Danny Fenton Posted October 21, 2014 Author Share Posted October 21, 2014 This was how it was done on the Bistormer.... Cheers Danny Quote Link to comment Share on other sites More sharing options...
Dennis Mulhair Posted October 21, 2014 Share Posted October 21, 2014 Danny, I know this plan is very old and when it was drawn up the way the flaps & ailerons were operated reflected the equipment available then. Why I ask did you not take the option to install separate servos for each surface? By the way still on the rudder and your work looks marvelous! Dennis Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted October 21, 2014 Author Share Posted October 21, 2014 Thanks Dennis, keep at it you will get there I like doing this the bellcrank way as I find it lighter. It also means that replacing servos is easier and doesn't involve hacking the wing open. It isn't simply the weight difference between two small servos and one slightly larger one its the extra cables, connectors linkages etc, it all adds up IMO..... Cheers Danny Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted October 22, 2014 Author Share Posted October 22, 2014 Still mulling over whether or not differential IS required on the Chipmunk. So I will leave the setup as I have it for now. Its easy enough to alter later. Did the flap servo mount and linkage..... I have left the retainer off the flap servo, so you can see the construction. If you are doing these with IC you may want to consider foam pads above and below, and a slightly poorer fit, to allow some vibration absorbtion. Cheers Danny Quote Link to comment Share on other sites More sharing options...
Martyn K Posted October 22, 2014 Share Posted October 22, 2014 Hi Danny I may have missed this, but how are you connecting push-rods to ailerons and flaps..? Looking at your flap and aileron servo layout, I think that I may go for 2 MG mini servos sat side by side in the centre section bays - each one driving a separate aileron. That will allow me to mix in any differential required. Martyn Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted October 22, 2014 Author Share Posted October 22, 2014 Hi Martyn, yep that will work and gives you redundancy It is only a threaded rod with a clevis at the bellcrank to allow adjustment and a 90 degree bend at the other I have used fairly thin bellcrank ply plates and they are flexing a bit, so make your own judgement on whether you go down this route definitely don't use 1/32 as I have, stick to 1/16 Birch ply. I will see what happens with the ailerons, may need to beef it up. Cheers Danny Quote Link to comment Share on other sites More sharing options...
Martyn K Posted October 22, 2014 Share Posted October 22, 2014 That is quite neat. (understatement of the year). As its quite close to the hinge line, I would have thought you may have used some reduction in the bellcrank to get rid of any excess servo travel. I cant imagine that a lot of movement will be required. M Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted October 22, 2014 Author Share Posted October 22, 2014 Hi Martyn, no the servo travels nearly fully to go from up to down so keeping the servos resolution. It will go down to about 45 degrees but we only need 30 so will have to play with end stops Just packing in the flap leading edge, I am only going to do the top half as the bottom wont be seen, the top probably wont be seen either but there you go, its just my OCD The upper curve is a radius from the hinge point, the lower is not, but I am going to chop the lower template off, you can see the block that I have added. Cheers Danny Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted October 22, 2014 Author Share Posted October 22, 2014 And the fit was well worth the effort........ Cheers Danny Quote Link to comment Share on other sites More sharing options...
Andrew Price 2 Posted October 22, 2014 Share Posted October 22, 2014 Yes it was Danny. That looks bog on Danny. Very nice. Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted October 22, 2014 Author Share Posted October 22, 2014 Hi Chaps, sorry if my answer was a bit abrupt Martyn, trouble with rushing sorry about that. The hingeline remember is well below the lower surface, so the horn being above the middle means it is a good length moment arm, hence full throw I have used the outer holes on the servo arm and the bellcrank. I have struggled with the aileron, hopefully my exploits will help you guys. I sorted the pushrod out very quickly, however it was done the same way as the flap, with the clevis on the bellcrank and just a ninety bend at the surface horn. This worked fine, but I thought it might be better if the clevis was at the aileron end as the clevis was very close to the crossover of the teo piano wires on the bellcrank. Anyway I wont go into why it wont' work with the clevis at the aileron end but it is to do with where the horn is on the aileorn and how it ligns up with the bellcrank. I had spent all evening only to end up back where I started I did how ever, beef up the leading edge of the aileron, so that the shroud gap is constant through out travel. On the flap I had to add very soft 1/4 and sand it to profile, on the aileron again a strip of 1/4 was added but much of it was sanded away. I had a lot of grief doing this as the ailrons were already radiussed (is that a word?) If you make the ailerons thicker from the get go you wont have this problem. Right over to the other side. I will also just say I am not happy with the aileron and flap trailing edges, so we will be doing another little trick here to create lovely sharp but ding resistant trailing edges. Other side first though.... Cheers Danny Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted October 22, 2014 Author Share Posted October 22, 2014 In the last picture above you can see that the piano wires get very close to each other. We do not want them touching ideally, though this would have been more of a problem with 35Mhz, its not such a problem with 2.4Ghz. But anyway why tempts fate. If you look at the first rib to the left of the belcrank you might be able to see a small piece of 1/8 x 1/8 theis is just touching the piano wire and stopping it from riding up. They don't touch anyway, but this will stop the wires moving due to vibration and touching causing an arc of static, or whatever it is that metal to metal contact causes..... Cheers Danny Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted October 23, 2014 Author Share Posted October 23, 2014 Okay flap linkages not going very well. In fact I have just ripped it all out again. Flaps are fine it's the position of the port bellcrank that is the problem. Firstly the bellcrank is mounted between two flimsy 1/16 balsa ribs, recipe for disaster in itself. I beefed up the rib, still not right. Secondly the bellcrank is one side of the rib and the horn the other, this means the arm has to be at a slightly different angle to the starboard. With bellcranks you need to get the angles exactly the same or it will not give even travel. Thirdly the dreaded slop, the starboard flap is fine but the port one is not good. I think this is down to the slightly longer piece of piano wire on this side bowing, amongst other things. More news if I get a chance to take a look over lunch Cheers Danny Quote Link to comment Share on other sites More sharing options...
Nigel Day Posted October 23, 2014 Share Posted October 23, 2014 Hi Danny. Assuming that you have/do beef up the two ribs, why not cut a small slot in the inboard rib so that the inner arm of the bellcrank sits the right side of the rib? You can strengthen the slot slightly if need be. Why not use stronger piano wire on the link too. It won't add much weight surely? Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted October 23, 2014 Author Share Posted October 23, 2014 Have you got a camera in my workshop? Tha'ts exactly what I am doing on both counts LOL .....uncanny Nigel.... Cheers Danny Quote Link to comment Share on other sites More sharing options...
Nigel Day Posted October 23, 2014 Share Posted October 23, 2014 No silly, I just used the Force. Edited By Nigel Day on 23/10/2014 10:36:26 Quote Link to comment Share on other sites More sharing options...
John Timmis Posted October 23, 2014 Share Posted October 23, 2014 Hi Danny, This looks very interesting. I was wondering if you had a method to make nice sharp trailing edges. I've just finished solartexing my wings so next job is to assemble the ailerons & flaps to the wing. Do you have a source of small nylock nuts or do we use a thread locking glue on the hinges? I was abit concerned when covering the flaps & ailerons about their lack of torsional rigidity. They seem ok now they are covered but it would have been easy to warp. I expect Dennis used doped tissue on the original model. Cheers John. Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted October 23, 2014 Author Share Posted October 23, 2014 Lol well the disturbance in the force is strong..... Hi John, interesting is one word for it. I have a feeling I am trying to be overly precise with the linkages, but I must confess the pressure of others watching and relying on me to get it right is a bit heavy at times. Keeps me on my toes I suppose. I thread lock the hinges definitely! I use the blue which is medium I belive? It seems to be working well. If you add the wood to the leading edge of the ailerons and flaps they stiffen up considerably, but yes you are probably right dennis would probably have used tissue or perhaps silk over tissue, using wall paper paste that's a subject for another time Cheers Danny Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted October 23, 2014 Author Share Posted October 23, 2014 And just to show how strong the force is with Nigel, here is exactly what he suggested and its much better. The slop is reduced, the geometry is now symetrical and the flaps operate together. So a result.... eventually I am starting to think two servos would have been so much easier..... Anyway this picture also highlights how much better the rounded leading edges looks when deflected on the starboard flap. Cheers Danny Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted October 23, 2014 Author Share Posted October 23, 2014 Managed to add the leading edge to the port flap, gives me a chance to show how its achieved in a little more detail. These surfaces are not to scale, but basically if you have a shroud then the radius can be marked with a compass at either end using hinge centre to upper surface as the distance. Sand to the lines at either end using a long sanding block, big Permagrit if you have one Then trial the fit, and mark where the fit is tight, sand the lines away and try again, eventually you should have a nice fit thoughout the travel. this wil do they will get a bit more sanding closer to covering. Aileron next.... Cheers Danny Quote Link to comment Share on other sites More sharing options...
Jack Banner Posted October 23, 2014 Share Posted October 23, 2014 Guys, I am not building a chipmonk but the last 3 pages or so has been very valuable to me as I am updating a scale model that currently has a single servo and (very poorly implemented) bellcranks for ailerons. Thanks to this thread I will almost certainly go with two smaller servo's in the centre of the wing Quote Link to comment Share on other sites More sharing options...
Nigel Day Posted October 23, 2014 Share Posted October 23, 2014 Lovely Danny. Thanks for the detail. The razor plane is my weapon of choice where possible so I'll start with that then a long bit of wood with sandpaper glued on until Santa calls. Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted October 23, 2014 Author Share Posted October 23, 2014 Posted by Jack Banner on 23/10/2014 14:13:40: Guys, I am not building a chipmonk but the last 3 pages or so has been very valuable to me as I am updating a scale model that currently has a single servo and (very poorly implemented) bellcranks for ailerons. Thanks to this thread I will almost certainly go with two smaller servo's in the centre of the wing Hi Jack, glad its been of use Bellcranks can be quite difficult to get to work well. But I think they are worth it. Once working and properly fitted they shouldn't need any attention and shouldn't fail as a servo might. But precision is the key. Hi Nigel, yes i should have said I use the plane to get the wood down to an approximation before the long sanding block came into play. FYI I used the long balsa cabin wooden block not the Permagrit, its a bit slower as the grain is finer than even the fine side of the Permagrit. Cheers Danny Quote Link to comment Share on other sites More sharing options...
Charles Galloway Posted October 23, 2014 Share Posted October 23, 2014 Just about to bend the u/c wire. I notice you've cut your legs off ( Maybe to match your dwarf carpenters!). I assume you are going to use oleos Have you decided which ones? Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted October 23, 2014 Author Share Posted October 23, 2014 Hi Charles I have some from HobbyKing, I think we showed them on one of the threads???? The dwarf carpenters aren't good with a dremel Anyway the anti torsion arms are a bit big, and they need the ends drilling to take a couple of grub screws but should work. Failing that some very soft sprung Unitracts might be worth the investment. Here is a link Cheers Danny Edited By Danny Fenton on 23/10/2014 16:03:30 Quote Link to comment Share on other sites More sharing options...
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