Energy recovery from freewheeling prop

[markxengineerin]

Yes. But clutches are complicated and involve a lot of parts, so I'm hoping for something simpler.

[derfy]

Originally Posted by markxengineerin

Yes. But clutches are complicated and involve a lot of parts, so I'm hoping for something simpler.

I was thinking a small clutch made for a tractor or piece of farm equipment. When I google "Prop Shaft Clutch" I get lots of hits.

[abroadreachtrvl]

They make driveshaft disconnects to enable vehicles to be towed behind RVs and such.

https://www.drivetrain.com/parts-cat...ducts-by-remco

https://trailtough.com/product/rear-...t-for-toyotas/

https://remcodsc.com/coupling/

A few ideas...keep in mind none of these are designed to handle the thrust loads from a propeller.

[GrowleyMonster]

Originally Posted by markxengineerin

Soliciting ideas for shaft de-coupling, or any data on regeneration power with/without a decoupling feature... Anyone?

Here is a simple version for brainstorming, where the shaft coupling has to be unbolted from the transmission manually. Shaft gets slide back 1/2" (pick a number) which engages the supplemental shaft support bearing. The manual process isn't ideal, but would keep things simple.

I think the toughest part about this would be figuring out how to mount the blue support structure labelled "hull" to the hull. I imagine it being made of G10 and just heavily glassed in, in a way that would not be very beautiful. But with every hull being different, I don't have a better idea.

If decoupling the transmission turns out to be unnecessary, and if the transmission output bearing can support a small radial load (I haven't looked at it, but it probably can) that makes the design much simpler.

(base sketch borrowed from the SigmaDrive brochure)

"Alternator" would be something like this:
https://www.amazon.com/gp/product/B0...e?ie=UTF8&th=1

Lower KV value would be best, anyone know of any good "motor" sources?

Chains are fine at low speeds. Not always so nice at high speeds. They sling oil. You will want a big wide belt or maybe three ordinary alternator / waterpump type vee belts.

For a motor/alternator I suggest a 5kw class Motenergy motor. Most that size run nicely at 48v with th proper cotroller, and I suggest a Kelly 300 amp 72 volt controller. That is peak current, not sustained, rating, and you want some headroom on the current and heat dissapation, which you get for just a couple hundred dollars extra. You want your controller and motor to just be loafing along because there is no efficiency hit for having them too big, like with a diesel. There is no minimum idle speed and there is no compression to overcome, just a rotor spinning in its bearings, and the electrical load, which you control. In regen mode, where it will mostly be for you, it is generating power and you set the amount. Think of it as electronic braking. That puts the desired amount of juice into your 48 volt bank. Since you won't be using it much for propulsion, a fairly small bank will do, just enough for house loads. Because the bank will not be huge, you may as well go with LiFePO4 batts. That way when you need the electric drive, you can pull current from the bank limited only by the motor and controller. The 5kw motor is rated differently and it is sustained current, 90 or 100 amps by the nameplate. For 60 seconds you can typically triple it. 300a peak for 60 seconds with the controller. You have crazy torque available for a short burst, like for avoiding a floating container or something, or passing under a bridge and your diesel just coughed its last or your fuel filters decided they are just not gonna pass any more fuel along until you change them. You would then be relying on your belts, so yeah actually maybe four vee belts. It is still cheaper than a big herringbone job. I have never used belt drive and someone else might chime in with actual experience, my eboat I set up with a reduction gear instead of belts. Not an option for what you want to do.

You probably already know that watts is basically volts times amps. But another factoid that might interest you is one horsepower is nominally equal to 746 watts. So 5kw is roughly 7 horsepower, and the power band is much wider for EP than diesel or gasoline ICE. More torque above and below, especially below, optimum rotational speed compared to an ICE. Instant on, no warmup, no checking the seacock or oil or hoping the darn thing starts. It's like carrying a gun. You will probably actually never really need it, but you will have it if you do.

You could go with a bigger motor, say 10kw or 12kw but meh. 5kw will do what you need it for. Since it will be spinning the boat prop, it will be equivalent roughly to a 10 or 12hp outboard for a quick push ahead. If you ever use reverse thrust you will need a double acting thrust bearing or two of them. Or for docking with electric, recouple to the diesel with trans in neutral. Docking with EP is waaaaaay cool, even if you are doing it because your ICE isn't cooperating.

However you intend to make and break the connection between shaft and transmission, make sure you don't knock it out of alignment or you will be fiddling with feeler gauges and shims and wrenches and hammers and prybars all day long. Perfect alignment is something to be treasured and not wasted wantonly.




You could also forget about the BLDC motor and 48v bank, and just use a 200A truck or bus alternator charging at 14v or whatevah. You will want multiple pulleys so you can fiddle with the ratio. You will probably not be able to pull the whole 200a out of the alternator but again, bigger is better, with electrical stuff, for heat disappation. Then again, a spare alternator for your diesel could do the job, and give you another reason to keep that spare! Be sure that the pulleys are right next to a pillow bearing or your thrust bearing.