Macommy

You guys use Bell cranks so please give advice. I have an electric .40 size aerobatic plane I want to use a Bell crank on.
It is tail heavy so I want to take the two elevator servos out of the tail and mount one in front of the rudder servo in the center of the fuse.

The servos are butted back to back with one on each side several inches in front of the horizontal stab. A control rod leaves each going to an elevator.

This is the plane, http://www.3dhobbyshop.com/detail.aspx?ID=2328

This is what I want to copy or to purchase something similar

http://www.centralhobbies.com/contro.../Bellcrnk.html

World models has this on their web site,

http://www.theworldmodels.com/para/p...id=26&subcat=0
I don't know where to buy it or if it is light enough and good quality and the width etc.

I've been told I would do better to copy this design or find something like it. The MK model has short arms and other problems.

The width of my fuse at that point goes from 1 & 1/2" to 1 & 3/4" at the wider point.

Basicly one carbon control rod would go from the servo to the center arm half way back and the lite weight bell crank would take this to control horns on both side of the fuse then back to the elevators. If someone has a better idea then I'll listen to that also. Thanks for the time.

John

vbortone

My Feedback: (2)

Consider this option: http://www.centralhobbies.com/contro...age/deps1.html

Good luck,

Vicente "Vince" Bortone

tggilkey

Good advice from Vince. The DEPS from central will do the most for lightening up the back half of the plane. I replaced the MK bellcrank system from a Temptation with the DEPS and was able to remove significant weight from the nose. Without examining the details of the two types I think the maintenance is lower for deps: the bellcrank will have an internal (in the rear) point of wear as well as two additional external points compared to DEPS. I have used it on three pattern planes and it will go in the fourth this winter. I like it.

Good luck!
Tom

nedim

My Feedback: (1)

Check these!


[link=http://www.hobbycity.com/hobbycity/store/uh_listCategoriesAndProducts.asp?idCategory=122&curPage=3&v=&sortlist=]hobbycity[/link]

They are similar with MK belcrank that Central sells but lot more cheaper. Comes in 3 sizes, 70, 80 and 90 mm wide.

nedim

My Feedback: (1)

It seems like the link doesn't work.

Go to hobby city.com (one word, do not put blank), it is under parts & accesories, horn/hinge/clevis page 3.

Sorry, I couldn't make the link work.

Macommy

Will the DEPS flex enough for the movement of my control horn? This plane is smaller than a pattern plane but it adds 3D throws. I don't know if that's more up and down flex or not. Thanks for the help.

vbortone

My Feedback: (2)

I think is very dificult to set up a plane to do both 3D and pattern. I suggest that you read the information in this link:

http://www.centralhobbies.com/instructional/instrct.htm

VB

Macommy

I don't want to set it up for pattern and 3D. It's a 3D plane not a pattern plane. My concern is that because it's a 3D plane the horn will move up and down too much for the flex of the carbon rod. It's only a .40 size plane though which means it's less than a larger 3d model.

vbortone

My Feedback: (2)

The carbon rod flex. However, it won't work if you want more than around 20 degrees surface movement. If you want true 3D throws you won't be able to use this option. Probably pull-pull cables will work for you.

VB

Macommy

I'm trying to understand why this won't work. This is a 3D plane, but it's smaller than a pattern plane by a good bit. It will have more flex from 3D throws, but less bc of it being smaller. How far from the fuse can the rod safely travel and how much up and down flex can there safely be.

vbortone

My Feedback: (2)

What are you planing to fly with this plane? If you want to fly 3D you will need elevator throws over 40 degrees. I believe that the carbon rod won't work if you need that much. You could try and let us know how much you could get.

Good luck,

Vicente "Vince" Bortone

Macommy

A link to the plane is at the beginning. The rod would need to bend enough to accommodate a difference of 1/2 an inch. If I have eight inches outside the fuse would it not flex enough to accommodate this. I'm not trying to be a pain. I was just really hoping to use this, but not wanting to waste time and money if it won't work. Thanks for the time and info.
John

vbortone

My Feedback: (2)

John,

If you don't use the plane for full 3D you could use the carbon rod. I think you could get around 20 degrees maximum that should be sufficient. If you want to do 3 D you will need to set the servos in the fuselage.

VB

insalacosm

My Feedback: (1)

Macommy - I was debating the same thing for a 60 sized plane and chose to use a bellcrank. While it never failed after a couple hundred flights, I was planning to switch it over to a DEPS setup until the plane met its demise due to bad timing of an engine flame out. My bellcrank was about 1/8" too small so it would not rotate freely eventhough I had plywood plates trying to square everything up and I had play in one side. There are a lot of linkages with a bell crank setup and there is very little tolerance for installation error, so my opinion is that it should only be used if another solution doesn't work.
Steve

tggilkey

Macommy

It's my opinion that the carbon rod would flex the 1/2 inch you need without endangering the rod. The rod is of a fairly small diameter - .070 I think, so it will bend some without breaking. If you are lucky enough to live close to a LHS that carries the CST display you will find CF rods there and you can get a feel for the flexover that 8 inch distance you mention. I'll have to measure my 2m pattern plane and see how much I have sticking out of the fuselage and maybe disconnect one of the clevises and see how a half inch deviation from it's natural position feels. I'll try to remember to do that this weekend and let you know.

Thanks,
Tom

BaldEagel

If you only want to set it up for 3D and you want the lightest rear end then close loop link both elevators, either to one or two servo's in the canopy area, its the lightest most positive link you can get.

Mike

Macommy

Baldeagel'

Would you elaborate on your setup. I'm intrigued, but what are the black wires for. I'm considering doing pull pull also. I might use one servo with ball links on both side of the arm with one small bolt through the arm and both links.

Thanks for all the suggestions. I'm still debating and these real world comments are helping.