DIY - Height Adjustable Desk questions (sitting desk and standing desk)

[ziegler]

(   this is the project that I'm trying to copy  http://www.instructables.com/id/Electric-Height-Adjustable-Desk/]http://www.instructables.com/id/Electric-Height-Adjustable-Desk/   )

I just heard of the growing problem, that we are sitting way too much and it can give us a long list of health problems.

Been trying to use my normal desk as a standing desk, I really like it so far.

So I looked around for DIY projects that could make something similar to what I wanted.
Did find a lot of different solutions for it.

(this one is also cool https://youtu.be/ZjMu-SBudsE)

found a cool easy design that looks do-able.

but here comes the part I'm unsure of (pushing mechanic):
- The design has a normal wood desk board, with 2 legs and some kind of pushing mechanic.

this pushing mechanic will need to:
- be able to, move about 50-65 cm (19,69-25,59 inches)
- be powered by some kind of small power-supply.
- be able to withstand a load at about 50 kg or more.

But this is something that I don't really know much about, since there is a lot of different kinds of mechanic-parts that can be used here:
- piston (magic?)
- gas powered piston
- hydraulic controlled piston
- linear actuators ?

what is the best choose here ?
(cheapest ?)
(most obtainable?)
(best performance?)

the piston will need to be somewhat affordable.

(
here are some other projects:
http://www.instructables.com/id/Convertible-StandingSitting-Desk-for-200/
http://www.instructables.com/id/Scissor-Bench-Adjustable-Height-Motorized-Workstat/
https://youtu.be/YJVjQ0Bl9y8
https://youtu.be/LIODjQH0NhI
https://youtu.be/A6cfamnqB2I

could be usable for some.
)

[jeroen79]

The desk in your first video has a handcranked scissor lift mechanism.
You could make something similar but instead of a handcrank it could be powered by an electric motor that drives one or two jackscrews.
The motor can be controlled by a simple switch forming an H bridge.
Possibly you could add switches to interrupt the motor at the mechanical limits or at the desired deskheights.

How powerfull such a motor would need to be would depend on how much weight you want to lift and how fast you want to lift it.
You can workout how much force will be applied along the jackscrews at a given height.
If you add a counterweight you can decrease the the amount of weight (not mass!) the motor has to move.
By adding reductiongears you can increase the torque on the jackscrews by running the motor faster.
High rpm reduction = high motorspeed = low motortorque and vice versa.


Hydraulics and pneumatics will either be handpumped or will need a compressor which will need it's own source of power.
Both can lead and a hydraulic leak will be messy.

[rs20]

You could go to aaalll this trouble to make a variable-height desk. Or, you could just get a tall chair so that when you sit on it, your head is at the same height as when you are standing. Then you just get a fixed-height standing desk, and you're done. Concerned about where your feet go? There's a ring on the chair; or you can have a box on the floor that acts as your false floor.

e.g. http://notsitting.com/standing-desks/making-the-switch/standing-desk-chair/

[David_AVD]

You could go to aaalll this trouble to make a variable-height desk. Or, you could just get a tall chair so that when you sit on it, your head is at the same height as when you are standing.

+1 to this.

All the benches at work are high enough to use when standing and we have drafting chairs to use when seated.  I like to work both ways and this is a simple solution.

[ez24]

My standing desk is 3 plastic storage boxes stacked for each corner (12 total) and a piece of 3/4"  x 4' x 6' piece of wood sitting on them.  It is stacked full of test gear and computers and has held up now for 5 years. 

For my sitting bench I am using a Costco 5 foot folding table ($50) with Costco plastic shelves ($30 each) at each end and planks going across the folding table as shelves over the workbench that are supported with the plastic shelves.  A lot of shelve space for little money.

But it would be cool to press a button or crank a handle.

[pickle9000]

I screwed a 24 inch stool to a 6 inch lightweight platform. It has an overhang on one side to place my feet. Works fine but I hardly ever use it. This is for my computer workstation, my electronics benches are over-height (but not for standing) and work with a 24 inch stool. 

[tggzzz]

There are height-adjustible work surfaces designed for elderly people with limited mobility. Might be helpful if you would prefer not to have to make it yourself.

I've seen them at a local charity/shop/advice organisation, but they don't have an online catalogue so I can't provide a link

[cs.dk]

So I looked around for DIY projects that could make something similar to what I wanted.
Did find a lot of different solutions for it.

Is it worth making it a DIY project? I don't know where in DK you're from, but this height-adjustable table is given away for a bottle of wine. http://hi-speed.dk/2phpBB/viewtopic.php?f=12&t=116132
Anyway, you can use the actuators, if the design doesn't match your criterias.

[ziegler]

Is it worth making it a DIY project? I don't know where in DK you're from, but this height-adjustable table is given away for a bottle of wine.

That table could be nice too, but it can't fit in my room, that is also the reason why, I want to convert my normal desk to something that can be both, without it changing my current furniture setup.

