# Rotation of a Screw

I want to start a simple project and need to see it's feasibility (and complexity in case)

As you may see in the photo

I have a rotating handle (yellow thing) attached to a screw

My idea is to create a computer system, that can move back and forth that rotating handle (with or without the handle, I don't mind).

What I think I should start with, it's with a Servo Motor that somehow, I could attach to that handle.
I'm not sure how to measure the Torque needed (it's not a big number, but it's not a very low torque either).

Maybe there are some similar projects to orientate me. This is my first project in arduino and I would like to see if there is a nice start.

SirLouen:
I'm not sure how to measure the Torque needed.

Use a torque wrench?

What's under the yellow handle, ie what's the end of the shaft? A square that you could put a socket on?

You will have to measure the torque required to turn the shaft in order to pick the right (geared) motor.

One way to do that is wrap the shaft with fish line or string and hang a weight to the free end of the line. Add weight until the mechanism is driven. torque=force x shaft radius.

kenwood120s:
Use a torque wrench?

What's under the yellow handle, ie what's the end of the shaft? A square that you could put a socket on?

I can't pull that handle... it seems glued to the screw. I'm still trying to figure out how to remove it without damaging it.

jremington:
You will have to measure the torque required to turn the shaft in order to pick the right (geared) motor.

One way to do that is wrap the shaft with fish line or string and hang a weight to the free end of the line. Add weight until the mechanism is driven. torque=force x shaft radius.

I was thinking in some kind of tool to measure this. Because it will be really difficult to calculate the weight needed in horizontal position, unless I use a pulley or something (too much hassle i believe!). Do you know any tool that makes the trick?

I was thinking in some kind of tool to measure this.

That tool would be a torque wrench.

jremington:
That tool would be a torque wrench.

The problem is that the digital torque wrench it's only intended for screw threads. In this case, I have to grab the handle and I'm not sure how (I would even have to grab it for the rotation with the servo, and still thinking how i may accomplish it)

So now essentially I have to see how to remove that yellow handle to see if there is some type of socket inside it

Fasten some sort of an arm (wood stick or something) to the knob (lots of tape might work to fasten things) - then put a string on the end of it and use a fish scale or some sort of scale to measure the force needed and then do the math with the length of the lever arm - not as exact as a fancy digital torque wrench but should work. Remember you are just trying to get close then add a bit of a safety factor to things

Also the knob has ridges so some sort of a clamp might be better to fsten things together

Even if you can’t get the knob off, there is that small bit of exposed shaft below the handle... you could attach a clamp to extend your new actuator arm out, away from the shaft/knob diameter,
.
Remember that increasing the diameter of your rotation reduced the torque required to move the shaft.

Also - important question, How many degrees of roration do you need?
This could significantly affect the method to drive the apparatus.

SirLouen:
I can't pull that handle... it seems glued to the screw. I'm still trying to figure out how to remove it without damaging it.

Cut the shaft just below the handle, throw the handle away, and machine the shaft square to take a socket.

lastchancename:
Remember that increasing the diameter of your rotation reduced the torque required to move the shaft.

No- the torque's the same, the force is less.

It looks as if there is grubscrew or rollpin in the handle - can't you unscrew it / drive it out with a drift?

Allan

SirLouen:
I can't pull that handle... it seems glued to the screw. I'm still trying to figure out how to remove it without damaging it.

I was thinking in some kind of tool to measure this. Because it will be really difficult to calculate the weight needed in horizontal position, unless I use a pulley or something (too much hassle i believe!). Do you know any tool that makes the trick?

Right in the picture you showed, the handle has a set screw holding it on the shaft.

Clamp a lever onto the shaft (vise grips or pipe wrench) and feel how it turns. See what weight is the same to lift. With that and the length of your lever you can get a ballpark estimate that's as good as you you are careful. With that, double the number and get a motor at least that strong, it will work.
The tools that make the trick here are some knowledge and perspective.