Peter van den Berg

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since May 27, 2012
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He's been a furniture maker, mold maker, composites specialist, quality inspector, master of boats. Roughly during the last 30 years he's been meddling with castable refractories and mass heaters. Built a dozen in different guises but never got it as far as to do it professionaly. He loves to try out new ideas, tested those by using a gas analizer.

Lived in The Hague, Netherlands all his life.
+52° 1' 47.40", +4° 22' 57.80"
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Recent posts by Peter van den Berg

Eric Marshall wrote:I guess I was talking about something like what this guy seems to have built. Is this just a stove door on a masonry firebox you think then? Or maybe he took an old wood stove and just lined the inside with masonry or ceramic and insulation so the metal wouldnt go molten on him and used that as his firebox.


This is a batch box design built by Adiel Shnior and  Shilo Kinarty in Israel. As far as I know they use custom doors for their builds.

What you ask for has been done before though, here's a video of a French conversion from wood stove to batchrocket.
You need to skip through the initial start, building a simple rocket cookstove and a demonstration model. Mark however, how everybody is convinced when seeing the double vortex forming.

2 weeks ago
Almost all rocket mass heaters are unwilling to run ferociously at first. Clean burning at the same time is relatively common, that white steam indicates there's a lot of water involved, either in the heater or in the fuel. Besides that, smoke coming out the p-channel and door is an indication of weak draft, probably caused by the core and bech not really dry yet.

On a more serious note, I spotted a couple of errors but I don't know if those are real problems.

The p-channel looks quite small for such a large system. Is the (internal) csa as large as 5% or more of system size?

You are using the Mallorca build layout, that one is tested in combination with a floor channel only. I honestly don't know whether or not this would lead to malfunction in combination with a p-channel. The drawing of the Mallorca build as well as the diagram in the Core Designs chapter clearly shows a floor channel, though.

Batch rockets aren't tested when combined with a piped bench. The 8" version at Paul Wheaton's is a notably exeption, although the coupled piped bench in that case is a pebble-style one, unlike yours.
3 weeks ago
Yes, it can be done like you suggest, Max. I updated the site a week ago with this article about riser simplification. All the other editions are on hold until Terry is ready with correcting the English side of it. Bar the Dutch version, but I have the gut feeling that one isn't useful to you.
1 month ago
You are welcome. Please keep passing it through, you'll never know whether or not I might kick the bucket in the forseeable future. The site is hosted and payed for by a third party.
1 month ago

Satamax Antone wrote:Well, carry on with your idea of covering it with normal concrete. But put a metal plate underneath. A piece of 2mm steel, the right length and width. You could even support the whole complex of metal and concrete with three crosswise T bars. Tho, remember, that theses should not be mortared in. and have expansion space lengthwise. Usually, you fit these in slots cut into the bricks, filled with a bit of superwool or rockwool.


Max, it isn't often that I feel I urge to contradict you, but this is one of those occasions. Benen is building an RMH with a steel bell and a bell bench as far as I am aware of. The chance that you'll be able to crank up the inside of such a bench up to over 400 ºC is fairly small, if not impossible. A steel plate under the bench top would expand much quicker than the pavers above it, so the bench would develop cracks for many years to come, over and over again. When you meant to say that the pavers should span the depth of the bench in one go, I agree.
1 month ago
The top of the bench doesn't need to be refractory concrete, in my own opinion.

The bench top of the Mallorca build was two layers of a very weak and thin cement/sand paver, meant as a cheap alternative for soft locally quarried slabs. In the Netherlands there are concrete sidewalk pavers of 60x40x5 cm. I know of several builds where two layers of that kind have been used. And a couple of others that have one layer of the said pavers and a top layer of sandstone slab, which looked fabulous to say the least.

Heat load put to these bench tops are within reasonable safety margins, estimated about 150 ºC at the inside. In 2009 I ran tests with a bell top made of those concrete pavers, inside temperature never went over 400 ºC. I have to add, the top gap of that bell was over a meter and the core was a smallish 13 cm J-tube. Benches are perfectly safe with a top like that, no problem I would say.
see https://donkey32.proboards.com/post/232/thread

Weight load of such a two-layer solution is far beyond the weight of human beings.
1 month ago
That top piece is meant for the bench, yes? In that case it would be better to do two layers, no rebar, seams overlapping and clay mortar in between. This way, it's much easier to make the thing gastight. Something along the lines of the Mallorca build, as shown in the video.
1 month ago
Good idea about incorporating the double bell requirements into the site, that will be next on my to-do list. At the moment I am busy to do a very belately rework of the Dutch version, most of the articles are about half as long as in its English counterpart.
1 month ago
Back in 2015 it was still a guess what could be used. Today, there is a lot more experience with sizing of bells so I can safely say yes. Remember though, those are maximum numbers so you need to ask yourself whether it's a good chimney you are going to use. When in doubt, 5% underspec'd won't hurt anyone.
1 month ago
There are some pieces added to the end of the Building, Designs and Applications chapters. In Building, a really simple way to calculate the Internal Surface Area is described. In Designs, a simplified riser build is pictured and in Applications some systems that are designed to run without doors or secondary air provision.
See for yourself: www.batchrocket.eu/en/
1 month ago