At the risk of boring people with my new found skill I have drawn up a couple more items yesterday. First was a much simpler task than the chimneys that I have drawn so far, this time a dome for the D2.
Then at a friend’s suggestion I had a go at the GNR version of the Ramsbottom safety valves.
I had got this far when Chris looked over my shoulder and said “it looks good but it doesn’t look right” she was of course correct the springs should be on the lever that I hadn’t drawn yet not the valve stems… To be continued…
The D2 chimney must have been beginners luck. The next one took me two days of fighting to get it finished. Despite the frustrations I have learned much from the experience (I am a great believer that mistakes and things going wrong are far better teachers than when things go swimmingly).
This chimney is for non condensing C12’s and J52’s. According to the drawing, the condensing versions were fitted with shorter but otherwise similar profile chimneys. I feel that I have done a better job of this one and it’s a bit finer in shape/detail.
I am not sure whether it’s beginners luck but further sessions today have added a tube under the centre of the flare to help locate the chimney in the smokebox and the rivets around the rim. I still haven’t got it completely hollow but I will perhaps try to achieve that on the next one.
You may have seen elsewhere that coming up I have a test build for an LNER D2. The first build is to be a BR period build and I have a J6 chimney casting from Gladiator for it. However once the etches are proved I plan to build a second D2 for myself which I wish to finish as it was in it’s early life with the LNER in lined green.
This means that it will need the original chimney so I need to turn one/have one 3D printed or something. Those who are Gauge O Guild members my be aware that following on from the success of the virtual shows the Guild has been hosting some special interest session in various subjects one of them being 3D CAD/Printing. I missed the initial session a few weeks ago but caught up with it via the YouTube channel and then joined last nights session.
Prior to joining the Zoom session I downloaded and installed Fusion360 which is the software at the centre of the 3D CAD element of the sessions.
This morning I had a play and following a demo video done by a fellow GOG member last year I managed to draw a chimney. Having completed it I shared the image below with the gent who ad created the artwork for the D2 etches and he commented that the smokebox looked a bit narrow. Then it dawned on me that I had used the figure for the radius taken from the drawing and hadn’t doubled it to enter the diameter. Apparently you can enter a radius figure but I haven’t worked out how yet.
So this afternoon I attempted to redraw it using the correct smokebox size.
You will note in the image above that there are orange coloured squares. These are offset planes that I used to apply the dimensions from my chimney drawing. I managed to miss out one of the planes (for the bottom of the chimney rim) and try as I might I couldn’t manage to draw any lines between the planes like I had this morning. in frustration I deleted all but the base, saved it and went and had my dinner.
This evening I worked out how to import a drawing, resize it and then draw over it as I would in Inkscape or QCAD.
Below are a couple of views of the revised drawing.
I went through the process again this time drilling the offset at 2mm which proved to be perfect for this particular application.
I had been using a very thin cutting tool which someone had ground (not very well it turned out) which came in the box of bits with the lathe. After cutting the first one I thought that I would examine the tool to see if I could improve it or at least rub it on a stone to restore the cutting edge. When I looked closely at the cutting part I noticed that the bottom of the tool was wider than the top and although there was some rake away from the cutting edge the fact that it was getting thicker couldn’t be helping to make an efficient cut. This is a sketch of what the tool looked like originally albeit the bottom of the wedge is somewhat exaggerated. [img]https://live.staticflickr.com/65535/51259964196_7d3dd5c448_z.jpg[/img]
I have watched a few Youtube videos on sharpening lathe tools recently so I had a go at grinding the tool to take off some of the thickness towards the bottom making the two sides parallel. This improved the cut and I successfully cut the groove for the first sheave. Then I parted it off but I was a little too close leaving a very thin edge. During the parting off, the parting tool moved slightly in its holder which pushed over the thin rim of the sheave slightly closing the top of the groove. In the end it was usable but I decided to cut another pair to be on the safe side. It was while parting off the first one that I noted that my parting tool was in fact just the right thickness for cutting the groove without having to move the carriage as well as the cross slide to get the desired cut. Having discovered this the next one progressed much faster and modifying the fixture that holds the parting tool so that it grips the parting tool more securely by squeezing it in the vice made the third one even faster still. The parting tool is one like this albeit mine only has one tool. You will note that it’s a pressed steel fitting that grips the part with the aid of a cap screw. Mine didn’t hold the cutting tool very closely to the holder but it does now. https://images-na.ssl-images-amazon.com/images/I/41Uv-fAJmjL._AC_.jpg
So here we have the finished sheaves.
This is how they will fit on the axle once I work out their alignment with the crossheads further down the line.
It turns out that I wasn’t far out with my 16mm deep offset hole, I had a measure of the remaining stock while putting this post together, and there is just about enough material to cut a 4th sheave had I needed a full set for a conventional inside motion build.
Although these parts are allied to the Princess build, I thought that I would add the making of them and the reasoning behind it as a separate post just in case anyone has need to solve a similar problem in the future.
Readers of the David Andrews Princess thread will
have noted that I had to make the brake gear removable to ensure that I could
remove the wheels due to them being mounted on telescopic axles. This need
stems from a similar issue but I will start at the beginning.
Although the gent that I am building it for doesn’t
want full inside motion. One thing that is quite visible through holes in the
front frames, is movement of the crossheads. I was asked if I could add some
element of movement using the spare outside motion bits from the kit ( a set of
Premier rods etc. has been supplied for the build). Having started to think
about it long before getting to the actual start of the build I realised that
with the axles being hollow I couldn’t use traditional cranks to make the
crossheads move (or rather I wasn’t comfortable that I could make it work
without ruining axles wheels). So I thought that a pair of eccentrics would
impart movement while being able to be attached to the hollow axles without
having to cut them.
