|
|
Post by cubflyercameron on May 13, 2010 8:37:26 GMT 1
Has anyone got a pic of a single servo aileron set up on a super cub? or tried it?
I would like to know how they work and how to set them up
Thanks Cameron
|
|
|
|
Post by ginginho on May 13, 2010 11:12:56 GMT 1
Cameron, Sorry I don't have pictures but I did help (=do) the conversion to a single servo for a mate, reusing the HZ 5 wire rudder servo mounted in the wing. We used what are called "snakes" in the UK, that is thin plastic rods that run inside close fitting tubes. These still allow movement when bent. We had to be fairly careful with the bend of these to ensure that there was as little friction as possible. I also had to fashion a connection piece that went between the servo arm, capable of swivelling (again to reduce the friction), linking to each of the snake ends in the centre of the wing. Once the bends in snakes were as desired, they were taped to the wing (underneath). I hope this helps. If I can get a picture from my mate, I'll post in on here.
|
|
|
|
Post by Legot on May 14, 2010 2:42:09 GMT 1
|
|
|
|
Post by Dillzio on May 14, 2010 2:51:30 GMT 1
Does the bellcrank defeat the purpose of the Flex cable? I don't think so. Quite right. Having a 90 degree bend in the cable puts a lot more stress on the servo, and running the two off one servo doubles the load so it's like having a 180 degree bend (or so says the guy at the hobby shop I was talking to about running two flaps off one servo). By using a bellcrank, you're putting a lot less strain on the servo. |
|
|
|
Post by cubflyercameron on May 14, 2010 6:51:28 GMT 1
well thats a hard one. I think I'll just go with two just to be safe ;D .
ginginho: With the parkzone servos, are they capable of running ailerons off just one? or will it eventually burn out
Legot: So the servo pulls and pushes a cable that pulls a rod up and pushes down ? or am i just imagining this. Good pics and thank you very much for them
|
|
|
|
Post by ginginho on May 14, 2010 9:16:21 GMT 1
well thats a hard one. I think I'll just go with two just to be safe ;D . ginginho: With the parkzone servos, are they capable of running ailerons off just one? or will it eventually burn out Legot: So the servo pulls and pushes a cable that pulls a rod up and pushes down ? or am i just imagining this. Good pics and thank you very much for them Well it's still working now, so that's about a year that it's been going. Although I have to admit that the pilot tends to fly his funjet more often these days. The snakes I mentioned are different that those in Legot's pictures, more like these. There is sufficient distance (more than a foot IIRC) between the wing centre to the aileron control horns so there is very little friction. The trick is not to put a bend in it, but to have a gentle arc over the whole distance. Another tip I heard was if you are concerned with them rubbing a bit, to coat the inner rod in talcuum powder or pencil rubbings (graphite) before installation. There was no need to do this on the install I did. |
|
|
|
Post by ginginho on May 14, 2010 9:26:04 GMT 1
By using a bellcrank, you're putting a lot less strain on the servo. Not necessarily, you are assuming the pivot axle of the bellcranks are a lower friction co-effiecient than the rods when installed. I don't see why you'd want to use this sort of arrangement for flaps though (near fuse part of the wing, presumably). The design Legot has done is the obvious method, a sort of torque rod, which are available commercially. |
|
|
|
Post by Legot on May 14, 2010 23:50:03 GMT 1
It is a nicely working setup. Could the snakes you are talking of be nylon ging? From the looks of the pics on that page, it seems that they are nylon, and I have a feeling that smooth nylon rubbing on smooth nylon has much less friction than the Sullivan flex cables I used, but it sems like it might stretch and develop a little slop. Have you seen this happen? (BTW The flex cables do require a bit of additional trimming as they expand in heat, it doesn't help that it's already 90, and this is still cool weather) In general, bell-cranks often take away much of the friction that cable only setups have. They tend to allow for most of the bends to be left out of the cables, reliving pressure on the inner walls of the tube. And for flaps that use the bell-cranks, I've mostly seen where they have the servo in the middle, two pushrods going from opposing ends of the servo arm, bell-cranks, and a pushrod between the bell-cranks and the flaps. This allows for a single servo, to move two pushrods that are not symmetrically placed, to the bell-cranks, which negate the in-symmetry, which then allows the flaps to move evenly. And yes Cubflyercameron, you prety much nailed how they work  |
|
|
|
Post by Dillzio on May 15, 2010 0:41:30 GMT 1
It is a nicely working setup. And for flaps that use the bell-cranks, I've mostly seen where they have the servo in the middle, two pushrods going from opposing ends of the servo arm, bell-cranks, and a pushrod between the bell-cranks and the flaps. This allows for a single servo, to move two pushrods that are not symmetrically placed, to the bell-cranks, which negate the in-symmetry, which then allows the flaps to move evenly. Or, you could have push/pull cables for the flaps that are symmetrically placed, so that one pushes and the other pulls, and reverse one of the bell cranks so they both move the flaps the same way. Might look a bit neater. |
|
|
|
Post by cubflyercameron on May 15, 2010 1:10:29 GMT 1
OK I've decided to go with two servos much easier and neater i reckon. thanks for your help Cameron |
|
|
|
Post by Legot on May 15, 2010 19:35:58 GMT 1
Yeah, two is a bit neater, but with the one Servo it still looks good because my covering job is done!!! Pics maybe by tuesday. with the covering it acctualy looks like two servos, bu no! It's one!
As you can tell I am very proud of it.
Now onto making needless suggestions for two servos.....
I hope yours gets them soon!
|
|
|
|
Post by ginginho on May 16, 2010 9:40:19 GMT 1
It is a nicely working setup. Could the snakes you are talking of be nylon ging? From the looks of the pics on that page, it seems that they are nylon, and I have a feeling that smooth nylon rubbing on smooth nylon has much less friction than the Sullivan flex cables I used, but it sems like it might stretch and develop a little slop. Have you seen this happen? TBH, I'm not sure what they are made of however I've used them elsewhere (depron wing) and I haven't noticed any stretching. |
|
