Arnold building the "Little Blazer"

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sbwhart:
Cracking bit of work that man :clap: :clap: :clap: :clap:

Are you following book plans or are they available on the net ?.

Stew

arnoldb:
Thanks Jason :beer:

Rob, thanks mate - :doh: Must have gotten confused with a Ford Escort dashboard project; hence the fluffy towel :lol: :lol: Wonder where I put the fluffy dice to hang from the rear-view mirror :scratch:. The height gauge is a treat - really makes life a lot easier :)

Thanks David - have to try and make it interesting :D

Thank you Dean. I love the boring head; and that one's mostly your fault :bow:. The home-made bits of kit are getting ever more useful - not as nice as shop bought tools, but they have character :)

Thanks Stew :beer:. Its from a book - "Two shop masters" by Frank McLean and Philip Duclos. Photocopied pages for doing the metric conversion thing on and use in the shop.

Time to finish morning coffee and hit the shop again :coffee:

Kind regards, Arnold

madjackghengis:
Hi Arnold, having built one of these myself and taken close to two decades to get it to run, I had to comment. I built mine from the article in the Home Shop Machinist, which I believe is half size compared to the one you're building, have you decided what your cylinder will be made of and what you will use for piston material? For my half inch bore model, I've made four cylinders and six pistons, using 6061T6 aluminum for the cylinder, and bronze bearing material for pistons. The aluminum tends to score, and I can hone out the bore four or five times and sand the burrs off the piston before I have to make new of each, so when the piston stuck yesterday, when I was running it just to sort of end the day, I bored the cylinder out an extra eight thousandths or so, setting it up in a four jaw chuck and centering the bore first, and have machined a piston out of graphite, out of a spare electic motor brush in fact, and will be making the sliding valve out of the same graphite from another motor brush. I hope to get more than an hour's total run time between rebuilds with the graphite but I've never run it in aluminum before. I look forward to seeing your's run, I made a mess of the cam, machining it in a four jaw instead of on a rotary table, and translated numbers wrong, using a diameter instead of radius, and having a cam which was substantial the wrong profile. As to the spring for the valve, it does not have to be strong, just enough to keep the face of the valve flat and no more spring necessary, my spring is made of a piece of copper sheet about fifteen thousandths thick, and I had to cut off all the excess and reduce the pressure to almost nothing to get the bronze slide valve friction down to almost nothing, getting my little version to run, so start with just enough pressure to keep the valve aligned and flat. I'm looking forward to seeing the difference in getting your larger version running, versus mine, but considering only the work after I figured out all the errors I made, as they don't figure in the virtues of the design its self. I can hardly wait to see the video, you're looking very good so far. :headbang: mad jack

arnoldb:
Thanks Mad Jack :beer: I don't know if you're talking about the same engine; I wouldn't like to build this one in half size - Well, not yet anyway; I would need some 1mm taps first!
I'm making the cylinder from cast iron and the piston from phosphor bronze; I don't have access to graphite for the piston yet. Thanks for the pointers!

On to today's bits.

Phil specifies the clamping screw on the collar as a 1-72 cap screw; I don't have anything that small, so I settled on an M2 machine screw. Head clearance for this screw is 4mm - and the collar is 4.7mm wide; that leaves 0.35mm either side; loads of space :lol: - as long as I could pull it off accurately.
I used the sharp pin to locate the edge of the vise jaw on Y, zeroed it and dialled in 2.35mm offset. Then I located to the center scribed line for the X and locked that:

Then with a 4mm center-cutting slot mill, very gently bored down to 1.5mm above the depth mark:

Next followed a small center drill - just a shallow hole with its tip:

That was a guide for the 1.6mm drill that followed - about 10mm deep for tapping M2:

A 2mm clearance drill followed; just 2.5mm deep, and then I tapped the holes - still in position, but with the collet holding the small drill arbor loosened to allow the arbor to rotate and slide in it. I just chucked the tap in the drill arbor and twirled the shaft with my fingers to tap the hole; it does not take a lot of torque to thread M2!:

