D869

The splashers are on...

After a bit of pondering and trying to make them as a several sided box I ended up making them with a 10 thou outer layer with the rest of the thickness of the sandboxes done in solid brass...

...done on the MF70...

There was a bit of a gap between splasher and footplate because the (deleted) N Brass splashers were slightly further out than my versions. I filled the gap with a bit of 5 amp fuse wire and solder. This left a bit of a messy solder fillet...

I really needed to get to the point where I had finished applying lots of heat to the splasher area before I could clean up the fillet which meant making and fitting some twiddly bits to go on top. These were done with a hand graver on the watchmakers lathe. They looked almost non existent when I was making them but they look quite big on the loco...

The curved tops are strips of 5 thou which I have not managed to photograph.

Next up is fitting the rear panels. These were made a while back but left off to allow better visibility around the motor and fixing screws. The bunker rear panel is 5 thou brass and so far the only main panel cut out by hand.

Keep those springs - someone will lose theirs and be grateful for them.

I did once ask Farish for a replacement for one that shot across the room never to be seen again. A good while later a letter arrived with one spring taped to it.

Glue-wise some of my windows seem to have a hard time staying put... even though I haven't tried to take them out.

Regards, Andy

Proper job! I'll definitely be in the market for some NBL grilles if you can spare any Pix.

I reckon on chopping off all of those rivets around the roof panel edges on mine though. I think the Farish mould makers got a bit carried away there.

Regards, Andy

2 hours ago, pete_mcfarlane said:

That looks quite an interesting way of building a chassis, and not one I'm really familiar with as a 4mm scale modeller. Is the rear axle fixed (by the shaped block to the left of the driving wheels)?

Hi Pete,

Dave Holland described his method of chassis construction some time back. It was published as an article in MRJ No 34 in 1989 and subsequently by the 2mm Association as a small booklet called 'Build an 0-6-0 in Two Millimetre Scale'. The booklet is unfortunately out of print but a PDF scan is available to 2mm Association members via the web site.

As with most 2FS chassis, Dave's design uses split frame pickup. The important points for the O2 are the use of a now somewhat old-school construction with 20 thou phosphor bronze frames and solid spacers. Instead of having captive driving axles the axle holes are slotted and a separate 'keeper' with upwards facing slots is used to stop the wheels falling off.

The chassis is not compensated or sprung in a way that most 4mm folks would recognise but uses a more recent technique called 'Simpson springing' in which the axles normally bear on the tops of their holes in the frames but are allowed some downward movement. A piece of springy phosphor bronze wire is arranged to rub on top of them to ensure that electrical contact is not lost when they find a dip in the track. Calling it springing is a bit of a misnomer because it doesn't do any significant weight bearing.

Coincidentally if you read Mick Simpson's original 'springing' article in the 2mm magazine, he credits the inspiration to... Dave Holland. Dave's article/book describes the use of a similar technique but he only used it on the tender axles (maybe just the centre one).

The shaped block in the photo is a brass frame spacer. It has a PCB layer on one side for insulation and a Delrin bush to insulate the frame fixing screws. It doesn't play any role in the suspension arrangement.

Regards, Andy

14 hours ago, DavidLong said:

5A fuse wire. How much do you need?

 

https://www.ebay.co.uk/itm/5-amp-fuse-wire-36-SWG-Tinned-Copper-Wire-40-meters-FUSE-WIRE-5-AMP-0-2mm-/113965764804?hash=item1a88e390c4

 

My reel already has a place in my will . . . 

 

David

Ordered now

I shall miss needing to smooth out the kinks from where it wrapped around the card every 2 inches or so though. I guess I could put them in for old time's sake.

14 minutes ago, Chris Higgs said:

 

I once used fuse wire to form the rib around the roof of a GWR Star in 4mm scale. Its surprsingly easy to solder it straight.

 

Chris

Yes a very under rated modellng material. For some reason all of my cards are devoid of the 5A variety... odd, that.

I still managed to buy some last time I tried but the shop person had to dig around a bit to find it.

