Bob D. wrote: ↑Tue Jun 07, 2022 10:33 am
I would think a larger hydraulic motor, prop driven, plumbed to a smaller displacement hydraulic motor might do something for you. These motors need alot of volume to operate. Running a big one at slow rpms might give enough output to a smaller one to do the work you need.
Hopefully the flapping wings are counterweighted fairly balanced so your not trying to lift a bunch of weight and also control it crashing down.
That's basically what I'm banking on.
The bird is being built by someone else in another state. I quite literally won't know what I'll be working with until its delivered. They haven't started on it yet and I told the guy who's overseeing this whole project that I need to be in contact with them before they start. There are a lot of details we need to discuss first.
Bill Shields wrote: ↑Tue Jun 07, 2022 10:45 am
I guess that I am stupid and still cannot understand why you cannot do this with a generator/ motor.
Not at all. That was actually my first idea too. Honestly, I'd prefer to do it that way but I still don't believe it's the best method.
If the water flow was relatively constant, that's how I'd do it. However, the flow changes like a sign wave. The wings are supposed to flap faster or slower to go along with the speed of the water. I don't think I could get that to happen with a generator and a motor easily. The high current draw to make the motor start moving may not let the generator spin until a certain threshold is hit. I'm hoping that even if the water is moving to slow for the pump to make the motor at the bird move, it won't stall the prop completely. Basically I'm banking on the bypass leakage inside the hydraulic motor for when speeds are too low. Again, I'm 1000% green to hydraulics so I don't know if it will work that way or not.
Bob D. wrote: ↑Tue Jun 07, 2022 11:22 am
Not sure what the plan is for making the bird switch direction and flap continuously. Maybe a piston to change direction and motor rotation for flapping. There will be a lull in motion during slack tide
I have to have some sort of a rudder in the water to point the bird in the direction of flow. That's one of the requirements, Plus it will mean the prop should always be facing in the proper direction.
The lull in motion is totally fine and expected. The speed of the wings is supposed to be in relation to the speed of the water flow. How anyone not associated with this project is supposed to know that when they see it is beyond me, but that's what they want.
liveaboard wrote: ↑Tue Jun 07, 2022 11:44 am
Solar panels work well these days but this is a sculpture and the artist is clearly quite particular about appearances.
Having said that, there are towed generators for sail boats, or there used to be.
Exactly. A concept artist drew something up for him when they were making the proposal. They were really excited with how it looked. Did anyone think to ask if it was even possible to make this contraption first before taking on the job? Nooooooooo. So now it's up to me to figure it out how to pull it off. Artist in New York, guy making the mechanics in Massachusetts and it gets installed in a river in PA by a rigging crew who's never seen it.............what could possibly go wrong?
Yes, they do still make tow behind generators. Like Bill, my first thought was to go electric. I know nothing about hydro-power generating so I started digging around for small scale, off the shelf options. Those didn't seem like they would pan out but the idea of a prop stuck with me. A few days later a video popped up on rebuilding hydraulic pumps which gave me the idea to try that. It had the most potential and now here we are.
Griz