My New Linear Actuators are SO MUCH BETTER! | PDJ #21

🚀 Hey Jugglebot Enthusiasts! 🤖 I'm thrilled to finally share this update of the actuator journey with all of you! Your insights, curiosity, and passion have been pivotal in this progression. If you were designing this actuator, what would YOU do differently? Or better yet, if you could see one feature or capability added to these actuators, what would it be? 🧐 Don't forget, if you want to learn more about the project, or to lend a helping hand, check out our Zulip site, here: pdj.zulipchat.com/

For the bearings, I would suggest a delrin or Teflon roller. You can get a pack of these easily, marketed as 3d printer rollers. They would stay on the bearings better, resist abrasion, and have a self-lubricating effect with the tubes. For the synchromesh cable, you may be able to design a clamping plate similar to those used for bike cables.

Is it just me.... or every time I watch video of this guy I say: "I really like this guy". Awesome project! very good idea and straight to the point!

It's a great design. You should also measure the force you can apply in extension - the opposite of your weight lifting test.

It's been a treat watching this be developed! Some suggestions for future testing: - Conduct endurance testing while the actuator is (reasonably) loaded, to better match end-use conditions - Implement multiple load cases into the motion accuracy test (and record deviations in both absolute and relative positions with each move). Under a single constant load (or no load) the stiffness largely "disappears" since the parts' deflections under stress are not really changing. In the final application, the load will be constantly varying and this may have a large effect.

Regarding terminating synchro mesh cables: You could probably create a part with an internal "thread" that matches the cable. Perhaps create a two/three piece part that can be pushed onto the cable and match its shape. As the pieces are forced together with the cable between, they'd pinch the cable and hold it tight. Then you pinch that part in a collared holder that prevents it from slipping out and provide pressure to keep the cable captured. Very hard to explain, but perhaps you get the idea. Not sure if it'd stand up to the tension, but it probably could. Let me know if you want me to elaborate and produce diagrams!

I love the cable routing. Flipping the motor 90 deg may be better and less complicated, but I love complicated mechanisms. It just looks awesome

Super cool project! Immediately got a couple ideas as well. Sorry if these are already named, but here we go: - Route the extend and retract spring via the same wire, so kind of get a capstan drive. - Make the sleeves for the inner bearings slightly concave. to make them self align to the rod? Maybe also make a groove in the middle of them to make a channel for the wire, to turn that issue into a feature. It might remove an extra bearing for routing the wire. - Make the moving bearings three sets at a 90deg angle, to get a kind of rollercoaster setup. - Add a fan to the output shaft of the motor, that spins a cooling fan over the brake resistor. Well now that that's out in the world so I don't think about it again, good luck!

For the cables pulleys You can absolutely do the compression with 2 pulleys : Use the first pulley to first route the cable throught any point of the desired destination line, and then put a pulley at that point to get the destination line First step is always possible due to a point and a line always being in the same plane, and same for 2 intersecting lines in the second step Good luck with your project

Regarding the MBS of that string, you're going to get something closer to half of that once you tie a knot in it.

Hello stumbled into the video and the topic pulled me in. Retired Engineer in Medical, Automation and Robotics Systems. You do a great job of scientific thinking and setting goals. We used a Small Stewart Platform to shake test medical Data collectors in Scanners. It was amazing as we rolled through the frequency scale how bits would actually start to vibrate so much we could only see a blur where the part was. We added braces and stiffeners and in the end it improved our end result significantly. The advantage of having access to Aerospace folks to help. We also used Carbon Fiber for patient support to keep them nice and still. Later i used Carbon Fiber to build robotic arms, Large ones for Defense manufacturing, we added active and passive vibration dampening to get long arms with heavy grippers to move fast and stop without rebound. I appreciate what you doing and how you are doing it but still unclear what gizmo is doing. oh and this work i mention was done in the late 70s and early 80s. Maybe you were born after that time. Keep it going troop you are educating as well as fixing your machine. We had to know position as well so we added a rotary counter on the motor to feed a location calculator. Have fun and keep up the good work. Dennis another thought on the center Round Shaft. I used a square Shaft on one device, machined two corners opposite each other and a three V shaped rollers to capture the shaft and maintain alignment with lowest drag. Those were all metal. I was surprised to see you running metal bearings on six sides of resin cured Carbon Fiber tube. The resin will require some compliance as you have learned. We found Delrin worked well it is machinable and robust with some compliance to prevent damage to the resin surface of the composite tubes. D

What an excellent project update. I love the collaboration happening, thanks for sharing.

For your linear bearings, a lot of newer industrial bearings use metalized ceramics. Systems that used to be rows of ball bearings on hardened steel rails have become ceramic sleeves which fit snug to the rail. I don't know if that applies to carbon fiber tubing, or much for your project - but a good lool at linear bearings might give you some ideas for how to stabilize your tube. I would even recommend going with some kind of graphite coating on the rods that can act as a dry lubricant. An oil or grease probably won't fit the application well, but can make a world of difference in longevity. Gears that run for decades with oil in them won't last a day without it. A little can go a very long way. You could look at just trying a teflon sleeve or set of pads that form to the wall of the tube. Play around with contact area and pressure to get what you need. The resin binder for the carbon fiber is probably going to be easy to wear. You may want to consider adding or trying to identify tubing made with a harder material. A silicon dioxide coating may improve wear characteristics (or perhaps an alumina spinel - quartz/saphire coat). If you want to go aerospace, you could try a sputtered titanium nitride coating. Not sure how well (or horrible) it would fuse - but if you're looking to go off the wall with it - that would be a direction. For the string, you might actually look into amarid/kevlar. The nomenclature to use is "tow" when looking for strings of fabric material (same with carbon fiber) - I spent days losing my mind looking for a carbon fiber string because I didn't know that was called a "tow". Well - a tow is unbraided, so I suppose not technically a string/line. You might look at fishing lines for off the shelf solutions and even talk to those communities about line routing.

Super glue probably doesn't stick well to TPU. Scotch Weld PR40 adheres very well to TPU. You could also print the TPU sleeves to be concave on the outside so they are self centering

The TPU sleeve over the bearing will work way better if you design them to fully engage with the surface area of the carbon fiber tubes. Make them like a circular indent like doing a sphere revolve cut in your cad program where the sphere is the same size as your carbon fiber rods. It will also help hold them centered if you add a bit either side of the bearing on the flat side that helps lock them in, like a U shape that comes down about a millimeter from the outside diameter of the bearing towards the center of the diameter. Hope this helps. 👍👍

This is awesome! I'm so glad to see your progress!. This is awesome! I'm so glad to see your progress!.

I once took apart an old photocopier and it had a steel cable moving the photocopier head around, so i think you might have some success with steel cables rather than nylon/other. And it really did surprise me how supple the steel cable was, so there might be some specific type of cable for applications like this.

You should look at 1-1.5mm Dyneema rope for your cable, very light, very flexible, very strong, low friction, low elongation/elasticity and easy to splice to create loop or termination

It’s a shame I’ve only just today discovered your channel, your communication of your development process is very inspirational to me!

High tensile threads need real care in end termination; if you create a good load sync with a gentle bend radius you'll be able to get the MBS. Try using a boss at each end with a number of "dead" wraps which will distribute the load into the thread. If you use the thread as one continuous wrap you'll only need two ends as well. You can eliminate one bearing by aligning the bearing to the tangent of the drive drum as well. If you put a counter rotation feature in the fixed end you won't have to pay the weight in the moving end as well ;)