Subject:
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Re: Some help or advice requested
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Newsgroups:
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lugnet.technic
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Date:
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Mon, 25 Jan 2010 06:03:49 GMT
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Viewed:
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20807 times
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In lugnet.technic, Owen Dive wrote:
> In lugnet.technic, Owen Dive wrote:
> > Hi all.
>
> SNIP
> > Thanks in advance for any suggestions.
> >
> > Owen.
>
> I have been asked for some pictures of what I am working on (very much
> prototypes at the present - don't expect anything elegant).
>
> http://www.brickshelf.com/gallery/captainowie/Decimator/picture_001.jpg
> This is the track for the tray, and the drive mechanism. As the axle at the
> front (bottom) of the device turns, the black liftarms pick up the tray and
> carry it forward a distance of exactly two studs. They then leave the tray alone
> for half their rotation, which is critical for the other part of the machine
> (not relevant here). You can see the tray in the top corner.
>
> http://www.brickshelf.com/gallery/captainowie/Decimator/picture_002.jpg
> This is the track from a different angle, and the tray. The pins in the tray are
> there to ensure that the liftarms have something to push against.
>
> http://www.brickshelf.com/gallery/captainowie/Decimator/picture_003.jpg
> Here you can see the tray in the track, at one limit of its travel.
>
> Hope that helps to clear things up - keep the ideas flowing!
>
> Owen.
Ok, so I have something that appears to do what I need it to do, however, it is
a bit of a monstrosity, and I think that it shows either that I am a genius, or
a madman - I'm not sure which!
Bear in mind that this still includes several quick hacks to get the thing to
work - it's far from production quality.
So. http://www.brickshelf.com/gallery/captainowie/Decimator/picture_004.jpg
and http://www.brickshelf.com/gallery/captainowie/Decimator/picture_005.jpg show
The Device primed and ready for action. The trigger is the blue axle joiner at
the top of the image. The grey connector on the same axle is blocking the
rotation of the 24t gear, which is in turn blocking the rotation of the 40t
gear. When the trigger is lifted, both gears begin moving due to the weight of
the black weight brick. This then falls with enough momentum to force the red
liftarm into the down position, flipping the switch at the same time.
http://www.brickshelf.com/gallery/captainowie/Decimator/picture_006.jpg and
http://www.brickshelf.com/gallery/captainowie/Decimator/picture_007.jpg show The
Device after this has happened. Now all you need to do is pull the blue angled
liftarm to make the elastic band pull the red liftarm back to its original
position, flipping the switch again.
Potential energy is supplied via the 24t gear at the bottom of the image (the
one in the horizontal plane), which drives the weight back to the top via the
worm gear/clutch gear pair.
Other things to note:
* The axle that the 40t gear is on does not go through the centre of the gear.
This allows the 40t gear to only mesh with the trigger-stop when the weight is
just past the top of its travel.
* The clutch gear allows the input to keep turning even when the weight is
blocked by the trigger.
* The freedom of the worm gear to move upwards allows the weight to fall
naturally, without being restricted by the input speed.
* The fact that the operation is assymetrical is no bad thing. The backwards
speed of the tray need not be limited by the necessarily slow forward speed - in
the same way that a typewriter carriage moves forward one letter space at a
time, but can be returned all at once.
* The tall white brick above the switch is there to guide the weight brick so
that it doesn't catch on any of the other bits, and the cam on the blue liftarm
is there to stop it (the liftarm) falling into the path of the weight.
Questions, comments or constructive criticism? My gut feeling is that the whole
thing is overcomplicated - however, that could fit in well with the rest of the
machine!
Thanks to everyone who has contributed, both in this thread and via email.
Owen.
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Message is in Reply To:
 | | Re: Some help or advice requested
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| (...) SNIP (...) I have been asked for some pictures of what I am working on (very much prototypes at the present - don't expect anything elegant). (URL) is the track for the tray, and the drive mechanism. As the axle at the front (bottom) of the (...) (15 years ago, 22-Jan-10, to lugnet.technic)
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