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HelicopterBergen R/C Helicopters › Assitance needed : RF interference on EB gasser
10-03-2005 04:08 PM  12 years agoPost 1
jdewer

rrNovice

Belgium

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Ladies & Gentlemen,

I definitely need your ideas.

Situation :
Last Saturday I reworked the tail of my EB, due to a difference in play between the two bladeholders and to get rid of an annoying play in the TR-transmission. While having the tools out, I added a good voltmeter to indicate battery state. Another thing I did was leave the RDS or how it's called (the cable to make a direct connection between the transmitter and the receiver without emitting anything over RF ) connected to the receiver. I thought it was a good idea , so that I could hook the heli up to the transmitter whenever I wanted.

After that I tried a small test-flight in the backyard. While spooling up, the receiver switched constantly to failsafe mode ( Futaba R149DP). A primary sign of severe interference, or so I thought.
I thought of the RDS cable behaving like an antenna. So I removed that cable and retested the heli : same thing. Failsafe modus when spooling up.
So I removed the new battery indicator and replaced it with the old one.
Same behaviour.
Next possibility : battery pack low. Battery charge indicator showed no problem, but I thought that it might be a good idea to have the packs fully loaded for Sunday morning (my weekly trip to the field ).

Sunday morning I had the same behaviour as the evening before : failsafe modus when spooling up the engine.

I thought of the spark plug connector, with a possible faulty ignition. Cleaned the spark plug connector and made sure it made a good contact. No avail.

I did a radio reception test with engine off : over a mile without a glitch. (mobile phones are great for this, aren't they :-) )

I didn't dare to do a reception test with engine running : the behaviour occurs only (or is more obvious) near to take-off condition (engine in powerband and collective-stick halfway ).

Sunday evening I verified all the servo leads, the power switch, the battery leads, the antenna connector on the receiver, in a word : all the electrics. Nothing that might explain the behaviour.

So : the big question : who has an idea what's going on ?

Kind regards,

Jan Dewerchin.

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10-03-2005 04:16 PM  12 years agoPost 2
jdewer

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Belgium

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I just read another post about interference coming from a lose boom support. Something to check this evening. Might just be the answer....

Anyway, your input is still most welcome.

Jan Dewerchin

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10-03-2005 05:57 PM  12 years agoPost 3
rckrzy1

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Hurst Texas

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My "weird" rfi problems have allmost allways been a cracked metal frame part. Look for the tell tale gray colored debris.



Wildcat Fuels

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10-03-2005 07:10 PM  12 years agoPost 4
Chris Bergen

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cassopolis, MI USA

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Since the frames are G10, I doubt that a crack will cause RF

Check the drive train, by that I mean the engine obviously, the clutch system, clutch bell and pinion, and triple bearing block. These are all the things turning when the engine is running. This may require pulling the engine completely out of the heli to inspect all bolts and bearings.

Are you using a base loaded antenna? If not, is your antenna wire anywhere near the ignition system of the engine?

Chris D. Bergen

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10-03-2005 08:48 PM  12 years agoPost 5
jdewer

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Belgium

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Chris,

I don't have a base loaded antenna. My antenna wire runs on the lower left side through a thin plastic tube, not particularly close to the ignition or anything.

The strangest thing is that this just started overnight, not like a condition that worsens or anything.

I'm a little reluctant to pull the engine. Oh well, that gives me the opportunity to recheck on the alignment and all the bearing, like you said.

I hope I can find the cause of this real soon, the days are getting shorter, and I don't get to fly too often lately...

Kind regards,

Jan Dewerchin.

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10-04-2005 03:32 AM  12 years agoPost 6
Chris Bergen

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cassopolis, MI USA

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Are you sure it is going into failsafe, and not maybe your throttle servo dying??

Are you running PCM or PPM?

Chris D. Bergen

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10-04-2005 07:34 PM  12 years agoPost 7
AutoMike

rrNovice

Seymour In.

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Just saw the same thing in a friends heli.He had just about gotten to the point of pulling his hair out when he found the switch harness was bad, making intermittent contact at rpm but idle or engine off testing showed no problem.

