down toward the ends and silver soldering to a boss.

Next, bosses to take the studs were silver soldered to the smokebox front ring. I needed them to be solid as the wedging motion will tend to bend the studs and so I wanted them supported very close to the point of leverage.

Here is the front ring with the bosses in place, three studs done and two fitted with their dogs. Getting the studs just the right length took a fair bit of trial and error.


IMG_20210502_174610 by malcolm brown, on Flickr


And finally, two little studs are fitted at the top to prevent the top dogs (or upper dogs if you prefer!) dropping down and preventing the smokebox door from shutting.


IMG_20210502_181041 by malcolm brown, on Flickr


So that's the smokebox and door more or less done. On the prototype, the nuts holding the dogs are castellated and split-pinned so that they don't gradually slacken off. I have been following other threads on castellated nuts, but doing these for 7 BA studs, and with 8 BA hex nuts to be true to size, might be a bit challenging. I will have a go, but have left the studs long enough to take thin lock nuts if that works better.

Other laser cut parts included the top plate-work that goes over the top of the frames. Naturally, I couldn't resist trying it in place. I realise now that it will either have to be easily removable or I shall have to complete everything between the frames before fitting it. I also got the plates for the cab cut (sides, front and rear)  - I can't do a trial erection of the cab yet, and it will involve some "interesting" bending.


IMG_20210501_163444 by malcolm brown, on Flickr

Best wishes

Malcolm

[ejparrott]

Aaah so that's where they go!

[mbrown]

Castellated nuts and Generator Platform


The little castellated nuts for the smokebox dogs turned out to be straightforward. The 8 BA Hex rod was gripped by each pair of flats in turn in the machine vice and small slots cut with a 0.020" slitting saw. The bar was then transferred to the lathe, turned, tapped 7 BA, and parted off. A bit fiddly, but all five were done in an hour.


IMG_20210503_142545 by malcolm brown, on Flickr


I don't think they will need split pins. A very gentle squeeze at the end with a pair of pliers to close the end up just a few thou, and they grip the stud rather like an Aerotite or Nylok nut.

Today's other job was the platform on the side of the smokebox upon which the turbo generator will sit. It is bent up from 1.2 mm sheet. I spent a long time making one to the dimensions I took from the prototype in 2019, only to find when checking the position from photos that in DR days the bracket was a different and simpler pattern. It seems that when she had a new smokebox, probably in the late 1990s, the saddle and most of the fittings were changed at the same time. The "modern" one is lying beside the frame in the photo.


IMG_20210503_172757 by malcolm brown, on Flickr


I have also fitted the sides to the smokebox saddle. Again, these are as in DR days and until the new smokebox was fitted. The front and rear plates are, in full size, made from thin sheets and attached with a few screws - the side plates take the load. Mine will be similar - eventually!

So endeth another Bank Holiday weekend, mainly in the workshop.

Malcolm

[mbrown]

Starting work on the springs


I decided that, having diverted my attention onto the smokebox for the last few weeks, I really couldn't put off doing the leaf springs any longer...

Thanks to Mike in NZ (44767), I got the spring leaves for both the loco and tender laser cut in spring steel from my CAD drawings. They weren't cheap, but they allowed me to cut out the centres of the leaves to fine tolerances and thus to use scale thickness leaves. The leaves on the prototype are 1 cm thick which scales at 18 swg.

Mike made a very nifty fixture for putting the curve into the leaves for his BR Class 3 tank. They have to be bent around a radiused former or the pieces taken out of the middle of the leaves to deliberately weaken the leaf will make it bend unevenly. I made a rather more rough and ready version out of the offcut I parted from the original 4.75" dia smokebox tube.

I willathow some pictures tomorrow as I forgot to take the camera into the workshop. Basically, a clip holds the leaf by its end, resting against the edge of the tube and a handle pivoted at the centre, with a roller bearing to bear against the leaf, presses it against the former, bending it tight against it. I had worked out by rule of thumb that the diameter was about right so that, when the leaf sprang back, it would assume the correct radius.

Unfortunately "sprang back" was just what it did.... On the first one, I took the handle a wee bit too far, disengaging the roller from the end of the leaf, which then sprang out of the clip and riccoched around the workshop. I heard it bounce loudly off the lathe cabinet and then it disappeared. Several hours of searching have so far failed to uncover it....

