Construction Tips and advice From Bob Shores
Good
ideas on how to do certain operations in engine building that may not be
obvious in the beginning from a master engine builder.
108 Carmelina St
Ruskin, FL 33570
bobshores@msn.com
http://www.bobshores.com
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TIP 1 RODS
Very few engine construction plans and drawings specify the order of
production of engine parts. The builder is expected to produce the parts in a
logical order that allows fitting the part under construction to existing
parts. The FIT is more important than the exact dimension.
Too many builders assume they can build parts in ANY order as long as they
are produced exactly to the dimensions shown. The TIP here is to build the
connecting rod LAST, as this is the final opportunity to EASILY set the
desired compression ratio by varying the rod length.
Bob Shores
Ruskin FLA |
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TIP 2 HEAD GASKET
An excellent choice for head
gasket materiel is virgin Teflon. A thickness of .032" is also a good choice
as the thickness can easily be changed, at a later time, to change
compression ratio. It is not likely that a Teflon gasket will
"blow", it will not stick to the head or block at high temperatures
and needs no sealing compound. It is a pleasure to lift the head off the
engine, after years of running, and not encounter the mess left by Asbestos
and paper gaskets. Sheet Teflon is readily available at a reasonable price.
Avoid Teflon that has been etched on one or both sides.
Teflon is easy to cut if you
use Brass tubes, sharpened at an angle from the inside, much like a core
drill. The correct OD Brass tube will slip inside the head bolt holes to cut
the gasket. The larger cylinder holes can easily be cut with precision if you
take a minute to turn out a cylinder with a 1/2" spigot. Sharpen the
business end of the cylinder with an internal angle to form a sharp edge at
the OD. Clamp the Teflon sheet, on a
wood block, on the mill table and cut the first hole. Move the table the
required distance (cylinder spacing) and cut the next hole.
Bob Shores
Ruskin FLA |
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TIP 3 CROSS HOLES
Often builders are required to drill a cross hole in a round, square or hex
rod to accommodate a pin or bolt. Some just "eyeball" it, and hope
for the best. Others use an Edge Finder, and hope for the best. Still others
mill a small flat spot, and hope for the best. Here is a quick, easy
procedure I use that gives good results.
Clamp a block of metal, with one reasonably flat side against the stationary
jaw of the mill vise. Drill a hole the size of the rod to be drilled. Without
moving anything else, loosen the vise and rotate the block 90 degrees.
Tighten the vise, insert the rod to be drilled and drill the cross hole
through the block and the rod. Both holes have the same center and the block
acts as a drill guide. Drill the opposite end of the rod for a spare.
If you have a drill large enough, or a boring head. the wrist pin hole in
pistons can accurately be drilled and reamed with this procedure. A little
extra time will prevent ruining a piston.
Bob Shores
Ruskin FLA |
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TIP 4 FLUID SAVER
Here is a quick, easy addition to your shop that will save money and time. You
will need a small plastic spray bottle, the type used to spray eye glass
cleaner. Empty bottles, in various sizes can usually be purchased from Kmart
or Wal-Mart. You will also need the red plastic tube usually taped to the
side of spray cans such as WD-40.
Pull the spray head off the bottle and drill the spray hole the same size, or
slightly smaller, than the OD of the red tube. Heat the center of the red
tube with a small flame until almost melted. Quickly stretch the tube
to draw the center down to a very small diameter.
Cut the tube in the center to form two tubes with tapered
nozzles. Trim the end of the nozzle to the desired ID. An ID as small
as .002" is easy to obtain. The nozzle will reach deep into very
small holes to administer only one small drop of tapping fluid, WD-40, oil,
amalgamated moose juice, etc.. I have several of these bottles and
constantly use them to lubricate drills, taps, saws, and cut off blades.
Bob Shores
Ruskin FLA |
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TIP 5 CHECK VALVE
Often builders are required to fabricate a check valve for use in fuel lines.
The valve has a small "inlet" hole, a larger "chamber"
hole that retains the ball and an "outlet" hole. Usually no data is
given and the builder must use his own judgment about sizes.
Here is the data I use for check valves. The inlet hole is 75% of ball
diameter. The chamber hole is 135% of ball diameter. The outlet hole is
usually .125" for 1/8" OD brass tubing. A tab can be formed in the end
of the tube and bent over to act as a ball stop.
If
the inlet hole is too small, engine vibration will dislodge the ball. If too
large, the ball will stick. I am sure there are other combinations, but this
one is easy for me to remember.
