Following the “impaired servo” thought-line, I noticed that the motor mount is 3D-printed. Could it be possible that it’s flexing due to the prop torque causing it to bind? Does the log show an unusually high amp draw at transition; within that 5-second time frame? The ground test with full throttle could definitely reveal that, if it was the case.
Good luck.
Hello Rollys,
The motor mount / tilt mechanism is both very tough and stiff. So that is unlikely. From the logs, I didn’t notice a noticeably high current draw during transition. Ground test with props off didn’t reveal much either. As the next step, we’re planning on conducting a props-on full-throttle ground test in a few days time to simulate the situation at ground level.
Thanks,
Wasim
I’m in the process of testing a four-motor quadplane with the front two tilting. I can confirm that vectored yaw works just fine, the same way it does on trimotor builds.
Brilliant. Thanks James (& Greg).
Hi Greg, in regards to your earlier post where you mentioned that you don’t believe this is an issue with tilt servos/mechanism. Something to bear in mind is that the RCOU PWM values for both tilt servos were identical. You can also see that in the graph you posted earlier (the green line for RCOU C14 sits behind the red line for RCOU C13 and the max/min and mean values are also identical). However, the right tilt servo did not physically move, which is very clear from the 4 x video frame grabs I posted above.
Based on this, would you not agree this is a hardware failure?
By the way, we do have a pitot, but we overlooked the parameter to make it active (doh!). Still, some are flying VTOLs successfully with synthetic airspeed calculations, so this should not be an issue. Even if airspeed measurement was an issue, it would not make one tilt servo react differently to the other.
Not intending to pick an argument here, appreciate your input as always, but would just like to understand why you have disregarded hardware failure when that seems to be the only logical conclusion.
Cheers,
Jacques
Hi Jacques,
I think these discussions are well intended so I never feel they are argumentative. We all learn from the various setups…both successful or not.
My point in disregarding the tilt hardware was based upon your previous projects. You are a meticulous builder and have made many interesting and awesome conversions. So my assumption was that you have already tested the tilt rotor hardware many times. Further, we are using similar (if not exact) components on other projects like the Nimbus 1800 VTOL and experience no tilt rotor issues when the motors are spinning.
One difference I see in your project is that you are not using vectored yaw. Thanks to James, we have confirmed that it is now a possible option. Another difference is that in previous projects similar to yours, I have seen both front tilt rotors tied to the same mechanism or output channel so yours is slightly different.
I wish I could pinpoint a solution but there are many variables. I know that swapping out the tilt servos is not an easy task but perhaps it will fix the problem or let us look elsewhere.
Cheers!
Hi Greg, thanks, flattery is always welcome 
In this case, if it was a hardware failure due to workmanship, then that will sit with Wasim, as he built the aircraft and I’m just doing the testing
But I can tell you it is very well built. I actually had some concerns about the first 3D printed parts he was using for the motor mounts, but he printed some beefier ones and they are very strong indeed. One thing I’m leaning towards is possibility of the BEC not being able to maintain sufficient current for both motors. We are going to check that out and also do some ground tests at full throttle and try actuate the tilt.
Thanks,
Jacques
Sounds good, Jacques. On our Nimbus VTOL, we have one 6v BEC per tilt servo. I used the Turnigy 5v/6v 5A (8-26v) SBEC at Hobby King.
Our current setup uses a HobbyWing 10A (20A) UBEC (www.hobbywingdirect.com/products/ubec-10a?variant=1013205920)
I think this is quite a powerful BEC, but there is always the possibility of the one we’re using being impaired.
Hi folks,
Here’s an update: After a series of ground testing, we’ve identified the problem - it was the case of an impaired BEC, and we’ve managed it sort it now. Thanks for your help.
However, I have got another question regarding yaw control in vectored tilt-rotors. When a plane is configured as a vectored tilt-rotor, does the yaw vectoring work in conjunction with differential (quad) motor speeds to control yaw, or is it just vectored yaw (without the use of differential speeds in quad motors)?
Regards,
Wasim
Hi Wasim,
Glad you got it sorted. Based on the hover throttle graph on the Nimbus with vectored yaw, I would say that only the tilt rotors are used in Q modes.
Happy Holidays!
Thanks Greg. Happy Holidays to yourself and everyone else here
Yes, the vectored yaw does work in conjunction with the motor torque. Greg’s setup doesn’t do this because it’s a tricopter-type frame, so there is no way to properly use torque to yaw while remaining stable. This is true on all tricopters, not just vtol tricopter-planes. But on a setup like yours, it will still use motor torque.
That’s great. Thanks James
Hi James,
I don’t see this defined in the Wiki so I was wondering what is the parameter (or parameters) that defines yaw via tilt rotor or yaw via motor speed (or a vectored yaw aircraft)? Is it Q_FRAME_CLASS? Are there any illegal combinations?
Nimbus VTOL Setup
Q_FRAME_CLASS,7 (for Tri)
Q_FRAME_TYPE,1 (for X)
Q_TILT_TYPE,2 (for Vectored)
Q_TILT_YAW_ANGLE,13 (degrees)
Cheers!
I’m not really sure on that regard, you’d have to experiment. I’d imagine having frame class set to tri would overrule the frame type setting.
My rig is very similar in configuration to Jacques’ build, a quadplane based on the MFE Believer platform. Frame class is 1 for quad, and frame type is set to 3 to make it an H quad. (this is to have correct prop rotations when in forward flight).
I don’t think there is any parameter that specifically enables or disables motor-torque yaw - If the frame class allows it, it’s enabled. If the frame class does not, as is your case, it relies on tilt.
Maybe this is something we should ask the devs for? On quadplanes with low power-to-weight ratios, a loss of total power can be observed because it maxes out two motors during yaw movements or corrections, while the other two go low. I’ve had issues with my own setups in this case, especially when flying in wind.
I’ve noted that AUTO flight is especially susceptible to this. On a smaller, non vectored build, it flew fine in q_stablize/q_hover and was even able to q_loiter, but went haywire on an AUTO takeoff due to lack of power. I fixed it by upping battery voltage, but I suspect that going to a vectored-only yaw would help as well.
Ok, thanks for the information. None of my Quadplanes have tilt rotors and all four of my tilt rotors are tricopters. I’ll ask our question in the dev tilt rotor thread.
Hopefully, Rolf won’t yell at me for double-posting. 
