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spuddevans:
Well having the day off today I was able to steal a few hours in the playroom workshop.

I started off with the pistons, I chucked one up in the ER32 collet.

I then turned it to 6mm length, turned the diameter to just be able to fit into the bore, then installed an oil groove. Then I used some 600grit and then 1000grit wet+dry to polish the piston to be a nice snug fit in the bore. ( I also eased the sharp edges off with the same 600grit )

I did the same to the other piston, this one was ever-so-slightly smaller ( to match the ever-so-slightly smaller bore ), and so I marked both the pistons and the bores so that I can match them up again, I used a couple of pop-marks on each part.

I then turned my attention to the crossheads, and after hacksawing some brass to make some smaller brass, I started to clean up and square up the pieces, and then to finally size them.

Here they are marked up and ready for drilling.

I didnt want to just rely on the markings, so I used my edge finder and then used the dials to get to the right position. I then drilled one hole before using the dials to get to the next position. This might seem overkill, but one of the blocks of brass was just slightly smaller than the plans called for, so I marked a datum face on both crossheads and indicated off this datum to get to the hole positions. This would make sure that the holes will be in exactly the right places relative to each other ( if not relative to the sides of the block )

I then drilled the hole in the side of the blocks

Here are the 2 crossheads drilled and ready to mill. Can anyone spot the (almost catastrophic) Boo-Boo?

On the second block ( cunningly labeled "2" in the pic ) I drilled the 2.5mm hole correctly, I then moved over, using the dials, to the correct place on the X-axis, and misread, or miscalculated, my dial position on the Y-axis and drilled the 4mm hole 0.5mm too close to the edge ( the centre was 3.5mm in from the edge instead of the 4mm called for in the plans. )
:doh: :doh: :doh: :doh: :doh: :doh: :doh: :doh: :doh: :doh:

Instantly thoughts of how I was going to rectify this sprang into mind, the 1st one being to silver solder a 4mm brass rod into the hole and then to re-bore in the right place. But after I thought for a while it occurred to me that if I make the other 4mm hole out by the same error I can just position the crosshead rods to match. Hence the numbering of the crossheads.

And that's all I got done today. Stay tuned for more of the same, or rather, different mistakes.

Tim

kvom:

--- Quote ---I can just position the crosshead rods to match.
--- End quote ---

Before going any further, go and mark the plan for the top plate with the revised dimensions.

Personally I would just remake that crosshead before doing the milling. :coffee:

spuddevans:

--- Quote from: kvom on August 05, 2009, 07:46:40 PM ---Before going any further, go and mark the plan for the top plate with the revised dimensions.

Personally I would just remake that crosshead before doing the milling. :coffee:

--- End quote ---

Thanks for that, consider it marked :thumbup:

I would remake the crosshead but I dont have another lump of brass that is big enough. :bang: But we'll see how it goes, I think the top-plate is one of the next pieces to make so it wont be long til I'm either ecstatic with joy or I'm buying in more brass :lol:

Tim

bogstandard:
Actually, I think I mentioned that the holes in the top plate should be made slightly larger, purely because this area is the one you are liable to have the most trouble with getting things to run smoothly.

Get the piston rod and crosshead connected, then adjust the rods for a good running position. The main thing that can catch you out, if the threads are not square in the piston rod and crosshead locking nut. They can 'kick' the crosshead out of wack, so only a tweak on them to tighten, rather than a grunt.

Coming along great BTW.

Bogs

NickG:
Tim, that's coming along great. Nice to see screwcutting as we probably don't see enough of that these days. Something I'm guilty of and I will have to practice to get the most from my lathe.

Also, good commitment as it would have been easy to do the rocking engine first!

Nick

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