Problems!! 14MZ 2.4 R6014FS

[Judge]

See this post:

http://www.flyinggiants.com/forums/443854-post62.html

He took a RX, placed it on a piece of black paper on his driveway. He covered that with the glass lid from a cooking pot to simulate the canopy and to trap heat.

He could not get his RXs to show this behavior.

[grayuk]

Yes, I saw that one but, I do not know if the rest of the gear was in sun or not.
If we assume it was not then maybe....there is a fault else where.
But, what is not clear is if the rx, in his case was enclosed all around (as it would be on an installation) or if just sitting on the paper with glass on top.
If that was the case then it is not a fair test of what is being described in the other failures. Air can move around too freely and remove heat.
I am not being negative here; I just want to be confident that this is a real problem.
I spend my life discovering and fixing issues in all manner of equipment, from military to medical.
It is critical to ensure that tests are definitive and not hiding another issue. (See the post on the vanilla ice cream!). It may be that this is actually an rx fault, if so, we can take measures to work around. But if it is not and we are all fooled, we are hiding another problem that will bite our ‘ass’ again when we least expect it. This is why Futaba will not ‘jump’ until they have had time to fully prove one way or another, then take the ‘right’ action.

I was once called to fix some medical equipment that failed on a regular basis, normally around 4 pm, but only on certain days and at certain times of the year! Strange but true (vanilla!) Other engineers had been in an failed to resolve the problem. Well after much head scratching I found the problem.
IA building opposite had a glass front, and at around 4pm in certain months, the sun was in the right position (but only if it was hot and the windows were open) light reflected into the room and onto the optical measurement sensors! This was enough to throw them out and give false readings! Now how weird is that?

Paul

[reyn3545]

If "breathing" holes were manufactured in the plastics, it would only allow the hotter to enter the case faster. Remember, the problem (at least in our minds) is not heat generated by the receiver, but ambient heat and its impact on the unit. Now.. breathing holes AND a fan... hmmm...

If no answer is found.. they'll be handing out flack jackets and helmets at the Tucson Shootout!!

In the same vane as your ice cream story... I used to sell PC equipment to BellSouth, a regional telecom provider in Atlanta. They opened up a new server room on one of the floors of the tower downtown, and once they got it up and running, they noticed that they were experiencing a high outage rate on the servers in this room. We had the PC manufacturer in several times to investigate possible power supply issues, electricians were in several times to look at available power, and I don't know how many people working on different aspects of the problem. Then, as Bellsouth was putting together a list of all recorded failures, someone noticed that they seemed to peak around noon and 5:00, and only on weekdays.... Yep, by now you've guessed it... the brainiacs decided to put this server closet right next to the elevator banks, and there were eletrical surges with the elevator activity during peak times. I don't know if they were pulling power from those circuits, or if it was some other technical thing above the comprehension of a sales guy, but as soon as they relocated the server closet, the problems went away.

[grayuk]

I am sure breather holes would help.
From what we have been told the rx generates quite a lot of heat on its own.
Normally this heat dissipates well as the ambient air is much lower in temperature. It does this through conduction.
As the ambient temp increases the temperature gradient between the RX and the surrounding air reduces, this means that the rate of heat dissipation reduces, so the rx gets hotter.
The rx will always be hotter than the surrounding air because it is a heat source. What changes is its ability to dissipate that heat into the surrounding environment which is now very hot and can only remove heat slowly from the rx.
If we can introduce a convection path (holes on the underside an don the top), the air can move through the case and take heat with it, dissipating the heat much more efficiently.

Your point on the server, seen similar things with soldering machines! These were putting massive spikes on the mains and screwing up computers!

[martin18152]

He took a RX, placed it on a piece of black paper on his driveway. He covered that with the glass lid from a cooking pot to simulate the canopy and to trap heat.

He could not get his RXs to show this behavior.



This is why the problem is more complicated than just the case temperature. As I stated before, electronic temperature profiles are complicated, and require engineering evaluation. The receiver may have to be under load, and under certain installation conditions etc…

I also don’t understand the Hitec Issue, if you read the directions that come with the Hitec programmer, it states that their digital servos operate on a control voltage from .8 to 5 volts , so what dose 2.7 v have to do with the problem. Looks like compatibility problem not defined.

I can say one thing; my first experience with futaba service was pretty good. I sent in a 3 year old 14mz radio with a failed trim switch, they fixed the switch, did a lot of other stuff, and as far as I can tell, no charge. I’m just waiting for the radio to be sent back.

[grayuk]

I am running a jet on 10 channels using a 14 channel rx.
A 12FG TX all servos are Hitec.
I have no issues, all work perfectly.

Paul

[gregorycstitt]

Maybe they should be handing out flack jackets and helmets now. It doesn't have to be a big show for someone to get hurt. My plane was taxing back rolling on its own when I lost signal. Thank God it was rolling slow or at least slow enough I could run up behind the plane and shut the ignition off. Remember guys, is doesn't have to be a TOC show for someone to get hurt. These radios and receivers are used by average fun flyers like myself everyday.

