Arnold building the "Little Blazer"

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arnoldb:
Thanks Mad Jack - I thought the electronics solder would melt... So it's silver brazing for me then; I'd better find the pencil torch! I'm for once trying to stay as close to the original plans as possible on a build ::)

Double thanks Gerhard :beer: - The engine of the month thing was totally unexpected! Feels a bit funny to see the photo sitting there every time I look in on HMEM...

Tomorrow's a public holiday here in Namibia, so I should get some more done on the engine :dremel:

Kind regards, Arnold

arnoldb:
Today's shop time :)

First order of the day was the cam fork - a straight forward milling job to get to size:

And after sawing off from the parent stock, drilling and tapping and a quick rub over emery:

Then I made the cam roller:

This is the second one I made; the first one went on a flying trip while I was trying to clean up burrs - I just heard it hit a wall and something metallic; didn't even see where it went... At least the shop monster got a bit to eat :coffee:

A little M2 bolt followed to act as roller pin - just some brass threaded rod turned down, threaded, and the head section filed to a hex while on the lathe:

Then I had to re-make the cam roller again ::) - I made the original one 3/16" and when I started putting things together, it looked way too small. Misread the print; it was supposed to be 5/16"! Parting off on the lathe no longer intimidates me like it used to, but on these smallish bits I always end up with quite a big burr that have to be removed from the parted face afterward. I tried something different for this one: before drilling the center hole, I parted it to just under the drill size, then center drilled and drilled the hole to size. Works a treat; I ended up with the roller sitting on the drill and only a very light burr:

The finished fork with the roller installed on it:

While posting, I happened to notice this photo was the 2000th one taken with my current digital camera - and I've only had it for about a year. A quick calculation, and it has paid for exactly half of it's purchase price in saving on having 35mm film developed!

The valve plate needs a 0.28mm slot cut in it, and Phil very kindly describes making a small slitting saw for the job. I deviated slightly from his design, but used the same principle. First some 12mm silver steel turned down on the lathe; the section closest to the chuck I just cut using successive parting cuts with the rear toolpost, and then slowly and lightly faced the front section down to obtain the correct width. A very sharp HSS toolbit made this a no-brainer though I was a bit apprehensive of machining to such a thin width initially:

Then some delicate-but-rough-looking milling on the rotary table followed. The first person to spot the boo-boo I made has a choice of one of two prizes:

The prizes to choose from are a) an under-water hair dryer or b) a steam loco catching kit consisting of a bag of charcoal and a bear trap ::) - UK members don't qualify for option b though, as it would just get used to heat shops :lol:
Fortunately, my mill can run in reverse....

I very gently filed cutting clearance behind the teeth, and then hardened the cutting teeth by heating red hot with a blowtorch and dunking vertically in oil.
For this cutter, I didn't bother to temper afterwards; it did not come out quite as well as I would have liked, so will most likely be a single-use one for brass only.

I then started work on the valve plate. Some brass, carefully milled down to size:

And then used the cutter made earlier to slit the top - worked a treat :dremel: :

After using a bigger slitting saw to separate the valve plate from it's parent stock, it was just clamped by the protrusion in the middle, and milled down to the correct thickness of 0.3mm:

A bit of clean-up, and careful flat-lapping of the face (to remove toolmarks and get it really flat and smooth) followed - and that's the valve plate done:

I noticed something interesting while doing the flat-lapping. Normally I can see the lapping starting to take effect very slightly on the outside edges first, but on this one, it started in the middle and took quite a bit of lapping to reach the outside edges... I think while milling the bottom flat, the milling cutter bent the thin outside edges slightly down. Just a tiny detail to consider in future....

At this point my woes really started... I had the bit of 0.1mm feeler gauge to make the valve spring plate from. Mark-out went easy and a pair of tin-snips made short work of trimming it down. Then I had to consider drilling a 2mm hole in it to fit on the valve pushrod. Thin plate and drills don't go well, so I sandwiched it between some aluminium scraps clamped with a toolmaker's vise:

Drilling went well, but I could feel that this feeler gauge plate was something different; it was tough to get through with the drill...

