Is a 3/16 Carbon Fiber Pushrod the General Standard?

[Brendan Eberenz]

Hey everybody. My son took his newly completed profile SV-11 to the NATs for some trimming during the week. We were having some issues and Todd Lee noticed that the carbon fiber pushrod had significant flex to it. It ends up that we were using a 1/8 (OD) sized CF pushrod. I've read a lot of threads on here about creating a CF pushrod, and plan to go with the Central Hobbies titanium ends. My question is about the size of the pushrod OD. We need about a 20in pushrod. Will a 3/16 OD pushrod take care of the flex issue, or do I need to take it up higher to the 0.210 OD CF pushrod on the Central Hobbies site? Most threads on Stunthangar seem to only mention 3/16, but I just want to make sure that I get it right this time. Thanks.

[Tim Wescott]

Check with Central Hobbies. If they're selling carbon fiber push rods and titanium push rod ends, then the ends are probably matched to the rods that they sell.

You probably want to get the matched sets. It will just be less hassle all the way around.

Note that 3/16 of an inch is 0.1875 and carbon fiber tubes are almost never on exact fractional inch boundaries. So if a tube looks like it's 3/16 of an inch, there's a good size that it's actually 0.21 in.

[Dan McEntee]

   Is what you have a rod or a tube? You want a tube as it is lighter and more stiff. The trend in pushrods went smaller I think because the ID allowed the threaded 4-40 ends to be epoxies in place easily. I think Dave Brown Products Stillwell their pushrod kits with everything included. You could also still install a guide or fair lead on what you have.

[Brendan Eberenz]

To clarify, it is a carbon fiber tube (not rod) we are already working with. We did get the alternative recommendation for a fair lead, but our fuselage is a profile body that has 1/64 laminate pieces over a truss frame. Installing a fair lead would take some body work we are trying to avoid.

Central Hobbies has titanium ends that fit either their 3/16 or 0.210 OD tubes. It seems like most people are getting the 3/16 tube, but I wanted to make sure that size has been rugged and successful enough for others with a similar sized plane.

[Motorman]

The 3/16" push rods are ok. I have used them on many stunt ships. The actual OD is .195" with ID .110 which makes them a close fit on a 4-40 bolt or the stainless steel/Titanium rod ends. They are also the perfect size to use 7/32" aluminum tubing as an end cap. I cut the aluminum tubing with a small tubing cutter so it crimps one end for a nice fit.

The .210 tubing has a much larger ID. If you use it make sure there is allot of JB Weld to take up the space or maybe wrap the threads with copper wire to beef up the diameter.

Personally I would not use a fair lead or let anything touch the CF tube.

MM

[Colin McRae]

I have been using 5mm OD/3mm ID CF tubes. Very stiff and the 3mm ID is perfect for using a 4-40 threaded insert. Maybe I'm just fortunate but there is a local RC hobby shop near me that has a good selection of CF tubes and lots of sizes.

[M Spencer]

Depends ifits real carbon . Best tricks try bending it , a good one will have high resistance to bow .
THOUGH Timber has same barometer expansion as timber aeroplanes , so a 3/16 x 3/8 or 14/4 x 1/2 bas or sumsuch , can keep your alignment in , if it tends to wander .

You can translate pushrod load to handleload , in a sense - for extent of duress to maintain equilibrium . If it pulls you off your feet , you need a fairly stiff pushrod .
added :-
Are archers still allowed ARROWS . Carbon Arrow shafts were IT , once .

( these library keyboards sometimes misspell . Sometimes tisnt he keyboard . 

[Steve Helmick]

Aerowhizkid has a good point about the current "CF" tube being real or bogus stuff. I would avoid buying such stuff from eBay or Amazon...unless I had good knowledge of the seller. An example of things to be cautious of is "Spectra" line. A lot of people have reported some is bogus and has no Spectra at all...stretches like mad, and not rated strength. It's why I always...always...buy fishing line from Tackle Warehouse. They don't sell CF tubing, however. I would look to Central Hobbies, a reputable kite shop, or a composite supply store like ACP (not to be confused with APC propellers).  Steve