This years Rocket Stove developements

[Graham Orm]

Hahaha, no, I was rushing to find a commercial rocket stove for Bugbear, and came across this and took the name a bit too literally, Bugbear rightly pointed it out, so I swiftly edited it with a 'Homer' mate.
Have you checked out the Youtube link I posted earlier ? Geoff Lawton has a few useful applied examples.

Yes I glanced, misleading then, using the 'Rocket' word in the name. That'll lead to some 'heated discussions' after purchase. Pun intended.

 

[bugbear]

Hahaha, no, I was rushing to find a commercial rocket stove for Bugbear, and came across this and took the name a bit too literally, Bugbear rightly pointed it out, so I swiftly edited it with a 'Homer' mate.
Have you checked out the Youtube link I posted earlier ? Geoff Lawton has a few useful applied examples.

Yes I glanced, misleading then, using the 'Rocket' word in the name. That'll lead to some 'heated discussions' after purchase. Pun intended.

The designer does claim some similar burning behaviour in his combustion design, although it's not identical.

I emailed him to check.

BugBear

 

[Graham Orm]

Should be interesting. The stove needs a 4" rocket tube at least 2'6" long inside to burn the gases.

 

[MIGNAL]

I've heard some 'rockets' claim much less than half the amount of wood burnt over that of a conventional stove. That's a stove with the inclusion of the thermal mass. Quite a claim.

 

[Graham Orm]

I've heard some 'rockets' claim much less than half the amount of wood burnt over that of a conventional stove. That's a stove with the inclusion of the thermal mass. Quite a claim.

It's a fact. They give an incredible amount of heat from a tiny amount of fuel.

 

[Jacob]

I've heard some 'rockets' claim much less than half the amount of wood burnt over that of a conventional stove. That's a stove with the inclusion of the thermal mass. Quite a claim.

It's a fact. They give an incredible amount of heat from a tiny amount of fuel.

Rocket stove, batch burner, gasification high tech stove and other variations - the whole idea is efficient max heat output per unit of fuel is from a fast hot burn. Inevitably this means fast frequent re-fuelling, or intermittent fast burning (a.k.a batch burning) but with heat storage for a steady supply.
Went into this in detail with our building project but decided it wasn't practical. Settled on a gas combi boiler plus a multi fuel stove space heater.
It'd work in a small workshop however like Grayorms as long as you can keep refuelling - perfect for a busy woodworker with loads of dry offcuts.

A compromise is to have a small wood stove but run it hot.

 

[MIGNAL]

This one is commercial, but note that he states it is for outdoor use only. Presumably because it hasn't got the necessary approval for use within the home. It looks a lot more attractive than some of the other homemade affairs.
Like the painted leaf pattern. May need redoing after a few weeks!


https://www.youtube.com/watch?v=ebGSAw2UKz0

I have a small 4.5Kw Charnwood. I think I go through around 4 - 5 cu. ft. per day - softwood burning around 10 hours per day. Not that I'm complaining, courtesy of a few builders I've had a whole years free burn. I've just received my first years energy bill and that free wood has paid for the price of the stove! Just the liner and installation to pay for now.

 

[houtslager]

as a semi green warrior I've made a few of the RMH stoves, and can testify that depending on the size [ 4, 6, 8 or 10 inch ] they can be damn good heat source for a home or workshop. The larger the diameter means a larger burning area therefore more wood required - I am currently using a 6"in my home in Germany, and will be building a 125mm diameter system in either [ or maybe both ] workshops - Amsterdam / Chippy

Go to the dreaded FB for loads more info or youtube and search for RMH

 

[Graham Orm]

I've heard some 'rockets' claim much less than half the amount of wood burnt over that of a conventional stove. That's a stove with the inclusion of the thermal mass. Quite a claim.

It's a fact. They give an incredible amount of heat from a tiny amount of fuel.

Rocket stove, batch burner, gasification high tech stove and other variations - the whole idea is efficient max heat output per unit of fuel is from a fast hot burn. Inevitably this means fast frequent re-fuelling, or intermittent fast burning (a.k.a batch burning) but with heat storage for a steady supply.
Went into this in detail with our building project but decided it wasn't practical. Settled on a gas combi boiler plus a multi fuel stove space heater.
It'd work in a small workshop however like Grayorms as long as you can keep refuelling - perfect for a busy woodworker with loads of dry offcuts.

A compromise is to have a small wood stove but run it hot.

For an entire evening in the shop Jacob, to try and put it into perspective, after the initial kindling to get it going, I would imagine I would go through a 4ft length of 3 x 2. I have a lot of 3 x 2 off cuts, this is why I use this comparison. They go in end on and only the end burns and the wood slides in as it disintegrates. It can be run at a lower temp once the rocket is up and running properly (about 10 mins). This is done by reducing the air intake.

According to the guy in Mignals video burning wood on an open fire only uses 8-10% of the potential fuel. A Rocket stove burns up to 95%.

 

[MIGNAL]

A 4 ft length of 3 x 2 would last not much more than 1 hour in my Charnwood, 1 1/2 hours at the very most and that's with the air intake set to medium burn. Perhaps 2 hours on low air intake, although at that setting it won't be pumping out much heat. They quote around 78% efficiency for the Charnwood, although I've heard it stated that these types of wood burners are a lot less than the quoted figures. Who knows. If Grayorm's rocket is anywhere near 4 Kw I think he is using around one third the amount of wood fuel that I'm using. Lot's of assumptions but an amazing difference if true.

 

[Jacob]

.....
A compromise is to have a small wood stove but run it hot.

