At 5.5 knots motor RPM is about 1800. Reduction is 3:1 so prop is at 600.
I designed my system to get the motor into a good efficiency range at my operational speeds based on the motor data from Motenergy. See attached. No mysteries about the ME1616 performance parameters. To be outside that efficiency range means more heat. You can do it but it costs. There's also prop efficiency to consider. I have an 18" prop and wanted it spinning slower than it did with the diesel. I am at 800 max now (was 1200 with diesel). Prop pitch is a bit less precise with slip considerations but I think I have it all dialed in pretty well now. The reduction gear (3:1 belt drive for me) is another tool to fine tune it all. How do you do that with direct drive? Change the motor windings? That's not an option with the ME1616.
I suppose the belt drive adds noise but it's still a lot quieter than the diesel. And if I really enclosed the compartment with sound proofing (none now) it could be close to silent which turns out to be a bit of a problem when your trying to understand what is happening in operation. Even with a little sea noise it can be hard to tell. So be careful what you wish for.
So my setup is designed around a max motor RPM of 2400 at 48V. The reduction gear was chosen to get my prop RPM to max at 800 and prop pitch was set to get me about 7 knots at max. I had expectations of performance based on data I collected from every similar installation I could find and my system has exceeded expectations. I think a lot of that is because my prop diameter and pitch are better matched to the system than average. A lot of folks are just using the prop that they had with the diesel but now have different RPM profiles and things don't match as well. So spend some time on that for best results.
Do you know what the reduction gearing is in your sail drives? Perhaps it's in a range that will get you a proper match with direct connection of the ME1616. But probably not? I don't know the relevant parameters of your boat and sail drives and props. And even if I did I might not be able to make anything of them. Could you drive the hydraulic system with the ME1616? I have no idea if that's even worth considering.
Dan Pfeiffer
On 2024-08-14 12:40 am, Charlie wrote:
Dan do you know what speed your motor is spinning at for the 3kW at 5.5kts?
I saw your gear reduction unit and I am trying to decide if i need to build that as well. To get the rotor rpms up where the motor is happier to run at.
- (Also is that true for this ME1616? are motors happier at higher RPMs? I thought DC motors were happy to put out torque at low rpms?.. but everyting i have read recently says keep the RPMs in an efficient band which is elusive to ascertain.
So i am trying to find out where the motors are running at RPM wise and if I should direct couple or gear down the motor. Then if I gear down (which seems logical now) to which RPM range am I calculating towards?
Thanks guys!
- This boat is a catamaran, has very interesting hydraulic drives at the moment. Has standard saildrives mated to the hydraulic gearmotors like on a piece of farm equip. Very compact and tidy but not very efficient.
