RCU Review: Du-Bro’s Heavy Duty Pull-Pull System & Full Dual Servo Arms

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    Contributed by: Jerry Festa | Published: January 2014 | Views: 10138 | email icon Email this Article | PDFpdf icon
    HPI Blitz RTR Review

    Review by: Jerry Festa (tailskid)

    Du-Bro Products, Inc
    P.O. Box 815
    480 Bonner Rd
    Wauconda, IL 60084
    Phone: 800-848-9411
    Fax: (847) 526-1604

    • Installs quickly
    • High quality hardware
    • SAE dimensions
    • Sufficient wire for majority of Giant Scale airplanes.
    • Directions consist of a diagram and may be lacking for a first timer.



    Du-Bro?s Heavy Duty Pull-Pull System and Full Dual Servo Arms

    Du-Bro has introduced a line of accessories for Giant Scale planes including a complete pull-pull package. The only item missing will be a dual servo arm (which is also available) matched to your particular servo. Both the pull-pull system and servo arm are made with high quality materials and can be used on most any aircraft.



    Du-Bro?s Heavy Duty Pull-Pull System and Full Dual Servo Arms
    Included in Part# 883 was the following:

    4? 8-32 all threaded rod
    Locking washers
    Locking cones and (2) nuts
    Nylon control horns and matching nylon clevis
    (4) 2-56 threaded Rigging Couplers
    (4) Locking keepers with cotter pins and 4 crimps.
    (5) 4? Heat Shrinking tubing
    (1) Roll of15? nylon covered steel wire


    First Look

    A lot of parts come out of that little package! To install a Pull-Pull system on my SlipStream RV-8 everything was included with the exception of the dual servo arm and I?m sure they would have included that if Du-Bro knew what brand servo was being used. Because I have a JR servo mounted for the rudder, Du-Bro was gracious enough to also supply their newest ?Full Dual Servo Arm? (P/N #3345) for JR servos. With all the parts accounted for, assembly was started.


    For those who have never installed a Pull-Pull system a quick overview may be desired. There are three components that make up a Pull-Pull system: Rudder assembly; metal cables; and Full Dual Servo Arm. The rudder assembly must have two control horns (one horn on each side). The cables must then connect the rudder to the third part, the dual servo arm.


    It is best to assemble as much as possible off the aircraft as possible, but eventually your last connections will have to be done on or in the airplane itself. Many like to start installing this type of system at the rudder, others start by connecting the cables to the servo arm. Whichever is easiest for you ? go for it! For our purposes here, the rudder gets the first attention.

    A 5/32? hole was drilled in the rudder, in line with the fuselage slots for the cables. One side of the 8-32 rod was completely fitted and that assembly was inserted into the rudder followed by the locking washer, tapered cone, locking nut and control horn. Then the Rigging Coupler was threaded into the clevis about 5 turns and the clevis attached to the control horn with locking pins and cotter pins.

    With this arrangement the rudder is almost done! The missing piece of the puzzle is now the nylon coated cable. By measuring about 12? longer than the distance from the horn to the servo arm, the cable was cut with some wire cutters. The extra cable will come in handy when attaching to the rigging coupler.

    Possibly the most challenging part of this entire procedure is attaching the cable to the rigging coupler and after one or two experiences turns into a non-event! By simply threading the cable through the rigging coupler?s hole you are almost 1/4th done!

    Leave at least 2? past the rigging coupler and bend the cable back over itself. Slide one of those brass fittings on the long piece of cable up to the rigging coupler. Take that ?excess 2+? of cable? and slide it through the brass fitting (you are now ½ done).

    With your nimble fingers bend the shorter piece of cable sticking out from the brass tubing and loop it around and through the brass fitting again! You are now 3/4th done.

    Pull that looped cable tight and with those pliers crunch (or as they say in the south ?Mash?) the brass tubing and you are done. Now that was easy wasn?t it?

    You only have to do this three more times. The other side of the rudder was done the same way. Now you have a rudder that is complete with two strands of cable going nowhere.

    Next task will be to fish the cables through the fuselage to the rudder servo which should be mounted in the center of the fuselage. There are a couple of ways of doing this: thread the cable into the fuselage and reach in with those tiny fingers and pull the cable forward; run a piece of Nyrod through the fuse and slide the cable inside that; make a ?U? shaped tool out of some wire and reach in and snag the wire and pull it forward. The choice is yours.

    The last major part is to connect the cables to the rudder servo arm. Remove the arm from the servo (if mounted) and attach the 4-40 swivel ball link and threaded rigging coupler. Install this assembly to each side of the dual servo arm and reattach it to the rudder servo.

    Lock the rudder in neutral by clamping the vertical stabilizer and runner together.

    This is a good time to turn on your radio and center the rudder servo. Make certain the cables running from the rudder are not tangled together or wrapped around a servo extension. Take each cable and loop it through the rigging couplers like you did on the rudder, pulling the cable tight, but in all honesty when finished the cable will probably be somewhat lose but that?s O.K. for now. Finish by crimping the brass connectors.

    Probably one of the cables are not tight ? maybe both, so remove the 4-40 swivel ball link from the Dual Servo Arm and hold the rigging connector with pliers, and screw the ball link clockwise a couple of turns. Re-install the servo horn on the servo arm and see if the cable is tight, if not, repeat the process until the cable is firm but not excessively tight ? after all these two cable will be pulling on your rudder servo?s drive train 100% of the time!

    So you are done with installing a Pull-Pull system on your plane. There won?t be any flutter because both sides of the rudder are under tension all the time ? giving you precise control on the one flying surface that doesn?t stall!

    Photo Shoot
    Heavy Duty Dual Pull-Pull System .91 & up $20.79
    Long Dual Servo Arms $9.99
    Full Dual Servo Arm $9.99
    Heavy Duty Clevis Horn System
    4-40 Pull-Pull System $10.08
    Rigging Couplers


    In over 40+ years, I have never had a Du-Bro product fail in its job. The quality of both the Dual Servo Arm and the Pull-Pull system lives up to their high standard. The use of these products relieves my worry about a cheap part failure and the result costing me of a giant scale aircraft. This product does as is advertised and does it well.

    Dealer Contact information

    Du-Bro Products, Inc
    P.O. Box 815
    480 Bonner Rd
    Wauconda, IL 60084
    Phone: 800-848-9411
    Fax: (847) 526-1604



    Comments on RCU Review: Du-Bro’s Heavy Duty Pull-Pull System & Full Dual Servo Arms

    Posted by: evarnad on 01/28/2014
    I see people cross the cables is there any pros or cons in doing this. Thanks, Wayne
    Posted by: tailskid on 01/28/2014
    If they cross, I would think they would wear eventually, but like you, I too see those rudder cables crossed.
    Posted by: cymaz on 02/02/2014
    You cross the wires to get the cables to exit the fuselage at a different point, usually a bit further down toward the tail.
    Page: 1
    The comments, observations and conclusions made in this review are solely with respect to the particular item the editor reviewed and may not apply generally to similar products by the manufacturer. We cannot be responsible for any manufacturer defects in workmanship or other deficiencies in products like the one featured in the review.

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