Kraton EXB servo saver buzzkill

[Hector_Fisher]

I love my EXB. But it's undriveable as it currently sits.

The steering is.... suggestive at best. Mostly when turning right. And that's what perplexes me the most. I can barely steer right, even when moving. Left turning is less of an issue, but still sucks. I know at least some of the fault is the servo saver (see second video). The saver is activating even though the truck is only resting on it's own weight. You can see the spring going down and the two pieces separating. And ONLY when turning right.

I also know some of the fault is with the servo. You can see in the second video that the plastic case top is flexing under steering. **Top quality cheapo servo** for the win. I will get that sorted out by getting another servo. But why is the servo saver strongly engaging when turning right not left? Is there anything else that i'm missing here?

I've read several threads about shimming the servo saver spring to tighten up steering slop, and I can do that. But this doesn't feel like "sloppy" or "loose" steering, this is bordering on "not steering".

 

[Yas]

Check all the hardware and make sure it's all tight, including the servo mount and the steering rack/ackerman plate. If it's all tight, I'd be shimming the servo saver

 

[FlipSide]

Servo saver does look very weak, but make sure it's not something else binding somewhere. I'd first try disconnecting the servo from the steering linkage and make sure everything moves freely.

The first thing I'd check would be the pillow ball retainers possibly being too tight and preventing smooth steering operation.

 

[Monster Dork]

Good advice above, but I'll echo your sentiment that the KEXB servo saver is not very good out of the box. The key is shimming or using an adjustable post like HR offers. The silver spring is the "hard" one, and it's stiff enough to never, ever allow the servo saver to work in any other car... It was ridiculous in my Typhon. I found that the HR steering setup with the cartridge bearings instead of bushings and a shimmed spring are a sure fix. Use washers or c-clips, appropriately sized, to add about .040" (1 mm) under the spring and try it out. The EXB servo mount is good, but the arm and link are better when made of alloy, too.

 

[Engineer]

Yep. Check that everything is tight and if so - I’d either shim or swap to a V3 steering hub. I get better responsiveness with that and a 25kg servo on my Kraton than in your video above.

 

[marucci87]

What everyone said above, but personally I would get a longer steering horn and make it as straight as possible from the servo horn to the bell crank/servo saver

 

[parcou]

Good advice above, but I'll echo your sentiment that the KEXB servo saver is not very good out of the box. The key is shimming or using an adjustable post like HR offers. The silver spring is the "hard" one, and it's stiff enough to never, ever allow the servo saver to work in any other car... It was ridiculous in my Typhon. I found that the HR steering setup with the cartridge bearings instead of bushings and a shimmed spring are a sure fix. Use washers or c-clips, appropriately sized, to add about .040" (1 mm) under the spring and try it out. The EXB servo mount is good, but the arm and link are better when made of alloy, too.

My Man

So you are saying although the EXB I think has some form of a black shim installed or something there. You felt you still benefited by shimming it?

I do have a better servo mount, removed the bushings, and have the M2C Ackerman plate. I do feel it could be more but I just said, oh well. Nos this has me thinking. How many clips did you add?

By this video, he is saying the servo saver is too loose and need clips to tighten it up

 

[Monster Dork]

On the Kraton, I went with the Hot Racing adjustable servo saver pillar thingy. It has a thread and a thin nut/spring seat that lets you set the spring height (preload) pretty easily. It took very little extra preload to cure my steering issues. I have since switched to HR steering parts in both my 6s toys. It doesn't bind at all and helps with control, you can't beat that. But doing the same preload adjustment with circlips or washers is perfectly viable and cheaper. You can install circlips with a pair of needle nose pliars, no disassembly. Add one at a time until the servo saver behaves as you want. It shouldn't take much. If you overdo it, you're pretty much deleting a failsafe and inviting parts damage. With my poor judgment behind the transmitter, I'm glad my servo saver still functions when I practice sucking ass at sending it to the moon.

 

[Hector_Fisher]

Servo saver does look very weak, but make sure it's not something else binding somewhere. I'd first try disconnecting the servo from the steering linkage and make sure everything moves freely.

