Boundary Layer (Tesla) Turbine Mark-II Page
The Tesla Boundary Layer Turbine, Mark-II
bigger! prettier! maybe even better!!
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What It Is?...
(c.a., January 2008)
I've been pleased enough with how my six-inch turbine works to start thinking
a while back about building a bigger one. In "Tesla lore" there seems to be
a near mythical ability turbine with a, depending on where you read about it,
11.5" or 11.75" diameter runner. So, I decided to make one with 11.625" runner
discs. And, in fact, began working on it some time before starting a web
page to describe it.
This is still an air powered, test bed device, so, although much prettier than
the six-inch unit, includes features that make it easy to disassemble and
reconfigure. The most significant feature not found on the six-inch turbine is
a slotted shaft which allows testing different styles of runner discs and star
washers without having to do a complete "glue up" of another runner. The discs
and star washers are made with key tabs that slip into the shaft slots, and the
runner stack is clamped together by nuts on both sides, which are screwed onto
the treaded ends of the slotted portion of the shaft.
Complete construction and testing information for the Mark-II turbine
will be made available as work progresses. But, before starting this page, I
decided that putting all the construction technique details onto one page along
with theory and testing results was getting in the way of telling the story in
an easy to follow manner. Hence, I established my
Miscellaneaganza! page as a place to
collect all construction technique details for reference. The page you are
reading now will present the major construction steps of the Mark-II turbine,
with the bulk of the details made available via links embedded in this page's
text that will open related sections of the Miscellaneaganza! page in separate
browser windows (or tabs, depending on your browser configuration) for those
interested in more information. That leaves this page free to concentrate on
theory, testing, and analysis results without losing them in the details.
Future work on my other pages will move towards this presentation style as
well, and utilize the
Miscellaneaganza! page for details.
(c.a., December 2006)
The Mark-II turbine volute was formed by heating and bending a flat 2.5" wide,
0.091" thick, approximately 38" long acrylic plastic
strip into a
ring. The plastic strip was
bent around a turned, laminated wood
form 2.75" thick with an 11.75"
outside diameter. The turned ring was screwed onto a 12.5" square piece
of 0.5" thick plywood; providing a base to align an edge of the plastic strip
against as the strip was bent.
(c.a., May 2007)
Heating the plastic for bending was accomplished using a 1500 W heat gun with
an attached wire whose length indicated the distance to hold the gun from the
plastic to achieve the appropriate no-rebound
forming temperature. The
forming temperature distance was
calibrated using an oven
thermometer. For cast acrylic plastic sheet of the
Plexiglas™/Lexan™ variety used here, the no-rebound forming
temperature ranges between 320° F to 356° F
Here, the calibration distance was chosen to select approximately 325° F.
Working with the end of the indicator wire next to, and the wire perpendicular
to, the surface of the plastic strip, the "calibrated" heat gun was used to
maintain the forming temperature at the surface of the strip during the
bending process. As the
bend progressed around
the forming ring, the plastic strip was lightly clamped in place with small
wooden blocks and c-clamps to allow cooling without deforming.
The volute ring was
closed by clamping its
overlapping ends onto the wooden forming ring, cutting though the ends with
a thin-bladed hacksaw, and filling the resulting saw-kerf gap with 5-minute
Edges and Sides:
(c.a., May 2007)
To give rigidity to the Mark-II turbine volute ring, and provide a place
to mount the turbine side pieces, two acrylic plastic rings were
turned from 0.236" thick
material to have the same inside diameter as the outside diameter of the
volute ring and an outside diameter approximately 2.5 inches greater than
that. One was attached
to each edge of the volute ring using high-strength epoxy glue.
Prior to turning, the rough
cut plastic blanks used for the volute stiffening rings, as well as those used
for the turbine side pieces, were aligned in a
jig and had size 6-32
threaded brass inserts, (the
type used for providing metal threads in wood), embedded in 5-minute epoxy in
six holes equally spaced at 60° drilled 0.625" inside the final diameter
scribed on the blanks.
Before attaching the plastic blanks to be turned, the alignment jig was mounted
on the same turning
fixture used to spin the
wooden blank turned into the volute bending ring.
To ensure alignment of the brass inserts between each plastic blank, the
inserts in the other blanks were installed with the first
blank in place
on the alignment jig, and the alignment screws threaded though its inserts.
