Chris Procter Posted February 5, 2012 Share Posted February 5, 2012 Hi, all Just adjusting the end points on my new Irvine tutors servo's and have a very annoying problem with a couple of them. All servos set up at mid-points then use T7C box to adjust servo end points, which is set according to the Irvine control surface deflection setting. all ok until a final check then 2 of the servos buzz at the end points of travel, so go back into Tx menu and knock off another percentage point each way........buzz stops for a few throws and then returns ?? I've adjusted them up and down god knows how many times but still get the buzz at the end points and they're not powering off ?? Is this normal/acceptable ? happens on Aileron and rudder/Nosewheel servo's but not elevator or throttle. Hope the above makes sense Thanks Chris Quote Link to comment Share on other sites More sharing options...
Alan Cantwell Posted February 5, 2012 Share Posted February 5, 2012 remove the link to the servo, when you move the control surface to the same deflection as the servo travels, does the movement tighten up? might be a benefit to make a simple card template to make sure the angle you manualy push it to is the same Quote Link to comment Share on other sites More sharing options...
Chris Procter Posted February 5, 2012 Author Share Posted February 5, 2012 Thanks Alan, checked the movement without servos connected, no resistance felt and the travel required is very limited according to the Irvine instructions. Aileron 6mm up and down Elevator 10mm up and down Rudder 15mm left and right Free surface movement at least double the above on all surfaces so they shouldn't struggle. when setting servo end point travel to the above travels they're ok, come out of EPA adjustment mode and do a control check and the buzz is back with full stick deflection ?? Many thanks Chris Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted February 5, 2012 Share Posted February 5, 2012 What are the servo's Chris? Sometimes digitals "hunt" a bit at the end of travel. BEB Quote Link to comment Share on other sites More sharing options...
John Privett Posted February 6, 2012 Share Posted February 6, 2012 Chris, have you setup the linkages so that the control surface deflections are approximately correct with the standard end-point adjustments? The end-point adjustment on the transmitter should just be "fine tuning". What are the end-point percentage figures for the two servos that are giving the problem? Quote Link to comment Share on other sites More sharing options...
Chris Procter Posted February 6, 2012 Author Share Posted February 6, 2012 BEB, the servos are Futaba S3003 's that came with the Fieldforce 7 2.4g set. John,(I hope I understand what you're asking) the standard EPA (100%) deflects the controls way too much for the irvine settings, so I went into EPA mode and wound them back to deflect the surfaces to those values. The servos now have : Channel 1 ------- 73% Left, 73% Right (Aileron)--------------- Buzz at end points Channel 2 ------- 66% up, 66% Down (Elevator)---------------No Buzz at end points Channel 3 ------- 112% Forward, 123% Back (throttle)------- No buzz at end points Channel 4 ------- 70% Left, 70% Right (rudder/ NWS)---------------- Buzz at end points Hope that helps I'm beginning to think there may be enough friction in the cheap plastic rod keepers to cause this when at an angle, as the servos don't do this when rods disconnected and the rods on their own move freely enough ?? Is this common ?? Many thanks for the replies, i'm sure we'll get to the bottom of this. Chris Quote Link to comment Share on other sites More sharing options...
Allan Bennett Posted February 6, 2012 Share Posted February 6, 2012 Yes, I was just about to chip in and suggest friction in the linkages and/or hinges. My experience is that a small amount of buzz is quite normal (provided the servos don't buzz when the linkages are disconnected), and can usually be stopped my moving the control stick ever so slightly. Also, I would not rely on end point adjustment to get your deflections right: Much better to adjust the linkage connection either at the servo or at the control surface; at the control surface, move the linkage out one hole to reduce the deflection, OR at the servo move it in one hole on the servo arm. Quote Link to comment Share on other sites More sharing options...
Ultymate Posted February 6, 2012 Share Posted February 6, 2012 I would be loath to tell you to move linkages in or out willy nilly to get surface throws correct as by doing so particularly with a novice builder /pilot you could be inducing servo overload and or the possibility of surface flutter. In my book it's perfectly ok to use a modern day radio to set throws via end point subtrim and rates. Quote Link to comment Share on other sites More sharing options...
FlyinBrian Posted February 6, 2012 Share Posted February 6, 2012 By using EPA / Travel Adjust to set the throws you effectively reduce the resolution of the channel. Get the throw as close as possible by adjusting the connections at the servo / control horn before fine tuning with EPA if needed. Move the linkage In on the servo end and out on the control horn to reduce movement and vice versa to increase. Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted February 6, 2012 Share Posted February 6, 2012 If this buzzing stops when you adjust the end point just one click or so I wouldn't worry about it to be honest. On the wider point of "linkage adjustment" vs "end point adjustment" I think both parties are right. Gross travel adjustment achieved via end point adjustment is not a good idea - it does significantly reduce the resolution of your radio sysyem. What's the point in having 1024+ resolution if you're only operating over 450 steps? Equally, I do think the days of fine tuning linkage travel mechanically have gone - we don't need to do this anymore. When systems had limited respolution - then yes it was needed. But now I think we can afford to sacrifice a little resolution for convienence. My personal approach is very like Brian's. Get it about right with the linkage - fine tune with the end-point travel. If I'm getting below about 80% travel - I'd revisit the linkage because its probably not as close as it could reasonably be! BEB Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted February 6, 2012 Share Posted February 6, 2012 All good stuff from the guys there.....I would add that some servos will buzz under the slightest load.....even just supporting the weight of the control surface..... As long as the servo isn't under a lot of strain I'm sure you'll be fine......ask an experienced modeller to check if you can.... Quote Link to comment Share on other sites More sharing options...
Chris Procter Posted February 6, 2012 Author Share Posted February 6, 2012 Some really great ideas and thoughts in the last few posts guys, thank you. I'll try and get the deflections nearer with the linkage adjustments rather than EPA, and hopefully cure this. Living and learning as they say. I'll repost here with any news. Cheers Chris Quote Link to comment Share on other sites More sharing options...
Chris Procter Posted February 7, 2012 Author Share Posted February 7, 2012 All much better thanks to all the advice. Now to get the engine run in and let an experienced hand give it it's first flight, hopefully the weekend weather will play nicely ! All the best Chris Quote Link to comment Share on other sites More sharing options...
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