carbon fiber servo "arms" from readyheli

[istandalone]

i'm confused as usual. with the servo arms i'm going to link to, i can't figure out which ones i need to use (straight or offset), so i bought both. i know finless was very adamant about making sure the offset is set properly on the servo wheels. this is a clip from the product info for the offset arms. "These have a small offset for use with the stock bellcranks which already have the offset" and this is a clip from the straight arms " These do not have a small offset for use with the CNC bellcranks which already have the offset". i'm confused because it seems that the stock plastic bellcrank arms are offset too? i don't have the plastic ones, but in the pic it looks like they are. has anybody used these arms? and for the cnc head, i should use the straight ones? another reason i'm a bit perplexed is that i've set my servo wheels up with an offset (i've got the cnc head) and there is no binding at all. can someone set me straight? thanks in advance.

[Pinecone]

Plastic bell cranks have offset.

CNC bellcranks do not have offset.

If you have plastic bellcranks, you need to set up servo arms with offset. If you have CNC bellcranks, you need to set up servo arms without offset.

[istandalone]

well goddamn, if i'd have known that, i'd have saved myself at least 3 headaches! thanks. one thing gaui is lacking, is model specific owners manuals.

[istandalone]

also, i ordered both sets not knowing which i'd need. if anyone needs the offset ones, let me know, i'll give them to whomever needs them, and whoever asks me first assuming i can get them in a regular sized postage envolope without going over the weight limit.

[bpd964]

I'll take them...

[istandalone]

sold!! pm me your address, i'll get them out tomorrow or saturday at the latest.

[bpd964]

PM sent... Thank you

[istandalone]

unless there is a delay in how fast pm's get routed, i did not get it.

[Vinger]

Plastic bell cranks have offset.

CNC bellcranks do not have offset.

If you have plastic bellcranks, you need to set up servo arms with offset. If you have CNC bellcranks, you need to set up servo arms without offset.
Gaui part refer:

Bellcranks need to be offset due to front cyclic servos working through a differrent angle than the rear cyclic servo.

Plastic bellcranks have offset for both front and rear bellcranks

CNC bellcranks have less offset for front cyclic servos, with zero offset for rear cyclic.

All this is done so that the swashplate will move linear with the servo movement, without unwanted mixing in the collective pitch travel. (simple geometry)

If you now mix and match differrent manufacturers bellcranks and servo arms you need to electronically mix out this unwanted non-linear movement.

Let us all put this debate to rest, as Gaui did it correctly fot both the plastic and CNC parts.

[istandalone]

i didn't know we were debating. i was just a bit confused about which of those cf wheels to use with the gaui cnc head.

[Pinecone]

Only dabate is that my front CNC bellcranks are setup with 0 offset.

[istandalone]

that's weird. i'm 99% sure that mine (gaui cnc front bellcranks) are setup with offset. i'll have to take a look when i get home from work. i should remember, as i was working on it all day yesterday. those cf wheels are a pita to install. once you get them positioned correctly, they seem to work really well. it's just not a five minute job like i first thought.

[mjdee14]

I just installed a set of CNC last night and they have 4 holes drilled in each, I installed them with offset....

I'm learning even though I don't understand some things...Gaui isn't so dumb...so I'll stick with the offset for now.

At my level of flying it probably doesn't make a big difference anyway.

[istandalone]

i just looked, and yes my bellcranks are set up with the offset. it's a pisser, because i just realized that when i was first building and setting up this 550, i really agonized over getting the offset perfect on the servo wheel. nowhere in the manual did it say that the wheels didn't need the offset if you have the offset on the bellcranks. so i dicked around with that friggin offset template for hours trying to get it perfect. so then last week i ordered the cf wheels from readyheli. if i had known that i just needed to space the links out properly, and not get the offset perfect i could have saved myself some grief and one hell of a headache. buy anywho the cf arms are on now, and seem to work good.

[Pinecone]

The CNC front arms can be used with or without offset.

