Hi there. I am mainly a lurker here, and enjoy very much learning
from each of you. I have encountered a problem, and hope the group
may be able to help me solve it. I am trying to make a small
candle-powered turbine, but with several approaches tried, I haven’t
been able to overcome friction at the point where the blades (which
I cut from a disk of copper) meets the supporting spindle. Can anyone
offer any suggestionse
Thanks in advance.
Not much detail to work with. I am assuming the spindle is vertical
if the turbine is driven by rising convection from candle. My first
thought is this. Fix the turbine disc to the spindle so the spindle
rotates WITH the turbine rather than the turbine rotating ON the
spindle. The spindle can then rotate, supported at its lower end.
The bottom end of the spindle should be tapered to a point upon
which it rotates and which rests in a depression, perhaps created by
tapping a small ding into the supporting surface with a centre
punch. The surface area of that point contact is much smaller than
the surface area of a hole in the turbine disc rotating against the
side of a stationary spindle. The upper end of the spindle likewise
can be captured in a small conical ding which exerts no downward
pressure on end of spindle, just keeps it from wobbling. If the
sides pf the conical depressions in which the ends of the spindle
are turning are a 60 degree angle (standard centre punch shape) then
the point of the spindle should be slightly less, just a degree or
two, so the spindle end truly contacts the bearing surface only on
its point, not on its sides. Best lubricant if one needed - whale
oil or watch lubricant. Hope this helps.
Marty, spinning around in Victoria BC
And, depending upon scale etc, the disc may be hung from the two
ends of an inverted “V” (or 2 inverted V’s at 90 degrees to each
other) supported at their centre on the tippy-top point of a
vertical spindle. How big is this contraption anyway? Like one of
those Scandinavian Xmas thingies with the flying brass angels? Up,
up, and awaaaaay!,
One solution I’ve seen (where the turbine is horizontal, the spindle
vertical) is to use a small, closed off glass tube as shaft for the
blades; this then turns on the tip of a needle inserted into the
tube.
Seen sideways (hope this works!)
/ glass tube
/
I Needle inside
\
Cheers
Hans Durstling
Moncton, Canada
why don"t you use a ruby at that junction point. al upscale watches
use them, totally without friction. just my humble opinion. gerry!
Do you mean something along these lines, only small?
http://www.ganoksin.com/gnkurl/ep81ea
If so I know the artist and he has to be very careful about the
weight of the spinning parts and where they attach to the vertical
pole. He uses ball bearings as well.
Aggie
Yeah, I guess a little more info would have been nice! I am aiming
for a small desk-top model. The horizontal turbine will, I hope, be
about 2 to 2-1/4 inches in diameter. The apparatus is to be mounted
on a piece of hardwood, with a depression to place the candle in just
the right place.
Again, if all goes well, I hope to somehow mount small “figures” –
dogs, cats, Chinese characters, blacksmithing tools, etc., around the
edge of the turbine, sort of like the bigger Christmas turbines.
However, I want this small. Sort of a personal model.
I have already gotten some very good ideas from each of you. I am
trying to build on these, to come up with something viable. Some of
them have taken me down paths I hadn’t thought of. I am hoping these
will lead even further.
Thanks, and if anyone has additional ideas…
Do you mean something along these lines, only small? http://www.ganoksin.com/gnkurl/ep81ea
Not really like these beautiful pieces, Aggie. I’ll try to find a
pic of what I’m talking about. Then I’ll learn how to post pictures!
(Thanks for your reply — I always enjoy your comments!)
OK - One candle power source - necessarily mounted off-centre to the
turbine because the spindle occupies the centre position.
Therefore the force applied to the turbine disc by the rising column
of heated gas is off centre and will want to tilt the disc and
spindle away from the hot side of the circle. The little Xmas candle
turbines with which we are all familiar solve that problem by using
more than one candle to counteract that off-centre effect. Two,
three, or four candles are placed symmetrically under the disc to
keep the forces balanced.
Any decorative objects hung from the turbine disc will apply their
own off-centre weight and, as the disc turns, will apply their own
cyclic forces trying to wobble the disc. So those bits should be (as
nearly as possible) equal in weight to each other and symmetrically
placed around the circumference to minimize the tendency to wobble.
The driving force from the candle is small. The off-centre effort
from the one candle and the dynamic forces of the dangling
decorations may, at some rotational speed, coincide with the natural
harmonic frequency of the whole assembly and amplify a vibration,
albeit small, which my be difficult for the candle to overcome and
which may inhibit rotation. Alternatively and worse yet, it may pass
a tip-over point and evolve into a self-perpetuating exponential
feedback loop, producing a cyclonic vortex (think “firestorm”) or
mechanical vibrations strong enough to shatter nearby structures. .
My intuition is that you should work with minimum of two candles
opposite each other and a larger diameter disc to make things a bit
easier - maybe 4 inches.
Get things right and you may be on the verge of producing a
perpetual motion machine. A centuries-old dream realized.
Good luck.
and wear a hard hat
Marty - staying in dynamic balance here in Victoria