How to construct the internal wood measuring stick

[miniadventure]

Hi folks, I'm new to this, please bear with me.

I understand the principle of the wooden measuring gauge that everyone is using to line up the bricks in the dome, but how is it constructed and what principle measurements should it be, I presume one flat edge marks up the internal brick front and the top flat edge marks up the angle of the square brick stone, then the dome is symmetrical?

My what size and angle etc does it need to be set at?

I presume the same angle is used to create wooden wedges to wedge up the square fire bricks while mortating??

Any help or advice will be great.

That's simon

[chas]

Hi Simon and that bit of kit (a trammel) is made of two pieces of thin flat wood - doorstop is ok, can be even smaller stuff. It doesn't require setting at an angle, it 'finds' the angle for you:

get one piece the radius of your dome and another about 8 inches long. Overlap them so you can secure them with tape or short screws.

Now, if, say, you have one or two courses of vertical brickwork ring to spring your dome from, put one or two bricks in the middle of the ring and lay the trammel across from the centre point to the outside. The step formed by the joint will rest up against the inside top edge of the ring (being the radius) and the 'extension' will lay more or less flat over the top of the brick. In practise it helps to have a locating notch to rest against a screw set in the centre-point, and to make sure the brick(s) in the centre can't move - you want everything to be a constant.

As you swing the trammel around the circle of bricks, it neatly clips that top edge and of course lays flattish over the top.

When you set your first brick at an angle to start your 'igloo', the same measurements will apply: you're building a hemisphere. So, the step will locate in the top inside edge and the extension, raised up at an angle, will lay flat over the top - as you've guessed. If it doesn't, you'll need to increase or decrease the angle of the brick until it does, and all other bricks in that course will follow at the same angle. Cut wedges to suit that angle if you want.

Up and up you go... with wedges or not according to how fast you want to proceed, and what you're sticking your bricks together with.

Hope that helps, like a lot of things, it's easier to do than describe...

Chas