Thanks Decoy, there are a few contact points between the baffle and the condenser wall, I will tweak it to get as many contact points as possible for the reason you give, and having to ram the baffle in tight should make a big difference. I am pleased to hear another confirmation that the first run will pick up dirt and nasties despite all appearing to be clean.
The tap within a tap is done, now I have a coarse and a fine adjustment in one. The original tap does all the adjusting in 1/8th of a turn, and there is also a half turn of backlash; ie the threads are very big and loose.
I did the mods on an identical tap in case there is a stuffup, and will insert just the modified spindle into the tap on the condenser.
Here is the original tap assembled and exploded, note the black graphite seal in it's compression flange (it looks at one with the flange) - the graghite can be crumbled and recompressed not as tight:
- OrigExpl.jpg (18.76 KiB) Viewed 7041 times
I drilled a hole all the way through the spindle to fit a stainless bicycle spoke. The drilling was done freehand and eyeballed from both ends, starting with a 1mm drill and following with a 2mm drill - luckily ended up pretty central. I cut some flutes across the threads of the spoke to turn it into a thread cutter. Because the thread cutter is not the most efficient, the threads are tight and there is no backlash. The threaded part of the spoke is a bigger diameter than the spoke wire. Left pic is a close-up of the top right pic where you can just see one of the flutes in the thread to make it a cutter, top right is the spoke in the freshly drilled hole, bot right is using the spoke to cut some thread at the top of the brass spindle. Another piece of spoke with good threads was used for the final needle.
- drillAndThread.jpg (18.33 KiB) Viewed 7032 times
The spindle threaded in and a handle attached. I had to take the handle off later in order to put the spindle in a chuck when making the needle point. It was spun in a dremmel type motor and held against a file, and fine corundum paper. The handle is silver soldered with jewellers hard silver solder, (I am a jeweller by trade and these fiddly bits are easy...the big stuff aint!)
- 009 spindleWithinSpindle.jpg (20.31 KiB) Viewed 7026 times
I drilled some holes in the side of the big spindle of the tap, it is already hollowed out so there is plenty of space for the alcohol to flow to the needle. A bronze cap with a small hole for the needle seat was brazed on, closing the hollowed out portion except for the needle seat. The spoke was sharpened into a needle setting the length carefully so that the thread travel matches the open/closed position of the needle. In the left pic the needle is fully seated, right pic the needle is full open. You can see a faint line around the bevelled end - that is the seating point of the main tap.
- spindleComplete.jpg (16.87 KiB) Viewed 7008 times
Complete tap, the handles of the needle valve were bent up for better clearance:.
- finComplete.jpg (13.81 KiB) Viewed 6997 times
The outlet hole of the needle valve is 1.8mm in diameter (a tad smaller than the 2.0mm needle). If I need more output than what the needle hole can give, I can then crack open the main tap and fine adjust with the needle. The needle valve needs 6 turns to go from closed to full open.
Next step after installing the modified spindle is to treat the brass and re-run the first run.
Edited 9/12/08 to improve the explanation.
and while I'm at it here is the stand and burner lit up:
