@strwbrrymnst_2347578 Hooks on the outside edges of the Collar is a great idea. There should be space to have an upper hook and lower hook, giving options for tension using the same rubber bands. I'll need to see if there's any unintended interference between the new rubber band position and the Pin, but there's potential in your idea. Thank you!
@marimolabs Now I love the design even more. Stupid me printed the legs with support inside, so I could not store the pins in the legs, hence the stowing option was not so important anymore and I did not give it more attention. I just figured it out with the guiding and interlocking. Nice!
How about putting the hooks to the vertical edges?
So far we used up to 6bar (~90psi) of loading pressure. Worked fine with the setup.
For the legs, bumps were also my first thought. Best way to avoid additional components without compromising rigidity. Looking forward to it.
@strwbrrymnst_2347578 Thanks! Very helpful.
- Legs: I like the idea of the leg locking; multiple positions is an interesting idea. I've thought about putting spaced grooves on the Leg that mate with a bump in the Base. This may be feasible in the next big revision. I'll have to ponder whether it's feasible to have Legs that are adjustable in this way but don't slip on launch.
Historical context: Base was initially designed for 21.4mm OD PVC pipes and the current printed Legs v1.0x had to maintain backward compatibility. Depending on print tolerances, the Legs are sometimes too tight or too loose in the Base. The last year has demonstrated good reliability with printed Legs, such that I think it's now reasonable to remove PVC pipe leg compatibility in the next revision. This allows better optimization for locking Legs and simplified Base geometry.
Rubber bands: Can I ask what launch pressures you were using? The design attempts to allow for a wide range of pressures, from fun launches with children to controlled-setting physics experiments. A recurring design challenge has been ensuring a clean release at higher pressures (some people have doubled the rubber bands) while not having the loading force be too high for younger rocketeers (as you were experiencing).
Your approach of rotating the Collar 60 degrees and moving the rubber bands is clever. It sounds like you're not using the Leg stowing functionality much, so having the Collar rotated isn't causing issues.
Perhaps we could have several hooks/mount locations for rubber bands (e.g. use here for <40psi, here for >40psi), or recommend different rubber bands depending on the launch pressures (e.g. #19 rubber bands are half as wide so provide less tension).
Love the feedback. Thanks for taking the time to share!
@marimolabs I was a bit annoyed by the legs which kept falling out of the base when I moved the setup, from the table to the lawn or in my office. (minor problem) But for sure it would be nice, if there was something like a spring putting some tension between the leg and the base. Even nicer would be to have the legs be able to lock in on different positions to compensate slope on lawns like mine. Probably overengineering though.
I used the exact rubber bands as described in the manual. I found them to have too much tension when going around the base leg. the kids were not able to "load" the jig themselves, so I took them off to have them go straight down to the horizontal beam of the base as can be seen in the picture. Now it works good for me/the kids. However, some hooks for the rubber on the beams could be another minor improvement.
But again, awesome project. I especially apreciate you following up on comments. (edited)
@strwbrrymnst_2347578 Great! Please feel free to share any improvements or problems you ran into. It helps me improve the design further.
Awesome model. Minor points to improve.
But most importantly: The kids had a ton of fun, so did the adults :D