Zinc based alloy?

That'll be this one then:

Haynes hot air engine for schools

Rod

Probably not in this case, the low melting point of alloys such as ZL12 made them easy to cast with the smaller school furnaces or even in a ladle with a big brazing torch and as teh OP wants to keep it looking as close to the one he previously made the colour of brass would also be wrong on the usually unpainted rim.

Should look like this

Edited By JasonB on 30/04/2020 13:12:59

The very same one. The original books are going for silly money (if you can find them).

I suppose the point of specifying Zinc Alloy like Zamak, or as my Dad called it 'Sh1t Metal', is its easy to melt and cast - no problem at all in a school metalwork class and very educational. Car door handles used to be made of it, and an ordinary blowlamp could melt them in a steel saucepan.

For a flywheel, almost anything roughly the right size and weight will do. My few examples were machined from a 150mm dia Aluminium rod or turned from a Cast-iron block cut to an octagon with an angle-grinder.

Trust me, I'm a doctor. Angle grinding cast-iron is only a teensy-weensy bit messy. Hack a lump of it in your living room and wifey will think fondly of you forever...

Dave

I assume the zinc alloy is heavier than aluminium, but not as heavy as steel. Otherwise, having cast the base in aluminium, why not cast the flywheel in aluminium at the same time? I think I'm going to go for steel, with additional machining to reduce the mass.

.

For info. **LINK**

https://www.dynacast.com/en/knowledge-center/material-information/die-cast-metals/zinc-casting-metals/zamak-3

[ other alloys are, of course, available ]

MichaelG.

Partly it would have been a case of how old Mr Haynes was at the time he wrote up the design. Someone actively making things by casting in the '50s and '60s would have thought in terms of a zinc based alloy which was being used at the time for dinky toys, lawn mowers, car door handle, bits of new fangled home appliances like 'fridges and washing machines. Aluminium was still more expensive and less available as scrap as well as having a higher melting point. I remember melting bits of my broken dinky car lift in a tin on the living room fire must have been about 1965 only a yard from where I'm sitting now.

Table of relative specific gravity values for metals at link below, for future ref.

**LINK**

The old style Zamak alloys as used on cars and appliances were around 7-7.5 spec gravity. This is close to cast iron or steel, which will have a silvery grey colour similar to Zamak. Some brass alloys are close to the 7.5 ish specific gravity but are not silvery colour of course. Aluminum alloy is 2.5 ish in specific gravity, not so good for flywheels.

Regarding possible use of brass, a 100 mm dia x 25 mm piece of brass bar or a 100 x 100 mm plate 25 mm thick will not be cheap and may not be too easy to find (not available in those sizes at all where I am, as an example) aside from the colour difference from Zamak.

Cast iron or steel will also be relatively much lower in cost than brass and may be easier to find also.

Just food for thought, my $0.02 worth. Ready for the usual forum arguments and opposite opinions.

NDIY must be a mind reader!

I was thinking of Brass, since it would be heavier, and so provide a better flywheel effect. Plus, am not a home foundryman.

Being old enough to remember the Mazak die castings used for mirrors door handles etc on cars, I dislike the stuff, for it's tendency to porosity. We used to call it monkey metal!

Howard

To sidetrack the subject, Dave’s (SOD) mention of using an angle grinder indoors brings back memories of when I used one to cut a doorway indoors, it was many years ago but I still have to tread carefully when mentioning angle grinders within earshot of my long suffering wife.
Dave W

Glad I'm not the only one, despite having 'sealed' myself in whilst cutting out a section of block wall in the living room, wife came home to find the living room (and the basket of clean washing) awash with grey dust, to top it all, it was a few days before Christmas, just a shame the video of me on the patio vacuuming the Christmas tree did not win me £250

Just come across this thread. It's exactly what I'm doing and made my version at much the same time as Bos'un. I never did find the plans on the internet, but sourced then from a school in Woolangong South of Sydney when working in Perth. I never did find where my original went.

Does anyone have a link to the other two booked in the series: stream engine and electric motor oil believe?

Bos'un - where did you get your flywheel cast?

Hi Avon,

I didn't get the flywheel cast, I made it from Mild Steel, with a slightly thinner web in the middle to reduce the mass.

The engine is now complete and running well, and Dad is proud of the result once again.

I've now added an eight coil copper cooling jacket to the "cold end" of the transfer cylinder. 4mm OD x 3mm ID x 1m copper tube, and a small 3 volt submersible pump to circulate the water. Works a treat.

I'd love to post some pictures, but I still use a phone with buttons and a 35mm OM4Ti camera.

I remember wrapping wet papertowel around the cold end - it went like the clappers! I've been thinking about how to improve it, but first I'm just going to get it made and running.

Where did you source your transfer cylinder material - I haven't found any tube with the thin wall required - I've considered rolling my own from suitable plate, but thats another complete project in itself.

Regards

PS. Get your grandchildren to take the photos!

Good afternoon Avon,

The material was sourced from Metals United Limited in Christchurch (UK). "brilliant2buy" on Ebay.

It was 25mm ID x 35mm OD, thick wall tubing in a 300mm length. It was possible to make the transfer piston and cylinder from the same stock.

Grandchildren, what grandchildren? Maybe the kids next door instead. Mind you, once they've taken them, I've then got to do something with them!