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Flitetest DIY Gremlins

jhitesma

Some guy in the desert
Mentor
#41
3D printing is making these micros so accessible. Theshortcrayon on thingiverse has 2 designs, the swirlie and the doubler, of which I plan on building one soon.
I've looked at those...but it seems the swirlie is based on a 1.5mm CF plate which he hasn't shared the design of, and the doinker crashed my macbook when I tried slicing it to see how long it would take to print :p

There are a number of other designs up on thingiverse for 80-90mm frames as well.

I've been teaching myself onshape and fusion360 so decided to sketch up a quick and dirty 80mm frame last night. Just a simple X 2mm tall with 8mm wide arms and 15mm motor pads (the 1103 motors are 13.6mm so 15mm gives a little tiny bit of almost protection.) The design is pretty crummy - I did a number of things foolishly in the sketch. But I printed it out over lunch just to get a feel for the size of these things in practice.

20170315_140718.jpg

We need a jawdrop smilie on this forum...I mean. I've seen photos of these things and have a fairly good feel for measurements (way back in high school I was on our science olympiad team and earned medals two years in a row for metric estimation at the state level) but it still blew my mind just how small this actually is. I had to get out my calipers and measure it to make sure it's really the size I designed it at.

It's not stiff enough that I'd actually try to fly it. I plan to draw the arms as U's or add some ribs to stiffen it up. But just for kicks I taped a dime to each arm, and two nickels in the middle to simulate the weight of flight gear (dimes are a bit lighter than the actual motors but the 2 nickels were a bit heavier than the ESC's and FC so it kind of evens out.) Then I tossed it at the concrete as hard as I could. Tape gave out and the coins went flying after a few tosses - but no damage to the frame.

So it seems 3d printed frame is actually pretty viable for something this small. I didn't account for the weight of the battery or camera...but this is also PLA and I plan on printing it in PETG or Nylon (or annealed Raptor PLA.) so it's a VERY unscientific test that should be taken with a HUGE grain of salt.

My motors and esc's should be here Friday - so need to get going on a real frame! But my props still haven't hit the US (shipped the same day - go figure) so not a huge rush yet. Starting to get excited though. And holding something physical in my hand really made me realize the sizes at play....

Oh...and neat thing about onshape...it's free cad that runs in your browser made by guys who split off from solidworks. It's crazy powerful and the big limit is anything you do in it is public. So here's the link if anyone wants to mess with it: https://cad.onshape.com/documents/b...3ce0781506987c1cbc/e/38a1a6301333e177140ed869 Be warned though - as I said this is a really bad design with some ugly mistakes in the sketches. I need to draw something better up tonight now that I've figured out a few more things about onshape.
 
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jhitesma

Some guy in the desert
Mentor
#42
Hmm, printable frame is looking more and more viable. Motors FC and ESC's should be here tomorrow - but props are still in shipping limbo. But did a few more onshape tutorials and took another stab at designing a printable minimal frame: https://cad.onshape.com/documents/2...b9c39531d712993399/e/0e5240a5739888c0591d7b06

First glance looks very similar - but the design process was much quicker and much cleaner. Only took me about 15-20 minutes to draw this up and the sketches are much cleaner and more parametric so it's easier to adjust:
Screen Shot 2017-03-16 at 10.35.06 AM.png

But flip it over and the big difference is obvious:
Screen Shot 2017-03-16 at 10.15.39 AM.png

It's hard to tell looking at it on the screen...but I thickened it from 1.5mm to 2mm and added 2mm ribs on the outside to make it stiffer. Those FC mounting holes are 3mm on a 20x20 footprint to match the pico blx...the emax femto is 20x20 (pico is 27x27) itself to give you an idea where/how it would fit. Those tiny 3mm holes look HUGE on this thing. I wanted to add some little snap towers that the FC could just snap onto - but no good way to print those and the ribs. I may try to design some small TPU pins or something instead...still debating that.

Over lunch I did a quick print again, 30 minutes this time - the extra material added 10 more minutes of printing:
20170316_134753.jpg

5g is a bit heavier than I had been hoping for, but is inline with onshape's calculations of 5.843g for PLA - Not too bad. I did wind up with 2 layers of infill this time (at 15%) so maybe that accounts for the nearly 1g difference. Or it could be my scale isn't that accurate or just density difference between my PLA and onshape's preset figures.


