
The Mechanical Transmission of Power – Jerker Line Systems - youngerdryas
http://www.lowtechmagazine.com/2013/02/the-mechanical-transmission-of-power-jerker-line-systems.html
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mjb
That's very cool stuff, and a really clever solution to a highly constrained
problem. I'd really love to see one in action - and it looks like I could.

> Why do this instead of powering each device individually? One: you save
> three electric motors. Two: there is no need to provide batteries or
> electric outlets at any of the locations. Three: you can balance the system
> so that one device helps power the other, saving a considerable amount of
> energy.

Pairing rocking machines like this is a real efficiency improvement,
especially with IC and steam engines where you don't really have the option of
capturing the return stroke's energy directly. Even with an electrical system,
where this is possible, it would add a whole lot of complexity.

> In these cases, you can distribute mechanical energy without conversion
> losses.

Without conversion losses, maybe. However, you are going to lose a lot of
energy to friction (especially if you have a lot of the rocking posts,
friction posts, hold-downs and so on). Also, unless the rods connecting the
machines are perfectly elastic you're going to lose a bunch of energy to
heating the rods themselves.

You can have all the "Doubts on progress and technology" you want, but if you
only count one kind of loss (electrical conversion) and not another
(mechanical friction and inelastic fraction) you're going to end up with a
non-realistic bias in favor of mechanical systems every time.

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bigiain
"You can have all the "Doubts on progress and technology" you want, but if you
only count one kind of loss (electrical conversion) and not another
(mechanical friction and inelastic fraction) you're going to end up with a
non-realistic bias in favor of mechanical systems every time."

I've been wondering for a while whether anyone's trying to re-capture some of
the "lost" energy from household electrical systems. I wonder why my fridge,
aircon, and stove aren't "pre heating" the cold water going into my hot water
heater? I even wonder why all my "fixed electronics" - I'm looking at the TV,
Playstation, audio gear, media center PC, home networking gear - have all got
heatsinks and fans "disposing" of "waste heat" (which I sometimes then spend
more money dealing with by cooling the room down with aircon).

Is there _really_ no good way to capture all that "waste heat" and use it to
offset the energy I consume having a hot shower every day?

(I'm guessing I'm not the first to ever have these thoughts, and that the
answer right now is "power is so cheap that the payback time for any available
technology that could do this is way longer than practical". Which satisfies
the pragmatist in me, but still makes the tree-hugger in me slightly
melancholy.)

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marvin
There is a very simple solution to this if you are in an area where
electricity is cheap and the climate is cold. Simply use electrical heaters
with a thermostat. Using electronic appliances, including light bulbs,
increases the temperature and reduces the time your heaters have to run.

This is also the reason why low-energy light bulbs are less profitable in
certain countries.

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schiffern
Your solution is penny wise and pound foolish. Using heat pumps will save you
enormous amounts of energy overall, even though your appliances look
superficially worst under that analysis.

The economic equivalent would be:

 _You:_ "Hey Bob, those are expensive fishing trips. Think of the opportunity
cost!"

 _Bob:_ "Thanks, you've saved me a bundle. I'll go quit my job immediately!"

(The effect you're citing is real, but the explanation is more basic: at low
energy costs, efficient goods have longer payoffs. This happens regardless of
what heating method people use.)

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marvin
Yes, this is very obviously true. But there are very good historical reasons
why this is the way things have traditionally worked in Norway.

First, heat pumps were very uncommon until only a few years ago, since no one
needs A/C in this cold climate. A heat pump can have a 10-year payoff with our
electricity costs, although this has gotten better in recent years. There is
no gas infrastucture. And it makes no sense to switch to high-energy
appliances untli you're switched to more efficient heating.

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bane
My father grew up in Southern Illinois when there was still oil being pumped
out of the ground. His father, grandfather and great-grandfather worked on
systems that sounded like these. A trip to area let me see an old single
piston engine [1], but we never found any of these systems still working.

According to my father, my grandfather would go to the central hub and grab
hold of one of the lines for a few moments, then to the next and the next. He
could tell by the way the line was moving and felt if there was a problem down
field he needed to attend to.

