Quick 3D printed flying project

[jhitesma]

Decided to make something fun for my daughter this weekend. Have had my eye on a few similar designs but finally decided to print this one for her: https://www.thingiverse.com/thing:51489

Just printed the 5 blade prop first - came out quite nice and flys impressively well!



At least for me. With a good solid tug I can get what I'd estimate as 80'-100' of altitude in calm air. But my daughter with her little 7 year old arms can't quite get that good of a tug on it. She gets maybe 10'-15' of altitude on her best tries. One of her friends was able to get about 20'-30' but still not as good as I could.

I tried printing a few of the other prop designs, 3 bade, 6 blade, and the remixed 5 blade lightweight version. She got really excited trying to predict which would do better - would more blades do better? Or Would ones with fewer blades to better because they were lighter? She guessed all by herself that the ones with more blades would be "stronger" and should be able to go higher...but they weighed more. She was really into trying to figure out which would be better and I loved watching/listening to her reason out her hypothesis!

I could have left it there. It's a great fun toy and we're having a blast with it. But I'm me. I can't leave well enough alone. And I want her to have the fun of launching a really high flight all by herself.

I also couldn't help but notice that the top of the handle looks to be about the perfect size to fit a 2204 or 2205 motor...and I have quite a few of those laying around from my multirotors....the original designer was also kind enough to share his Solidworks files which Onshape can open....hmmmm.

Only took a few minutes to open the file for the "hub" in Onshape and make a few quick adjustments:


First I removed most of the hub since I didn't need the shaft and spool.

Then I made a new sketch on the bottom face and drew a 5mm circle in the center which I did a remove extrusion "through all" to fit a 5mm motor shaft. (It's actually 5.4mm to fit easily but 5mm is easier to say.)

I'm using a spare CCW emax 2204 2300kv motor so it should self-tighten...but figured I'd use a nyloc for safety...except...the only nylocs I saw on my desk had a large flange on them and would require removing too much material from the hub. So instead I just used the stock prop nut.

I made another sketch on the top surface and added a 6 sided inscribed polygon on a 10.3mm circle to fit the stock prop nut.

It actually took me four revisions to get the sizes "just right", thankfully this is a quick 25 minute print

Finally I had a hub that fits my motor and holds the nut. Since it's a CCW rotation it self tightens and all is good with the world:



To test it I grabbed a spare KISS esc....then realized it would be a lot easier to use an ESC with a built in BEC for this so swapped to a spare emax 12a "simon series" I had laying around. Mounted the motor on a spare arm for my hexacopter (which I don't plan on using because this hybrid plywood/CF arm proved to be too weak.) wrapped the ESC in some kapton to keep it from shorting out on the arm then added some heat shrink to keep it all in place.

Hooked up a servo tester and took it outside with a 450mah 2s pack from my 90mm quad. Spun it up to full throttle...and got to enjoy some nice failure. :black_eyed:

I had grabbed the 3 blade prop to test with first figuring it would be the lowest stress on the motor. But...the 3 blade prop was damaged. One of the blades had broken at the hub. Still flew fine human powered but the power of the 2204 on 2s was more than it could take and it blew apart before it could launch. Also, I had forgotten to tighten the mounting screws on the 2204 so it almost fell off and was shaking like crazy.

Oh well, 1st tries seldom succeed!

Snugged up the motor, grabbed the 6 blade prop...inspected it for damage...and went out for another try.

Worked great On 2s it didn't seem to get quite as high as my manual pulls...but these "simon series" ESC's have slow FET's and can't do active braking. So the launch is a little sub-optimal. And it's a lot windier today than it was yesterday so I had a lot of lateral drift that probably ate some energy.

Well....let's channel my inner Tim Taylor and give it "more power!" time to try 3s.



It's kind of scary how it sounds at full throttle...but it works quite well Think I'm getting a bit more altitude than my hand launches now...but again the wind today makes that hard to judge.