I was going for 90mm mtm this time but for some reason left my arms at 50mm so wound up with a 100mm frame by mistake. Oops, that's what I get for rushing. Should be even stiffer at 90mm though so that's nice. Here it is next to the super quick and dirty 80mm from yesterday.
20170316_134826.jpg

And next to my E010 for another size comparison:
20170316_134901.jpg

I'm starting to think this may actually be viable too. The 2mm tall ribs look tiny but add a lot of stiffness. I was worried I may have to add some more ribs inside the arms to stop them from twisting - but they actually resist twisting quite well already. They still flex up and down some - but not too much worse than 2mm thick ply would. I may add a bit more webbing in there to see if it helps, but it's pretty darn close to something I'd be willing to try flying. At 80mm it's probably plenty stiff.

I still want to add some kind of prop protection and am debating just how I'll do that. But if I had my parts I'd start assembling this little guy :)
 

PsyBorg

Wake up! Time to fly!
#43
I know you designed it to be pretty side up but it looks to me like it already has built in motor protection if you turn it over as well as a nice safe channel to strap external esc's into should people not use an AIO fc.

That would also allow for some serious race footage where you get a flying start, gather speed and chop the throttle so you slide across a hardwood or tile / linoleum floor to recover and take back off after passing under obstacles. Could make for some fun indoor FPV races. Specially if you design it to use counter sunk motor screws.
 

jhitesma

Some guy in the desert
Mentor
#44
Yeah, I haven't decided which side is "up" yet :) If the motors fit inside the rim (they should...but I have a hard time believing they're really THAT small!) then I'll probably increase the thickness/height of it for more protection and do that. I'm not sure ESC's would fit in there though...arms are only 8mm wide and 5mm inside the ribs. So...we'll see. Once I get my parts tomorrow I may make some changes to accommodate them ;)
 
#45
Yeah, I haven't decided which side is "up" yet :) If the motors fit inside the rim (they should...but I have a hard time believing they're really THAT small!) then I'll probably increase the thickness/height of it for more protection and do that. I'm not sure ESC's would fit in there though...arms are only 8mm wide and 5mm inside the ribs. So...we'll see. Once I get my parts tomorrow I may make some changes to accommodate them ;)
Looking nice!!! You thinking about making a prop guard for the frame? I feel in order to fly these indoors, you need one to prevent damage to walls and such when you run into them!!
 

SP0NZ

FT CAD Gremlin
Staff member
Moderator
Mentor
#46
Hmm, printable frame is looking more and more viable. . .
Nice work so far. Great job with the modeling. It's cool to see more and more people here getting into 3D modeling.

I'm waiting for the official #FTGremlin power pack kit to start designing a 3D printed frame for it. I'm sure I could start now, I'm just using that as an excuse. ;)
 

jhitesma

Some guy in the desert
Mentor
#47
Looking nice!!! You thinking about making a prop guard for the frame? I feel in order to fly these indoors, you need one to prevent damage to walls and such when you run into them!!
Yeah, I'm more interested in flying outside since my house is so small I can barely fly a proto-x inside....but do have a few ideas on prop guard ideas I plan to try and model soon. I'm also planning on trying to print this in PETG and/or nylon instead for extra strength...but am worried about the loss of rigidity since PLA is so much stiffer. So...we'll see. Motors are still showing expected delivery of today...but last update put them in LA so not holding my breath.

@sponz - thanks. Last time I used any "real" CAD was autocad R13 or something like that (the one that came with the sample 3D space shuttle drawing) ...on an original IBM PC with a green only monitor. I've played with sketchup for some small projects but really didn't care for it's interface. Most of what I've done lately has been with openscad since it runs on my outdated computers and lets me make customizable things for thingiverse. I finally have a new notebook and can run Fusion360 - but am having a lot of fun with Onshape since it runs on almost all of my computers and my wifes chromebook :D

My big problem is still a gap in my visualization between on-screen and reality. Things look great on screen - but then when made in reality aren't quite what I was expecting so I have to go back and iterate a lot. Those 2mm ribs look huge on screen - but in reality they seem like almost nothing for example. But practice and experience is starting to help with that.
 

LitterBug

Troll Spammer
#48
I really should continue to resist this thread cuz there is way too much in my hanger already, but I have a bunch of 1306 motors laying around, a 3D printer, and a box of junk parts that I could make something up. Been wanting a Moller M200 since I first saw the ads in the back of Popular Science back in the '70s.
moller-sky-car-m200x.jpg

Kind of a Jetson's retro look to it. Should not be too hard to pull off as a quad or a hex... I've thought about building one out of foam/styrofoam to go over an existing quad for almost a year too.

