I am in the process of putting together a machine based upon Sandy's design and have a question about the gondola. In the video of its assembly, it appears that two of the three bearings are used as actual bearings (so the cable can move in relation to the pen; however, the third bearing appears to be just a space to keep the other two a little bit above the stabelizer platform (big circle).

Am I correct in my understanding? Why is a space needed/desired?

By being a bit crafty, you can get away with just one bearing, as I have. Ofcourse its still untested (waiting for the motorshied) so this could turn out to be a bad desing, but I have high hopes in it. Just over 0.5kg so brobably wont be needing any extra weight.

And first post, hi to all 🙂

Hi, Kumpari! Very cool looking design.

Sandy, thanks for the feedback. Your comments helped me understand your design criteria.

I could't find the brass tube in stock locally, so since I have a Sherline lathe, I machined a small piece of brass to friction fit the bearings and a decent fit to either of the pen types I plan to use. The nice thing all that exfras work provided is the tube is heavier (a little less than the bearing's weight) but also thick enough to add two set screws for holding the pen.

I have laser cut parts on order for the gondola using your design, but I started playing around with designing a 3D printed one that can avoid the third bearing, yet still place the cord in about the same position. It all incluldes mounting bracket for a lift servo as well as guide pins for the servo cord.

As soon as I finish verifying it works I will post the design files for this:

For the first time in ages, I had some time to play this weekend -- all work was getting Kongo grumpy! >:-(

I did some more plateless gondola experiments. In contrast to the wonderfully "Terminator"-style gondola pictured above, I tried to remove as much mass as possible from the gondola. Pen/surface friction mixed with the gondola weight results in wobble when there's no stabilizer plate, so I wanted to work on the problem. Since the plateless gondola is for surfaces other than paper, such as glass/acrylic/varnished wood -- y'know, smooth surfaces on which the ink doesn't dry quickly and the gondola might smear the lines -- I'm less worried about the friction.

So I removed all the weight I could, and printed a plastic ring that goes around the gondola tube to act as a bearing. Over the bearing goes a string attached to a weight. The string is attached to a bottom corner of my board, goes over the gondola tube/ring, and the other end with the weight runs over a bearing at the other lower corner. So instead of a "hanging V" style drawbot, it now looks like an "X".

It works OK, but I'm not sure the benefits outweigh the hassle. There are problems:

• The board can't sit on the floor, because the new weight has to dangle below it
• The setup doesn't work as well at the sides of the board, especially near the bottom corners.
• It's meant to be used with a nearly vertical setup, but doesn't push the pen toward the surface (the string only pulls the gondola downward).

I'm not sure if I'll continue playing with this arrangement or not. I'll definitely need to build a new board first (one that's lighter, so that it can be placed on something easel-like).

Good to see new blood in the forum, and people fabricating new gondolas!