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carbon tube as push rod

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Old 03-10-2016, 07:13 PM
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Stick 40
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Default carbon tube as push rod

I am putting together a hanger 9 PT-17, it was about 90% done when I bought it. its a good sized plane 71in. wing span and should go about 10 to 12 lbs.
the push rod tubes are already in and they only take the flex size . I would like to make it a little stiffer.

I see that 1/8 in. carbon fiber tube is the right size for the tube in the plane , and 2x56 thread seem to be the right thread size.

does anyone see a problem with using carbon fiber this way? the 1/8 in. carbon fiber tube will be the push/pull rod between the servo and the tail surfaces.

If this is possible I was thinking of hitting the threaded rods with thin CA to lock the 2x56 threaded rod into the carbon fiber tube.

thanks

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Old 03-11-2016, 03:15 AM
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Carbon fiber tubes work extremely well as pushrods. Stiff and light. Just make sure there are no bends in the push rod tubes to cause friction. Carbon tubes need a straight shot. JB Weld, available at any hardware store, is the standard for securing the metal into carbon fiber tubes. Make sure you clamp/secure the ends while its drying as the air pressure will try to push them back out (at least for the second end). Wrap the tube with masking tape before cutting it so it doesn't splinter. Also, do not breathe the dust. Nasty stuff. Lots of places sell the carbon tubes and special fittings for the ends or you can just JBWeld in some threaded rod.
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Old 03-11-2016, 03:47 PM
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the tubes in the plane are straight , there is almost no bend at all. yes the carbon tubes are stiff and that is why I want to go with them.

2x56 tread in very tight threading into the carbon tubes , don't think they will come out.
did not think of JB weld. I do like JB weld The masking tape was a good reminder.

I had to do something as the tubes end before coming out of the tail of the plane, so I could not use flex golden rod push/pull.
I am bouncing back and forth between a P-26 and the PT-17, lots of fun, till the wife makes me go out doors. Lol
thanks
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Old 03-11-2016, 05:29 PM
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Sure carbon is stiff and light but 1/8" will need to be supported at least in one spot around its middle. Larger diameter won't need supporting(1/4" x 1/16" wall)

Epoxying the steel ends is fine. So is slow ca. Glued mine with ca for years on 11 pound planes with 4 hp up front.

One thing to to keep in mind is that carbon expands differently than wood and the longer the pushrod, the larger the difference. You may experience weird trim changes during the summer. It's not a big deal, just beware; there's nothing wrong with the plane.
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Old 03-11-2016, 05:50 PM
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The tail end has 4 braces counting the ones at the servos, it will be fine.
I might not notice the change in trim with my flying. Lol
I was wondering the 2x56 threaded rode trys to screw into the carbon tube, would it be good to tap the carbon fiber tube with a tap?

thanks for the input.

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Old 03-12-2016, 06:55 AM
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Carbon shafts tend to have the ends split when any type of force is applied to the overall diameter of the shafts end. I found a half to one inch aluminum tube glued over the end stopped and splitting.

Central Hobbies has some nice carbon push rods and titanium threaded ends. I have used them for years strong as all get out.

https://www.centralhobbies.com/cat4....124&sub2cat=46

Dennis
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Old 03-12-2016, 05:51 PM
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Originally Posted by Stick 40 View Post
The tail end has 4 braces counting the ones at the servos, it will be fine.
I might not notice the change in trim with my flying. Lol
I was wondering the 2x56 threaded rode trys to screw into the carbon tube, would it be good to tap the carbon fiber tube with a tap?

thanks for the input.

sticks
Sure you can tap the carbon but the threads will not hold well. Make sure to epoxy or ca with slow or medium. I always wrap the carbon tube ends with carbon tow and wick thin ca on the fiber. I've never had a tube split and there is no sense tempting fate.

The 2-56 push rod end is strong enough for a 12 lb plane. Just don't expose too much steel. The carbon should be as long as necessary to keep the steel part no more than 1 or 2" long max.
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Old 03-13-2016, 07:46 AM
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[QUOTE=MTK;12188582]Sure you can tap the carbon but the threads will not hold well. Make sure to epoxy or ca with slow or medium. I always wrap the carbon tube ends with carbon tow and wick thin ca on the fiber. I've never had a tube split and there is no sense tempting fate.

