Kraton Kraton 6S V4 Build - now EXB

[Paul777]

So Arrma seem to have managed some UK stock at last so I've finally completed what was intended to be my initial build with the addition of EXB Bumper and Outcast wheelie bar. So thought it was about time I posted a list of everything else that has been done.

- Shimmed diff internals (CoreRC 3.5 x 11 x 0.2 CR452)
- Shimmed input pinions (M13x19mm 0.2mm 2 in each diff https://www.ebay.co.uk/itm/253288550927)
- Shimmed diffs into housings (CoreRC 13x16x0.2)
(See here for details on how I rebuild them https://www.arrmaforum.com/threads/a-nother-reason-to-rebuild-you-diffs-from-new.33003/#post-454866 )
- 500k cst fluid centre, 40K front, 20k and 100k options for rear (still playing around)
- Adjust droop screws - stops the shock ends pulling out
- Add motor fan - generic dual fan from ebay with steel mesh fitted as guard
- Aluminium servo mount - generic version from ebay
- DumboRC transmitter / receiver with gyro (I love the speed of these and easy of tweaking the gyro)
- Vent tyres, seal holes - 3mm cutter in the dremel and go slow to let it cut not tear
- JX Ecoboost CLS6336HV 36KG servo - now removed - doesn't live up the spec
- DS3235 Servo (Provides about 23kg.cm at 6V) - much improved steering at high speed on grass
- 4 circlips on servo saver - significantly improves steering at high speed
- Bearings to replace bushings on steering posts
- Proline Baja Bug body (3238-02) - shoe goo'd where necessary and repaired from previous use with JBWeld in the back vertical bits. Custom mount on rear post mounts
- Aluminium mudguards on rear arms - easy to make and do a great job of keeping the rear arms clean(er)
- Bracing for rear wing - snapped the wing bracket mounting bolts first time it landed on the wing, made this and has been fine since (https://www.arrmaforum.com/threads/bullet-proofed-wing-mount.4111/post-442567)
- Rubber sealed bearings on wheels (RCBearings.co.uk) and in rear diff (will replace other bearings as and when things are apart)
- Tall (Outcast) side guards (AR320352) - bolt straight on V4 and provide much better protection. Not sure if they would bolt onto V5 chassis without some minor mods. Also provide a surface to mount the velcro for the dust guard.
- Dust cover ( this with the side guards keeps 95% of the dirt out, haven't broken a fan blade since) Zips are terrible but just leave the done up and use the velcro - use super glue to attach velcro if it starts coming away from plastic. (https://www.banggood.com/Chassis-Gu...X-Monster-Truck-RC-Car-Parts-p-1651619.html)g
- RPM bumper on rear - fitted without the top section - provides some protection to stop wing braces getting bent
- Diff outdrive inserts (ARA311028) from EXB/V5 on rear - controls the dogbones and seems to reduce outdrive wear, I've put them on the centre diff as well
- Punch set to 6
- V5 rear input pinion (ARA311054) (just because I was swapping a different diff and housing to try different fluid) Seems harder and can be used on V4 (Best used with ARA310977 and ARA310976 but can be used without)
- Found snapped pin on outdrive gear in rear diff that was removed - replaced with 2.25mm HSS drill bit shank
- Found snapped pin on outdrive gear in front diff replaced with 2.25mm HSS drill bit shank
- Snapped pins in new rear diff - replaced with HSS drill (Lesson - HSS work, standard ones don't)
- Add Arrma Extreme Bash Front bumper (ARA320573)
- Add Outcast wheelie bar (ARA320366)
- Shim wheel between bearing and hex with 0.4mm of 8x11x0.2 (CR453) shims on each wheel to reduce slop
- Replaced front diff bearings - diff was clicking under acceleration in the air, bearing wear was allowing diff to move laterally. These were rcbearings.co.uk ones that have only done 3weeks use - maybe 20packs. Conditions have been muddy but this still feels like fast failure. They still run smooth, seals are good - no grit inside but have worn to have lots of play. Have put another set on for now and will see how they go.

 

[Canopy]

Great build, looks very functional!

 

[Paul777]

Great build, looks very functional!

That's the aim, trying to set it up to spend more time bashing and less time wrenching! Need to find some longer lasting bearings though....

 

[Canopy]

That's the aim, trying to set it up to spend more time bashing and less time wrenching! Need to find some longer lasting bearings though....

Yeah I find some bearings are great and some don't last at all. Also made worse by certain driving conditions.

 

[Paul777]

Just ordered some hybrid ceramics (Stainless races, ceramic balls) as an experiment to try in the diffs as there isn't much room for wear on those before the ring gear teeth start skipping under power. I do wish the ring gear and pinion used deeper teeth to give more tolerance to play in the diff, these 6S diffs always look under sized for the power they take.
Although the weather here will hopefully start drying out a bit soon and conditions won't be quite so bearing munching. I checked the play on the rear diff today (which had new a new Arrma v5 diff unit including Arrma rubber seal bearings about the same time) and those have a similar amount of play so will need replacing soon.

 

[Paul777]

Decided to swap the whole thing over to an EXB platform, so it doesn't look much different, just a few shiny red bits here and there! But hopefully less time wrenching and more time bashing, the new diffs with increased helix angle certainly give a smoother sound to the drive.

 

[Paul777]

Slight bad landing today and one of the front hubs broken at the lower ball socket - snapped the socket clean in two. Landing was only small and didn't look bad but the wheel just gave way, must have just caught it wrong or been weakened by a previous impact. So that's on order... For now I've superglued the bits back together - hopefully it will hold if I keep it on the ground until the parts arrive.
Meanwhile I found that trying to remove the wheel hexes the factory had used so much threadlock that one of the grubs stripped even with liberal use of heat. Got it out eventually after hammering a torx driver into the socket so just needs a new set screw. But I wish Arrma would teach the factory how to use threadlock - I removed all the others while I was at it to check and 2 of then I had to hammer the hex off the axle as it had been stuck - so much threadlock had been used it had flowed everywhere. On the other hand both the bolts going into the alu chassis braces had come lose and no sign of any threadlock on those! Seems like the best thing you can do with a new Arrma is disassemble it and rebuild it to make sure everything is starting out right - but of course when a new toys arrives who has the patience for that.

 

[Senton_Prime]

@GunitSamba