RCGuy.com Servo Relocation Plate and diff
lockers
The overkill FXR-Pro Tekin ESC.
The lightweight A123 packs reduce CG
Top
link is extended with un-used lower link brace via a little trimming and a
long grub screw]
RPM's narrow crawler wheels vs regular width wheels.
Rock King Crawler Project
Phase 2 Wheelie King Crawler Conversion
By Tony
Arnold – StampedeProject.com
Last
month we explained some rock crawling basics and even completed a Phase 1
Wheelie King crawler conversion that put us out on the rocks in a hurry.
Facing the facts, the stock Wheelie King’s wheelbase and high rearward CG
(center of gravity) isn’t the best for a crawler, we need a longer & wider
chassis, a different CG, more power, more articulation and better traction
like real rock crawlers. Since last month, I have spent my time morphing
our Phase 1 HPI Wheelie King into a sloth-like competition level rock
crawler through a lot of trail and error, but it wasn’t easy. Knowing I
would cook up some custom fabricated crawler, Stephen made things rough by
mandating a zero fabrication build that anyone could complete – OK, so not
a bad idea. Though minor Dremel tool modifications were allowed, I could
not so much as drill a hole in the chassis.
-------------Call Out--------------------
Previously Completed Phase 1 Conversion
-
Remove the
rear sway bar
-
Reverse the
tread pattern on the wheels for better traction
-
Remove the
wheelie bar
-
Installed
RCGUY.com diff lockers
-
Kimbrough
66T 32P Spur for Associated trucks #249
-
Robinson
Racing 9T 32P pinion #0090.
--------------------------------
Build Research
Attempting to consolidate down all the great crawler ideas into one easy
build took some time. I canvassed forums and looked at hundreds of
crawler-winning designs, played around with a plethora of shock
placements, shock-tuning changes, and nominal weight & CG changes on the
Wheelie King. My efforts identified a combination that drastically
increased articulation by nearly double of other standard conversions and
delivered competition level crawling capabilities. As you can see from
the scrapes on my crawler, this process took a lot of trial and error.
Without cutting, drilling, or fabricating, the result was an innovative,
durable, and easy build that transformed a Wheelie King into a competitive
Rock King with almost 90 degrees of un-forced competition level
articulation with mind twisting CG that was oh-so-fun to drive.
--------------Call Out -------------
ROCK KING - PHASE 2 UPGRADES
REMOVED:
UPGRADED:
-
Stock 27T
motor upgraded to Axiom 85T V10 Crawler Motor
-
Stock ESC
upgraded to Tekin FX-R-Pro
-
Stock NiCd
battery to a slim A123 Racing 6.6V 2200Mh Lithium-Ion pack
-
Deans
Ultra-Plugs on all connections
-
Servo
upgraded to a high torque servo
-
Shock oil to
1000wt Silicon diff fluid
-
Locked
differentials with RCGUY.com dif lockers (Phase 1)
-
Kimbrough
66T 32P Spur for Associated trucks (Phase 1)
-
Robinson
Racing 9T 32P pinion (Phase 1)
-
Drive shafts
to E-Maxx replacements with about 3/8” trimmed all ends
-
Wheels and
tires to RPM Crawler wheels and Pro-Line Moabs
CUSTOM:
-
Dremeled top
battery tray flat
-
Axiom motor
end bell was rotated 180 degrees to reverse the motor
-
Repositioned
receiver to the rear of the battery tray
-
Mounted
Tekin ESC between reciver and motor
-
Moved the
rear steering lockout to the front
-
Rotated
suspension stays 90 degrees
-
Attached new
extended top and bottom links
-
½” fuel
tubing added as soft limiters on all shocks
-
Rear shocks
left sprung and attached as shown
-
Front shocks
inverted & installed springless for a drop front suspension
-
Trimmed rear
left carrier to accept a RCGUY.com servo relocation plate
-
Stared the
rear tire foams and V cut the front tire foams
-
Added ½ cup
airsoft BBs in each front tire
-
Screwed
antenna mount to shock mount for an under body antenna
-
Body was
trimmed for articulation clearance
-
Body side
panels were bent inward for snag free crawling
-----------------------------------------------
Leaks & Tweaks
A picture is worth a thousand words and the inserted pictures hopefully do
a better job explaining the build that I would, however one particular
point deserves a little explaining. Looking at the pictures you might as
“why did I only set up rear steering?” The answer is that in order to
flip that painful rear biased CG, I made the front of the truck the back
and the back the front to move the battery and motor weight over the front
of our crawler. The truck is now running backward, however earlier I
rotated the end bell of the motor 180 degrees so that the motor and
transmission will now run in reverse – worked great. You may also notice
one leaky shock received a Traxxas aluminum shock cap and new seals; the
others were not leaking after swapping fluids so I left them alone however
a rear shock spring kept popping out of its retainer.
