Strictly.... “ Hot Air “

[Twizseven]

Liam,

Are you intending to make the key tapered (1:100).  I found this an interesting exercise, a) making the tapered key especially as it is so small b) putting tapered keyway in the flywheel.

Colin

[ettingtonliam]

Very probably. I've got a slotting tool which can be adjusted to cut at an angle, and the key is just a filing job till it fits. Mine are anyway.

[Alyn Foundry]

Great news….

After seriously long negotiations I finally managed to get the manufactures to reconsider doing the 185 gram Tuna tins. We had to compromise at 198 grams though…. I mentioned that the lack of this size of tin was severely hampering the construction of Robinson hot air engines.

Seriously though, it’s looking like Tuna Mayonnaise for tomorrow’s breakfast.

Cheers Graham.

[Jasonb]

Will be interesting to see what difference that extra 13g capacity makes

[Alyn Foundry]

Will be interesting to see what difference that extra 13g capacity makes

My toast overfloweth…. 

[Alyn Foundry]

After a serious mishap with my latest build the foundry went into overdrive after a call for help.

My castings are ready 24 hours after the call. They sent me photos of the moulds. Take a good look at the second picture, what do you see ? 

Cheers Graham.

[Twizseven]

Distinct lack of a route for the poured metal to reach its destination.

Colin

[Jasonb]

I think they have scooped a bit out in the first photo though maybe Graham did not want to to feed the underside of the cylinder rather than the foot?

The foot and underside of the cylinder look concave, understandable where sand has been scooped out and meets the cylindrical part of teh cylinder but foot should look flatter. The shadow may be fooling us, the two green bits are the only uncut part and look straight, the red marks are exaggerated scallops where they have cut the runners

J

PS We also need full details of this mishap

[Alyn Foundry]

PS We also need full details of this mishap

Well, as we all make mistakes from time to time…. Not so much a mistake in this instance but an un noticed problem with the highly “ chilled “ top mounting lugs. It took several attempts to drill and ream the 3/16” hole and the bit must have followed the easiest route. The problem only became apparent after fitting the link motion.

The “ chill “ effect had also found itself in the three legged base. Even after several minutes in the gas Forge at around 850 degrees C followed by a very slow cooling ordinary HSS drills wouldn’t even mark the surface.

This casting has to have three holes at 120 degrees for 1/4” Whitworth tapping, 5.1 mm. The solid Carbide drill bit I ordered from eBay got lost in the post so I re remembered an old trick from my days at Chester UK.

Masonry bits are cheap as chips, with a really tough Carbide tip soldered onto a softer backing. Using my trusty Diamond in Borozon wheel I carefully re profiled the top cutting edge from the triangular top form to a single cutting face then gently removed the sides to get the desired 5.1 mm diameter. Back to the rotary table under the big drill press and within seconds the holes were through. I’ve never worked with such a tough casting, ever!!

Putting the threads in was also a serious challenge using a first taper Presto tap. Needless to say I will be needing a new one. I just managed to get a three to four turn start in each hole ( 1/4” thickness  ) before risking a breakage. This foundry is definitely NOT on my Christmas card list….

Cheers Graham.

[Jasonb]

Temp sounds OK but would have thought a bit longer heating time needed.

Would the pivot on the top of the cylinder be less likely to give problems if you did not core the slot, makes it a bigger lump so should not cool as fast and easy enough to mill the slot.

[Alyn Foundry]

Jason.

Rather than further clutter Jo’s Bailey build I’m replying to your question here….

I’ve just finished speaking with Geoff from the Anson engine museum. There’s no record of any drawings for the Gardner vertical hot air engine and, it would seem they never applied for a patent for it. The only known example is currently owned by Adrian from Engineers Emporium.

I mentioned the vertical Robinson patent engine, here’s a picture.

Cheers Graham.

[Jasonb]

Thanks Graham, I might try contacting Adrian and seeing if he can take a few photos and give a couple of sizes. It's mostly the conrod(s) and detail at the top of the piston as that can't be seen otherwise it's reasonably straightforward.

The water jacket would be a steel fabrication, two side frames could be fabricated or CNC cut from solid and same for the flywheels from slices of CI bar.

I think the Gardner is more appealing to me than the Robinson.

J

PS how is your eye?

[Alyn Foundry]

PS how is your eye?

Still sore Jason, so I’ve been unable to get out in the workshop.   

I too favour the look and simplicity of the Gardner engine.     

[Alyn Foundry]

More on the Robinson vertical hot air engine.

It seems that there’s at least one survivor of his 1881 patent, built under license in New Jersey USA.

<a href="https://www.youtube.com/watch?v=pQ6No2-cpuQ" target="_blank">http://www.youtube.com/watch?v=pQ6No2-cpuQ</a>

I’ve also got the patent drawings. Just a tentative question to those interested in building hot air engines.

Would anyone be interested if patterns and castings were made for a half scale replica from the patent drawings?

Cheers Graham.

[Jasonb]

Only if they came with a 13" swing lathe thrown in as a freebee

That will limit your market. 1/3rd scale may suit people more as that gives a 8 5/8" flywheel. Even 1/4 scale would work with a 5 1/2" flywheel and 2" bore