Push rod flex
04-26-2005 | 09:28 AM
#1
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From: Montreal,
QC, CANADA
Push rod flex
Hey guys/gals
I have 2 problems with my spad kit. First of all, the kit came with, what looks like cooper push rods (look at pic bellow) and I'm think they may flex/bend if I use them. What are your experiences with plain metal push rods without any tubing to prevent flexing?
First problem: Plane is nose heavy.
Second problem: all my servos setup are working fine except for my rudder servo, I beleive it's stalling (I hear a humming noise coming from the servo, even when it's in neutral). And I'm having a hard time gluing the push rod tubes to the pvc fuselage because of several factors.
I think I can fix both those problems by moving the rudder servor and the elevator servo (If I have to) from inside the fuselage ( right behind the landing gear) to outside bolted right in front of the stab. And use the cooper push rod that came with my kit. I don't think I'll be able to do that and use my plastic push rod tubes (Because I have no where to glue them if they servos are on top of the fuselage.) So I have no choice (I beleive) other then to use those metal push rods. But like I said earlier, I'm concerned with push rod flexing...
What do you guys think?
Sorry for the typos, I'm at work, it's busy and I had to make it quick :-)
I have 2 problems with my spad kit. First of all, the kit came with, what looks like cooper push rods (look at pic bellow) and I'm think they may flex/bend if I use them. What are your experiences with plain metal push rods without any tubing to prevent flexing?
First problem: Plane is nose heavy.
Second problem: all my servos setup are working fine except for my rudder servo, I beleive it's stalling (I hear a humming noise coming from the servo, even when it's in neutral). And I'm having a hard time gluing the push rod tubes to the pvc fuselage because of several factors.
I think I can fix both those problems by moving the rudder servor and the elevator servo (If I have to) from inside the fuselage ( right behind the landing gear) to outside bolted right in front of the stab. And use the cooper push rod that came with my kit. I don't think I'll be able to do that and use my plastic push rod tubes (Because I have no where to glue them if they servos are on top of the fuselage.) So I have no choice (I beleive) other then to use those metal push rods. But like I said earlier, I'm concerned with push rod flexing...
What do you guys think?
Sorry for the typos, I'm at work, it's busy and I had to make it quick :-)
04-26-2005 | 09:52 AM
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From: Aurora,
CO
RE: Push rod flex
Hmm, never heard of copper push rods. As far as the nose heavy condition, try moving servos like you said as well as the battery. The battery will help plenty. In most cases you can balance an airplane just like this. Push rod flex is a big problem for a lot of aircraft, so many are going to a pull pull setup. This is a more complex way to go but it does save weight and there i virtually no slop in the cntrols. Another type of pushrod is the carbon fiber type. These are extremely light weight and and stiff. As far as the rudder servo goes, I think it is just having trouble centering. Check to make sure that the rudder isn't hard to move or their isn't excessive ca in between the rudder and fin. If the airplane is sitting on the tailwheel, try lifting the tail up and see if it stops. If that doesn't fix it then you may need to look into the servo. Hope this helps
04-26-2005 | 10:57 AM
#3
RE: Push rod flex
Binary-
A couple thoughts:
First, your SPAD kit is basically a SPAD Debonair with some modifications to make it slightly better looking. Check out Debonair instructions at www.spadtothebone.com for some ideas.
A standard Deb has the elevator and rudder servos in the tail. You could do that if you wanted. You just need to make sure you keep them out of the oil residue from the engine. Anything longer than about 8" is too long for a wire pushrod without a sleeve. My Deb pushrods were about 12" and I eventually just bought a carbon fiber rod to make stiffer pushrods. Dowel will also work.
As far as the balance is concerned, first make sure your battery is as far back as possible. Mine is just behind the wing. Next, think about moving the wing. The method for balancing a Deb is to temporarily attach the wing and move the wing forward or back until it is properly balanced. To move the CG back, you move the wing forward. Then you drill the holes for the dowels that hold the rubber bands.
-Scott
A couple thoughts:
First, your SPAD kit is basically a SPAD Debonair with some modifications to make it slightly better looking. Check out Debonair instructions at www.spadtothebone.com for some ideas.
A standard Deb has the elevator and rudder servos in the tail. You could do that if you wanted. You just need to make sure you keep them out of the oil residue from the engine. Anything longer than about 8" is too long for a wire pushrod without a sleeve. My Deb pushrods were about 12" and I eventually just bought a carbon fiber rod to make stiffer pushrods. Dowel will also work.
As far as the balance is concerned, first make sure your battery is as far back as possible. Mine is just behind the wing. Next, think about moving the wing. The method for balancing a Deb is to temporarily attach the wing and move the wing forward or back until it is properly balanced. To move the CG back, you move the wing forward. Then you drill the holes for the dowels that hold the rubber bands.
-Scott