[mjdee14]

i just looked, and yes my bellcranks are set up with the offset. it's a pisser, because i just realized that when i was first building and setting up this 550, i really agonized over getting the offset perfect on the servo wheel. nowhere in the manual did it say that the wheels didn't need the offset if you have the offset on the bellcranks. so i dicked around with that friggin offset template for hours trying to get it perfect. so then last week i ordered the cf wheels from readyheli. if i had known that i just needed to space the links out properly, and not get the offset perfect i could have saved myself some grief and one hell of a headache. buy anywho the cf arms are on now, and seem to work good.

isn't the idea to have offset on both the servo and the arm? because if not the rods will have different travel as they go past the center position.


The way I understand it is if this was a 90deg swash you wouln't need the offset. and the elevator doesn't need it because it pretty much travels straight up and down and can't deviate,

Am I using the correct thinking here?

[lightbulbjim]

Eh? The CNC aileron arms are designed for no offset. The only reason there is four holes there is so that they only need to make one part type for both aileron arms (cuts down on production cost).

On the stock plastic aileron arms, there is a molded line pointing you to which holes to use for each side. For some reason they designed the arms so that a line drawn straight through the ball holes doesn't pass through the pivot. Not sure why they did it but it means you need the matching offset on the servo arms.

If on the CNC arms you just use the holes that the slightly hollowed-out patterns "point" to then you get the straight setup with no offset (thus requiring no offset on the servo arm holes). The reason you end up with different holes left and right is because the angle from the swash link to the servo output shaft is different for each aileron servo.

If you look at say the Rotorworkz frame, the angle is the same on both sides.

[istandalone]

my balls came preinstalled by gaui in the cnc bellcranks, with the offset. i'm going to trust that gaui knew what they were doing on that. plus, after installing the cf wheels, i popped off one link at a time to check for binding, there is none. i guess it can be ran either way, but i'm leaving well enough alone for once lol.

[Pinecone]

If the bellcrank has offset, the servo horn needs the SAME offset.

If the bellcrank is set up straight, then the servo horn needs to be be setup straight. Basically both ends have to match.

[bpd964]

also, i ordered both sets not knowing which i'd need. if anyone needs the offset ones, let me know, i'll give them to whomever needs them, and whoever asks me first assuming i can get them in a regular sized postage envolope without going over the weight limit.

Thank you very much.. They arrived yesterday..

[istandalone]

no problem! glad i could help. pinecone, not trying to argue, just trying to understand. my cnc bellcranks came with the balls installed offset. i used the cf servo wheels from readyheli with no offset, which readyheli says to use with the cnc bellcranks. if i take off one end of either link and move the servo through it's travel, there is no binding whatsoever, and it's like that with all 8 ends. i can pop off each end one at a time and move the servos through their travel and the link will stay perfectly lined up with ball. i'm just starting to wonder if it really matters. it doesn't seem to in my case, but why would mine be different.

[Pinecone]

The problem is, with both links attached there will be binding. Because the distance from ball to ball changes for each link as the servo moves.

Try this. Disconnect one link. Move the servo to full travel one direction. Hold the disconnected link against the ball it would connect to. See any difference?

Just move one ball on the CNC arm to the other hole and you will now have both ends without offset.

[istandalone]

Try this. Disconnect one link. Move the servo to full travel one direction. Hold the disconnected link against the ball it would connect to. See any difference?


that's exactly what i'm doing. popping off one link at a time, and no binding. if i experience early servo failure, then i'll probly set it up the "right" way but for now all is fine.

[Pinecone]

NO. You will not get any binding with only one link installed.

What I am saying is if you set your heli up at center stick, if you pop offone link and hold if up to the balls where it should fit, the holes nad balls are lined up. Now move the servo full travel one way or the other and hold the link up to the balls. It won't fit properly. THAT is the source of the binding.

With offset on one end and not the other, as the servo moves, the spacing between the balls changes.

[istandalone]

NO. what you are explaining is what i'm doing. i've tried it every combo of ways. no binding. no need to yell, hoss. and considering all of the hours i've spent getting this as close to perfect as i can, i'm leaving it they way it is until i see reason to change, ie servo failure. my head and swash move perfectly and the servos center dead on. leaving well enough alone for once in my life. besides, i'm not a good enough pilot to even notice the difference, i don't think.