RC India

I have been trying to modify my Cheap 2K Chinese plane I had (two brushed motors(pusher), no control surface, moving stick just switches OFF one of the motors) for genuine R/C flying

1. 32"x5" dihedral wing (Cut 1.24"x6" Ailerons)
2. Replaced the twin brushed motors with a 25g/2S/2200Kv/55W brushless and 4.5x4.5 prop in pusher config. I know the Kv is not right, but my other motors are on the way
3. 2x 9g Servo (Ailerons/Elevator), 2S/800mAh/45g Lipo, 12A ESC

The AUW of the modified plane is almost the original plane at 220g, with additional 30g due to servo/ESC.

the problem I have been facing is with the Aileron Push-rod design. I have stuck an servo at center line of the wing, a little towards leading edge from CG.

The Pushrod is a 1mm spring wire and connected to servo/Horn in Z-bend. I had to bend the wire at around 15 degree to connect to the horn. While the pull is fine, but when pushing, there is large wobble in the middle section of 'Z', and I cannot make that section smaller than 4mm (nose pliers/wire tensile nature). When the servo pushes some of the movement is lost as the middle section slides in the horn, moving the aileron only on the residual 30% of traversal.

I wanted to fly this bird before going on vacation to home, but now its too late. I would be really grateful some one can point to some good text on push rod design, especially the bent/angled ones I would be doing on my foamies very often.

-Ujjwal

Possibly post some pictures to make it clear.

Sorry for that, I would really post it when I get back to home. I just wanted to get some direction on the text on design, so couldn't wait to get the picture.

It appears that your "z" bend is not quite that and is sliding up/down the servo arm. Also possible is that the pushrod wire is too thin for the arm hole.

The middle part of the Z should be the right size. About 2mm, if you measure the inside.

Here is an interesting thread on this :  http://www.rcgroups.com/forums/showthread.php?t=769933

The shrink tube method works if you can get hold of the right diameter ones.

Thanks Awnwar/Sushil/Tg i was looking for similr discussion. The half Z bend with the Red heat shrink looks interesting. But i think I get relevent experience in scratchuilding, I guess its better using standard linkage stoppers like :
http://www.rcdhamaka.com/index.php?main_page=product_info&cPath=56&products_id=289

'Z' bends can be really nasty, specially when you don't have the right pushrod wire.
-Ujjwal

The Z-bend must not be like Z instead it sould be like

_____
        |______. 

And the middle '|' must be like Anwar said straight and at most 2mm.

Look at this page at http://www.airfieldmodels.com/information_source/model_aircraft_hardware/l-bends_and_z-bends.htm - this is a good site that gives good building tips. Look at how small the Z bend is. Use a narrow nose plier to make the Z bends. The wire must also be stiff and not one that bends easily.

In past i was using z bend option for my models. since bending a perfect z bend is not easy with conventional available tools when one is using steel pushrods (very hard). then i see this with Sai:

http://cgi.ebay.in/PUSHROD-SNAP-ON-LINK-FOR-SERVO-HORNS-2MM_W0QQitemZ150379067244QQcmdZViewItemQQptZLH_DefaultDomain_203?hash=item23034a776c

very convenient and easy to use.

Hey thanks Sandeep. I have already ordered these in 1.5mm and 2.0mm and they are on way. Sadly RCD was not having the 1.5mm ones. these terminators are best to be put on the 'Servo' side. The screw design is very convenient in fine adjustment of the rod which are not possible with snap on style/Clevises, and most importantly if you have removable wing section , you can remove the push rod-servo link at will.

The plastic/Nylon clevis/Snap-on clevis are better on the control Horn side - fix once and forget! Though there is such rule, creativity has no limitations.

I took the task of modifying my cheapo Chinese toy with whatever was available with me right now, and tried with the basic stuff (was fun to make motor mount with veneer, wish had seen Ashta's post earlier). A great learning experience.

@TG, I made a similar 'Z' bend as you have mentioned (thanks for the ASCII art work :D) and not the literal slant Z. Ya the problem is making 'Sharp' right angled bends. The rods i have take a small curvature and slide inside the horns!! I guess i would use Bench vice to get a perfect bend and also try to use heat shrink. I don't want to cease experimenting all the options. Its better to learn on an inexpensive, throw away model than burn my feet on an ambitious project!

I would try to compile all your replies and mine experience and put in a separate thread. I hope it come out good enough to find a place in 'Sticky' section.


-Ujjwal

There is one more convenient method of making a good push rod with removable Z bend. instead o f using the entire length of push rod (2 mm fiber rod or steel wire), use easily available paper U clip for end to end connection for Z bend, as paper U clip is easy to bend. paste both end of U clip Z bend using CA glue along with heat shrink tube. i use bamboo stick trimmed to round shape and stick U clip as Z bend. try it once.......

@Sandeep....  Pictures ?  :)

This page http://www.dynmodel.com/sig/007.htm gives some graphic details of pushrod designs.

Here is the picture. actual image will be posted tomorrow.
(http://img02.imagefra.me/img/img02/2/12/22/sandeepm/f_ul2dxq8m_a5ca004.jpg) (http://imagefra.me/)

May do for small electrics but sounds dicey for a nitro model.

Check this
http://www.spadtothebone.com/freeplans.htm

and click on Misc Section

[Admin Update] Direct link : http://www.spadtothebone.com/misc/pushrodbuild.htm

Yep, the "hold" just by the shrink tube between two essentially cylindrical surfaces. The CA helps, but is that enough ?

It would be safer if the other end of the clip is inserted into the bamboo stick itself.

You tube video:

http://www.youtube.com/watch?v=poysDIZnRts

Another video of using a Z bend tool and making a perfect push rod.

http://www.youtube.com/watch?v=GdIDldHeaN0

This one does insert the end of the link into the wood.

Oh my Oh my!! you guys are 'God' of these Small things!! I have busy packing for my home stay, so R/C on the back burner !! Thanks a Ton Folks!!

 :) ;) :D ;D :) ;) :D ;D :) ;) :D ;D :thumbsup: :thumbsup: :thumbsup:

No small thing, a malfunctioning push rod and a lot of effort and time and money would be converted to match sticks after the crash ;D