When I tried bending it, this happened:

:bang: - this steel plate does not like bending...

That was the only bit of 0.1mm plate I had... The off-cuts are too small to use, but I used the busted bit to do an experiment; I tried bending it around some 1mm rod, and that went OK:

Except, when I tried the minutest adjustment after the original bend, it promptly snapped again.

I tried bending it while heated red-hot with the pencil torch; same result. I had a closer look at the feeler gauge set this came from, and it's made by Gedore in South Africa - pretty good quality kit - hence good quality, but frustrating, steel in this case. I thought it was a cheapy set of imports; what a waste of good tooling. At that point I decided to call it a day and have a good sleep over what to do next for the valve plate spring. Besides, it had started raining here and rain is best appreciated sitting on the stoep (porch) with a very cold beer in hand.

Regards, Arnold

arnoldb:
:) It helps to sleep over problems...

This morning when I woke up I knew where to find some plate that should work; amongst the scrap from the old dot matrix printers that I'm stripping for parts. I found a bit that was 0.12mm thick - and appears to be stainless steel:

The third time round making a bit goes quick; a couple of minutes later, I had the valve plate spring:

All set up for silver brazing; I squashed a tiny bit of flux into the groove before fitting the two pieces together:

Poking at this lot with a thick silver brazing rod was hairy, but I got the job done - sort of. After some cleanup:

Next I raided my acoustic guitar for its high E string - Its been years since I played it as I tend to hurt my ears - and started making springs; something I've never attempted:

I made a booboo on this one; I need a compression spring, not a tension spring; but it was good practice. The spring's internal diameter must be just over 2mm in my case, so I used a 1.5mm drill bit chucked in reverse in the pin vise. The start of the wire was just squeezed between the jaws of the pin vise with a sharp bend to get started, and I turned the chuck manually by left hand - while just keeping tension on the wire and guiding it with my right hand.

After making a compression spring, I had this:

Not the most beautiful - but functional. It would have benefited from a proper guiding setup instead of just trying to wind the spacing by eye...

Next call of the day was the flywheel. Roughly trimmed down to size on one side:

The boss in the center is called for in the plans; I nearly missed it - and would have had to make a spacer later on if it was not there.

When I built the Grasshopper engine, I made up this double-sided tool for doing undercuts in flywheels :dremel: :

Flipped around, and the other side done. For now, I left the excess on the outside, and only after I took this photo realized I had not completed the hub:

On to the RT on the mill; some 8mm holes drilled:

And then milled further with a 10mm end mill:

Back to the lathe, and this time with some suitable short stock chucked in the 3-jaw, then press the flywheel against the jaw faces with the revolving center - and with a bit of cardboard in between the wheel and jaws to provide friction. Turning the rim to final size was then a breeze:

Then back to the mill to spot face, center drill, tap drill and thread the hub for a grubscrew:

I needed some M2 grub screws... Some bits of M2 threaded stainless steel were slotted 0.5mm for a flat screwdriver:

I just used a junior hacksaw to saw them off after slotting while still held in the vise.

Hmmm, let's see now.... Going back through the plans, there's little check marks next to all the engine parts, and I made the additional ones I needed... Al that's outstanding is the base and burner. Some assembly followed, with some careful adjustments to work out a couple of tight spots, and a test with a recalcitrant pencil torch that does not want to stay lit with a smaller flame:

:ddb: :ddb: :ddb: - it's alive; not very well yet, but a good sign :D
I'll try and finish the base and burner tomorrow and get it running properly :)

:beer: Arnold

scrapman:
Hi Arnold :wave: interesting build and it's a runner :clap: :clap:,

Ray.

Stilldrillin:
Arnold.
A runner! :D You're wearing that big long distance smile! :ddb: :ddb:

Very well done, and shown...... :clap: :clap: :thumbup:

David D

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