Hello and a part-built blowfly

[Lisa]

Thanks Jim, I hope he is.

[Lisa]

Just a couple of little jobs today. Firstly, the bolts for fixing the front crankpin retaining collars arrived, so the coupling rods are now actually held in place:

Cruel close-up showing all my file marks, and lack of cleaning up of the wheel castings.

Secondly, I made and fitted the bushes for the eccentric rods, these are a light press fit in the rods:


I was going to finish the retaining collars for the driving crankpins as well, these just need to be drilled and tapped for a grub screw; however both sets of drill are missing the tapping drill for this, so that'll have to wait for now.

[Roger]

Hi Lisa,
I too have such a camera, and it's amazing how turning things round and lighting them from another angle can make such a difference as to how minor blemishes are exposed.

[springcrocus]

Lisa,

If your camera allows it, try and work without flash at all times. Stuff looks so much better, witness my own work.

Steve

[Lisa]

Thanks Steve, I'll keep that in mind, of course the other option is to hold the camera too close with flash on; I did this before taking the shot above and the rod was barely visible in the nearly all-white image.

Roger, yeah the camera is brilliant at show up every little problem, which can be an advantage at times. Might look into wrapping some fine emery around a bit of tube in the bench drill, which should help polish things a bit. Come to think of it, that's in the construction series for Blowfly... I should probably read that more often.

[Roger]

Hi Lisa,
I have a strong aversion to Emery paper, it rounds off the edges which I dislike, and it's a pain to hold onto a file. I much prefer to use a fine file or needle file with a little cutting oil to draw file items to an acceptable finish. It doesn't give a highly polished surface, but I like the look of it and I can control what the edges look like.

[Jim]

Apart from viewing parts in photos I often hold parts up to a mirror to see them in a different angle/light and that often shows things that I hadn't seen like a slight bump that needs to be taken down more or an edge not quite straight or whatever .
The side rods are looking great too and by the way I only read the instructions when things go pear shaped, then to my amazement they usually warn against doing that which I've just done! Very annoying.

Jim

[springcrocus]

Aug 24, 2016 21:48:30 GMT Jim said:

Apart from viewing parts in photos I often hold parts up to a mirror to see them in a different angle/light and that often shows things that I hadn't seen like a slight bump that needs to be taken down more or an edge not quite straight or whatever .
The side rods are looking great too and by the way I only read the instructions when things go pear shaped, then to my amazement they usually warn against doing that which I've just done! Very annoying.

Jim

Instructions?? Instructions? What are they and where do you find them?

Last time I read some instructions, the first item on the list was

1. Remove all items from the packaging.

The instructions were at the bottom of the box under all the items.

Steve

BTW, soft focus can do wonders for imperfections.

[Lisa]

Started on the connecting rods this afternoon, just turned up the small end bosses. These next need to be mounted side-on in the 4 jaw so that a small flat can be machined where they meet the rod proper. They'll then be drilled and tapped to fix them to the rod before silver soldering; same as the coupling rods. The crankpin bosses were made when I did the coupling rods, and are the same as the driving end bosses on those.

Layed out in a mockup of how the rods will look when done. I wasn't deliberately trying to follow Steve's advice regarding flash (honest!), it just refused to fire; probably due to the lathe work light reflecting off the bench surface.

[Lisa]

One connecting rod is now machined and assembled, the other is awaiting machining. Then it'll be on to silver soldering and bushing; same as the coupling rods.

The length of these rods is right at the limit of what the Taig can do; I have to carefully mark and centre drill the ends with the bench drill, as there's no way to do it on the lathe.

On another note I decided to see what a ME machining service would charge for machining my cylinders; even cutting it down to the bare minimum, and just doing the bits I can't do (boring the cylinder, and machining the port face) was well beyond my budget. So scrap that idea.

[Roger]

I'm sure you'll find a way to do the cylinders and port faces.

[Lisa]

Aug 28, 2016 10:31:51 GMT Roger said:

I'm sure you'll find a way to do the cylinders and port faces.

