Pull-Pull Elevator on DP Ultimate - am I missing something
 

I recently had to re-hinge one side of the elevator on my DP Ultimate. When I was finishing up I realized that it appears the only way you can adjust the elevator throws on each side is with the holes on the control horns. For those not familiar, the DP Ultimate uses a single servo with dual wires going to the separate elevator halves. Since i was not the builder, I had not seen this setup before. Am I correct on the only available adjustment, or I am missing something.

Pull-Pull Elevator on DP Ultimate - am I missing something
 

My single servo pull pull system has a short threaded rod that the control horn and locking nut screw on one side and this rod has a hole drilled through the other end and the wire loops through the hole. This allows adjustment (at the control surface)like you would normally have with a solid push rod system.

Hope this helps :)

Pull-Pull Elevator on DP Ultimate - am I missing something
 

Use Dubro 4-40 rigging couplers

http://www2.towerhobbies.com/cgi-bin...?&I=LXE074&P=0

And Sullivan 4-40 clevises

http://www2.towerhobbies.com/cgi-bin...?&I=LXFV18&P=7

Pull-Pull Elevator on DP Ultimate - am I missing something
 

I hate to disagree with you fellows; but all you are doing is adjusting the cable tension. You are not adjusting the throw at all. The only way you can adjust the throw is by moving your cable attachment in or out on the horn (closer or farther away from hinge line). Tell me were I am wrong.

Pull-Pull Elevator on DP Ultimate - am I missing something
 

I'm guessing you've got the big one....but if it's anything like the 40 size, and you use the stock hardware...then yes, you have to pretty much redo the entire setup to change the throw....ie. lower on the horn at the elevator or further out on the horn at the servo. Since I went ahead with the stock stuff I just set it up for Big 3D throws and then tuned it down thru the TX for normal flight modes.

Pull-Pull Elevator on DP Ultimate - am I missing something
 

I don't understand. Control throws can only be changed via servo travel from the tx or by changing the linkage ratio.

It doesn't seem like you have a problem unless you want the travel on the left and right side to be different. In this case, you're right. To change the travel from one side relative to the other, you have to change the linkage (holes in the horn).

Pull-Pull Elevator on DP Ultimate - am I missing something
 

I am talking about adjusting the throw so that the right and left side have the same throw. You are correct. the general travel is done at the servo or were you connect to the horn. But on the DP, using only one servo and two sets of pull-pull wires if the two sides are not exactly equal all you can do is change the hole you use on one side or the other. When I reattached the left side elevator it was off a bit from the other side. In order to make both sides travel identical the right side is in last (4th) hole, the left side is on the 3rd hole. Now an MK post type horn would be the best way to solve this problem with this type setup. I love the elevator pull-pull setup. It is very crisp and slop free, but I think the single servo setup is a weakness.

Pull pull
 

It sounds like the control horns on one side has been over tightened and compressed the wood a bit more. If this is the case the hole spacing on each elevator half will be slightly off rendering different throws. Sometimes you might have to add an extra hole to get everything matched up. Tom

Any pic's?
 

:p

Well I worked on the pull pull today.
 

Its a good idea , IMO to have 2 people do this step.
I was working with my buddy, Paul (who is doing the review for this plane for RCU) and it was so much easyer to work at this step together.

But I can see were this can be a bear . :D

Pull-Pull Elevator on DP Ultimate - am I missing something
 

you're right man. that only adjusts TENSION on the cable-not the throw geometry. Gotta go outboard on the horn, if no other adjustment from the transmitter is available. I wouldn't try going TOWARD the controll surface horn-might cause flutter.

DP Ultimate
 

Now I could be very wrong, but I have had two of these planes and still have one. If you only shorten say the top cable to raise the elevator half all you will do is increase the cable tension but if you LOOSEN the bottom cable at the same time the elevator half will raise and the tension will remain the same since it is the opposite cable that it is pulling against. That is how I adjusted both of mine and it worked very well. Try it. You will see.

Pull-Pull Elevator on DP Ultimate - am I missing something
 

Robo, yes, but if you have different tension in the upper and lower cable you are not really changing the throw. You are just allowing slop in the looser cable which gives a false since of changing throw. It's kind of a technical point. And what you say probably works. But from a purely technical point and the "I know I did it" point of view, I think it's a compromise.

I have given this problem a geat deal of thought and come to the conclusion that a single servo, split elevator, pull-pull is not the best system for the simple point that the hinge line on both sides must be exactly on plane for the throws to be identical. When I re-hinged, it threw the two sides off.

Pull-Pull
 

Not to belabor the point but the cables are pulling against each other not against the elevator half. The hingeline of the elevator is the pivot point. The tension on the cables is going to even out when the elevator half seeks its resting point. I'm probably not describing it properly but if not over tensioned the cables cannot have a different tension. The elevator is going to center on an equal tension between the two cables.

.
 

robotech is correct....i have done 3 of em and had no probs adjusting. only prob ya may have is if you run out of threads for the clevis and then you have to rewire it. :)

Pull-Pull Elevator on DP Ultimate - am I missing something
 

Tinman, I think we are all trying to discuss something hard to explain clearly. I am going to try your method when I get a chance.

One thing I failed to also mention is that the location of the control horn in this type of setup is also critical. If they are not identical in their location, fore and aft on each side, the throws will be different.