Vector 40 Horn and bellcrank hole locations

[kevin king]

I try not to post questions that have been answered already but i cant find them. 🧐🤯
I need to know which pushrod bellcrank hole to use on a vector 40 kit powered by an OS LA46. I also need to know which flap horn hole to use for the pushrod from the bellcrank, and the flap horn hole to use for the pushrod to elevator, and the elevator hole to use as well. Its a stock 4" bellcrank and it has 3 holes. The stock flap horn has 3 holes, and the stock elevator  horn has 3 holes. Thanks

[Craig Beswick]

Kevin,
on my Vector ARF I got it all so horribly wrong. I crashed it and rebuilt it and set the controls up this way.

Pushrod in the hole furthest from the pivot post in the bellcrank.
Bellcrank pushrod in the top hole of the flap horn. Elevator pushrod in the middle hole of the flap horn and then in the middle hole of the elevator horn. Or, whichever elevator hole is closest to a 1 to 1 with the flap horn.

I have a BG LA46 in mine. With these changes it flew the way everybody talked about how it should fly! I had the controls way to slow!

Good luck
Craig

[Dave Hull]

I recently redid the bellcrank installation in a Vector 40. The leadout failed at the bellcrank--fortunately during a ground check--so there was something left to repair.

The Brodak plans (as drawn by Curt Contrata, and presumably faithful to Randy's design) show the pushrod in the bellcrank center hole, which measures out at a radius of 11/16". This is paired with a flap horn radius of 1-1/4".

If you have the assembly booklet from the Brodak kit, you will see a picture of the flap pushrod in the outer hole of the bellcrank. If you like quicker controls, that may be an option. I haven't got much flight time on mine since the leadout replacement exercise, but I like the control feel using the center hole so far. It feels pretty deliberate, and that makes the rounds smooth.

Note that another "control ratio" that should be considered is the line spacing at the bellcrank vs. the line spacing at your handle. Assuming you have the standard 4" bellcrank, that might be a good place to set your handle to begin with. Unless you have already found a ratio that works for you on similar planes. So you can always "speed up" the control feel by widening your handle spacing, or vice versa. But you may want to watch that your control surfaces do not hit the travel limit as hinged by a fast bellcrank/flap horn ratio.

It also might be worth mentioning that moving the pushrods out at both ends while maintaining the same ratios, causes the forces in the pushrod to go down. That means the ball joints, clevises, etc. see less load and the wear on the moving surfaces goes down. Also, if you had just a little bit of play in each joint, the larger the radius on the control setup, the less lash there will be at the control surface. In other words, without fitting anything tighter or holding closer tolerances, you get less free play in the control surfaces.

The plans show the flap to elevator ratio is 1:1. That means the radius to the holes on both ends of the elevator pushrod should be the same. Use the farthest one out that you can. On the plans (assuming the hardware is the same as the plans) that is a radius of 3/4", which was limited by the elevator horn. If your horns differ, just be sure that the connections at the flap horn do not interfere with each other over the entire control range. No binding or grinding....

Good luck with yours,

Dave

[Dave Harmon]

The Brodak plans (as drawn by Curt Contrata, and presumably faithful to Randy's design) show the pushrod in the bellcrank center hole, which measures out at a radius of 11/16". This is paired with a flap horn radius of 1-1/4".
I like the control feel using the center hole so far. It feels pretty deliberate, and that makes the rounds smooth.
So you can always "speed up" the control feel by widening your handle spacing, or vice versa. But you may want to watch that your control surfaces do not hit the travel limit as hinged by a fast bellcrank/flap horn ratio.

Dave

My Vector 40 ARF is set up this way.
Some years ago I had a conversation with Randy regarding the outer bellcrank hole as shown on the assy booklet that came with the later ARF airplanes.
It was pretty plain that the booklet did not match what was in the box which was the subject of the phone call.
Randy insisted that the middle hole on the bellcrank should connect to the top flap coupler hole and the elevator pushrod MUST be connected to the middle hole on flap and elevator couplers for 1:1 ratio.
That's what I did and the airplane(s) fly very well with the CG where Randy recommends.
This is nothing really new in the control line world but later I had a different problem with that ARF bellcrank.

It turned out that the supplied bellcrank has a tremendous amount of wobble.
This can be seen through the slider slot if the leadouts are tied together with a piece of soft wire through the ferrules/thimbles to hold the leadouts steady.
Then move the elevator or flap and watch the bellcrank flop back and forth which causes a lot of slop in the control circuit.

On the next V40 ARF I removed the original bellcrank with huge slop and put in a nice phenolic bellcrank from OKIE AIR using the same measurements that Randy recommends.
I added some additional anti-wobble pieces to the bellcrank and the result was no more slop even though I used good after market hardware on both pushrods.

Also....with the CG and slider adjusted properly....the front leadout drags against a couple of ribs which can't be doing anything good so I inserted a long drill on the slider slot and drilled a bunch of holes in the rib and then knocked out the piece(s) that were dragging on the lead out.

[Ken Culbertson]

The plane in my Avatar is nearly identical to a Vector in all respects except tip and rudder shape. It was a product of the 70's and weighed 34 ounces.  It was set up 1:1 middle hole to top hole on a Veco 3" bellcrank and flap to elevator horn middle to middle.  I flew it on a large EZ-Just which I think was a 5" spacing.  Fast forward to the Vector 40 ARF I flew all of last year.  It was 46 ounces.  Also set up 1:1 but it did not corner anywhere near as well as the 70's plane.  It was not mine so I couldn't change the ratios, but I think it would have performed better at 2:3.  If you can do it, I would use an adjustable elevator horn and set it initially to 1:1 with plenty of up adjustment room.

