Installing a new servo - how to put servo horn in right position?

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Aeromotive

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Hi all.

As posted earlier, I need to change my throttle servo. I recently bought a Hitec HS-5645MG.

As I was taking off the old servo I took pictures of how the servo horn was placed, in order to reproduce the exact same setting. However I realize it's difficult to get the same exact fit and angle. Picture below is the position of the servo horn that I have now (which I replaced last year because it broke).

352f9yp.jpg


I'm no engineer, so how can I get the closest possible to the stock position? What if I install it a few degrees off? Is it damageable? Can throttle trim help me?
This is my first time doing this, so any tips are welcome!

Aero.
 
Hi all.

As posted earlier, I need to change my throttle servo. I recently bought a Hitec HS-5645MG.

As I was taking off the old servo I took pictures of how the servo horn was placed, in order to reproduce the exact same setting. However I realize it's difficult to get the same exact fit and angle. Picture below is the position of the servo horn that I have now (which I replaced last year because it broke).

352f9yp.jpg


I'm no engineer, so how can I get the closest possible to the stock position? What if I install it a few degrees off? Is it damageable? Can throttle trim help me?
This is my first time doing this, so any tips are welcome!

Aero.

You can use the trim controls on your transmitter to get the servo arm back into the same position as it was with your old servo.

Make sure that the servo output shaft for your new servo has the same # of teeth as your old servo. Different manufactures have different # of teeth. To prevent the servo horn from skipping teeth you need to have the correct servo arm for new servo.

Lee
 
Step 1 is most important. After you mount the servo, plug it in to the receiver and power up the system. This will ensure that the servo shaft is centered. Once you have the shaft centered you can eyeball the angle of the servo arm to get it into a relatively close position as the old one. Then you'll just have to fiddle with trim to get it back to it's sweet spot.
 
Step 1 is most important. After you mount the servo, plug it in to the receiver and power up the system. This will ensure that the servo shaft is centered. Once you have the shaft centered you can eyeball the angle of the servo arm to get it into a relatively close position as the old one. Then you'll just have to fiddle with trim to get it back to it's sweet spot.

Great point.

I just did some checking and a Hitec servo requires a 24T servo saver.

Lee
 
Also many transmitters/receivers have programming settings that adjust your center point on the servo instead of having to fiddle with the trim all the time. I avoid using those knobs because if one gets bumped or messed with ya gotta recenter it.
 
You can use the trim controls on your transmitter to get the servo arm back into the same position as it was with your old servo.

Make sure that the servo output shaft for your new servo has the same # of teeth as your old servo. Different manufactures have different # of teeth. To prevent the servo horn from skipping teeth you need to have the correct servo arm for new servo.

Lee

I'm a bit lost with terminology here :

Servo horn = that L-shaped part (on my picture) that attaches to the servo?
Servo arm = the arm that attaches servo horn to engine?
But I'm not changing the servo arm, just the servo and its horn :/ Or am I mixed up?


Step 1 is most important. After you mount the servo, plug it in to the receiver and power up the system. This will ensure that the servo shaft is centered. Once you have the shaft centered you can eyeball the angle of the servo arm to get it into a relatively close position as the old one. Then you'll just have to fiddle with trim to get it back to it's sweet spot.

Great point.

I just did some checking and a Hitec servo requires a 24T servo saver.

Lee

All right, so is "servo saver" actually "servo horn" (eg. that L-shaped part on my picture)? Because I'm not changing any servo saver (at least I'm not aware of a servo saver for throttle on my model)...
Anyways, the eBay listing from the seller says that my servo comes with different servo horns, so I'm guessing they should have the right tooth count?

Also many transmitters/receivers have programming settings that adjust your center point on the servo instead of having to fiddle with the trim all the time. I avoid using those knobs because if one gets bumped or messed with ya gotta recenter it.

I know the receiver is on the car (connects to my servos and batteries, 3 plugs in total), but what/where would the transmitter be? I'm guessing on my controller? And how can I check if my receiver/transmitter have those "settings"?

Thanks for the input guys, and sorry for asking more questions... I'm trying to learn the most I can!
 
Servo arm, servo horn, same thing. Yes that's the L shaped thing that screws into the servo shaft and controls throttle, steering, and brake.

A servo saver comes in different forms. It can be a 3 piece "servo horn" with like a built in spring in the middle of the horn that allows the top half of the horn to turn too far while the servo shaft and bottom part of the horn remain static at full 60° so the servo gears don't strip.

Another servo saver is plastic or metal rods that prevent the horn from turning beyond 60° . 60° is the common degree of rotation...some go beyond.

Basically it helps protect your servos gears from getting trashed when you are in a turn and slam a wheel into something applying too much force on the servo. Much like stripping a spur gear by having your slipper too tight and landing a jump hard.

Oh and your "transmitter" is your radio.... Which "radio and receiver" do you have and I (or someone) can tell you if you can program it.

Don't be sorry, that's why we are all here everyday. This is a great place to learn all about your RC. I've been in the hobby for more than a decade and I still learn something new everyday!

Sent from my SCH-I500 using Tapatalk 2

---------- Post added at 11:45 PM ---------- Previous post was at 11:35 PM ----------

A few examples of different savers...

852123-seattle-rc-racers-hangar-30-composite-servo-saver-x-stiff-set.jpg


292000079.jpg


servo-mount-servo.jpg
 
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Or maybe just take the radio away from you and let you drive it like Rolex does... on his knees shouting, "Vroom, vroom!"
 
Thanks for the help. About my receiver/transmitter... they're both stock (it's an RTR...). Here are the pictures!

a2rgvo.jpg

1z3uqe0.jpg

cny9z.jpg


By the way, can anyone explain to me the use of the side 6V input on my transmitter, and those 2 switches (one says F-G and the other NP-ADJ)?

Again sorry for picture quality...

I just received my servo... excited about trying it!

Thanks.
Aero.
 
Update

New servo works like a charm. However I can't fit the throttle linkage with the horn that came with the servo. I uploaded 2 pictures to try to explain the issue. The "arm" you see (called "Crank Rod" by Kyosho) is too thick to fit the servo horns that came with my servo. Or the holes of the horns are too small... By the way the horn in the picture is the old one...

317jmkx.jpg

j64nxz.png


(Hope I explained clearly enough)

On the eBay listing from the seller you can see there are 3 horns I can use (I need a 90-degree shape), but none of them fit my "Crank Rod".

There are 2 options here :

1) Get a 24T horn that has bigger holes (how can I know the width of those holes?)
2) Get a new "Crank Rod" that is thinner, so that it fits the horns I already have.

Any suggestions?

Edit : I can't use my old horn because it's a 23T, and my new servo has a 24T spline. I'd rather do things right.
 
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Or maybe just take the radio away from you and let you drive it like Rolex does... on his knees shouting, "Vroom, vroom!"

Haha

Sent from my SCH-I500 using Tapatalk 2
 
A small drill bit or reamer would work fine for enlarging the hole on the servo arm.
 
Wow. Can't believe I didn't think of this!

Thanks!
 
The "NP-ADJ" switch controls your trigger movement. Some vehicles require 50/50 (movement is 50% forward/50% back[brake]). Others require 70/30. 70% of movement is for throttle, 30% is for brake. This usually physically moves the trigger, at least it did on other radios I had that had a switch like that.

Can't figure out what the other switch is for.
 
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