the arguments are right, i am away now for trying original compression because of lazyness to prepare a new spacer ring under the cylinder…but i will try the 2 remaining spacer rings together…
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There is only one more property of gases that we need to mention, and that is the change in volume in relation to temperature. Let me give you an example: if we feed a mixture with a temperature of 50°C into the engine and compare it with the amount of the same mixture with a temperature of 20°C, there is a difference of almost 10%, similar to the engine working in a vacuum of 0.9 bar.
I will give you another example that would be useful for explaining the operation of the gasifier:
if we feed air with a temperature of 20°C into the gasifier and compare it with air heated to 520°C, the volume of the latter increases by 2.7 times
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So… running woodgas in an engine with a 21:1 cr would indicate that the gas was biased to an even higher ignition temperature or…? Water plus CO2 raising the auto ignition temperature.
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It would be appreciated if you would show your welding set up. I have read about it but have not seen it. 
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Giorgio, warn me if I’m too intrusive in your topic…
I forgot to add earlier that preventing “dangerous” temperatures from being reached when compressing gases in an engine is not the same whether the engine is absorbing gas under vacuum or gas heated to a higher temperature, even though the mass quantity is the same, because in the second case we are compressing already preheated gas that reaches higher temperatures…
If I touch on the second example, “preheating air for the gasifier”, where we see that hot air has almost 3 times the volume and 3 times the density, this means that the speed of this air must be 3 times higher at the nozzle to supply the same amount of air to the gasifier, as in the case of supplying cold air. This characteristic, however, does not mean that we need a much larger nozzle diameter if we want to maintain the same pressure difference at the nozzles, because hot air also has a relatively better viscosity.
Now when we look at what happens when such heated, relatively rare and fast air enters the hot area with charcoal, we can imagine that it brings with it a high temperature, so it is not necessary to burn the fuel so intensively to maintain the conditions for conversions, the high speed and better viscosity allow oxygen to penetrate further into the charcoal, thus removing the intensive oxidation and high temperature away from the nozzle, I also imagine that when using multiple nozzles and the WK hearth shape, there would not be as many problems with clinker as in the case with one nozzle.
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A little off- topic but I’m wondering if anyone has torn down a engine that was run exclusively on wood gas. I have worked in factories that run their equipment, fork lifts ect, on propane and I have seen them torn down. They look like new inside unlike any gasoline engine. I’m wondering if wood gas would be about the same.
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professor doctor tone explains…i, and i think all active members of us are grateful about your posts, tone, you have always arguments for practical and interessant work…
tom, i think that depends of the quality of filtering…on our motors (running on chargas) till now i have not seen corrosion from alluminium in the combustion chamber…
for complete fun in the school i must learn also latin…!!! too much languages in europe…
bruce, i use 3 batteries , each 110 ah, truck or tractor type, connected for welding to 36 volt.
for charging connected to 12 volts, charged with photovoltaik…
for regulation there is a long iron wire, wounded around a stone like a big brick , as resistance, but this is not enough, at the end of the wire is a spring formed resistance of a electric baker oven, this is very effective, i use from 5 to 10 windings…i posted some fotos in tools tips and tricks somewhere, but who can find it again?
5 years ago in this time we began with gasifying…looking for scrap pieces, propane tanks, a lot of round pieces and so on…i remember a pile of pieces and the question how to fix them together in a successful way…the result, with some modifications after a while, was our stationary unit…
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Is this what you are looking for?
I’ve got to say that is quite an ingenious setup. Perfect for off grid welding. How long would you say those batteries would last on one charge?
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when the batteries are more or less new, i can weld 25 to 30 elektrodes 1,6mm without bringing the batteries in a critical discharge…when the batteries are old, 5 years about, i can only weld 4 to 5 elektrodes , than the current is weak.
generally when i feel the current becomes weak, welds not so good more, it is time to recharge the batteries…
thanks bronlin for refinding this post for bruce
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new engine has a lda100 motor
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today we removed the front sheet of the motor for reaching to the motorhead …found this is a lda 100 lombardini…
the motor from the motoretta is a 4 ld 705 with a compression ratio from 17 : 1…
now i looked for data for the lda100 and found ( artifical intelligence based) 20: 1…
i am not shure if this is true…has someone a relieable data sheet…
bore and stroke and ccm is the same…
maybee the pistons combustion chamber is smaller??
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Tone, Giorgio,
I believe it is possible that you are both correct. The original equipment distributor / manufacturer may have requested a different compression ratio depending on the intended market area destination, and contract orders, depending on need and localized fuel availability. Or I may be wrong! 
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i am really not shure about compression ratio…we opened the motorhead, first there was no gasket …( maybee forgotten in the manufactory or tuning from a mechanican?) the other motor has a ring copper gasket there.
combustion chamber in the piston has approximately 30 ccm…4,3 diameter and 2, 1 cm deep…
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two paper thin brass cylinder foot spacers only…
the other motor has had a thicker spacer there…he is claimed with 18 hp…(4ld 705) cr: 17 :1
sometimes i read in internet market place motor lda 100 with 18,5 hp…
so i am really not shure that my lda 100 has the same cr (17:1) as my 4ld 705…
also why lombardini would use a different motor identification if it is the same motor
will be difficult to calculate spacers for lowering compression without knowing real cr…
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now i looked in the papers, lda 100 has no motorhead gasket, only iron on aluminium…
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maybee, originally they have built the motor with cr 20:1, than comes out this was not ideal for some reasons,( material stress?) and with a thicker cylinder foot ring and a copper ring gasket the motor was reduced to 17: 1…and was called than 4 ld 705…
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Now you can easily measure the volume of the compression chamber, assemble the cylinder, piston and cylinder head, you can use grease for sealing. Pour water inside and you have an accurate figure for the size of the compression chamber, if CR is 1:17 the volume is 44 cc, if CR is 1:20 the volume is 37 cc. This difference is made by a 0.9 mm gasket, well, if you want CR 1:13, you need a 3 mm thick gasket.
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Doing your assembled volume measurement use a light oil instead of water. The residue film left will protect the metals. And you will have less leakage past the piston rings.
Tilt the whole engine to have the open injector hole up; at the highest point. Bang on the engine assembly with a length of wood to shake loose any air bubbles.
S.U.
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I put a pressure gauge on the assembled engine and crank it over and get the compression pressure. Just divide that number by the atmospheric pressure and there is your static compression ratio. For gas engines, block open the throttle valve.
Compression ratio is irrelevant. Compression pressure and combustion pressure is what matters.
Tone kinda hinted around at the most important thing, flame speed. Too much hydrogen, and the flame speed goes up and creates a pressure wave that destroys engine parts.
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