The 2-56 push rod end is strong enough for a 12 lb plane. Just don't expose too much steel. The carbon should be as long as necessary to keep the steel part no more than 1 or 2" long max.

I like the idea of wrapping the end of the carbon tube with something , but what is " carbon tow"?
your talking about having the threaded end of the 2x56 put into the carbon rod no more than 1 to 2 inchs.? Seems like a lot, I would think 1 in. would be plenty.
yes I planed to glue the threaded rod into the carbon tube.

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Old 03-13-2016, 09:13 AM
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Carbon tow is each individual end of a fabric. Tow is similar to yarn except it is not twisted. It's referenced by the number of filament strands making it up....eg- 1K, 3K, 6K, etc., all refer to the number of filaments in the tow (1000, 3000, 6000, etc). Make sense?

Almost forgot....the 2-56 steel end should be as short as possible. One inch inside the carbon tube and one inch outside. Also the steel should be well aligned to the horn. 2-56 is barely .070" and has been known bend into a zig zag under heavy load if not kept short. Don't ask how I know....

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Old 03-13-2016, 09:21 AM
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Part#: CHMPRE35T2
PUSHROD ENDS TITANIUM 1/8 x 2-56
Description:

Package contains 4 ends.
2-56 Threaded ends for the 35 inch long Central Hobbies Carbon Fiber push rods. These are made for Central Hobbies brand 5/32 inch diameter pushrods and may not fit other brand rods. Outside diameter of barbed end is 0.071".



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Old 03-13-2016, 04:11 PM
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Originally Posted by MTK View Post
Carbon tow is each individual end of a fabric. Tow is similar to yarn except it is not twisted. It's referenced by the number of filament strands making it up....eg- 1K, 3K, 6K, etc., all refer to the number of filaments in the tow (1000, 3000, 6000, etc). Make sense?

Almost forgot....the 2-56 steel end should be as short as possible. One inch inside the carbon tube and one inch outside. Also the steel should be well aligned to the horn. 2-56 is barely .070" and has been known bend into a zig zag under heavy load if not kept short. Don't ask how I know....
I have some carbon fiber thread material, is this what you are talking about?

I measure the reg. goldburg 2x56 about that, but my 2x56 allen is .082.
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Old 03-13-2016, 04:13 PM
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Originally Posted by Propworn View Post




Part#: CHMPRE35T2
PUSHROD ENDS TITANIUM 1/8 x 2-56
Description:

Package contains 4 ends.
2-56 Threaded ends for the 35 inch long Central Hobbies Carbon Fiber push rods. These are made for Central Hobbies brand 5/32 inch diameter pushrods and may not fit other brand rods. Outside diameter of barbed end is 0.071".


I will look into these,
thanks
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Old 03-13-2016, 04:36 PM
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You can use the flat, or spread tow, for wrapping the ends of the tube. Except you only need a small fraction of the width you have making a pita to separate. The material wrapped in the smaller package is possibly better. Or just take one end from the tape you show. You don't need much... A 3"-4" length is enough to wrap the tube 5-6 times which is plenty.

The titanium ends from Central work fine. They get pricy tho including snh. Steel push rod stock is often in the scrap bin.....cheap and works as well
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Old 03-15-2016, 05:12 AM
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An alternative to wrapping the outside of the carbon pushrod with tow, is to slide an aluminum tube sleeve over
the outside of the pushrod. Find some aluminum tubing that is a good fit to the pushrod, cut it to about
3/4" and slide it in place. It will keep the c.f. from splitting when you thread in your 2-56 steel end.
Scuff the pushrod first and then glue the aluminum in place - thin CA works fine, it will work its
way between the c.f. and aluminum.
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Old 03-15-2016, 05:15 PM
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lots of good ideas.

thanks for the input, its great to get this kind of help. I have not worked with fiberglass and carbon fibber a lot before. But I have a better handle on it.
I feel I can go forward with this project, its a lot of fun being able to work with this stuff and learn.

This does not mean some one else can't come in with more, just wanted to thank everyone.

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