Belt Drive

brian eiland · Dec 25, 2016

DVD of Build Process & Drive System

Barry said: ↑

Abel Tasman Sea Shuttle working in the Abel Tasman National Park uses belt drives on some of their larger aluminum catamaran passenger ferries.
Basically they take passengers around the coastline of the park and drop them off on SHALLOW sandy beaches by beaching the boat.

Their problem was to be able to get their ferries close enough to shore to allow the passenger to disembark but not have the propellers digging up the sand.

They designed a belt drive system to be able to lift the props partially out of the water for shallow water operation.

Actually they designed and built two different types of drives, As this was several years ago there is a chance that some of what I put into this comment might pertain to one or the other type of drive as to length of boat etc but will get this information into the thread as to the viability of a belt drive system.

I rode on both of these taxis, one out and one back several years ago

Belt drive
25 meter aluminum catamaran, 150 passenger, twin Scania 485kw/600 hp diesels
The motors were above the prop shafts in an engine compartment that hinges just ahead of the front of the engines. When coming to shore the engine compartments were pivoted UP by hydraulic rams lifting the props partially out of the water.Ie the motor and props lifted up

I spoke to the captain about this unique drive and he put in a dvd on the in cabin screen that showed the entire build process of the boat and drive system.

Again from memory, I would expect that the ferry cruised at maybe 20 knots and the captain said that they had several thousands of hours on a set of Kevlar belts

Side pivot taxi
Not sure on the size of this boat ( maybe 15 meters) the engines were fixed but their outdrives which were designed by the owners, actually rotated outward on the axis of the input shaft to lift the props partially clear of the water

Two rather unique drives
Click to expand...

We never did get a copy of this DVD ??

Barry · Dec 25, 2016

Hi Brian
I believe that you had sent them a request for a copy. I had not made contact with them about the DVD

brian eiland · Dec 25, 2016

I did make a request, but never got anything in return,...not even a note?

brian eiland · Feb 22, 2017

Barry said: ↑

Hi Brian
I believe that you had sent them a request for a copy. I had not made contact with them about the DVD
Click to expand...

They finally answered with an email, but then never carried forward with my request for more info????

brian eiland · Feb 22, 2017

uniform elongation of Silent Chain

Meantime I was doing a little house cleaning on one of my storage disc and ran across this little diagram that had existed in a PDF form, but I managed to convert to a jpg image.

brian eiland · Apr 23, 2017

Been looking back at this duo-prop, chain drive leg arrangement I had suggested for one of my larger catamaran designs....

....and figured I might make reference to this very interesting video presentation...
DUEL: Duoprop vs Singleprop
https://www.youtube.com/watch?v=TdcWQpN8hl4&t=637s

brian eiland · Jan 9, 2024

brian eiland said: ↑

Been looking back at this duo-prop, chain drive leg arrangement I had suggested for one of my larger catamaran designs....

....and figured I might make reference to this very interesting video presentation...
DUEL: Duoprop vs Singleprop

Click to expand...

I had a fellow inquire just recently about some prop drive systems i had suggested in the past. I was looking thru some of my postings, and this one that ended this series of discussions came up.

I thought it might deserve re-posting.

brian eiland · Dec 4, 2025

I've become re-interested in this 'silent chain drive' subject again. I was having some problems finding all of the images (not that many) of the PYI units,..AND surprisingly I could NOT find any such outdrive unit in their inventory?? ...so apparently they just dropped the idea??

I still think it is very viable, and may make an attempt to find someone interested in pursuing such a product. There are a LOT of catamarans out there now as compared to when i left the business.
I'll just repeat this quote I made long ago,...

Big Torque over 90 Degree Gears?, perhaps 'Belt drive'
Click to expand...

On this other subject thread I had advanced the idea of belt or chain drive arrangements:
http://www.yachtforums.com/forums/technical-discussion/2232-new-drive-system-volvo-penta.html

"Other than direct straight-shaft drive of propellers, most marine drives today involve some sort of 90 degree arrangement, ie.sail drives, stern outdrives, outboards, etc. The 90 degree gear set (and there are usually two sets) is the potential weak link in the system. All the power is being transferred over a very physical small contact area between two bevel gears. This contact patch can be nothing more than a thin line on the opposing two teeth! Special hardened gears and maintaining close-fit tolerances permit the horsepowers of today. But when it comes to diesel engines, the situation gets worst. The diesel is by its nature a much more torque'y beast. Gears to handle an even modest horsepower diesel are extra hard pressed. Teeth can break or get worn so quickly as to loose all tolerance."

Click to expand...

brian eiland · Dec 7, 2025

brian eiland said: ↑

I wasn't speaking of an 'open' chain drive but rather a contained one that maintains the perfect parallel shaft arrangement that is required for long term application. These 'silent chains' have been Incorporated in many industrial drive applications.

An older Oldsmobile vehicle application to connect the transverse motor and transmission arrangement proved highly durable for over 100K miles with just ordinary transmission fluid lubrication.

There are also a number of subtle differences in the chain to drive gear details in these 'silent chains'

There are a few other links over on this other posting:
Prop Shaft Systems. http://www.boatdesign.net/forums/inboards/prop-shaft-systems-24636-4.html#post286085
Click to expand...

If there are still any of these folks interested in the subject, could someone answer why i can no longer find ANY images of those PYI silent chain drives on the internet (other than 2 of mine that don't even show up with an image search??

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Belt Drive

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