Richard Webb 2 Posted October 31, 2014 Share Posted October 31, 2014 This was my FMS b25 that id bought s/h for the princely sum of £65. It needed a new pair of engine nacelles and a new pair of wings but after meticulous replacement i finally maidened it the other day. The take off run was perfect, track dead straigt and true, it rotated beautifully but the trouble was it kept climbing, and climbing with me furiously working the elevator control until it tip stalled and well a mad dash out the way resulted in this It would appear the servo in the tail failed in the up position. While checking the servo i noticed the plug on the servo lead which is buried deep in the fuselage was partially disconnected whereas the rudder one was still firmly connected. It would seem that when the model was built the previous owner hadnt fitted clips and when they pulled the extention lead through it dislodged the connector. It was then just waiting to happen. It seemed to work fine on the ground but i assume our slightly bumpy strip made it worse and with the stick pulled back the elevators just stayed there. and in fact if you look at the picture you can see they are still facing skywards! The one problem with the b25 is that the wiring is such a ball of wires in a tiny little hole that its easy for one to get snagged or pulled, i run mine with a 3s 3350 and it can just about get it in and that was even with some of the canopy cut away inside! The object of this is basically to say check everything on a new or used model and use connector locks. Anyway B25 mk2 is on its way from Italy as it seems no one has the silver one in the uk anymore. Richard Quote Link to comment Share on other sites More sharing options...
Masher Posted October 31, 2014 Share Posted October 31, 2014 I have learnt the hard way that if acquiring models from just about anywhere including expert builders, you must assume that everything is wrong until checked! Go through everything carefully is the only way. Quote Link to comment Share on other sites More sharing options...
Stevo Posted October 31, 2014 Share Posted October 31, 2014 Every S/H model I've ever purchased I've always stripped down, and rebuilt, and yes servo locks always. Quote Link to comment Share on other sites More sharing options...
Dave Hopkin Posted October 31, 2014 Share Posted October 31, 2014 I much prefer to cut the servo lead and solder in a length of servo wire - then I know it cant come undone Quote Link to comment Share on other sites More sharing options...
Nic Jarman Posted November 14, 2014 Share Posted November 14, 2014 I had been given a balsa Tiger Moth. I converted it to 2.4GHz and checked the operation of all the control surfaces rigorously. Then I set the throttle linkage to the 4 stroke engine. I took the plane into the garage and started the engine, tick over a bit fast but the throttle cut working fine. Now time for the full beans and set the mixture; the whole engine mount/bulkhead and tank mount came out and fortunately the engine cut when the servo link snapped. My Corsair was infront of it, a near miss. Quote Link to comment Share on other sites More sharing options...
Nic Jarman Posted November 14, 2014 Share Posted November 14, 2014 Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted November 14, 2014 Share Posted November 14, 2014 Yes have to agree Check .........check and check again even if its something that look solid like battery, servo, engine mounts etc give them a good tug and if in doubt re glue them . Last year I bought a large 30cc Chipmunk from a guy down hove way. He seemed an OK sort and assured me it had been flown and all was ok . He lied , glad I hadn't bought a car from him . It was a can of worms as one thing after another was found to be faulty during the check over and it could not possibly have been flown the way it was.After a few days I thought I had it sorted and went to our field to fly it . It took off beautifully climbed out then went haywire as if the battery had slipped to the tail .....it had! Then I found I couldn't close the throttle .I had fitted an ignition cut out so switched off the engine and managed to glide it to an area of standing corn that cushioned the arrival . Total disaster averted but could have been much worse. The COG had moved as the battery mount that looked securely screwed in was only screwed to 1/6th balsa with no glue and this must have let go on the take off run. Then the throttle servo problem . This had worked perfectly during run-ups etc but was now the gears were slipping ? As soon as I removed it from its mounting the fault was obvious . Two of the screws that hold the servo case together were missing and the other two were very loose . It had to have been fitted like that as the screws couldn't have come out in situ as there wasn't enough room . The servo all looked ok in the model and appeared firmly fitted. I put the above all down to me for not being more thorough. So DONT believe what anyone selling a model says unless you have seen it fly and you know them very well and still check it thoroughly. Edited By Engine Doctor on 14/11/2014 17:20:53 Quote Link to comment Share on other sites More sharing options...
Malcolm Blake 1 Posted November 14, 2014 Share Posted November 14, 2014 Surely we don't do these checks just when we get a new or second-hand model. Ilike to carry out these checks everytime I take my models out of the shed and before I start a days flying. Quote Link to comment Share on other sites More sharing options...
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