David,
Our Chief Engineer at Electric Yacht, Scott McMillan, discarded the chain drive option a few years ago because of the noise issue. Cogged belts still give the option of varying a sprocket size to allow for custom gearing for each installation so that in most cases, you can use your old prop and shaft eliminating the need for haul-out.
Addressing the alignment concern, sprockets are both contained within a body that integrates the motor, the gearbox and the controller, so both shafts are permanently aligned perfectly. You can see photos and other info at http://www.electric
Bill Tomlinson, Electric Yacht.
--- In electricboats@
>
> Personally, I would rather go with the gearbox. Keeps the complexity
> down and makes for a beautiful engine room. I mean look at this:
> http://propulsionma
>
> Still, I can see where the belt/pulley setup has its advantages:
> - each component is relatively inexpensive so spares can be kept on board.
> - parts are available everywhere and from many different suppliers.
> - you even have a reasonable chance of finding what you need in a retail
> store that is open on a long weekend.
>
> Mind you, once the drive system is installed and everything is properly
> sized and aligned, the chances of anything failing are pretty small
> whether you go belt/pulley or gearbox...
>
> James:
> How do the gearboxes hold up over time in a salt air environment?
> Any chance of galvanic interaction with other metal bits?
> And what about field servicing?
> Is there anything an owner can do on his/her own in the field if
> something goes wrong with their gearbox?
> What spare parts would you recommend a prudent owner have in their
> on-board inventory?
> Some closeup photos of "at install time" and "after x seasons" would be
> great (actually, that would be great for all of you electric converts to
> do1).
>
> Cheers,
>
> /Jason
>
> James W. Lambden wrote:
> > David,
> >
> > The gearbox solution will deliver more power, more efficiently than any other solution. Helical gears are 97% efficient and seals account for losses of another percent. Gearboxes have an integral thrust bearing. The cast iron of the gearbox acts as a heat sink for the motor so the motor is capable of running longer at higher loads. There is no possibility of catching fingers or clothing like belts or chains can. Gear noise is minimal with slower turning motors and big slow turning propellors. Gearboxes can be mounted to a stainless plate and put back on the original motor mounts for accurate alignment. Split / Flex couplings offer alignment and make it easy to install.
> >
> > The greatest advantage of the industrial gearbox is the many different gear ratios. They are essential to be able to balance the system for optimum efficiency and power.
> >
> > James Lambden
> >
> > www.propulsionmarin
> >
> >
> >
> > ----- Original Message -----
> > From: dennis wolfe
> > To: electricboats@
> > Sent: Wednesday, November 25, 2009 7:06 PM
> > Subject: Re: [Electric Boats] Bearings and power transmission
> >
> >
> >
> >
> > David,
> >
> > The flange mounted ball bearing has plenty of capacity to take the small thrust loads 6hp can generate and it has a spherical OD so will align itself with the prop shaft. The timing belt does not need a tensioner, just mill slots in the plate to slide the motor to create tension in the belt. The belt and pulley solution is lighter, cheaper and quieter than the gear solutions, plus you can change the ratio by substituting a new pulley and belt.
> >
> > You could use your existing gear box from the ICE too, if you can devise a way to couple the motor to its input shaft plus mount the gearbox to the boat. Not so simple.
> >
> > I think the al plate is a better mounting system - it is more rigid than plywood w/fiberglass, easier to make and won't crush under the bolt heads. You can machine 6061 aluminum with wood working tools, even cut it on a table saw with a carbide blade.
> >
> > Denny Wolfe
> > www.wolfEboats.
> >
> >
> > Message -----
> > From: goldsmithfoil
> > To: electricboats@
> > Sent: Wednesday, November 25, 2009 8:54 PM
> > Subject: [Electric Boats] Bearings and power transmission
> >
> >
> >
> > Hello group, I'm putting together an electric system for an Islander 32' using the MARS brushless set-up. I'm puzzling out the power transmission and motor mounts. First question is about the motor mounting. Looks like most people are using 1/2" AL to mount the motor and shaft bearings. Could heavily glassed ply be used in its place or does the AL acting as a heat sink make it a better choice?
> >
> > Second question is about power transmission. Seems there are three choices: use an existing marine transmission, use an industrial gear box, or set up something with belts and pulleys.
> >
> > I have the gear box from the diesel we pulled, I just worry about it being inefficient and not allowing the prop to spin the motor for regen. Anyone know how efficient small marine transmissions are whether it would be a good way to go? It would certainly be the easiest solution and the MARS motor runs at about the same RPM as the Yanmar did so the ratios should match up well.
> >
> > Second option is an industrial gear box like Propulsion Marine offers, this also looks like a good solution with a minimum of engineering involved.
> >
> > Third option, which I'm leaning toward is setting up a board with the motor and some pulleys to bring the speed down for the shaft. V-belt, chain, or timing belt? One thing I haven't seen anyone address is idlers or tensioners on the belts, there has to be some method of tensioning the belts. Are people just using a slot and leverage before bolting down like an alternator? I've seen spring loaded tensioners for timing belts that looked like a good solution.
> >
> > The other question I have is about thrust, a pulley and belt set up needs some sort of thrust bearing, do the flange bearings I see being used provide that function or is an additional bearing needed in the system? I'm new to the mechanics of power transmission, so I've got these questions.
> >
> > Thanks, I'm looking forward to some discussion on the mechanics of setting up such a system. I've got a good grasp on the electrics, charging, and battery systems, its just the mechanical part I still need some help with.
> >
> > Thanks,
> > David
> >
> >
> >
> >
> >
> >
>
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