Kraton Kraton 8s Steering Problem

[strafefx]

Hey guys,
Just picked up a used Kraton 8s ebx and I'm having a steering issue. I've attached a YT video where I demonstrate the steering with the wheels on & off the ground.
Steering Rate is all the way up and ST trim is in the middle.

servo: Spektrum S905
Transmitter: DX3

Let me know what I should try. I would like to try and fix it as much as possible before going out and buying a new servo.
Thanks!
EDIT: I ended up getting a new servo (primal rc) and reset my steering endpoints also, bumped up the BEC voltage to 8.4v turns way better now!

 

[SrC]

Get rid of that stocker servo. It is undersized for that 30+ pound K8s. And you probably need a better, firmer SS spring. Seems they all run that way out the box. You may want something like this.

https://www.primalrc.com/product-prpre010

or this popular one...
less $$. Many K8s/OC8S guys are running this one. Its all about your wallet. Easy to sink $1k Plus into these RC's out the box right away to make it work right. Parts are costly.

https://www.primalrc.com/product-prpre005

You will need the longer Arrma option part Rx box/servo mount to fit a "True" 1/5 scale servo. Stocker is just a "large" scale servo" for a much lighter RC truck. A True 1/5 servo is what the K8s should have had out the box. Arrma cheaped out. You are not alone. The servo is one of the first things many change out, even before running it. I researchd this K8s well. I passed on it though. Just me. My wallet said no way....There are many 8s threads on AF. Search for them.

 

[Moirae]

Hey guys,
Just picked up a used Kraton 8s ebx and I'm having a steering issue. I've attached a YT video where I demonstrate the steering with the wheels on & off the ground.
Steering Rate is all the way up and ST trim is in the middle.

servo: Spektrum S905
Transmitter: DX3

Let me know what I should try. I would like to try and fix it as much as possible before going out and buying a new servo.
Thanks!

Check the pivot balls and make sure they aren't too tight on the side that's struggling. The steering links also get worn out over time and create tons of slop which could probably lead to something similar as well.

pivot ball ARA330560
composite ball cup set to replace the worn out ones on steering links - ARA330744

 

[SrC]

+1.
Yeah the PB's.... Forgot about that. A simple clean out and readjustment of the PB's matters. They get all bound up with dirt ingress sometimes. Been there, when I run in fine clay dirt. Can even happen quickly within a few packs. Sometimes you can even hear the PB's start to actually Squeak from extreme binding and tightness. Need to isolate/disconnect the servo link to best adjust the PB's for free play. The only way to do it right.
>>>Just there is no substitute for a better servo on othe K8s. Nothing worse than the stocker lame, slow, and weak servo, with any RC model. Driveability truly suffers. SS spring is always part of this equation. Don't overlook that.

 

[PeighDay]

I was also having some weird issues with steering where my Outcast 8s would turn right further then turning left sort of like in your video. Checked all the pillow palls (nothing biding) and tied rods and everything checked out fine. In the instructions for building the servo saver it says to center it as close as you can but to have it slightly to right (see diagram below from instructions). What I did was center best I could but have it slightly to the left. I then adjusted the servo arm to where it was centered with the wheels. Seems to have solved my issue.

 

[strafefx]

Get rid of that stocker servo. It is undersized for that 30+ pound K8s. And you probably need a better, firmer SS spring. Seems they all run that way out the box. You may want something like this.

https://www.primalrc.com/product-prpre010

or this popular one...
less $$. Many K8s/OC8S guys are running this one. Its all about your wallet. Easy to sink $1k Plus into these RC's out the box right away to make it work right. Parts are costly.

https://www.primalrc.com/product-prpre005

You will need the longer Arrma option part Rx box/servo mount to fit a "True" 1/5 scale servo. Stocker is just a "large" scale servo" for a much lighter RC truck. A True 1/5 servo is what the K8s should have had out the box. Arrma cheaped out. You are not alone. The servo is one of the first things many change out, even before running it. I researchd this K8s well. I passed on it though. Just me. My wallet said no way....There are many 8s threads on AF. Search for them.

Hey, I got the primal servo installed and running. Is it safe to bump up the BEC voltage to 8.4v or do I have to leave it at 6.0v (stock)? Thanks!

 

[SrC]

Hey, I got the primal servo installed and running. Is it safe to bump up the BEC voltage to 8.4v or do I have to leave it at 6.0v (stock)? Thanks!

