CARS II

My Feedback: (7)

I'm using the right lower knob for the gyro gain but converted it to a digital trim, so far it has worked fine, one of the nice things about making the knob digital is that the trigger point can be adjusted, when you are increasing or decreasing the gain the trigger point can be moved to the 11' and at the 1' position, when I'm done with the Assist gain adjustments then the trigger point is moved to the 7' and 5' position, this way it will take a lot of travel on the knob to get to the trigger point.

The left lower knob is going to be used for the throttle kill on my two gassers, the trims are crossed and using the throttle trim to set the engine ready and to stop adjusted to 100% which gives 3 steps, go up two steps and the turbine is ready for a start, 2 steps down and it is shutdown, if by a chance I touch the throttle trim bottoms when the engine is running then the trim goes one step down but the engine keeps running till it goes down one more step, I have no concerns if that happens, I know the engine will keep running because of that I use the trim bottoms.

CARS II

My Feedback: (7)

Thet top inner left, long, 2 position switch is used for the gear, there has been two occasions when I bumped the switch and the gear came up somewhat on the model while on the ground, also in a few occasions I felt like flipping the switch but stopped myself from doing it, all this when landing mostly, because of that I decided to swap the 2 position gear switch for a locking switch to prevent any other incidents.

CARS II

My Feedback: (7)

Around 20 years ago or so, I used to fly my prop planes and listened to music at the same time, of course, I had my CD player hanging off my belt and used a headset, the one with the foam covers well, I still like to listen to music while flying, this where I was disappointed that the DS12 didn't have an FM tunner build into the radio like the DS24 BUT, no fear I can download music in MP3 in the radio and play it to my heart's content I will be doing that soon, I occasionally like to listen to powerful music while fflying, this is one of the futures among many that attracted me to Jeti ( they can keep the games )
I now have to figure it out how to turn the music on and off ( help Harry? )

CARS II

My Feedback: (7)

I will be doing a video soon on what the vibration analysis looks like on all 3 axis ( x,y,z ) when the engine is running ( thanks to my friend Raffy for showing me how to do it ) I will start with my Boomerang XL on Thursday, keep an eye for it.

Dansy

My Feedback: (53)

not Jeti fault but obviously that pump is not made for a on/off quickly, the sequence is pretty hard on the pump/esc....the PowerBox jet work find in that mode...

CARS II

My Feedback: (7)

Totally agree with you D, I came to the same conclusion, that the pumps are OK to use as they were designed, that's the reason why I returned the spring loaded switch back but, I also removed a 2 position switch on the front right and replaced it with a 3 position switch in preparation for when I get one of the newer smoke pumps.

Dansy

My Feedback: (53)

I also never bump the switch on TX for anything.....and my gear switch is on the throttle stick midway.....(small button) and the top is my flight mode, get used to where they are and doing the same for all model, I think is the key....my other stick has the same button and switch (smoke and Gyro mode)

it’s just to get used to their location....

CARS II

My Feedback: (7)

Here is my vid of the vibration check on the X Y Z axis on the Boomerang XL, this was done without the wings, booms and stab, with those parts on there is less vibration, specially at nearly 100% throttle.

Jannica

I don’t knew how many of you out there who use a transmitter tray? But if you do you probably want longer sticks. I have made some to be made on a 3D printer and the file is free for download here. I also made larger knobs for the top two potentiometers on the DS-12. Feel free to use them if they suit your preferences.



Large potentiometer knob for Jeti DS-12 by Gitarritzan - Thingiverse





Jannica

Sweden

CARS II

My Feedback: (7)

We maiden my friend's T1 this passed weekend and this what we saw when we were performing the vibration checks, the picture shows the most significant vibration out of all 3 axis, it looks like this is the spot where the receiver picks up the most vibration and at around 90 to 100% throttle.

I haven't seen that much vibration on any of my 3 jets, one reason may be that they are made out if wood and that wood absorbs the vibration better that fiberglass, my wood build jets have many more points where the wood is touching and that also may be helping absorb vibration, the Boomerang is of a composite build and having thicker skin and been bigger may also help absorb vibration better than the smaller jets, all this is speculation based on what I have experience with the jets and Jeti receivers so far.

HarryC

My Feedback: (1)

CARS II, if you think you are investigating the acoustic interference problem then you are barking up the wrong tree! The problem is caused by sound waves in the ultrasonic region. The Assist vibration monitor detects mechanical vibration, not sound, and at a fraction of the frequency of ultrasonics.

camss69

My Feedback: (46)

Hey Harry, how was it determined that it’s an acoustic issue? If it’s pointed out that it was determined to be an acoustic issue in another thread can you share the link? i just haven’t run across it myself. It’s my T1 that has the REX7A mounted in it that was maidened this past weekend with the Assist left off based on the vibration issue noted in the screenshot. I contacted James at Esprit and he said “ it is a harmonic resonance issue and occurs at specific resonant frequencies.” Are we all talking about the same thing here? Acoustic or harmonic resonance, is that the same thing? Just trying to get an understanding of what exactly the issue is. I was pretty disappointed to not be able to use Assist in my plane this past weekend.

wfield0455

My Feedback: (7)

Just out of curiosity, which turbine was this ? There were a couple of people before that had issues with the Assist in Jets and I believe they both had the same brand turbine ?

