Any question answered...

If an aluminium tube is 42mm OD at room temperature, what would the OD be when heated uniformly to 120 deg C?

You can calculate this for yourself, but 42.1mm.
α=2.1 to 2.4×10^-5.K^-1 depending on which aluminium alloy
ΔT=100K
42×(1+(2.1×10^-5×100))=42.09
42×(1+(2.4×10^-5×100))=42.10

Lovely jubbly. I did look it up but I just found a load of people infighting about the correct way to do it and it hurt my head

Is it the coefficient of linear expansion thing I did at A level? Should it have pi in or somewhere as its a radius thing, now my head is hurting lol

Should it have pi in

The π cancels out if you're minded to go about it that way. Convert the OD to a circumference by multiplying by π, calculate linear increase in circumference, convert that back to a diameter increase by dividing by π

Assuming an isotropic material, all the dimensions increase in the same proportions. The usual trick question is to ask an unthinking person whether the ID grows or shrinks 🙂

Shrinks? The material expands in all directions 🙃

QI klaxon sounding

@el_presidente
Sounds like something by Robert Bowen?
https://www.robertbowenart.com/

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This is more of a cutaway but is not a barracuda

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Amazing, thank you- not quite how I remember it in my head but this must be it - they are so cool, thankyou

Guessing that is where Paul Jackson got his inspiration

Any fire/fire safety experts here? I.e. trainers?

Anyone know any?

I'm planning to start a new project, based on a used high-end steel frame. I don't have any affinity for a particular brand, so I'll pick it based on size, and the steel used in construction.

Can someone please advise what the lightest steel used in production frames across a)70s b)80s c)90s

I guess Columbus Max was no1 in the 90s?

I'm more interested in finding something lightweight, rather than strong/stiff.

Thanks in advance.

Not sure of lightest brand but something in 753 would probably be a good bet for lightweight

Why not titanium?

I'm not sure Max was ever the lightest steel tubing that Columbus produced, I think EL/OS was lighter.

Reynolds 753 was introduced in the 70s and positioned as a lightweight tubing, which predates EL/OS.

Frames got lighter in the 90s when TIG welding became more widespread, I think Dedacciai had lighter tubing than both Reynolds and Columbus then.

Ideally looking for something that has tubing with a small OD and a curved steel fork!

Ishiwata 017 used to be a tester’s favourite for light weight in the early 80s

See also:

Ishiwata 017 used to be tester’s favourite for light weight in the early 80s

FTFY 🙂

Thanks. My paper doodling was getting messy lol

I remember the example in the link below about adding a metre to a piece of string around the earth from school lol

https://jumk.de/math-physics-formulary/increase-in-circumference.php

That's just not true

The metre of additional string around the earth raising it around 16cm? That bit is certainly true

I'm trying and failing to cut very thin leather precisely. I want multiple geometric and curved cuts and i want them identical every time. I just can't do it with hand tools. What's the cheapest laser cutter i could use?

How about a cutting machine?

https://www.johnlewis.com/cricut-maker-ultimate-cutting-machine-champagne/p4801500