Mathew Brooks Posted July 13, 2013 Share Posted July 13, 2013 hi guys, i am having a few difficulties with my ripmax .40 trainer. i have all futaba radio gear and is 35mhz. i am getting a lot of interfierance whilst in flight i think as the motor is throttling very irratic whilst im not even touching the remote. i would like to change it to 2.4ghz stuff so as not to get any interfierance and crash.....again. i have heard of 'dogy crystals', im not sure what this means but could be a factor in my problem... i will put up some technical info of what gear im using in a bit as not got aircraft to hand, just some initial thoughts would be a good start.. Quote Link to comment Share on other sites More sharing options...
simon barr Posted July 13, 2013 Share Posted July 13, 2013 Hello Mathew.Sounds like you may have metal-to-metal "noise". Have you got a metal clevis on your metal throttle arm?, and if so, is it loose? Or are the wheels rattling? Changing to 2.4ghz will certainly help, but worth checking everything anyway as "good practice". Doubt if it is the crystals as they usually work or they don't... Its dead easy to change to 2.4, just buy a Tx/Rx combo and plug your servos in... Quote Link to comment Share on other sites More sharing options...
stevejet66 Posted July 13, 2013 Share Posted July 13, 2013 I had this problem as i use both 35mhz and 2.4ghz, I changed my 35mhz crystals to a different channel and all the twitching stopped. Quote Link to comment Share on other sites More sharing options...
Phil Green Posted July 13, 2013 Share Posted July 13, 2013 Hi Matt, theres nothing fundamentally wrong with 35mhz and we should all continue to make use of it if we are not to have it taken away from us. Futaba 35mhz gear is as reliable as any, its probably one of the best, but you may have a specific problem that forums are generally very good at fixing. I'd do at least a little investigation into this problem before jumping ship. Do you notice it only on the throttle channel? there are many reasons for an engine to wander in rpm, such as fuelling, fuel state, air leaks, adjustment, temperature, back-pressure, glowplug ... if only the rpm is affected it might not be interference at all. If the throtttle servo is definitely doing its own thing, have you tried this servo on a servo tester, and have you tried a different servo in its place? if you're sure it is definitely interference, do other club members suffer, is it at one particular location on the field, if you leave the tx on the flight line do you get intereference when walking the model through this location? does the gear range-check ok? Does the interference affect your other models? do you see any visible signs of a possible RF field (CB or ham aerials on nearby houses etc)? batteries all ok under load? maybe the throttle servo is stalling at extremes of travel? Lots of possibilities, let us know what you think. Cheers Phil Edited By Phil Green on 13/07/2013 18:42:32 Quote Link to comment Share on other sites More sharing options...
crispin church Posted July 13, 2013 Share Posted July 13, 2013 to answer your question about changing to 2.4 no its not hard you take out the 35 meg rx and replace it with a 2.4 but make sure your pluging right servo lead into right plug they not all follow futaba and of coarse you will need the same brand of tx 2.4 is not like 35 any make works there many brands to pick from spektrum and futaba is very common is most shops there are orange and lemon that make rx that works with other but make sure it say its for your tx but look and fix your problem Quote Link to comment Share on other sites More sharing options...
Phil Green Posted July 13, 2013 Share Posted July 13, 2013 ... but if you dont try to find a reason, you could end up simply transferring the problem to your new 2.4 gear... Quote Link to comment Share on other sites More sharing options...
Rick Tee Posted July 14, 2013 Share Posted July 14, 2013 As Simon says check for any metal to metal, if your push rods are metal or CF all the way make sure they can't touch. Use a scanner to check the channel you are using is clear. If the RX aireal is inside the model put it outside, exit the model as close as is practical to the RX, do an engine/motor running range test (TX aireal down) and try another servo on the throttle. If that fails to solve the problem change the xtals. Edited By Rick Tee on 14/07/2013 07:03:30 Quote Link to comment Share on other sites More sharing options...
Dave Bran Posted July 14, 2013 Share Posted July 14, 2013 In addition to the various suggestions above, the potentiometer on the throttle inside the Transmitter might also be a cause when the carbon track gets dirty. Have had this from time to time with Futaba Tx's, and a quick spray into the pot of a contact cleaner that is a total evaporation type and work the stick to ends of travel a few times usually cures it. However, making changes before you fully investigate is NOT a good idea, you can introduce more than you cure I suggest you make no changes until you have tethered the plane securely, run the engine keeping well away from and behind the propellor, and do a range check with the aerial partially down with someone who knows what to look for watching the plane carefully. Find out for sure if it occurs ONLY to throttle or not. Then return here if nobody to help you. Quote Link to comment Share on other sites More sharing options...
Allan Bennett Posted July 14, 2013 Share Posted July 14, 2013 Just to leave no stone unturned, have you looked/listened to see if the throttle servo is jittering, or if the engine is fluctuating without the servo moving? The engine could be "erratic" if air is getting in somewhere, for instance; or even if it's not tuned correctly. If you've determined that it's the throttle servo that's jittering, and causing the engine fluctuation, try plugging a different servo (any one) into the throttle channel to see if it is quiet. That could maybe reveal a dodgy throttle servo. A dodgy crystal would probably cause all servos to be erratic or, more likely, to not work at all. What age is your Futaba gear? If it's not ancient, your symptoms are not sufficient to necessitate an upgrade to 2.4GHz -- though they may be an excuse if you want to change Quote Link to comment Share on other sites More sharing options...
Mathew Brooks Posted July 14, 2013 Author Share Posted July 14, 2013 thank you for the comments guys, i will look deeper into the problem today and see if i can find the source Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted July 14, 2013 Share Posted July 14, 2013 Just an obvious question - this is an IC powered model? Or is it electric power? BEB Quote Link to comment Share on other sites More sharing options...
