Commander_Drake

My Feedback: (2)

My electric Hobbico Twinstar crashed this morning. The onboard camcorder caught it all:

http://www.youtube.com/watch?v=xEf9_9i8nMw

You can hear a motor cut out then you can hear me fiddling with the throttle and trying to get both motors going again. I have had several good flights with this setup but now for some reason the ESC's seem to be competing with each other for current.

Here is the setup:

2 MP Jet 28/20-7 motors, 2 Phoenix 35 ESC's, one Thunder Power 3S2P 4200 mAh LiPo, 10x7 props.

There is not much damage to the plane and it will fly again soon. The nylon wing bolts sheared, the fin broke off cleanly at the base and the nose got a little dent. It didn't even rip any Monokote. I'm not sure what to do about the problem. A LiPo that can supply more current? Separate LiPo's for each motor? Higher rated ESC's (I'm pulling about 50 Amps from the battery at full throttle)? Some torroids on the battery cables?

Sessholvlaru

Wow, the noises that thing made were sure interesting. Kudos on the flying skills, it seemed like you fought it forever. Glad to hear the damage was minimal. Maybe not enough in the speed controller department?

Commander_Drake

My Feedback: (2)

Sessholvlaru, Thanks! Yea, I'm thinking I need to go to 45 amp ESC's. Big bucks for two of them though

Kensonic

How are you powering the radio and servos? Are you using a separate battery or are you using the BEC in the Speed control? If you are using the BEC, have you disconnected the power lead on one of the two speed controls? I'm flying a Mulitplex twin jet with two Warp 4 brushless motors and two Thunderbird 18 speed controls with two 3S2100 LiPos (one for each controller and motor). I'm using the BEC from one of the Thunderbirds with the power lead disconnected on the other. This works well.

Arrow IV

No Offence Guys,
I can't wait till the rest of the gang reads this thread!!! This is a ele vs gas debate if I've ever seen one!!! There will be some gas guys foamin at the mouth to get a bite of this one (pay back for the B-25 thread)!!! Let the games begin!!!

Commander,
Cool views man! I get a kick out of what the "plane sees"!!! Good stuff!!!

Commander_Drake

My Feedback: (2)

Arrow, All are welcome to debate but source of power is a minor issue to me. I fly both a glow and electric version of the Hobbico Twinstar and enjoy them both. Could be rubber band or fusion powered, I don't care. Flying is the thing.

Kensonic, Thanks for the ideas. I'm not sure if I can disconnect the BEC power on the Phoenix ESC or not. I'll look into it. I have had many good flights with this setup and have posted several videos in the members video section. There was occasional glitching but nothing like this last flight. On the test bench everything seems to be working fine again. I'll get to the bottom of it eventually. I might give Castle Creations a call.

PS. I am not using a separate RX batt.

NorfolkSouthern

I must admit, the sounds of them motors was funny. Sorta like R2D2 malfunctioning! I'm glad to see it'll be back up and running again, though.

NorfolkSouthern

CGRetired

My Feedback: (1)

I don't quite understand Arrow IV's post. What does this issue have to do with debate between ele and glow? This is a simple engineering issue that, when solved, will provide Commander Drake enough information to fly his Ele Twinstar.

I fly both Glow and Electric and enjoy both. I must admit that I have experimented more with Electric because I don't fully understand all that is necessary for a good, performing electic flyer, but I'm getting there. It's mainly an issue of my abilities as an RC pilot and getting used to the way we fly electrics vs how we fly glows than it does with anything else.

Nope, this is not a debate issue, it's simply someone looking for help to get his electric flying correctly.

Drake.. let us know what you find out. I am interested in flying a dual motor aircraft and your input will help a lot.

Thanks.

DS.

Arrow IV

Boys,
I don't really care what yall fly, gas, glow, ele, nuclear... whatever, if it works for you great, go have some fun!! If this is a "engineering" issue then good luck to you boys. I'll just take my "Pilot 2 cents" and put them on deposite where they can earn some interest. Good luck with the "engineering" hope it works out.