Still it's proved the concept enough to take it another step:



Handle modified to mount a 220x motor! It's printing now, still has about 30 minutes to go.

Oh, BTW OnShape project is here if anyone wants to play with it:
https://cad.onshape.com/documents/1...8f83c0697b2e8aff1b/e/799261b008764e4709b70116

And STL for the motor hub is shared on Thingiverse here: https://www.thingiverse.com/thing:2404022

I was thinking about modifying the handle to hold some 18650 batteries...but hooked up my watt meter and found this thing is pulling 22amps with the 6 blade prop (and 21 with the 5 blade) on 3s...no wonder my little 12a esc is getting kind of warm 18650's won't deliver those amps...so I'll have to stick with a lipo pack which won't fit in the handle very cleanly. I have a few ideas though.

Also going to swap my 12a simon series esc for a 25amp afro since it can do better braking to release the prop faster. And going to replace the servo tester with an arduino setup so you just push a button and it then spins the motor at full throttle for a few seconds and then cuts it to 0. (Could get fancy and add a tach function so it stops when the props stops accelerating...but I'm too lazy to tackle that right now.)

Fun project well worth trying if you're got a 3D printer!

 

[Snarls]

Nice little project. It's always fun and rewarding to take some concept and improve/modify it using your CAD and 3D printing capabilities. What filaments are you currently using? Looks like some semi-translucent colors.

 

[PsyBorg]

Bad side Bill here.... addicted caller and long time devils advocate.....

Whats the limits on that printed material for the rpm's you are pulling. I would be worried about that whole "Lets spin a CD rom to 19000 rpm and watch it shatter" thing happening. Having never printed something and not knowing exactly how well the bonding between layers is this thought has crossed my mind. Specially since it is for kids to play with. We are used to knowing how damaged a prop can be before it becomes a safety hazard so I was just putting that side by side with a kid at play having the attention to detail to know what to look for.

On a brighter note Plus 1 for your daughter with the sciency thought process. Good parenting brings that on by keeping them active and being involved. I meant to compliment you on that before when you bring up the interactions with her that have impressed you.

 

[jhitesma]

Nice little project. It's always fun and rewarding to take some concept and improve/modify it using your CAD and 3D printing capabilities. What filaments are you currently using? Looks like some semi-translucent colors.

This is the MakerGeeks Crystal series Green and Red I got in their December GeekBox (Which incidentally I just found out I'm still being charged for even though I canceled it two months ago ) The handle and hub are in the last of the MakerGeeks "Mint Green" I got in one of their grab bag's last year and used for my 3D printed robot arm and needle cutter.

 

[jhitesma]

Bad side Bill here.... addicted caller and long time devils advocate.....

Whats the limits on that printed material for the rpm's you are pulling. I would be worried about that whole "Lets spin a CD rom to 19000 rpm and watch it shatter" thing happening. Having never printed something and not knowing exactly how well the bonding between layers is this thought has crossed my mind. Specially since it is for kids to play with. We are used to knowing how damaged a prop can be before it becomes a safety hazard so I was just putting that side by side with a kid at play having the attention to detail to know what to look for.

Very valid concerns. And why I tested it by myself with safety glasses when no one else was home

PLA is pretty tough - but also brittle. As I mentioned the high RPM's of the motorized launcher did cause the one damaged propellor to shatter. And I shattered another yesterday experimenting with launching horizontally and hitting my truck. (No damage to the truck, but the prop wound up in 5 pieces only 4 of which I found.)

I would advise children (and adults) to hold it above their head just in case...but given the design of the parts with the thick outer rim I feel fairly safe letting my 7 year old play with it. Which isn't an "Ages 7 and up endorsement" that's just my opinion as the parent of my child and my knowledge of her and her ability to deal with potentials dangers.