Mathew Brooks Posted July 14, 2013 Author Share Posted July 14, 2013 Ah it is an IC powerd model and i am now aware i have posted in the wrong section....can it be moved? Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted July 14, 2013 Share Posted July 14, 2013 Not a problem Mathew - as you can see I've moved it! The real reason for asking was with it originally being in the electric flight section and you refering to "motor" in the OP, I wondered if what you were getting was just good old "glitching" which electric models can suffer from on 35MHz. BEB Quote Link to comment Share on other sites More sharing options...
Mathew Brooks Posted July 17, 2013 Author Share Posted July 17, 2013 right guys, i have have had a good look over the model over the last couple of days and i did find a loose front wheel and a slightly loose engine so i tightened everything up. i also saw that a couple of the servos were slightly rusty (bought the plane second hand) so i took it out and tried to fly it again. it took off perfect with no twitching and flew lovely, i then did a circuit and came in for a touch and go landing. this is when the prblems started, the engine revver up for a few seconds and made it too quick for a landing so i pulled up again and went around for another circuit. as i turned in for a final aproach the plane went mad again and revved up and the wings dipped to a point where i just had to level it up before crashing. luckily i was in a farmers field with a crop so very light damage, but what i did find was that the grub scre that holds in the internals to the carb on the engine was missing letting them almost pull out like a kind of barrel. it may have been this causing the revving of the engine if i had only just noticed it? Quote Link to comment Share on other sites More sharing options...
Allan Bennett Posted July 17, 2013 Share Posted July 17, 2013 Yes, the missing screw (or perhaps it was loose, and finally went missing during the flight) could most certainly have caused erratic engine running, either by letting the thottle setting change, or by letting air in when it's not needed. Quote Link to comment Share on other sites More sharing options...
Mathew Brooks Posted July 18, 2013 Author Share Posted July 18, 2013 This is my connecting rod to the carb. I don't really understand when you say metal to metal. I'm assuming its the metal rod to metal arm? http://i18.photobucket.com/albums/b127/mango_maty/null-4.jpg Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted July 18, 2013 Share Posted July 18, 2013 Mathew, if you read this you will find out how to insert your photograph into your post. People are far more likley to look at it and advise you if they don't have to go off onto another website to see the picture. BEB Quote Link to comment Share on other sites More sharing options...
Mathew Brooks Posted July 18, 2013 Author Share Posted July 18, 2013 Quote Link to comment Share on other sites More sharing options...
Mathew Brooks Posted July 18, 2013 Author Share Posted July 18, 2013 thank you BEB. tried it the photobucket but it didnt work. Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted July 18, 2013 Share Posted July 18, 2013 A-Ha! That throttle arm on the carb - its metal - right? And that rod it metal too. That carb arm will vibrate like mad. The two metals will rub together and you'll get a shed load of radio interference! That's what the guys mean by "metal to metal contact". How to fix it? Two ways: First, instead of using a metal rod with a Z bend in it, use a threaded end rod with a plastic clevis. Second, alternative way, replace the metal arm on the carb with a plastic one. Either way - don't leave that metal to metal vibrating contact - you'll never get a clean radio link with that there. BEB Quote Link to comment Share on other sites More sharing options...
PatMc Posted July 18, 2013 Share Posted July 18, 2013 IMO metal - metal noise is a mythological problem. I used to be very careful to avoid metal - metal contact, believing at the time the perceived wisdom. Then I wondered about all the unavoidable metal to metal contact that goes on in an engine. That was back in the good old days of 27 MHz AM sets. Since then I've invited anyone who's claimed to have experienced it to demonstrate the problem - no one has. I dare say there will be somebody reading this who will have experienced metal - metal interference - the invitation remains open. I suspect that as in this thread the problem witnessed will have some other cause. Quote Link to comment Share on other sites More sharing options...
jeff2wings Posted July 18, 2013 Share Posted July 18, 2013 If you have metal rattling in your engine ,you need a new one ! Quote Link to comment Share on other sites More sharing options...
PatMc Posted July 18, 2013 Share Posted July 18, 2013 Anyone mention metal "rattling" ? Quote Link to comment Share on other sites More sharing options...
Erfolg Posted July 18, 2013 Share Posted July 18, 2013 Patmac I think I know where you are coming from. For me there has been much I have not really believed. Then evidence has indicated that it could be. There are other things which I have believed, with most other people. Other things I have thought were true and others believe to be true, have turned out to be not correct. Typical what I just take for granted that Pi is 3,142, which is reasonably true. But can you prove it? I have also believed that most heat loss from a body is from your head. Which is not really true. It is only true when you are wearing cloths and your head is exposed. So we come to metal on metal. Is it true. It is the sort of thing which you can easily imagine has been researched. I can also tend to believe that most accept the existence of the phenomena to be true, is based on there being no contradicting evidence, known to us the public. If it does exist I can imagine it will not be straight forward. Does it matter if the materials are magnetic. What determines what frequencies are generated, at what strength, Does humidity matter and so? The fact that most of us do not experience the problem, it seems that it must be highly specific. So if changing to a plastic clevis does the job, great. Yet if it did not I would not be surprised. From my own experiences, issues like this often revolve around faulty electronics or something else we have wrong. I have often been embarrassed by my own stupidity, rather than the problem being something esoteric. Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted July 18, 2013 Share Posted July 18, 2013 Pat -I too was a sceptic about this, but the debate in this thread - which at least proposed a credable mechanism - lowered my sceptism considerably! Makes interesting reading! BEB Edited By Biggles' Elder Brother - Moderator on 18/07/2013 22:22:17 Quote Link to comment Share on other sites More sharing options...
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