HobbyKing.com New Products Flash Sale
Reply
Thread Tools
This thread is privately moderated by Daemon, who may elect to delete unwanted replies.
Old Nov 17, 2011, 05:27 AM
Registered User
Daemon's Avatar
Lakewood, Colorado
Joined Aug 2002
29,079 Posts
Build Log
Evolution of a crashable Tricopter

My first Tricopter started life as the simple wooden framed Mongrel Gear Trilogy
using 4 cheap rate gyros, 3 cheap ESCs, 3 cheap motors and the RC Tx's CCPM mix.
The rear motor was mounted on a platform supported by a heli blade shaft and pivot
which is a popular option for Tricopters.
However, during the learning process (having never flown any rotor-craft before), I
found that any crash on the rear arm bent the heli blade pivot. In fact any
hard landing would do it as the weight of the motor simply bent the shaft down.
That meant the yaw trim changed constantly and eventually the shaft just
snapped off.

I rebuilt the rear tilting motor mount using steering parts from a crawler
so that it was a tilting platform with the pivot point directly over the center
of the rear arm. That mount is totally cobbled together with zip ties
but it has been absolutely bulletproof. I tweaked the servo position but otherwise
transfered that mount over from old frame to my new one, unmodified.


It wasn't long before I was buzzing around low between and below trees, over water,
etc. Accumulation of crashes including an inverted water landing went through
the first batch of motors pretty quickly. When I got into the 2nd batch
of motors (and some ESCs) ordered from HK I found some un-subtle differences
in power. I was having to use a-lot of trim to get it flying level. Problem is,
that wasted precious flight time, and if I tried to leave it trimmed when changing
batteries, one or more of the gyro's wouldn't arm because the center position
was too far away from true center, the ESCs wouldn't arm because their throttle low
position was no longer low. I'd have to center all the trims, plug in the battery, try to
remember the exact number of clicks of pitch and roll trim.. take off, trim some more.. get
it steady, fly for a while, land and repeat. I finally got fed up with that, and ordered
a v5.5 Black KK multicontroller board. That eliminates all four rate gyros and
it initializes the throttle signal independently of pitch/roll trim so I can maintain
trim changes between battery packs (trim still changes with differences
in motors, ESCs, battery size, cameras on-board etc).

KK controller is pretty much plug and play. Only quirk in latest Tricopter firmware
is that it won't let me reverse the gain on the yaw gyro, and it happened to
be backwards for my current servo and mounting position. Eventually switched
to a digital servo that I could reverse programatically. Digital servo jittered a lot
so eventually moved to HS85MG which happened to turn the correct direction.

Moving on, the Trilogy has a single plywood layer in the central platform, and 3
square arms with bolts through the arms connecting them to the platform.
I found that most hard crashes would result in either the platform breaking down
the middle, or one or more of the arms splitting out around the bolt holes.
Went through a lot of PU, gluing those arms back together.

About now you're going "Why don't you just stop crashing?"
Well, besides the fact that I like to fly fast, close to and under things so was crashing
into and falling out of trees regularly I was also having random motor mount failures.
The Trilogy was originally designed (may still be) to mount the motors to the
arms using zip ties to hold two of the 4 arms of a standard motor mount cross
down to the top face of the square arms. Zip ties could take the flight load, and a little
CA kept em from sliding off. Idea was, that in a hard enough crash
the zip ties would break, saving the motor itself. Ultimately though, I had several
failures of those 4 armed crosses themselves. They were vibrating and twisting causing
metal fatique of the cheap aluminum until the cross failed, the motor departed the
arm, and the tricopter falls from the sky like a brick. Once or twice might have
written off as a fluke but it happened about a half dozen times. I needed to be able
to mount the motors using all four arms of the motor mount cross, but still retain
some way to absorb crashes and hard landings.

My old Trilogy frame finally just gave up so I retired it. Looking around for
an alternative, stumbled on a very popular link.
http://www.rcgroups.com/forums/showthread.php?t=1494207
Dual layer central platform simply clamped to dowels for the arms
with motor mount platforms also clamped to the arms.
A minor crash results in the arms or mounts shifting or rotating.
A major crash also breaks nylon bolts. Every component is field replaceable,
and it's fairly easy to break down for travel.

Here's my version.

Close-up of how each motor is mounted

It's a pretty easy build. The platform and all the plates were cut from aircraft ply with
a handsaw, and the holes made with a drill press, but could have been done
with a regular hand drill.

Close-up of the gear on the central platform.

It ain't pretty but it gets the job done. The GoPro is strapped down to
an anti-vibration platform (gel mounts inside). Flight camera is
in a block of foam.
5V BEC to power Rx and KK board.
KK board has real simple wiring.
2.4Ghz FrSky telemetry Rx works fine for my usual relatively close buzzing around.
Video Tx mounted on another pair of clamped together plates,
a bit lighter than the motor mounts, so it rotates more easily, which helps
prevent damage to the low pass filter and CP antenna stuck on top.