I'm probably going to print a few more in PETG. It's heavier so may not fly as well and could do more damage when it hits things....but it's also stronger and tends not to shatter like PLA when it does break. I may also do a few in ABS which is lighter than PLA but tougher and also doesn't shatter. I'd love to do a few in Nylon which is really light and super strong but also soft but not as soft as TPU...but I'm having issues printing Nylon right now. TPU may be fun to try....wouldn't worry about it coming apart and would be all but unbreakable. But...may not be stiff enough to actually work.

On a brighter note Plus 1 for your daughter with the sciency thought process. Good parenting brings that on by keeping them active and being involved. I meant to compliment you on that before when you bring up the interactions with her that have impressed you.

I was really impressed that she did that without my prompting Makes me really glad about the school we've got her in (which is STEM based) and the path she's getting set on!

 

[PsyBorg]

Yeah that is kind of special when they surprise you like that. AND being a girl even more so seeing an interest in the sciences or more particularly to us here interest in flight no matter how it is done.

I posted mainly to have the discussion in public knowing you understand your daughters grasp on things and do spend time with her in our hobbies as much as she will allow. That way should others decide to try this they know there are risks and you making the design get to put out in front what your thoughts and concerns were and did not just go hey try this its cool..

 

[jhitesma]

Made a bit more progress last night. Got the handle modified to hold the motor and ESC:



I was just a little bit off on the hole for the motor wires. Since I didn't actually measure that and just eyeballed it's location I'm pretty happy with it

This is MUCH easier to hold and use than the hex arm!

But...that old BS20 ESC uses just about all of the space. It's on an older version of blheli and does have damped light with fast enough fets to actually take advantage of it. I haven't got a chance to try flying it outside yet - but just revving the motor and stopping it I can see and hear that it's stopping much quicker.

One surprising thing about this motor setup - it's actually better/safer for inside flying than the hand pull one. It's surprisingly hard to do a slow pull on the manual one. It's almost always too slow and the prop doesn't come off...or it's too hard and it slams into the ceiling.

But with the motor I can consistently choose to only turn it up to a set point on the servo tester and reliably do indoor launches that don't hit the ceiling

Tonight I'm going to work on code for the arduino and I'm debating the different ways I can set it up. I definitely want to give it a "power" control". But am debating if I'd rather use a 3 position switch for (inside, small yard, big field) power settings - or a knob to give fully adjustable power. Then the other question is how should the trigger switch work. Easiest way is as long as you hold it down it revs to the set power then when you let go it cuts it to 0. Slightly smarter way would be when it detects a button press it revs for a set amount of time (to give the prop time to spin up to speed) and then cuts to zero. Smartest way would be to add a sensor to read the RPM's of the disc and rev until they stabilize then cut it to zero.

I don't think I'll do the sensor though...if I had an ESC that gave RPM feedback that would be easy. But I don't. So I'd have to use a hall effect or an IR led and both have issues I'd rather not deal with. IR led would seem easy...but since I use variable prop geometries it's not so straight forward. So first step I'll get it working where a button press means on and no button means off. Then I'll probably add a simple timer to automate it.

And...as I mentioned I'm running out of room:



Even fitting an arduino pro mini in there will be tricky. I could do something else though....I could use an old ESC with burned out FETS and just program it's AVR chip like an arduino. Or I have some loose AVR chips I could use - wire it up dead bug style or with a little homemade PCB. Any of those may save some space. But are more work. And there's still the matter of what to do with the battery.

I may do a bit of shopping and see if I can find a small high C 3s pack that will be easier to work with. Maybe make the handle longer and put it inside like the ESC. Or maybe make a cradle on the bottom it can be rubber banded into.

I may also try making a harness to run two of my little 2s packs in series and see how it does on 4s Though...those only have JST connectors on them and the JST on this is getting awfully warm at 22 amps Maybe I should order up some XT30's finally.....

