Resurrecting A Totaled Elev-8 Quadcopter

[GlassKnees]

A couple of months ago, I took out an Elev-8 quadcopter that I built and modified for a fun flight outside the front of my house. For those of you who are unfamiliar with the Elev-8, it was a kit that I bought from Parallax, a company in California that sells kits/parts for people who want to learn about robotics. Anyway, I modified the original quadcopter by replacing it's basic flight controller with an APM2 F.C. with GPS and telemetry. The resulting aircraft allowed me to select any of three flight modes at a time (I can choose from a dozen or so and put any three on the aircraft). It had so many features that I won't go into, as many of you are familiar with the APM which has been around for along time. Here is what it looked like:

I loved to fly this thing! It was stable and fun to fly. Then, one day, a couple of months ago, I took it outside for a short flight. It flew flawlessly as I expected. I decided to give it full throttle to see how well it would accelerate vertically - just as it rose about 20 feet, I heard a loud crack and it pitched over and crashed in the street. I thought there was a mechanical failure, but saw nothing come off the aircraft as it fell.

It was totaled. I was going to trash it, but decided to gather it up to see what I could salvage. In the meantime, my wife and I decided to sell our house and move to Colorado. I brought the crashed remains with me. After getting settled in our new house, I set up a work area in the basement and unpacked the pieces:

Looking around, I found lots of spare parts that I had ordered at various times to repair this and two other Elev-8's I had. After conducting an inventory, I decided that I had enough spare parts to rebuild this aircraft But before I begin, I had to try to salvage some things - the wires going through the booms from the motors to the ESC's which were mounted on the center chassis, etc.

I also decided to remove and replace the ESC's and while doing so I made a discovery. The ESC for the #3 motor had a bad solder connection - the bullet connector came right off the wire. The #3 motor is the left front and it suffered the most damage - it came down on that boom and cartwheeled so that the left rear boom/motor took most of the remaining shock and damage. The other two booms and motors seemed okay but on closer examination, one of the remaining booms was slightly dented.

Here is the suspect - note the missing bullet connector on the red (power) lead:

These were 40 Amp ESCs and I decided to replace them with the stock 30 amp devices that came with the kit. But after awhile I began to wonder about changing motors. I have four brand new KA outrunner 1050Kv motors, but I also have a bunch of Tarot 4006/620KV motors. Hmm, maybe I can use these... There is a dirth of information on the Tarot motors and lots of bad reviews. but hey, I've got some and might as well use them. so, based on info I gleamed from other forums, here's what I'm expecting.

After searching through my bag o parts I think I have pretty much everything I need to rebuild the aircraft. I did decide to order a new set of ESC's - will wait until they arrive. Here are the parts laid out:

I'm hoping that the all up weight of the final aircraft to be around 5 - 51/2 pounds. At 50% thrust, I'm expecting to get around 700 gms thrust per motor using 13x5.5 props => 6lb 2.75 ou. I'm expecting to draw 3 A per motor, so with a 5000mah lipo I could get over 20 minutes flight endurance.

This will be a running thread - I hope to add to it as I get into the build and document my progress. At the end, I weigh the aircraft and conduct some endurance tests to see how far off I am with my expectations. Feel free to comment - if you think I'm off on my numbers then please, let me know!

 

[Gyro Doctor]

I heard a loud crack and it pitched over and crashed in the street. I thought there was a mechanical failure, but saw nothing come off the aircraft as it fell.

That "loud crack" sound could very well have been electrical in nature.

 

[GlassKnees]

I agree. I will have to be extra careful when soldering to insure that I have good strong connections. I also have a parallel project going on - a Tarot 650 Sport quadcopter - it is built and has a Feiyu-Tech mini 3D axis with GoPro camera. But when I powered it up, I'm getting an indication that one of the ESC's has a power problem - I suspect a loose connection; #4 motor is affected. I will have to open it up and troubleshoot. I hope to get it resolved and take it out on its maiden flight in a week or so.

 

[GlassKnees]

Update - 10 Jan...

