A
look inside the Arneson Surface Drive ASD8
When I describe the ASD8 I'm using in my Turbine Powered Boat
Project, it seems many folks are unfamiliar with Arneson
Surface Drives, so here's a brief
explanation.
Invented in
the early 80's by Howard
Arneson the Arneson
Surface Drive offers a high-performance
alternative to other
marine drive systems. Arneson Surface Drives are also
produced under license by Twin
Disk.
When
it comes to drives for my 1400 HP gas turbine, I can
count the choices on one hand. Very few will stand up
to the torque of a T-58 turbine.
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Simple and reliable, Arneson
Surface Drives are absolutely bulletproof! Featuring
a bronze thrust tube and 2" stainless shaft, this
monster is rated
to handle 1400 HP.
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These
are the 'before' photos my Arneson ASD8. This particular
ASD8 drive unit was manufactured in 2000 by Twin
Disk. This Twin Disk ASD8 surface drive is identical
to the Arneson ASD8 bronze inline surface drive.
Weighing
under a couple hundred pounds fully installed, the Arneson
Drive (ASD8) features a full 40º of steering swing and
allows the operator to power trim up to 15º while making
power and underway.
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Here's
the trim pump, associated lines, and some wiring.
It's
obvious all the components (including these Twin Disk
steering and trim cylinders) are engineered for reliability
in high
performance and extreme applications.
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Here's
the stainless steel hardware, backing plate, and drive-line.
This Arneson ASD8 was the one part of I was very concerned
about being able to locate (within my budget). You just
never see these available used (unless they are incomplete
or garbage).
I
really 'lucked out' and found this entire package for
sale locally. It had only been run for a couple seasons
and was removed because the increased speed caused the
hull to 'porpoise' more than the owner felt comfortable
running with. The seller even included several pieces
of optional equipment; Char-Lynn
helm pump and engine-driven power steering pump.
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The
Char-Lynn power steering system calls for servicing with ATF
Type "A" (which is real hard to find) but through
extensive research,
I discovered that Dexron
III/Mercon ATF is a suitable substitute.
Since
this is a high-performance project, I want to be absolutely
sure all my gear is in top operating condition
My
ASD8 appeared to be in outstanding condition, except for a
small tear in the boot. Since I had no idea how long the tear
had been there, I wanted to inspect inside to ensure there
was no water intrusion and no subsequent interior damage.
These
photos and descriptions are only intended as a general orientation
and introduction to the Arneson Surface Drive model ASD8.
There is no substitute for qualified personnel
following the maintenance procedures as outlined in the maintenance
manual.
Disassembly
was a breeze. I cleaned and inspected (inside and out) and
determined the need to replace the boot and trim cylinder
connecting pin.
Ken at Pacific
Surface Drives was very helpful and provided the parts
(and advise) I needed. After the parts arrived, I prepared
for re-assembly.
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After
I removed the old boot, I performed some minor corrosion
control and sprayed the exterior of the drive housing
with clear lacquer.
Next,
I tapped the threads in the forward end of the housing
to ensure re-assembly goes smoothly.
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I
stopped by the local Marine Store and picked up some
new packing. It was like stepping back in time about
75 years. They've got boat loads of old marine parts
and supplies from yesteryear (both new and used).
Here's my new boot that just came in from Pacific
Surface Drives
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The
new boot gets slipped over the end of the drive tube
(actually I had the wrestle it on there).
Here's
the ASD8 ball. After only a couple seasons of use, it
showed no signs of wear and cleaned up real nice.
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Slip
the ring nut on then the ball gets bolted back onto
the drive tube.
The
notches in the back of the ball line up at the top and
bottom (to allow lubricant to flow through into the
tail housing).
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Be
sure to properly torque the bolts.
The boot is pulled back to allow access
to work the ring nut.
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I
cleaned all traces of the old gear lube out of the socket
and inspected it. The double cardan universal joint
also showed no signs of wear.
These
four nylon rings go between the nut and the ball.
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I
supported the drive tube with my hoist and assembled
it vertically. After inserting a ring of packing and
the O-ring, I carefully lowered the ball into the socket.
Here I'm putting the outer ring of packing in place.
Next the four nylon rings get put in place and the spanner
wrench will be used to tighten the ring nut.
Now
we have a new Surface Drive. After it gets mounted on
the transom, I'll re-torque the ring nut,
plumb the reservoir, and service it with 80-90W gear
lube.
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Here's
my ASD8 steering cylinder after I 'went through it'.
All the corrosion was removed, seals checked, the brass
fittings were replaced with stainless, and the rubber
hydraulic hoses were replaced with stainless steel braided
aircraft lines. Clear lacquer will help keep it looking
good.
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The
last of my stainless fittings finally arrived, so I
was able to get my ASD8 trim cylinder assembled also.
Now
all the rubber hoses have been replaced with high-pressure
stainless steel braided aircraft line to ensure long
life and high reliability.
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My
Arneson Drive came with an Osborne 22 x 28 prop that
had been well taken care of (and cleaned up pretty nice).
This prop is the correct pitch for my boat and is a
little larger diameter than the experts think I'll need.
It's perfect for testing, then I'll have some real data
to work with. I hope to be testing on the water early
next summer.
I'm
told I'll need a Rolla 16 X 28, 5-bladed surface
piercing prop, but I want to gather some 'hard data'
by completing my on the water testing before I invest
the money. Howard Arneson gets 120+ mph out of his T58
powered Skater
32' and I estimate my Cobra will be just about 1,000
lbs. lighter. Based on his results, I believe 125 mph
is within reach (after I get everything dialed in with
the correct prop). Only time will tell.
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I
began the process of 'dry fitting' my Surface drive.
My transom turned out so nice I I really hated
to drill into it.
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Now my Arneson
ASD8 surface drive is mounted.
Next,
I'll set the gas turbine in place and measure the drive
line
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Once
I get hydraulics hooked up, the trim cylinder will hold
the drive up.
After
the drive line is fabricated, I'll locate the engine
and design motor mounts.
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My
turbine
powered boat is now complete.
I
went through every component in my boat the same way.
I take my maintenance very
seriously and high reliability is critical throughout
this project.
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