With the second set of inserts thus aligned with the first, the second
set was epoxied in place.
With threaded inserts installed in the two ring blanks, and 6-32 thread holes
drilled in alignment with the inserts in a
third blank to be used as a
turbine side plate, the three blanks were mounted on the alignment jig,
with the two ring blanks closest to the jig face.
Before placing the side plate blank on top of the stack, the paint stirrer
compass was used to scribe
a centered circle on the exposed ring blank face of the same diameter as the
outside diameter of the turbine volute ring. The side plate blank was then
set in place, the blank stack screwed to the alignment jig, and the compass
used once more to scribe a circle defining the finished stiffening ring
outside diameter on the exposed side plate blank face. With turning marks
scribed, and all three plastic blanks attached to the alignment jig, as a
unit, the alignment jig and rough cut plastic blanks were all
trimmed using a jigsaw
to just outside the visible scribed circle. With that the alignment jig was
mounted in a lathe, and all three blanks were
down simultaneously to their final outside diameter. After turning, a small
registration hole was
drilled through all three blanks near and slightly inside the radius of one
of the 6-32 thread mounting screw holes as an alignment aid for later
Removing the completed side plate blank from the alignment jig and
the attachment screws through the stiffening ring blanks allowed the two ring
blanks to be simultaneously
bored on the lathe
to identical inner diameter, given by the previously scribed turning limit
circle on the outer ring blank face.
To facilitate testing different width runner assemblies, a side plate
small enough to slip
inside the turbine volute ring was turned on the alignment jig. The outer
edge of this side plate was
grooved accept an o-ring,
(made from thin automotive vacuum
hose), to seal it against
the inside of the volute.
(c.a., June 2007)
After construction of the stiffening rings and side plates, a stiffening ring
attached to each edge of
the turbine volute ring using high-strength epoxy plastic weld glue.
(c.a., July 2007)
With the volute stiffening rings permanently in place, a set of
stand offs was constructed
to fix the distance the small side plate sits inside the turbine volute ring.
A second full-size side plate was also constructed. Assembly for both the
small plate and the
second full-size plate
included installing 6-32 threaded brass inserts.
(c.a., May 2007)
The Mark-II turbine
base is basically an all
wood construction. The turbine volute ring sits on two commercially obtained 8"
long pinewood shelf brackets,
modified into volute
mounting brackets by making rounded cutouts in their corners to fit the volute
ring. The volute ring brackets are mounted on a sheet of 0.5" thick commercial
laminated pine board 24" long by 18" wide.
(c.a., June 2007)
A close fit of the volute ring to its mounting brackets' cutout areas was
accomplished in two
steps. First the cutouts were
sanded smooth and square using a drum sander mounted in a drill press. Second, a
thin layer of sawdust-and-glue mix type wood filler was applied to the upward
facing curved cutout areas, strips of waxed paper laid over the wood filler to
prevent sticking, and volute ring pressed down into the filler to form exact fit
surfaces on the mounting bracket cutouts. This process set the final distance of
the bottom of the volute ring off the turbine base plate to approximately 2".
(c.a., July 2007)
A temporary axle was used to facilitate aligning the Mark-II turbine axle
support uprights. Prior to using the alignment axle, the base assembly had to be
prepared for installation of the axle supports. That process included final
placement of the volute ring mounting brackets on the turbine base plate, and
alignment both vertically and horizontally of the volute ring relative to the
turbine base plate, as well as cutting pockets for insertion of the axle support
uprights into the turbine base plate.
The volute mounting brackets were
aligned with a straight edge
and the pair set centered on and screwed to the turbine base plate at the proper
distance apart to accept the volute ring. Two identically marked spacing
boards were used to align the
volute ring horizontally on the base plate, and a carpenter's
square was used to align the
volute ring perpendicularly to the base plate. A thin coat
of sawdust-and-glue type wood filler was smeared over the volute mounting
bracket support surfaces, the
filler covered with waxed
paper to prevent sticking, and the volute ring set in the alignment fixtures and
pressed into the wood filler to create the final aligned volute mount surfaces.