Thanks Roger, filing and scrapping is always an option for the port faces, if it comes to it.

Meanwhile, the missing drills arrived in the mail today, so I finished off the retaining collars for the driving crankpins by drilling and tapping for grub screws. So these are now in place, and the one assembled connecting rod is there as well:

Afternoon sunlight stopping the flash from firing, but it's slowly looking more like a loco as bits get added.

[Roger]

You can always face off the port on the lathe if you clamp the cylinder to a faceplate or carefully hold it in a 4-jaw.

[Lisa]

Not really an option with this lathe I'm afraid Roger. The cylinder casting is larger than both the faceplate and the 4 jaw (and probably the headstock for that matter), plus the 4 jaw chuck only has about 8mm of depth in the jaws with them in the wide configuration. Here's a pic':


I do have a set of riser blocks that can be fitted to give an extra inch of centre height, but at the cost of some rigidity. I checked a while back, and the riser blocks would be needed to swing the casting, otherwise the corners foul the bed.
It could be possible to mount the cylinder on the cross side (you can see the T slots in the pic') with a special mounting plate, then fly cut the face. This would need multiple settings of the cutter and/or casting though, as there's not enough movement in the cross slide to machine the whole face in one setting.
With a similar setup it may be possible to bore the cylinders with a between centres boring bar; I'd have to make one off the lathe though, as - like the rods - a bar long enough to do the job would be too long to centre drill in the lathe.
So there is possibilities, whether it could be mounted rigidly enough is really the biggest issue (particularly for cutting through the 'crust' of the castings).

Very much open to ideas though.

[Roger]

I see your problem Lisa, it's all down to the size of the kit. Have you got a Model Engineering Club that would help out?

[Lisa]

I'm not a member of any, and there's none nearby in any case (other than grandchester, which is in the middle of nowhere, so I'm not able to get there, or anywhere near, even if I didn't have to look after dad).
So yeah, not sure what to do. But I can work on other stuff for now.

[steam4ian]

G'day Lisa.

Looking at your job I would mount the castings on the cross slide. Dress up the valve face with a file first, even use an angle grinder and flap disk. Use emery paper on a flat surface to grind in the face. You may be able to get away with this as all the 'machining' you will need depending on how true the surface is the cylinder axis. My son has recovered two car cylinder heads using this method.

This surface will be you datum for the next operations. If it is not true to the centreline then you will have to pack it so the casting centre line is true to the lathe centre line.

The cylinder faces can be machined by a cutter mounted in the four jaw. I suggest doing one, the slide bar end, first and then doing the boring without taking the casting off the cross slide; that way the face and bore are true.

The cylinder bore can be machined by a bar between centres with a cutter on it.

The other cylinder face can then be faced

If the valve face needs truing up to the cylinder axis, that can be done last with the cutter in the four jaw with the face machined with the bore as the datum.

Ian

[jma1009]

Hi Lisa,

I would agree with Ian if the cylinders were gunmetal - you might just get away with it. However it will be a real struggle, and you may not get a decent finish. It will also take a long time with various awkward set ups, and very fine cuts so as not to strain the lathe.

For cast iron cylinders I would not attempt such a job on your lathe.

Cheers,
Julian

[Roger]

Lisa replied to my post that there's not enough travel on the carriage to use a fly cutter. I agree, I don't think this job is plausible on such a small lathe. Outside help is needed.

[Lisa]

The Blowfly cylinder castings are the same as for an outside cylinder Maid of Kent, just as a possibly more familiar reference for those having a ponder.

A friend suggested a compound vice, and a milling cutter in the bench drill chuck for doing the port face; which is something I hadn't thought of.

Meanwhile work continues on the connecting rods, with the second one now machined and assembled, and a start made on the silver soldering.

The rod's just had a light clean up, will give it the full file and polish once the crankpin end is fixed in place. Also, that front wheel could do with a bit more of a clean up too.