Winco Steve Posted December 7, 2012 Share Posted December 7, 2012 Hi all, I have now, officialy, run out of ideas! I have tried every trick known to me (and some not known to me) inorder to solve the throtle servo being under constant load (buzzing). It is a standard SRM 102 (sanwa). I have changed the servo, used every method I know to link it to the motor (wire, rods, plastic snake etc.) and various types of link connections (Z bends and all). I have re -sited the servo from its designed position and raised and lowered it. Different control horns/wheels also. The receiver battery is fully charged. The engine is an Irvine 53. Does anyone have a panacea for my ills? Is there a trick I have missed over the years? Normaly I can resolve this problem but this is just beyond me this time! I sit, scratch and hope! Regards, Winco Steve Edited By Winco Steve on 07/12/2012 14:26:07 Quote Link to comment Share on other sites More sharing options...
ken anderson. Posted December 7, 2012 Share Posted December 7, 2012 hello steve..could be that the servo has had it......disconect the control horn and is it still buzzing-if so i would say that its on its way.....i had a look and new they are a tenner.......so get it on your list off santa(her indoors) .... ken anderson .....ne..1 her indoors/santa dept. Edited By ken anderson. on 07/12/2012 14:35:49 Quote Link to comment Share on other sites More sharing options...
Winco Steve Posted December 7, 2012 Author Share Posted December 7, 2012 Hi Ken, Tried exchange of servos, tried three all do the same. When control horn disconnected then load off/buzz stops. So I'm quite happy that the servos(s) are not the problem. Oh, I need loads more from Santa that she has no idea about yet! All the best, Winco Steve Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted December 7, 2012 Share Posted December 7, 2012 Steve, would it be possible to get some pictures of the installation loaded up? An analogue servo will only buzz as a rule if it's under load. My diagnostics: Is the pushrod lined up with the arm at both the servo and the throttle? If not reroute it so that it is. Is it easy to move when disconnected from the servo? If it is, then maybe it's the nature of the servo. A lot of digitals are noisy, that's just the way they are. If the pushrod feels the least bit stiff when disconnected from the servo, is it easy to move if disconnected from the throttle? If it is then you've got a sticky throttle, if it isn't then your pushrod needs some attention. Edited By Bob Cotsford on 07/12/2012 15:07:30 Quote Link to comment Share on other sites More sharing options...
Greybeard Posted December 7, 2012 Share Posted December 7, 2012 One other point. Does it buzz at any position or just at the ends of travel? Quote Link to comment Share on other sites More sharing options...
John Cole Posted December 7, 2012 Share Posted December 7, 2012 It doesn't buzz if you remove the servo arm, but does it buzz if you replace that but disconnect the linkage at the throttle arm? Quote Link to comment Share on other sites More sharing options...
Winco Steve Posted December 7, 2012 Author Share Posted December 7, 2012 Hi all, Several points there. O.K. The link between the servo and the motor is now a plastic snake type. This seems to be the best option in my case. The 'buzz' is at all points not just at the end points. The snake is almost straight to motor. The 'buzz' is no longer evident when either the motor link OR control horn ends are disconnected. It is only when both ends are connected to motor and servo that buzz starts. Push rod is free and easy when disconnected. Easy to move, by hand, when connected to only the motor (no obstructions or friction). Throtle barrel opens and closes smoothly. When at full open or full closed (carb) a slight +/- on end stop will TEMPORARILY stop the buzz. When moved from this position it starts again. I will try my photographic skills out and put the results on line if I can work out how to do it! Thanks all, we may get there yet! As I say, I have tried everything I know but the solution evades me. Regards, Winco Steve Edited By Winco Steve on 07/12/2012 15:52:17 Quote Link to comment Share on other sites More sharing options...
