Thread: Discussion Citabria Propeller and shaft
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Old Apr 17, 2008, 04:23 AM
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Plymouth, Devon
Joined May 2007
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What I did after breaking my prop was to open the plane up, carefully cut around the gearbox and pull it free, not forgetting it has two posts going into the foam. Next, using a pair of pliers, carefully remove the collet from the back of the shaft - I recommend doing this over a box with a towel in so when it 'pings' off you don't lose it - then pull out the rest of the shaft from the front, and strip the gear off it. Use a gentle side to side rocking motion as you pull, it'll come off easily enough. What I did next, and can't recommend enough, is to remove the brass bushes from the gear assembly, ream out the holes with a 3mm drill bit, and fit two 1x3x1mm ball races. I swear I get an extra 5 minutes out of my plane because of this mod, my average flight time, without too much throttle management, is over 20 mins. And you never have to lube the shaft again, lubrication actually damages these really tiny bearings. If you can't find the ball races, try, 2.25 for a set of 2 and a length of cf rod. He sells it as an upgrade for the piccoz. Anyway, next cut a length of 1mm cf rod, about 1 1/2", and slightly round the ends off with a nail file or whatever, then fold a tissue over a few times, put that over the cf, and grasp it firmly with your pliers. If you use a bit of twisting and a bit of force, you'll be able to pop a prop straight on without enlarging the hole at all, and it won't need any glue so it can be taken off later if necessary. You will need a new prop though, the remains of the old broken shaft won't let you get your new shaft in deep enough (ooh-er missus). Then, for reinforcement, cut a 6mm length of carbon tube, 3mm od 1mm id, and slide that on the shaft so it's touching the prop, and glue in place. The spur gear goes on next. If you haven't noticed, either side of the gear is a raised piece of plastic, higher on one side than the other. The lower side goes towards the front. The gear is pushed up to the tube, then glued again. You can now feed the other end of the shaft through the gear box, and glue the collet back on to hold everything together again. This takes less time to do than it did for me to describe..... While you've got the gearbox out, I also highly recommend taking off a lot of the downthrust. I've got mine at about 6 degrees now, loads more power when you want it, and cruises nicely on lowest throttle. To do this you just cut a couple of tiny slivers of foam out of the fuse. You can save them to glue back in if you decide you want the dt back again. You will need about 2 clicks of down trim to stop the plane climbing on full throttle, and to leave myself with full control throw I just adjusted the control rod with the servo centred so that the leading edge of the elevator is just a little above the trailing edge of the h stabilizer, and glued in place. Can loop off level fight now, and if you hold full down elev, the plane flies inverted! Also, whilst you've got the fuse open, try moving the control linkages to the inner holes on the control horns, makes the plane much more responsive, especially on the elevator. You just gently wiggle the 'z' bend until it comes out of its hole, then reverse the proceedure to get it into the new one. Don't be too forcefull doing this, you don't want to snap the control rods, gently does it! Sorry for the long, rambling message, I hope you try the bearings if not the downthrust, but pref both. I've got a completely different plane since I did these mods to it, it flies even better than it did stock, and a lot quieter and for a lot longer.

edit; forgot to say that I just used UHU POR to glue the gears back in, after picking off the white mastic type stuff. This seems strong enough, I nosed in at a very steep angle onto concrete the other day and the plane just bounced, only damage a scuff on its 'chin'.
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Last edited by thewildweasel; Apr 17, 2008 at 04:31 AM.
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