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Smart Drive Oil Barrel Undershot Waterwheel
bmannz:
I now have a months RPM data and the average is 5 rpm in the rainy season, I have seen up to 12 rpm, oddly the higher the flow the lower the speed as the buckets get stuck underwater in this run of river design. I could reduce the amount of bucket, so really just have the leading edge (more like a banki / cross flow) and increase the bucket count, and / or shift the wheel to a place with fall to fix this.
Sorry about the terrible pic, red is rainfall in mm, blue is wheel rpm
Anyway back to the gearing issue, I went to the laser cut man yesterday and asked how much for a 1500 tooth sprocket so I can direct drive my 9 tooth and achieve 166x ratio on my estimated low flow average of 3 rpm to get 500 rpm on the smart drive, no problems he said, that sprocket will be 4 metres across!!
Ok I say, let's assume I want a 1 meter diameter sprocket, how many teeth and how much is that? The rough price estimate was $250 which I thought was pretty good, however the tooth count was down around 450 which is a 50x ratio, less that the 100x a lay shaft will give me so it's back to Randall at Edgell automotive for some more go-kart parts.
I collected some 25mm pillow block bearings, and a length of 25mm mild steel shaft and dropped them into the workshop in amongst some racing cars in pieces having their engines rebuilt, randalls going to turn the shaft on his lathe to fit the small bearing and all going well I'll be installing this weekend...
MattM:
You would need a planetary gear system to keep the gears small. Is that what the lay shaft is, a planetary gear?
bmannz:
Hi Matt, it's an intermediate shaft placed between the waterwheel axle shaft and the Fisher and Paykel generator shaft with a big and small sprocket on it.
At the moment I have a big tooth count on the waterwheel shaft and a small tooth count on the generator, 89:9 (10x speed increase) I'm going to add another shaft in between the two so the 89 teeth on the wheel will drive the 9 teeth on the intermediate shaft which is also turning another 89 tooth sprocket which drives the 9 tooth on the generator
So 5rpm in the creek will give me 50 rpm on the intermediate shaft which will produce 500 rpm on the generator (or so the theory goes)
Will be chucking it on today so will post a pic when it's done
george65:
--- Quote from: bmannz on September 08, 2017, 03:15:11 PM ---So 5rpm in the creek will give me 50 rpm on the intermediate shaft which will produce 500 rpm on the generator (or so the theory goes)
--- End quote ---
This would be 100:1 speed increase. Sounds like it is going to need a LOT of Torque to just to overcome the gearing drag let alone power anything on the final output.
I was putting together a Post hole Differ this afternoon that has a 40:1 Reduction gearbox on it. Just twisting the output shaft to make the input side spin up, Even with a Screwdriver as a lever took a lot of effort. I think for 100:1 gear up, you'd want to be using serious shafts and gears because even if you do have the torque, once a resistance is applied at the other end, the forces on the Primary drive components are going to be Huge.
Going to be 100X speed magnification and even more Torque multiplication.
It would seem to me that there is only so much driving power anyway and the the least path of resistance will simply be around the waterwheel rather than through it.
I played around with F&P motors a while back and I would say they are a pretty " savage" sort of a generator. They don't need much speed as they come out of a washer to generate high voltage (gave a few friends some good belts after I did it to myself and realised how ppowerful they were) but the torque is going to be reasonable to get any power out of them. Even spinning them with no load creates some reasonable drag, maybe just from the fields energizing.
I have nothing but mucking around and gut feeling to go on but I would think that given the power I imagne you have from the stream, you would probably be OK at 100 RPM on one of those motors to make power which would be at least a couple of hundred volts and then pull it down to what you want ( if it's for battery charging ) from there. If you want AC, My gut feeling is you are not going to get much more than to light up an LED globe, If that.
Not trying to put you off, more like noting my predictions to see how far wrong I am when you get the thing working. :0)
That said, 100:1 gear up still sounds like a lot of parasitic drag to me.
MattM:
Just a rough guess, but he will probably pull a steady 300-350rpm. He can hand start it, because once it starts spinning - the water isn't sporadic like wind - it will sustain.
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