Hello and a part-built blowfly

[steamer5]

Hi Lisa,
 Just finished reading thru your build. you are doing a great job! Good to see that your Dad still takes an interest in the workshop, mine still plays in his, although the projects have become a bit smaller!
looking forward to how you make the boring bars & how that goes.

Keep up the great work!

 Cheers Kerrin 

[Oily Rag]

May 28, 2017 9:15:56 GMT steamer5 said:

Hi Lisa,
 Just finished reading thru your build. you are doing a great job! Good to see that your Dad still takes an interest in the workshop, mine still plays in his, although the projects have become a bit smaller!
looking forward to how you make the boring bars & how that goes.

Keep up the great work!

 Cheers Kerrin 

Hear hear

[Lisa]

Thanks folks, at present I'm mostly waiting on bits to arrive so that I can continue; I could of course start on something else, but I really don't want yet another unfinished part sitting around.

However some things arrived today, and I can now finish the crossheads, so I might do that and then poke at something else while waiting for the rest.

[Lisa]

I was grumbling to a friend about a blunt cutter a little while ago, so he bought me a new one; unexpected but appreciated nonetheless.

So today I set about starting the frame modifications, beginning with the holes for the exhaust piping.
These were ½" holes as per the original design, which were opened out simply by plunging in with the brand new 16mm cutter (cut like a hot knife through butter), then hacksaw and file to make it into a slot. I was going to mill it all out, but once the hole was to size it was simpler to just cut and file.

The lathe in the background is hanging apart while I wait for the last few bits to make the bolting table.

Next will be to machine the cylinder/steam chest cutouts to size, then I can put the wheels back in and hopefully not have to hack at the frames any more.

[Lisa]

I got the frames setup in the mill for machining one of the cylinder cutouts today, and made a start on the actual milling.


This pic' shows both the rough chain drilled and angle-grinder ground cutout I'm starting with, as well as where I run out of travel on the milling table; that last 10mm or so will have to be filed.
There's about 1mm to come off all up, to get the cutouts to the right size.

[Lisa]

Having spent most of last week in bed with the flu (dad demonstrated his usual bullet-proof immune system by being totally fine), then rounding off the weekend with a migraine, it was nice to get back into the workshop again this afternoon.

So I milled out the left cylinder cutout today, and made a good start on the filing needed for it as well.

The front end of the cutout still needs some filing before the cylinder will fully fit in, this can't be done in the mill due to the buffer beam getting in the way; but I'd very much rather file one side of the cutout than all four, 10mm thick frames are not fun to work with. So there's still a bit more to come off, then I can do the cutout in the other side frame.

I did a bit of a wobbly video, as Roger would say, just for the sake of it; Dad wandering in and wanting to poke at things brought the filming to a halt though.
www.youtube.com/watch?v=N2iB5exsB_E

[Lisa]

This afternoon I finished filing out the frame cutout so that the cylinder is a nice push fit in the cutout.


I've also now set the frames up in the mill to do the other side.

A little package also arrived today, containing the bolts and grub screws needed for the lathe bolting plate, and the between centres boring bars. So I should now have everything I need to finish those, and the cylinders, and ultimately get the chassis on air.

[Jim]

You're making great progress Lisa. Good news too that you now have the gear to start work on turning the rough castings into working cylinders, it's slow but very satisfying work.
Jim.

[Lisa]

Thanks Jim, I was starting to wonder where the bolts had got to, as I ordered them a while ago; I think the couple of metres of threaded rod in the order may have slowed things down, at least that's my guess.
I don't mind slow work, as long as I get there in the end.

[doubletop]

Jun 7, 2017 11:23:44 GMT Lisa said:

I got the frames setup in the mill for machining one of the cylinder cutouts today, and made a start on the actual milling.


This pic' shows both the rough chain drilled and angle-grinder ground cutout I'm starting with, as well as where I run out of travel on the milling table; that last 10mm or so will have to be filed.
There's about 1mm to come off all up, to get the cutouts to the right size.

Lisa

Not wishing to appear hyper critical but I'm wondering why you haven't taken the time (an hour or so) to completely dismantle the frames and work with them as a bolted together pair and machine them more accurately? It will pay dividends in the long run getting the locations of these main components in the right place. The time taken to set up the whole frame assembly, with buffer beams in the way, resulting in a non-rigid setup would be far less if you'd done the strip down. This is not about rivet counting but just a bit of accuracy, later when trying to get all the other motion parts to match up with their mates, located somewhere on the frames, will become more and more problematic as the work progresses.

I'm a relative newbie at this game and learned a major lesson when Don Ashton pitched into my Dart refurbishment and kindly gave me his revised motion design. Bits of it were only a few thou from the original locations, when I asked him whether it mattered, he replied along the lines "do you want it to work". I then made the effort to get everything within a few thou of his design. I now get comments from the old hands on how good my loco goes and sounds. To be honest I have no experience of what “good” really means but I do know that the loco worked well from day one.

