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Hi all. I am currently working on a project (to be revealed in due course!) and I've come across something of a stumbling block. I have a tray that is constrained to move in one dimension, and a series of short liftarms under the tray, all rotating (...) (15 years ago, 19-Jan-10, to lugnet.technic)
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| | 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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(...) SNIP I don't think there is a 'save' way to do that. In fact thats the reason reversal switches have dead space, because you will short circuit stuff otherwise (might be only for a millisecond though). I don't know if you ever worked with some (...) (15 years ago, 22-Jan-10, to lugnet.technic)
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| | Re: Some help or advice requested
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(...) <snip> Hi Owen, As you say, you want a mechanism where the switch wants to be either on or off, but not in the middle. Had you thought about adding a pivot point at the top of the switch handle, with an axle going up and a weight at the top. (...) (15 years ago, 22-Jan-10, to lugnet.technic)
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(...) Hmm, an interesting solution. (...) But there's the rub! I'm afraid I can't see an obvious way to do that, given that the weight will need to be positioned quite precisely. I will play around with it, though, and see what I can come up with. (...) (15 years ago, 22-Jan-10, to lugnet.technic)
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(...) Last year I built a pneumatic excavator module for a GBC display exactly for this reason: doing it with an RCX would have been like cheating when it could be done mechanically :D As for your 'problem', I've been turning this over in my mind (...) (15 years ago, 23-Jan-10, to lugnet.technic)
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(...) 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 (...) (15 years ago, 25-Jan-10, to lugnet.technic)
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(...) ... (...) Well, seeing your pictures, I can't help wondering: do you actually need the tray to change direction as soon as it hits the end? If not, you can use a much easier solution: just power its motor for a given amount of time in one (...) (15 years ago, 25-Jan-10, to lugnet.technic)
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(...) You're quite right in that there's nothing in the pictures to suggest that having the having the motor running after the tray reaches its stop would be a bad idea. However, that would be disastrous for the rest of the machine - think of a (...) (15 years ago, 25-Jan-10, to lugnet.technic)
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| | Re: Some help or advice requested
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(...) <snip> (...) I've got a slightly different solution, where the tray tips an inverted pendulum right and left. The pendulum's momentum/weight flip the polarity reverser. The tri-blade bounds the inverted pendulum's swing. The first three steps (...) (15 years ago, 26-Jan-10, to lugnet.technic)
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(...) (URL) (...) (URL) (...) Kevin (15 years ago, 26-Jan-10, to lugnet.technic)
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(...) A nice solution, but I doubt very much if my tray could push the pendulum upright (especially since the total angular travel would be the limited movement of the pendulum _plus_ the angle that the tri-blades had rotated). However, for (...) (15 years ago, 27-Jan-10, to lugnet.technic)
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| | Re: Some help or advice requested
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(...) It would depend on how much of the dead band you eliminate. Cleaning up bookmarks I came a cross this which might work: (2 URLs) Jetro (15 years ago, 27-Jan-10, to lugnet.technic, FTX)
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Here is yet another possible solution that I have found effective for something very similar (a vehicle that reverses its direction when it hits an obstacle). This one is purely mechanical (no electrical switch needed). (2 URLs) The mechanism relies (...) (15 years ago, 31-Jan-10, to lugnet.technic)
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(...) Hmm, I had dabbled with a similar solution, but inverted (with the motor driving the bottom gear and the two side gears the two outputs, but discarded it for reasons that escape me at the moment. I must investigate this further. Thanks! Owen. (15 years ago, 2-Feb-10, to lugnet.technic)
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(...) Yes, there are quite a few possible variations on this mechanism. There is even at least one in an official model: (URL) Hope you get it working. I always like a purely mechnical solution :) (15 years ago, 3-Feb-10, to lugnet.technic)
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(...) SNIP (...) So I bet you had all been waiting with bated breath for the revelation of my project, and then I bet you had all thought that I had given up, when there was no revelation forthcoming. In actual fact, I had been working on this until (...) (14 years ago, 27-Mar-11, to lugnet.technic) !
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| | Decimator (Was: Some help or advice requested)
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(...) Cool! (You may be mad, but only in the very best way. ;-) Play well, Jacob (13 years ago, 17-Jun-11, to lugnet.technic)
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