Posted by Curbie on December 15, 2009, 5:54 pm
Can you point me to a link for the math on those Archmedian screws???
I think especially on a home scale, using methane to run an engine for
motion, to generate electricity, to power a motor to then create more
motion for pump (or anything) is going to be a though rattle. It seems
to me that if process produces any real net energy at a home-scale the
commercial guys would already be doing it.
I'm look at using methane to run a properly sized engine for motion
drive all the process functions mechanically once per day. Keep in
mine I don't trust Jean Pain's claim of 1kg of bio-mass produces 1m^3
of gas, which seems way too high or the commercial guys would doing
this. Just another experiment.
The thing that about this idea that has appeal for me is the organic
compost and the potential of enough methane for cooking, and the
timing of the process is interesting; the timing seems to be dictated
by the digester temperature and carbon to nitrogen ratio which seems
Most literature on methane production of this nature is based on an
animal&vegetation-waste feed-stock, shooting for a 30 to 1 C/N ratio
(John Fry) for fast continuous digestion, Jean Pain on the other hand
uses a batch digester with a straight vegetation-waste feed-stock, for
a 60+ to 1 C/N ratio for slow gas production and using most of the gas
at low pressure without compressing it.
So the idea here is make several smaller digesters to spread-out gas
production through the late summer until spring, hopefully compressing
enough gas to perpetuate the process the following summer, along with
gas for cooking.
Once I visualize what the process needs, I should be to whip up some
experiments to get me the data to check viability (cost analysis) and
ONLY if viable, redesign for production. I have lots of time so, that
is all that I can lose by looking into this.
Posted by Jim Wilkins on December 15, 2009, 11:16 pm
This claims over 70% efficiency:
A homebrew one's efficiency would strongly depend on constriction
details. For instance the worm gear speed reducer I suggested could be
made without a machine shop but typically is less than 50% efficient.
The big advantage is that they don't need wetted seals or bearings,
which is also true for a bucket type paddle wheel.
I can't remember what dozens of people have written, do you have a
machine shop? I mostly read and post on rec.crafts.metalworking where
most participants have metal lathes, milling machines and welding
equipment, or want info on buying them. It's a real struggle to build
moving machinery without them.
Posted by Curbie on December 16, 2009, 12:56 am
Thanks, but believe your efficiency claims without the link, I was
looking for the math involved with designing a pump to deliver x
gallons, at x RPM, requiring x HP or the like. I notice that the angle
of inclination, center shaft/tube, and blade sizes are all different
in the pictures. I think I would need the math to sort out a proper
No, but know of on-line machine shops, and would rather find one near
by to where I move.
I did a lot of welding as a kid on race cars, I might spring for a
welder depending on needs, but am thinking any machining would best be
left to the experienced.
WOW!!!! Is that stuff in the gallery yours? The band saw is cool, but
the garden tractor would be exactly what I would want and the bucket
loader is fabulous! Did you build it?
Posted by Jim Wilkins on December 16, 2009, 5:04 am
Yep, I got the free, dead tractor running again and the loader
attachment is all home made, mostly on the cheap. The frame is 2"
square tubing, great material for welded projects. The $0 orange
hydraulic cylinders are used, leaky Porta-Power clones, the $0 pump
is a $00 gear motor someone had rebuilt improperly. This broach cut
the splines in the hub of the pulley to match those on the pump shaft:
That's a disadvantage of surplus equipment, it may be available
because it's difficult to use. The cylinders needed new seals in an
unavailable size so I installed ones with the correct cylinder
diameter and machined adapters to fit them to the piston. They still
The bucket is 16 ga stainless so salted snow and ice won't corrode it,
arc welded with 312 rod which is much faster than TIG for joints that
don't need to hold water. I designed it to lift 500 Lbs (the frame for
500 per side) but 200 raised 4 feet high is about all the little
tractor can reasonably manage. That's still a full bucket of wet snow,
but not much sand.
I took a semester of night school welding class first to learn to use
7018 rod, good to know although the mild steel tubing doesn't really
need it. The test was to weld two plate edges together and then bend
them over double along the weld line with a 50 ton press.
For the pump I think you could just figure the weight lifted, 1 HP =
550 lbs raised 1 foot in 1 second. You ought to be able to do half
that much. Or build one, measure the torque including friction, reduce
it enough that the motor can drive it. Pulleys are easy to swap.
I designed the sawmill transmission that way. The blade maker
suggested 5000 FPM, the engine (borrowed from my logsplitter) doesn't
vibrate too badly around 3000 RPM, the smallest chain sprocket I could
find had 12 teeth, I bought vee belt pulleys to match the speeds and
just push on the carriage until the motor slows down. I didn't know in
advance how fast it would cut.
The bandsaw transmission shafts are sized for 10 HP, 15 KSI max outer
fiber torque stress. Loader frame members could see 20 KSI, max pivot
pin projected load is ~2500 PSI, I grease them often. That pushes the
crush strength of oilite so they are drill rod pins in brass waterpipe
Posted by Curbie on December 16, 2009, 6:05 am
I will need a garden tractor and your looks great, roto-tilling,
moving & spreading compost and general yard work, rebuilding a lawn
tractor is one job I look forward to. So when I was conceptualizing
the raceway idea, one view I didn't really show was the cistern end.
Pile up snow on the cistern, a few extra snow piles, and in the
spring, fill the raceway and cistern from the snow melt.
Wood cut on that rig would seem to be too nice for firewood (scrapes
maybe), are you cutting stock for cabinet makers?