I have not posted in a while, got to that point where I need some more funds.
I had a query on the vapor blaster I built, so maybe I will share some of that detail. The surface finish attained is well worth the effort, and it has quickly become my all time favorite cleaning device, not just for bike use.
Basically a slurry of fine galls beads and water is formed by continuous agitation of the mixing tank. this slurry is then pumped to a ceramic mixing nozzle where air between 2 - 3 bar is forced through a venturi and carried the slurry to the work piece. The action is very gentle and has more of a peening action which closes up the pores in the metal, so it does not attract dirt. For aluminium I further bake the piece at 200 Deg. C for 30 min, to form an oxide layer. The only negative about this process is getting all the glass beads out of threads and other cavities. You are well advise to ram balls of masking tape in to all blind threaded holes and clean well with a high pressure jet of water afterwards as well as compressed air. Even then you may have to run a tap down threaded holes.
The device mostly consist two large plastic barrels, on cut in half to for the slurry mixing tank. A standard 0.75kW pool pump (We in South Africa have lots of these owing to the weather being warm!) the shaft seal does tend to wear out say every 6 months, but they are cheap and easy to replace. You know it is worn when you and up standing in a puddle of water!
I made a steel stand as a base to house the pump, and act as the platform for the mixing barrel. I used standard pool type fittings and valves.
The valves seemed like a good idea, but when they get full of slurry the just jam, so in effect you get one chance to set them. The one barrel is cut in half and used as the mixing vessel. It is better to use the half with the caps in it, so you can easily drain it when required. The pool pump is mounted bellow the tank. The output of the pump is fead to the mixing nozel, and a return stream is also sent back to the mixing vessel to agitate the mixture. i use an adjustable nozzle that is positioned in such a way to keep the mixture swirling, and off the bottom. It takes some fiddling to get this right.
The main spray chamber barrel has a large window cut out of it, and I fabricated a steel section to hold a pane of glass. I also added a 12V windscreen wiper motor to keep the glass clean. I use rubber gloves and now use retaining rings form a sandblaster to hold them in place. Rubber gloves are not the best idea as they pick up oils and perish over a 6 month period. I also included a grden spray gun to rinse off part's but hardly ever use it as it is to tempting and you end up with to much water in the main tank. In the base of the barrel I drilled a grid pattern of holes to let water and glass beads drain out and stop my parts falling out. I did heat that area of the barrel with a hot air gun to form a bit of a natural run off. The problem with plastic barrels is that they are not really very rigid and tend to sump over time. I did have to add two pieces of angle iron under the barrel to support it along its length. Even so the slump means that there are dead area's and glass beads quickly build up, so have to be sprayed back in to circulation periodical. The entrance to the barrel for parts is via on of the twist on plastic lid's. This tended to be problematic as the glass beads made it difficult to unscrew and the thread leaked, so I siliconed sealed it in place and cut a square opening in the cover and added a hinged perspex flap, now I can feed items in and out with ease. Even if the flap does not seal properly the contents don't really get out as they are deflected by the inwardly opening flap.
In my hast to get the system running I rummaged through my parts boxes and found a suitable housing being a water pressure relief valve which I stripped down and added a ceramic nozzle from a MIG welder. I intended to fabricate something fancy out of aluminium, but this has worked well and stuck.
I inserted an outdoor light through a hole in the side, nd wired everything up with circuit breakers in a small electrical enclosure. I still want to add a foot activated switch to switch the air on and off, and a timer to switch the pump off if there is no activity for say 5 minuted.
In the air feed I have a solenoid valve, so air is only allowed to flow when the pump comes on, this is really to save on air. it is important for air to be flowing when the pump comes on as if not slurry gets feed up your air hoses and air regulators and solenoids stop working within seconds! To prevent this I have installed a ball valve in the air pipe on the nozel so any slurry will just force the ball closed and shut the air line off.
I have also fitted an air regulator directly on the unit so I can adjust the finish level, but mostly just leave it at 2.5bar.
I know I have oversimplified the process, so ask if more detail is required.
The main stuff to get right is:
a) Continuous agitation of slurry
b) Mixing of slurry and air in the mixing nozle
The rest you can do any old how.
I still want to ass:
a) Better electrical foot operated control of the pump and air.
b) A way to skim the crud off the surface as a continuous operation and pump the spill over water back to the washing nozzle
c) Some for of silicone rupper gloves
d) possible a bent metal stainless steel case so drainage is better controlled
e) A better wiper sustem