Control arm
02-17-2007, 08:14 AM
#26
RE: Control arm
ORIGINAL: Hammbone
O.K. then, has anyone had the arm strip out? Or has anyone had the arm wear and develope slop?
Jim
O.K. then, has anyone had the arm strip out? Or has anyone had the arm wear and develope slop?
Jim
02-17-2007, 08:58 AM
#27
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RE: Control arm
Have you even looked at the arms we are talking about? They will not twist under a load. They are a high strength arm. Put one in a vise and take a pair of pliers and try to twist it. Now take your aluminum arm and do the same thing. You might be surprised. (I haven't tried this so I might be surprised)
I am no expert on metals or plastics, but I'm sure there are some plastics that are stronger than some aluminums. These black plastic Hitec arms that come with the 5955 may be just as strong or stronger than an aluminum arm. They sure seem very strong to me. Why would I pay another $10 for a different arm when this one could be just as strong or stronger? I haven't heard of anyone having problems with this black plastic arm.
Now if I hear about some problems or failures, I may be switching to aluminum arms. That's why I asked if anyone has had problems.
We are all free to use whatever arms we want on our planes, and you won't find me argueing with someone about this. I'm all for discussing it to hopefully learn something though. I would be very interested in some destructive testing to see at what point (lbs of force) these arms fail, and I would be interested to see how this compares to an aluminum arm.
Jim
I am no expert on metals or plastics, but I'm sure there are some plastics that are stronger than some aluminums. These black plastic Hitec arms that come with the 5955 may be just as strong or stronger than an aluminum arm. They sure seem very strong to me. Why would I pay another $10 for a different arm when this one could be just as strong or stronger? I haven't heard of anyone having problems with this black plastic arm.
Now if I hear about some problems or failures, I may be switching to aluminum arms. That's why I asked if anyone has had problems.
We are all free to use whatever arms we want on our planes, and you won't find me argueing with someone about this. I'm all for discussing it to hopefully learn something though. I would be very interested in some destructive testing to see at what point (lbs of force) these arms fail, and I would be interested to see how this compares to an aluminum arm.
Jim
ORIGINAL: Silversurfer
I can't provide any answers as to whether or not any of the H/D plastic arms have broken or stripped, but I do feel that if anyone is using a ball link attached to a plastic arm of any type they are being extremely careless and taking great risks. If you're going to go plastic, use a standard type clevis. Ball links are for arms that won't twist under a deflected load as plastic will.
As for my opinion about plastic arms and big planes in general...if you're going to invest that much ($2,500 and waaay up) why does one want to skimp on the part that connects all the moving parts of a flight surface? People will spend $115.00 on a servo but won't flip another $10.00 for a high strength arm? Makes sense to some I suppose.
I can't provide any answers as to whether or not any of the H/D plastic arms have broken or stripped, but I do feel that if anyone is using a ball link attached to a plastic arm of any type they are being extremely careless and taking great risks. If you're going to go plastic, use a standard type clevis. Ball links are for arms that won't twist under a deflected load as plastic will.
As for my opinion about plastic arms and big planes in general...if you're going to invest that much ($2,500 and waaay up) why does one want to skimp on the part that connects all the moving parts of a flight surface? People will spend $115.00 on a servo but won't flip another $10.00 for a high strength arm? Makes sense to some I suppose.
02-17-2007, 09:12 AM
#28
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RE: Control arm
ORIGINAL: Silversurfer
I can't provide any answers as to whether or not any of the H/D plastic arms have broken or stripped, but I do feel that if anyone is using a ball link attached to a plastic arm of any type they are being extremely careless and taking great risks. If you're going to go plastic, use a standard type clevis. Ball links are for arms that won't twist under a deflected load as plastic will.
As for my opinion about plastic arms and big planes in general...if you're going to invest that much ($2,500 and waaay up) why does one want to skimp on the part that connects all the moving parts of a flight surface? People will spend $115.00 on a servo but won't flip another $10.00 for a high strength arm? Makes sense to some I suppose.
I can't provide any answers as to whether or not any of the H/D plastic arms have broken or stripped, but I do feel that if anyone is using a ball link attached to a plastic arm of any type they are being extremely careless and taking great risks. If you're going to go plastic, use a standard type clevis. Ball links are for arms that won't twist under a deflected load as plastic will.
As for my opinion about plastic arms and big planes in general...if you're going to invest that much ($2,500 and waaay up) why does one want to skimp on the part that connects all the moving parts of a flight surface? People will spend $115.00 on a servo but won't flip another $10.00 for a high strength arm? Makes sense to some I suppose.
Not sure if the 5955 has enough torque to strip either the plastic or aluminium splines, lets face it aluminium is a fairly soft material. Would have thought Hitec HD gear is designed with that in mind?
02-17-2007, 10:25 AM
#29
RE: Control arm
I also question the HD arms that come with the powerful Hitec servos. I am using them on my new PAU 330L and they seem strong and tight. After doing some resurch on plastic arms, like the Nelson's setups, they recomend replacing the plastic arms after so many flights. I don't think this is the case with the new aluminum style arms. I do plan on changing mine out soon, but I think the HD plastic ones are good for so many flights. And keeping them very snug with the screw is a must, where the SWB double locks are an added protection.
02-17-2007, 11:01 AM
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RE: Control arm
I have them in a AW 36% Katana and I have blocked up the surfaces and lifted the entire plane up and down using the stock black arms for over 10 minutes with no problems. They did get a little warm but not hot. Plane weight is 28lbs 6oz.
I was testing them out before flying them. Two per aileron, 1 per elevator stab and two for rudder.
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I was testing them out before flying them. Two per aileron, 1 per elevator stab and two for rudder.
[img][/img][img][/img]
02-18-2007, 10:01 AM
#31
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RE: Control arm
Thank you for all your replies. As hammbone says you have to see these arms before making a generalization about plastic. I applied voltage to the servo and pushed very hard on the linkage with a force that would easily bust any control surface with no problems. I have aluminum arms I could use so it isnt a cost issue. I have no problem using aluminum arms but I dont think they are necessary here. On the other hand I have JR 8600a servos that come with the same arms as a 40 oz servo. Hopefully manufacturers will wake up and include nice arms for us.
02-18-2007, 11:24 AM
#32
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RE: Control arm
Using the plastic arms supplied with the 5955 servo's will never fail if a metal pin type clevis is used on the servo arm end. If you run a ball type link it "may" be possible to fail due to twisting on something like a rudder installation in which I would just go with the aluminum arm....I'd use them on anything with a heavy duty clevis on the arm, Buzz