As a final step, I slit the collar with a 0.5mm slitting saw:

Some more layout followed:

I used a 10mm mill to clear the big bit of excess away - just by eye to the lines, making sure that the bottom met the curved section in the base nicely:

To mill out the section between the two bearing columns, I had to revert to a 6mm mill. The 10mm is too big here, and I thought I had an 8mm long series. Well, so much for "thought" ::) :

:doh: Notice the ding on the top of the collar ? - :( - I forgot to check clearance for the collet chuck and left too short a bit of the cutter sticking out, so I ran the collet chuck into the collar... Fortunately not to bad; the chuck lost some black off it's closing nut, and the ding was very shallow and easy to file away. I just hate that sudden extra "grrrr" noise!

Then I milled the back end to 10 degrees as per plans:

For laying out the center line for the crankshaft, I needed a plug turned up to fit closely in the collar. This calls for a "scrap" bit of "something - but I couldn't find any, so I used a good bit of aluminium. It was really nice to get back to the lathe for a change :D :

That piece was then just parted off and clamped up in the base collar. Phil recommends clamping the base to an angle plate for the next step; I don't have one, so bodged it by holding the piece against a square with the base edge firmly lying on the glass plate. Then get the height at the top of the plug, subtract its radius, set the height gauge to that, and scribe the center line on the one column:

It looks as if the base is not sitting with it's one edge flat on the glass plate in the photo; that's an optical illusion.

The other "crossing" center line is easily marked from dimensions, and this is the result:

The piece was then set up squarely in the mill again, and the axle bearing holes drilled at 2.9mm for reaming out to 3mm later. At this point it was 14:00 and my elderly neighbours like to take a Sunday afternoon nap. Their bedroom is very close to my shop, so I shut up with the machines for a while, and brought out the small needle and riffler files to clean up the base a bit - after I used a larger file to round off the one sharp edge and the tops of the bearing columns:

A while later, and after some 320 emery followed to get a brushed finish, I ended up with this:

Well, while posting up I noticed it's not quite good enough yet; the one bottom mounting hole came through the base between the pillars :doh: - so that needs to be fixed. And as always, one sees some more places that requires finishing off - the camera is pretty good at showing those up!

Once I heard the neighbours were awake, I started off on the cylinder. A bit of 30mm cast iron - faced off and center drilled:

Then turned down to 1", and cleaned up a bit with emery:

The neck turned down and a trial fit to the base; it had a bit of a step at the back that needed further relieving, so it appears a bit short:

Turning the fins on the cylinder was a no-brainer; much to my surprise :ddb: I thought I'd have to make a turning bit, but found one among my assortment. BONUS - it was already sharp and suitably profiled for cast iron :) And its tip was 1.6mm thick! - Well I needed 1/16" - 1.59mm. That half a thou won't make much of a difference :coffee: And another bonus; my lathe's leadscrew is 8 TPI, so one turn per fin; no messing with numbers! Fins started:

And done - 15 minutes later:

It took longer to get in there with some emery to get a bit of shine showing up in the bottom of the grooves than it did to groove them ::)

Then I bored the cylinder... I'm not entirely happy with the finish inside, so I suspect a lot of lapping will be required later. Not sure though, as cast iron is deceptive. Brass and aluminium will machine to a mirror finish indicating that it is smooth, while cast iron can be very smooth and still look dull...:

I parted off the cylinder .5mm over length for clean-up - then chucked it with some paper to protect the finish on the fins, and cleaned off the back side:

The cylinder to this point; I quit while I was ahead today ;) :

And assembled thus far:

I don't think there will be any progress during the week; so most likely next weekend only.

Thanks for checking in!

Regards, Arnold

raynerd:
:bow: :bow:

Amazing! I`ll be waiting for the next instalment...excellent job.

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