Granite Standard Process for Replacing a Servo?

[Necplur]

Is there a high-level procedures list for replacing a servo? This is for the Granite 3S BLX, purchase about two months ago from Horizon.

I'm replacing the stock servo with a Spektrum S6240 (I know, I know. Everyone seems to be going the Savox, but I went with what the person on the other end of Horizon's chat recommended, before I found this site.)

I see some videos about removing the electronics module first and tips to get wires inserted and so on. But what about the final installation and config? Making sure it's centered correctly, and so on?

And documentations or videos?

 

[Cheapbastard]

Turn the esc on, let the servo center itself, turn the transmitter on with the steering trim in neutral, then place the servo saver on the servo, the servo saver should be pointing to the outside of the chassis. You may need to adjust the steering trim to get everything centered once installed. Then you need to set your steering endpoints or if you have the STX2 use the steering rate (D/R) knob to adjust the steering so the servo won't continue to turn when the steering bellcrank (where the steering toe links attach) hits the middle of the chassis turning left or right.

 

[JAM]

Start by removing the entire esc/servo module out of the chassis.

 

[Necplur]

Turn the esc on, let the servo center itself, turn the transmitter on with the steering trim in neutral, then place the servo saver on the servo, the servo saver should be pointing to the outside of the chassis. You may need to adjust the steering trim to get everything centered once installed. Then you need to set your steering endpoints or if you have the STX2 use the steering rate (D/R) knob to adjust the steering so the servo won't continue to turn when the steering bellcrank (where the steering toe links attach) hits the middle of the chassis turning left or right.

This is awesome, thanks! (I also got a DX5C and new receiver... but I think I might do one at a time.)

 

[Oldskool]

23t output shaft...

 

[Arrmature]

Witha servo that power hungry I'd consider using an external BEC.

 

[Necplur]

23t output shaft...

I don't understand?

 

[Arrmature]

I don't understand?

The stock servo and servo saver have 25 splines on the shaft. The spektrum has 23 splines on the shaft. You won't be able to use the stock servo saver, you will also need a 23T servo saver. Savox servos are also 25T which is why they are often used.

 

[Necplur]

Witha servo that power hungry I'd consider using an external BEC.

What's a BEC and how do I know if I need one or not? (I'm googling and reading that it's some Voltage Regulator/Battery Elimination Circuit... so I know what the abbreviation is, but not actually what I need it for.) From the ones on Amazon, what to the free wires connect to?

Is this the same or different than a glitch buster?

The stock servo and servo saver have 25 splines on the shaft. The spektrum has 23 splines on the shaft. You won't be able to use the stock servo saver, you will also need a 23T servo saver. Savox servos are also 25T which is why they are often used.

Bah, thanks! I thought the Horizon chat would have told me that...

 

[Cheapbastard]

Get a Kimbrough servo saver then. The Kimbrough 124 servo saver would be the one to get. Use the spline adapter labeled A for 23t spline servos https://www.amainhobbies.com/kimbro...XUJ088K4mPfOwcG8wVRKVAxHi1l2VRu4aAiaGEALw_wcB. Just need to trim it to fit, drill a hole a little bigger for a 3mm bolt and add a 3mm locknut.

 

[Necplur]

Get a Kimbrough servo saver then. The Kimbrough 124 servo saver would be the one to get. Use the spline adapter labeled A for 23t spline servos https://www.amainhobbies.com/kimbro...XUJ088K4mPfOwcG8wVRKVAxHi1l2VRu4aAiaGEALw_wcB

Thanks! Do I need to get grease, too?

 

[Cheapbastard]

Thanks! Do I need to get grease, too?

Nope, I added a picture above in my previous post what it should look like when installed.

 

[Necplur]

Nope, I added a picture above in my previous post what it should look like when installed.

That's great. Thanks again.

 

[Arrmature]

What's a BEC and how do I know if I need one or not? (I'm googling and reading that it's some Voltage Regulator/Battery Elimination Circuit... so I know what the abbreviation is, but not actually what I need it for.) From the ones on Amazon, what to the free wires connect to?