Also, did you do the vibration analysis first and leave the Assist off because of what you saw or did you do a run up on the ground and have control surfaces start twitching and decided to do the vibration analysis based on that.

camss69

My Feedback: (46)

Brand new K160 G2.
We turned the gain all the way up on the gyro, then did vibration analysis/run up and during the run up noticed the elevators twitching.
The elevators twitching and what we saw in the screenshot above is why I left assist off.

Very interested in your and Harry’s input on this.

Thanks!

HarryC

My Feedback: (1)

MEMS gyros are prone to interference from ultrasonic sound at the high frequencies at which the gyros vibrate. It is a well known phenomenon. Totally unrelated to piston engine airframe vibration which is mechanical and of low frequency. Model jet engines are capable of generating the inaudible ultrasonic sounds which can interfere with the vibrating parts of the gyro. MEMS gyros are not solid state, they have moving parts but are so small they can be made on a chip. The effect of the interference is control surfaces vibrating or even kicking to maximum deflection. This happens at certain rpm. It is specific to an engine, another identical engine may cause interference at different rpm or no interference at all.
The cure is high quality gyros and very sophisticated software, though afaik no brand has been able to eliminate it entirely, just make it extremely rare.

wfield0455

My Feedback: (7)

I'm rather curious where vibration in the ~300Hz range would be coming from as I can't really see how that could be coming from the turbine.

When you mounted the Assist did you simply use the foam tape provided or did you also strap it down with a zip tie or Velcro strap ? Straps that are pulled too tight can reduce the effectiveness of the foam tape.

If you believe it's acoustic interference, the Cortex used to offer what they called a hush blanket (or something like that) which was basically a fairly dense foam box that could be placed over the Cortex to act as sound insulation. You could try to fabricate a small box out of foam and place it over the Assist and see if that makes a difference.

ww2birds

My Feedback: (14)

For what it's worth .. I tried an Assist receiver on my Reaction 54 (my test plane for anything new or scary!). It's powered by a Jetcat P100. I have been a longtime Cortex and Cortex Pro user, and I do recall the early days and the acoustical hood that was recommended for turbine use.

I was really excited to try the Assist RXs but saw the same issues being discussed here ... with very strong jittering of the gyro-controlled surfaces at various throttle settings. It was honestly alarming to watch on the ground, especially on the elevator. I never turned it on in flight.

To be honest, I did not try really hard to troubleshoot it .. there are other issues with the assist from a systems point of view in my opinion .. for example the use of backup receivers that are or are not stabilized. Seems that this was not thought through very well by Jeti.

I will be interested to see if the Jeti team can make changes to the Assist firmware to address these issues, I believe that's how the Cortex team did it.

Dave

wfield0455

My Feedback: (7)

As for the issue with servos twitching at various throttle settings, that sounds like acoustic interference but as you say, you really didn't try to trouble shoot it. Personally none of my Jets have this issue with the Assist so I'm not really qualified to comment on that. Assuming Jeti used high quality MEMS gyros in the Assist (they claim they did) it should be able to be resolved with a firmware upgrade.

As for the Assist not stabilizing a backup receiver, there is no such issue if you actually want it to be and connect it accordingly. You simply need to connect the backup receiver directly to the Assist and if you do the output will be stabilized even when the signal from the backup receiver is used. If you're concerned about the Assist being a single point of failure, the Cortex Pro is the same. When using a Central Box, it you connect both receivers to the Cortex Pro in order to have both stabilized then the Cortex Pro becomes a single point of failure, same as if an Assist is used with backup connected direct to an Assist. There are many different ways to configure things and you need to chose which is important to you and select a configuration that you;re comfortable with but to say backup receivers aren't stabilized is not correct and the Assist is no different than the Cortex Pro in that regard.

I'm not trying to say the Assist is better or even as good as the Cortex Pro, just trying to clear up what appears to be a VERY common misconception about the Assist.

ww2birds

My Feedback: (14)

Hi Wayne,

I think you know I am a very happy and very loyal Jeti user .. and I was really hoping the Assist would be a good solution. And I suppose I owe it to them to do at least a little troubleshooting ... but having "seen this movie before" with the Cortex, I figured they would address it and I'd try again when they did. I used the latest firmware as of mid last summer when this all happened. Do you think they have done anything to address this problem since then?

I am encouraged that you have not seen it in your planes. Surprised but encouraged .. it was NOT a subtle effect. Perhaps if it is very high frequencies of vibrations the fact that it was a small turbine with a very high full throttle RPM had something to do with it.

