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Turbine Powered Boat

A look inside the Arneson Surface Drive ASD8

Jet Boat

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.

Arneson ASD8 Diagram

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.

Arneson ASD-8 side view

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 40 of steering swing and allows the operator to power trim up to 15 while making power and underway.

Twin Disk ASD8 Drive
Twin Disk Surface Drive

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.

Twin Disk ASD8 Drive
Twin Disk Surface Drive

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.

Arneson Surface Drive

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.

We have T-58 & Rolls Royce Gnome gas turbines available to power your project.
We also have starters, manuals, instruments, and gearboxes for T-58 and Gnome gas turbine engines.

T58 Turbine Powered Boat

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.

Twin Disk Surface Drive

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.

Arneson Surface Drive
Arneson ASD-8

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

Arneson Drive
surface piercing drive

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.

Arneson asd8
Maintaining the Twin Disk surface drive

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).

ASD-8 surface drive
Arneson sold to Twin Disk

Be sure to properly torque the bolts.

The boot is pulled back to allow access to work the ring nut.

Howard Arneson surface drive
ASD-8 stainless steel drive shaft

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.

Arneson surface drive tools
ASD8 Drive Repair

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.

Surface drive boot

General Electric T58 Turbine

ASD8 steering cylinder

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.

T58 turbine engine testing area
Twin Disk ASD8 trim cylinder

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.

Arneson ASD8 trim cylinder
Surface Drive Prop

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.

Surface Piercing Prop
Composite Arneson surface drive adapter

I began the process of 'dry fitting' my Surface drive.

My transom turned out so nice I I really hated to drill into it.

Composite Arneson surface drive adapter
Composite Arneson surface drive adapter

Now my Arneson ASD8 surface drive is mounted.

Next, I'll set the gas turbine in place and measure the drive line

Composite Arneson surface drive adapter
ASD-8 Arneson surface drive

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.

Arneson surface drive ASD8

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.

Turbine Powered surface drive

Please take a look at my "items wanted" list.

My Dream   T58-GE-3   4 Sale   T58-GE-8F   Projects   Gathering   Composite   SDG   Boathouse   History   Gnome   Cobra 30   ASD8   Wanted   Trailer

Twin Disk ASD-8 drive

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