Receivers and servos work best when they are powered by a nice, clean stable voltage. The demands of the motor causes the voltage of the battery to vary quite a bit and very suddenly. Back in the old days (which I am old enough to remember) a second smaller battery was used to power the receiver and servo. Then the BEC was born. The BEC is basically a voltage converter/regulator that takes it's power from the main battery and outputs a nice clean stable voltage for use by the receiver/servo. The BEC is built into the ESC and in these cars outputs a regulated 6 VDC at 3A maximum. The stall current on that Spektrum servo is 4.9 A at 6 V. Every time the servo chnages from being stationary to moving, the servo is stalled and so will draw 4.9 A for a very short time. The BEC can probably handle those short bursts, but no guarantees. The real problem happens of you're turning and something like a stick or a rock jams the steering an it's unable to return to center. When you release the steering, the servo will draw 4.9A trying to move the steering until the BEC burns up. It's possible that the ESC output is protected, especially if it is a switch-mode ESC, but Horizon won't (or can't) share those details.

Is this the same or different than a glitch buster?

A glitch buster is nothing more than a capacitor. It basically knocks out any high frequency ripples (noise) on the power lines.

Bah, thanks! I thought the Horizon chat would have told me that...

I totally agree They should have known better.

 

[Necplur]

The BEC can probably handle those short bursts, but no guarantees. The real problem happens of you're turning and something like a stick or a rock jams the steering an it's unable to return to center. When you release the steering, the servo will draw 4.9A trying to move the steering until the BEC burns up. It's possible that the ESC output is protected, especially if it is a switch-mode ESC, but Horizon won't (or can't) share those details.

Again, amazing information. Thanks. this is all very fascinating.

I meant this to just be a fun, easy upgrade. Something bigger than the 6.5kg servo in there. All the YouTubers seems to say two definite immediate upgrades on the Granite 3S BLX: New radio. New servo.

How critical is the external BEC? What are the risks of not getting one? (read your example of the stick in the steering, but was wondering if you thought this was just a matter of time in a few runs that I would burn this out?)

How does one know if an external BEC would be beneficial. The Stall Draw, I'm thinking? And what limit/number would need one? Looks like the Savox 15kg has the same(-ish) draw. Would that need an external BEC, too? That one at least would have been easier at 25T...

 

[parcou]

Thx for the post...so as a newbie I have purchased a new steering servo for my Granite BLX still waiting for it to arrive here.

I also bought this servo saver for it. How do I determine which spline I need?

 

[cageywhite]

Thx for the post...so as a newbie I have purchased a new steering servo for my Granite BLX still waiting for it to arrive here.

I also bought this servo saver for it. How do I determine which spline I need?

I literally just completed this swap out today. Follow the instructions you've gotten in this thread and it works great. I used a Dremel tool to reduce the size of the servo where you attach the screw. You also get three different adapters to put on the post on the servo that turns it from left to right. Just pick the one that fits and you are good to go.

 

[Necplur]

Just need to trim it to fit, ....

What part needs to be trimmed?

drill a hole a little bigger for a 3mm bolt and add a 3mm locknut.

Is the circle in red what needs to be drilled out a little more?

And is a 3mm locknut something I need to provide or is this something that either comes with the servo or I can reuse from the stock one?

 

[JAM]

What is in yellow will need drilled out. You’ll see that though once you get it. The m3 bolt won’t fit. I also opted for a longer bolt that was already circled in red as the hardware that came with it does not work.
Also where I added blue is what needs trimmed down as the saver will hit the wall where I put the x. I shaved mine down “carefully” with a knife then used a heavy grit sandpaper to fine tune it. That’s if you do not have a dremmel. I do but on the first go at it I didn’t want to shave too much.

If you install everything but the saver, which you should so you can power it on and let it center itself first, then you can start test fitting the saver as you trim.

 

[Necplur]

What is in yellow will need drilled out. You’ll see that though once you get it. The m3 bolt won’t fit. I also opted for a longer bolt that was already circled in red as the hardware that came with it does not work.
Also where I added blue is what needs trimmed down as the saver will hit the wall where I put the x. I shaved mine down “carefully” with a knife then used a heavy grit sandpaper to fine tune it. That’s if you do not have a dremmel. I do but on the first go at it I didn’t want to shave too much.

If you install everything but the saver, which you should so you can power it on and let it center itself first, then you can start test fitting the saver as you trim.
View attachment 83022View attachment 83021View attachment 83022

OK, that settles it, I'm getting a Dremel! ;-)

Just to make sure, shaving the new servo saver, not the car/electronics basket?

Also, have any suggestions for a box of bolts and stuff? You said you opted for something bigger and I'd have no idea. I have nuthin'