Thursday, 29 November 2012

Creepy but amazing

Theo Jansen's mechanical creatures are amazing and this one comes straight out of a 3D printer ready to "roll"

Wednesday, 12 September 2012

Really sucks

The dust shroud shown in the previous post works really well but only if you have suction and can keep it. Last summer I pimped my shop vac with a cyclone because it would clog in seconds especially when doing wood work. Thought I should actually show it:

Cyclone vacuum systems seem a bit mysterious but are really not. First how do vacuums work? Well they move air with an impeller, speeding it up and creating a region of low pressure. Atmospheric pressure (the pressure caused by having a sky full of air above us) then pushes air into that region. So the impeller creates an air flow. This picks up dust simply because the dust becomes entrained in the flow of air. So in my shop vac the bag is in a chamber from which the air is sucked, this creates a flow of air through the nozzle and through the bag and out of this chamber. The bag acts as a filter. The problem is that it fills quickly and soon becomes clogged as fine particles get stuck in the pores.
A cyclone system uses the fact that the dust only moves within moving air. If you watch the video and understand the construction then air must flow from the tangential intake on the side of the cone to the vertical tube which ends about halfway down the cone. The high velocity of the air, the tangential inlet and the shape of the cone means the flow has to turn. Particles that are neutrally buoyant will follow the flow perfectly but anything with a bit of mass to it will tend not to turn and carry on straight, leaving the flow before hitting the cone's side and flowing down into the collection bin.  So most of the dirt ends up in the bucket rather than going up the tube into the vacuum. Actually as a side note, cyclones are used to extract neutrally buoyant bubbles from bubble generators for use in flow visualization, they use tiny 3mm or so bubbles full of helium, they follow the flow so well that even when streamed over a wing at high speed they do not hit the wing and pop, they will even go through fans etc. In those devices the bucket is just collecting soap solution from popped bubbles which are flung outwards.

dust to dust

I'm just trying to move in to the not so littlest workshop, to make more space I am moving a partition wall closer to the stairs it surrounds. This revealed bare concrete floor, the rest of the floor is epoxy coated but that also looked pretty shabby. So I got quotes for a new epoxy floor, ouch!  DIY it is then! Step one, remove all the old epoxy floor. I hired a diamond grinder, this got rid of the bulk without too much fuss and the dust extraction kept things pretty clean. But that left the details; the hire place did not have a small grinder so I started using my angle grinder, I bought a diamond grinding wheel which worked brilliantly but coated me and everything in dust within seconds, it even set the fire alarm off. So I had do do something about it. At 5 to midnight I went to Tescos and got everything I needed:

Friday, 24 August 2012

Cute Stirling engine kit

I had the great pleasure of building up a prototype kit of this cute little Stirling engine last weekend. Soon to be sold at It consists of laser cut parts that slot together with a little glue, the "boiler" consists of a travel sweet tin and the power piston is made from surgical glove which can be easily replaced when worn. It was extremely easy to put together except for perhaps the bending of the con-rods but Michael has designed a jig to make that much easier. I love the noise it makes and I think it certainly makes a tea light more interesting!

Wednesday, 22 August 2012

It's been a while and yet another new toy

I've not posted, mainly because I have not been very active and partly because my garage is now saturated with nice machines with insufficient room to move between them. I hope to have remedied that soon with the all new not so littlest workshop.

Here is my new purchase, a Zcorp 406. Basically the same as the 402 in many ways but it can also print in colour. Or rather it can't, of course it is not working! But it seems all the issues are in fluid flow and print heads, this I think I can handle.

The new machine (image from Ebay auction) on the right you can also see the little clean up station that came with it.

An example of the sort of output it can produce when working!

Friday, 13 July 2012

Hello world

I picked up a Denford Router 2600 pro on ebay a couple of days past, this is just something that was on one of the disks to check it works.

Monday, 9 July 2012

Superhydrophobic solution for urinals?

Another little thing I noticed when playing with my Teflon block was that I could get a stream of water to bounce off it. I'm thinking a patent for a urine guidance system to prevent splash back could be in the works ;)

Of course there may be some more serious applications but I can't think of any at the moment for the life of me.