Ken

[kevin king]

Thank you for the information everyone. The comment on wobble at the bellcrank also was interesting as i noticed this too. With the bellcrank bushing flat on the table I measured 3/16 movement at the bellcrank arms tip. Thought i did a poor assembly job so i grabbed a new bellcrank out of my Strega kit. It had the same wobble. I think this is a problem but to what degree? That I dont know.

[Dave Harmon]

Thank you for the information everyone. The comment on wobble at the bellcrank also was interesting as i noticed this too. With the bellcrank bushing flat on the table I measured 3/16 movement at the bellcrank arms tip. Thought i did a poor assembly job so i grabbed a new bellcrank out of my Strega kit. It had the same wobble. I think this is a problem but to what degree? That I dont know.

You can check it another way too.....
Tape or block the elevator in neutral.
Then holding tension on both leadouts....move them back and forth and see how much slop you have.
Assuming both pushrods are tight on the bellcrank and both wing and flap couplers....there should be very little slop.
When I changed to the phenolic bellcrank from OAKIE AIR....almost all slop was gone due to almost no wobble.

[kevin king]

Thanks Dave. I was hoping to get this plane done for the start of the flying season. The fastest replacement i can get is a Sig 4" bell crank, And i am not sure how good they are or if they have the same throws. Ordering an Oakie Air could take months because i am in Canada. I do have a PSP bell crank but i would prefer not to use it on a mid size airplane. Will see if i can modify the Brodak bell crank first to see if i can take some slop out of it.
Kevin

[Dave Harmon]

Thanks Dave. I was hoping to get this plane done for the start of the flying season. The fastest replacement i can get is a Sig 4" bell crank, And i am not sure how good they are or if they have the same throws. Ordering an Oakie Air could take months because i am in Canada. I do have a PSP bell crank but i would prefer not to use it on a mid size airplane. Will see if i can modify the Brodak bell crank first to see if i can take some slop out of it.
Kevin

The SIG B/C might be the same as the BRODAK.
You can try some large nylon washers pressing on top and bottom of the B/C to help stabilize it some....anything would be better than it is.
I think you said you have the Vector ARF.....if so remove the E clips on the shaft and remove the plastic tube spacers on the shaft. Then put in some nylon washers with wheel collars holding the washers against top and bottom of the B/C.
In my case because I used a different B/C, I used an 1/8" shaft and tossed the really soft original shaft.
I am doing it this way in the future too even though it is a bit more hassle.

[Dave Hull]

Guys,

On the Brodak BB-389 bellcrank, and probably other similar units, you can reduce the wobble by about half with a simple upgrade. I did it on the last repair job and was happy with the result.

First, know that the parts are injection molded, and putting a draft angle in the mold helps to eject the parts. Therefore, a round hole is actually a tapered cone, and that is before you get any shrinkage distortion. On the parts I measured, there was about .0015" size variation in the center bushing. On the crank it was much larger due to the shrinkage pull--up to about .005" or so, but elliptical due to the pull in the direction of the arms.

The easy improvement is to drill (or ream, if you have a reamer) the hole to size "K". Then, cut a short piece of 9/32" K&S brass tubing. Be sure one end is clean and square, but don't worry about the other end or the length too much yet. Press it into the bellcrank so that the good end of the tubing bottoms out flush. Now, take a fine file and trim down the other end of the brass sleeve flush with the 'crank. This gets rid of the taper on one of the two pieces and cuts the wobble significantly. The Delrin-on-brass friction is low, so the other functionality is still very good. You are just barely cleaning up the hole when you drill or ream it to a size K, so you haven't reduced the overall strength much.

I did not have a lathe to make up a new center bushing, or I likely would have. Still, it was much better and took all of 5 minutes to modify.

Dave

[Dave Harmon]

Guys,

On the Brodak BB-389 bellcrank, and probably other similar units, you can reduce the wobble by about half with a simple upgrade. I did it on the last repair job and was happy with the result.

First, know that the parts are injection molded, and putting a draft angle in the mold helps to eject the parts. Therefore, a round hole is actually a tapered cone, and that is before you get any shrinkage distortion. On the parts I measured, there was about .0015" size variation in the center bushing. On the crank it was much larger due to the shrinkage pull--up to about .005" or so, but elliptical due to the pull in the direction of the arms.

The easy improvement is to drill (or ream, if you have a reamer) the hole to size "K". Then, cut a short piece of 9/32" K&S brass tubing. Be sure one end is clean and square, but don't worry about the other end or the length too much yet. Press it into the bellcrank so that the good end of the tubing bottoms out flush. Now, take a fine file and trim down the other end of the brass sleeve flush with the 'crank. This gets rid of the taper on one of the two pieces and cuts the wobble significantly. The Delrin-on-brass friction is low, so the other functionality is still very good. You are just barely cleaning up the hole when you drill or ream it to a size K, so you haven't reduced the overall strength much.

I did not have a lathe to make up a new center bushing, or I likely would have. Still, it was much better and took all of 5 minutes to modify.

Dave

Good idea Dave. I’m going to try that next time instead of the phenolic Bellcrank.
At least I won’t have to cut the lead outs and do the whole thing all over again.