Post by Deleted on Dec 20, 2016 19:59:10 GMT
Propellors have always bothered me, everyone uses them, but few people realise the downsides to them. But when i looked at paddlewheels, they look the same now as they did 200 years ago, there's been no engineering work done on them, but a great deal has been done on the propellor.
There's some obvious issues with the paddlewheel itself, from an efficency point of view. There's interaction with the engine issues. And there's issues with the way the typical boat moves in the water that can make a paddlewheel positively useless. But there's issues with the propellor too, like wrapping up fishing nets. Like grounding, like being unbalanced at high rpm, and (with outboards) getting supposedly large engine hp thru tortuous convoluted (using tiny gearsets) down to the propellor. The propellor is pretty task-specific: large diameter of one blade twist for bollard pull, and small diameter and another blade twist for high speed lightweight travel. If you hit a rock, pipe, or boatramp, break a blade, you are spending a few $hundred to $thousands for a new prop.
The reason we have propellors as the default interaction with the water isn't because they are better in all cases. It's because way back when, to get more hp from lighter engines, engines which no longer burned coal, engine makers increased the engine rpm. This meant to turn the ole paddlewheel, big heavy gearboxes were needed, negating the weight, cost, and space savings of the new lighter engines. But the engines coupled nicely to propellors. Even continuing to burn coal, the steam turbine offered the same high rpm advantages, to such a degree that power plants and nuclear submarines use them still.
But the propellors are pricey, and difficult to make properly in your backyard.
So, hoping that more was available online as OCR and scanners have been widely available, i went searching again.
I found a pdf about paddlewheels written in 2011, of a well known company down under, who spent some time, outfitted boats with instrumentation, and threw common sense and computers at the problem of bringing paddlewheels into this century. They used a commonly available engine, they made different paddlewheels, they mounted them in the boat in various ways, they measured and computed numbers all over the place. It would have been embarrassing if done in the usa. They plotted peak efficencies at 45 and 50 knots.
One thing they did that i don't really approve up: their final publish paddle design was totally optomised for forwards travel, and would simply not work in reverse. Their absolute last paddle design isn't published. Since it isn't published, i have no idea what they did, and so i have already worked out an improvement. But then, i have been thinking of paddlewheels for decades.
They used the stock car transmission with the car engine, makes sense, this was a prototyping situation, so you use what's in the parts box if you can. But larger gears would last longer, and an innovative design approach might make the gearbox lighter than the car transmission, which is made the way it is for certain automobile reasons.
The result: A method of moving a fishing boat at 35knots using a dead simple paddlewheel that any metalworker can make with simple tools.
The gotcha: Not really, but the paddlewheel drive gives you options not available with a fixed screw-twist propellor, and it's easier to simply steer the boat if a small $25 computer managed the various settings for your preferences. The paddlewheel will be heavier than the propellor.
There's some obvious issues with the paddlewheel itself, from an efficency point of view. There's interaction with the engine issues. And there's issues with the way the typical boat moves in the water that can make a paddlewheel positively useless. But there's issues with the propellor too, like wrapping up fishing nets. Like grounding, like being unbalanced at high rpm, and (with outboards) getting supposedly large engine hp thru tortuous convoluted (using tiny gearsets) down to the propellor. The propellor is pretty task-specific: large diameter of one blade twist for bollard pull, and small diameter and another blade twist for high speed lightweight travel. If you hit a rock, pipe, or boatramp, break a blade, you are spending a few $hundred to $thousands for a new prop.
The reason we have propellors as the default interaction with the water isn't because they are better in all cases. It's because way back when, to get more hp from lighter engines, engines which no longer burned coal, engine makers increased the engine rpm. This meant to turn the ole paddlewheel, big heavy gearboxes were needed, negating the weight, cost, and space savings of the new lighter engines. But the engines coupled nicely to propellors. Even continuing to burn coal, the steam turbine offered the same high rpm advantages, to such a degree that power plants and nuclear submarines use them still.
But the propellors are pricey, and difficult to make properly in your backyard.
So, hoping that more was available online as OCR and scanners have been widely available, i went searching again.
I found a pdf about paddlewheels written in 2011, of a well known company down under, who spent some time, outfitted boats with instrumentation, and threw common sense and computers at the problem of bringing paddlewheels into this century. They used a commonly available engine, they made different paddlewheels, they mounted them in the boat in various ways, they measured and computed numbers all over the place. It would have been embarrassing if done in the usa. They plotted peak efficencies at 45 and 50 knots.
One thing they did that i don't really approve up: their final publish paddle design was totally optomised for forwards travel, and would simply not work in reverse. Their absolute last paddle design isn't published. Since it isn't published, i have no idea what they did, and so i have already worked out an improvement. But then, i have been thinking of paddlewheels for decades.
They used the stock car transmission with the car engine, makes sense, this was a prototyping situation, so you use what's in the parts box if you can. But larger gears would last longer, and an innovative design approach might make the gearbox lighter than the car transmission, which is made the way it is for certain automobile reasons.
The result: A method of moving a fishing boat at 35knots using a dead simple paddlewheel that any metalworker can make with simple tools.
The gotcha: Not really, but the paddlewheel drive gives you options not available with a fixed screw-twist propellor, and it's easier to simply steer the boat if a small $25 computer managed the various settings for your preferences. The paddlewheel will be heavier than the propellor.