Questions from someone just getting started

Just concentrating on the first section of the build right now. I’m sure I’ll have more questions
about the rest later. On the hourglass design, or many of the open hearth designs, why does the
cone of the top part of the reduction hourglass not extend to the outer edge of the inside diameter
so that bridging does not happen in that voided area - as pieces will inevitably get stuck there.
Is it intended that this will eventually fill up with unburnt fuel or charcoal? Is there a downside to
extending the cone as I described and filling this area with insulation, and maybe running the air intake
lines through this area for preheating?

Is preheating the air one of the most important steps?, because I have other ideas about how to really
insure that I get a good preheat. Back on my earlier question, why are not all of the areas like the reaction
and reduction zones super insulated to make sure the burn temps are as high as they can be? I know
this will make it harder in the next step to cool the gases off, but…? Is it a matter of once you reach
a certain threshold temp, that all the advantages are satisfied, and there is no more to gain?

Also, on moisture collection, I’ve seen many models that have a condensation catch ring near the top of
the hopper. Would there be an advantage to putting a further removable restriction here, to narrow up the
diameter, and maybe catch more condensation?

Thanks very much!

Welcome to the DOW PaulB.
People will be better able to answer your questions if can explain out what your intended wood fuel prep wiliness is and even it’s general species.
Big difference between a dedicated pellet fuel gasifier, a sawdust fueled gasifier, a screened chipped fueled gasifer or a chunked wood gasifer.
Fellows here doing all of these fuel types for small engines, medium engines and large engines.
So that leads to what engine power size you want to fuel and for what purpose stationary? or vehicle?

Here I’ll show you with my own example.
I am stationary power with a V-twin engine welder gnerator with my own fuelwood trees living in a very wet temperate rain forest climate. I will only chunk wood prepare my own on-site raw wet conifer woods.
Now with some of your questions applied to me. I no longer use an hourglass direct hot char contact hearth. I now use an overlarge ID bottom flat plate restriction unit and allow the ash and char to build up to the air nozzle ring in a natural forming slope. My heat size shrinking soft wood chunks will flow down nicely moving down along this slope. The ash will form a self regenerating heat and metals erosion conserving insulator.
Now I know from expreince if I was using chipped fuels the particles will hang up too badly and not flow along the ash slope well for cinsumed replenishment without a lot of shaking encouragement. Tricky. Not enough shake - no material flow. Too much; and collape the ash slope clogging the whole unit. With chipped fuels then SOME, not all, do use a slick smooth surface - your hourglass: Richard “Pepe”, DJ and MattR. Yes. Left top open to back gap fill with ash as the char carbons would consume away leavingthe excellant ash behind. OTHERS handle chips and pellets in comptely different ways - ArvidO very active on the Small Engine Users Corner section of this site. Jim Mason with auger dribble in feeding. Sawdust fueled a whole different beast entirely and I’d be asking DougB.
Pellets and dried chipped fuel, and even kept dry shipping pallet or cabinet shop kiln dried chunks then hopper condesate measures are really not all that nessary. My rainforest wet raw wood I’ve learned with my small system I do not have enough gasifier system excess heat to run a condensing hopper well and then need a constanly powered air blower condenser fan. So as a stationary with lots of space and no weight restictions I can go first off gasifer system using engine wastes heats and do fuelwood drying with a combo of engine blown hot air and naural rising engine heats, And then extraordinary hopper moisture measures are not nessary for me.
Vehicle mobile gasifers, with space and weight limits, have MUCH larger heat souces and well able to operate condensing hoppers and have condernet travel air flow for “free”. Thses the ones with raw forest woods as base fuels going for all of in gasifier system fuel moisture removal measures they can incorporate. This is much better for found traveling “opportunity” wood fuels - usually going to be wet 9 months of the year.

See. The Depends, Depends, Depends are all on you man.

Steve Unruh

A few rules of thumb…

  • more heat in the char bed is better. Metal heat tolerance will be the limiting factor here.

  • more preheating is better. Any BTUs captured will increase the efficiency and improve gasification. Again there’s practical limits.

  • ash/char makes great hi-temp insulation. Good designs often depend on it. Flat plate and inverted V both use it for shaping the hearth area.

  • in general, better to condense water before gasification than after. Water is “a real damper” on a fire. :slight_smile:

As Steve said, the specifics very much depend on your design and use case. What did you have in mind?

Good morning Paul , Welcome aboard .

Agree with all Mr. Steve and Chris has said.

I think we all can agree the hotter the burn, the more recycling of the heat and the more the moisture is removed from the fuel is all good.

The problem is where does the point of diminishing returns catch up with us. This will be unique to each builder and application because each builder will have different availability of building materials , fuel quantity and quality, building skills , time etc,etc.

I think in my situation I may have reached the point where the fuel is cheaper than the time and effort to get more efficiency from the system.

As Steve says ,depends , depends . All cases will be different.

