Linear to angular motion

[zeppelin]

Hi Eurobricks Members,

I'm working on a project where I need to convert a linear movement to an angular movement. The model needs to be very accurate and also very robust.

I have been spending hours on prototyping a workable solution with gears, linear actuators etc, but none of them seem to be working good enough.

This is a image of the mechanics I'm having trouble with: max length : 15 studs, max height is 3 studs after the green dot and the red axles is were a medium/large motor is connected

The contraption need to be able to lift at least 300grams. Gears are slipping, gear racks are not working properly and Lineair actuators are interfering with the other parts of the model. (as there are not supposed to be sticking out lego elements when the liftarm has reached it's upper position, this means that all parts should be after the green dot when the liftarm has reached his 90°+ position).

I hope you guys will be able to help me out!

Thanks in advance,

Zeppelin

Edited July 6, 2014 by zeppelin

[Alasdair Ryan]

Would a simple arm operated by a worm gear work?

[zeppelin]

A worm wheel isn't accurate enough. It needs to be 'locked' in the 90°+ position. Tried a worm gear (8t) as wel as bevel gears, both are not accurate enough. A LA would be good, but I can't find a setup that the LA stays always horizontal between the 3 studs.

Edited July 6, 2014 by zeppelin

[Sariel]

I can't find a setup that the LA stays always horizontal between the 3 studs.

Would this help?

http://www.bricklink.com/catalogItem.asp?P=61905

[Alasdair Ryan]

Would any of these quick ideas help?

[zeppelin]

Would this help?

http://www.bricklink...tem.asp?P=61905

Mounting the LA horizontally is not a problem, but all mechanisms I tried lift the LA up a bit, like in a excavator. The LA/gear rack should always stay in the horizontal plane, but I haven't found a mechanism that provides this with the required movement. So, basically, that's what I'm like looking for. I guess I didn't make that clear enough.

EDIT: @ Alasdair: the second one looks good, although, I can't have any pieces behind the 'purple' one when it is in the show position (90°+ position).

Edited July 6, 2014 by zeppelin

[Alasdair Ryan]

You just need to add something to limit the movement,a small liftarm extending down ways and then hitting a connecter or beam should solve that issue (same thing will apply to when the arm is on its down position).

Edited July 6, 2014 by Alasdair Ryan

[zeppelin]

Alasdair: this is the problem with your setup. As the panel needs to be lifted +- 120°, we can't have any parts near the rotatingpoint. The second setup interferes with the white panel.

Any other ideas?

[Alasdair Ryan]

This should work.

[efferman]

fits this to you?

[Rockbrick]

sorry to be a pedant, but unless you are pushing the rack or using Pneumatics

you are really turning gears to make the linear motion to then give you the angular motion you need so you are really doing:

angular -> linear -> angular

[Captainowie]

It does sound like all you need is some linkage that keeps the linear actuator body from moving. Something very much like what efferman suggests.

Alternatively, as Rockbrick points out, you're starting and finishing with angular motion, so do you really need to use linear motion at all?

I seem to recall some Bionicle parts that are half gear half liftarm that might help with your mechanism clearance issues.

[zeppelin]

Thanks. Efferman's solution is working.