Bob Shores
Ruskin FLA |
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TIP 6 PISTONS/RINGS
Much has been written about
producing pistons and rings. I have tried every method I am aware of. One
thing I have learned is that when someone starts to tell me how to make
piston rings, I stop him and ask him to crank up his multi cylinder engine.
If there is smoke in the exhaust, I ask why he did not make a good set of
rings for his own engine.
Over the past many years of
reading and patently listening to men explain how they make pistons and
rings, I have slowly developed a procedure that consistently produces pistons
and rings that fit and work well ,,, for me. For lack of a better tag, I call
it the Shores Procedure. Here is my procedure to produce Cast Iron pistons,
rings and cylinder liners.
Close grained, centrifugally
cast, Cast Iron is my choice for these items. Good engineering rejects all
other metals with the exception of Aluminum for the piston. First, fabricate
the cylinder liner by boring it to ID minus .003". Install the liner in
the block. Do not use a hone as this will only increase eccentricity and
taper. Lap the liner with an expandable Aluminum lap. The length of the lap
should be 3/4 of the liner length. Use Clover Leaf fine grinding compound,
available at most Auto Parts stores. Do not put Diamond dust in your engine.
Diamonds are forever.
The particles in the grinding
compound are manufactured to crack apart in use, leaving sharp edges, thus
the compound will diminish in size and fresh compound will need to be added
during the lapping process. Lap to a mirror finish. Do not
leave herringbone scratches to retain oil for the piston. Rarely does a
piston lack oil, the PROBLEM is to prevent oil migration from the oil
pan, around the piston and into the combustion chamber.
To
produce the piston and rings, chuck a short length of Cast Iron and turn a
3/8" OD spigot about 3/4" long. The spigot will serve as a
"handle" to hold the work. Chuck by the spigot and turn to piston
OD plus .003". Cut the ring grooves .003" deeper than specified.
Drill and bore the ID, leaving the skirt long enough to part off 2 or 3 rings
later.
Grip
the spigot, horizontally in the mill vise. Drill and ream the wrist pin hole.
Grip the spigot vertically in the mill vise. Insert a temporary rod through
the wrist pin hole to align the piston. Mill the slot for the rod. Chuck
the spigot in a 3/8" VSR hand drill and lap the piston with a
compressible Aluminum lap to be a snug fit in the cylinder, certainly not
loose, but not overly tight. Remember that from this point on, the piston
will only get smaller.
Back in the lathe, part off the rings. Before you completely part a ring
off, lay a fine file over the groove and remove any burr raised by the cut
off tool. Stroke both sides of the ring on 600 grit paper on a flat surface.
Wrap this paper around a rod and de-burr the ID. Be sure the rings fit the
groove in the piston. Part off the piston.
Grip most of the ring in the mill vise. Pad both sides with thin soft wood
and do not over tighten. Use a circular saw blade, about .006" to saw
the ring into. At this point, you are assured that the ring is a perfectly
circular and that it fits the piston and cylinder liner.
The ring needs to be "sprung" open so that it exerts a slight
pressure against the cylinder liner walls. To spring the ring, the
circularity must be altered, certainly not anywhere near the gap but at it's
natural flexure point, which is directly opposite the gap.
To
do this, lay the ring on a flat, powerful magnet. Place a square steel bar in
the gap. Arrange the ring so that the area opposite the gap is off
the magnet. The magnet will securely hold the ring and bar and also act as a
heat sink. Use a small Butane torch to heat the area directly opposite the
gap to a dull red color.
The Shores method prevents the use of special fixtures, an oven to heat the
ring to high temperature that certainly distorts, warps and scales the ring.
Also, the ring is gapped without manual breaking or chopping it into with a
cold chisel and the working surface of the ring is free of tool and file
marks. Certainly there are other methods and the prudent builder will use the
one he is comfortable with, without knocking his buddies method.
Bob Shores
Ruskin FLA
This is Bob’s technique, there are others some simpler and some more complex. If you ever see one of Bob’s engines start and run, you must agree that what he does works. David |
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TIP 7
A
MINIATURE COMPRESSION TEST
Occasionally,
ones curiosity can be satisfied by actually measuring the compression of a
small gas engine. Especially on multi-cylinder engines where it is difficult
to determine which cylinder is not "up to snuff". If you enjoy
building small tools, here is a nice project for your tool box. I found a
small pressure gauge in my junk box, the type used on small steam engines and
boilers, and decided to build a compression tester shown in the accompanying photo.
