Saturday, July 17, 2010

Nickel Plating

I got a bit of Bright Nickel plating salts from Caswell Europe. I'm using a 'slow cooker' (which I pulled out of a skip) as my plating bath and a pure nickel electrode. This solution likes to be a bit warm in use.

I think the main things about plating successfully are: cleanliness and current control.

My power supply doesn't have current limiting so I have to use the voltage control and just watch the mA meter. Its probably gives a slower deposit or something, but I've had good results with it.
Here is one of my electrodes. I just did them for the fun, I really need to nickel plate the copper parts of the diff pump interior.

I did notice how slippy the surface became after plating. Even to run you fingernail over the surface is quite different to the feel of copper. It must become very flat and smooth at a microscopic level.

The Heater Section.

I found a 220v 600 Watt element from a travel kettle. I saw 4" pumps tended to be around this wattage so I'm hoping it s enough for my homebrew version. The good thing about this element is that it came encased in a lump of aluminium. This allowed a good surface contact between the heater and the bottom of my pump.

Unfortunately, when I soldered the base on to the barrel of the pump it domed very slightly. So the flat heater and the base didn't touch as much as they could. So I decided the best thing to do was grind them against each other.
I had some carbide grits so I used them. I did 80, then 220, then 400 and then Brasso. It took and hour or so. I was quite happy with the result. Not perfect but pretty close.

I needed to isolate the element from its metal box, electrically and thermally. I had kept a few blown plug fuses, thinking they might come in handy some day. Ceramic tubing!
I cut the ends off then emptied out the sand.The underside of the element had a three M3 tapped holes in a nice equilateral triangle. So I measured that and marked it on to the metal box. I drilled that out and put an M3 nut and bolt through the holes.(they were proud about 10mm, just enough to hold the fuses)

I put a bit of high temp silicone on to the end of the bolts and stuck the ceramic tube on.

I screwed short pieces of M3 threaded bar in to the underside of the element and these sat neatly into the tops of the fuses!
As this was going to be squeezed against the underside of the pump, I didn't fix it in permanently.

I had a nice ceramic connector and some high temp wire, from an old halogen security light. So I got the power out of the metal box where it could be connected without fear of melting.

Quick, quick clamp

This is a picture of a temporary clamp I made while I was waiting for the real clamps to arrive. It seemed to work OK. As you can see, its made of two pairs of split rings at 90 degress to each other.

8 m4 bolts are holding them together. I had a short ring of tubing and an o-ring inside.

Note the black marker on the acrylic to make it easier to reassemble. I made this by eye so nothing matched up unless reassembled in the same way it was drilled!

Thursday, July 15, 2010

Leaks, leaks and more leaks

Its a moral tale... and the moral is: pressure test everything as you go along.

I'm guilty of rushing a few bit here in retrospect. I got a bit carried away with the excitement of nearly having the pump finished and didn't pressure it at the silver solder stage. Because once you start soft soldering you cant go back and fix your bad silver solder joints.

So for the pump barrel I pumped the system down as much as I could with the backing pump and painted some shellac on to the area that was leaking. That fixed that for now. How well it stand up to the 220 degress plus, I dont know.
This was in interesting discovery. I found a bad lead solder seam which looked ok and worked ok for the last few months. But now I found it was leaking. Naturally enough it was the last place I looked. I desoldered and resoldered everything else, assuming that one was good. Then in exasperation, I pressure tested it. And there it was...

Today I hooked it all up and pumped a but of water through the cooling sleeve. There was a leak there too. Actually two leaks:

One I thought I'd fixed, close to the bubbles in the top photo.

The other at the top of the sleeve. This one only became apperant when I was pumping the water through. I had tested it initally just with gravity and it was fine. But the small pressure of the pump pushed a bit of water above the inlet level and squirted out the top.

High temperature silicone!

Fingers crossed.

Friday, July 9, 2010

The diff' pump video. Looky here.

I've just uplaoded a video to youtube fo the diff' pump as it stands. There are a few posts missing between the last one andthe pump as it is in this video but I'll put the missing info up over the next few days.
In the meantime watch the video! <-- click that!

How to shake a 100mm hole in a piece of steel.

This is me drilling the 100mm hole for the ISO flange for the top of the diff pump. Its a bit of a late post but I didn't have the pictures at the time.
The external measurement of my stainless pump barrel is 102mm. The hole saw was cutting a little too large. I think it wasn't exactly a circle. I've noticed this on other hole saws too.

I decided I'd bend the teeth in a little to give me a tighter fit. Well, you can't do that. I is a very brittle alloy. And I happily snapped off two teeth without too much pressure.