Winco Steve Posted December 7, 2012 Author Share Posted December 7, 2012 Hi again! Just tried another test by 'temporarily' legthening the throtle arm. No difference..but when I put it back to original I found that the buzz can be eliminated by the following. When moving from full closed to quarter (for example) on the throtle stick and then stop stick movement at this position the buzz is present. But slightly, very slightly, easing stick back will stop the load/buzz. This works throught the stick range and in both directions. Any ideas? Winco Steve Edited By Winco Steve on 07/12/2012 16:28:10 Quote Link to comment Share on other sites More sharing options...
John Cole Posted December 7, 2012 Share Posted December 7, 2012 It could be simply that the potentiometer on the servo has got a bit worn / dirty. It's also possible that the jitter comes from the Tx. Try this: Disconnect the linkage and then move the servo lead onto a switched channel (5 or 6?). Then move the switch from one position to the other a large number of times, letting the servo make a full travel before revering the switch. That might clean up the pot. Reconnect the linkage. Move the servo lead onto e.g. the elevator channel and see if the buzz is still there. If not, try it on the throttle channel. still buzzing? Try a different servo to control the throttle. Quote Link to comment Share on other sites More sharing options...
Phill @ Elite Workwear UK Posted December 7, 2012 Share Posted December 7, 2012 Blah - I had just typed almost exactly what John said. I have finger ache now! I had a receiver that was causing all sorts of odd servo behaviour a couple of weeks ago. Can you temporarily change the receiver totally?.. is it 2.4 or 35mHZ?.. Phill Quote Link to comment Share on other sites More sharing options...
CARPERFECT Posted December 7, 2012 Share Posted December 7, 2012 One way to check the RX is Temp change wich channel you use for throttle with any of the others and see if it buzzes Quote Link to comment Share on other sites More sharing options...
John Tee Posted December 7, 2012 Share Posted December 7, 2012 If it didn't buzz mid range I would suggest altering the servo travel on the tx (if computerised) but if buzzing mid range would suggest a binding throttle push rod/cable. John Quote Link to comment Share on other sites More sharing options...
Winco Steve Posted December 7, 2012 Author Share Posted December 7, 2012 Hi Guys, Good ideas! I will try a different receiver altogether to see what transpires. Never thought of that, just goes to show if you don't ask....! The buzz (we shall call it) is across the whole range of travel. By the way, the servo is a never used new one so should be O.K. Can still try another again! I have experimented with the settings (adjusting EPA's to different % etc ) in the TX (Sanwa 6000) but no joy. The RX is a Sanwa 35MHZ but I also have a new Futaba 6J (2.4 GHZ) with an R2006GS receiver so I will give that a go as well if problem still persists on 34MHZ. So will try....different 35MHZ receiver and 2.4GHZ TX/RX. I will return with results tomorrow! Thanks to all, Winco Steve Quote Link to comment Share on other sites More sharing options...
Ian Jones Posted December 7, 2012 Share Posted December 7, 2012 Does the throttle arm on the carb moves freely? Opps sorry Bob has already said that. Edited By Ian Jones on 07/12/2012 18:23:22 Quote Link to comment Share on other sites More sharing options...
Winco Steve Posted December 7, 2012 Author Share Posted December 7, 2012 Hi Ian, Yes, already covered but grateful for your input. Cheers, Winco Steve Quote Link to comment Share on other sites More sharing options...
Allan Bennett Posted December 7, 2012 Share Posted December 7, 2012 I've sometimes had throttle servos that buzzed slightly, but could be quietened by slightly easing the throttle stick the opposite way. It can be caused by inperceptible friction in the link and/or the carburettor throttle movement, but I'm convinced it goes away altogether when the engine's running, because the vibration helps overcome any sticktion in the linkage (or maybe because I can't hear it over the engine noise). But whatever, it's never caused me any problem in flight, and I've never had a throttle servo fail on me in 25 years' of flying. Quote Link to comment Share on other sites More sharing options...
