Martin M Surrey

[Martin MerringtonParticipant @martinmerrington30203]

Building a Stirling Hot Air Engine from Roy Darlingtons Book

[Martin MerringtonParticipant @martinmerrington30203]

Just started creating the cutting list, some very odd sizes like 66mm OD square alumium box section.

Interested as to whether other people have had the same problem sourcing the materials for the

Silver 11 single cylinder boat engine?

[roy entwistleParticipant @royentwistle24699]

I thought aluminium was still in imperial sizes

Roy

[richardandtracyParticipant @richardandtracy]

66mm is about 2 5/8", so probably imperial.

Our local stockist has mostly inch stock quoted in mm, but as imperial dies wear out, they're replaced with the nearest sensible metric, eg 8x4x1/4" box is now 200x80x6mm

Regards,

Richard.

[SillyOldDufferModerator @sillyoldduffer]

You can get box section in both Imperial and metric; not sure it helps much because 66mm doesn't seem to be either! 66mm is 2.6", which is fairly close to 2 5/8" as Richard says, but I've never seen that size listed. (I only know about 'ordinary' suppliers though)

Could it be a US standard size, or perhaps an obsolete size?

[Neil WyattModerator @neilwyatt]

Welcome to the forum Martin.

I suspect that it may have been intended to use 2 1/2" square (63.5mm) tubing?

Can you substitute this size in the design?

[SillyOldDufferModerator @sillyoldduffer]

I think it's a US size: 2 1/2" inside with the wall making 66mm outside. Just guessing, it appears they have a range of box sections that will fit one inside the other, perhaps for making telescopic poles. Our 2 1/2" O/D would slide into their 2 1/2" I/D. Not noticed anything that would fit together like that over here, perhaps I'm dreaming…

Is this one of those projects needing access to a well-stocked industrial scrap box circa 1956? With the sort of optimistic instructions that say, 'I found the Uranium lying in the road near Aldermaston, but I'm sure your local Nuclear Power Station will let you have an off-cut for a few shillings…'

Dave

[JasonBModerator @jasonb]

Looks like the wall is about 3mm or 1/8 thick from looking at photos of his engine, he's also from the UK

[Martin MerringtonParticipant @martinmerrington30203]

Hi folks thanks for the replies, the American idea might be worth investigating, otherwise I will have to make up the box section from sheet. The item is the main crankaces for the engine so I can't really use anything other than the correct size. The plans in the book Stirling and Hot air engines by Roy Darlington & Keith Strong are beautifully illustrated but all dimensions are in metric, a lot can convert readily to imperial but not this one.

cheers

[not done it yetParticipant @notdoneityet]

Surely other dimensions will reflect the wall thickness? How about some more dims?

[Michael GilliganParticipant @michaelgilligan61133]

Martin,

This is wild speculation on my part.

I suspect that the engine in question might be the single-cylinder version of this one: **LINK**

http://www.stirlingengines.org.uk/boats/dboat.html

… if so; perhaps you could do a quick 'sanity check' on the quoted dimensions by scaling from this photo: **LINK**

http://www.stirlingengines.org.uk/gifs/boat/roy3.jpeg

MichaelG.

[Martin MerringtonParticipant @martinmerrington30203]

Thanks fro the input, have now found a 70mm square box section with 4mm thickness, giving 62mm inside dimension, and have also found that all the attachments go from the end plates so I should bea ble to accomodate the 2 mm difference.

cheers

[Author]

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