So plan B was to sand the outside of the saw to remove the outer edge of the teeth. Now that did work. Always remembering not to let the teeth get too hot or they will loose there edge very easily.
Here it is whizzing around. I set the pillar drill too its lowest speed. I predrilled the pilot hole too. I wanted to get as little wandering as possible. The whole drill press shook like hell for the first few minutes, until the groove developed.
Again, I stopped quite of the to oil the groove and make sure it was cutting freely. I went all the way through from one side this time. The clamping of the disk was a pain and I didn't think I could line it up again from the other side.
It worked out just fine. In fact, it was bang on. A friction fit onto the tube without any sanding.
That doesn't happen very often...

Sunday, July 4, 2010

Electrical feed-through

Today I decided to leave my base plate intact and feed everything through the 'belljar' instead. I had a few reasons for doing this, ease of access being one.
So I got out my trusty hole saw and drill and cut two 40mm holes in the top of the gas cylinder. It went through without a problem. I stopped every now and then to add a bit of 3 in1 into the groove.
Then I sanded back the paint and exposed some clean metal for the epoxy to stick to.
I cut two 55mm squares of 4mm glass to act as insulation for the electrodes. I drilled these wet with a tile drill bit. 6mm. I went three quarters of the way through from one side then flipped them over to finish the hole. This stops a large flake being pushed off the underside of the glass when you get through.
I used plenty of water to lubricate. The drill was running slow and I was only pressing till I could hear the hiss of the glass being cut.
Then JB Weld again! I hope this stuff works...

These are my electrodes for the filament power. They are 6mm brass rod. I silver soldered a flange on to compress the o-ring, which I hope will seal it up. the square bit is a baffle to stop the aluminium from depositing on the glass and causing a short circuit.

Thursday, July 1, 2010


I was cutting a new opening in my vacuum table and I dropped the bit of ply on to my Bourdon Gauge. It popped off at the lead solder. Eejit.
I put wet cloths around the other lead soldered components and fluxed and remelted the solder back into place. As good as new... or secondhand anyway!

Gas Cylinder Belljar

This is going to be my vacuum chamber. I found it dumped in a ditch so I took it back to the workshop and took the brass valve out of the top. They are in there pretty tight! Before I cut into it I filled it with water to get any remaining gas out. This is a very important step. I then pored most of the water out and boiled the remaining water to get the steam to draw any that might remain out with it.
I cut the base off with my angle grinder. I did all this a couple of years ago in my initial efforts to get a vacuum system going. The base flange was a huge job. I think I cut it with a cutting tourch and spent the rest of the day grinding it into the right size.
The view port is a bit of 50 by100 mm box section and a face plate made of 3 by 25mm ribbon steel. All the steel is brazed together. I only have a stick welder so the brazing is a better option for gas tight seals.
I'm using JB Weld here to stick on the glass view port. I don't know if this is going to be a problem in vacuum but I've read some good reports about it. So what the hell! Its the slow kind by the way.I picked up a radiator bleed valve for €1.40 today. Its new and has a metal on metal seal. I hope it works. I threaded the steel washer which I brazed to the top of the cylinder. I will JB Weld the threads to get a good seal.

Today I have decided to do my electrical feed throughs in the cylinder instead of through the baseplate. I seems like a better option for practical reasons.

100mm Hole in 20mm Al. Baseplate.

Last week I bit the bullet and decided to go ahead and cut the hole for the diff' pump in my base plate. I got the piece of Aluminium plate from a local scrap dealer.(€10). He had mixed cement on it and it took a bit of cleaning with patio cleaner. Its dilute hydrochloric acid I believe. Any way, it attacked the cement well and loosened it after a few goes.
So I decided to use my router and an 8mm straight wood cutting bit. As you can see from the picture I did a test cut in MDF first to see if it would work.
First I drilled a 6mm hole in the MDF and pushed in a pivot made of 6MM brass tube. You can see that sticking out of the wood.
I then carefully measured two points on the base plate of the router one at 102mm dia and the other at 98mm dia. I centre punched them and drilled them out at 6mm. (Don't forget to measure from the correct side of the cutter!). So then I had my pivot point on the router. Easy!
Here is the first pass in the aluminium plate. I oiled the hell out of it. On the cutter and in the channel. I did 8 or 9 pases on one side then flipped it over and needed 4 untill I felt the cutter clear into the groove in the oppisite side. I forgot to mention that the 6mm brass pivot went all the away through the 20mm plate, so it could be used on both sides.
This was a critical point...
As you can see I left 3 tabs holding the plug in place. Aluminium is very sticky to work and I was a bit concerened that at the last minute it would catch the router bit and fuck it all up. The tabs were thin enough to be broken off by hand and sanded back. The process was quite painless, the cutter bit was still sharp at the end. I suppose it took a couple of hours in total.
Note: I firstly cut the 102mm circle to about 3mm depth and then 98mm the rest of the way through. This was to imitate the ISO100 flange design. Just in case I get a gate valve one day...