11 minutes ago, Ian Smith said:

I can't see the photos Andy.

Ian

I just added them again so hopefully all OK now

Is it just me? Can anyone else see the photos I posted yesterday or are they gone for everyone?

The posting last night went very slowly and two copies appeared when it eventually finished. I deleted the second one and all seemed OK, but today the pics have vanished for me.

2 hours ago, Izzy said:

There is a very good thread in the 7mm section about building an 02 from a Connoisseur kit. Page 15 deals with the cab roof and it seems some gained sliding hatches. I’d also use cut brass shim strip flooded with solder then scraped away to finish to suit. At the edges this may need to be edge on to appear correct looking at photos.

 

Izzy

Thanks. I think that Calbourne on the IoW has the hatch but as far as I can tell 30225 did not... although shots of the roof without steam obscuring the view are not exactly commonplace.

The smokebox on the O2 is now together. This proved to be a tricky job with lots of starting over - 2 inner wrappers, 2 outer wrappers and 3 fronts. Getting it all lined up on the boiler and then cleaning up the join around the front was also very tricky but it's done now. The door was turned up on the lathe, finishing off with a hand graver.  At the moment it's not fixed into place.

Here is my dodge for holding the front still while getting the thing aligned and then soldering into place. This was front No 2, which wound up being removed because I'd put the rivets a tad too far out and they wound up right on the edge once I'd filed the edge flush.

To finish the topic started by my question from the previous episode, I added a couple of brackets from phosphor bronze inside the tanks. They are not very elegant but they are out of sight and it has been handy to be able to adjust them to get the boiler to sit upright. Here's a pic of the body upside down to show how the brackets support the rear of the boiler. I think I need to add a positive 'back stop' to prevent the boiler from being pushed too far back and possibly damaging the paintwork.

The front splashers are looking like being the next job.

Thoughts are also turning to the cab roof. This has a rib all around the edge plus another that goes across the centre from one side to the other. At the moment I havent figured out a good way to do do this, so suggestions would be welcome.

Nice job on the signal Tim. One of ours has been clobbered a couple of times so far and the etched ladder is usually the thing that is most difficult to put right again. I'm not sure that plastic ladders would work for us because I usually send the current feed for the lamps up the ladder but I'd still be very interested to know more about your plastic laddering.

1 hour ago, Pixie said:

 

 

Not that hard - find me some photos of them in red on the WR in 1971 and I'll happily build a few. I have got plans to model W80300 in red as it seemed to be a late survivor

 

I'll keep an eye out but IIRC I've seen a couple of pics circa 1967 with a D600 and the full GW TPO set in red and one or two circa mid-70s all in Blue/Grey which leaves a band of uncertainty.

The full GW TPO sets were introduced in 1961 I think - 6 brand new Mark 1 TPOs per set plus a Siphon G. Four different TPO diagrams between the six coaches . For some reason we have not got around to building the full set for St Ruth. We kinda cheat with a set 'inspired by' the North Mail which had just one TPO and a bunch of vans... snag is that although it started from Penzance the TPO didn't get attached until Plymouth... that could be the train shown in those photos because it also had a more daylight compatible schedule while passing through Devon.

55 minutes ago, Pixie said:

First up was some bogies, shoebeams, pantographs and various little details for a pair of Raworth class 70 Electrics. The basic models are resin casts of 3D prints, made available by Radley Models. They're both well out of region and a little early for my 1971 Western Region theme, but as they were dragged from Brighton to South Wales for scrapping in 1969 I felt it was close enough. Both 20001 and 20002 are now more or less complete, save for the handrails and glazing.

Yes but if I'm not mistaken yours seem to have moved to Japan.

Nice models - I also have a soft spot for these and have been tempted to go 'off message' in that direction. Your pans do look good.

Nice work on the Western too. I really must get around to doing more to mine than some time. I'm stuck down an LSWR 'off message' rabbit hole just now though.

Not tempted towards 1960s Royal Mail red for the TPOs then? How hard can it be?

