Hello and a part-built blowfly

[Lisa]

Hi everyone, I've just been looking at some of the threads here instead of working on brake gear.

I've recently started looking after my elderly dad full-time, and have taken the opportunity to restart work on a 5" gauge Blowfly 0-4-0T seeing as the remnants of the workshop are available to me. Remnants, as dad sold most of it all off when his health began to decline. So it's been about 10 years since I last worked on a steam loco (rebuilt dad's modified Sweet Pea just before he sold it), and even without the machine tools needed to finish the loco it's nice to get back into model engineering after so long.

The pic' below is what I'm starting with; I got as far as a rolling chassis before this was put away. Valve gear is slip eccentric, which is complete (a grand total of 2 rods). Currently sourcing some BMS for the coupling rods, and working on the brake gear - which isn't actually a part of the original design, but makes sense to have, and is a good re-entry point I think.

[Deleted]

Hi

Welcome to the forum....always good to see a new member with a loco build to tease us with....i look forward to watching your progress....we have a great bunch of people on this forum with a vast amount of experience/knowledge in all things steam...your in good company...

Pete

[Shawki Shlemon]

Welcome to the forum , I guess another OZ member and engine , there are lots of these engines and are very good steamers . Good luck .

[Lisa]

Hi Pete, and Shawki, thanks for the welcome.

Pete; building a 5" gauge Flying Scotsman was somewhat of a childhood dream for me, before I got more interested in narrow gauge, still maybe one day.

Shawki; yes I'm up near Brisbane, not far from Grandchester MLSA.

A mildly amusing Blowfly related tale: about 18 years back my dad was discussing the design with a fellow (QSMEE) club member, and enquired as to how you'd oil the valve gear. The other guy, a well known boiler inspector, took a look at the GA - inside valve gear, side tanks, no frame cutouts - and replied "stand the b*****d on it's end."

[Lisa]

Not much progress the last couple of days, as the usual late september cold snap has made the workshop a less than desirable place to be during the evening/night, which is when I usually work down there.

As such all I've done is cut some steel to size for the brake hangers, and pivot pins for same; I'll turn or shape these over the next couple of days as appropriate.

On the subject of oiling the loco, my current thoughts are to fit a twin ram mechanical lubricator between the frames just behind the front buffer beam. One ram would then feed the cylinders, while the other would pipe out to oil the axles and valve gear. The original design calls for a displacement lubricator, but I'm just not a fan of those. Not sure how to go about driving a mechanical lubricator though if it's located there, as while I could drive it off the valve rod, I've always avoided this; any reduction in valve travel from notching up (not a problem with slip eccentrics, but better to plan ahead in case I fit proper valve gear later) results in a corresponding reduction in lubrication. Another option would be to mount the lubricator on the running board, in front of the side tanks, it could then be driven off the cross head.

[ejparrott]

You need different oils for the cylinders and the bearings. I would fit the lubricators to each running board, driven from the cross-head, one for one oil and one for the other, just remember which oil goes in which! Whenever possible I feel there should be a separate tank and pump within a lubricator, so you can be sure that both cylinders are being fed.

[Lisa]

I know conventional wisdom says to use different oils, but the result of various experiments over 20+ years of commercial operation (at one point 8-10 hours a day, 7 days a week, for about 4 years) of 5" steam showed that it's better to use steam oil for the bearings. The result was a significant reduction in wear; one loco with southern valve gear needed its bushes replaced weekly with a thinner oil, this became quarterly when steam oil was used. The consensus being that on a small loco the heat transfer from boiler/firebox/cylinders is considerably more than on a full sized loco; thus warmer bearings thin the oil more, requiring a thicker oil to begin with to counteract the effect to ensure adequate lubrication.

An added bonus being not having to worry about mixing oils up when there's only one.

[Roger]

That's interesting, it does seem to me that thin oil is likely to become ineffective pretty quickly on linkages in particular where it's not replenished. Although it's not as easy to get thicker oil into those parts, it would seem more likely to stay there if it was thicker. I would doubt whether going as far as Steam Oil makes sense on large plain bearings which have a reservoir of oil though. That's just going to increase the drag unnecessarily, it's surely not going to get to the sort of temperatures that will make it significantly less viscous?
Something sounds very wrong if a locomotive needs bearings replaced weekly!

[fostergp6nhp]

Morris lubricants now do a universal oil formulated for miniature steam so one oil does all.

[Lisa]

Up late (not unusual for me, especially in the warmer months) and doing some scribbling. Putting some thought into the coupling rods, and considering a bit of deviation from the original design for various reasons.

The standard Blowfly design calls for 25x7mm steel, shaped into a dogbone (rounded ends, thin centre), the bushes are then wider than the rods/bosses, but not centred in them. I'm thinking of using 2 pieces of 25x10mm for the bosses/rod ends, joined by a length of 12x6mm which would be threaded and silver soldered into the bosses.

The benefits would be:
Less work with the hacksaw, and thus not wearing my arm out.
What to me is a more pleasing shape.
Centring the bushes on the rods would also centre the forces applied to the rods on the bearing surfaces, which could (maybe?) reduce wear; and would also centre the oil hole in the bush, thus better lubrication.

Here's a quick workshop drawing I made of what I'm thinking:

[steam4ian]

Lisa

Have a look at the coupling rod design for Sweet Pea, it is something like you are proposing but I would think a little bit stronger.

