Fitting a Reduction Gearbox to a 6S Kraton ... Econo/Fun Crawler build

[Big Kid]

Having finished up on upgrading and building my first KRATON 6S, am left with once more an almost complete bunch of parts to build another one.
Being i honestly don't need another Basher / Fun Racer .... Put the parts to use purposely set up as a CRAWLER having 1M in center diff, 500K in front & rear diffs.
Super soft shock springs and thick fluid. It is a work in progress and at this juncture we have it operating. ( MEGA servo for steering up next ) Pictures don't necessarily follow sequence of build, tho do show most of the set to date.

Power is coming from a 3642 2250Kv Outrunner Crawler brushless motor that is coupled to a 17 to 1 ratio planetary gearbox. This allows very very slow wheel rotation and a Ton of torque delivered to tires. yea it Crawls and given traction ... Lol straight up a tree !!!

So just sharing an odd little fun diversion from bashing

 

[blaster27]

Looks like a lota fun.

 

[RC Steve]

Nice build.
The hole in your build is a soft servo saver. You need to figure out a way of locking it out so those big wheels turn when you want them to.

 

[joshludden]

Love those tires!

 

[Big Kid]

Nice build.
The hole in your build is a soft servo saver. You need to figure out a way of locking it out so those big wheels turn when you want them to.

Indeed ... a 500 in/oz min servo going in so that will indeed be an issue.
Have an older Gen 2 servo saver in place ( Adjustable preload ) where a heavier spring can be easily fitted.

 

[Big Kid]

We're done minus updated High Torque steering servo ...

Planetary gearbox all greased up, 22t pinyon gear. 36MM fan with a thermo coupler that turns on fan once some heat is detected on gearbox housing.
* Outrunner motors heat up the inside windings and that conducts away via air flow and mounting foot into gearbox.

While mechanically we're fully operational the diffs need to be further stiffened but not locked. 200K F/R is not enough and likely going 500K F/R keeping 1M in center diff if not going spooled ?

 

[pomplemus]

Awesome! I seen to recall you're somewhere around the Sacramento area, I'll need to swing by with my Kraton Krawler build sometime so we can compare notes.

I ended up going with silicone ear plugs in all three diffs, and that works pretty well. Almost locked, but still a bit of give to save the drivetrain when doing things a bit more on the bashing side.

Did you end up going with the 540/550 sized planetary gearbox I see on Amazon under many different brands? I think GoolRC is one?

My build uses a Castle 1717 1250 KV geared at 11: 50, and it tops out around 35 mph, but still has plenty of low end torque with the sensored setup. I'm very curious to see how yours compares.

 

[Big Kid]

Awesome! I seen to recall you're somewhere around the Sacramento area, I'll need to swing by with my Kraton Krawler build sometime so we can compare notes.

I ended up going with silicone ear plugs in all three diffs, and that works pretty well. Almost locked, but still a bit of give to save the drivetrain when doing things a bit more on the bashing side.

Did you end up going with the 540/550 sized planetary gearbox I see on Amazon under many different brands? I think GoolRC is one?

My build uses a Castle 1717 1250 KV geared at 11: 50, and it tops out around 35 mph, but still has plenty of low end torque with the sensored setup. I'm very curious to see how yours compares.

Sadly MUCH slower .... I had ordered by description a 1 to 5 ratio gear box for the D90 crawler. What when received was 1 to 17 being a whole lot lower geared than what wanted. I protested threw ebay this misrepresentation of the sellers specifications to no avail. Went round & round with the Chinese seller who NEVER OWNED UP to the misrepresentation & am at this moment set up as such.
It is LOW low low geared and crawls crazy well .. tho slow with a top end likely closer to 10 mph

 

[pomplemus]

Ah, that's unfortunate. Low speed control must be crazy good though, I think you have a good chance of beating mine in a pulling content!

I just recently killed dual 4S direct power NSDRC RS800 V2 servos in mine. Going to be making some major upgrades, going all out to double the steering torque yet again. Around 320 kg cm (4444 oz in). No such thing as overkill for steering torque in a rig like this!

 

[Big Kid]

Little further along now having a 6s SENTON body and mount kit.
being this is an XL length chassis, as well running a wide track & wheel base some repositioning of body mounts is in order as is some body trimming.

We have spaced the body rearward so the front of body sits behind edge of wheel radius so climbing onto a rock face the tires hit before the body.
As such the front wheel/s turn in out in front of body gaining some wheel well clearing in the back.
Rear wheel clearance is a tad tighter as the body width is almost at inside tires width .... perhaps a taller body position or trimming ? We're not there yet.

 

[joshludden]

Little further along now having a 6s SENTON body and mount kit.
being this is an XL length chassis, as well running a wide track & wheel base some repositioning of body mounts is in order as is some body trimming.