Regards, Andy

I took part in a fairly lengthy thread on the Shapeways forum about this. Several knowledgeable people contributed but the main thing that was absent was any concrete info from Shapeways or the suppliers of the machines and resin concerned. All that I can say is that it has diminished my confidence in Shapeways and this process in particular. I have redrawn some of my models for SLA/DLP but there are some models of mine that don't really suit SLA/DLP  so I am still using SW.

Sorry not really an answer to your question but without an answer from the printer/resin makers and/or Shapeways I think there will always be an element of  'Fear, Uncertainty and Doubt'.

Regards, Andy

Thanks Jim. Yes I think that some sort of bracketry attached to the inside of the tanks is the most likely answer but I'm open to other ideas - it's just one of those things that has never occurred to me as a question that needs to be answered when scratchbuilding a loco... which is probably because I haven't scratchbuilt a loco until now.

A bit more progress. On Friday I cut out the front spectacle plate and a few other odds and sods and tack soldered them to the body. Now the boiler (brass tube) can be tried in place and the thing starts to look a bit more locomotive like.

At the moment the back end of the boiler is held up with Blu Tack. I intend to make the boiler removeable for painting so I need to come up with a proper arrangement to keep this in place - not something I've ever really 'registered' when reading about other people's loco builds. How do other people stop the boiler from dropping onto the motor?

I might still have another go at the spectacle plate to get a closer fit to the boiler top.

I think the next job is to tackle the smokebox. This is complicated by the presence of rivets on the real thing, the front ones following a sort of horseshoe shape around the boiler and smokebox saddle. The starting point for my plan was to steal Ian Smith's rivet press idea...

But whereas Ian made his to fit his Peatol lathe, I wanted mine to go on the MF70 which meant making the punch, limit adjuster and return spring concentric so that's what I did. The punch has a hole down the middle so that a piece of 2mm steel rod can be held in the MF70 spindle to keep the thing in one place while the workpiece is moved around by the XY table... which means... CNC rivet embossing... well, CNC assisted anyway.

Here is the thing in use. Mine has no lever - pressing down on the adjuster with a couple of fingers seems to be sufficient pressure. My workholding arrangement could be neater.

... and without any brass or digits to impede the view...

The press is smaller than I intended because that was the only bit of 1/2 inch aluminium (or any other metal) that I had to hand. It's just big enough for the O2 bits but I will need to make a new 'block' if I want to do any bigger panels in future.

Below is my first go at the smokebox front rivets in 5 thou brass. My plan is to solder another 5 thou layer behind this and then cut around the outside manually. There are a few dummy rivets at the bottom to show me where the bottom corners should be plus one right in the middle. I'm still a little uncertain whether my first attempt will get used - the rivets do tend to make a slight crease in the metal - probably not a big deal on the smokebox front but maybe more of an issue for join lines on otherwise flat surfaces.

That's another place where I could use some advice - how do other people avoid getting creases along the line of rivets?

On 29/01/2020 at 21:03, queensquare said:

 

My rock cutting south of the viaduct isn't as spectacular as the prototype but does serve to conceal the point where the line doubles, a good mile or more earlier than it should. Both the cutting and viaduct were modified ready for double track in the late nineteenth century but it was never extended beyond Midford due to the cost of doubling the tunnels.

 

I think I've seen that photo before but I'd never spotted the temporary narrow gauge track. Not sure what gauge that might be but it looks really flimsy - maybe 15 inch gauge?

Thoughts are now turning back to the O2 body. I'd assembled enough of this to check clearances around the motor etc but then left it to one side while I got the chassis built and running.

Making use of the hard-won lessons from building 2mm scale track and reading about other people's efforts, the obvious next step was to deploy the 80W iron and start taking the body apart again...

Seriously, one side was very slightly further back than the other. We're talking about a few thou but it was noticeable when looking at the overlaps at the end where the bunker rear and the tank fronts will join. Having thought it wasn't too bad when I first assembled the body it has been bugging me so I decided to bite the bullet now before the misalignment is replicated in the cab front and rear panels.

