mikedsilva

hi

hope this is the right forum in which to ask this question:

What sort of cable can i use to fabricate my own pull-pull setup?

Background: i have an excelleron 90 which came with its own cable and fittings. One of the cables broke... i have some fishing trace wire which i used to make a bracing on the tail feathers of another plane a while ago. The cable is rated at 18lbs and is plastic coated. In fact, when compared with the stuff that came with the original kit, it looks almost identical!

I plan to use some small diameter brass tubing as the crimping material.

Does this all sound sufficient?
thanks
MIke

dmcmike

My Feedback: (14)

A lot of Fishing line will stretch, a no-no for pull-pull cable. Check out a fisihing line by berkley called 'Spider-wire'. It doesn't strectch. It's also smaller in diameter, allowing you to use a higher lb test rating for the same size. The brass tubing is ok, it's what i've used in the past, just make sure you run a loop around the tube, such that you have 3 pieces of line going through it prior to crimping. The other alternative is to use a braided plastic coated metal cable. I think Dubro has some available. Don't know if any of this is available in Australia. hmmm. maybe the spiderwire is! I just spied it online, available in New Zealand.

mcmike

Jimmbbo

You may be talking about the same stuff, but WalMart (as well as any good sports shop) carrys a small diameter nylon coated seven stranded wire fishing leader material called, clevely enough, "Sevenstrand" that comes in several different strengths, and has sleeves made specifically for crimping the wire... pretty cheap, too... Bought some 27# and 60# for doing pull pull experimentation and for tail bracing...

Cheers!

camdyson

Mike,

Fishing trace is fine - been using it for years. 20lb is enough for most jobs, but there's plenty of choice. You're not likely to exceed 20lb on a .90 plane's rudder - no need to go beyond your servo's rating.

Cam

mikedsilva

thanks for the encouragement.
18 pounds works out to near 300 ounces, and my servo is a Hitec 645MG which i think has a rating of 100 ish... so i am sure the trace will be perfect.
however, i will re-do them since i didnt pass the cable back through the brass tube a second time... i guess that would reduce all possibilities of the cable sliding out!

however, i have a geometry problem; the cables hook up directly to the servo (using a coupling) and the elevator horns do not place the clevis right over the hinge gap (pivot point). So when neutral, the tension is fine, but when i deflect, i have some slack on one side...

The elevator horns consist of a threaded rod that runs through the elevator and a nylon connector threads onto the end of it. I hope that description makes sense. I need a nylon connector that has a longer arm so that the clevis pin sits over the hinge gap. Any ideas where i can buy longer ones?

mike

T_om

The wire or line going slack on the side with no tension will not hurt a thing.

As to the correct line to use, make sure you use a fishing line product called "Braided Spectra". The example given earlier of the brand name "SpiderWire" is braided spectra.

This line has practically zero stretch. If any slack appears, it is usually because the fuselage itself expanded or contracted due to temperature changes. It is good stuff. Be sure to us a drop of CA on knots as this line is slippery and difficult to tie without the knot slipping.

Tom