--------Call Out -------------------------
Phase 2 – Rock King Parts List
-
2 sets (4
total) Traxxas T-Maxx Turnbuckles 116-118mm #5139
-
1 set (2
total) Traxxas Half Shaft Drive Shafts #4951X OR HPI E-Savage Drive
Shafts #82008
-
RCGUY.com WK diff lockers
-
1 RCGUY.com WK Servo relocation plate
-
Axiom 85T Crawler Motor
-
1000wt
Silicon Diff Fluid
-
Tekin
FXR-PRO ESC
-
Trinity
Golden No Solder motor leads
-
Deans
Ultra-Plug Connectors
-
A123 Racing
6.6V 2200Mh Lithium-Ion Pack
-
High Torque
Steering Servo
-
RPM Narrow
Crawler Wheels with ½” offsets
-
Pro Line
Moab Tires
-
1 Cup
Airsoft BBs
-
StampedeProject.com Decals
-
Fuel Tubing
for shock limiting
-
12 – 3mm
locknuts
-
4 – 3mm x 15
machine screws
-
8 – 3mm X 30
machine screws
-
24 or so –
3mm Flat washers
-
4+ - Shock
limiters or pistons for spacers
-
2 – Traxxas
grub screws #3962
------------------------------------------
Final Testing & Conclusion
Granted the upgrade list isn’t short, however you may already have a lot
of these parts if you really look through your parts bin. Although a ton
of testing lead up to our final testing, it was all worth it. The short
and narrow stance of a stock Wheelie King is definitely was way under
USRCCA 2.2 Class 12.5” wheelbase and overall width limits and flipped on
anything over 45 degrees. By stretching and widening that stance closer to
the limits and the other upgrades, we now have a competition level crawler
which can ascend some near vertical obstacles with a mind bending CG with
almost 90 degrees of free articulation. The Rock King performed very well
on the variety of rock piles I tackled and cleared all but the most
challenging courses I set up in my rock strew and piled landscaping (no
need for a road trip, fun can be had in my front yard.)
Although I used widely available bolt on parts in the two conversions, a
little homemade part fabrication will deliver a truly custom pro class rig
with tons of tuning capability. There were a couple changes I would have
liked to make such as swap out the flexible plastic steering links with
metal, and add custom shock mounts, but those would have required
fabrication. Want to see how to make an easy custom crawler chassis? Bug
Stephen with an email and I’ll whip one up in a future article.
-----------Stand Alone Call Out--------
Rock King & Crawler Build Tips
·
Moving
shock placement inward at the top softens the suspension and increases
articulation.
·
Heavier weight
shock oil or even diff fluid in the shocks improves performance.
·
Droop suspension
allows suspension to droop and provide traction when high centered.
·
Cut tire foams in
an eight-pointed start pattern greatly increases traction.
·
Cut front tire
foams in a V pattern and add ½ cup airsoft BBs per tire improves traction
and lowers CG.
·
A 55T motor may be
a little fast in the WK – the 85T Axiom worked great and allows for faster
gearing.
·
Adding a large
spacer to each shock on the right side to combat torque lean.
·
RCGuy.com diff
lockers and servo mount plate make things easy.
·
RPM’s crawler
wheels & Pro-Line Moabs greatly improve traction
--------------------------------------
The
more experience I have with rock crawling the more I love it. Playing
around with tons of different ideas really brought back feelings that I
have not had since I re-entered RC. Watching something I created clear an
impossible obstacle is a great feeling, a feeling I think is almost lost
in today’s spectacular quality RTR RC world. Transforming a humble
Wheelie King into a truly competitive Rock King crawler with amazing
articulation… well, it was just cool. You really can’t explain what it is
like to watch and recover from a perfect vertical balance or picking a
line and watching your crawler perform mind-blowing maneuvers. Building a
crawler is almost as fun as driving one and I had a great time engineering
and completing this build. If you are looking for an inexpensive way to
get into competition crawling, the HPI Wheelie King is becoming one of the
hottest crawler build platforms and with the exception of the crawler
motor and diff lockers. Now I know why, this was one of the most fun
builds to date. See you on the rocks…
---------Call Out--------------
Final Rock King Specs
Wheelbase: 12.4”
Overall Width: 12.25”
Weight Bias: Approx 75% Front
Motor: Axiom 85T V10
Gearing: 9/66 32P
Battery: A123 6.6V Lithium-Ion
ESC: Tekin FX-R-Pro
Wheels: RPM Crawler ½” Offset
Tires: Pro-Line Moabs
-----------------------------------
Sources: HPI –
www.HPIRacing.com, Axiom Motors –
www.AxiomMotors.com, RC Guy –
www.RCGUY.com, Tekin –
www.TeamTekin.com, RPM Racing –
www.RPMRCProducts.com, Traxxas -
www.Traxxas.com, Pro Line –
www.Pro-LineRacing.com, Deans –
www.deansplugs.com,
A123 Racing - www.A123Racing.com, Custom Decals -
SupersportUSA.com
FINAL NOTES
- I have received some comments that the article published in RC Car
lacked some detail, it turns out RC Car didn't want to run a ten page
article so I had to cut it down...a lot.
See
the Full Un-edited Wheelie King Build here.