Fortunately, it was a top leaf and not one of those with the carefully calculated gaps cut in the middle. The solid top leaf should be fairly easy to re-make and I do have enough spare material. But it is darned annoying. At least, once I had turned the bending tool to face a wall, just in case, all the other leaves for the tender springs bent up easily and accurately. So I know it works - and I know what to do to stop further disasters... I hope.

Tomorrow I have to beg borrow or steal a large potato to prevent the top leaves losing their temper while I silver solder the raised ends which bear on the spring hanger pins. And I will try to remember the camera.

Malcolm

[mbrown]

Springs continued....


Here is a picture of the leaf bending gadget I described yesterday.


IMG_20210509_134537 by malcolm brown, on Flickr


The ring from the smokebox tube is held with a disc cut from MDF and secured to an old breadboard. The lever has an adjustable pivot so that I can pull the roller bearing, just visible at the bottom, hard against the embryo leaf, and one end of the leaf is clamped by the clip. It was failure to clamp this tightly enough that led to the loss of one of the leaves, but I made another, cut from the scrap on the laser-cut sheets and ground to size. It is fairly rough and ready, and probably won't last very long, but it has done the four sets of tender springs and is good enough to manage the eight for the loco.

The raised ribs on the top leaf were silver soldered on, with the leaf embedded in a large potato, and are made of 3 mm split pin wire. They were held on by a 10 BA screw while being soldered.

The spring buckles were water jet cut - and came out more rough and ragged than previous parts I have had done by this method. They needed a lot of fettling to get the sides smooth and the opening to size to hold the leaves tightly. The leaves are held together by a 1/16" rivet through them and the buckle, the rivet being held up at the base by a 6 BA grub screw which fits into the small pocket on the top of the axlebox. The spring pins, rocking washers, and special nuts (3 mm x 0.035 thread) were made some time ago.



IMG_20210509_181926 by malcolm brown, on Flickr


So here is the first spring in place. Despite bending the leaves around a 4.5" dia former, the camber is very shallow, but that is as on the real thing. I really should have put the raised portions a little further out as the spring pins are slightly splayed. Nevertheless, it is not so noticeable from a distance and the main thing is that the scale thickness leaves, where most of the centre has been cut out of the intermediate leaves, gives a spring that seems just right - firm but definitely "springy".

Here are the leaves prior to bending, and a buckle after filing up to size but before drilling and turning the base.


IMG_20210509_191504 by malcolm brown, on Flickr

That is all for a while now - for the next two weekend I shall be playing with big(ger) trains on the Talyllyn!

Best wishes

Malcolm

[mbrown]

Pressing on with the springs


I have had a few weeks off from the workshop, enjoying some time driving on the Talyllyn and just lazing around in the sunshine while we have it.... But I have managed the odd hour here and there and have completed the four leaf springs for the tender.

I wasn't happy with the first one I made - the camber was insufficient and the "lumps" on the top leaf which bear on the spring pins were too far apart. That meant I had to re-make the bending tool to bend the leave to a tighter radius - I hadn't realised how much spring-back there would be in 18g spring steel. Luckily, there was just enough spare spring steel on the panels to make a replacement top leaf.

I used a steel disc about 4" dia which was another relic from some scrap bin and needed turning all over to remove bits of weld and rust. This one gave me just about enough camber on the springs.


IMG_20210601_175815 by malcolm brown, on Flickr


The bolt to tighten the roller bearing against the leaf turned out to be essential to ensure that the leaf was formed uniformly against the steel disc and didn't bend irregularly where the section of the leaf changed.

The leaves are held in their buckle by a 1/16" rivet locked in place by a 6 BA grub screw. I also finished the spring pins and nuts but ran out of time to assemble everything.


IMG_20210601_180130 by malcolm brown, on Flickr


The trick of sticking the top leaf into a large potato whilst brazing on the ends worked well - although I can't get the smell of burning spud out of my nostrils...


More next weekend, all being well.

Malcolm

[twombo]

Gadzooks! Malcolm! Those are real “treasures! Those “lumps” are the crowning touch! Wee, Bits, but they really. “Make” the part! Thank goodness for Laser cut! imagine the task done according to the “ old way!

wee Bits but essential! Narrow gauge prototype in 17/32” scale is quite a large and powerful machine, I reckon! Lovely! This is exciting! About how long are these springs. 2” might be just right for a standard gauge 4-6-0? I wonder!

There is an article in a back number, of The Steam Chest that I need to send a note to Cedric, regarding! I owe him a note, Besides!

Now, back to the “Shed”!

Mick

[mbrown]

Thanks! They are just over 2" long and the leaves are 8 mm wide by 1.2 mm thick.

