Monday, 17 March 2014

Experimental Swift brick

by Dick

In publicising this idea, it is in the spirit of encouraging people to do experiments, rather than an idea that should be rolled out extensively, not yet anyway. The idea came out of the success of the air brick liner Swift bricks at St Neots. 

Swift brick with 2 fostered Swifts. Photo Judith Wakelam
The air brick liner Swift brick has internal dimensions: width 175mm x length 200 x height 100mm.

It thus occupies a space of length 1 brick and height 2 courses of brick. We wondered about a brick of height 1 brick - would this be acceptable to Swifts?

So, we built some prototypes out of 5mm thick fibre cement board. These have internal dimensions: width 150mm x length 225mm x height 75mm.

Swift exploring a Swift brick. Photo Clarke Brunt
In 2013, we installed 6 of these on 3 houses, all of whom were playing attraction calls. We managed to get Swifts to enter 2 of the boxes at one site, and we had them clinging to the boxes at a second site.

For the experiments, we have not knocked bricks out of any walls yet, but we have installed them under eaves with a simple wooden harness.

The width of these boxes could extend across the cavity, which, in modern houses, may be as much as 100mm, allowing a box width of 200mm. Also the length could be extended to 1.5 bricks ~330mm long. This would fit well in a Flemish bond.

4 fostered Swift chicks in a Swift brick
If this idea works, it would be the easiest thing to retro-fit into a wall, and may provide least resistance in the housing trade to install many of them in new build. We feel it could be a game changer.

For anyone who would like to have a go at this, please get in touch.

Saturday, 15 March 2014

Nest concave tool

by Dick

We previously advocated soft fibre-board for making nest concaves, here. Up until now, we have made these by gluing together two layers of fibre-board to make a blank 25mm thick, then scooping out the concave on a lathe. Here we have a better idea.

The tool mounted above a blank, and the tool in action, right.
The cutting edges are bevelled at 30°

A friend of mine has made a tool to be used in a pillar drill. Setting the pillar drill to its slowest speed, 210 rpm, it does a nice job of very quickly excavating the concave, without creating clouds of carcinogenic dust.

The material of the blade is 3mm gauge plate.

It takes less than a minute to scoop out each concave.

Note: the diameter 100mm is intended for cutting material 25.4mm (1 inch) thick. For other thicknesses, assuming 2mm is left at the bottom, the diameters would be as in this table. A larger diameter means a shallower concave: