Assembling your first Team Losi kit
Mark R. Brown / mbrown@OpenMarket.com
- Introduction
- Start stock
- Gather the right tools
- Get the right materials
- Build it right
- Don't over-tighten fasteners
- When it doesn't fit, double-check
- If it doesn't feel right, fix it
- Pay attention to known trouble spots
The instructions for Team Losi off-road
kits are remarkably complete and well-illustrated.
Even so, it's a fact that some folks who buy a kit
aren't able to put it together themselves.
These notes are meant to help you get from the stage of
having bought your first Team Losi
off-road kit to the stage of having
that kit correctly assembled and running around
under your control. The notes focus on the
XX and XXT kits, including the bushing and 'CR'
variants. Many of the general principles described below apply to other
kits, but the particular tips are quite specific to
these Team Losi kits.
A good hobby dealer can help you with any
assembly problems you might encounter. That's a big
reason for buying your kit from a good dealer rather than
from the cheapest dealer. Bring your problematic
parts to the dealer and, most likely, you'll walk
away soon thereafter with the problem solved.
If you conclude that you really don't have the
mechanical skills to complete the assembly, you can
pay your dealer to finish the job for you.
These notes aren't a substitute for a good hobby dealer.
But they make it less likely that you'll need your
dealer's help right away.
If you are reading this memo in hardcopy, you should know that it
lives at
http://www.oocities.org/MotorCity/2314/losi-kit.html --
you may find more up-to-date information there.
I've also written a FAQ
for R/C electric off-road racing; it lives at
http://www.oocities.org/MotorCity/2314/rc-faq.html
Putting together your first Team Losi kit
will be a challenge, but it should be an enjoyable
one. Have fun!
When you assemble your kit the first time, build it stock, with no
add-on parts.
You are a lot less likely to run into assembly problems
if you follow this simple guideline.
And if you do run into problems, the problems will be simpler
to deal with because there can't be any finger pointing.
Obviously, Team Losi is committed to making their own parts fit
together.
You may be asking yourself, "What does he mean by
'assemble your kit the first time'? Once the kit is
assembled, doesn't it stay assembled?" To which
the answer is, "Only if you don't use it very much!"
If you really use your R/C buggy or truck, you will
break things and wear things out. You'll become
very familiar with the workings of your kit. That's
one reason for buying a really good kit to start with --
it is much more fun to work on a kit that's well
engineered than one that barely works.
There are just two exceptions to the guideline:
- Tires.
If the kit tires aren't suitable
for your local dirt, don't waste a pair of wheels
by mounting the kit tires;
mount some tires that will work. If you are
planning to run at a local track, the racers
there can advise you on the choice of tires.
- Turnbuckles.
If you plan to replace the kit
turnbuckles with stronger ones, go ahead and
do that as you build the kit.
Aluminum screw kits are not an exception.
It is very easy to go wrong with aluminum screws because they
are so soft.
If feel you must put your ride on a diet (not necessarily
a good idea), install the lightweight parts after you've got
the standard kit working.
Using the right tools makes assembly much easier.
The right tool is most valuable
when some force is required to do the job.
With the right tool you can
apply just the right force in just the right place.
With the wrong tool you may not be able to get
the parts together, or you may hurt the parts
(or even hurt yourself) with misapplied force.
The Team Losi instructions describe an assembly that
uses an absolute minimum of tools.
It is easy to imagine why:
They don't want to scare buyers by saying that
a whole bunch of tools are required.
But you'll have a much easier time if you gather
more than the minimum set of tools.
Borrow them from a friend if you need to.
- Adjustable pliers.
At several places in the assembly you need a tool
to help press parts into place. The ideal tool for
this purpose is a medium-sized adjustable pliers.
The ones I use are Channellock brand pliers, about
9 inches overall length, with jaw spacing that adjusts
from 3/8" to 1 1/2" (measured with jaws parallel.)
- Wrench for shock cartridge.
You need a wrench for tightening shock cartridges
onto shock bodies. You need a 7/16" open-end
or box-end wrench. Losi says to tighten shock cartridges
with pliers, and you can do that, but
you are much less likely to damage the cartridges with
a wrench.
- Locking pliers.
A small locking pliers (Vice Grip brand or similar)
is useful in a couple points in the assembly.
You can get by with regular pliers, but you'll
have an easier time (and will be less likely to
damage parts) with locking pliers. I use
a 4 inch long Vice Grip.
- Small file.
You'll need a small file for removing two ears from
your servo case. If you have a Dremel tool
and know how to use it, that's even better.
- Small screwdriver.
If your kit is equipped with Hydra-drive you will need
a small flat-bladed screwdriver for installing the Hydra
drain plugs. A screwdriver is also handy for snapping e-clips
into place, though you can make do using the flat side
of the Losi wrench.
- 2.5 mm Allen wrench.
If your kit does not include a 2.5 mm Allen wrench (none of the
kits I've seen does), you'll need to get one for mounting the motor.
- Tools for body trimming.
The body is made of
vacuum-formed polycarbonate plastic; you need tools for trimming
the body to its finished shape and cutting mounting holes:
-
A hobby knife (e.g. an X-Acto handle
with several fresh #11 blades) is the basic tool.
Be careful with it!
-
A short-bladed, stout scissors is very handy for body trimming,
but you can make do with the knife if you go slow and
are patient. Regular scissors are too long for cutting inside curves,
like wheel wells, and fingernail scissors are usually too flimsy to
cut the body.
-
A set of drill bits (e.g. 1/8", 3/16", 1/4",
5/16") is handy for making holes in the body.
You need to make 5/16" holes but if you attack the
body with a 5/16" drill bit you will either
tear the body or end up with a hole in the wrong spot.
Instead, make a starter hole by twirling the point of
your hobby knife.
Then enlarge the hole with a smallest drill bit, then a
larger one, etc.
You can work the bits by hand if you don't have an electric drill;
polycarbonate bounces back from impact but is very soft.
A tapered reamer is an even better (but far less common)
tool for making these holes. Lacking any of
these tools you can cut the holes with the knife if you
go slow and are patient.
-
Some fine wet-or-dry sandpaper is useful for smoothing
the rough edges.
- Nut drivers.
You can perform the assembly without any nut drivers,
but it is a lot easier with nut drivers.
The most important sizes of nut drivers are 3/8" and 1/4";
it is nice to have 3/16" and 5/16" also.
-
You'd use the 3/8" on wheel nuts. These are large locknuts
so they are fairly hard to turn. And you have to reach inside
the wheel to turn them. It is difficult (not to mention
ugly) to use pliers on these nuts.
-
You'd use the 1/4" on the shock mount nuts and on the
slipper/Hydra adjustment.
It is not so difficult to use pliers on these
nuts, but it is still ugly.
-
A 3/16" nut driver would be handy for attaching the 16
ball studs, but you can do the job using the wrench that
Losi supplies.
-
A 5/16" nut driver would be handy for adjusting the servo
saver. There's only one of these and you rarely touch it
so using pliers is not a big deal.
Try to get all four sizes of nut driver if you can.
If you have a 1/4" drive socket wrench
set with 3/16", 1/4", 5/16", and 3/8"
sockets, that's a bit less convenient but will at
least avoid making a mess of your nuts with pliers. Nut drivers
generally have small handles that limit the torque you can apply;
when using socket wrenches you must be very careful not to
over-tighten.
There are two things the kit does not include that you
might think you can do without, but you'd be mistaken:
-
Thread lock. Get Loctite 242 blue thread lock and use it on all
metal-to-metal assembly points:
-
(truck only) front axle set screw
-
cap head screw to attach universal yoke to dogbone
-
slipper shaft long set screw
-
cap head screws to attach transmission case to motor plate
-
Thin CA. Get some thin CA glue (from Pacer, Goldberg, etc.)
The instructions "recommend" that you glue the tires to
the rims. In the case of rear tires, gluing is absolutely
required for all but the tamest use. It is a good idea to
glue the front tires, and required for competition use.
Many assembly problems are caused by over-tightening fasteners.
The materials used by Team Losi are amazingly strong,
but like anything else they have limits.
When plastic is sandwiched between metal (e.g. attaching
a ball stud to a hub carrier using a mini locknut, or
attaching the transmission case to the motor plate
with a long 4-40 screw), you can crush the plastic or strip
the metal by tightening too far. Just snug it up.
When metal threads into plastic, you can strip the plastic
by tightening too far. The front and rear bulkheads
deserve special mention because they are made of
a more flexible
plastic than the rest of the kit -- by design, to absorb
shock. It is very easy to over-tighten screws and studs
that thread into this softer plastic. Don't use
too large a grip (tighten with your fingers, not your
arm), go slowly, feel the resistance build
as the fastener bottoms out, then stop tightening!
That extra quarter turn will make the assembly weaker,
not stronger.
Over-tightening wheel nuts is a common source of
problems. Overtightening these nuts risks damage to your
expensive ball bearings (if you've got them.)
So just snug the rear nuts up to where the wheel does not
wobble on the axle. (The axle will still wobble a bit
on the hub carrier.) Stop tightening
the front nuts when there's still a tiny bit of side-to-side
play of the bearings on the axle.
If an assembly is not going together correctly,
then either (1) there really is a bad fit, e.g. a
part is damaged or defective, or (2)
a mistake in assembly is causing the bad fit, e.g.
you've picked up the wrong part.
Everybody makes mistakes.
If something isn't right, stop what you are doing, take a deep breath,
and then take a second look. Re-read the instructions.
If you can't figure out what's wrong, get a friend to take
a fresh look at the problem.
Don't use force beyond what the instructions call for.
Perhaps the most difficult thing to communicate in an instruction
manual is how something should feel as you are building it.
You learn the correct feel through experience.
Here's an attempt to describe how things should feel:
-
The chassis is meant to be quite solid.
Shock towers and such that are attached (almost) directly to the
chassis should feel like part of the chassis.
When you bolt the transmission assembly to the rear of the chassis,
it should feel like part of the chassis, and should actually add a
lot of stiffness to the rear pivot support.
-
The suspension and steering pivots are meant to be very free-moving.
With shocks not installed, if you raise a suspension arm
it should fall under its own weight with no perceptible
resistance. With servo disconnected, you should be able
to move the steering through the full range of travel with
no perceptible resistance. If you feel binding in
any joint, take that joint apart and look for the problem.
-
The shocks (with springs not installed)
are meant to provide constant damping
through their range of motion. There is a small amount
of air inside the shock; the damping becomes consistent
once the air has mixed with the oil in the shock
(which should take only one stroke.) If not, add oil.
The shocks should bottom out fully without any springy
feeling. If not, bleed oil. Note: The shaft will spring out
somewhat after
you compress it fully; similarly it will suck in somewhat
after you extend it fully. But it won't feel really springy if
you've bled the shock correctly.
-
The gearbox and rear axles should spin with very
little friction.
With the gearbox removed from the car, spin the spur gear; the
spur gear and outdrives should continue spinning for 5-10 seconds.
(Fewer seconds for a bushing kit.)
If the axles don't spin freely with the rear wheels/tires installed
you may have over-tightened the rear wheel nuts.
-
The diff action should be quite smooth.
With rear wheels/tires installed and holding the spur gear,
when you turn one tire the other should turn in the opposite
direction, with no gritty feeling.
When you spin the tire it should coast awhile (1-2 seconds for
a truck, less for a buggy, less for a bushing kit) before
stopping.
If the diff has a gritty feeling, you may have assembled it wrong;
if it has too much friction, you may have used too much grease or
over-tightened the diff.
-
With the front wheels/tires installed, the front wheels
spin very freely. With bearings you should be able
to spin a wheel and have it continue spinning for a good
fraction of a minute before it coasts to a stop. If the front
wheels don't turn freely you may have
over-tightened the front wheel nuts.
-
With the motor and pinion installed, the gear mesh should
allow a slight amount of wiggle-room (backlash) for the
spur gear, all the way around. The pinion and spur
must not bind at any point.
When something doesn't feel right, figure out what's wrong and
correct it. If you aren't sure whether or not something
feels right, take it to somebody who has enough experience
to help you.
