1. Before you begin, you should make some tools. To do this you need a lathe for sure.
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1. A rear bearing puller (drawing
1)
2. A front bearing pusher (drawing 2) 3. A sleeve holder for the lathe (drawing 3) 4. A bearing support for assembly (drawing 4) 5. Needle valve body holder (drawing 5) 6. Piston lap (drawing 6) 7. Dies for shims (drawing 7) 8. Plug turning holder (drawing 8) 9. Shim turning mandrel (drawing 9) |
2) Check the rod fit to crank
pin. It should be tighter or it will overheat. 0.0015 is the correct
clearance. Also
chamfer the front side of the rod
bushing so that the rod will fit up to the crank cheek.
3) Make the crank fit the bearings
by spinning in the lathe and applying 600 grit paper to the bearing
areas
until they are a perfect fit in
the bearing I.D.
4) Make the case between the ball
bearings fit the crank with a 0.002 clearance, this can be done with a
roll of
600 paper around a dowel or rod.
It is not the most perfect method but it does do the job. The crank can
not
touch the case in this area.
5) Fit the bearings to the case.
This is an area where the CS really needs some help. Usually the front
bearing
fit pretty good, but the rear is
almost always too tight. If it is too tight, it will burn up the
bearing very quickly.
A home shop method of bearing fit
is to put the bearing on the shaft and cut the outside of the outer race
with
a flap wheel while holding the
shaft at about a 45' angle, this will take off metal very evenly, even
though it
sounds crude. Clean bearings at
this point. Trial fit the bearing in the case by heating the case at about
150-175
degree and put the crank and bearing
in together. At this temp, the bearing should go in with pressure.
Push
the front bearing into warm case
with the front bearing pusher.
6) Needle valve: The CS needle valve
assembly needs extensive work. The number one problem is the feed
side hole is too large and the
needle will not go into the body so far enough to lean it down enough to
run.
The second problem is the collet
does not have a taper on either the body or the nut to squeeze down on
the
needle itself to make it snug so
it won't change once set. Put the valve body in the fixture and mount
in the
3 jaw so the feed side is facing
the tail stock. Drill the feed side 0.400 deep witha 1/16 drill.
Turn the body
around and cut a taper of 60 degree
on the end of the threads (put the nut on first). Next, take a Zona saw
and deepen the slit about another
0.060 or so, this finishes the machine work on the body. The collet nut
is
next. Check it up in 3-jaw
with the open end towards tail stock. Use a 1/8 center drill to put the
taper inside
the collet to match the taper on
the end of the body. After the center drill contacts the bottom of the
hole,
move it into the hole another 0.007.
Check your work. If it doesn't look like enough, cut another 0.002.
Now back to the body. Remember the
1/16 bore we put into the feed end? Now put A LENGTH OF 1/16 O.D.
brass tubing into the 1/16 bore
and screw the needle in until it stops and then back out one full turn.
Then
slide the 1/16 tubing into the
hole and bottom it against the needle. Sweat solder the tube into the body
in
this position. After soldering,
trim the tubing to flush and deburr and needle valve is done. Sometimes
after
the needle valave body is modified,
the nuts can not be screw on the body far enough to make the collet pinch
the needle. You can either
shorten the nuts or face mill the needle side of the case. The reason
this happens
is some of the valve bodies are
too short to begin with.
7) Now to the sleeve fit in the
case. In about half the engines, the sleeve does not fit the case
perfectly. It
should be a slip fit into the case.
If it does not, mount your liner holder fixture in the lathe and place
the liner
on it with the flange on the left
side. Use your ball bearing center to pinch the liner between the tool
and center
and carefully sand with 600 paper
while spinning in the lathe. Do not get crazy here, you only want
it small
enough to fit, not rattle around.
At this time you may also have to remove about 0.005 from the flange so
that
it will fit into the counterbore
of the case top. Fortunately, most of the inaccuracies of the CS
are on the tight
ride, so they can be corrected.
8) Now comes the piston to liner
fit. Ideally, the piston should stick dry about 0.060 before top
dead center.
This will be loose enough to run
OK initially, but leave enough material to break into a nice running fit
after
a few runs. Some engines
come pretty well fitted, but some are tight,and when run this way they
burn plugs.
Loose plug elements inside your
engine is risky business. Use your piston lap to clean up piston
and make
it round. Cut a little using Bon-Ami
and oil, clean and dry it and check the fit dry. Work very carefully here
-
you can not go back. After
the piston fits, check the "e" ring wrist pin retainers. Sometimes, they
are not
scated in the groove, sometimes
they have been bent during installation and sometimes the wrist pin is
too
long although it is usually too
short, if anything. The "e" rings should not be loose enough to turn
in the
groove with light pressure.
If they do this they will come out at 30,000 rpm, use a magnifier to look
at this
stuff -it is surprising what you
will miss if not using a magnifier!
9) Now you're ready to check the
liner depth in the case. Most CS 049/061 have a problem here. (it is easy
to
fix, but the shims are not easy
to come by. You have to make them). Put the piston and rod on the shaft
and
slide the liner into the case with
the piston at bottom dead center. You should be seeing no more than 0.010
of the piston. If you see more
than 0.010, put a liner shim under the lip of the liner and recheck. When
you get
it close, oil the piston and liner
and put the crank at T.D.C. and tap the case bottome with the palm of your
hand
while holding the liner against
a wooden block to seat the liner in the case. Now, measure the piston to
top of
liner distance. It should be about
0.116-0.118. Add shims under liner to get these numbers.
10) We're getting there now. All
thst is left to do is the head. Here you have two choices: 1. You can use
the
stock CS plugs or 2.You can make
ahead for Nelson plug. I prefer the Nelson, as it is consistant and reasonably
priced and available.
If you elect to make the Nelson
conversion the first project is to get the Nelson blank either from Nelson
or me.
Chuck up the fixture and screw
the blank on. Make a tool with a 0.005 radius so you can cut a reasonably
sharp
corner and cut the major diameter
to the same diameter as the original plug. Measure the depth the
piston is
down in the cylinder at T.D.C and
make this portion of the head exactly the same (0.116 to 0.118). The diameter
of the portion of the head that
goes into the cylinder is very important to be the same as you can make
it.
I measure the piston before i assemble
the block and cut to that dimension first. At this point it will
be too
big, but you can sneak up on the
fit from there. The bottom of the head to the plug face bottom is 0.055
on
the 049 and 0.065 on the 061. The
chamber is cut into the haed with a 3/8 ball mill held in the tail stock
chuck
on your lathe. The vertical wall
between the plug andthe chamber should be 0.008 to 0.009, although it is
not
really too critical except that
it should not be too thin because the Nelson plug would be weaken it somewhat.
The area above the flanger of the
head should be turned to 0.430 to fit the hole in the clamp ring. The bottom
of the clamp ring will need to
be turned down about 0.025 to make it contact the flange of the Nelson
head blank.
Use a 0.005 shim between head and
liner which gives 0.005 deck clearance.
11) Back cover, the CS comes with
an O-ring on the back cover. Most of the time it can be removed and the
cover screwed all the way in until
tight and the clearance between the rod and the back cover will be 0.010
or
so. With the O-ring in, the rod
can move on the pins as much as 50% of the bearing width which results
in
erratic running and rapid wear.
12) Use your drill press or a mill
to cut the liner shims and plug shims. Put the punch in the chuck and the
die
in the vise so that alignment is
prefect and punch holes in Pepsi cans and 0.003 brass shim stock to make
as
many shims as you like.
Cut the holes in to individual holes
and sort of trim around the hole with scissors to get rather scabby looking
shims with a nice round hole the
middle. Then stack them onto the shim turninmg fixture and clamp
them between
the chuck and the ball bearing
tail stock center, and turn to sleeve lip dia 0.003. You will need to make
a punch and
die set for each diameter of hole
you wish to make,i.e. bore size and liner size for each displacment of
engine. This
is also true of the shim turning
mandrel (drawing 7 and 9).
Okay I think everything has been
dealt with. As you can see, this is no small project and even after you
have
the tools made it takes over 2.5
hours each to do these engines right. But the result are much worth it.
The 049
on the tornado 5x3 will turn above
30,000. All of them are better than 28,500 which is very good. The
061 will
turn the 6x2 APC at 29,750 or better.
Both these engines RPMs are with 40-50% nitro fuel. Mix 50% nitro,30%
methanol, 20% KL100 Klotz oil,
to get the best fuel you can use. Klotz oil is 20% castor, 80% synthetic
and
gives good lube and rust resistance
in the fuel.
Remarks from James:
Thanks for the advices, we have
changed much and Nelson head is standard now in our production.