We have spaced the body rearward so the front of body sits behind edge of wheel radius so climbing onto a rock face the tires hit before the body.
As such the front wheel/s turn in out in front of body gaining some wheel well clearing in the back.
Rear wheel clearance is a tad tighter as the body width is almost at inside tires width .... perhaps a taller body position or trimming ? We're not there yet.

View attachment 370035

View attachment 370036

View attachment 370037

View attachment 370038

Body's looking great! What color are you thinking?

 

[Big Kid]

Body's looking great! What color are you thinking?

25 years ago had painted an MP6 buggy body in a YELLOW / RED / WHITE pattern that really stood out. So thinking perhaps a revisit along those lines ?
** Big issue i'm having and NOT FINDING is the masking / window sticker sheet w/o buying another body
A call at some point to Horizon should anwser that Q and help make the paint decision & work willing to be done otherwise.

 

[Big Kid]

Today I tried an alternate to Silicone fluid in F/R Differentials ...
Found a small nugget of HVAC "Duct Seal" in with some moly grease made for a VERY STIFF action in the spyders ... You can counter rotate wheels so there not locked, but almost tho still allow turning with just a mild push happening.
Now the Center is on 1M fluid, and it on a Hard and steep crawl if rears catch a steep ledge it is allowing the rears to stop turning and fronts running alone ... time to SPOOL the center !!!

Whats to lose .. went into center doing the same ... NOW super stiff.

In a crawl test, given traction .. straight up a tree
Up against my foot on rough asphalt, at low throttle ALL 4 tires rotate and paw for traction !!!!! Thinking that works fine

Small crawl up a big boulder in the yard. Abrupt lip @ 5" tall and it walked right up at a dead slow crawl. Not lacking in torque that's for sure !!
Other places in yard, it lacks extreme articulation, but still claws its way threw the rocks unless high centered.

 

[Big Kid]

Ok, here we're changing suspension geometry by extending the shocks lower eye length, bending chassis stop tabs a bit.
Rear shock tower ( Gen 2 ) replaced with a modified Typhon front tower. This brings upper shock eyes closer having shocks laid down a bit ( cantilevered ) more and yielding more total travel. The Camber link hole position was so close to the OEM position, bushed the larger hole and mounted threw them. Adjusted camber a bit & done.
Measured on a set up board both ends now yield 3.4" of vertical travel. Chassis ride height now @ 5/8" higher.
The SENTON body mounts at the rear now is higher allowing for a taller body position over chassis. * Having the SAME shock towers now I'm getting full adjustment capabilities for body height positioning.

 

[Big Kid]

Just ordered a Power Hobby 760MG servo ...
Plan on keeping a servo saver in place as to not stall & burn up a servo.
This is a Play rig and have zero interest in locking up the steering expecting positive wheel contoll at the cost of servo damage ... as someone else has been doing quite regularly

 

[Big Kid]

Lol ... yes you

 

[pomplemus]

LOL I definitely feel called out, haha!

I've had good luck with the 760MG in my basher Kraton. It lasted me I think for a year or two before a particularly zealous skatepark session caused a large enough shock to kill it, I replaced it with the Perfect Pass monster. Both of those as far as I know are private label versions of the AGF A86BHM 55 Kg servo which I tried in my Kraton Krawler. It never died, but it just faded (torque wise as it heated up) too quickly to be effective with the 8" RC4WD tires I'm using.

I think it will do fine with the more reasonably sized wheels you're using, and it should reduce power output to keep itself from burning out when stalled. You can get a bit more out of it too by using a solid external BEC, I like the Hobbywing 10A.

 

[Big Kid]

Pomplemus,​

It's all good ... You had posted within your build thread the Servo journey had been rather costly, So I'm not stating or calling you out on anything new.
I run the PH 729 in my Kraton hybrid with good luck so far, tho only pushing things with 4S power.

Ideally as you have done, some Tall tires like the Proline XL crawler tires might be in my future.
The Member who posted a picture of his that he modified for his 17mm hex arrma .. I sent him a PM being he loosely seemed to state he might be willing to part with them ?

 

[pomplemus]

Haha, of course, just poking some fun at myself.

I started my build on a budget, buy that ship has sailed and sunk long ago, I just like to conveniently ignore that fact!

Jenny's has the SCX6 wheels/tires, they should fit with some minor cutting, possibly another option at a reasonable price.

 

[Big Kid]

Put in a PowerHobby 760 HV servo last night then beefed up the servo saver spring to very stiff specs.
Went out Krawling today for about an hour in the front and side yard rock piles ...
This rig is a kick in the ass !!

It paws itself over dang near any obstacle given traction, Goes really slow if requiring that technical touch.
Waiting on some AXIAL 1/6 scale 7" crawler wheel / tires now .... Once done we finalize body cutting and get painting