It may be obvious but get the major components, axle boxes, cylinders, wheels and quartering and motion plates in the right locations and the rest of the parts will literally fall into place.

Pete

[Lisa]

Hi Pete,

The main issue is that the frames are welded together, as per design. I don't think there's that much of a rigidity issue with 10mm plate welded together, but grinding out all the welds would be problematic.
If I were to make another Blowfly I'd redesign the frames to be bolted together from the start, and do all the machining on them as a matched pair before assembly. The axlebox cutouts were made with the side frames tack welded together as a pair, so I can be sure the axles are parallel, likewise the handful of holes were drilled as a matched pair, but the cylinder cutouts were only ever chain drilled and roughly cleaned up; which was some bright idea I had when younger that I can't even remember the full reasoning behind now.
It's only slip eccentric, so there's not much to worry about with the motion, unless I decide to retrofit stevenson's at some point down the line.
Dad and I spent quite some time, years back, with a 6' pinch bar and a large hammer twisting and pounding at the chassis to get it straight, square, and parallel; I'm honestly not sure I could reassemble it as well a second time, particularly without access to a nice big surface plate.
So all things considered I figured this was the best option, I am taking plenty of measurements off common fixed points (bottom of the frames, axlebox slots, etc) to be sure the cylinder cutouts are in the same place on each side.

[doubletop]

Jun 23, 2017 9:30:35 GMT Lisa said:

Hi Pete,

The main issue is that the frames are welded together, as per design. I don't think there's that much of a rigidity issue with 10mm plate welded together, but grinding out all the welds would be problematic.
.

Lisa

I've been following in the background since your thread started but I had missed that the frames had been welded together which would be problematic. It caused me to run through your thread again and I must say that you are achieving fantastic results. You are demonstrating what can be done regardless of the size of the equipment.

Pete

[Lisa]

I had intended to roast a leg of lamb for dinner tonight, but instead got distracted by the workshop; can't say I'm particularly bothered though, lamb can wait.

So I finished the milling of the second cylinder cutout today, the top of this side was somewhat convex (concave?) and needed quite a bit taken off the ends, but the middle only ended up having about 0.2mm skimmed off. There is however now quite a large lump to file out that the mill couldn't reach.

The top is on the bottom in the pic', just to confuse matters a bit.
That should now be the end of needing the frames in the mill, so I can move on to making the bolting plate for the lathe cross slide there now.

I've also gone ahead and marked the cylinders so that they're now handed; not really necessary yet, but I find it simpler to have a definite left and right cylinder.

[Lisa]

Both of the cutouts are now finished to size, so the chassis is back on its wheels. Naturally I took the opportunity to clamp bits on for a look.


Next, on with the lathe bolting plate, the boring bars, and a packing/fixing plate for mounting the cylinders on said bolting plate.

[racinjason]

Looks good Lisa I remember my blowfly looking like that.
Cheers Jason

[Lisa]

I stumbled upon this offcut going cheaply on ebay, and grabbed it; 2½" diameter 1.6mm wall copper pipe, just what's needed for the dome. So that's the first of the boiler materials started to be gathered.

Buying the materials piecemeal over time will make it somewhat more affordable, so that's a start.

[Lisa]

So, with the bolting plate for the cross slide done, I now need to make another plate to fit on top of the bolting plate, this is both to raise the cylinders to the correct height relative to centre height, and position them for clamping.
I did some measurements earlier, and had a little play about with 3d modelling:


This is essentially a copy of the frame cutout, which bolts to the second and fifth row of holes on the bolting plate, leaving the first and sixth rows for clamping down the cylinders.

[andyhigham]

Lisa, when I machined my sweet pea cylinders I mounted the castings in a 4 jaw chuck, machined the bore and the back face at the same time. Then turned them round, clocked the bore true and machined the front face. It could also be done on a face plate. My brain told me that machining the bore and the back face without moving the casting would keep all the critical datum true to each other. This was using a very elderly Myford ml3, with an oversize chuck

[Lisa]

Hi Andy; a fly-cutter followed by between centres boring will keep things square, I don't have a big enough chuck to grip the cylinders the way you mention, and don't have a face plate. This might take me a while to get everything sorted, but I'm not in a hurry, and it will do the job well.

[Lisa]

Here's the smaller of the two boring bars, tool obviously not cut and ground yet.



A bit of ¼" HSS for the tool, which fits nicely in a 8mm hole after grinding the corners off, an M8x1 grub screw in the bottom for adjustment, and an M5 grub screw in the side to clamp it in place.
I'm missing a grub screw again, so there's a M5 bolt as a placeholder.
The larger boring bar will be more of the same, but 30mm diameter instead of 20mm.