Rod type coupling and connecting rods were used on some low cost contractor type locos.

Regards
Ian

[Lisa]

Ian,
Sweet Pea is pretty much where I got the idea from. I've got a GA from the original EiM(?) series that we had photocopied and enlarged to actual size. Pretty sure the magazines were sold with the loco though (my dad's last loco was a heavily modified Sweet Pea - 0-4-2+T, briggs steel boiler, walschaerts valve gear).
However as I recall Sweet Pea's coupling rods are marine style, with 8mm steel rod threaded and silver soldered to a small plate, with the bronze crankpin brasses bolted to that. Which is similar to what I'm proposing here, but with flat instead of rod between the bosses, and with bushed steel bosses instead of bolted on brasses.

[jma1009]

what you are proposing is similar to the conn rod and coupling rods on the Ffestiniog Railway George England 0-4-0 locos.

cheers,
julian

[Lisa]

Just to show I am actually doing stuff, here's the coupling/connecting rod bosses (as per earlier drawing) getting machined to size in the lathe. The close up makes the bench look messier than I thought it was.
The lathe is a Taig II (Peatol), which is the only lathe I have at present, while small, it's had quite a bit of use, and will do just about everything except the cylinders; to give some idea of size, that chuck is 4" diameter.
The other 5 bosses are sitting on the cross slide for the photo. All have been machined to length, currently machining to height, next machine to width. Then I'll bore the holes for the crankpins and bushes (on one 'end' anyway, will drill the other crankpin hole once the rod is assembled so I don't end up with the wrong dimensions), and then drill the holes for connecting them together into a finished rod.

[Lisa]

Oct 6, 2015 8:36:09 GMT jma1009 said:

what you are proposing is similar to the conn rod and coupling rods on the Ffestiniog Railway George England 0-4-0 locos.

cheers,
julian

The QR A10 (which I have 5" gauge drawings for) was where I got the main inspiration from, but yes looking at the few semi-decent rod close ups I could find of the George England loco's they're about the same; though I'm just going for a round bush in a hole rather than what looks to be split bushes in a slot on those?

[Lisa]

Have just bored out the crankpin hole on one of the front coupling rod bosses. This took a couple of hours as the little Taig II lathe can't drill bigger than 10mm, so a great many 5 thou cuts followed to bring it out to 16mm for the bush, then a 2mm deep 20mm counterbore for the retaining collar to fit in.

[Lisa]

One end of a completed coupling rod, sort of. A trial assembly of the front end of the left coupling rod, still need to turn and thread the other end of the rod for the boss, but this at least gives some idea of the finished rod. The central rod ended up being a little thicker than I originally intended, simply because I got hold of some fairly cheap offcuts of 12x7 BMS, instead of the intended 12x6. I think the thicker material probably worked out for the better anyway.

[Jim]

Hi Lisa,
You're doing a great job there and I reckon your dad would be delighted with the progress. It's interesting to see you using a 'Diamond Cutter', they are brilliant bits of kit with the jig for sharpening guaranteeing the right cutting angle every time. I have tipped tooling but use the diamond cutter almost exclusively and with the other end sharpened in the jig for thread cutting only adds to it's usefulness. With care quite a lot of work can be done on a small lathe. A mate of mine machined a 'bent wire' crank shaft for his 3" Alchin on a Myford 7, it was pushing things to the extreme but he took his time with light cuts and produced a superb job.
cheers
Jim

[Lisa]

Nov 7, 2015 20:31:26 GMT Jim said:

Hi Lisa,
You're doing a great job there and I reckon your dad would be delighted with the progress. It's interesting to see you using a 'Diamond Cutter', they are brilliant bits of kit with the jig for sharpening guaranteeing the right cutting angle every time. I have tipped tooling but use the diamond cutter almost exclusively and with the other end sharpened in the jig for thread cutting only adds to it's usefulness. With care quite a lot of work can be done on a small lathe. A mate of mine machined a 'bent wire' crank shaft for his 3" Alchin on a Myford 7, it was pushing things to the extreme but he took his time with light cuts and produced a superb job.
cheers
Jim

Hi Jim,
I agree, the diamond tool holder really is brilliant, just a shame that the current makers of it don't seem to have the tiny one we use on the Taig II available anymore; it's rigidity has greatly improved cutting ability on such a tiny machine.

A 3" Alchin sounds like a nice model, I've always liked the fine lines of the Alchin traction engines. Dad was more a Burrell fan (apparently he had a great uncle that owned one in Scotland), so we did have a 1" (I think) Burrell when I was little, was fun to chase chickens around the yard with.

[Lisa]

Nov 7, 2015 20:31:26 GMT Jim said:

Hi Lisa,
You're doing a great job there and I reckon your dad would be delighted with the progress...

He is, I snapped a shot of him when he sneaked in to the workshop this afternoon, it's great when he does; his dementia seems to noticeably recede, so it's one of the few times he can actually keep up a conversation.
This pic' also shows pretty much the entirety of the workshop (other than some storage shelves/drawers/racks behind the camera) - the Taig lathe is hidden under the rag to the left, said rag being soaked with oil and is probably why a 30 year old machine is still (mostly) shiney.


Been raining all day here, so took the opportunity of a cool workshop and finished off the machining for the centres of the coupling rods. Camera flash decided it hated me when I went to take a photo though.