The photo above also shows the N-Brass bits used so far - the two layer footplate and valance etch and the inner carcass for the side tanks and bunker. The tank inner etch had solid sides which didn't seem like the best idea either for soldering or for weight distribution (most of the tank sides are aft of the rear driving axle) so the CNC miller was used to turn most of it into holes. I changed my mind a bit between one side and the other...

The bottom edges were also filed down to reduce the overall height - the N-Brass kit seems to have the tank tops more or less flush with the top of the sides but photos of the O2 show the tops being a little lower with the sides extending up to form a slight lip.

As seen in the previous post, the outer tank and bunker sides were milled to the outline traced from the GA drawing in the Wild Swan book on Adams locos. Here is a side next to the N-Brass G6 etch for comparison...

The O2 is a tad longer and the cab (at least on the Callington locos) is 6 inches lower than the G6. Some O2s had taller cabs.

The observant may have spotted a problem here - how can I build a longer loco using the N Brass G6 footplate etch? Answers on a postcard

At the close of play the body is back together although I decided not to refit the rear spectacle plate for now.

Next step is to get the front spectacle plate done... which also needs to match up with the top of the boiler so that will also mean getting the boiler pitch sorted and probably deleting that cross-piece between the two tank tops.

Hi Both,

Yes Rich is correct. I made my own mounts from aluminium, very much along the lines of the ones available from China/eBay etc. The available ones seem to come and go.

I didn't particularly want to make my own but I did want my mounts to allow me to revert to manual operation quickly and easily and I couldn't find anything else to fit the bill.

If you don't need to be able to swap and change like me then there really isn't much reason to make your own but if you do want more details of the ones that I made then drop me a PM and I will be happy to share the details.

My steppers are NEMA17 45Ncm 2A jobs from eBay. I was uncertain whether these would have enough torque but they seem fine. I'm feeding them 24V and in practice the whole drive system draws about 0.5A in total when running (I only have two axes powered so far).

Regards, Andy

Thanks Izzy. so paraphrasing a lot, there are many variables involved so doing a test piece with the same speeds, feeds etc and then finding the 'fudge factor' by measuring it seems like the right thing to do.

The metal being cut is another variable I think - I found different levels of 'fudge' with brass and phosphor bronze. A bit less with brass IIRC although I wasn't being 100% methodical when I did the brass.

15 hours ago, -missy- said:

There are lots of mods possible on the MF70. I'm currently looking into the possibilities of a motor swap to try and get the spindle speeds down a bit.

Yes the Proxxon spindle speeds don't go down far enough for my liking especially when using 2 and 3mm drills. I haven't looked into changing this myself. I did find a thread elsewhere about the MF70 motor and speed controller. It won't answer your question but it will give you at least some idea about what you are dealing with. https://www.model-engineer.co.uk/forums/postings.asp?th=140490

I must admit that the Model Engineer thread and some info from Rich rather made me doubt the long term robustness of the MF70 and this doubt has probably influenced my thinking somewhat.

One of the reasons for my lack of postings on here recently was the acquisition last August of a bigger lathe to live in my shed. I can now run bigger milling cutters and generally chew more metal off things by doing the heavier grade milling on there. I was also running into the height limit on the MF70 for some jobs (drilling mainly) so moving to the lathe has sorted that too. The Proxxon is now 'CNCed up' so I can keep it for jobs like milling 2FS loco bits which is what I intended it to do in the first place.

The only other suggestion worth mentioning, especially with the Proxxon, is backlash on the table. Backlash on a CNC is bad news.

I found some CNC controller firmware that does backlash correction (see my posting above) and it seems to work pretty well. I found about 0.08mm of backlash on both the X and Y axis on mine, some of which is from the axis leadscrew and some probably from the shaft couplers that hook up the stepper motors.

One thing that I forgot to mention last night is that I've also found that the size of cut tends to be a bit more than the cutter size. I first found this when manually milling the frames for the shunting tractor. I don't know if this is down to vibration, the cutter flexing or being slightly off axis but it does happen and it's not down to backlash. After doing the O2 bogie frames and measuring how they came out I added a fudge factor to the cutter diameter that I told dxf2gcode and the main frames came out pretty spot on.

