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BB Ratchet 0.3

by Corona688 Dec 19, 2013
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crazy cool design!
does it matter that the sprag5 is slotted and the sprag6 hub is not slotted??
i believe the slotes are for springiness. is that not needed??

and in the video you show the slotted hub. can you make a video showing the unslottted hub?

That's a relic of an earlier design. It's certainly not needed, probably not desirable, and not that springy anyway.

Great, simple design. I keep a bunch of various small steel ball bearings and the only one out and within reach was an unopened pack of the exact size. Good omen. Anyway, if you're okay with it, I'd like to use this mechanism for a new attachment for a system I designed which allows people with very limited hand strength to perform most all of the tasks that normally require strength to apply force, some level of dexterity, and the use of fingers. Its a band that goes around the middle of the hand and then there are custom attachments to hold onto various objects so they cant be dropped plus a variety of specific shapes which serve to apply all of the types of force that a normal hand could do without any position or muscular interaction. With your design here, I can attach a screwdriver head so that people using the system can screw and unscrew things with a repeatable single direction of motion.

I give away all of the designs and parts of this system for free at a rate of 30-50 sets monthly depending on how successful print sales went that month. I'll never charge a dime to anyone for this and will make a good faith best effort to provide these assistance prints to anyone who asks for them no matter how many people ask and regardless of my monthly plan or distribution strategy. If there's a reason why you wouldn't want this design used, I'll honor anything you decide and can send you the .STLs to other parts as I develop them prior to putting them up here if you want.


As long as you post the designs I'd be happy. With a noncommercial license you're in your rights to do as you wish as long as you don't sell it but if you post your designs I'd be thrilled.

Ill post the part using your rachet design immediately after i get a print that i would put my name on. Probably before Wednesday, and ill certainly link it to your work. I got a very high quality print from your file just as it came on the 2nd attempt. The first print with two shells (Im using Simplify3D) left some cosmetic flaws on the top and bottom, so i added a third shell to those faces only, and the results were perfect. Ill throw up a photo when i get back home.

Ill eventually get to posting all of my work- its just an issue i have with putting my name to work that has obvious room for improvement. As my talents lie in other areas, ill never come close to your skill level, but i come up with a ton of ideas. To give you a more full picture- i spent two years planning and refining a business model where regular 3D Printers can get going for less than $2000 to go full time out of the gate or for well under $1000 (currently the minimum ive come up with to be able to accept most orders is $650ish. Without putting up 10-15 pages, the plan revolves around focusing on the local area where you live and growing a reputation as a positive force for your neighborhood while in business you adhere to a standard for honorable motivation, honest practices, and for demonstrating not only genuine care for the customer and a fierce commitment to product quality. Rather than putting money into advertising, i go to local retirement facilities and physical therapy places, etc with boxes of prints which make people's lives easier or help lessen the burden of a disability, etc and spend a couple of hours telling people about the amazing new tech of 3D printing and showing folks how to get the most out of all of the free prints you passed out. I planned every detail, conducted dozens of surveys and interviews and filled up 8 notebooks which i distilled down to two books worth of the best ideas. I opened up full time on 1/1/18 and while ive been building, modifying, and printing for six years, i took a stab at following this business plan for all of my income. After two and a half months, ive simplified the plan in many ways and eliminated a bunch of things that i planned to always stock while adding some capabilities (like copper electroplating for a real metal surface thats both cheaper and far superior to the metal dust filaments like Bronzefil. I base the size of the monthly (now divided into two times a month) free print distribution on using the same amount of filament used to make the prints which i sold. I try to pick the most useful print that is easy to make and makes a lot of items. This month ,thisgroup of prints which im trying to improve have been requested by the places i had planned to go as they heard about them from last months group. The one crucial rule and the two exceptions to the non-profit printing are that every item that leaves my shop is held to the same standards of quality. I never cut corners or skimp on infill, etc. I consider giving away free junk worse than not giving away anything at all. The exceptions are that any print which can be helpful to a military veteran (i did my 4 years) gets immediate priority over all jobs, even paid work, which is listed on my sale contracts. Finally, if someone approaches me with a genuine need that a 3D print can help, they deserve my best attempt to help them in a reasonable timeframe and regarless of whether or not they can pay and if an offered payment would cause them difficulty, it shoulnt be taken or if the work was massively labor or material intensive, no more than the base cost of the filament should br charged. Honestly, with the price for a kg roll and the number of prints you can get out of a roll, the financial toll is miniscule. Last month i ended up printing 4kg of free items and there was enough that every resident at the facility got all they wanted and i still had dozens of items left.