The desk in your first video has a handcranked scissor lift mechanism.
You could make something similar but instead of a handcrank it could be powered by an electric motor that drives one or two jackscrews.
The motor can be controlled by a simple switch forming an H bridge.
How powerfull such a motor would need to be would depend on how much weight you want to lift and how fast you want to lift it.

First I wasn't so glad of the idea, since I can't know if the setup could hold all the weight.
Or if I could make it, since it is a little my advance than what I was thinking.

But then I made a 3D model of the project and saw how unsecure the design was, when you compare it to the scissors model.

I have seen setups in this style that use one linear actuators.

Then today when I was throwing away my garbage in my neighborhood's local garbage-room, there I found one of those bed-motors used for back and foot bedding, and one of the BIGGEST motor I have ever seen in person.

With these I can cut costs, by using one of them in this project.

[ziegler]

the bed motor (dewert duo 5, from 1995) has the added value of having a remove with it, so I just need to make the right setup for it.
https://www.google.dk/search?q=dewert+duo+5&biw=784&bih=771&source=lnms&tbm=isch&sa=X&ei=qdlhVbS7HcGdygOPuIH4Cg&ved=0CAYQ_AUoAQ
Have tested this one, and it works just fine.

the big motor on the other hand, has a lot of extra hardware to it, that I'm not sure works or how to use.
Also I don't know if this motor work.

[ziegler]

the type cannot be seen, I can only see a "e x" in the type field.
it has an input voltage at 24.

it is a "Besam Unislide Motor Gearbox", i think so. I found it at ebay for $386.60
 http://www.ebay.ca/itm/Besam-Unislide-Motor-Gearbox-Assembly-GUARANTEED-/121625509227?pt=LH_DefaultDomain_0&hash=item1c5171fd6b

[jeroen79]

First I wasn't so glad of the idea, since I can't know if the setup could hold all the weight.
Or if I could make it, since it is a little my advance than what I was thinking.

But then I made a 3D model of the project and saw how unsecure the design was, when you compare it to the scissors model.

Wether it can hold the weight depends on how sturdy materials you choose.

With a bunch of math you can analyze how the forces are distributed.
http://www.engineersedge.com/mechanics_machines/scissor-lift.htm
https://andreacollo.wordpress.com/2012/09/18/scissor-lift-jack-equations/

Design for a higher weight than expected and add some extra tolerance to the parts and things should be fine.

[Dave Turner]

It's less complicated, and cheaper, to follow the suggestion of having your bench at a suitable height to stand at; and then have an adjustable height draughtsman's chair for when you want to sit.

This also allows the the bench to be designed to allow you to get your knees underneath and to brace the front legs with a cross member acting as a foot-rail.

The only disadvantage is the extra height that you need to lift heavier components higher onto the bench.

[David_AVD]

Exactly.  A fixed height work surface will always handle weight better and be more stable than an adjustable one.

That said, maybe the OP really wants to build an adjustable desk for the "coolness factor".

[rs20]

Exactly.  A fixed height work surface will always handle weight better and be more stable than an adjustable one.

Always? What about a hardwood panel bolted to a forklift? 

[tggzzz]

Exactly.  A fixed height work surface will always handle weight better and be more stable than an adjustable one.

Always? What about a hardwood panel bolted to a forklift? 

Oh, I think you could make an argument for "always", provided you restricted the choices a little more.

But who cares?

An engineer would always want a significantly more stability and load capacity! And wouldn't care one iota if it was better by a factor of 1000 - if the original was sufficient.

After a glass that is 50% full is neither half empty nor half full: it is twice as big as it needs to be,

[jwm_]

Exactly.  A fixed height work surface will always handle weight better and be more stable than an adjustable one.

Always? What about a hardwood panel bolted to a forklift? 

Klaus might have some issues with panels on a forklift.

https://youtu.be/-oB6DN5dYWo

[ziegler]

Wether it can hold the weight depends on how sturdy materials you choose.

With a bunch of math you can analyze how the forces are distributed.
http://www.engineersedge.com/mechanics_machines/scissor-lift.htm
https://andreacollo.wordpress.com/2012/09/18/scissor-lift-jack-equations/

Design for a higher weight than expected and add some extra tolerance to the parts and things should be fine.

Thank you for these links, just what I needed.

I have reach the math now, and I not sure I get any of it.
But I found this cool calculator.
http://www.engineersedge.com/calculators/scissor-lift-bottom-loaded.htm

I'm unsure what weight measurement it use, and how to convert Ry to Kg.

[ziegler]

I'm kind of close to finishing the design, but I'm not sure how I can get the motor to turn the screw, just as the handle does (from this video)

https://youtu.be/vJH1QLGeklc

[rs20]

.
http://www.engineersedge.com/calculators/scissor-lift-bottom-loaded.htm

I'm unsure what weight measurement it use, and how to convert Ry to Kg.

The units are kg throughout -- as long as you consistently use kg
 Or, they're pounds throughout, as long as you're consistent
.. Etc etc.