We agreed this as the way forward and I ultimately
bought castings for the slide bars/crossheads and eccentric straps from Laurie
Griffin. I was also going to buy some eccentric sheaves too until I recalled
Nick Dunhill finding the new cast versions very time consuming to prepare.
Further thought made me also realise that the LG cast ones wouldn’t really work
anyway. This is because in a ‘normal’ inside motion set up the eccentric sheaves
are trapped between the cranks so the eccentric straps cannot slip off the edge
of the sheaves. Of course, I planned to use them as a single eccentric so they
would need to be restrained at either side.
Instead of ordering a set of cast eccentrics along
with the other parts, I bought a length of 12mm round brass bar instead.
Initially I was going to offset in the lathe using
a four jaw chuck to offset the bar but having done a bit of research online,
most machinists were of the view that you could but if you had a mill it would
be far easier to drill it in the mill. Not being as proficient with my mill as
I hope to be in time I did use the lathe to put a small centre mark in the end
of the bar before transferring it to the vice in the mill.
Then using a centre drill inserted into my centre
mark to centre it quickly, it was easy to plot the offset (2.4mm, more on this
later) and then drill it out to 4.5mm. I then took it to final size with a
Transferring it back to the lathe I took a skim off
the outside and marked up for the first sheave. Some time later we had this.
I tried the
eccentric strap for size and found it was just a little too wide for the strap
to close completely around the sheave.
It was at this
point that I noticed that the depth of cut of the groove to accommodate the
strap was such that it was very close to breaking through into the offset hole.
It seems that in setting my offset hole at 2.4mm from the centre to gain the
maximum amount of movement was just too much.
You may be able
to see the mark where it’s just about to break through in the image below. This
was made worse by having to apply a second slightly larger reamer than 3/16
(4.74mm) to get the axle end into the offset hole
The plan is to
start again from the other end with a 2mm offset hole and see how I get on.
Yesterday saw more progress on the motion for the J6, with the valves almost complete.
I still have the arms to make that connect the valve rockers with the expansion link etc. But I am pleased that I have got this far as I had hit a bit of a mental brick wall with concern that attempts at soldering on the valve rocker supports would result in them dissolving into individual parts again.
As happens often when procrastinating, I worried for nothing.
In my varied kit collection I have a few items of NER rolling stock from Medley Models/NER Days and it recently came to my attention via a fellow modeller that among other things the buffer heads in some of the kits need a little attention. I had a vague recollection of Steve Hoyle mentioning something about his supplier having supplied them as they are and has subsequently passed away so no chance of doing anything about them. These are what came with some of the kits (appologies for the slightly out of focus photos). You will note the interesting collar that would prevent any kind of compression…
I bought a couple of B1 opens from Mossy and they have been sat on my desk with the buffers beckoning to me each time I sat at my laptop. So this afternoon I decided to turn the collar off. In the end I did about 30 and it was quite a good exercise in repeatability on the lathe using the graduations on the lead screw handwheels although the minor variations in sizes proved that they weren’t done with a CNC machine. I also took the opportunity to file off any centre pips and rub over the heads with emery while I had them in the chuck.
Further progress on the tender has seen the basics of the body
So far, the only issues have been some bowing of the half-etched
sheets which has taken a bit of work to get them soldered up straight. The
worst being the rear sheets with the steps and the coal door.
In the end I added a second sheet of 10thou nickel to back
off the coal door.
While I am distracted with outside jobs during the good
weather, I have been working on another of the key outstanding jobs that is
simple to pick up and put down. The back head/plate, is as I mentioned earlier
in the build, a GNR Boiler Back Plate set from LG Miniatures. It wasn’t quite
deep enough so I added a strip of thick brass along the bottom. Also missing
from the set as delivered, were the injectors. Laurie includes a layout drawing
in the set and it showed the missing injectors. An enquiry to Laurie had an apology
and a pair of injectors in the post.
I am not sure if they were from the GNR set or another more
generic pair but a little bit of scratch building had them looking the part. I
had to fabricate one of the levers for the right hand injector from a .9mm rod
with one end squashed and drilled out for the pin and then tapered with a file
in the mini drill (too small to old securely in the lathe).
In the end I only used one of the hand wheels from the set
because they came with cast stems on them and I wanted to fit them to the stem
already present on the castings so I used some cast hand wheels from the spares
box which had holes in the centres. Had I not had them to hand I would have cut
the stems of the castings and drilled them for the ones with the cast stems but
it would have been a bit tedious.
The GA showed some kind of inline valve down the right hand
side of the cab at the side of the back plate so I knocked one up from a couple
of bits of tube and a cast handwheel from the set.
My apologies for the greenish tinge it’s reflections from
the green storage box that I propped it against for the photos.
With the brake hanger height sorted it was time to fit them.
Because the wheels are on telescopic axles, they need much more wiggle room to
be removable than the Slaters et al, types. It’s actually quite surprising how
little room you need to remove a Slaters wheel.
The lack of space around the brakes meant that for the
wheels to be removable the brakes need to be removable too. I did this by
adding a collar from microbore tube over the .9mm rods that the brakes hang from
on the frames. And at the moment the cross shaft at the front of the tender is
removable but I am sure that if this were fixed the brakes would pivot out of
the way to get the wheels out.
Just to prove that they are removable.
I also made the two quite hefty support rods for the water
Plus, a Blue Peter moment in that here’s one I did earlier.
I fitted the brake cylinder that I turned when I first got the Unimat 3.
A few general shots of the inner chassis, for no other reason than I got a bit carried away with the camera.