Cheers!
LitterBug
 

PsyBorg

Wake up! Time to fly!
#49
Haha I remember that as well LB. My grandfather and Uncle used to get popular mechanics subscriptions each year when our school had us kids sell magazine subs to get money to fund local sports and recreation programs in our town. I never connected this to the Jetsons but now that you said it It really does look like it could have been the predecessor to the folding briefcase versions George had.
 
#50
Hi Jhitesma!

Please post some pics once you have this little beauty assembled and ready to fly.

In a future evolution of your 3d model, you could add an enclosed area in the center to hold the emax femto FC/PDB.

Nice work!
Greg
 

jhitesma

Some guy in the desert
Mentor
#51
Hi Jhitesma!

Please post some pics once you have this little beauty assembled and ready to fly.
Was really hoping I could do so today...but USPS still says my motors/FC are expected to be delivered last Friday :p My batteries I ordered Friday from a US seller are scheduled for delivery today. So at least I won't have to wait on those.

I did tweak the frame a bit more, I bumped the ribs from 2mm tall to 3mm which gave the frame quite a bit more stiffness without affecting the weight enough for my scale to detect (it's not a great scale.) I did both 80mm and 90mm versions and both seem stiff enough to fly.

Once I've actually flown it I'll share stl files on thingiverse...but anyone who wants is welcome to open/copy the Onshape document and generate their own stl's if they can't wait. (you right click on the part in the "part list" at the lower left of the screen and select "export" to generate STL's.) I labeled all the features so it should be easy to modify and do things like hide the mounting holes.

In a future evolution of your 3d model, you could add an enclosed area in the center to hold the emax femto FC/PDB.
Yeah, I was thinking about a version designed for the emax stuff - the motor mounting is slightly different and the femto is a bit smaller and doesn't have mounting holes. I have a friend who already has an emax setup (but got one bad motor and one bad esc so can't fly it yet) and need to get together with him to check some measurements/fit.

If anyone has the hole spacing/size for the emax 1104 motors handy I could update a version of the frame for them really quickly.

Honestly instead of an enclosed area I'd probably just use some strong double sided tape to mount the femto over the middle, should weigh less and as light as these things are I'm not overly concerned about damage.

I also still want to add something to mount my FPV gear but will probably just use my existing e010 mount and a rubber band for the first few tests :D
 

JimCR120

Got Lobstah?
Site Moderator
#52
Emax Status Change

Just in case you haven't noticed there was a change on the Emax micro power pack.;)

Now it is called Power Pack G Gremlin Power Pack.;)

The price also went up a bit to $75.95. :(

It is still out of stock. :mad:
 

PsyBorg

Wake up! Time to fly!
#53
Ohh hopefully the restock times well with the beginning of the month before I spend my spare cash for the month on another flight battery .
 

Mid7night

Jetman
Mentor
#56
There appears to be no prop hub with the pack. The motor bells are tapped. Looks like props are screwed directly to the motor bell.
I mean on the tri-blade props themselves; how thick is THEIR hub? It appears to be the same diameter as the motor (roughly), but how "tall" is it?

I'm modeling all the bits for CAD mockup purposes, and I plan to upload them when done, but that's one dimension I can't find.

Also, if anyone has them; what are the max thicknesses of the ESC and FC board?
 

earthsciteach

Moderator
Moderator
#57
I mean on the tri-blade props themselves; how thick is THEIR hub? It appears to be the same diameter as the motor (roughly), but how "tall" is it?

I'm modeling all the bits for CAD mockup purposes, and I plan to upload them when done, but that's one dimension I can't find.

Also, if anyone has them; what are the max thicknesses of the ESC and FC board?
Ah, I see! Sponz just received the Emax micro-pack. I'll bug him to measure that when he gets off of work.
 

Mid7night

Jetman
Mentor
#58
Ah, I see! Sponz just received the Emax micro-pack. I'll bug him to measure that when he gets off of work.
Great, thanks! Here's pics of the parts as-is. I just need to finalize dimensions before I upload. :cool:

Prop:
FT-Gremlin_prop_T2345BN_tri.jpg

ESC:
FT-Gremlin_ESC_EMAX-Bullet_6A.jpg

Motor & wires:
FT-Gremlin_motor_RS1104-5250.jpg

FC:
FT-Gremlin_flight_controller_F3-Femto.jpg


The flight controller and ESC were SUPER difficult to model correctly, but I think I did ok.... :p