Subject:
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Re: pneumatics & mindstorms?
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Newsgroups:
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lugnet.robotics
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Date:
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Thu, 29 Jul 1999 09:25:57 GMT
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Viewed:
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1201 times
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> In lugnet.robotics, Mario Ferrari writes:
> > I had exactly the same experience. I used that kind of compressor on my S5
> > robot many months ago, it's slow and unefficient.
> > The small pumps work much better. Ralph Hempel has a very good double action
> > compressor in his page:
>
> I did not build a compressor using the large pumps before, only the small
> pumps, so I believe in your findings. Still I wonder why.
>
> The larger pump takes more force to move than the smaller pump, but the larger
> pump also pushes in more air per stroke than the smaller pump. There must
> something other than the sizes that causes the difference in efficiency.
> (Friction?)
Yes, I guess friction is the answer.
1) The difference in the surface of the pistons between the two kind of pumps
is important. I didn't compute the ratio, but imagine can easily be 1:10 or
even more. To get that ratio you need to gear down your motor using two 8:40
stages, and this produce a lot of friction (even worse if you use a worm
gear). So a good part of your power gets lost.
2) The large pump seems to have more intrinsic friction too, I mean if you
remove the spring and apply no load is still a bit hard to move, while the
smaller one has almost no friction (and probably worse airtight!).
> The tank pressure is not constant. Maybe we need an automatic transmission: We
> switch to the lower gears when the pressure is built up. (I think this is too
> complicated for being practical. Still, an interesting thought.)
>
> Maybe we should use something like a balloon as the tank. The volume of the
> Lego tank is not expandable, therefore within one or two operations, the
> pressure goes down quickly while there are still lots of air in the tank. As
> the result, the actual usable volume of the Lego tank is only a fraction of
> its total volume.
I like the idea of the balloon tank, although not from an aesthetic point of
view :-)
I usually try to get a more constant pressure using more than one air tank.
With 3 or 4 tanks you can perform some very fast pneumatic actions in sequence
without problems, and then give the compressor its time to restore pressure.
Luckily enough, a few months ago I was able to order some air tanks at the
French Lego Service (the european version of S@H). I think France is the only
country where they are available as spare parts.
Mario
http://www.geocities.com/~marioferrari
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Message has 1 Reply:
Message is in Reply To:
 | | Re: pneumatics & mindstorms?
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| (...) After the big piston operates once, how long does it take to recharge the pressure? (...) I did not build a compressor using the large pumps before, only the small pumps, so I believe in your findings. Still I wonder why. The larger pump takes (...) (25 years ago, 28-Jul-99, to lugnet.robotics)
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