Jim C.

ahh man, you were ok untill you turned right, I didnt read all the posts, but I bet the right one quit. always always RAISE the dead engine in a turn. But I also noted that if you did, you would have hit the tree... good job nonetheless!

Dc2LightTech

This is an electrical engineering issue! try installing line filters to the input of each ECS's, or better yet, use separate LiPos with filters for each motor. do you have caps across the motors?

Dc2LightTech

and keep all wires from the battery to the ECS and the motor as short as possible!

Troy-RCU

My Feedback: (1)

Not a good idea with BRUSHLESS motors

It may be an issue of the esc's cutting out with interference... many have that fail-safe function built in so you don't have runaway aircraft in the event of radio issues. The motors will sputter and try to shut down if it gets erratic signals. Good luck getting rid of your Gremlin.

Commander_Drake

My Feedback: (2)

LOL. I was wondering when someone would bring that up. Unfortunately, by that time the plane was out of sight behind the trees so I was flying by guesswork and trying to avoid hitting a tree. The fact that I succeeded was pure luck. You are correct though, and the video is a good example of what happens when you turn toward a dead engine.

Thanks to all for the suggestions. I'm going to try separate LiPo's and shorter battery cables, and perhaps some filters too.

iron eagel

Your motors are rated for 25 amps max so the 35 amp esc's that you are using are more than good enough.
With two engines on one batt at full throttle you may have dropped the cell voltage below the cut off voltage for an instant, just long enough to shut one motor down (just a guess).
But it is probably more likely that you had some rfi issues. I would do as they have suggested regarding the filters and lead dress, but more important get another batt and run each motor with its own power source.
Also, check the battery with a cell balancer, to be sure you are not dealing with a bad cell also...

Kensonic

Commander_Drake

Thanks for the reply. If you are using two speed controls with both BECs connected, you are going to have issues.

" PS. I am not using a separate RX batt."
< Message edited by Commander_Drake -- 10/18/2006 4:33:50 AM >

In this configuration, you have two linear regulators trying to supply current to the system and they will fight each other. This is strictly a no-no. What I do on my twin brushless setups is use a Y-harness to drive both ESCs from channel 3 and then cut the RED wire to one of the ESCs. This will disable the BEC from one of the speed controls and allow the other ESC to provide power to the system.

Kensonic

Commander_Drake

My Feedback: (2)

Hmmmm .... I'm using separate RX channels for the two ESC's and I have programmed in differential thrust to go along with rudder movement, although I usually leave the mix switched off. But I guess that dosen't make any difference. I can still cut one of the red wires coming from one of the ESC's to the RX.

Dc2LightTech

I would cut the red wire to both ESC's and use a standard RX battery to keep the noise out of the receiver.

I am building a twin Seagull dual ace (i would upload pics but I cant figure out how to do that). I only ordered the wings and am making it like a P-38. how are you programming for differential thrust ? I will also use the twin rudders as air-brakes...

Commander_Drake

My Feedback: (2)

pj, There is a nice step by step description of setting up the differential thrust here: http://www.rcgroups.com/forums/showthread.php?t=489099

To upload pics, don't use the quick reply section. Click on one of the reply buttons at the top right of a message and then under the area where you type the message you will see "Click here to upload images and files". Pics must be gif or jpg.

Dc2LightTech

here is a pic of my current project...

iron eagel

oh yes Kensonic is quite right in his observation about the power system flaw, lift one red lead as he said.
Or use a seperate RX batt as suggested by p

Commander_Drake

My Feedback: (2)

I clipped one of the ESC power leads to the RX and everything still functions fine, including the differential thrust. However there are still signs of glitching.
On looking things over it seems obvious to me now that the battery leads are just way too long. I had to route them through the nacelles, the wing and into the fuse where I have a hatch for the battery. I'm going to change to sepatate packs for each motor and mount them right behind each motor in the nacelles. I'm going to have to add more weight to the nose though, so I might as well cut the other ESC power lead and put a separate RX batt in the nose.

Dc2LightTech

check this schematic...