Subject:
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Re: Pneumatically driven locomotive ??
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Newsgroups:
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lugnet.trains
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Date:
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Tue, 24 Apr 2001 17:34:14 GMT
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Reply-To:
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cmasi@cmasi.NOMORESPAMchem.tulane.edu
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Viewed:
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801 times
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Shaun Sullivan wrote:
>
> Just out of curiosity, has anyone ever succeeded in putting together a
> pneumatically driven train? Reading through some of the posts regarding
> the new S@H train offerrings, I got to thinking that it could probably
> be done - it would make an impressive feat, and would be pretty
> realistic, with compressed air being substituted for compressed steam.
>
> I'm envisioning a battery-driven motor or two pumping like mad to
> maintain air pressure in some of the blue tanks, hidden within the black
> "fuselage" (please forgive me, I'm still picking up on the train
> lingo). Two of the small actuating clinders could be the actual drive
> pistons, one on each side. Then, using a standard linkage, these
> pistons could be connected to the drive wheels.
>
> One air tank could use its air to push the cylinder out. A mechanical
> switch that was somehow triggered by the position of the wheels (and
> thus the linkage) could then direct air from the other tank, to pull the
> cylinder back in. By alternating the cylinders/tanks, my thought is
> that you could actually turn the wheels, just as in a steam locomotive.
>
> Since the switching of the cylinders is *position* determined, this
> system would provide more force initially, when the train has to
> overcome its inertia. The longer the wheel takes to turn halfway (and
> activate the switch), the more air pressure builds up, exerting more
> torque via the linkage.
>
> Granted, you'd still be using electricity to provide the compressed air
> - I guess its a small compromise, considering the inadvisability of
> actually having open flames or burning coals on your ABS. But other
> than the compressor motor(s), the system could be compeltely
> mechanical. And all of the components could be hidden pretty well, I
> imagine. It sure would be a beautiful sight to see a LEGO train moving
> under its own power ...
>
> So, has anybody tried this? And if not, who's up for the challenge?
> I'm interested in giving it a try, but I'm afraid it's a couple months
> away on my list of projects ...
>
> -shaun
I have always wondered how steam engines do deal with pistons winding up dead
center. With a car, the starter motor gets the fly wheel going, so there is
already momentum before the pistons start firing, but with a steam locomotive
the pistons start at a dead stop and the inertia of the train seems like is
would outweigh the momentum of a wheel. The only thing I can think of is to have
the sides push at different times.
Side A starts to push, and 1/4 of the way through its cycle side B starts to
push. When side A reaches dead center side B is has only gone 1/4 of the way
through its cycle, so side B can push side A past dead center. When side B
reaches dead center, side a is 3/4 of the way through its cycle, or 1/2 way
through the powered return cycle, and side A can push side B through dead
center. To do this with LEGO the axles would have to be linked together, and the
back and forth mechanism of the push rods would have to be tied to a pneumatic
switch. If someone can pull it off it will be an impressive engineering feat!
Chris
--
See some of my LEGO creations at http://cmasi.chem.tulane.edu/~lego/
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Message has 1 Reply:
 | | Re: Pneumatically driven locomotive ??
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| (...) have (...) That's how it is done, it's called "Quartering". Realize that a 2 cylinder, double acting steam engine has as many power strokes as a 8 cylinder car engine (4 stroke). Because the "push" for the pistons comes from the steam, the (...) (24 years ago, 24-Apr-01, to lugnet.trains)
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Message is in Reply To:
| | Pneumatically driven locomotive ??
|
| Just out of curiosity, has anyone ever succeeded in putting together a pneumatically driven train? Reading through some of the posts regarding the new S@H train offerrings, I got to thinking that it could probably be done - it would make an (...) (24 years ago, 24-Apr-01, to lugnet.trains)
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