the unmagnificent man Posted December 7, 2012 Share Posted December 7, 2012 Hi Steve, I had the same problem a few weeks ago on a flap linkage (see VQ Hurricane) Just some things to try (you never know!) How tight is the servo screwed in? Check that the servo screws are not holding the servo to tightly. make sure that the servo is able to flex slightly on its rubbers. temporarily remove two of the screws (keep 2 opposite corners) and slightly back off the other two. This will mean that the servo is actually loose and therefore can't be forcing against the push pull rod unless the pushrod is even slightly too tight. is the servo pushed into a tight servo try and not allowing any flex? I ask these questions because after reading all the above i thought if the servo was not screwed in at all (just connected to the throttle linkage) then any force back to the servo would just turn the servo. Normally the twist would be taken up by the rubbers. However if the servo was held too tightly bzzzzz. Just a thought. good luck. UMM Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted December 7, 2012 Share Posted December 7, 2012 Have you got a different make or model of servo that you could try? It might just be that the model of servo you are using has an extremely tight deadband and low torque. The slightest load would stop it getting to exactly where it wants to be, hence it buzzes away trying for that last fraction of a degree of movement. Backing off the throttle fractionaly then puts it where it's happy. Quote Link to comment Share on other sites More sharing options...
Former Member Posted December 8, 2012 Share Posted December 8, 2012 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Winco Steve Posted December 8, 2012 Author Share Posted December 8, 2012 Hi all, Thanks for all the replies. There are a few there that I have never considered so thank you very much. So, I returned armed with all my new knowledge to sort this out once and for all! I changed the receiver, problem persisted. Changed to 2.4 no difference. Getting a bit cross now! What have I NOT changed? The motor. Anything worth a try now! Changed motor to an old Super Tiger and linked it up. Problem solved!!! So I triple checked the freedom of movement on the Irvine carb and it seemed smooth enough to me. It has never been a problem in the past. I then very, very, very slowly moved the carb open and shut and noticed a slight 'catching' in movement. This was not apparent when moving the barel at a 'normal' pace. O.K. strip down carb, clean, deburr (?) lubricate....still the problem. I then noticed that removal of the barel retaining screw elliminated the 'catch'. Cleaned the screw and no better. Replaced the screw with a spare...no better. I'm now thinking a new carb is the solution as it is impossible to do much more with it. Anyone got one !!! I replaced the Tiger motor and problem gone. So, not the linkages, servos but a carb problem so slight that it has this undesirable effect. Thanks to everyone and I hope my little experience has also benefited some! it's turned my already grey hair white! Best wishes, Winco Steve Edited By Winco Steve on 08/12/2012 09:58:13 Quote Link to comment Share on other sites More sharing options...
FlyinBrian Posted December 8, 2012 Share Posted December 8, 2012 Check the helical slot that the screw slides in, there must be scratch or something in the slot which you can probably remove with fine emery paper. Quote Link to comment Share on other sites More sharing options...
Winco Steve Posted December 8, 2012 Author Share Posted December 8, 2012 Hi mate, Yes, tried that with very fine wet & dry and a very fine watch makers file. No joy I'm afraid. However, I will have another try and hope I don't over do it! Regards, Winco Steve Quote Link to comment Share on other sites More sharing options...
Solly Posted December 8, 2012 Share Posted December 8, 2012 If I were you I'd just let it buzz mate. Quote Link to comment Share on other sites More sharing options...
Winco Steve Posted December 8, 2012 Author Share Posted December 8, 2012 Hi, That certainly is an option! However the challenge was set! I have now solved it! I decided to **** or bust so I completely stripped the carb down and then removed the brass fuel inlet cone (which is the only piece not threaded and probably not supposed to be removed!). I was then able to use a very fine Dremel bronze brush to completely clean the whole interior of the carb barel housing. Plenty of 3 in 1 and put it all back together. Cleaned the helical slot too and buzz gone!! At last. It appears that, after all, it was a sticky barel which only stuck when it felt like it! There must have been some kind of debris in there that caused a burr which I eventualy removed as stated. Thanks to all for your help. I think a got a bit obsesive! Regards, Winco Steve Edited By Winco Steve on 08/12/2012 13:22:06 Quote Link to comment Share on other sites More sharing options...
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