Probably to protect the walls from heat.
5 Likes
Well, it seems that it has to do with the size of the unit, the 300mm pipe has a diameter at the tip of the nozzles from 208 to 258mm.
Also see that they get worse gas and higher resistance in a unit that has too large a diameter on the restriction against the pipe diameter, and as usual I donât understand why.
Do you have any idea @Woodrunner Göran?
3 Likes
Hi Jan, please remind me what problem/ question was again, i have alot of things buzzing around in my head at the moment⊠(mostly/always) 
Having a hard time keeping up with threadsâŠ
5 Likes
If I have a hearth tube of 300mm, what will be the difference if I have a diameter of 270 or 230mm between the tips of the nozzles?
Why is there worse gas and greater resistance if I have a restriction of 125mm than one of 78mm in a core tube that is 300mm?
2 Likes
Oh, hard to say, i believe much can depend on the charbeds âcompactionâ? A big tube and small fuel sizing gives small char, and a very restricted charbed, this compacting is much due to all the fuels weight âstandingâ on the charbed, tube, restriction and grate all acts as shelves, carrying some of the weight.
Some observations from me: about the fifth version of my volvo gasifier my woodgas âmentorâ gave me a old, ww2 imbert heart that i built in (175mm hearth dia), the volvo ran fantastic, almost no vacuum pull, no problem running 130 km/h (wich is good for an old volvo 142) only problem: bridging, only possible to drive ca 2km then it stopped, on bumpy dirt roads it ran like a rally-car, but on paved roads, no, i had to drive on the roadside every 100 meter, to shake it, tried to solve it with stronger towing springs, rallye shock-absorbers, and even some very old winter-tires (hard as bakelite) it helped some, possible to run 3-4 km on smooth road before stopping.
When it really got tired of this i built my own hearth, exaggerating what could help these troubles, built from a rim, 420mm inner dia nozzle circle ca 300mm restriction 75mm and a very small reduction, straight pipe 175mm inner dia.
This never bridged, but ran constantly âconstipatedâ very high vacuum directly after gasifier, top speed 100km/h, but it always ran, always started fast and easy.
Very small char after restriction ca 5mm pieces, took some time to learn what wood size and type worked best in this one, straight pine and fir, vacuummeter hit the bottom, top speed 50 km/h.
Sorry for long post, i just thinks this can show some of the âextremesâ?
12 Likes
Very interesting Göran.
Do you remember how big nozzles and how many you had.
How big was the core tube, no problems with tar in it?
2 Likes
Hi Jan, if i remember, i had 8 nozzles, 9mm inside, (Biltema lÄnga tolvkantshylsor, 9mm)
9 mm, deep sockets, 1/2" fitting.
If you by core tube means the part of hearth with nozzles, over restriction? It was 420 mm.
Tube after restriction was only 175 mm.
3 Likes
Wonder when (if ) I will ever learn this, was going out to the lake again after lunch, opened the lid to poke a little
with the iron, and there was a small bang.
The wife stuck her head out and wondered what had happened, the windows on the balcony, where she sat reading, had shaken.
11 Likes
Haha! Jan, this is probably the hardest part to learn. Iâve noticed the best way is to stick the torch into the hopper before turning on the blowerâŠBUT⊠this morning going home from work I didnât. After running the blower for a little while I waved the torch around inside the hopper and it all seemed safe, but when the flame got sucked down through the char there was a huge bang and my forehead was sprayed with tary condensation. Not the most appealing eau de perfume 
(I had a shower 5 min earlier)
14 Likes
Yes, I know you have to fire the hopper first, but I think it burns for so long, hesitant to do it in a parking lot at a store.
Wasnât so popular though when there was a bang and my wife was standing by, she got black spots on her face and hair and smelled like tar all day
12 Likes
I donât recall ever having a bang when refueling. Only at lightup.
However, driving off in the dark after refueling, thereâs sometimes a flash visible in the rear-view mirror. Seems quite entertaining to traffic behind. Iâve had cars overtake me just to be able to give me a 
10 Likes
Hmm, I wonder what I should do then, itâs when refueling that it mostly pops.
6 Likes
Happened to me once when refuelingâthe sound ricocheting off of surrounding buildings. I expect I was the only one who knew what happened, and it happened fast. I was going to ignite the gas with my grill lighter after removing the lid, but never got the chance.
11 Likes
Does it matter that I have around 600f out of the cyclone?
Or is it just a good thing that I have such high heat, it should show that it is hot in the unit so that the reduction goes quickly?
3 Likes
To me it seems a little to high, especially after the cyclone? But every gasifier build have different working temperatures. You can ofcourse take some energy back, into primary air, or in wood drying.
On my chevy gasifier, with stabilized charbed, it reaches 200°c after 15 minutes driving, after an hour around 300°c, when it reaches over 400°c i have to stop and poke a little, it burns out the reduction charbed after longer highway driving.
For this longer fast drives im going to try Kristijan and Bobâs rocket fuel mix in the future, to see if it keeps the charbed filled good.
Edit: my volvo gasifier almost never reached over 100°c after the cyclones (double parallell)
6 Likes
I believe youâll also find less moisture in the monorator tank. Itâs a very good idea in practice.
4 Likes
@Woodrunner ,Goran.
Yes, maybe Iâll turn the heat down a bit, at the same time the car runs quite well now.
@ForbiddenTuna ,Cody,
It is possible that I get a little less water in the tank, but with the new system I still get a lot more water out than before.
2 Likes
Sorry for the confusion Jan, I was agreeing with Goran with the âRocket Fuelâ mix for highway driving in his Chevy.
3 Likes
I tested rocket fuel before, since then the engine light has been on, think something went wrong with the oxygen probe, (lamda)
2 Likes
WIth using the rocket fuel sometimes it is hard to even see a haze of smoke coming out if you wanted to flare it off on start ups.
Bob
2 Likes