Society of Robots - Robot Forum

Mechanics and Construction => Mechanics and Construction => Topic started by: CoreyC on October 17, 2013, 11:24:54 AM

Title: Any links to info for raising/lowering an armrest about a pivot 1/4 turn
Post by: CoreyC on October 17, 2013, 11:24:54 AM
Hi everyone - my first post here. I'm a car mod enthusiast and just finished a custom audio install on my car.

My car has a shared armrest in the middle of the back seat, which pivots along it's bottom edge and attachment point like a vertical trap door. Behind the armest is a window to the trunk space (I cut out the metal, so it's a direct hole).

My goal is to be able to remotely actuate the armrest up and down. I've been trying to research ways to accomplish this, but I haven't found a webpage tackling a similar problem - I don't know enough to know if I need a servo motor, a DC motor...from there determining how big (I can calculate the min torque I'd need), or options for gearing the motor shaft to the armrest.

This is a new field for me - If anyone has any links to anything relevant that could benefit me I'd appreciate it. Thank you for your time.



Title: Re: Any links to info for raising/lowering an armrest about a pivot 1/4 turn
Post by: jwatte on October 17, 2013, 12:57:28 PM
A DC gearmotor with limit switches will probably work. A servomotor has additional sensors that let you emulate the limit switches, but also do more, so if you use a suitably strong servo, that would work. It probably doesn't need to be fast at all, so a very high gear ratio would be preferable.
There's also a safety issue -- you don't want the motor to be so strong that it will choke a baby who happens to be laying on the back seat when the button is pushed...

An alternative is a linear actuator with an arm that turns the armrest, but you may not have space for that within the constraints.
There are small, high gear ratio, servo motors that can probably do what you need, such as the Robotis Dynamixel MX-106. That servo also runs on 12V, which is good for cars, although you probably also want a TVS or other kind of "load dump voltage" protection.
The benefit of a motor with gearing is that you can mount it straight on the axis of rotation, which makes it less messy to install.
Title: Re: Any links to info for raising/lowering an armrest about a pivot 1/4 turn
Post by: CoreyC on October 17, 2013, 02:13:54 PM
Thank you very much for the reply Jwatte. Your idea with a linear actuator with an attached arm that I can try and slip into the armrest sounds great - it's what I had in mind. I've made a crude sketch.

You've given me a great starting point. I'll research some more and then remove the rear seats and check all the physical constraints I have to try and keep things as stealth as possible.

And I have a daughter on the way, so not choking her would be a good thing :)

Appreciate your time.