[grayuk]

Sorry to be a pain again but how many independent failures like this have been documented?
Are they all in the giant scale type?
Has any one reported a failure in a different type of aircraft?
Paul

[Judge]

	Quote: Originally Posted by grayuk
	Yes, I saw that one but, I do not know if the rest of the gear was in sun or not. If we assume it was not then maybe....there is a fault else where. But, what is not clear is if the rx, in his case was enclosed all around (as it would be on an installation) or if just sitting on the paper with glass on top. If that was the case then it is not a fair test of what is being described in the other failures. Air can move around too freely and remove heat.

Well, it is at least as fair as hitting it with a heat gun as another person did.

	Quote:
	I am not being negative here; I just want to be confident that this is a real problem.

As do I and I am waiting for Futaba to determine if it is indeed a problem or not.

But it amuses me to no end that the Internet mobs will take the word of people whom they have never met and know virtually nothing about over the word of the manufacturer. All this because they think Futaba is going to lie to them or whatever

[fastford]

	Quote: Originally Posted by martin18152
	I use to work in the military electronics business years ago, and there were all sorts of ESS programs to test thermal / vibration environments, these tests were done on 100% production units, at various sub assemblies. The trick was to pick test parameters that sufficiently stressed the component / assemblies, with out degrading its useful life. I doubt Futaba dose ESS on a 100% basis, you probably could not afford the product if they did. I would hope they do some, on a sampling plan, but who knows. I will bet they are probably doing a little right now. Some times big problems are connected to the simplest fix, that’s engineering, and I’m sure Futaba is working on it. Thermal profiles are very complicated, and I wouldn’t try to guess the problem. Simple thermal profiles show a linear decrease in temperature from the high T1 to low T2; however, the rate of heat transfer in nonlinear and very complicated. In this case you have a lot going on, radiation from the sun, radiating heat out of the receiver, internal generated heat by components, convective air over the case, and some heat generated convective air inside the case. You could eliminate the sun radiation by putting the receiver under some balsa or by using non insulating shield, that would eliminate one complication and would not hurt; however, heat transfer will stop once T1 = T2 regardless of the sun radiation, if T1 is your internal heat generator, it will continue to rise in temperature until T1 > T2 and energy will then continue to transfer from T1 to T2. Since the heat generated in the unit is fairly low in frequency, the rate of heat transfer out of the case by radiation is probably insignificant, where on the other hand the frequency of heat generated by the sun is very high, and the transfer rate is very significant into the unit – for this reason, it confuses me on why futaba makes their cases black, unless they plan on the units being in a dark place (classically that’s the way it use to be prior to the giant scale revolution with huge canapés) , then emissivity would dictate energy to flow out of the receiver by radiation. The amount of energy transfer is dependant on the geometry of the conducting / radiating surface. Energy can be transferred along board traces to the buss, and out through the servo control wiring. Once again the power box, or power distribution system would help, buy reducing the current through the receiver buss, therefore increasing the heat transfer. This is my opinion, and I plan on doing the following to make me feel better, since I have no direct knowledge of the problem, and I have not had any problem with my present system: Do not put the receive in direct sun light under the canapé, you can put it in the fuse, I doubt balsa and covering will block 2.5 GHz signals - maybe not the case with carbon fiber fuselage. Use some sort of power distribution system that reduces the load to the receiver buss If you have to put the receiver in sunlight, reflecting shield the receiver with a non insulating cover, that allows airflow over the receiver. Cover the canapé while it sits on the flight line, this should be done regardless of your receiver, I have seen canapés warp / melt on sunny hot days, so most people do this anyhow. Do a prolonged ground check prior to flying; chances are if heat is the problem, it will show up on the ground before you fly. I can say this will work with full canisters exposed to the inside of the fuse. Have Futaba hire more Mechanical engineers, thay are better a thermal dynamics than electrical engineers, lol, just kidding. If futaba has a design problem and it sounds like there me be some undefined issue, wait for futaba to better Idiot proof their system, and still do all of the above.

Mark I am impressed

[fastford]

edit

[freya1]

Judge, nobody is trying to discredit Futaba, we fly futaba since I can remember and will continue to fly Futaba because I am sure they will find a solution.
I know you weren" there and you can think whatever you wan't, but I saw it happen as did a few more people at the field, and as you can read it has happenned to people in other states as well.
My equipment has worked with out issues even on the same day it happenned to my friend, but should I push my luck untill we know exactly what is going on? I think not! I like to bring my kids to the flying field and so do my friends and I am not risking their lives because you think we are lying, Maybe Futaba had a bad batch of receivers and only those will be affected, but somebody needs to do some testing or investigating instead of saying we are lyers because you don"t know who we are.
We ara not trying to create a panic or bash the product, we just want to bring the issue out so it can be fixed before somebody gets hurt.
Thank you