 

[jhitesma]

Quick demo video of testing tonight. Yeah, I know I'm holding it way too close to my face - but it's kind of hard to use with the servo tester. Started putting together a sketch for arduino tonight to convert it to pushbutton - but don't feel like firing up the soldering iron to actually test the code right now.

It actually didn't get that high in this video since the wind was so strong. Had some better launches yesterday and this morning. When it's calm it comes down within a few feet of me instead of across the street.

Can't believe I haven't lost any of the propellers yet to the neighbors trees and roofs

 

[LitterBug]

OOoooooo..... Need to bulk print a bunch for flight fest.... We can litter up the landscape like a good LitterBug! I have wanted to build a clear demolition box to spin things up in till they frag.... need high speed camera to capture all the goodness.

A few things I'd like to start with: Fidget spinners

And my favorite, More blades are always better 5' prop


Cheers!
LitterBug

EDIT: I have a Hex frame that we can remote bulk launch these puppies with!

 

[LitterBug]

Bad side Bill here.... addicted caller and long time devils advocate.....

Whats the limits on that printed material for the rpm's you are pulling. I would be worried about that whole "Lets spin a CD rom to 19000 rpm and watch it shatter" thing happening. Having never printed something and not knowing exactly how well the bonding between layers is this thought has crossed my mind. Specially since it is for kids to play with. We are used to knowing how damaged a prop can be before it becomes a safety hazard so I was just putting that side by side with a kid at play having the attention to detail to know what to look for.

On a brighter note Plus 1 for your daughter with the sciency thought process. Good parenting brings that on by keeping them active and being involved. I meant to compliment you on that before when you bring up the interactions with her that have impressed you.

How many do you want Big Bad Bill? (or are you sweet William now?)

Cheers!
LitterBug

 

[jhitesma]

And my favorite, More blades are always better 5' prop
View attachment 89916

Nice Is that clear PLA? Almost looks like nylon....

EDIT: I have a Hex frame that we can remote bulk launch these puppies with!

Now you've got me thinking...I wonder if these would fit on my hex....Only problem is I'd only be able to launch three at a time without cutting open half the ESC's and unsoldering the jumpers (KISS - so no software rotation change option)

If you do do that you MUST get video!

 

[LitterBug]

Nice Is that clear PLA? Almost looks like nylon....



Now you've got me thinking...I wonder if these would fit on my hex....Only problem is I'd only be able to launch three at a time without cutting open half the ESC's and unsoldering the jumpers (KISS - so no software rotation change option)

If you do do that you MUST get video!

Yup. Clear PLA. One of the first things I ever printed. Should have plenty of stress risers ready to fail! Should be EPIC!

I'm thinking there ought to be a way to get dRonin to mass launch the toy copters.... Maybe a set of 915mhz telemetry radios, GCS motors tab, Z_I_N_N_N_G!!!!! Spare Seppuku on hand, spare Knokoff a550 hex frame, and a bunch of spare ESCs.... could also have @jhitesma recommend a custom mix for using a standard TX/RX pair and skip the whole GCS/motors tab. This WILL be going to Flite Fest in a couple weeks.....

Cheers!
LitterBug

 

[Snarls]

And my favorite, More blades are always better 5' prop
View attachment 89916

Is that the fan from one of the jet engines on Thingiverse? I've been wanting to print one of those models, but it would be a long project.

 

[LitterBug]

Is that the fan from one of the jet engines on Thingiverse? I've been wanting to print one of those models, but it would be a long project.

Yes in deed. I have a few of them downloaded in my queue. Think this is the one www.thingiverse.com/thing:1327093 and I shrank the main fan down to 5" for shiggles....

Cheers!
LitterBug

 

[jhitesma]

I'm thinking there ought to be a way to get dRonin to mass launch the toy copters.... Maybe a set of 915mhz telemetry radios, GCS motors tab, Z_I_N_N_N_G!!!!! Spare Seppuku on hand, spare Knokoff a550 hex frame, and a bunch of spare ESCs.... could also have @jhitesma recommend a custom mix for using a standard TX/RX pair and skip the whole GCS/motors tab. This WILL be going to Flite Fest in a couple weeks.....

