DLuders Posted November 13, 2011 Posted November 13, 2011 slfroden posted this of "A proof-of-concept to realise the control of two Lego linear actuators using a single Lego motor."The top linear actuator has more resistance than the bottom one due to the white rubber belt. "When the motor spins, it turns the differential, which provides power to the bottom linear actuator since it has less resistance. "Once the bottom linear actuator has extended or retracted as far as it will go, it's resistance becomes greater than the resistance provided by the white rubber belt, and the power from the differential then transfers to the top linear actuator. "The key to getting this working well is getting the resistance of the white rubber belt just right. "A modified version of this set-up could be used to control a gearbox, such as Sariel's 4-speed Compact Linear Gearbox ( http://sariel.pl/2010/07/4-speed-compact-linear-gearbox/ )." slfroden made this follow-on : "A proof-of-concept to realise the control of two gearbox selectors using a single Lego linear actuator and a single Lego motor. "When the the linear actuator extends it moves two linkages. The bottom linkage has a stretched white rubber belt, and as the belt begins to contract the bottom linkage moves first. Once the bottom linkage can move no further, then the top linkage begins to move. "When the the linear actuator retracts, the top linkage moves first, followed by the bottom linkage. "The gearbox design is a slightly modified version of Sariel's 4-speed Compact Linear Gearbox ( http://sariel.pl/2010/07/4-speed-compact-linear-gearbox/ ). "Unfortunately this set-up only uses three out of the four available gears in the gearbox." Quote
Sokratesz Posted November 13, 2011 Posted November 13, 2011 Nice, I built the same some time ago but I didn't have LA's to control it yet back then - Sok Quote
Alasdair Ryan Posted November 13, 2011 Posted November 13, 2011 In the top video it's says ' both rams fully retracted' when the top one is not. Quote
Splat Posted November 14, 2011 Posted November 14, 2011 (edited) DLuders, thanks for posting my videos (slfroden is my alias on YouTube, BrickShelf, Flickr, etc). You already posted one of these videos before, but I guess it is hard for you to remember every single thing you post... In the top video it's says ' both rams fully retracted' when the top one is not. You are correct. It all comes down to resistance. The rubber belt adds resistance to one side of the differential, but in the video that I made, the rubber belt didn't provide enough resistance. It is easy to fix by either using a smaller belt, or adding a twist into the rubber belt (like in the second video). You want to be careful not to add too much resistance though, otherwise you might strain the motor or break the 12T bevel gears in the differential while trying to overcome this resistance. It was just a proof of concept, and I haven't actually used this technique in a MOC yet. Edited November 14, 2011 by Splat Quote
le60head Posted November 14, 2011 Posted November 14, 2011 Great idea! Could be very useful for selecting one of many different functions, powered by the same motor. Thank you for sharing! Quote
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