Dang!! Thats going to leave a mark....

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10-04-2005 07:53 PM  12 years agoPost 8
jdewer

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Belgium

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Chris,

I can tell that it's failsafe mode because the collective switches to about 0° pitch, notable when you start to reach the hoovering point at about 5° pitch.

AutoMike,

Hmmmmm... Good one. I sure hope it's as simple as that. But how come the swashplates drops to about 0° degrees pitch when it happens? I thought that under that circumstances, the pitch would remain at about 5° ?

Doesn't it take effort from the servos to pull the blades back to 0° ? With no juice, hard to accomplice, no ?

Anyway, thanks for the input, I got something to chew on for this evening.

Kind Regards,

Jan Dewerchin

oemèr, oeliver ! :-) Old flemish proverb.

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10-04-2005 08:02 PM  12 years agoPost 9
jdewer

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Belgium

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Chris,

I forgot to mention : I fly PCM.

oemèr, oeliver ! :-) Old flemish proverb.

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10-04-2005 08:58 PM  12 years agoPost 10
crowfly

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Pleasant View, TN​U.S.A.

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There is a huge difference between losing the battery current to the receiver & servos,,,, and losing the radio signal to the receiver & going into "failsafe".
I can tell that it's failsafe mode because the collective switches to about 0° pitch
Actually this tells me it is not going into failsafe unless 0° pitch is where you have programmed it to go to in fail safe. If you program the collective servo to hold the last command, it will do just that so long as there is battery voltage going to the receiver and servos. If you lost battery current all the electrical components would be dead. All servos with no load on them would hold their position and all servos with a load would attempt to rotate to a point of no load. A sure fire way to tell if your going into failsafe is to program the throttle to go to idle. Unless you have a very strong throttle return spring (if you do, unhook it). Now, with the throttle programmed to return to idle and the pitch programmed to "hold",,,,,,,, when the problem occurs, if the pitch flattens out and the throttle doesn't return to idle, you are not entering failsafe mode, you are most likely loosing operating current.

If God had meant for man to fly, he would have given him more money

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10-05-2005 09:10 AM  12 years agoPost 11
jdewer

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Belgium

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Crowfly,

Thanks for your advice. I checked the power switch yesterday evening and indeed, it wasn't in a good condition. Actually, it surprised me that any current got through at all. So the receiver definitely didn't switch to failsafe mode as I thought first.

I think I'm going to adapt the solution a buddy of mine uses : gold plated 'banana' connectors from the battery, going into two separate connectors in the receiver, leaving out the possibility of a unreliable switch, and getting more current in for those power hungry digital servos.

Thanks all for your input and advice, time to correct the situation and go burn some fuel !


Kind Regards,
Jan Dewerchin

oemèr, oeliver ! :-) Old flemish proverb.

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10-05-2005 02:32 PM  12 years agoPost 12
Chris Bergen

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cassopolis, MI USA

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Good job, Crowfly!!

Chris D. Bergen

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10-05-2005 02:44 PM  12 years agoPost 13
Gary Travis

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Utah

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Exellent!! glad the problem has been found. I just noticed this post as I have been away from the computer getting ready for a road trip. At the Ircha SW FF Tristan had the same problem, we replaced the switch and away he went.
Gary

Bergen R/C Helicopters Duralite Batteries DJI Innovations Magnum Fuels Wren Turbinesl

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10-13-2005 06:40 AM  12 years agoPost 14
jdewer

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Belgium

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Guess what ? It's back...

Here we are, almost two weeks later.

The faulty power switch is gone, replaced by a temporary arrangement until I get the banana - contacts.

Last Sunday at the field, I was all to happy to start flying again. The engine was a little hard to start, I let it purr a little to warm up a bit. And then I started to spool up.

As soon as the head was almost at speed, I had no control anymore. As I was trying to get as close as I deared to get to shut the engine down, the swashplate gave two violent jerks backwards. Very disturbing when you are that close.