After the wood filler hardened, the volute ring was
marked for drilling four
mounting holes over each volute mounting bracket support surface with a pattern
to make it impossible to mount the volute ring other than as it was oriented
at the time the marks were made. Without moving the alignment fixtures, the
volute ring was lifted from its mounting brackets, and, using wooden soft
jaws to hold it in a large
vice, the marks on the volute drilled through and counter sunk for #6 flat head
screws. The volute was set back in the mounting
brackets and alignment fixtures, and the drilled holes in the volute used to
mark the mounting bracket support surfaces for drilling
pilot holes for the
volute mounting screws. The volute was again lifted from its mounting brackets
so the mounting bracket pilot holes could be drilled, then set back down once
more and screwed in place with #6 flat head brass wood screws. With the volute
ring mounted in place, the
alignment fixtures were removed.
(c.a., September 2007)
To add rigidity, and provide
support for the turbine runner axle uprights, the volute ring and its mounting
brackets were removed and the turbine base board, and the base was
ringed around its bottom side
with 4" wide pine board 0.5" thick. All four corners were then rounded to a 3"
radius using a jigsaw followed up by a drum sander mounted in a drill press, and
the top edges shaped using a 0.25"x0.625" bearing-aligned Roman
Ogee bit mounted in a
woodworking router. The mounting brackets and volute ring were then reattached
to the reinforced base
Finding your center:
After the volute ring was aligned on the turbine base, a
involving cutting a
cardboard disc to fit the
volute ring and marking the disc with
through its center, was used to find a line on the turbine base directly below
the center of, and parallel to the face of the volute ring with a carpenter's
square. This line provided
an index for setting the axle support uprights in place.
During the center finding process, the perpendicular lines on the cardboard
alignment disc were used to put vertical and horizontal center-line
marks on the volute
stiffening rings. As an aid for later alignment of holes in the axle upright
supports, one of the horizontal marks on the stiffening rings was used to mark a
square-cut piece of
cardboard to indicate the
height of the geometric center of the volute ring above the turbine base plate.
To mount the turbine runner axle support uprights, the volute ring and mounting
brackets were removed, and a
pocket was cut near each
side of the turbine base plate, of the appropriate size for a close fit on the
end of a 4" wide by 0.75" thick oak board.
Lines for the pockets were
marked so that their inner edges would align with the inner edges of the under
base stiffening boards on either side of the base plate and their long edges
would be perpendicular the line previously drawn to indicate the projection of
the center of the volute ring onto the base plate.
A router jig was
constructed and used to cut the 4" by 0.75" pockets, using a plunge router with
a 0.375" straight cutter. The jig was aligned to set the 4" sides of the pocket
perpendicular to and centered on volute ring center line, and also aligned with
the previously drawn edge alignment marks. This set the wide faces of boards
inserted into the pockets to be parallel to the faces of the volute stiffening
rings, as well as directly opposite from each other and centered on the center
line of the turbine volute ring. The
pockets were cut to a depth
of approximately 0.25" into the under-edge stiffening boards. A thin, sharp chisel
was used to square the rounded corners of the pockets for the final fit of the
uprights into their pockets.
After the first pocket was cut, the square-cut
piece with the volute ring center line height marked on its edge was used to
determine the proper length for the axle support uprights, and two appropriate
length pieces cut from the 4" by 0.75" oak board. The jig was then aligned on
the other side of the turbine base plate and the pocket cut for the second axle
After the router jig was removed, the axle support uprights were
shaped to their final form
and inserted into their base plate pockets. Then, the volute mounting brackets
and volute ring were reinstalled on the base plate. The volute mounting brackets
were permanently attached with glue and screws, but, the uprights were left free
to be removed.
For preliminary axle alignment, two runner
discs with 0.5" diameter
center holes were cut from 0.091" thick acrylic plastic sheet and mounted on
a 0.5" diameter US standard thread rod temporary axle, with their outer faces
separated by approximately 0.5" less than the distance between the outer faces
of the volute stiffening rings. With one axle support upright removed, the
runner assembly was
centered in the volute ring on thin cardboard spacers and positioned on the
threaded rod axle so one end of the rod touched the face of the remaining
support, allowing the location to drill the axle hole in the support to be
marked around the end of the axle shaft. The procedure was repeated for the
opposite side upright, and the marked hole positions drilled to 0.5" diameter.
The two disc runner assembly was then centered on the temporary axle rod, and
the axle rod installed in the axle support uprights to check the preliminary
For final alignment the runner assembly needed to be able to spin freely in the
volute ring. To that end, the ends of the temporary
axle rod were turned down
to fit in 0.5" outside diameter brass bushings inserted into the 0.5" holes
drilled in the axle support uprights.