Hmmm, I like promoting dRonin...but it would probably be overkill for this

Just a bunch of ESC's hooked to a RX is probably fine - then just need a mix in the TX that goes from 100% throttle to 0%. I'm kind of wondering if an ESC with reversing might work even better - go from 100% to -100% to help release the props faster...but I haven't experimented with that yet.

I would warn to use a big battery. I'm using the 5 and 6 blade props/fans and they're pulling around 22-23amps on a 2204 2300kv motor. I blew up my 3 blade before I could get an amp reading off it...maybe I'll try and reprint one tonight and get some numbers off it.

Since it's only pulling those amps for a second or two I'm not worried about the motors/ESC's...even my little 12a emax ESC held up to it...but...with 6 of them at once. 130+amps is going to need a beefy battery to not puff

Of course since the battery doesn't have to fly that's not big deal. Hook 2 or 3 2200's in parallel and you should be more than fine. Just use some heavy wire!

I already wish I could make FF this year...now I REALLY wish I could

I had hoped to make it an every other year kind of thing which would have meant this year. But...my parents are trying to sell their house and downsize. Incidentally, anyone looking for a really great house on a big lot - though with lots of trees - in northern Ohio let me know, just west of Cleveland in Bay Village. Yard is big enough to fly multis if you're more talented than me:

But I digress...with them trying to sell the house visiting this summer just isn't going to work out. Either we'd be there messing up the house while they're trying to show it off to potential buyers - or we'd be there while they're trying to deal with moving. Neither option makes for a nice vacation But once they sell and get a new place we'll be trying to get back into an every other year FF routine - my wife is even saying she misses it and wants to go back

 

[LitterBug]

Oh, now that is real close to FF. You should do both a visit to the Parents, AND FFE17! My wife is not a fan of north coast sand. Looks like a really nice place.

 

[jhitesma]

Oh, now that is real close to FF. You should do both a visit to the Parents, AND FFE17! My wife is not a fan of north coast sand. Looks like a really nice place.

That was what we did in 2015. Had family from Youngstown and Chicago as well as us visit for a big fourth of July party, then hit FF with my wife and daughter for 2 days one night. My sister and her husband and son stopped by on Saturday to check it out along with my parents and everyone had a good time. Had really hoped to do it this year...but the timing with their house going on the market just made it unrealistic

FFE18 though...is on our calendars, or will be once the dates are set

 

[jhitesma]

Still being lazy about actually testing my arduino code....

But last night remembered that I have an optical tach...and got curious.

Put a bit of reflective tape on the hand pull version, had my wife aim the tach and gave it a few good tugs. I was maxing out around 3,000 RPM or so with that.

Moved the tape to my motorized one....it's a 2300kv motor on 3s so I was expecting a top speed in the 28,000rpm range. I was able to confirm it's hitting 20,000 rpm - but at that point the tape got flung off and I was no longer able to get a reading

So the motorized version is a bit less than 10x faster than the manual version. Good to know. It does NOT result in 10x higher launches though - not sure if it's due to release issues or just physical limits...plus I haven't been able to test the motorized version in really still air yet. I still like the motorized version better since it's a lot easier to get consistent launches with

 

[LitterBug]

I'm thinking next on the list should be a continuous prop feed mechanism so you can rapid fire them.... ;-)

Ready for a bulk print tonight....


Cheers!
LitterBug

 

[jhitesma]

Sweet! May want to do one adapter first to make sure the nut opening is ok for you. I sized that for the cone nut that ships with emax 2204 motors. The red bottoms ship with nylocs that won't fit...and smaller "regular" nylocs will probably be too small to get locked in there and it may not be big enough to get a socket on them.