Potty Over Crank Wall Engine

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Stilldrillin:

--- Quote from: sbwhart on February 26, 2011, 06:01:43 AM ---Bin thinking about the marking blue, I guess on a dull or black hot rolled surface marking white would show up the lines better, I think I've seen castings marked up this way I wonder what was used, any ideas.

Stew

--- End quote ---

Stew.
When I wor a lad...... ::)

Every morning I had to crush a lump of chalk, big as me fist, and mix it with water for the marking out department men.

They painted on. Then blew dry with the airline, when in a hurry. :thumbup:

Used on iron valve castings. Daren't leave any lumps in....... :doh:

David D

scrapman:
Hi stew :wave: the build is looking great, sorry about your dad i know what your going through my mother had vascular dementia,

Ray.

NickG:
What about those white paint markers? Don't know what they'd be like but worth a try.

Rob.Wilson:
Hi Stew

Cracking job you have made of the rods :bow: :bow: :bow: :bow: ,,,,,,,,,,,,, Will this be your next engine publication in model engineer :poke: :poke: :)

Rob

sbwhart:

--- Quote from: Rob.Wilson on February 27, 2011, 03:39:42 PM ---Hi Stew

Will this be your next engine publication in model engineer :poke: :poke: :)

Rob

--- End quote ---

Hmmmmm depends on how it comes out Rob, little bit concerned about the size it looking as though it will be a bit bigger than I had in my minds eye, its scaled at 1/3 of the full sized engine I think I would have been better if I had based it on a 4" fly wheel which would have bin about 1/6 th but that would have led to other complications.

Any way on with the build :-the split big end bearings, I was concerned that to make split bearing is waist-full on material, then John suggested to make them from two bit of oblong bar milled of square and held in a four jaw. I had already got some brass plate put aside to make the eccentric straps, when I measured it up I realized that I could get the split bearings out of it as well.

So soldered the two half's together as John showed in his resent post

Square it up in the mill and with a slitting saw cut the bits out:-The square bit will make the Straps and the the long bit at the top the bearings.

For the bearings square the bar up making sure to get the join on centre, then grip it in the self centering four jaw, turn up dia then drill and ream the bore and part off to length.

Apply a little heat to separate

To finish off fit a small dowel in the hole I drilled in the con rods and mill a small flat in one bearing half, the dowel will stop the bearing spinning in the housing, like a key.

Thats them done

Eccentric straps

Taking the same amount of both sides so the join stays central thin the blank out a bit

Then drill a 10mm hole in the middle, turn a mandrell up and use this to mount the blank on the RT line the RT up using the centre in the mandrel.

Scratch a centre line using a centre drill held in the chuck.

I used CAD to work out the angles to generate the strap.

Then first drill the corners 3mm

Then with a 3mm slot drill mill out the shape.

With the straps still on the mandrell and using the mandrell to find the centre line drill the strap M2.5 tapping and drill a 1/6" hole to help locate the rod.

Then line the scratched centre line up using a parallel.

And with a 1mm slitting saw split the strap in half.

Tap one half M2.5 and open the other up to 2.5 and bolt the two half's together, then in the four jaw, (check the split is on centre) bore out to for a nice running fit on the eccentric sheath.

Separate the two straps by heating them up.

To face the straps to thickness you need to ensure you get the bolt holes central so turn up some little bushes 4mm dia and fasten the two half of the strap together with these bushes.

Turn up a mandrel same size as the sheaths, I used the bit of bar the sheaths were made from, clamp the strap to this and with a sharp tool, small cuts and time, face the strap off until you just kissing the bush, turn it over repeat the other side and the hole will come out in the middle.

Done

This is what it's looking like

Stew

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