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LitterBug's DIY 3D printed Gremlin - OctoUFO

LitterBug

Troll Spammer
#1
This has been a L - O - N - G time coming. Like several Decades worth. I thought it was the Moller M200 that was in the back of my head all these years, but after finally finding an advertisement from the back of December 1985 Popular Science it is all becoming more clear.
StarcraftAd.jpg
Imagine being able to fly over all those cars stuck during rush hour in something like that.... ;)

Well at any rate here is the design and build thread of my RC version of just such a vehicle.
InitialTestPrints.jpg

In the next couple posts, I'll take you through the design and build process I've gone through on this build.

Cheers!
LitterBug
 

LitterBug

Troll Spammer
#2
Designing from scratch and test fitting

I've been playing with a handful of tools for designing 3D printed "things", and so far, my favorite tool has been OpenSCAD. It uses a pretty simple programming language which is good for knocking out quick designs. I've parameterized key dimensions making adjustments to prop size, dome size, and the like results in an instant update of the layout.

I started with the motor mounts and ducts and worked outwards from there. Once I had those dimensions, I could tell it was going to fit on my print bed with a little bit of work.
OpenScadDuct.jpg

Went through several different designs. First thought was to print individual ducts to slip fit into a top and bottom half. Could then assemble it all with hot-glue, silicon atv, FoamTac, etc...
OpenScadBottom.jpg

After going through several test prints, adjusting for prop clearance, and slip fit, it became clear that this was creating more complexity than it was worth. With the limited 8x8 inch bed and 2inch props, it was getting difficult to have enough space to have good slip fit without causing shape issues and leak errors when slicing the prints.
InitialDuctTesting.jpg
InitialMotorSpacing.jpg
InitialDomeTesting.jpg
InitialMultiPartDesign.jpg
SlipFitTesting.jpg

I have a really nice collection of ABS test prints to use for playing with Acetone finishing at a later date.

For this first attempt, I've settled on a two piece design and ended up switching to 1.9" props.

Bottom with integrated ducts and motor mounts
BottomABSonPEI.jpg

Top
TopABSonPEI.jpg

The ducts from the bottom extend up 2mm into a tapered ducts in the top. Half of a two piece Christmas ornament slips into the Pilot Canopy hole in the middle.
Canopies.jpg
 
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LitterBug

Troll Spammer
#3
The electronics

This is the simple part of the build. Although since I was unable to find a 20x20 Flight Controller that supports 8 motors, and I'm using 20x20 4in1 ESCs, I will need to design a 20x20 to 30.5x30.5 adapter to mount the FC on top of the ESC stack. I initially thought about using individual ESCs for each motor. There are a few different ESCs available.
ESCs.jpg

When it came time to assembly, decided that might be a bit too complex, require a power distribution board, and I might just want to have 10A escs in case the heavy build needs more power for more thrust. Eight one way, two times four the other. I finally settled on a Seriously Pro Racing F3 EVO FC and two 10A 4in1 RTFQ ESCs. Here's a pic of the initial wiring up of the FC, ESCs, and RX.
LecTronNicks.jpg
I'll be using the Motor Mapping for *flight +Octo, but running dRonin for the firmware.
MotorLayout.jpg
It's much easier to remap motors in dRonin, and this allows me to try it out on *flight at a later date without much effort.
 
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LitterBug

Troll Spammer
#4
Final Assembly

FINALLY Getting really close to maiden. Still have a small amount of work to do on mounting the stack. Due to space constraints, somewhat heavy build, and dropping to a smaller prop diameter, I decided on a set of 10,000kv motors which have a higher potential thrust value but also higher current needs. Thus the final decision to go with 10A 4in1 ESCs. Here's the current iteration of the bottom half with the motors mounted up and props attached. Just enough clearance for the props, and good fit with the top half.
SmallerPropUniDesign.jpg

Have the Electronics all wired up and ready to go, then realized that I still need a 5V BEC for the FC. DOH. the Batt input on the FC was only for monitoring. <oops!>
MotorTestReady.jpg

Weight = 92g with just the top and bottom half of the frame. This thing will be a porker! But I have 8 motors to deal with that..... I'll initially test 2S, but can bump up to 3S if needed. Pretty sure I'll be smelling burning lacquer if I need to bump to 3S for more thrust. The motors can do it and sound cool doing it, but they get really hot fast.

So at this point, I've been able to flash the ESCs to the latest BLHeli 16.7, check and adjust motor rotations, and do initial configuration of the dRonin software.

Things left to finish:
  • Wiring BEC
  • Mounting the ESCs/FC/RX/BEC
  • Coming up with battery mount options
  • Maiden
  • Sign on a variety of test pilots.
 
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PsyBorg

Wake up! Time to fly!
#5
This is pretty cool. I would add one thing to your to do list though. You MUST print out a George Jetson pilot figure at some point maybe cool to hide all the electronics with hehe.

What size / type batteries you planning on? The way the room looks inside I would probably guess you would be going with two batteries paralleled?
 