Wow, thanks for the quick responses. Here is the deal, I want the initial build to be large enough for
a stationary motor, either a twin cylinder 650CC Kaw motorcycle motor, or a 1500cc volkswagen motor,
(probably the bike motor) I think the bike motor is rated at about 30 HP, and the VW probably about 70. But, realistically I will probably mainly be using it for an 8HP generator at a remote worksite. (Eventually, I intend to do a system sized for a truck, and that is what I have actually been collecting materials for, but that is down the line). As far as the medium, I have about 50 acres of mixed wood, a lot of oak, pine, hickory, locust and hedge. I will be just rough cutting with a chainsaw or machete at first, and incorporate a rear axle/wheel rim chunker later on. While I like this kind of rough fabrication - have done it all my adult life, I don’t really want to have to redo it any more than I have to…so that’s why I’m here, to try to get some of this stuff worked out ahead of time, a kind of standing on the shoulders of giants type of thing. So, back to the questions. I know that there will be a downside to sizing the first one larger than what it will typically be used for, but, is that a huge problem? I have welders and torches, and am by trade a draftsman/designer, so I can work out all my designs virtually in 3D, and animate them - I can do that for you guys as well, if you have some radical new invention. But, most of the builds I have seen are using way too many airtight welds than I am comfortable with. I’ll wind up making just as many welds with my design, but I want to run as much internally as I can, to avoid leaks and aid in preheat, and to make the hearth and reaction zone modular, so I can change it out if I’m not satisfied with some aspect, or want to try something new, without having to do a whole new build. Also, since there is so much variation with diameters of found materials, which is essentially all I will be using, except maybe for the reaction zone tube liner. If I am successful with using a liner, then I, or others, can duplicate the design easily, without caring that much if the I.D. of their shells are 9" or 10", since I know as soon as I get one build, at least one of my neighbors is similarly inclined to build one of their own. Maybe I will try to get some drawings together to show my build concept, and you guys can critique it - kind of like a virtual workshop. Haven’t looked into what kind of attachments can be posted, or if there is a place on this board that these kinds of things are supposed to go. I should be able to export an .avi or similar. But, back to the questions. If I read the one response right, the kind of medium that I will be using will be best served by the hourglass shape - Is that the general consensus? Because, I am not adverse to the reduction style used by “Mr. Teslonian”, in his youtube Chevy Luv truck build, with just an overlapped smaller hole every time he reduced to another “tube”. In either case, it has been my intent to completely insulate around the whole reaction zone and reduction zone, probably even with refractory cement, depending on how that load is supported above. Maybe it will be best to just get some drawings togther. That probably won’t be till next week sometime, though. Anyway, thanks very, very much for all the help. Oh, one other quick question, is there a value in making the outer core fairly small to help the reactor maintain heat better, and create more turbulence? Also, should I make an effort in the outer core, with spiral shaped baffles, to direct the swirl the way I want it to go?

Also, looking forward, I live in Kansas. Are there any workshops or people on this board in the NE KS area? When I was younger, I noticed that for many of the larger highways and freeways in KS listed all the kinds of vehicles that were prohibited, like horse or animal driven, and one of the prohibited vehicles was those powered by wood. I always thought that was curious - back then I thought “How are they driving cars on wood?” ha ha. Does anybody know if they are still illegal to be driven on major highways in KS? Thanks.

Hello Paul ,

I have driven through Kansas a couple of times . No one noticed or said anything to me but there were certain times I’m sure the law would have been upset with me . See below .

Excellent article, Wayne.

Ok, I’ve just got too many questions to keep quiet - I know I will wear out my welcome shortly at this pace,
if I haven’t already, but for a modular design it would certainly be easier to have one large central air
intake, then a manifold to distribute the air to multiple passages. I had been trying to avoid this, because
I was of the mindset that this would not get equal distribution to all the ports. Hopefully, someone can
contradict me on this. I know manifolds are a super-common way of accomplishing this, so I don’t know why I’m hung up on it, but is there something I should know about how to build one to ensure even distribution, or will the normal suction be enough. (I’m sure someone can quote the physical principle that describes this effect, and assure me one way or the other). I assume the runners all have to be of the same length, but some bends might be more restrictive than others…The reason I would like to a central intake is that I want it to be able to be dissasembled easily, and I could use the flanges and asbestos ring that is common on the exhaust header on automotive applications. This is usually a 3-bolt arrangement that seals very well, and will withstand the heat. Has anyone tried this already? Thanks.

Good Morning PaulB
I suffer from this racing mind stuff also - very distracting - and set me back a good 18 months for practical engine fueling gasification.

