Gallery, Projects and General > How do I??
Electric motor question
Charles:
Surely the ideal design would be driven by a single actuator, no problems with maintaining even movement, no complex interlink mechanism?
A scissor lift style is out because you can't get your knees under it, but what about a cantilever design as found on a forklift?
An 'L' shape frame on the floor, with the upright part at the back, uprights consisting of two rails spaced, say, 500mm apart, a plate with 2 pairs of bearings sliding on the rails, with a linear actuator in the middle. Bench top cantilevered out from the plate.
chipenter:
Four 1meter lengths of 20mm studding with timing pullys , as in a mill knee .
AdeV:
Aha! One of the advantages of being a hoarder, is every now and then you stumble across something you forgot you had, which could prove useful....
In this case, a decent sized gear motor!
This is one of a pair of wheelchair motors I was given some years ago by John Bogstandard, so it'll be good to finally put them to some use (or one of them at least). I don't know how powerful they are, but they turn at about 60rpm @ 12v, which seems to be right around where I want the speed.I can always bump up the voltage ifI want to run them faster, for the length of time the motor will be running, I can't see it being a problem. There appears to be an encoder on the end as well, although why I am not sure, and there's no connectors to it. The two extra pins in the plug are not connected to anything.
I can remove the bracket and the clutch lever (I will simply leave it permanently engaged), and will weld up a bracket to hold it to the underside of the bench.
Apologies to any Americans out there, the rest of this post will be in French. To translate back to the mother tongue, simply divide by 25.4...
So, I've worked out that ideally I want about 600mm of travel, from around 700mm to 1300mm. I could possibly get away with less (which would also make any leadscrews cheaper), so I may settle for 500mm & start at 720mm (standard desk height) and only go to 1220.
Charles - one leg with cantilevers sounds pretty easy, and certainly a lot less "dieselpunk" than having a load of chains thrashing around under the bench... I do wonder though if it will be stable enough. I am currently anticipating having almost 3000mm x 600mm of bench (kitchen worktop) rising & falling. There's a 90 degree corner, but I'll probably fix that at desk height. Maybe fit a kitchenette there in case I can persuade the wife to come by & do some cooking :lol: :wack:). Also, I quite like the dieselpunk thought... I could put a camera at floor level to watch the mechanism at work :D
So, I guess another question would be.... what size threaded rod? I can pick up 16mm ACME threaded in 1m lengths for a surprisingly low price on eBay, 20mm costs a bit more but I'm wondering if the extra thickness would provide additional stability. Having said that, I do intend to use close-sliding-fit tubing, the outer leg will be fixed to the floor & the inner leg is what it actually sits on, the overlap should prevent too much side-to-side wobble, especially combined with the linear bearings. But would 16mm possibly bend under,say, a 200kg load (weight of bench+contents+me leaning heavily on it)? I think if I do Charles' idea of one linear actuator,I'll go out to a 30mm screw, that should be plenty surely?
AdeV:
PS: The other advantage of using leadscrews over ropes, is setting the initial leg height is dead easy: Just rotate the inner leg until it's firmly in contact with the ground. I'll probably turn up a small end plate which screws to the ground to prevent it from turning when the bench is raised/lowered, which will be screwed in once the height is set.
DMIOM:
Sussed it out - I can guess what you're up to! :ddb:
"Bed" rising on leadscrews = Z axis, then all you'll add later is a lightweight X/Y gantry above to carry as many printheads as you want => mega-3D-printer!
:proj:
Dave
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