RE: Bob Cat Copy Falcon 120 Jet
I am using the Spektrum DX7, and ran out of channels to operate the smoke system, so linked it into the undercarriage, ie gear up smoke on ( I use a pneumatic system not electric). I have now used the rudder mix switch on the top r/h side of the tx. I mixed this to the undercairrage channel, so when selecting gear up, the servo arm just stops short of opening the smoke valve. I flick the rudder mix switch, and servo moves just enough to operate the valve. There is an offset function in the rudder mix, which makes the undercariage servo do all sorts of different movements when the rudder stick is moved, so took a while to set it up without servos binding, but works well. I can now retract the gear then switch the smoke on when i like.
Ref my nose gear extension mechanism, I found when i was up the flying field that i would occasionally get an air leak, across the the piston o ring. The leak stopped at pressures around 60 psi, but any higher and it would leak. On test in the house all was fine. I was chatting to a jet model suppliers about the problem, and they said they get a lot of selector valves back, which seem to leak, but in fact it is the o ring seal on the piston rolling over (some well know high end brands suffer from this as well). I tried a well known high end brand piston ram and found similar problems myself. I wanted to order some BVM O ring lube to try and irradicate the problem, but shop was out of stock. I tried 3 in 1 spray oil with PTFE lube content from Halfords, and hey presto no leaks, so far. Havnt flown the model yet, but have had it pressurized outside and all appears ok. Might help someone with leaking rams. Also no need to disassemble, just spray it into the air pipes and on the next operations it lubes itself. This has worked on my home made jack and selector valve, so cant say it will work on yours.
On my 68th, 69th and 70th flights, the engine failed to start first time, strange. I removed the glow plug, and found a perfect ring of coke had formed around the plug, covering the element. Turned the model upside down and removed it and fitted a new plug just in case, hopefully that was the problem.
I am using a flow reducer on air up spring down retracts now ( havnt tried it in flight yet). I use a Skymaster quick disconnect coupling in the main air up line. I fit a miniture ball bearing in the disconect before screwing the two halfs together. On the side of the coupling that has the o ring and push out nipple, I cut a cross slot across the end of the brass nipple ( the bit inside the valve body). The reason for this is when you select up, the ball bearing is forced to the end which has not been cut and the ball tries to seal the tube off. Obviously it will never seal perfectly, so the air leaks past and gives you smooth slow retract. Now when you select down, all that air has to escape quickly to allow the gears, (especially the nose, which is fighting the air loads) to spring down rapidly to lock properly. The slot cut across the other nipple, ensures the ball can not restrict the air flow too much. This is I think is a better system than using a restrictor ( a brass nipple with a tiny hole in it) as you will get a restriction in both directions, cheers Tim