It has been awhile but finally have some progress to report. The ESC's I ordered arrived from Amazon:

I finished soldering bullet connectors and applying heat shrink. I had agonized as to where I would install the ESCs - underneath the motors or in the center chassis as the original kit was built. After considering which wires would need to be lengthened, I decided to mount them in the chassis.

I decided to use velcro to attach the ESCs to the chassis as opposed to zip ties because the slits on the chassis plate were not conducive for securing with zip ties. Another change I have to make is I have to fabricate a new set of leads (3 per motor) from the ESC's to the motors. The leads I salvaged are too short. I made one and attached it to one of the ESC leads for the #4 motor:

I will have to custom make the other wires in order to provide enough length to attach to the motor to facilitate motor replacement without having to take apart the whole aircraft. I don't have enough wire to fabricate all the leads I need but I have some ordered - may be another week or so before report again.

 

[Gyro Doctor]

... Don't forget to allow some length for a slight "service loop".
You'll want to be able to access or move some things without the need of unplugging them.

 

[GlassKnees]

Absolutely Gyro doctor! This was a problem with the Elev-8 kit - it was a pain if you wanted to replace motors. I plan to have enough slack so that I can easily change out motors if I have to. Just waiting on the wire to arrive so I can continue. I need to double/triple check solder connections also!

 

[GlassKnees]

Status 1/21
So, last night before going to sleep it occurred to me that I need to solder some bullet connectors to a couple of the Tarot motors I plan to use. Afterwards, I can test them out. Here are the motors I picked out of the pile:

To test each motor, I pulg it into an ESC, connect the signal servo connector to the throttle port on an R/C receiver and plug the power leads of the ESC into a lipo battery - in this case, the one I will use for initial flight testing. The ESCs have a Battery Eliminator Circuit (BEC), so the red wire on the servo connector will supply power to the receiver. I turn oon the transmitter and move the throttle stick all the way up, then plug the ESC into the battery. The ESC senses that I want to calibrate it, so I get two beeps, I throttle down, get three beeps and the all clear signal and I can then throttle up the motor:

All four motors are working and the solder connections appear to be good. So now I'm still waiting for the wire that I need to run through the booms to connect the motors to the ESCs that will be mounted in the center chassis. Stay tuned....

 

[GlassKnees]

Feb 11 update:

It's been awhile since I posted anything as I was waiting for 14 awg wire which I ordered from Amazon - took forever to arrive from China and I realized that I didn't order enough, DOH!!! So I've ordered some more from Walmart, as the supplier I bought from is now out of stock.

Meanwhile, you may now about the crash that occurred with my other modified Elev-8:

I have looked at connections and so far have not seen anything that looks like a bad solder job, so at this point I don't know what caused the crash. MY Tarot 650 Sport is grounded in the meantime - partly because I had only one 6S lipo and it was destroyed in the crash, but mainly because I don't know the cause of the Elev-8.

Although the Tarot flew well, I was unable to get the landing gear to retract. I ordered a new landing gear controller, thinking that the one that came with the kit was defective, but while getting the aircraft ready for test flights after moving from Texas to Colorado, I discovered that I did not properly install the landing gear. I fixed the problem, but prior to that, I had ordered a replacement landing gear controller, which arrived. So, today, I thought I'd do some troubleshooting.

I spliced power/gnd wires with a JST connector to the power/gnd leads of the controller, and plugged it into a small 3S lipo for power. I then plugged one of the landing gear on the aircraft to the controller, and the servo connection from the controller to the Gear port on a six channel receiver I had lying around. I used an ESC with a BEC to power the receiver. When I powered up the landing gear controller and receiver and hit the gear switch on the transmitter, the landing gear retracted! Woo Hoo!!! I will hook everything back up as it was, and try again - if it works, I will have to buy an 8 channel receiver as I need 7 channels: 4 for controlling the aircraft, 1 for switching between flight modes, 1 for gimbal tilt control and 1 for controlling the landing gear.

in the meantime, I'm seriously considering redoing all solder connections on motors, ESC's on the Elev-8 to make sure that all solder connections are okay...

