MikeWhy wrote:

Locking against heavy loading would seem to suggest a worm. PV? A
Stirling pumped "hydraulic" motor/water wheel? I know... complexity.

PV plus motor plus worm drive is certainly an attractive route, but too
expensive and not suited for local production and maintenance.

It needs to be really simple and so inexpensive that it's not worth
stealing. For context, rural Somalia might be one of the target "market"
areas.

--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
http://www.iedu.com/DeSoto/

On Apr 25, 4:47*pm, Morris Dovey wrote:
[snip]

The sun-tracker will, of course, need to make one (controlled) cycle per
day, and somehow (automagically) start out facing east in the morning.


That's an easy one. Expanding gas cylinder like the greenhouse people
use to open a vent. Hide it in the shadow of the collector itself, so
when the sun peeks around, it starts expanding till it creates its own
shadow again sortakinda like a wheatstone bridge but mechanical. When
the sun stops playing peek-a-boo with the cylinder at night, it is
brought home by its own collapse, perhaps helped by a counterweight/
spring.
The cylinder would sit lengthwise along the obvious edge. It could sit
in a slot in the collector itself for extra intensity. The mechanical
challenge is minimal.


Maybe something bi-metal?

On Fri, 24 Apr 2009 21:28:34 -0500, Martin H. Eastburn wrote:

Robatoy wrote:
On Apr 24, 11:33 am, Morris Dovey wrote:
Swingman wrote:
Their problem ... this guy nicely illustrate that more than a few
intelligent, resourceful woodworkers have snapped to using SketchUp
on their own hook.
And for us unintelligent, non-resourceful folks, who have unreasonable
difficulties drawing precise involute gear teeth with SU, there are
(free) tools like

http://www.forestmoon.com/Software/GearDXF/

that produce DXF files of gears for use with DummyCAD (and other
software).


You'd need a .dxf import function that is pretty robust to take
advantage of that, eh?
:-^


I have multiple cad packages that can do that.

I have a excel spread sheet that generates gears and the output can be
imported for a gear in my cad. Kinda neat. I made some spiral gears
that hang from a line and dangle below.

Martin



Slightly OT, but do any of you who play with gears have a suggestion for
a package I could use to model simple-to-middling gearboxes, both CAD
style drawings and also actual modelling where I could adjust the speed
of an input shaft (or two) and see what happens?

Robatoy wrote:
On Apr 25, 4:47 pm, Morris Dovey wrote:
[snip]
The sun-tracker will, of course, need to make one (controlled) cycle per
day, and somehow (automagically) start out facing east in the morning.

That's an easy one. Expanding gas cylinder like the greenhouse people
use to open a vent. Hide it in the shadow of the collector itself, so
when the sun peeks around, it starts expanding till it creates its own
shadow again sortakinda like a wheatstone bridge but mechanical. When
the sun stops playing peek-a-boo with the cylinder at night, it is
brought home by its own collapse, perhaps helped by a counterweight/
spring.
The cylinder would sit lengthwise along the obvious edge. It could sit
in a slot in the collector itself for extra intensity. The mechanical
challenge is minimal.

I've been considering /two/ such gas cylinders (so that operation isn't
air temperature dependent) - one on each side of the collector, each
side connected to opposite ends/sides of a double-acting hydraulic or
pneumatic cylinder. That setup would allow for an eastward pressure bias
that would be overridden during the day, but would cause the tracker to
revert to east-pointing at night, pretty much as you describe.

The major drawback appears to be instability in gusty winds due to the
gas' compressibility.

Maybe something bi-metal?

Maybe, but I think your first idea is a better match to the problem.

--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
http://www.iedu.com/DeSoto/

Morris Dovey wrote:
MikeWhy wrote:

Locking against heavy loading would seem to suggest a worm. PV? A
Stirling pumped "hydraulic" motor/water wheel? I know... complexity.

PV plus motor plus worm drive is certainly an attractive route, but
too expensive and not suited for local production and maintenance.

It needs to be really simple and so inexpensive that it's not worth
stealing. For context, rural Somalia might be one of the target
"market" areas.

Offhand I'm not sure how one would design such a thing but rather than using
shaft work could you pump water from one plastic bag to another, with
appropriate levers and paddles resting on top of the bags?

J. Clarke wrote:
Morris Dovey wrote:
MikeWhy wrote:

Locking against heavy loading would seem to suggest a worm. PV? A
Stirling pumped "hydraulic" motor/water wheel? I know... complexity.

PV plus motor plus worm drive is certainly an attractive route, but
too expensive and not suited for local production and maintenance.

It needs to be really simple and so inexpensive that it's not worth
stealing. For context, rural Somalia might be one of the target
"market" areas.

Offhand I'm not sure how one would design such a thing but rather than
using shaft work could you pump water from one plastic bag to another,
with appropriate levers and paddles resting on top of the bags?

Maybe. I've been too involved in trying to help get the engine working
to worry about the tracking system until now. Nearly all of my past
experience with control systems has been digital, and I'm really in over
my head on this one.

It seems to me that if I can choose one side to pump to, then I should
be able to pump to a cylinder/piston linear actuator of some kind
(thinking of a reworked shock absorber or strut) to do that job.

Hmm - if I use robatoy's gas cylinder idea to control a valve to direct
part of the pump flow to one of your actuators, I might be on a better
track than I am now, even though I'll still need to figure out some
reliable way to make it face the morning sun without being vulnerable to
nighttime gusts.

--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
http://www.iedu.com/DeSoto/

On Fri, 17 Apr 2009 03:39:52 GMT, the infamous "Lew Hodgett"
scrawled the following:

"Phisherman" wrote:

The gear mechanism is amazing on this shop-made tablesaw jig. Check
out this video:

http://tinyurl.com/dxdwlu

Don't want to pee on somebody's parade, but looks to me like a lot of
complexity for what is basically a very straight forward task.

I give you Fred Bingham's book for reference.

Which one? _Practical Yacht Joinery_, which I bought, knowing full
well that I'd be rich someday soon, or _Boat Joinery and Cabinet
Making Simplified_?

Agreed, a stackable type of box joint jig is easily possible, it could
only do one side at a time, unlike this one. Mathias' jig ROCKS!

------
We're born hungry, wet, 'n naked, and it gets worse from there.

"Larry Jaques" wrote:


Which one? _Practical Yacht Joinery_, which I bought, knowing full
well that I'd be rich someday soon, or _Boat Joinery and Cabinet
Making Simplified_?

Take your choice, it's in both.

Lew