Yes, I am familiar with the many ways to connect receivers to central boxes, and how to work around the single point of failure issue .. I have had many discussions with Danny about it and learned what others have been doing and some of the different setups people use. And if you break the single point of failure on the Assist, and let the CB choose the RX you'd be choosing back and forth between a stabilized stream and an unstabilized stream or between two different stabilized streams. This may or may not be a practical concern. But it seems like a stand-alone Assist module that attached as a "plugin" to the CB would be a much nicer design. That's something Jeti as the system owner could do that would be a value-add compared to an add-on like a Cortex or an iGyro. The iGyro effectively does that with their high end powerboxes...

As one of the config gurus, what is your recommendation for setups -- one of two 2.4s? where to connect the 900? I started with two 2.4s in dual path, and one 900 .. all connected directly to the CB, or through the Cortex if I have one installed .. and since then I have mostly migrated to one 2.4 with the 900 coming in to the EX backup port which from my experience seems to perform better .. at least as measured by fewer low signal alarms. But I understand that link quality may not be measured the same way with dual path or "classic" connections .. again maybe you can shed some light on that ... perhaps this is not a real link quality issue but a different measurement issue.

In 2019 at Top Gun a LOT of pilots had signal issues over one particular area of land .. and sure enough I had "switching to 900" alarms at the same place on almost every lap. I did a plot of the signal quality with Jeti studio and color coded the Q level on the 2.4s and sure enough, it was much lower in the area where the other radios were having issues. Gotta love that backup RX.

Thanks for the thoughtful reply.

Dave

camss69

My Feedback: (46)

The assist is mounted using foam tape on a painted piece of plywood. It is only mounted with the tape and does not have a zip tie or Velcro strap over it. Danny at Aeropanda did recommend building a foam lined box to put the assist inside. It is in the bottom right corner of the picture.



I was wondering if the box would also help with the acoustic interference problem as well.

camss69

My Feedback: (46)

I had an issue with my engine on the second run. The recommendation from Kingtech is to run it on the stand and see if it has the same issue. I’m going to leave the pump and ECU in the plane and I have some spare cables and I’ll run the fuel line outside to the stand. Obviously the plane will need to be close to the test stand. If it’s acoustic interference I should see the same issue with the engine next to the plane running on the test stand? If it’s vibration related I shouldn’t have the problem with engine running outside the plane.

What do you guys think? I’ll take pics of my setup once I get it ready to go, sometime this week.

wfield0455

My Feedback: (7)

Dave,
I honestly have no idea what may have caused the issues you saw with the Assist causing control surfaces to twitch / jump at some throttle settings. It certainly sounds like acoustic interference but I don't believe it's a wide spread issue with the Assist but Jeti really does need to address it or provide some guidance on how we can avoid it. Still I have jets using K45, K60, 2 ,K140s and a Jetcat P120SX all flying with Assists and I haven't had the slightest issue with any of them.

As for redundancy, it would probably make everyone's life MUCH easier if Jeti offered a Central Box with built in Assist that would allow you to have 2, 2.4Ghz receivers and a 900Mhz backup all of which would be stabilized. If your current configuration is a single 2.4Ghz receiver and a 900Mhz backup that can be duplicated with an Assist pretty much the same way as with the Cortex Pro. Simply configure the 900Mhz receiver for Ex Bus output, configure E1 or E2 on the Assist as an Ex Bus/Receiver Input and connect the 900Mhz Rx to it. Select Stabilized Ex Bus output in the Assist and connect the Assist Ex Bus output to the Central Box. Both 2.4Ghz and 900Mhz should be stabilized.

Hopefully Jeti will get to the bottom of this acoustic interference issue soon but if they don't get reports from a significant number of users it probably won't be too high on there list of priorities so ideally everyone that has had similar issues should contact Jeti's support people and report the issue,

camss69

My Feedback: (46)

There was at one time supposed to be an external assist, support for them was listed as one of the features of the new CB’s.
I had an REX12A in a T1 Mini with K85 and never had any issues with it in almost 70 flights before I sold it. I also never did any type of vibration testing so it may have seen the same or similar results as the one I have now, I’ll never know. However it was mounted in one of the 3d printed mounts that Pacific RC Jets sells and not mounted with the double sided foam tape.
I am wondering if I would see the twitching surfaces at the default gain setting instead of gain all the way up. The mini with the REX12A I flew at the default “Jet” setting in assist. I doubt I will be flying this plane at 100% gain setting anyway so I may test that as well.

CARS II

My Feedback: (7)

A friend of mine made me a pair of trim hats, I used double side tape to secure them down, 4 small circles, one for each buttom, next time I will cover the entire face of the hat, this way I don't have to guess the position of the buttoms, tried them already flying my Boomerang, feels good and easy to find, it only requires a light push.

Any one interested to try them, let me know, my friend is willing to make more.

ravill

My Feedback: (11)

Post pics Carlos!

They look like the grumania trim additions.