built my first rocket over the last couple of days. got 70 red bricks from the local builders merchants and arranged them as in the book. was a bit confusing at first as it is not at all clear that you need 2 3/4 bricks to keep to correct dimensions. it is obvious once i worked that out. no clay slip or insulation yet so tested it just using the bare bricks. it has been running for around 1 1/2 hours so far and all seems well. been checking temps around the stove so i can work out how many fire bricks i need. looks like around 12 to 15 should do. around the burn chamber and the bottom of the riser i may replace the brick riser with a cast one once i get the perlite and fireclay. i wiil carry on with the brick riser for now and get some netting to wrap around it. has anyone used the fibreglass netting sold as fly screen to hold the perlite in?
Bob, for holding the insulation, a thin sheet of sheet metal is good enough, since it's not in the burning zone anymore, it can cope. Something like 24 gauge (0.6mm) is good enough. Tho i think it can cope being of the galvanised type. Since the flue gases of a rocket are damp and a smidge acidic iirc. But normal steel should last a while too, once soot has deposited on it. Or it's surface will have rusted.
just thought if i could use heavy duty cooking foil over chicken wire. that would solve the large hole problem with the chicken wire. it is only for a test anyway to see how the bricks hold up to the heat.
Location: Southern alps, on the French side of the french /italian border 5000ft elevation
Bob, forget about perlite for your test. Use some rockwool held directly by the chickenwire. Tho, if you can find fiberglass and make a sort of bag, i think it should hold against the heat for holding your perlite.
did a bit more work on my project today. carefully relaid all the bricks with clay slip between them. let that dry a bit and mixed up some cob. i found a seam of clay under a fallen tree so didn't have to dig down 3 feet to get to it. mixed it with more or less equal portions of sharp sand and stuck it all around the base of the RMH.
i put 6 courses of bricks on top of the burn chamber to test it and have started to dry out the cob. it will take a while as the cob was quite wet. it held onto the bricks ok but i think i made it too sloppy. i have a bucketful left to finish off areas that need a thicker layer. so far so good.
my rockwool has arrived as has the perlite. the plan is to experiment with the brick riser first and when it all seems to be working ok replace the brick riser with the cardboard tube cooking oil drum filled with perlite and clay slip, then get it really hot to burn out the cardboard and set the clay. does that sound like a good plan. i havent started on the flue or the large oil drum yet as i may move the whole thing before i do that.
will i be able to reuse the cob once it have dried out by just mixing it up again with some water.
A timing clock, fuse wire, high explosives and a tiny ad: