Friday, March 1, 2013

Project Weasel: Work Surface Angle Adjustment

The one unfinished task required to have a fully functional DIY art easel was a way to lock the work surface's scissor arm at a specific angle. With no pressing hurry to solve the issue, I let the problem percolate in the back of my mind as I went on to other things.

Letting things set has considerable value because our subconscious mind will make a connection with a solution when we least expect it. In my case, I was roaming through a hardware store looking for parts to build a light box for tracing when I saw a storm door closing mechanism. The light bulb of innovation went on. I grabbed one of the door closers and headed for home to see how it could be re-purposed to fit onto the easel. Too bad I didn't keep the closer from my old storm door as it would have functioned and saved me fourteen dollars. Oh well, such is life. Keeping too many things leads to packrat-itus syndrome as well as a huge mess.

Before I describe the retrofit, one thing I'd like to point out is that the photo does not have the easel's sliding work surface anywhere visible. I've removed it to simplify working on the angle adjustment. Earlier posts in this series show the sliding work surface.

Initially, I thought about placing the door closer on the inside of the A-frame but I didn't like the idea of reaching in between the pivots with my hand. Things have a habit of slipping at the wrong time and when your arm is between a heavy wood lever arm, well, bad things can happen. So I thought about ways to attach the door closing mechanism to the outside of the pivot arm.

The first few attempts failed. Initially, I forgot that the spring action only works one way to slow the closing of the storm door. Fail because of being oriented in the wrong direction. Okay, so I reversed the direction but the angle wasn't right and the closer's mounts were giving me problems. As the pivot arm moved through its range of motion, the attachment clamp wanted to break due to the lever arm twisting against it severely. A little creative thought fixed that problem by reversing the pivoting attachment mount and placing the cylinder in between the outer arm of the scissor pivot and the back support member of the A-frame. A quick trial indicated it should work so I attached the cylinder in place. It worked. The drawback is that there is only enough forward movement to allow the work surface to move from 25 degrees back to a vertical position. I lost the forward tilt ability but the vertical position is adequate for my needs so no real loss.

The first closer mechanism I tried releases its clamping action if the piston shaft is pulled forward. That's how the mechanism unlocks after you tap its latch. I had another closer cylinder that has a positive twist lock mechanism which is better for this design. Twist the locking ring one direction and the piston arm stops moving either direction, twist the ring back to its original position and the piston arm can move again. This ensures pulling forward on the pivot arm won't release the closer when it is not intended to happen. I swapped the closers after I took this photo but it's still mounted in the same relative location.

The second problem I mentioned is the fact that a storm door closer releases all resistance as the door nears its closed position. For doors, this serves to allow enough momentum to lock a door latches. In my case, it makes the scissor arm bang against the A-frame. It's mostly noise so again, I can live with it.

One last thing I decided to add was a limit stop for the forward range of motion on the scissor arm. As it stood, the door closer served as a range of motion stop for the arm. But I didn't like one single point taking that much stress so I added a simple cable loop that pulls tight as the arm approaches its full range of motion point. By attaching one eye-hook to the A-Frame and another to the scissor arm, I was then able to loop a plastic coated cable through the eye hooks as well as through a turnbuckle. The turnbuckle allows me to tighten the cable to adjust the stopping point. When adjusted, the cable assembly essentially ensures the scissor arm can never fall forward out of control if the door closer happened to break.

So there you have it. Excluding any additional tweaks to improve functionality, I consider this project complete and ready to use. I'm looking forward to taking some painting classes now so that I can make use of my new easel.

Ready to read more about project weasel? Here's the next post for the easel construction project. If you want to go back and see the entire project progress from the beginning, you can read find the first post at this link: Project Weasel.