Absolutely 8.4v.
You will get the max advertised
Torque of 130 kg and Max speed of .13 sec.
Just test it out well, to make sure the BEC of your ESC can supply the BEC Amps required for this servo. Otherwise drop the BEC back down one notch. Probably will not need to however, but always test out your changed settings. Even at 7.2 volts BEC, it has impressive specs.

 

[strafefx]

Absolutely 8.4v.
You will get the max advertised
Torque of 130 kg and Max speed of .13 sec.
Just test it out well, to make sure the BEC of your ESC can supply the BEC Amps required for this servo. Otherwise drop the BEC back down one notch. Probably will not need to however, but always test out your changed settings. Even at 7.2 volts BEC, it has impressive specs.

Sorry should have been more specific, I got the PM1373 70kg. The specs says 7.4v is the max voltage. My stock spectrum 160a only has two options for BEC voltage (6.0v & 8.4v)

From my understanding the servo draws power from the ECS so even if its set to 8.4v it will only draw 7.4v, Is that right?

 

[SrC]

Yes max BEC Volts from that 160 amp ESC is 8.4v.
The PM13130 Raminator Servo can run on 8.4v last I heard.
Isn't that what you have??

Description:

Full CNC Metal Case and all Metal Gear 8.4V(MAX) 130kg Brushless Motor Digital Servo

Max Rotation Angle:180°

Pulse width:1000-2000µs=90°

Pulse width:500-2500µs=180°

Dead band: 4µs 1520µs / 330hz

Motor: Brushless Motor

Operating Speed (6V): 0.15sec/60°

Operating Speed (7.2V): 0.14sec/60°

>>Operating Speed (8.4V): 0.13sec/60°

Stall Torque (6V): 107kg.cm

Stall Torque (7.2V): 119kg.cm

>>Stall Torque (8.4V): 130kg.cm

 

[strafefx]

Yes max BEC Volts form that ESC is 8.4v.
The PM13130 Raminator Servo can run on 8.4v last I heard.
Isn't that what you have??

Description:

Full CNC Metal Case and all Metal Gear 8.4V(MAX) 130kg Brushless Motor Digital Servo

Max Rotation Angle:180°

Pulse width:1000-2000µs=90°

Pulse width:500-2500µs=180°

Dead band: 4µs 1520µs / 330hz

Motor: Brushless Motor

Operating Speed (6V): 0.15sec/60°

Operating Speed (7.2V): 0.14sec/60°

>>Operating Speed (8.4V): 0.13sec/60°

Stall Torque (6V): 107kg.cm

Stall Torque (7.2V): 119kg.cm

>>Stall Torque (8.4V): 130kg.cm

This is the servo I have

 

[RCbuzz]

If it's rated for it in the spec sheet, run it! Just know at the higher voltages it does consume more power and may not last as long.

 

[SrC]

My bad. Sorry.
You can always try running it on 8.4 volts on the bench.
One more volt form 7.4v to 8.4 is doable IMHO. No issue at all. One more Volt won't hurt it IMHO.

If it's rated for it in the spec sheet, run it! Just know at the higher voltages it does consume more power and may not last as long.

I beg to differ. Maybe not a hard and fast rule? Just from my experience. One more volt is not significant. Its the Amps that matter. The BEC circuit should handle it as well.
If the servo runs Very Hot then just drop down to 6v. I wouldn't worry however.
A temp gun at the Alu. servo body will judge best. How I do it.
If running an AVC Rx or any Gyro, servos generally run even way hotter, FWIW. Any servo, at any BEC Volt.

 

[stock20]

My bad. Sorry.
You can always try running it on 8.4 volts on the bench.
One more volt form 7.4v to 8.4 is doable IMHO. No issue at all. One more Volt won't hurt it IMHO.

I beg to differ. Maybe not a hard and fast rule? Just from my experience. One more volt is not significant. Its the Amps that matter. The BEC circuit should handle it as well.
If the servo runs Very Hot then just drop down to 6v. I wouldn't worry however.
A temp gun at the Alu. servo body will judge best. How I do it.
If running an AVC Rx or any Gyro, servos generally run even way hotter, FWIW. Any servo, at any BEC Volt.

Arrma Forum tells me to start a new thread instead of reply - but here it goes anyway.
I agree with the comment here. I think folks (including me) often confuse voltage specs for voltage limits.