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What do you do when you're given some 1.25" aluminium Hex bar

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Joules:
The only thing I could think of for hex bar.

It really just started as a way of testing the accuracy of my collet blocks and a deeper learning of the DRO on my mill.  Work has dried up and I was given the bar to have a play.   I didn't get any pictures early on as I was just having a play and didn't think it would come to much.  I only did a CAD drawing of the crankcase once I got to the point of boring it out.  About 30 mins to draw in CAD and then the rest of the day making this and one other I cocked up earlier when I got distracted and forgot the allowance for my parting tool.   So I have a second crankcase shell, just 2mm shorter !!!

I will get to use the Turnado for making the front cover, it initially looked like it would become a solenoid engine, but as the cylinders can be swapped out it could also be compressed air with poppet valves, or just a desktop model with an electric motor inside it.   Just having a play about and learning to use the tools I have.

SwarfnStuff:
Jolly good, now we await the story of how it becomes whatever you decide to turn it into. New tools / toys definitely need playing with.
All the best,
John B

awemawson:
That crank case is crying out for hexagonal barrels and hexagonal pistons  :lol:

Joules:
Quite a coincidence Joe posting in tools about his 12 sided "Hex" blocks.   I ran into the exact problem he relates too doing the crankcase.  The hex blocks gripped by the faces in the mill vice resting on the hex edges, that are rounded.   What I hadn't realised was the 0.2mm error across those edges.

So how to measure the faces of my little crankcase relative to the internal bore.   I got a set of thread measuring wires a few weeks back, something I should have bought along time ago.  But you can use them for so much more, they are very accurately ground.  In my example 2 wires fitted in a cheap Aldi adjustable vice support the internal bore of the crankcase, the wires chosen fit within the anvil of my mic, they will also average out any burr on the internal edge of my cylinder bore.   I am not measuring the thickness of the crankcase, just the difference between faces.  I would need to work out tangents and loads of maths to do that (too lazy, life's too short)

The mic is gently placed over the face and wires and lightly wiggled to set the wires and crankcase.  Write down the readings and find your lowest face, that is now the reference.  I have 0.005" to come off face 5 and 0.002" to come off face 1

And a little further CAD down this rabbit hole.

Joules:
I think my cylinder design is now finalised, I made this test cylinder in Delrin this evening.  The thing is tiny, black and a bugger to photograph.  It still has another 3 operations to finish.  The fins need cutting, trimming the flats on the flange and exhaust ports opening.  As this is Delrin I opted to bore it 1mm undersize.  I might make another in white Delrin to make sure my procedure is sound.  It has an overall length of 14mm, the flange is 1mm thick.

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