Throttle linkage tips??

[CustomPC]

John (bigcr),

What's the best way to setup the throttle linkage?

In the video you say you'll be making a dedicated video for throttle setup. How far away is that?

I'm doing mine now and the supplied rod seems too short (forward facing motor).
I'm not too sure that i'm understanding the manual 100%. If i set it up as per the manual the ball links are only screwed onto the rod by about 2mm which doesn't seem enough to me.

Have you tried any linkage setups that introduce some mechanical expo and make the throttle more linear? I found post in RR from a CSM engineer about doing such a thing and it improves the performace of the RevLock.

[david.read]

Hi,

If you measure the distance between the output shaft on the carb and the center point on the servo's output shaft then this is a good starting point. I would reccomend that you try to screw the links on at least 5mm each side.
You mention that you can only get 2mm of thread! Well that's on the tight side, as you already know. Sounds like you require a longer control rod.

When you get the right length of control rod then you can make the distance between links (Ball center) the same as the distance between the servo output spline and the carb barrel. Ensure you have the curve in your radio to 0% 50% 100% (L,M.H) and your throttle trim all the way down. If you imagine a straight line drawn between the servo and the barrel output you need to install the servo horn at exactly 90 degrees to this imaginary line. If this does not work rotate the horn 90 or 180 deg and see if it helps. If it is nearly there then you can use subtrim to get it perfect. When this is done, fit the link to the servo horn and position the arm on the carb to fit the link on the other side, hold the barrel exactly at 50% when you tighten it up. You can remove the link on the carb side to function test the setup if you need to or you can reduce your ATV/ Travel adjust below 100% so when you function the stick the linkage will not bind. Your end points should be very close to 100% when you are finished.

RicksRC has a very helpfull post on this subject in the tips section..

Hope this helps.

David Read.
Heli Addict

[CustomPC]

Thanks David,

After hours of fiddling, i think i have it right..

I did pretty much like you say in the first part of you your post.
The linkage rod is the length of servo spline to butterfly axel (There's still only 3mm thread on the ball links so i have ordered some longer rod).
I set the throttle trim all the way down and the put the arm on so that at 50% it's 90 deg to the line from servo spline to carb axel.
I put the ball on the servo horn at 12.5mm (the manual says 13mm, 12.5 is the closest i have).
It then took a lot of trial and error until i could find which settings match the servo's travel to the full movement of the butterfly.
Eventually i found that setting the endpoints at 120% on both sides was close to perfect.
I put the stick all the way down with trim all the way down and tightened the screw on the carb arm.
It now gives me full travel of the butterfly. Neutral trim looks right for a fast idle.

Everything i've read about these gasser carbs says that 50% revs on the engine is somewhere around 30-40% on the butterfly. My setup now has the butterfly open about 40% with the stick at 50% so i must be close.

Only thing left to do now is start it and fly it to fine tune it all.

[lep1933]

Where can I get the longer throttle link pushrod? Minair has part #122-95 which is 129mm long, but if I cut it, is there a threading tool I can use to put threads back on the one end?

[DavidH]

MA has several different lengths of pushrods. Don't know which MA heli you have. I have been flying MA since 1994. Never had a reason to use anything other the pushrod that MA supplies with the kits to be used from the throttle servo to the throttle arm on the carb.
The MA throttle pushrods are 2mm threads. But you can not really thread a 2mm diameter pushrod from MA. The diameter of the rod is less than 2mm. The threads are rolled onto the rod, so that is what makes the threads 2mm. The rod is like 1.8mm diameter

David

[lep1933]

Thanks for the response Dave. I'm putting the final touches on my Spectra-G and the pushrod in question is part# 122-94 which is M2.6X97mm. I've installed the engine in the forward facing orientation and with the 97mm pushrod, I'm only getting about 2mm/ball link threaded. This worries me since I was told that each ball link should be threaded at least 5mm.

Does MA have a rod that is M2.6 and 103-105mm in length?

[hoot]

MA120-29, PUSHROD M2.6 X 118 is closest I could find

Use 2mm rods.

Search ronlund.com m2 rod

There is 100 and 110 lengths