Out of interest, what is the power level for that 97% efficiency? My experience of measuring power losses in smaller gearboxes (specifically the Mitrpak range of right angle drives) tended to show that the losses were fairly fixed in terms of power, so the efficiency ranged from around 1% at very low power levels to around 98% at the maximum rpm and torque that the gearbox would accept.
The specific gearbox I was looking at would handle around 300 watts maximum at the relatively low rpm I was working at (so lower than its absolute maximum power capability by a fair margin), but had a fixed power loss of around 20W when cold, dropping to around 14W when warm. At normal operating power of around 100W the efficiency was between 80 and 86%, whereas at the maximum power I was using of around 300W the efficiency could be as high as 95%.
I switched to a belt drive in order to reduce the high fixed losses associated with a gearbox (most of the losses seem to come from friction in the bearings and seals at low torque levels). I'd be interested to see an efficiency vs rpm and efficiency vs torque plot for these gearboxes, as I suspect that they may well be way poorer than 97% efficient over a significant part of their acceptable operating region.
Jeremy
--- In electricboats@yahoogroups.com, "Eric" <ewdysar@...> wrote:
>
> Another option is a Browning 3201 gearbox. The ME0907 should bolt directly to it. They have a built in thrust bearing, 97% overall efficiency including bearings and seals, 10,000 hours MTBF and come in 10 different gear ratios. To me, a single component that handles everything (reduction, thrust, motor mount, etc.) helps keep it simple.
>
> Fair winds,
> Eric
> Marina del Rey, CA
>
> --- In electricboats@yahoogroups.com, danbollinger <no_reply@> wrote:
> >
> > Take a look at Goodyear Eagle NRG herringbone belts and matching pulleys. http://www.goodyearep.com/ProductsDetail.aspx?id=3400
> >
> > Most radial bearings will accept a certain thrust, moreso if they are angular contact type, so you might not need a thrust bearing in your drive system.
> >
> > For simplicity, look at flange and pillow block mounted bearings.
> >
> > --- In electricboats@yahoogroups.com, "svcabernet" <bsmisner@> wrote:
> > >
> > > Hello all,
> > >
> > > I've been lurking here for a while, which has paid great benefits as I've been putting together a parts list for an electric drive for my Cascade 29.
> > >
> > > Given the limited budget I've decided to "build" the system myself rather than go with one of the tried and true manufacturer's assemblies.
> > >
> > > The one component(s) I've been having trouble with is the reduction drive. I've decided to use timing pulley's/belts or sprockets and chain along with captured roller/thrust bearings but am having a tough time sourcing them. I wouldn't be opposed to a gear reduction either provided a "bullet proof" reputation. The motor of choice is the ME0907 for it's lack of brushes, performance, and affordability. By my calc's a 2:1 to 2.5:1 reduction will be needed to maximize performance. Any ideas would be appreciated.
> > >
> > > Thanks,
> > >
> >
>
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