With the axle able to spin freely, the axle support uprights were clamped to
square cut blocks, and the blocks clamped to the turbine base plate. The axle
supports could then be tapped with a rubber hammer until the runner discs
were able to spin freely in the volute ring without rubbing. Then, since the
axle support pockets were cut to align with the inner edges of the under-base
stiffening boards, brass
shim material could be
inserted under the uprights to set their position, and screws used to fix them
in place against the shims.
(c.a., September 2007)
The finishing steps for the basic Mark-II turbine assembly included applying
a dark mahogony
stain and polyurethane
varnish finish, adding
rubber feet to the
underside of the base, changing the assembly screws and washers to
brass hardware, adding
black-iron gussets between
the axle upright supports and the turbine base, and making locking
collars to use on the axle
ends to retain the runner assembly within the volute.
(c.a., June 2007)
As a rule, projects involving machining and glue-up are fraught with danger for
shiny acrylic plastic surfaces. And, constructing the Mark-II turbine volute was
no exception. Once the volute ring and stiffening rings were formed and glued
together, there were a number of dings, scratches and globs of glue that needed
cleaned up. In fact, for a
reasons, the volute surfaces
were particularly badly damaged, and required more effort to restore than might
normally be expected for a plastic working project.
Restoring the surfaces was a four step process. First, a small sanding drum in a
Dremel™ tool was used with 80 grit sanding cylinders to knock down the
worst of the excess glue and also to
feather out the more serious
gouges. After grinding, the surfaces of the volute were
dry sanded by hand, stepping
up through several successively finer grades of paper ranging from 80 grit to
Once grinding and dry sanding was completed the next step in refinishing was
wet sanding. The wet sanding
process moved though several grades of paper ranging from 600 grit to 1600 grit.
An electric orbital sander was used for most of the wet sanding. It was
necessary to make an extended paper mounting
block to gain access to the
space between the volute stiffening rings with the electric sander.
Once the final grade of wet sanding was completed and the sanding residue
cleaned off, the volute ring was smooth and clear, but, did not have the luster
expected of an acrylic plastic surface. To bring back the shine two grades of
stick-type rub on polishing
compound (#3 and #6) were
applied to the volute and polished with muslin buffing wheels chucked in an
electric drill. And, finally the volute was cleaned and polished with
spray on acrylic polish.
Slotted Axle/Keyed Runner:
(c.a., December 2007)
The key-slot axle and keyed runner discs were constructed using a series of
jigs employing a Dremel™ tool router with a 0.25" straight cutter. The
central element of the key-slot
axle assembly is a length of 0.375" diameter US standard threaded rod, which
acts as the axle between the axle support uprights. The key slots were cut into
a 0.825" diameter 5" long PVC rod,
turned from a rectangular PVC
block, which was drilled and
threaded through its center
to allow it to be screwed onto the 0.375" threaded axle rod.
A set of wooden soft
jaws were constructed for
working with the 0.825" PVC rod in a vice, and utilized first in
threading the ends of the
rod for 0.825" US standard nuts. The threads are for nuts to compress and
retain runner elements on the PVC shaft once the necessary
slots and keys have
Again using the soft jaws, a length of 0.375" threaded rod was screwed through
the 0.825" PVC rod by turning a wrench against a set of
double nuts on the
threaded rod. This made the PVC rod ready for slot cutting.
The first of the key slot jigs was a set of guide rails constructed from
hardwood strips that the
Dremel™ router, mounted on the
arc-cutting jig used in
constructing the six-inch turbine, could be slid down,
aided by a pair of aluminum angle material rails mounted on the bottom of the
arc-cutting jig. This assembly allowed cutting a 0.25" slot on center down the
0.825" PVC rod. The hardwood guide
rails were spaced apart by
around two spacer blocks, with the spacer blocks sandwiching a 0.25" thick piece
of aluminum bar. With the guide rails screwed down to a base board, the spacers
between them, separated by the aluminum bar, formed a 0.25" wide slot exactly
centered between the guide rails that was used to
center the router cutter
between the guide rails, allowing the aluminum angle pieces to be marked and
attached to the bottom of the
arc-cutter jig to keep the arc-cutter jig on center as it was moved along the
hardwood guide rails.
