Help with CNC bellcranks

[Mark A Smith]

Hello to all,new here to this forum but have been "playing" with Rc helis since about 1981:P.Recently got a 550 and ordered the CNC bellcranks.I can see that the elevator B/C is now 90deg compared to the plastic version.The ail and pitch cranks also have the 2 hole on each side arrangment.My question is,what holes do you install the balls onto ?? :confused: Seems as though I cannot get equal length rods no matter what I do?? According to the gaui manual,if the CNC bellcranks are used,You do not have to set up the offset servo wheel arrangment.You can use 180 deg servo arms. Any help with this would be great
Thanks
Mark Smith

[Mikej]

Here is my set up
Left side bottom front, top back (first picture)
Right side top fron, bottom back (second picture)

[Vinger]

Hi I used the Finless trick of using the other bellcrank as a template on the servo wheel. You have to use the CNC ones as a template if you want to use them. The CNC and plastic belcranks have differrent geometry, you still use the offset holes as these allow for a linear movement of the swashplate together with the straight elevator bellcrank.

[Happy|Harry]

the gaui cnc and plastic levers have exactly the same geometry :confused:

mark just do as mike suggests and go with the straight links and get rid of the offset all together, i think most everyone with a hurricane uses this method :)

phil

[Pinecone]

I use straight arms also.

Both links still need to be the same length, but the servo arm will not be exactly 90 degrees. If the link lengths are different, you will get binding as the servo moves, and may pop a link off.

You do have a package of Raptor links, don't you? The Gaui ones are so short that a lot of the links have very few threads. YOu can use Raptor links on both ends or only one end for the extra length.

[Mikej]

I use straight arms also.

Both links still need to be the same length, but the servo arm will not be exactly 90 degrees. If the link lengths are different, you will get binding as the servo moves, and may pop a link off.

You do have a package of Raptor links, don't you? The Gaui ones are so short that a lot of the links have very few threads. YOu can use Raptor links on both ends or only one end for the extra length.

Good point Terry - if you look at the pics posted you will see that the links on either end of the rod are different, one Gaui one Raptor :thumbup:

[Vinger]

Hi guys/girls,

If you take the CNC (Gaui) bellcranks and put them over the standard plastic ones, you wiil see that the offset holes are not the same. Gaui uses the offset so that the roll cyclic servos (front pair) can transfer the same vertical movement to the swashplate as the elevator servo. This is because they have to work around an angle greater than 90 deg, where the elevator works through 90 deg. The CNC set should be used together and not be mixed with the plastic ones. The roll cyclic servos need the offset to be less when you use the CNC elevator bellcrank.

It is simple to check, if you only change the elevator to CNC (straight) bellcrank and then measure your swashplate without altering the throws and you will see that it does not move correctly (I use a swash leveller). If you now change the front two bellcranks to CNC (with offset) the swash moves correctly once again, provided you had it setup correctly to start with. It is simple trigometry if you want to do the maths.

[mjdee14]

Is this why it is recommended to reduce the pitch % on the swash....?

to compensate for the diference?

[Happy|Harry]

i'm sorry vinger but i was comparing the plastic arms to the microheli cnc versions and these are exactly the same, i now see you were comparing the plastic and gaui cnc versions and you are correct that there are slight differences in the geometry, but if you set them all up as straight surely everything is correct?

phil