The drawing that also accompanies this TIP is self explanatory. A
1/2" hex brass bar is gripped in the lathe 3 jaw, drilled and tapped 1/8
NPT to accept the back connected, 1" OD, 100 PSI pressure gauge. The bar
is then drilled deeper and tapped 10-32. A smaller drill is used to drill
through. Gut an old 1/4-32 sparkplug or glow plug. Turn the stem of the
tester down so that the end slips in the sparkplug body. Silver solder the
plug to the stem. The ball check should be close to the end of the plug body to
prevent enlarging the combustion chamber during test. Drop a
steel ball inside, then a weak spring. Anneal a 10-32 setscrew, drill a small
hole through it and install the setscrew to place a little tension
on the ball. Install the gauge with some pipe dope on the threads and
you are in business. A drop of oil on the ball will usually seal a very small
leak. Some
builders may note that air can be trapped between the ball check and the
gauge. Not to worry. My ex-friend Pete, while sitting in his bathroom, had a
stroke of genius. Pete suggest that after the test is made, the ball is
momentarily moved off it's seat and the gauge will automatically go to zero.
Pete also suggest that you use the plastic tip of your shoelace to do
this.
Click here for a larger drawing
that may be printed. Bob
Shores Ruskin
FL |
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TIP-10
Fuel
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TIP-10
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TIP-11
BOB'S BOBBER
When I was a lad, a long tailed dog followed me home. My Dad cut off his
tail, renamed him Bob and said that I could keep him. I learned a lot about
Bobbing and Bobbers that day.
Today, I order most of my small bolts as long as I can get them as I usually
have to Bob them for my use. I made a Bobber that I find very useful to
quickly, easily and professionally alter the length of small bolts. Here's
how:
Drill a series of holes down the center of a 1/8" X .750" X 2" steel bar.
Tap the holes 1-72, 2-56, 4-40 and 6-32.. To use the Bobber, screw the
bolt through the Bobber, use a nut, washers or spacer to position. Grip the
Bobber in the bench vise and use a large sharp file to quickly remove the
excess length. The Bobber will act as a "File Button" to ensure the end is
flat and even with the Bobber. Many bolts can be quickly Bobbed to the same
precise length. For extra long bolts, Grip the end of the bolt in the vise,
hacksaw it away then file flat to the Bobber.
The Bobber can be 1/4" thick and tapped to any thread desired. Take a few
minutes to make one and you will find it a nice addition to your tool box.
Bob Shores
Ruskin FLA |
TIP-12
Hall Sen
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TIP 13
DEAD DOG
When turning work between centers, such as turning a
crankshaft or camshaft, the clanging and banking noise that the lathe
dog makes in the faceplate is very annoying. To reduce this noise by
about 98%, I made a device that I call a Dead Dog. I chose this name as
I was using a Dead Center at the time.
The device is a lathe dog made from two pieces of square
stock with a threaded tang that sports a threaded cylinder with an OD
that fits nicely into the faceplate slot. Since there is very little
"slop" between the cylinder and the faceplate, the noise is gone.
Commercial lathe dogs have a teardrop shaped tang, making it difficult
to fit it with a "Snubber".
 I
made three of these bar clamp style dogs, one with 5/16" stock, one with
3/8" stock and one with 1/2" bar stock. The clamp bolts can be hex head
or socket head. The clamp bolt are about 1" apart on the 5/16" dog.
Rather than give specific dimensions, the attached photo explains all.
These Dead Dogs are quick and easy to make and you will find other uses
for them
Bob Shores
Ruskin FLA
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TIP 14
Clamp Type Rod
The clamp type rod offers so many advantages that I chose this design
for the Pacifier V 4 engine that I am building. The small amount of time
and labor to make this type of rod makes engine assembly and disassembly
a more pleasant experience. The two photos below show the design.
Five of these rods were made (1 as a spare), from 6061-T6 Aluminum to
fit within .625" OD pistons. The cap bolts are 2-56 and the clamp bolt
is 0-80. The .006" wide slot was sawn with a Jewelers circular saw blade
given me by Jerry Keiffer. The threaded cross hole was counter drilled,
by hand, with a No. 53 drill in a pin vise. A thin piece of brass shim
stock was placed in the slot to prevent the clearance drill from going
too deep.
Wider slots can be sawn with no ill effect. Very little torque is
required on the 0-80 bolt to firmly clamp the wrist pin. Here are some
of the advantages:
Actually, the time and labor to make a clamp type rod is offset by the
time and labor to accommodate a typical tang eye type rod.