Some steps in the assembly process are more likely to cause
trouble than others. Here's a list of problems that I've
noticed, or that others have reported to me:
-
Mounting the front bulkhead can be difficult if the
hinge pins are tight. These fits are tight by design,
to help keep the bulkhead from wiggling around.
The instructions tell you to tap the pins into place
(presumably using a small hammer.) If you've got
an adjustable pliers, you can use the pliers to press
the pins into place. If the pin is correctly lined
up the pliers should give you the leverage you need
to push the pin into place.
-
(Truck only) It can be difficult to get the kingpin hole in
the front axle lined up with the corresponding holes in the
spindle.
Grab the shoulder of the front axle (the larger-diameter
part that sticks out of the spindle after assembly) with
small locking pliers. This will allow you to fiddle with
the alignment until the holes line up by eye. Don't grab
the axle where the bearings are meant to ride, or they might
not slide on very well when you are done.
Now insert the kingpin by hand. Most likely you won't
be able to press it through. So use your adjustable
pliers to press the kingpin a little harder. If it
still doesn't go, pull the pin out and take a look.
You'll see a bit of bright aluminum at the point of
interference. Fiddle with the alignment so this bit
disappears from view, then repeat until the pin presses
into place.
-
The kit contains 16 studded balls and 16
plastic rod ends that attach to them. The Losi rod
ends are excellent -- they don't pop off the studded
balls easily. It stands to reason that they don't
pop on easily, either. Use adjustable pliers to press
them together.
-
Sometimes when you try to adjust a turnbuckle,
turning the turnbuckle twists a rod end off of its
studded ball. There's just too much friction between
the turnbuckle and the rod end. You can reduce this friction
at the time you attach the rod ends. First lubricate the
turnbuckle threads using some oil or wax. Then thread
the rod ends all the way on (no threads showing)
before unthreading them to get the overall length shown
in the instructions. "Working" the ends in this way makes
later adjustment easy. If you've got a reversible
electric drill you can use it to speed up the process.
If you install Lunsford Punsher turnbuckles it is
extra important that you work the rod ends. Punisher
turnbuckles are larger diameter than the stock turnbuckles
so they are a tighter fit to the rod ends.
-
When trimming the lower mounting ears from your servo,
don't leave a square corner as the instructions show; a
rounded corner is stronger. Remove as little plastic as
possible while still allowing your servo to sit flat on the
chassis.
-
(CR only) The bolt-on rear pivot support used on the CR
barely clears the motor plate when you install the transmission.
This creates a problem later when you try to install the gear cover.
After bolting on the pivot support, use your file to remove about
1/16" of extra material above the rearmost pivot support
attachment screw on the right side of the car.
-
Assembling the universal pivots into the rear axle
can be a difficult step. Be patient, line the parts
up, and press the pin home using the adjustable pliers.
-
Use your small locking pliers to hold the shock shaft
while you thread on the shock end. Hold the shaft between
the grooves, and protect the shaft there using some cardboard
or paper towel so the pliers don't scar the shaft.
Don't over-tighten the shock end or you'll weaken it or
strip it out.
To assemble the swivel ball into the shock end, place the ball
on a table and press the shock end onto the ball using
hand pressure.
-
Be sure to use the supplied 3mm screws for mounting the motor.
4-40 screws will seem to work, but won't really hold the motor
securely.
-
The kit instructions include gearing recommendations
for all kinds of motors.
Don't start with a pinion any larger than recommended for your motor.
It is OK to start with a smaller pinion.
-
The pre-trimmed gear cover has a bit of extra plastic
at the outer edges. For the most part that's OK, and it may
even add a little strength. But you may
need to trim off some of the extra material to clear the right
outdrive or to clear the pivot support that you modified earlier.
-
Go very slowly when adjusting the diff.
The rear tire (particularly the large tire of a truck) gives you
a lot of leverage on the diff screw.
It is pretty easy to strip out the aluminum nut that holds the diff
together.
Sneak up on the diff adjustment, turning the right outdrive as little
as possible in each step.
Stop tightening when the diff stops slipping.