LitterBug

Troll Spammer
#7
Funny you should mention parallel batteries, and once again, can't get anything past the 'borg. I must not have uploaded the correct picture, cuz there is a connector on each 4in1 with interconnection between them. Prolly run either two 300 or two 450 in parallel. Also depends on 2S or 3S. Have it wired "just in case" so it can be single or dual.
ParallelPower.jpg

Cheers!
LitterBug
 
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French

Construire Voler S'écraser Répéter
#8
Awesome build!!!! Can&#8217;t wait to watch it hover (you need lights beaming down ;) )

Did you think about XT30s vs the JSTs?
 

PsyBorg

Wake up! Time to fly!
#9
Ohhh Marvin is another great choice providing you print a uranium 238 space modulator to mount on the air frame too!.
 

LitterBug

Troll Spammer
#10
Awesome build!!!! Can’t wait to watch it hover (you need lights beaming down ;) )

Did you think about XT30s vs the JSTs?
Yeah, I have thought about getting rid of all my JST and converting to XT30. But I have a bunch of batteries, planes, and small quads that would need to be converted as well. I did finally find an xt30 paraboard for charging and have a couple larger XT30 batteries. My concern is more battery sag rather than overcurrent on the JST connectors. My other 11xx quad builds can sag and heat up batteries, so imagine what double the motors on a heavy build could do. One other thing that would be cool is to get the BLHeli startup tune to play the Close Encounters 5 note tune.... Have plenty of lighting ideas depending on how well it flies.

Cheers!
LitterBug
 

PsyBorg

Wake up! Time to fly!
#11
With the new firmware there are several selections. My Gremlin now plays the Imperial March on boot up. That is beeper strength set to 91. There are 5 or so other choices as well. Not sure if the one you want is on the list though.

Edit: Ohh I just remembered there IS a video some guy made on how to make and program your own start up tunes on you tube so all is not quite lost.
 

LitterBug

Troll Spammer
#13
There are also some new features in DShot that allow alerts and such to go out through the motors. May check with the dRonin Devs to see if it's feasible to use that as an option too. Thanks for the ideas and links guys!

Cheers!
LitterBug
 

LitterBug

Troll Spammer
#14
Maiden/autotune Ready!

Managed to get the ESCs and FC mounted tonight as well as wiring up a BEC to run the FC. RX is bound, ESCs are calibrated, dRonin Neat firmware is configured, and there is an indoor fly tomorrow night. Just need to figure out where and how to mount the batteries.... May just velcro them to the bottom and use them as landing gear. :) Here's some bad focus pics:
MaidenReady.jpg
MaidenReady2.jpg
MaidenReady3.jpg

Really cramped for space with the dual 4in1 stack with the FC on top and the limited 8" diameter size... We'll see how the maiden goes before deciding on designing a larger version and tracking down a larger printer.

Cheers!
LitterBug
 

French

Construire Voler S'écraser Répéter
#16
Awesome!!!

If you have a taranis, you should load up some hover and pew pew sounds on your radio and have them set to switches ;)

 

PsyBorg

Wake up! Time to fly!
#17
Looks to me like you could easily stand up two 450 mah 2s or 3s batteries next to the FC. A little velcro to hold em in place so they don't beat the FC into a frenzy should work well enough for scale type flying. I don't think you designed this so much for free styling and getting bounced off objects. Or did you? :p

That profile shot looks awesome. CLASSIC old school space invaders stuff. Love it! :applause: I still think it needs the Uranium PU 36 Space modulator. Later it was upgraded to be much bigger and dubbed the Illonium Q-36 Space modulator.

Where is the Kaboom? There NEEDS to be an Earth shattering KABOOM!!

 
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LitterBug

Troll Spammer
#19
I'm dying to see this fly....but at the same time...I'll gladly wait for Marvin to get in it first ;)
Already thinking of ways to scale this up. Making a foam shell for my F550 hex with 9" props would be absolutely AWESOME for FFE next year. May try a Hex 5" with foamboard and 3D printed ducts as a progression. Some simple math shows:

If 2 inch props barely fit 8" diameter circle for an octocopter, the following diameter would be needed for:
3" Props = 12"
4" props = 16"
5" props = 20"
5" props with a 22.5" diameter would get me the size I want for a Moller M200 layout.
Did a quick sanity check drawing in OpenSCAD for validation, and the math works out right.

With a hex, the diameter could be less. Will have to work out the dimensions leaving room for a decent cockpit dome.

Also trying to think up a 3D printed design for 5" that would be split into sections and fitted together. Carved foam with 3D printed motor mount thrust tubes seems like the easy way to go.

Cheers!
LitterBug
 
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LitterBug

Troll Spammer
#20
Initial Maiden......

Huh... when you make the motors spin in the direction opposite of the picture in the configurator, you get constant yaw spin... D'OH! Unfortunately no film developed yet. I can't tell you how many times I checked the mapping and rotation thinking I had it all set right. Could have fixed it by clicking on one box at the gym, but didn't think to recheck the prop rotation till I got home. Good news is, I should have plenty of thrust even on 2S so it's time to start adding LEDs....

All powered up before maiden
PoweredUp.jpg


Cheers!
LitterBug

PS: AUW with 2x450mah 2S batteries.... 231g
 
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