Bob Shores
Ruskin FLA
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TIP 15
COMPRESSION PROBLEMS 10 Compression, or the lack of it, continues to be the most common problem when builders contact me for assistance. This prompts me to post TIP 15 that hopefully will benefit some builders. Compression problems can be on either side of the head gasket, so, let's start on the underside by checking the CYLINDER/PISTON FIT.
Remove the head. Place a few drops of fuel on the top of the piston and run it up and down a few times leaving the piston at the top of it's stroke. Remove excess fuel with a napkin. Place your thumb or the heel of you hand over the cylinder and move the piston down. A very strong vacuum should occur against your hand.
The length of time that the vacuum exists is an indication of cylinder/piston fit. The vacuum will remain for many minutes when the cylinder and piston has been properly lapped to a snug fit. The vacuum will disappear in less than a second if the lapping job or the fit is poor. Good compression cannot be expected with a poor fit. If the vacuum remains strong for 10 seconds, or longer, the fit is acceptable and you can expect the compression to be good.
I do not expect the rings to seal the piston until they are "broken in" (with a few hours of running time) and then only when the piston is moving fast. Remember that a "snug" fitting piston will run hot until it has broken in so, run the engine in short burst, for the first hour, to prevent overheating. Certainly, the piston will wear more at the top as this is the hottest area when running.
If you are building a slow running (less that 1000 RPM) and a cool running (less than 170 degrees F) engine, a cast iron cylinder and piston is the best choice due to it's coefficient of expansion and natural (carbon) lubricating characteristics. With this setup and a little WD-40 in the fuel to suspend carbon particles, rings are not required for good compression during the first 1000 hours of running time.
Above the head gasket. Valves are the most common problem. The valve stem should be lapped and the head should be concentric with the stem for an easy valve grinding job. I use 300 grit compound to grind valves. With a tight fitting rubber tube forced over the end of the stem, twist the valve back and forth with your thumb and forefinger while slowly rotating the valve. DO NOT use a drill or machine to rotate the valve. After the stress of machining, a valve can be expected to warp or bend a bit with temperature variation. Using finer grit will not allow the valve to quickly seat itself if it warps a tiny bit when the engine first runs.
ALWAYS use virgin Teflon for head gaskets. It is cheap, readily available, will not "blow", requires no gasket compound, will not stick to metal and will "creep" into surface imperfections. Use brass tubing, sharpened at an inside angle, as core drills to cut bolt holes. Larger core drills (thin wall mild steel cylinders) are easily turned with the lathe.
Sparkplug holes should be drilled, tapped and counter sunk (usually with an end cutting end mill) in one operation. The end of the sparkplug should be flush with the inside of the combustion chamber. Anything else is poor design. Always be sure the head bolts are short enough to actually clamp the head down. To determine precisely when, or if, a valve closes, remove the sparkplug, place a rubber tube over the exhaust pipe and blow on it. You cant blow through a closed valve.
As always, I hope this little TIP is useful or that it serves as an alternate method for some builders. Am I getting to long winded with the TIPS ?
Bob Shores
Ruskin FLA |
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TIP
16
INKPLATE 11/16/2003
Having built the bridge type inlet manifold for my V-4
engine, I desired to paint it Jet Black, with a high gloss, hard and
durable finish. I also desired to do this quickly.
The manifold was made of cold rolled steel with stainless
steel flanges that are Silver Soldered on, presenting a dissimilar
metals problem.
The procedure was to finish the surfaces with 400 grit
Wet-or-Dry and wash the manifold in Acetone. Using a large Felt Tip Pen,
one coat of permanent black ink was applied to all surfaces. The Ink
dries in seconds. The manifold was impaled on a rod held in the jaws of
a VSR electric drill and rotated slowly while a light coat of Automotive
clear lacquer (available at Auto Parts Stores) was sprayed on and it
dried to the touch in 3 minutes.
The manifold was then suspended over a temperature
controlled Hot Plate at 130 Degrees for 20 minutes. The result was a
very black, hi gloss, hard, durable finish. I intend to apply two more
coats of clear lacquer in a week. The entire process, from surface prep
to bolting the manifold on the engine required less than 1 hour of time.
To distinguish this process from others, I call it Bob's
INKPLATE process. INKPLATE seems to
work well on Brass, Aluminum, Silver Solder, Stainless, or a combination
of these metals.
I have not had time to experiment with other methods of
treating the metal, such as abrasive grit size, sandblasting, buffing
compounds, etching, etc.. Also, I have not tried other colors of ink
such as Yellow, Blue, Green or iridescent colors.
