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Pumpkin drop event

Kraken Incident Report

Maingear

Flugzeug Liebhaber
#1
Built Kraken exactly as published with suppo gear and metal gear servos. 10 gauge harness from batt to ESCs.

Both esc would not run on a 2c 5000mah batt (within spec of electrical system) in lipo mode(1). Consulted suppo factory and recomended manually checking cells to ensure min voltage not crossed. So I ran in mode 2

Flight tested tuesday at flying club. Limited flights to 50% throttle. Flight timeteas 5, 5, 5, then 7 min flight after verifying with handheld cell checker and maintaining batt after each flight. Experienced temporary #2 motor failure on 4th flight in a climb attitude. Recovered and landed safely. Fellow clubs members wern't sure what happened to make it bank right. Left the flying club and went home and performed a thorough inspection of all systems, no findings. Motors static checked good at home.

Two very short patterns for a flight test again on Thursday at dusk no issues. Very exciting!

Friday- Installed 3c 6000mah batt (just shy of 1lbs) mode 1 works. performed 2 min ground check including very brief 50% and 75% power check, then throttle up to 100% then throttle off. Checked good. 3 experienced Club members were supervising me the whole time.
Taxied to runway, max throttle, shot to 100ft then #2 motor failed, recovered without spin, landed without damage.

Opened #2 pod and smoke was comming out of the rear of the esc. Removed and replaced esc with new suppo 30A as specified in build instructions. Ground tested good, second flight Friday was amazing. The heavier and higher voltage battery allowed the plane to fly with authority, differential thrust was allowing the motor on the side the turn was going into to reduce thrust, corodinated turns were very sharp with only slight drop in altitude without elevator correction.

Three minutes into the flight the #2 engine failed when the Kraken was in a nose down attitude turning onto a long final. Was not able to pull up enough to flair. Went down in a bean field. One prop was the only damage found. Returned to pit area, completed an inspection and batt check. Damage prop found. Replaced prop and installed fresh 3c 6000mah batt.

Ground run at 50% and #2 engine emitted a squeal and stopped. Both ESCs and motors were hot. No idea what's going on!?

Conclusions:
Airframe is very controllable & damage resistant
Control surfaces are very responsive
Diff thrust by rpm reduction is effective
1 Lbs load added to airframe does not affect responsiveness
This plane draws attention because they hear its scratch built and looks great
Powerplant system is not reliable - I can't figure out why! Is a 10" propeller proper for these components? Do I need to go to a 50A ESC?

Justin
 
Last edited:

Balu

Moderator
Staff member
Admin
Moderator
#2
Wow, that was a detailed report :)

Perhaps the ESC need more cooling? Where did you mount them?

What motors are you using? Usually the manufacturer has some suggestions on what prop to use and how much Amp it will draw in that setup.
 

Maingear

Flugzeug Liebhaber
#3
http://www.suppomodel.com/motor/A2217.html - specifications of motor called out in Kraken plans.

I plugged everything back up this morning and smoke pored from the batt lead side of #2 ESC. That makes two fried esc.

9x5 is recommended prop on suppo spec sheet. why is 10x4.5 listed in Kraken build data?

Ventilation is provided by holes in firewall, also cut a scoop in bottom of power pods when first esc was replaced.

I can't say suppo is junk if their specifications are not followed. I'm out two ESCs and can't train my 11 year old son today :mad:

Replace both ESCs and install a 9x5?
 

Maingear

Flugzeug Liebhaber
#5
I had no idea how to check the motor and have been assuming it was an isolated problem. To ensure it was an isolated problem I decided to run the #1 motor at 50%. It ran for less than 7 min. I'm assuming the esc crapped out. Batt still had over 3.8v per cell.

I promptly pulled the pods off, packed them and the two dead escs, and shipped them back to the people I bought them from. An autopesy is in order! I even packed the prop I used.

What did/would you use on your Kraken? (The 6.4 amp hour battery will be used)

Frustrated

Justin