For an entire evening in the shop Jacob, to try and put it into perspective, after the initial kindling to get it going, I would imagine I would go through a 4ft length of 3 x 2. I have a lot of 3 x 2 off cuts, this is why I use this comparison. They go in end on and only the end burns and the wood slides in as it disintegrates. It can be run at a lower temp once the rocket is up and running properly (about 10 mins). This is done by reducing the air intake.

According to the guy in Mignals video burning wood on an open fire only uses 8-10% of the potential fuel. A Rocket stove burns up to 95%.

Sounds good.
We were looking at this stove here which is the same idea but at the other end of the scale i.e. for central heating a large building but utilising the fast efficient burn idea. Too expensive for us - huge tanks involved, concrete footings etc.
So we are having a simple multi fuel for the big rooms. On the small size according to heat calcs, the idea being to run it hot, with extra heat from a long flue pipe

 

[bugbear]

A 4 ft length of 3 x 2 would last not much more than 1 hour in my Charnwood, 1 1/2 hours at the very most and that's with the air intake set to medium burn. Perhaps 2 hours on low air intake, although at that setting it won't be pumping out much heat. They quote around 78% efficiency for the Charnwood, although I've heard it stated that these types of wood burners are a lot less than the quoted figures. Who knows. If Grayorm's rocket is anywhere near 4 Kw I think he is using around one third the amount of wood fuel that I'm using. Lot's of assumptions but an amazing difference if true.

I worry (a little) about this. Measuring efficiency, especially when burning such a variable fuel as wood, is really rather tricky (or interesting, depending on your mind set )

I wonder how some of these claimed efficiency figures are being arrived at.

BugBear

 

[Graham Orm]

.....
A compromise is to have a small wood stove but run it hot.

For an entire evening in the shop Jacob, to try and put it into perspective, after the initial kindling to get it going, I would imagine I would go through a 4ft length of 3 x 2. I have a lot of 3 x 2 off cuts, this is why I use this comparison. They go in end on and only the end burns and the wood slides in as it disintegrates. It can be run at a lower temp once the rocket is up and running properly (about 10 mins). This is done by reducing the air intake.

According to the guy in Mignals video burning wood on an open fire only uses 8-10% of the potential fuel. A Rocket stove burns up to 95%.

Sounds good.
We were looking at this stove here which is the same idea but at the other end of the scale i.e. for central heating a large building but utilising the fast efficient burn idea. Too expensive for us - huge tanks involved, concrete footings etc.
So we are having a simple multi fuel for the big rooms. On the small size according to heat calcs, the idea being to run it hot, with extra heat from a long flue pipe

Also with a wood burning boiler you have to keep feeding it unless you make it a pellet feeder which takes up even more space.

 

[Graham Orm]

A 4 ft length of 3 x 2 would last not much more than 1 hour in my Charnwood, 1 1/2 hours at the very most and that's with the air intake set to medium burn. Perhaps 2 hours on low air intake, although at that setting it won't be pumping out much heat. They quote around 78% efficiency for the Charnwood, although I've heard it stated that these types of wood burners are a lot less than the quoted figures. Who knows. If Grayorm's rocket is anywhere near 4 Kw I think he is using around one third the amount of wood fuel that I'm using. Lot's of assumptions but an amazing difference if true.

I worry (a little) about this. Measuring efficiency, especially when burning such a variable fuel as wood, is really rather tricky (or interesting, depending on your mind set )

I wonder how some of these claimed efficiency figures are being arrived at.

BugBear

The guy in the video that Mignal posted claimed 1500 deg inside. That's almost double the highest reading I've ever seen. Mine and any other I've seen peak at around 800, even open topped with a thermometer probe suspended in the rocket tube. But then he is selling them!

 

[Benchwayze]

What does it matter which way a chimney exits a building, so long as passers-by can't burn themselves on the exhaust? Heat goes upwards dunnit? Or does this mean you can't put a cowl over the top of a vertical chimbley?
H&E gone mad with power again?

 

[bugbear]

A 4 ft length of 3 x 2 would last not much more than 1 hour in my Charnwood, 1 1/2 hours at the very most and that's with the air intake set to medium burn. Perhaps 2 hours on low air intake, although at that setting it won't be pumping out much heat. They quote around 78% efficiency for the Charnwood, although I've heard it stated that these types of wood burners are a lot less than the quoted figures. Who knows. If Grayorm's rocket is anywhere near 4 Kw I think he is using around one third the amount of wood fuel that I'm using. Lot's of assumptions but an amazing difference if true.

I worry (a little) about this. Measuring efficiency, especially when burning such a variable fuel as wood, is really rather tricky (or interesting, depending on your mind set )

I wonder how some of these claimed efficiency figures are being arrived at.

BugBear

The guy in the video that Mignal posted claimed 1500 deg inside. That's almost double the highest reading I've ever seen. Mine and any other I've seen peak at around 800, even open topped with a thermometer probe suspended in the rocket tube. But then he is selling them!

Yes, but that's just a temperature at a point in time. Impressive, in its way, but only very indirectly related to overall efficiency.

BugBear

 

[Jacob]

.....
Yes, but that's just a temperature at a point in time. Impressive, in its way, but only very indirectly related to overall efficiency.

BugBear

Higher temperature is very closely related to efficiency with wood burning. That's the whole point of the rocket et al.
It's also the problem as it would be convenient to burn slowly with steadier output and less frequent stoking but still have high efficiency, but this is not possible.

 

[bugbear]

Stove efficiency is simply the ratio of the amount of energy in the wood to the amount of energy delivered by the stove.

To measure efficiency you need to measure energy, not heat, and certainly not temperature.

BugBear

 

[defsdoor]

A stove delivers the energy in the form heat. What else can you measure ?

 

[Racers]

1500 degrees, dosen't steel melt at 1500 degrees?

Pete