INKPLATE seems to be a neat way to put a
good paint job on very small parts. If you try the INKPLATE
process, or experiment with it, give me some feedback on your
procedure/results on the Message Board.
Bob Shores
Ruskin FLA |
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TIP 17
TAP DISK 11/28/2003
Difficult to believe that I have not
posted a tip about my Tap Disk. Every shop should have one , and use it,
to prevent small tap breakage. I have not broken a tap within the past
10 years while using my Tap Disk and I constantly use tap sizes 0
through 6. Take a few minutes to make one, try it and I am sure you will
opt for this taping method whenever possible.
THE DISK
Turn
an Aluminum disk, 1 1/8" OD, knurl it, center drill .144" and part it
off .325" thick. Drill NO. 43 from the OD to the ID and tap 4-40.
Install a 4-40, hex head bolt, .750" long.
TO USE
Insert the tap in the Tap Disk to it's
mid point. Tighten the bolt with a 1/4" wrench. Drill the hole to be
taped in the Drill Press, Mill or Lathe. Remove the drill, fill the hole
with WD-40, or your favorite taping fluid and grip the upper half of the
tap in the chuck, just loose enough to turn freely. Lower the
spindle/tap to the work. Use your thumb and forefinger to tap the hole.
The photo below shows the Tap Disk ready to use.
Bob Shores
Ruskin FLA |
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TIP 18
HUB CLAMP 1/24/2003
WHENEVER POSSIBLE, USE A SPLIT HUB CLAMP TO MOUNT YOUR
FLYWHEEL AS IT ELIMINATES KEYWAYS, KEYS, SETSCREWS, PINS,
WHEEL PULLERS, HAMMERS, DAMAGE TO THE CRANKSHAFT AND CUSS
WORDS. THE PHOTO BELOW SHOULD CONVEY THE DESIGN BETTER THAN
WORDS.
INSERT A SHIM IN THE CROSS SLOT BEFORE DRAWING THE HUB INTO
THE FLYWHEEL WITH A BOLT, NUT AND WASHERS TO PREVENT BENDING
THE HUB. VERY LITTLE TORQUE IS REQUIRED ON THE BOLT TO
REALLY GRIP THE CRANKSHAFT.
BOB SHORES
RUSKIN FLA
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TIP 19
CROSS THREAD 2/16/2004
WHEN
INSTALLING BOLTS OR SCREWS, PRESS DOWN LIGHTLY AND TURN IT
COUNTERCLOCKWISE UNTIL YOU FEEL IT "CLICK" THEN, TURN IT CLOCKWISE.
THIS WILL PROPERLY ENGAGE THE THREADS. IF YOU MAKE A HABIT OF THIS, A
CROSS THREAD ACCIDENT IS REMOTE.
BOB SHORES
RUSKIN FLA
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TIP 20
Boring Head 3/28/2004
I COULD NOT USE THE 2" CRITERION BORING HEAD
(I HAD PURCHASED FOR $100.00) IN MY BARKER BENCH MILL AS IT
IS TOO LARGE AND TOO LONG. I BUILT MYSELF A NICE BORING
HEAD BY SCALING THE CRITERION DOWN TO 1.35" OD WITH A SHORT
1/2" SHANK. IT ACCEPTS 3/8", 5/16", AND 1/4" BORING BARS.
IF I MADE ANOTHER, IT WOULD ACCEPT 1/2" AND 1/4" BORING BARS
ONLY. THE ADJUSTMENT BOLT IS THREADED 1/4-40 SO THAT ONE
TURN MOVES THE BAR .025". THE RESULT IS AN EXCELLENT BORING
HEAD FOR SMALL MILLS. I MADE IT FROM MILD STEEL BUT WOULD
USE 303 STAINLESS IF I MADE ANOTHER. IF YOU HAVE A SMALL
MILL, IT IS WELL WORTH THE TIME TO MAKE THIS BORING HEAD AS
IT IS A NICE CONSTRUCTION PROJECT.
BOB SHORES
RUSKIN FLA
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Silver Angel Cam
Fixture
5/28/2004
The cam grinding fixture for
the Silver Angel has been a topic of recent discussion.
It appears older versions of the plans included the fixture
and newer (black and white) versions are missing this
detail. There is a thread in Construction Questions
about this fixture.
Click here for a larger version that you can print Steve Peirce got Margaret's permission to draw and post the drawing. |
Copyright 2004, Florida Association of Model Engineers, All
rights reserved.