Long story short, when i get all of the wrinkles worked out of the business model and all of the strategies, prints to bring when meeting business clients of many types, types of customers and the common issues with explaining 3D printing to unaware people have all had a real life trial, i intend to give the plan away to anyone under the conditions that they genuinely intend to start their own business and they agree to abide by the standards of honesty, integrity, and commitment to quality that are called for. So thats the full background on why im asking around to use parts of designs for non-commercial purposes. If you get a chance, let me know what you think of positioning 3D businesses as small community focused establishments or of anything else i mentioned.

So you wish to use these parts as demonstrators? That's okay as long as you POST THE DESIGNS.

I know the vicious cycle you're in and they'll NEVER be good enough. Just post already.

I didn't forget about posting the designs. They're coming soon but figured I owed an explanation for the holdup. The print I borrowed from you needed so little work done to it (just had to add the shaped bar that attaches it to the main part- everything else was good to go, the most common bits fit just right into the center hex, 3/16" ball bearings work great, etc.) that it was quickly in it's final form since any ease-of-use feature I could think to add- like mounting it to the attachment bar on an axis so you could spin it 180 degrees to change directions instead of removing the attachment and putting it in the other way- added obvious points of failure.

I've planned a testing system with three feedback stages- rough prototype, refined prototype (based on first feedback), and final version pre-release. I started the rough "beta test" two days after I last posted here, a week early, because I had some extra help become available. The feedback that we got was way more comprehensive and helpful than expected. I was looking for a basic list of things that people liked or didn't, with priority on factors which might make someone who benefits choose not to use it or a factor they'd have to mention to a friend if asked for a review. I got a lot more than I hoped, with a far higher rate of useful suggestions. The only impediments to people giving feedback were both predicted- some people just can't bring themselves to criticize or say anything remotely negative about somebody's work. Secondly, some people will just not believe that the item is free of charge, commitment, or other abstract type of debt and won't accept it regardless of assurances. The most important feedback hit me from out of nowhere, which concerned the fact that items like this- which work around some loss of ability- can have a profound positive impact on a person's (especially with the elderly) sense of self-reliance and personal independence which leads to overall improvement of their quality of life due to decreased reliance on caregivers and others to do things they used to do themselves. That was huge and will now be a primary consideration for future design projects.

I'm putting in the last few design changes, then I'll post everything. Yours gear design was the first attachment which directly addressed a movement type and had a purpose separate from simply not dropping or getting a better grip on different things. In testing, the base item that wraps around the hand moved more than it should and tended to twist into the back of the hand in uncomfortable ways, so I have to add a bit of structure to offset that issue. I'm putting in as many hours as I can on design, so not much longer. I've got a busy week with new types of professional clients to meet with plus a GoFundMe campaign to put together. We're hoping a small crowdfunding round will free us to fully develop a process whereby someone can identify a need that 3D printing can address in their community. We'll develop and test methods for every step geared toward providing the maximum benefit to the most amount of people as cost effectively as possible. After that, beyond distributing the program and establishing a forum where people can improve and refine our work, but we want to set up training and get some groups going out there.

Getting good feedback is always difficult, yes! That's another way restricting your design shoots yourself in the foot. With luck we'll see it soon, if not, please post anyway, so you can get better feedback.

Where do you post your designs? I love the sound of this but can't find them.

These haven't gone up. I generally like to work out most of the bugs and kinks before putting things up in public though I'm happy to email or send them to people in any stage of completetion.

If it's polished enough to print 50 sets a month, it's polished enough to post :p Just flag it as a work in progress and people will understand.

How much would I have to upscale it to use 6mm airsoft BBs? that's all I have and don't want to buy more.

6/4.5 = 1.333 meaning 133% or so. Plastic BB's aren't as good as metal ones though, in strength or quality, and scaling it will alter the size of the hex hole as well into a weird size neither metric nor SAE has ( 1/3 an inch? 8.5 mm? )

I made two..... they work great.

I made one it worked great. Thanks, Great design!

Glad you liked it. Which version was it, the 4 or 6 ball?

Both actually with 4.5mm BBs and 5.98mm plastic airsoft pellets. I went and played with the code a little changes parameters and tried out different things. My openscad skills are not real good. I can edit other people code but have yet to practice writing my own stuff. I then made versions of this ratchet in sketchup and placed it part assemblies. I really like the concept of this design because it is simple yet effective.

There was an error in spragg5.stl -- one of the parts was in midair -- which I've fixed in spragg5-fixed.stl. Sorry!