 

[GlassKnees]

February 18 Update:

The remaining wire I needed arrived yesterday and I was able to complete routing power through the booms to the motors. But there's not much space in the chassis. I had to pretty much take everything apart in the chassis and try to put it back together - here is the completed wiring, including power distribution and APM power module:

It took a lot of coaxing but I managed to get the bottom chassis plate installed. Here is the bottom with the landing skids added:

And here I am now, with the APM flight controller and receiver mounted:

Things remaining to do:

• Install the #3 motor, and verify that all motors spin in the correct direction.
• Level the mounts and tighten mounting screws
• Install telemetry transceiver
• Begin configuring the APM: Accel, ESCs, compass, radio, flight modes.
• Double check other parameters: Voltage failsafe, radio failsafe, RTL altitude, Waypoint speeds

The weather here is windy and a snow storm will be coming in a couple of days, so I may not get to test fly it for a week or so.

 

[Jackson]

But there's not much space in the chassis

Ya think?

 

[GlassKnees]

February 21 Status:

I had to open up the bottom chassis plate to reposition the APM power module in order to get more slack to the leads going to the APM itself. I also had to get more slack to the wires going to the #3 motor. All that done, I leveled the motors and tightened up the mounting bolts:

I then took it upstairs, connected it to Mission Planner on my laptop and did the accel, compass, ESC, radio calibrations, checked the flight modes, and failsafes. I need to go to the hardware store to get some velcro to secure the battery; otherwise, I think it's ready foor its maiden flight:

And here it is next to its bigger brother, the Tarot 650 Sport:

 

[GlassKnees]

I had success today! I had to replace flight controllers and a balky engine (#3), but after all the APM configurations, I was ablle to get it to arm, fire up the motors and disarm. So I installed the propellers and took it out to a nearby parking lot. It armed after getting GPS lock and I took off - it was very controllable and when I switched to Loiter mode it held its position. RTL mode worked fine as well. I switched back to manual (Stabilize) mode before it landed and flew it around briefly before landing it.

Unfortunately, I had no video as there is no on board camera and I was alone. Perhaps I can get someone to come out with me next time and shoot video.

 

[Jackson]

I had no video as there is no on board camera and I was alone.

I see lotsa folks using a tripod.

 

[GlassKnees]

I will try to get some video this morning - will fly a waypoint mission and use a camera mounted on a tripod. BTW, I managed to find some thrust data on the Tarot 4002 620KV motor - specs are hard to come by but a Russian guy ran a test on YouTube:

Here is the thrust/current curve along with my estimates of where 50%, 75% and 100% thrust levels (black vertical bars) are ( a 13"5.5 propeller was used):

I am using 12" propellers and I'm in Colorado at about 5000 ft elevation, so I don't know what kind of endurance to expect. The aircraft weighs 2.086 kg (including the lipo), and I'm expecting to draw around 7A current from an 8000 mAh 4s lipo. The waypoint mission is small - just a demonstration of it's ability to fly autonomously. Also, the temp is around 18 degrees F. so I won't have to worry about overheating motors!

 

[Jackson]

Also, the temp is around 18 degrees F

Batteries don't like the cold.

 

[GlassKnees]

The following video pretty much covers what I posted here but also has video of two test flights:

 

[Jackson]

Looking good.

 

[GlassKnees]

A footnote:

I just returned from a trip to Singapore to visit my son, his wife and their brand new baby. Anyway, while there, I ordered an FPV camera and video transmitter from Amazon - want to try out the FPV experience using the Elev-8. The components arrived before I did, and this morning, I hooked it up and installled on the aircraft. Here, I connected them up after fabricating power/ground leads using bullet connectors - I have a spare pair set of bullet connectors on the power distribution system on the aircraft that I planned to tap into. Here is the setup pror to installation:

Here, I test to make sure that I get a clear signal:

Here is the camera and vtx installed on the aircraft. The vtx is mounted underneath on the right side with the antenna pointed downward:

Finally, a power up test:

Note the Tarot quad in the background - I also received a small 450mAH 3S lipo for the Tarot to power the gimbal and vtx - chose to use a separate power source. I got careless with the previous battery pack and let it discharge too low. Now both aircraft are ready for video flights using my brand new video monitor/dvr!