I never quite "got" what he was talking about in my mind, and my father was
very young when he saw them in action so I never really had a great
explanation of what these "lines" were.

Great post and finally fills in a gap in my father's childhood stories.

[1] - they looked something like this
[https://www.youtube.com/watch?feature=endscreen&NR=1&...](https://www.youtube.com/watch?feature=endscreen&NR=1&v=e_7r4FHt0zI)

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rwinn
Video: <https://www.youtube.com/watch?v=ALPkDoX9Wz0>

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nickpinkston
To see one of these systems in action, the Drake Well museum in north Western
Pennsylvania has the system used to pull the first oil wells. From steam
engines to the well pumps - it's very cool place if you're up by Erie. Also, a
nitroglycerin blasting demo is pretty cool.

<http://www.drakewell.org/>

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gus_massa
Is this really more a efficient way to transmit energy than electrical
currents? Anyone has a link to a economic analysis?

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wlesieutre
It's transmitting power directly instead of taking it through a generator then
back again using a motor, so it's quite possible. A quick search suggests that
motors and generators can both be over 90% efficient in the
electrical/mechanical conversion, but I would guess that you could do better
in a purely mechanical system.

Over short distances we already use mechanical energy transfer all the time
(drive shaft in cars, chains in bikes, etc.), this takes the same idea and
extends it to a longer distance.

My hunch is that while it would still work in theory, electrical systems would
win out because of construction costs and maintenance. Motors and generators
are widely available, wire gets laid once and works for decades, and
contractors know how to deal with all of it. A jerker line needs more frequent
lubrication, has custom parts that wear out, and when they do you can't just
say "I need a new NEMA 6 motor" and have it in a day.

EDIT: Also worth noting that the high efficiency numbers for the electrical
system are going to be at peak load, if you run it at partial they'll drop.
The frictional losses on a jerker line are probably a bigger percent of the
total at part load as well, but I don't know whether they'd be more or less
significant than a generators'.

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wiml
It's really easy to overestimate the efficiency of a mechanical system. Each
of those swiveling joints, wheels, etc., is going to lose a few percent even
if perfectly maintained. Some of the devices like the friction supports will
lose more.

Regarding replacement, I suspect that in an oilfield in the back of beyond in
the late-19th/early-20th century, many of the replacement parts for these
systems would be made on-site with a saw or a farrier's anvil.

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wlesieutre
It might come down to whether you're using the oscillating motion directly or
trying to turn it back into rotation. There's no way that you'd get rotation
more efficiently than a motor, but elements like the tripod pendulums seem
like they'd have comparably small losses to the generator/motor. Then again,
I've never seen any measurements of energy losses on pushing a pendulum back
and forth, so as you say, I could be overestimating the efficiency of those
too.

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pontifier
I have often thought of using a similar system for power distribution in a
robot. a single powerful motor with flywheel, and multiple cables to transmit
power to each joint.

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sliverstorm
Wait, but then you have to regulate speed to each joint. Is there an easy way
to do this I haven't thought of?

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bigiain
If you've got a (mostly) symmetrical action, like bipedal walking, there
almost certainly is some way to recapture "returned power" from footfalls to
reuse for the next step. It'd be a little different from just balancing
reciprocating pumps against each other, since you'd need to "time slip" the
recaptured energy - but a flywheel might make that possible without incurring
too much loss to make it worthwhile.

For multi-legged robots, a bit of smart geometry can pretty much do this
already - see these things: <http://www.strandbeest.com/>

I suspect using some computer-adjustable versions of the "multipliers" from
the article would allow you to build something like a strandbeest which you
could steer while only losing a little of the efficiency.

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ck2
Hmm, the very first "smart grid".

Well not so smart in itself but very cleverly used.

First steam-powered cable-car systems were also at the end of the 1800s.

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jchrisa
This company builds tech for using municipal water supplies as a power
distribution system <http://www.lucidenergy.com/>

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js2
Wonder how many digits and limbs were lost to such systems.

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ars
Probably not many. The lines don't move very fast - about 1 cycle per second.

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gus_massa
But the tension is (probably) very high, if a digit gets trapped it'd
(probably) get crushed.

