Building a new boat {OK dreaming about it!!]

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fredrosse
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Re: Building a new boat {OK dreaming about it!!]

Post by fredrosse » Wed Apr 07, 2010 1:11 pm

A toothed timing belt is the way to go for an efficient, silent, and low maintenance drive system between the engine and drive shaft.

My electric boat uses a 1 inch wide timing belt, driving 4:1 to the prop (1700 rpm motor, 425 rpm prop). My steam scanoe also used a toothed timing belt drive, much smaller yet, at 2:1 ratio (600 rpm engine, 1200 rpm drive to the I/O unit). The belts I use are much smaller than the ones found on typical automotive four cylinder engines, yet entirely robust enough to allow grounding the propeller against a rock while traveling at full speed. Sorry to say, I did this once with 4 adults in the electric boat, but because of the relatively low power of the boat, and low inertia of the rotating components, no harm was done.

With moderate belt tension (or an idle pulley as found in typical automotive practice) belt slap will not be a problem.

Keep the engine and propeller shafts parallel, and no type of flexible shaft connection will be required.

The timing belt drive for typical four cylinder auto engines would be sufficient for steam engines as typically found in small launches. The biggest expense here is the cost of the timing belt sprockets, not the belt. Automotive belt sprockets are 2:1, which just might prove about right for your launch setup, the prop shaft turning double the engine speed, so you can use the much more plentiful propellers for gasoline/diesel engines, typically having pitch somewhat less than diameter. Using at automotive sprockets would save considerable costs if you have access to a junkyard, and can fit the automotive sprockets to your shafts. You can purchase belts which fit your sprocket distance requirements at moderate cost. I troll the e-bay website for bronze propellers, and typically buy 14 to 18 inch propellers, in excellent condition, for about $20-$30 US.
steamboatjack
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Re: Building a new boat {OK dreaming about it!!]

Post by steamboatjack » Tue Apr 13, 2010 12:15 pm

I don't think using old automotive parts is the way to go with toothed belts.
Industrial tooth belts components are not that expensive in UK they can be obtained from Fenner I dare say there is a similar outfit in the US, maybe Graingers or similar. Go for the High Torque drive type with rounded teeth and pulleys fitted with taper lock bushes, could not be easier.
Use as bigger diameter as you can fit in but if its outside the power/torque range use a wider belt.
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Jack
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DetroiTug
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Re: Building a new boat {OK dreaming about it!!]

Post by DetroiTug » Tue Apr 13, 2010 2:04 pm

A source for timing belts and timing pulleys here in the US is Stock Drive products/Sterling instrument:

https://sdp-si.com/eStore/

I'd be a little concerned about using these in areas of high temperature.

As Steamboatjack says, the HTD series is best for higher torque loading.

-Ron
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