It's already proven that it can take a beating. I broke some nylon bolts and plates
but had spares in the field. I've reinforced the bottom plates
with a layer of Kevlar cloth since then, and they're holding up better. A hard, fast
forward landing from a dead battery resulted in every arm moving and every motor
mount twisting, with no damage at all.

If you look at the tail mount photo above, can see that the servo is simply clamped
between the two plates with a little stick on sandpaper to add friction. Hopefully
any hard impact will basically just disassemble the whole mount rather than
break the servo arm or something else.

Here it is in action
FPV - Tricopter - Trees, sun and shadows (6 min 4 sec)


Since that flight, I've done some more work on motor/prop balancing and
freeing up the anti-vibe mount to do its job better.
It's a bit heavy but there is some room for weight savings by trimming down
some of the plates. I might try thinner, but dual reinforced kevlar plates
for all the motor mounts. The video Tx plates can be much smaller.
May also poke some large round holes in the bottom plate in unstressed
areas.

[edit]
Here's another showing how it handles crashing.
FPV - Tricopter - Low flying.. crash crash crash (3 min 45 sec)

Platform was unharmed. Broke one nylon bolt a few props.

Recently switched KK board firmware to KapteinKUK v1.6 and that got rid of some of
the glitching I was seeing on the motors and tail servo. That plus the FY30A stabilizer
in series, has made it quite a lot more stable in high speed flight.
Here's an example of what it can do now.
FPV - More tricopter night ops (4 min 31 sec)



I take no credit for the design, as I borrowed directly from others.
I went with this approach because I like flying a lot more than building/repairing.
Daemon is offline Find More Posts by Daemon
RCG Plus Member
Last edited by Daemon; Jan 22, 2012 at 10:06 PM.
Reply With Quote
Sign up now
to remove ads between posts
Old Nov 19, 2011, 12:39 PM
my karma ranover my dogma
galaxiex's Avatar
Edmonton,Canada Eh
Joined Jun 2007
7,573 Posts
Thanks for posting this build log.

Some great ideas there, that I'm sure will help a lot of folks building a Tri.
galaxiex is offline Find More Posts by galaxiex
Reply With Quote
Old Jan 13, 2012, 09:04 AM
Registered User
Deutschland, HE, Frankfurt am Main
Joined Mar 2011
139 Posts
Hi,

Nice Trikopter !

I just saw your motors and noticed that I have the same one on my new wing.
My question is: what propellers did you use und what A-draw do you get with them per motor ?


regards blacknose
blacknose2010 is offline Find More Posts by blacknose2010
Reply With Quote
Old Apr 16, 2012, 11:58 AM
Advanced Monkey
nebstress's Avatar
United Kingdom, England
Joined Nov 2011
1,605 Posts
KK Board with FY30A

Hi Daemon,
I've been trying to connect an FY30A to my KK controlled Tricopter, I am not sure that I have got it right & would really appreciate some help or advice.
I have it connected between the KK board & the Receiver, is this right?
I was thinking that it might be better to put it between the KK board & the ESC's & Servo??
Please any help would be much appreciated.
nebstress is offline Find More Posts by nebstress
Reply With Quote
Old May 16, 2012, 04:57 PM
Plane Destroyer / Life Enjoyer
airbagit13's Avatar
Miami, FL
Joined May 2009
3,508 Posts
Nice Daemon, I love me some night time Tricopter flights.
airbagit13 is offline Find More Posts by airbagit13
Reply With Quote
Old May 17, 2012, 04:02 PM
Registered User
United States, MO, Kearney
Joined May 2012
82 Posts
please send me an email

I am looking at building a very similar platform as this and was wondering if you would help me to huddle the parts to build and fly it...

it will actually be used for shooting some footage for various videos i'm producing..

Thanks!

Jeff
nyztyz is offline Find More Posts by nyztyz
Reply With Quote
Reply

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion The Ultimate Crashable AP platform sky guy Aerial Photography 0 Apr 05, 2008 09:01 AM
Discussion "crashable" landing gear - anyone know how? rotagen5 Foamies (Scratchbuilt) 22 Feb 22, 2008 12:45 AM
Discussion any non crashable planes? flyboy367 Electric Plane Talk 25 Dec 12, 2006 07:17 PM
What's the latest thinking in crashable planes? Jim_Marconnet Beginner Training Area (Aircraft-Electric) 37 Mar 15, 2006 02:10 AM
crashable (very inexpensive) 5.25 MP digital camera tmophoto Aerial Photography 3 Sep 16, 2004 11:25 AM