Ok now with your basic goals, conditions and needs lined out here are some of the info mines to start digging into to settle in that mind for some real work.
Instead of giving you dumbing down fed direct links my bread crumb trails will teach you this sites info fishing capabilities better.
Member Dutch John here also a mind racer; lives in country with an actual history of woodgasification use, engineering and scientific publications, some old Museum’ed examples and even some remaining oldtimer operators to talk too. He’s a degreed professional an DOer/DIY par excellence’, a reader with a “yard high” stack of woodgasification books acquired and bought. After a vehicle bumper mounted system, three different working small engine systems, and now a BIG 454 V-8 Chevy truck systems ALL with mostly his own “better” design ideas; his direct advice here to DOW newbies is on your first to build strictly from a known proven design to be your first woodgas/operator trainer system. Still digging back for that link statement.
He DOES NOT use direct slick metals char contact on the larger systems. DOES use direct slick metals or ceramic on the small. Read and study it all. In words and pictures focus on what woodgas WANTS to be. Keys: condensates, tars, soots and ash. He and I joke with each other how many of our “better” early and even experienced later ideas have Flopped and had to be cut off and abandoned.
Been decades of very, very smart Degree’d, professional fabricators, professional welders fellows doing this thousands of differnt ways and what proves out workable aways gets the early ideas bells and whistles removed and KISSed down to practical to handle those real factors above. AND do this for hundreds, thousands of hours at metals killing, refractory eroding and ceramics melting tempertures and gases turbulances.

For your easiest to build with the least amounts of “gas tight welds” “using common tank stuctures” able to use your mixed species fuel woods in a chunked form you simply cannot beat a Stigg Eric Werner “tanks” build. Internet search his name with woodgas. Long links train to his site, and then on his site a bit of a circular rabbit trail to his “My Canadian Project”. Step by step worded and pictures build-up complety to running engine/gnerating with EVERYTHING shown from engine mixer, hearth/hopper to very proven, practical cooling and filtration.
This has moderate internal pre-heating and excellant evolved safety features with basic operator instructions.
Self-collects and uses ash insulations and metals protections.
NO wood fuel moisture removal features.
A solid weld up system - so cut apart for repairs and modifications.
This one IS based on systems WITH the excellent condensation recovery and disassembly features of the Sweedish Government SMP/Volvo system - but now designed to be made with a stick welder, cutting torch and an angle grinder/cutter.

It’s adding these other “advanced” capbilties where your designing for doable fabbing will get skill level and material expense hard real quickly.

For your engines use and selection look here on this site:
Curser over and click open the actual “Forum” tab. This will show you your memberships level of available sub-forums.
Click open the “Small Engine Users Corner”
Read the actual woodgas engine users topics.
Your 650 Kawasaki will be OK for your woodgassed 5 hp offgrid electrical generaton IF you run it at its lower camshaft/valve determined min 3000 RPM torque band speed. Woodgas can be ran at higher RPM but then a PITA for continuous loaded power stabilty control. 2000-2500 loaded RPM much better for the woodgas fuel characteristics. This engine will not like that low of RPM loaded and will overheat. You’ll have to add a power driven cooling fan as is. Monitor and watch you engine oil telmeratures on any down adjusted air cooled engine.
Your first woodgased fueled engine YOU WILL MUCK UP with tars learning woodgas and need repair or replacement. Only use for your first engine an easy cheap to repair one; or a walk-a-way engine. Sacrificing an engine will save you one year of getting in service develpoment time versus the “perfect flare gas” l-o-n-g step by step way. Run up the woodgas fueled engine operating hours then you will learn about soots!

Being in Kansas your very best leg-up would be to hook up at one of Doug Brethower’s Missouri woodgas do’s.
Then you can hear a for real engine powering. See, smell, feel ahd even taste those tars, soots, ashes, temperatures and heats.
MUCH more to learn from a thousand hour operator than a youtube minmal hours, one climate, one fuel operator.( I am being very polite.)
This will save you a whole year of failed ideas right here. It did me.

Steve Unruh

Steve - great comments and advice. I will chase down all of those leads. And you are totally correct, I spend way too much time planning and re-imagining and not enough time doing. There is a quote that I recently picked up, actually in another similar type of search…“The enemy of a good plan is the dream of a perfect plan” (Von Clausewitz). That, unfortunately, describes me to a tee.

Good. Good. We over thinkers have to stick togather.
Your engine exhaust dougnut idea is valid and some use this especially with “make’er out of old vehicles”. Better than even the hotrod three bolt flange gasketed joint with the dounut type able to align rigid piping. BIG water/gas pipe unions are in the good, being used catagory also is you can take the price and weight. (hint: drill and safety wire the nut which “loves” to shake loose with small engines vibertaton!)
Exhaust SS sleeve overbanding clamping type have been used - sometimes difficult resealing after disassembly without a new unmarked band.
The Best are probably the actual metal to metal exhaust union systems with no dounut or gasket to burn or erode out.
WayneK and now a few others using 2-3 bolt drawn tight balled pipe in expanded pipe metal to metal types.
Chris Seymour (memeber here) on his commercial systems pictures using the machined V-band clamped type.