Asbjoern Rohde

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since Jun 23, 2011
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Recent posts by Asbjoern Rohde

bottom of page shows some figures for exfoliated vermiculite
7 years ago
Thank you!

Figured the hugroscopic properties would be irrelevant when used as refractory insulation... but did not take into account the soakage from the clay slip.

Don't suppose anyone know the max temperature perlite and vermiculite can withstand?
7 years ago
Hey everyone!

I have tried to find this information on the internet for a while now, but even engineering and industry sites don't seem to display it. Thought I'd turn to you guys.

Among the goals of my future rocket stove is a really HOT clean burn. So my question is: Which insulation withstands the highest temperature and generally perform best in rocket stove? Exfoliated- Perlite or Vermiculite? They seem to perform rather equal with the exception being the hygroscopic properties.

Thank you!

/Asbjörn in Sweden
7 years ago
So for some more details:

Firstly go to this website. It is in swedish, but contains a lot of photographs. Also an improved version of the one in the video is featured. Also another type where a spring works with tensional force instead of compressive (as the suspension spring does).

Materials and dimensions are:

- The spring comes from a car suspension. It is 43 (~17 in) cm long unloaded, and 29 cm (~11½ in). The steel diameter is 13 mm (33/64 in) and the whole spring is 16 cm (6 19⁄64 in) diameter. The part of the spring that moves comprises 5 1/3 winds. Trial and error would make other springs work too.. The splitter that uses tension springs (pulling the spring) are easier as you can combine several springs.
The spring sits in place only by means of the weight on top of it and by the aid of small blocks welded as seen on this picture:

- The shaft on which the axe head and weights are welded used was from an old harrow and is a square (hollow) steel bar with the measurements 75x75x4 mm (2 61⁄64 x 2 61⁄64 x 5⁄32 in) and 128 cm (50 25⁄64 in) long from one end to where the axe and weights are welded onto it.

As you can see the shaft has been hightened approx 8 cm (3 5⁄32 in) at the hinch to leave more space for the spring.
The weights and axe head are quite long (62 cm or 24 13⁄32 in) , and the handle has been placed fairly high to avoid having it in the way of the splitting wood. Among other scrap steel, hydraulic arms from a tractor were used for weight and welding the axe head onto.
These weigh 38 kg (83.8 lbs) alltogether.

The Axe head and weights should be welded to the shaft with a bit of an angle towards the hinch in order to direct the force directly from above onto the firewood log. Otherwise the axe head will be pointing slightly towards the operator as it travels in a circular motion.

The tip of the axe should be hovering an inch or so above the firewood log you intend to split when resting on the spring. Otherwise you have to lift the axe to place a log on the chopping block. A tip is to keep the cleaving surfaces that come in contact with the wood clean from rust to limit friction. Keeping the axe sharp is also important as this allows for the axe to cut through knots etc. This is of course optional. It can also function with a round edge for minimal risk of cutting injuries. Height of the axe position can be adjusted by moving spring closer or further away from the hinch.

- For a handle you can pretty much choose whatever you think will work for you. Don't go too thin as this may be uncomfortable.

- The hinch needs to be very robust and the one used here is from an old 'grip' from a small forestry tractor.

Be creative and find some steel bars etc for the rest of the construction.

To give a rough idea of the remaining measurements I will comment on the following picture:

The long steel bar on which the hinch and lower spring platform are welded onto measures approximately 155 cm (61 1⁄32 in).
The lower components in the frame forming a 'V' measures: The right side pair: 95 cm (37 13⁄32 in) and the left side pair: approx 75 cm (29 17⁄32 in).
Distance between the 'legs' comprised of the 'v' frame is 100 cm (39 3⁄8 in).
Lower spring platform sits approx 92 cm (36 7⁄32 in) above ground/feet.
Distance between where the 'v' frame joins onto the longer steel bar is approx 115 cm (45 9⁄32 in).

The left side of the 'v' is cast/imbedded in a block of concrete. Alternative would be another frame construction, bolting it to a floor etc.

The sturdier it is, the safer and more precisely it is, too.
Here he is making kindling using this big contraption, showing it is versatile.

If you keep the hinch well greased it should function without making much noise allowing you to enjoy the birdsong or a trickle of water while splitting wood

7 years ago

I am based in Sweden, an hour north of Gothenburg. Hope you find some in norway!
7 years ago
Hello! This is my first real post on permies. Firstly I intend to present myself. You can of course skip this to go straight to firewood splitting!!
I have been self studying permaculture and stayed at permaculture farms for years now. Soon it is time for me to take on some land suffering from unsustainable practices and turn it into a permaculture oasis and eventually a demonstration center. I am based in mid/south Sweden at the west coast, and my dream is to start a permaculture research institute. I am 21 yr old and work as a carpenter and have done natural building, i.e. straw bale and cordwood.
For more than a year i volunteered and lived with natural builder Simon Dale (famous for his hobbit-like house in Wales), before taking on other projects. I love this forum and think it is crucial to the movement and a wonderful and inspirational place where people allow their imagination and ideas to be discussed. Also the behaviour is very social and pleasant compared to other forums, and i have respect for Paul who dedicate so much of his time on this.

Cheers everyone!

And now for something completely different, a man with... a scrap metal splitter!

This contraption would make it easy to split your firewood, if it is of a decent quality (grainwise). I think he is splitting alder which can hardly be the most sought after firewood. It is safe to operate because the axe head hits the same spot everytime and cannot move sideways. Also, it will never reach contact/impact with chopping block as the car-spring stops it at the right height making sure hands wont get crushed (unless between head and firewood - doh!). At least I reckon it could be adjusted so. Make sure you weld it well. The axe head weighs more than 38 kg!

Just thought i would share the concept.. maybe it has even been shared here already. What do I know. I have more detailed info on this if you are interested..
7 years ago
There are of course many green building books out there where you can read into straw bale or cordwood building used in a roundhouse construction.

Here's a roundhouse specific book:

By Tony Wrench, another guy in Wales.
9 years ago
In case you've seen Simon Dale's roundhouse(also known as the 'hobbit house') - he's a dear friend of mine and the one I volunteered for for half a year in Wales, before taking on my own project.
9 years ago
I'm new on the forum here. It looks great.
Permaculture is amazing and I also enjoy green building in particular.

I thought I'd share some roundhouse building with you that I did in SW Wales, UK.
All materials are locally sourced or salvaged second hand.
We mainly used handtools to minimize total embodied energy of the building. There were lots of volunteers and a great atmosphere.
Methods such as cordwood, straw bale, cob, roundwood timber framing, earth floor, dry stone walls etc etc were used.

Feel free to check out my albums(one by one from the top works the best (there are a few pictures that aren't really about the build)):

I also helped out on a project in Sweden, rebuilding a 140 year old log farm house, building a roundhouse, pizza oven, and digging a 5 metre deep well by hand - we also dumpsterdived a great deal for free food! (some pictures not related to the building):


Feel free to comment and ask questions

Asbjoern in Sweden.

Have a nice summer!

9 years ago