The 0.825" PVC rod was centered between the hardwood guide rails by lightly
clamping it down on 0.5"
rods set between the guide
rails, and cutting slots to fit over the 0.375" threaded rod in the center of
the PVC rod in two 0.125" thick pieces of 0.75" wide steel
bar. The steel bar pieces
were screwed to the ends of the hardwood guide rails, and nuts tightened against
retain the PVC rod firmly on
center between the guide rails.
A clamping block was screwed to the bottom of the jig so the jig could be set on
top of and firmly clamped into a large vice. The height of the Dremel™
router cutter was adjusted to
clear the retaining nuts, and
the first slot cut.
To cut the second slot exactly
180° around the PVC rod
from the first slot, two pieces of the original hardwood spacers and a piece of
0.25" aluminum bar were
cut down to fit under one of
the 0.125" thick steel retaining bars. The 0.825" PVC rod was loosened and
rotated approximately 180° in the guide jig. Then the cut down wooden
spacers and aluminum bar were used to
align the first slot exactly
on center in the jig by sliding the aluminum piece into the first slot, and
using the spacers to center it between the guide rails, forcing the slot to
center. With the first slot properly aligned, the retaining nuts were tightened,
and the second slot was cut.
To lock the runner discs to the axle key slots, the runner disc axle holes were
enlarged, on center, from
0.5" to 0.825" diameter to fit over the 0.825" diameter PVC rod. Then, through
a series of steps, two 0.25" wide tab slots were cut approximately 0.375" deep
into both runner discs' center holes to align with the slots in the 0.825"
diameter PVC rod section of the axle assembly. First, using a PVC
fixture consisting of a
0.825" diameter disc about 0.5" thick with a 0.25" diameter stob about 0.75"
long extending from the center of one of its faces, one of the runner discs was
centered around a 0.25"
diameter hole drilled in a board large enough to support the disc. After the
disc was centered it was clamped down, the fixture removed, the 0.25"
cutter of the Dremel™
inserted into the 0.25" hole in the support board, and a piece of aluminum
angle material set against the router and clamped across the disc to provide a
guide for the router to cut
tab slots into the center hole aligned with the geometric center of the disc,
180° apart, and, hence, unavoidably
aligned with the key
slots in the PVC axle piece.
With tab slots cut in the first disc, the second disc was placed on top of the
first disc, and both discs
registered together using a
screw with nut through one hole pair from the rings of assembly holes near the
outer diameters of the discs. The pair of discs was centered over the 0.25" hole
in the support board, again using the PVC fixture, with the second disc against
the board. Then the discs were
clamped to the support board,
the alignment fixture removed, the Dremel™ router 0.25" cutter extended
into the 0.25" hole in the support board, and the aluminum
angle piece set against the
router face and clamped to the runner discs. For this operation, besides
centering the router over the discs' axle holes against the aluminum angle
piece, the angle piece was adjusted so that the router cutter
slid cleanly back and forth
along the angle piece into both tab slots in the upper disc. Then, without
removing the upper disc, tab slots were
cut into lower disc. Because
of how the discs were registered together, not only are the tab slots in both
discs aligned, but, so are the assembly holes in both discs relative to the tab
After the key slots and tab slots were cut, a
jig was constructed for
cutting a precise 0.25" wide
strip of 0.091" thick acrylic
plastic sheet to be used for the
tabs to extend from the tab
For four passes, the 0.25" strip was
rounded on its end to fit the
rounded end of the
tab slots in the runner discs
and cut to length to extend from the tab slots into the
key slots on the 0.825" PVC
axle slot rod. The four rounded strips were then
glued in place in the runner
discs to create the key
tabs necessary to lock the
runner discs in place on the key slotted axle shaft.
The inside diameter of a
length of so-called 3/4" PVC pipe fits (a bit loosely) over the 0.825" diameter
PVC key-slotted rod section of the runner axle assembly. So, three sections of
the pipe were trimmed in a
lathe for clamping the runner
discs in the center of the
volute when the axle was assembled and installed in the turbine axle support
Rather than use the
bushing from the temporary
alignment axle, pockets were cut in the
volute side of the axle support
uprights, centered over the original 0.5" alignment axle bushing holes, to allow
insertion of 1.125" outside diameter ball
bearings. To cut the pockets,
the volute ring was removed, and an electric hand-drill angle
boring jig with the angle set
to 90° clamped to an upright,
centered with a 0.5" forstner
bit through the original 0.5" diameter hole, then the 0.5" forstner bit changed
out for a 1.125" forstner bit and the
pocket cut to a depth equal
to the thickness of a bearing. The same method was used to expand the remaining
portions of the original 0.5" holes to 0.75" to allow the ends of the axle shaft
to extend through their bearings without interference. After the pockets were cut
and the holes enlarged, the volute ring was reinstalled.