Cheers Rich.

(non techies look away now)

Speeds and feeds... mostly 40mm per minute when cutting. About 14K RPM for the 1mm cutter, slower for a 2mm cutter. I stick to about 0.2mm depth of cut which means 2 passes for 10 thou... takes maybe 5 minutes per pass for a typical part but when you consider the overall planning and setup time then it's not that big a deal.

My 1mm cutters are from eBay - there is a chap selling a brand called Cobra Carbide made in the US. They have a 3mm shank. No idea if it's a good brand or not really but I tend to think that the US is probably better than some unknown stuff from China. So far since I've had the MF70 I've snapped one Proxxon and two Cobra 1mm cutters (including non CNC work). The 2mm cutter is from the Proxxon set. I used that on the spacers.

Controller - I started with an Arduino Uno and a cheapo (and quite suspect) clone of the Protoneer CNC shield and A4988 stepper drivers. This was running GRBL and got me up and running but I wanted backlash compensation and as you know it can't do that.

I looked at running GRBL on an Arduino Mega - this has a version with backlash compensation but it can't use the same pins used by the CNC shield so that was no good unless I ditched the CNC shield.

Then I found the Marlin firmware and put this on the Mega. It can do backlash compensation and can be set up to use the pins required by the CNC shield. I'd need to dig around a bit to find exactly what I needed to change to make that happen. It's more focussed on 3d printing than CNC milling and its G code is a bit odd but it does the job. It also has the possibility to use an LCD display and keypad and run jobs from an SD card but I don't do that.

There is an rough version of UGS that I use to send G code to Marlin from the PC. See here https://github.com/winder/Universal-G-Code-Sender/issues/1080

Upstream of that I use QCAD for the drawings and dxf2gcode to produce the G code. The latter does the job, at least for simple profiling and drilling work but documentation is very sketchy so figuring out how to get it right is tricky. It is free though.

Thanks Julia, I think it was your blog that first put the idea of a CNC Proxxon into my head. It's just taken me quite a few years to make it happen.

I will probably keep the mf70 as is for a while. My tooling improvement  'to do' list is already long and distinguished.

I haven't posted much on my blog recently so thought I would try creating a workbench thread and see how that goes... so here goes...

As some of you may know MinerChris is building a cameo layout based on Callington in Cornwall for the Diamond Jubilee challenge. I'm calling it 'Cameo Callington' (he isn't).

He's making good progress but I can't see him having time to finish any appropriate steam locos before June so I thought I would take a break from Hayle North Quay and make a contribution.

The original plan was to build an N Brass LSWR G6 kit and put it onto an 0-4-4 chassis to make an O2 class suitable for the layout. It hasn't quite worked out that way but there will still be some N Brass bits on the loco.

For the last few weeks I've been concentrating on the chassis. Some words and pictures in somewhat backwards order...

All put together.

The bits. In spite of appearances here, the frames are 0.5mm phosphor bronze. I'm trying out the Dave Holland 'keeper' style of chassis and so far it's proving very handy during the mechanical fettling stage. The front spacer is solid brass to get the weight forward with a PCB insulating layer. The rear one is Tufnol.

The main frames straight off the milling machine. I must thank Mr Brummitt for his kind advice on the subject of CNC converting the Proxxon.

Some actual milling in progress. You may notice that this is not a chassis component.

It didn't all go right - it took me some trial and error to get the milling parameters sorted. The top one has too much depth of cut.

Bang up to date - after two rounds of fettling the bogie pivot and wheel arches, it finally managed to get through the horrible curves of South Yard's pointwork. The O2 will also be my first South Yard appropriate steam loco.

The body is rather more advanced than shown here but I will save that for another posting when I get back onto that part of the build.

2 hours ago, Re6/6 said:

 It's not particularly cheap but it does go a long way and it won't crack. I mix it with a dash of brown powder paint to take away the whiteness if damage occurs.

 

 

We mixed it with cheap instant coffee for the scenery on St Ruth. John's workshop smelled of cheap instant coffee for weeks afterwards.