Now I have another 8 to make for the loco. Last weekend I chickened out and made a start on the equaliser beams instead. But we'll get there eventually....

Malcolm

[mbrown]

Equalisers and tender springing


The equalisers between the first and second and the third and fourth axles on the loco look easy enough but presented a few challenges. You can make them out in the photo below, appearing just under the rear coupling rod end:


577728_651517734953261_3154313139901192022_n (1) by malcolm brown, on Flickr


The vertical spring pins are held between equalising beams behind and in front of the bracket on the frame. The pivot pin appears to be fixed, with the outer beam held in place by a split pin. But how to release both the beams is the problem, as the bolts holding the bracket are hidden behind the frame. I suspect they are accessible in full size, but not in 1:9 scale... Similarly, I couldn't put the pin in from the front and nut it behind the frame as there is a stretcher right in line with the pin, both in full size and on the model.

Anyway, the beams were small laser-cut pieces with bosses silver soldered to the middle hole and 1/8" rivets, with their heads turned to look like the prototype, silver soldered to the outer ends of one of each pair. The photo below shows the components for one pair of beams, the assembled parts for another pair and a pair assembled.


IMG_20210613_144418 by malcolm brown, on Flickr



To secure the pivot pin, I drilled and tapped through the bracket into the frame and the stay behind it which was plenty thick enough to take a thread. The pin is shouldered down and screwed 6 BA so that it tightens up to the shoulder, and cross drilled at the outer end for a 3/64" roll pin which simulates the split pin. The pin was screwed home with a little home-made key, cross-slotted at the end to mate with the roll pin, as shown. A dab of Loctite on final assembly should ensure it is secure - it doesn't get much turning moment to loosen. I would have preferred a more positive fixing, but this was the only solution I could think of and it should be OK.



IMG_20210613_161615 by malcolm brown, on Flickr



And here is one side done, although the lighting isn't brilliant and the frame is upside down. I just need to make 16 spring pins and to assemble the eight springs, and we'll be there. The roll pins will be shortened in due course.


IMG_20210613_162201 by malcolm brown, on Flickr


In other news, as they say, the tender springs are all now assembled and look pretty good. I just need to make lock nuts to go on the spring pins.


IMG_20210613_171954 by malcolm brown, on Flickr


Now that a few more opportunities for normal life are opening up, workshop time is a bit more limited than over the last year or so. And with the present good weather, the temptation to lounge around and not get going on various projects, is almost irresistible! But no point busting a gut for a hobby!

Good wishes to all

Malcolm

[mbrown]

Petticoat Pipe


After a break from the workshop over the last couple of weeks, I wanted to get on with something but still couldn't face the repetitive work on the springing - so I reverted to the smokebox to complete the petticoat pipe.

The chimney has a short parallel section which protrudes into the smokebox. I have had trouble in the past with trying to remove superheater elements when the petticoat got in the way of the header bolts, so I wanted to make this petticoat removable.

It started life as a length of 2" aluminium, bored to suit the chimney extension and turned on the outside with a ring around the diameter. This ring was then milled away on the rotary table to leave just a small section sticking out. This was to form the clamping lug.


IMG_20210626_171023 by malcolm brown, on Flickr


Next, the flare on the outside was completed in the lathe and then it was reversed in the chuck and the bell-mouth machined, first with a boring tool and then finished with my trusty hand scraper, visible in the photo.



IMG_20210626_173930 by malcolm brown, on Flickr


The lug remaining after the ring had been milled away was then drilled and tapped 2BA and a saw cut put in to allow for the clamping action. I was going to use a slitting saw, but it was a puzzle to work out how to hold the petticoat to do this, so I ended up using a hacksaw which was perfectly satisfactory and much quicker. Here are shots of it from the top and bottom...


IMG_20210626_181104 by malcolm brown, on Flickr


IMG_20210626_181116 by malcolm brown, on Flickr


Finally, here it is in place, clamped to the chimney extension. I can now go ahead to make the blast pipe and nozzle which screw into their socket between the steam pipes, giving both precise alignment and some height adjustment by screwing it in and out.


IMG_20210626_182530 by malcolm brown, on Flickr


Earlier on, when checking the fit of the petticoat on the chimney extension, I made the mistake of trying it for size while the aluminium was still hot from machining - it slid into place beautifully and then cooled and stuck! I did manage to get it off without damage, but it was a salutary lesson in patience!

Best wishes all,

Malcolm