The bearings have a 0.5" inside diameter, and two 2" long 0.375" US standard
coupling nuts were turned
down to 0.5" over approximately 1.5" of their length to match the
inside diameter of the
bearings. The turned sections of the nuts were then polished with emery paper
and crocus cloth to allow the bearings to slide
smoothly on and off the nuts.
Using the wooden soft
jaws to hold the 0.825"
diameter PVC rod in a vice, the length of 0.375" threaded
rod used for the axle element
of the key-slotted axle assembly was centered through the PVC rod by turning it
with a wrench against double
nuts. The double nuts were removed, and the coupling nuts were screwed onto the
ends of the 0.375" threaded rod, with their turned sections outward, to provide
the bearing surfaces for the
key-slotted axle assembly.
To install the axle, on one
end of the axle rod the coupling nut is
threaded up the shaft until
it is near the 0.825" PVC rod section. This allows that end of the axle shaft to
be passed fully through the
bearing in its support
upright, which, in turn, allows the coupling nut on the opposite end of the axle
to be aligned with and
inserted into the bearing in its support upright. Threading the coupling nut
near the PVC rod back down the axle and into its bearing completes
installation of the axle.
Prior to installing the axle, a 0.5" inside diameter locking
collar is slipped onto the
bearing surface of each coupling nut to
retain the axle between the
To complete the basic
assembly of the Mark-II
turbine, the center
holes in the volute end
plates were cut out, on
center, to a diameter of
2.25". Expanding the openings provided clearance for the ends of the 0.825" PVC
rod and compression nuts on its ends during assembly and spin testing.
The 0.5" inside diameter locking
collars and partially turned
coupling nuts were removed
from the 0.375" threaded rod axle, a 0.875" US standard thread nut was
screwed onto one end
of the 0.825" PVC rod on the axle, and a
regular 0.375" US standard
thread nut screwed onto each end of the axle far enough to allow the coupling
nuts, with their locking collars, to be reinstalled. On the end of the
axle closest to the 0.825" nut on the PVC rod, the regular nut and coupling nut
were run up the axle to near
the PVC rod. One of the volute end plates was
leaned against the volute
side of one of the axle support uprights and the end of the axle with the
coupling nut threaded up near the PVC rod was passed
through the volute ring from
the side opposite the leaning end plate, through the end plate center hole, and
into the center hole of the bearing in the pocket in the axle support upright.
In order, the runner disc
spacers, runner discs, and were slipped over the axle and onto the PVC rod and
the second compression
nut screwed onto its end of the PVC rod locking the runner assembly to the PVC
rod. The second end plate was slipped over and both end plates
mounted with brass washers
and screws. The axle was installed into the support bearings as described in the
previous section. With the coupling nuts in place, the regular 0.375" nuts were
run down the axle shaft to contact the coupling nuts, then the nuts were
double-nut fashion, to fix
the coupling nuts on the axle. Finally, the locking collars are
adjusted to take the play out
of the shaft by sliding them up to the bearing faces and tightening them down.
(c.a., January 2008)
Here I'll be documenting tests of larger runner designs, and such. But, don't
expect anything to show up too soon. There is still a lot of work to do with
dynamometer testing, and flow analysis on the six-inch turbine. Also, work
on the Mark-II turbine to this point has been somewhat just proof-of-concept
regarding construction. There need to be a few changes before real work with the
new turbine can begin. In particular, the turbine, in its current state, has no
inlet nozzle. Also, the threaded rod material used in assembling the key slot
axle is notoriously not straight. So, at very least, before taking the Mark-II
out for a spin, an inlet will need to be constructed, and a new central axle
element machined from genuinely straight rod.
(Clicking reference numbers here takes you to the text location of the
 Heimann, Erich H., 1975. Do it
yourself with plastics. Mills & Boon Limited.
Last updated 03August2008
Alan Swithenbank, email@example.com