Optimal throttle servo placement for a linear movement/motion

[skunkwurk]

Hi guys,

Installing a throttle servo and figured I'd put a post out there to gather your thoughts before I epoxy it in. I made a servo mount to place the servo arm orientated exactly 180 degrees from the throttle arm, up(servo) vs down(throttle). The mount would lay the servo on it's side so that the arm would swing forward/down as the throttle arm would push forward/up, using 1" arms on each end. I think it would be a pretty clean and a mechanically linear setup.

My question is the following. I see a lot of the guys simply cut out a hole in the bottom of the motor box and screw the servo to the box. Any benefits or comments on approach? I've installed servos outside of the fuselage before, with either approach I would have a portion of the servo exposed to the cowl area. So I don't see a benefit regarding interference or temperature between the two. I've even seen servos recently being installed between canister pipes in the fuselage tunnel.

I've added some pictures of my mock up of the servo and mount. Thanks in advance guys.

sc

 

[Bunky.F.Knuckle]

The 2nd pic is how I mount the throttle servo on my 35% Carden Extra. I have seen/found no ill effect. I don't think there is a wrong way to mount a throttle servo.

Lots of folks choose to mount the servo far away from the engine. I have/will have again an airplane like that. There is nothing wrong with it, outside of such a long carbon pushrod.

 

[skunkwurk]

thanks Bunky.

 

[Bartman]

I don't think there is a wrong way to mount a throttle servo.

i don't disagree with you but i like to have at least one layer of airframe between the servo and the engine just to keep it out of the gunk and heat of the engine area.

@cespedes; you could mount the servo on the other side of that lower engine box panel and let the arm hang down through the box so the geometry will be nearly the same but the servo will be on the other side of the box. you might need a longer arm to make it work and that might screw up the geometry of the two linkages and if that's the case just ignore everything I've just said.

 

[jlmold]

If it was mine, I would mount the servo on the inside of the box just to keep it cleaner. just my 2cents.

 

[rcpilotacro]

...and cooler 2+2 C

 

[stangflyer]

If it was mine, I would mount the servo on the inside of the box just to keep it cleaner. just my 2cents.

Plus with it on the inside of the box, you can get more of a "straight" on geometry angle on it. The way that you have it mounted, it appears to me that the servo arm has to "raise" the link as it is pushing it. This geometry is going to change every time you advance or pull back on your throttle stick. The best angle of attack....is the straight on approach.

 

[skunkwurk]

Plus with it on the inside of the box, you can get more of a "straight" on geometry angle on it. The way that you have it mounted, it appears to me that the servo arm has to "raise" the link as it is pushing it. This geometry is going to change every time you advance or pull back on your throttle stick. The best angle of attack....is the straight on approach.

I think the geometry would be very linear as it's laid out. I think of it this way, I could be wrong, but I see it as 2 gears of the same size. If one gear turns to the right and you had a dot at the top of the gear, it would roll to the right and down. The adjacent gear would begin to turn left and if you have a dot on the bottom of the gear, it would begin to move forward and up. That's the type of motion I'm trying to put into place. where the two dots are the servo arm 4-40 thread. Hope that makes sense.

Also, I've redesigned the servo mount based on feedback. I think it will enclose the servo enough to protect it from the heat, gunk, etc... let me know your thoughts.

sc

 

[skunkwurk]

Final install of the throttle servo, the movement is very clean and linear with butterfly movement. I think the servo is well protected as well.

sc

 

[stangflyer]

By golly, I think you've got it. Looks very clean, accurate and overall nice neat setup. I think you will have no problems with that setup.