The first thing I'd check would be the pillow ball retainers possibly being too tight and preventing smooth steering operation.

I honestly thought it was pretty smooth. I had taken off the servo and the steering seemed smooth and unimpeded. However, I backed out the pillow ball retainer screws an 1/8th of a turn and jerry-rigged a "shim" for one of the linkages so that the linkage would be more flat (it was rather angled before, with the servo saver that Horizon had provided when I called to ask about no servo horn in the box). There is still slop at the ends of the steering throw, but I can actually turn right now. I'll probably look into shimming eventually.

So overall, I am not sure which is the fix that did it. Possibly both.

What everyone said above, but personally I would get a longer steering horn and make it as straight as possible from the servo horn to the bell crank/servo saver

Yeah I ended up doing something similar and got the linkage more level and I think that helped quite a bit (see pic I added above). Just odd because I saw several people on here mention that they ran it angled like that with no problems.

On the Kraton, I went with the Hot Racing adjustable servo saver pillar thingy. It has a thread and a thin nut/spring seat that lets you set the spring height (preload) pretty easily. It took very little extra preload to cure my steering issues. I have since switched to HR steering parts in both my 6s toys. It doesn't bind at all and helps with control, you can't beat that. But doing the same preload adjustment with circlips or washers is perfectly viable and cheaper. You can install circlips with a pair of needle nose pliars, no disassembly. Add one at a time until the servo saver behaves as you want. It shouldn't take much. If you overdo it, you're pretty much deleting a failsafe and inviting parts damage. With my poor judgment behind the transmitter, I'm glad my servo saver still functions when I practice sucking ass at sending it to the moon.

I'm priding myself in having made this a $450 Kraton EXB, so I probably won't add the HR steering parts just yet, but with all the money I saved I may look into it in the future if shimming doesn't do the trick!

 

[marucci87]

Yeah

I honestly thought it was pretty smooth. I had taken off the servo and the steering seemed smooth and unimpeded. However, I backed out the pillow ball retainer screws an 1/8th of a turn and jerry-rigged a "shim" for one of the linkages so that the linkage would be more flat (it was rather angled before, with the servo saver that Horizon had provided when I called to ask about no servo horn in the box). There is still slop at the ends of the steering throw, but I can actually turn right now. I'll probably look into shimming eventually.

So overall, I am not sure which is the fix that did it. Possibly both.

View attachment 183394

Yeah I ended up doing something similar and got the linkage more level and I think that helped quite a bit (see pic I added above). Just odd because I saw several people on here mention that they ran it angled like that with no problems.

I'm priding myself in having made this a $450 Kraton EXB, so I probably won't add the HR steering parts just yet, but with all the money I saved I may look into it in the future if shimming doesn't do the trick!

not only do you want it level but you want to put a longer servo horn on too, I bet that will help, you want it as straight as possibly because that angle your putting more stress in into the system requiring more torque to get it to turn. You want it as straight as possible from the horn to the bell crank while the wheels are straight, and as level as you can like you already did. But imo that short horn put more stress into the servo saver causing it to weaken the spring.

 

[Hector_Fisher]

Yeah

not only do you want it level but you want to put a longer servo horn on too, I bet that will help, you want it as straight as possibly because that angle your putting more stress in into the system requiring more torque to get it to turn. You want it as straight as possible from the horn to the bell crank while the wheels are straight, and as level as you can like you already did. But imo that short horn put more stress into the servo saver causing it to weaken the spring.

View attachment 183399

I see what you're saying. It's an issue with geometry. Considering this is what horizon sent me, I'll be sticking with it for some time until I can afford an alternate. I think the axial servo horn they provided as a "replacement" is only 1 maybe 2mm shorter, but agreed that it's probably affecting the way forces are delivered to the saver.

I have mine pictured next to the 23t that originally came in the box. So technically my EXB DID come with a horn, but not what I had planned based on looking at the manual online prior to purchase.

I don't think the spring would be weakened as such. But if I used it alot this way, I could see premature wear on one side of the servo saver. Like only one side getting used alot. Luckily for me I've only ran this twice so far.