Subject:
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Pnuematics: e-switch and thoughts
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Newsgroups:
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lugnet.build, lugnet.robotics
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Date:
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Tue, 20 Oct 1998 21:32:38 GMT
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Viewed:
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2281 times
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After following the ongoing pneumatic thread, I thought I would
1) show my newly designed electric switch
2) talk about the glory of pneumatics and
3) throw in my 2 pickles.
There are references to the previous pneumatic thread in this post.
First here is a micromotor actuated pneumatic switch
http://www.members.home.net/ourcreations/pictures.htm . This design has a
fairly small bounding box. When the basic supports in this mock up are
incorporated into an existing model superstructure, the mecanisim it becomes
fairly small. I made this mostly because I think the pneumatic elements are
great, and to change the opinion that they might not be worth the space.
"If you just want to move something, other techniques need much less
overhead."
That might be true for moving something light, but a gear system that can
snap a 16 stud beam would be hard pressed to fit in the bounding box made by
the above switch, a piston, a and compressor setup. Granted, that's not
much of a test of utility, but pneumatics do show an advantage when you need
strength. Aswell the fact that the pistons already have linear motion, can
be advantageous over producing such motion with a motor system.
Another advantage is the 'place-ability' of a piston. I find a piston can
be more easily placed in tight positions than can a fixed drive chain (in
some situations). There is an advantage of greater physical flexibility
between power input and output. It is the difference of building a model to
compliment a pneumatic system, and building a model *around* the nessesary
gears for a drive system
As for the small piston being too weak for use... that's like saying the 1x4
beam is too short to span a 6 stud gap. Everything lego element has its
place and function.
DISCLAIMER:
I should say that I usually run my pneumatic models with an umbilical, and
although I have monkey-ed around with compressor pumps (designed a few) I
have not used them that much. One of my models has 4 large and 6 small
pistons, and eats air. For prototyping I use a 1 litre pop bottle as a tank
and four hand pumps hooked in parallel. As well the switches are integrated
into a 'virtual' hand control and are actuated with finger motion (so I
circumvent the space and stiff switch complaints as well).
Still, I feel the pneumatics have their function, and to dismiss them too
quickly would be a mistake. I'm not saying go buy them, but don't pass on
them out of hand. Like someone already said, I like them for their
"undiscovered" uses. For me that's LEGO.
Ask not what your Lego can do for you, but what you can do for your Lego.
LINC
Continued pneumatic blathering past this point...
To reduce piston speed I constricted air flow inline. I used a small gauge
disposable syringe tip. Score and snap off a section of the tip to fit in a
T-joint. Place the section in the T-joint and glue in place. I am against
piece modification and can't use this, but it might be useful for someone
using pneumatics in a Mindstorms creation.
***All Lego piece desecration was carried out by my girlfriend as I cowered
in the corner.***
The storage tank I eluded to above is made from a 1 litre plastic pop
bottle. I haven't pressurized it until the pumps bleed off excess, because
I am afraid it will blow. Take the lid, remove the lid liner, punch two
holes in the lid and awl out with scissors, cut two small (slightly smaller
than tube diameter) holes in the liner corresponding with the lid's holes,
add tubes through the lid and liner... if the holes are small enough they
are self sealing. I wouldn't recomend drilling the holes because the holes
might be too clean and not self-seal as well. "Pushing" the holes through
the lid improves sealing.
For a standard compressor setup using pulleys and v-belts, by offsetting the
large pulley with a cam element you can charge a compressor tank to a higher
pressure before stall (or you have your regulator kick in). By timing the
pulley offset and the pump action, when torque requirements are low (pump
recovery) the drive axle spins faster, and when torque requirements are high
(last little push of the pump piston) the drive axle slows and is given more
leverage. No rpm loss (possibly? an increase).
Question: Has anyone done maintenance on the pistons; used lubricants or
cleaners. I find that the pistons will get sticky spots on the metal if
left in one position for a long period.
Things that could be improved:
-- Yes, if possible make the switches with less friction. However, the
above switch setup demonstrates that is not completely necessary.
-- Elongate the overlapping through-holes within the switch. (i.e, make
some of them in a 'teardrop' shape) This would allow finer control of the
piston as air flow would be more restricted if you moved the switch only
slightly to one side. As you continue to move the switch, the hole would
progressively become larger and air would move faster. This would simply
improve fine control and help prevent on-off-jerkiness.
-- put stud *holes* on the other side of the switch.
Well there is my two pickles.
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Message has 3 Replies:
 | | Re: Pnuematics: e-switch and thoughts
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| Much agreement from me! It's amazing what creative uses there are for them, I pointed out earlier that I made a catapult, which when the air pressure builds up enough, it flings a 1x12 which has a open box with ballow tires. I also made a good (...) (26 years ago, 20-Oct-98, to lugnet.build, lugnet.robotics)
| | | Re: Pnuematics: e-switch and thoughts
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| I must applaud Linc for a wonderfully design switch... I love it :) I also agre with everything he has said about the Pneumatic elements. One trick I have found to be very usefull is using pneumatic cylinders as motion-transfer devices. If you take (...) (26 years ago, 21-Oct-98, to lugnet.build, lugnet.robotics)
| | | Re: Pnuematics: e-switch and thoughts
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| (...) That link doesn't work anymore. Can anyone tell us how this construction worked? (any gears? Levers? Maybe a worm gear?) I might want to use the idea in a Mindstorms design. (by the way, I really liked the soda bottle tank idea and might try (...) (25 years ago, 10-Aug-99, to lugnet.build, lugnet.robotics)
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