Double threaded rods lift

[Anonymous No.1599213]

Hey /diy/

>Metric system thread

I'm trying to make a standing desk which goes from 60 to 130 cm. Therefore I can't use a single threaded rod to lift it (cause 70 cm range doesn't fin in 60 cm minimal height)

I think I'll make something like pic related but I don't know how to transmit the rotation on the 2nd rod (red square), since it has to rotate with the 1st rod but also slide along it.. Any idea ?

I hope my drawing is clear enough

[Anonymous No.1599219]

Maybe a worm gear on "main" rod and a 90 deg gear on the 2nd rod would do the trick ? But the ratio would be gigantic

[Anonymous No.1599220]

>>1599213
That is a bad design but I'll entertain you for five seconds.

Have one rod rotate and fix the nut, then have some kind of belt transfer that rotation to the nut of the other screw, but fix the screw so it doesn't rotate. You'd have both nuts in the same level, but one stationary and one rotating.

[Anonymous No.1599223]

>>1599213
Fix the motor and both nuts to the middle section.
Top of rod 1 to top of top section
Bottom of rod 2 to bottom of bottom section

[Anonymous No.1599229]

>>1599213
stupid question, buy why not have just 2 rods at the back, inside square tubing with bracket/support mechanism for the front?just hide the 2 supports behind either 2 wood columns or just a back across the entire desktop with shelves/pegboard/mounted light at top, powerstrip etc? also gives you a better cord management if you center all your wiring, hiding behind everything at a mid height so there is less hanging wire as height changes.
If you are putting at wall, minimal bottom support is needed if you anchor it at a stud. If you make it even higher ranged, you could have it completely raise to be out of the way when not in use (if high enough to sit under entirely, it gives you more open space in the work area, like workbenches that fold up/down against the wall, but moving up out of your way instead)
(pic related 2 hours in crayons on napkin)

[Anonymous No.1599233]

>>1599220
Belt isn't reliable enough

>>1599223
Good idea but I can't. there is a risk with the wire getting caught in something (the need to be hidden inside).

I came up with this design, seems good enough right ?

[Anonymous No.1599234]

>>1599229
I have no walls or stuff to hide it. My desk is floating in the room.

>>1599233
Woops, messed up. Redrawing

[Anonymous No.1599236]

Don't get stuck on a certain mechanism.
Separate the goal from the method. That's a major engineering failure in many DIY topics.
Your goal (based on your limited post) is to raise and lower a desk, not driving things up and down a rod.
You can also use things like a gear on a toothed track with a locking mechanism being a solenoid pressing against the track that only disengages when power is applied to the motor to raise or lower it. Or scissor lift like mechanisms you can find on work carts or furniture.
(Pic related, another interesting mechanism, is example of how high end tables expand equally on center to add leafs. you can add more "tracks/rails" to something like that and have something that expands out more than twice its original collapsed size.)
If you are really stuck on telescoping legs,look at how extending masts for portable ham antennas or flagpoles work: cable with pulleys and several nested tubes

[Anonymous No.1599237]

>>1599236
Can't drive this with stepper. It requires too much torque.

Here is the correct drawing

[Anonymous No.1599238]

>>1599234
it can still be free standing in the middle of a room using that method but with good base support if you aren't using it from all sides like a table. nothing wrong with a desk in the middle of a room that has 2 corner pillars.
And since you just need a short distance, you could just have something like a backsplash just sticking up at the back to cover the rods or mechanisms to give your extra 10cm+. There are plenty of desks that are made with something like a really short hutch/ shelf at the back.
Basically, I'm just saying you don't have to have drive mechanisms on all 4 corners if you just drive it at the back and build it sturdy like those desks on frames that look like the letter U on its side

[Anonymous No.1599249]

>>1599237
I didn't see the requirement to use a cheap low torque stepper motor anywhere.
Are you actually intent on constantly driving the motor to use the braking? You'll burn it out.
If you can't use a regular motor with a simple switch like usual, which would be good enough for most styles of movement or lift mechanisms, because you need it to be automated to precise heights within millimeters and the height always known to some control logic, you can use a regular motor with an encoder wheel. Or even a spring retracting cable going through a pulley to measure height.
Power windows on cars are another heavy duty lift mechanism where the travel distance is longer than the area of the drive mech.

Regarding drawing, a gear moving up and down on a powered shaft and off axis forces without binding, lots of play and backlash will require proper design with heavy bearings and relatively tight tolerances. That drawing shares concepts with early transmissions.
And chains always beat belts and you can order all kinds of sizes of chains/gears or steal them off all kinds of scrap shit.

[Anonymous No.1599252]

dual drive screws side by side. Drive one screw by motor, the other mounted to stay stationary. Connect drive nuts from each screw by gear or chain. Once the drivenut on the motor driven screw hits the end stop, the nut will rotate with the shaft and rotate the drive nut on the nonpowered screw and that drivenut will then move along that screw.
Should be easy to figure out from there.

[Anonymous No.1599266]

I think i'll do this with pulleys and steel cable (red in drawing). Much cheaper and simpler

[Anonymous No.1599278]

why the fuck wouldnt you just pin it

have the legs able to telescope and you just lift and slide a pin in to hold it at whatever height

[Anonymous No.1599281]

>>1599278

Cause I want to it to be electric.