An interview with Thommy Greer regarding his crawler with a principal focus on what he's done to it to make it competitive, and why.
- John Beech
Based on a Losi Nightcrawler, this 2.2
Sporty has been modified beyond all recognition. I bought it new in
2010 as my very first crawler. While it was a lot of fun to drive
while stock, as my experience level grew I've spent many a long hour
late into the night upgrading, modifying, and tuning it. And as my
skills improved, I've learned a lot with it. Now it's finally to the
point of being fairly competitive.
In fact, it's won several events
including 4th at the Crawl-A-Palooza in 2016, and 3rd in 2017. If the
name rings a bell it's because it's an event held at the rock
crawling mecca of Disney, OK in Mayes County. In fact, this is the
longest running crawling event in the world. Held at Hogan's Off Road
Park on the 2nd weekend of October, prepping for it is one
of the highlights of my year. And it's not just comp and scale rigs,
but a chance to see 1:1 running around on the rocks, too. Anyway,
there's plenty of information about the event on Facebook, so let's
talk about the rig.
The biggest modification involved
ditching the stock chassis for an RC Bros spider chassis. This
upgraded chassis adds a lot more versatility because of the
adjustability of the link geometry. Being able to set up the links
affects how your rig handles on the rocks. Moving the links up or
down affects squats and anti-squat as well as affecting vertical
incline and sidehilling. Another major mod involved the axles
and a TAG kit that's basically a tube that slips into the housing. In
turn, this lets you use Axial XR-10 C-hubs and knuckles (plus their
universal axle shafts). The result of this mod to the front axle is
you get better steering . . . much better steering versus the stock
I'm also using RC Bros knuckle weights (Delrin holder and
tungstem slugs) – these basically let you add unsprung weight at the lowest
part of the vehicle (and out as far outboard as you can). Being on the knuckle
means it's not rotating mass, which would hurt acceleration, and note, it's sitting below axle level. This
is good! Remember, sprung weight is anything like the body, frame, battery, motor, etc. This added unsprung weight aids the rig while maneuvering.
Another essential modification is the
over/under drive. Basically, the front runs a heavy duty spool and
worm gear. The rear runs the stock spool with Dlux Fab chromemoly
worm gear (chromemoly is an abbreviation for chromium-molybdenum
steel). While chromemoly steel isn't as lightweight as an aluminum
alloy, the much higher high tensile strength and malleability makes
it great for this application. Of course, the reason for doing this
is the stock worm gears wore out really fast (the chromemoly upgrade
is almost impossible to wear out because it's tougher than nails).
Anyway, what you end up with is a front with overdrive while the rear
has the stock ratio. Basically, this means the front spins faster
than the rear, which works to suck the rig down onto the rock. Plus
it also helps it turn sharper. Finally, the rig has titanium and
Delrin links – these are more durable than stock, which is
important if only because they slide better over the rocks! Believe
it or not, this can be a big deal.
Of course the rig has comp wheels.
These are also from TAG but since they're out of business, others
have stepped up and offer them as well. Comp wheels aren't just
lightweight, but most importantly, they're very easy for swapping out
the foam within the tires. As experienced crawlers know, swapping
foam quickly may be important for tuning the tires between events.
Anyway, the comp wheels have a 5-bolt pattern with a ring on the back
plus a plate on the front and standoffs in between. Basically, when
you pull the bolts out of both sides of the standoffs, since the
tires are glued to the wheels you can just pull the foam out of the
middle of the ring. This, is way better than trying to cut the tire
off the wheel after it's been glued on, or trying to use beadlocks
since they have a ton of bolts, which means more time. Remember, it's
a combination of what your rig weighs plus the terrain and available
traction that greatly affects what you're going to use in a tire
foam. Being able to adjust, or tune the foam is super important for
Speaking of traction, this brings us to
the custom hybrid tires – 2.2 Rover on front plus Losi Boss Claw.
I call them a Bover tire because we're basically dealing with
one half of each tire glued together. Yes, I essentially slice them
in half and glue the two different tires together! And the rears are
customized also. In this case, they're based on Hotbody Truggy Block
Tires that have been narrowed and then 2.2 sidewalls are glued on.
Sure, it's a lot of work, but they work really good . . . and like
all competitors, I will pretty much work as hard as possible and try
anything to win!
This brings us to the electronics and
motor. I use a Brood vapor brushless motor for the usual reasons –
cooler, faster, stronger, smoother startup, high torque at low RPM.
The ESC is a Tekin RS. It works good with the brushless sensored
motor – and most important, it's compact! As for the steering
servo, the ProModeler DS470BLHV is my choice. It runs cool and is
really quite. Moreover, since it's on the front of the rig where it
gets abused like crazy, having a case machined from a solid billet of
6061-T6 aluminum is super important because not only does it run cool
but it's basically bulletproof. Being a crawler, I've wedged the
front wheels in crevasses and had to work them back and forth to get
loose. I've killed a lot of servos before the ProModeler and I hear
the new version is even tougher because they press bronze inserts
into the aluminum case to reinforce where the steel gear shafts fit.
All in all, my rig's working pretty
good. I'm looking forward to campaigning it this year.