Being that close, I saw the battery indicator very clearly and it got current : it showed full batteries. Then all of a sudden I got controls back for a fraction of a second, enough to let the engine servo cut the throttle. Once the engine stopped, I regained full control immediately.

Two possibilities : The spark plug wire a bit loose & bad servos.

Together with the other gas pilots at the field, we verified the state of the batteries, checked for loose connections, and tried to test the state of the servos. When checking the spark plug wire, the contact looked ok, but we can't tell for sure.

So it's all back to where I started a couple of weeks ago.

Any ideas ?

Jan Dewerchin

oemèr, oeliver ! :-) Old flemish proverb.

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10-13-2005 12:27 PM  12 years agoPost 15
Malorie

rrElite Veteran

Paw squared, MI

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Sorry if this ground has been gone over before. Have you tried a different reciever?

Malorie

Life's a journey, NOT a destination.

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10-13-2005 02:05 PM  12 years agoPost 16
Chris Bergen

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cassopolis, MI USA

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Before you do anymore testing, set the failsafe to go to idle or stop on the throttle in the radio.

Change spark plug.

Get the antenna as far away from the ignition as possible.

If you have some sort of shielding on the spark plug wire, make sure it's properly grounded, or remove it all together.

Check the bearings in the drive train, cluchbell triple, bearing block.

Check the clearance of the pickup coil next to the magneto. I typically use 2 business cards. I have seen where the coil slipped and was rubbing on the magneto.

Is there any other history of this helicopter we should know about (crashes, etc).

Chris D. Bergen

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10-13-2005 02:44 PM  12 years agoPost 17
v22chap

rrKey Veteran

Granger, Indiana

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Jan

Are you running the stock RX wire or a base loaded antenna ?? This will make a difference on this problem ,,if it hasn't been brought up before.

Larry C ----------Bergen R/C helicopters

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10-13-2005 06:04 PM  12 years agoPost 18
Chris Bergen

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cassopolis, MI USA

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He does have the wire and it was suggested to run base loaded.

This may or may not be the problem, however we wont know until it is changed and that solution is eliminated.

Chris D. Bergen

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10-22-2005 07:39 PM  12 years agoPost 19
jdewer

rrNovice

Belgium

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Sorry, I was not able to post any news recently.

The problem is solved, finally !!!!

You'll never guess what the actual problem was, so I 'll tell you right away :

The tail pushrod rubbing against the tail boom support struts.
Carbon rubbing against carbon = RF interference.

It started when I was working on the tail (first post). Apparently, I didn't align the horizontal fin support like it should have been, so the tail pushrod could rub against the tail boom support struts. Add a light vibration on the pushrod with the engine in the powerband and bingo ! RF interference.

I had a "light bulb experience" last sunday at the field : a fellow heliman had a power extention to his fieldkit, made from two jump-start cables and a carbon plate (to keep the two poles apart - so he told me ! ). I told him he was in for some fun, should he connect that to his car battery. He didn't believe me , connected the jump-start cables to his battery and picked up the carbon plates with his bare hands to show me how well it isolated. Five seconds later, the carbon (or his burnt fingers) started to smell badly and got very hot. I think I saved his car battery by quickly disconnecting one of the start cables and told the man to use plywood instead.

The incident got me thinking on the conductive capacities of carbon and that I had to check all carbon components for rubbing or crack marks or anything on the Intrepid EB. Within two minutes, I found the real cause for the RF-trouble. Not that hard, it were the only carbon parts that close together in the EB....

Have a nice weekend, everyone !

oemèr, oeliver ! :-) Old flemish proverb.

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10-25-2005 04:17 PM  12 years agoPost 20
Chris Bergen

rrElite Veteran

cassopolis, MI USA

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The boom supports are aluminum, unless replaced with an aftermarket item, and yes, this can still cause interference.

Glad to see you found it!!

Now get a base loaded antenna on there!!

Chris D. Bergen

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HelicopterBergen R/C Helicopters › Assitance needed : RF interference on EB gasser
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