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Author Topic: Performance Impeller  (Read 19242 times)

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Offline Heavynets

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Re: Performance Impeller
« Reply #75 on: November 08, 2017, 03:15:41 PM »
The pitch of the stock impeller varies with its distance from the hub.  Using the actual dimensions at the tip of the blades, the pitch is about 5.816" per revolution.  Using bizler's number, 4.488 (based on actual speed at max rpm) and my number, 5.826 (based on the theoretical pitch), the impeller's efficiency is about <77% (4.488 / 5.826).  The actual efficiency will be less than 77% because I used the blade's tip dimensions and not the average blade dimensions.  This and a dollar will get you a senior coffee at McDonalds.

Offline Painlesstom

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Re: Performance Impeller
« Reply #76 on: November 08, 2017, 04:04:44 PM »
I'm guessing that it's unlikely the 40% infill.  More likely it's the designed wall (shell) thickness, designed blade thickness, absence of a radius where the blades meet the hub or the threads stripped.

Every impeller I've printed has had the same shell and blade thickness, fillet on each side, and the threads did not strip. The first failure I've had with PLA was this one, which I intentionally printed at 40% infill as an experiment. Tested two more impellers since then, at 70%, and no problem.  \./8
Tom

  >:D    

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Offline Heavynets

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Re: Performance Impeller
« Reply #77 on: November 08, 2017, 04:33:20 PM »
They may not have had the same load on them as this one.  Where did this one fail?

Offline Painlesstom

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Re: Performance Impeller
« Reply #78 on: November 08, 2017, 05:45:01 PM »
I was at 3980 rpm, full throttle, for less than one minute when it failed. Hard to say exactly where the failure took place since there was a domino effect once the first blade took a vacation. I have run every other impeller at full throttle as well, up to 5100 rpm, for as long as 5 minutes sustained.  Not worried about it, it was a test and I learned something from it. If there's more to it that infill, I'll never know, testing is telling me that's what it was so I'm happy to stick with 70%. Still could have been a stick that got sucked up, but again I'll never know. lol
Tom

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Offline Heavynets

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Re: Performance Impeller
« Reply #79 on: November 09, 2017, 10:03:48 AM »
When I made my guesses as to the cause and asked "Where did it fail?", I had not seen the picture, only the video.  The picture doesn't show unless I login. 

Is that infill that I see inside the blades near their base?

Was the only variable in this test the change in infill percentage, other than that, it was identical to a previous test?

Offline Painlesstom

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Re: Performance Impeller
« Reply #80 on: November 09, 2017, 11:16:24 AM »
Ok, that makes sense now. Yes, the base of the broken blade shows the infill. Infill and blade count were the only variables to the previous test, nothing else changed.
Tom

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Offline Painlesstom

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Re: Performance Impeller
« Reply #81 on: December 05, 2017, 02:13:16 PM »
Made it out for a quick test of an 8 blade variation today. Water is lower than previous conditions so taking that into account I still saw stock numbers. 4100 rpm @ 15 mph. Still several ideas to test yet, but starting to see a pattern. Any gains are going to be very elusive, good practice with Fusion 360 though.  \./8
Tom

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Offline Maritimer

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Re: Performance Impeller
« Reply #82 on: December 05, 2017, 02:39:46 PM »
Any thoughts on whether more blades would make the impeller more susceptible to ingesting debris? I'm thinking that the wider spacing with fewer blades would allow larger particles to pass through without harm. Perhaps there's a relationship between the spacing of the impeller blades and the spacing of the bars on the intake grate?

== Steve ==

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Re: Performance Impeller
« Reply #83 on: December 05, 2017, 02:48:42 PM »
1 Cool 😎 Point for your efforts.
I'm not an engineer or claim to be one. If you could 3-D print a new pump that takes in more or less water, would that affect the performance?
My hope is that one day you will achieve this as your best modification and we can say bye to Mokai.  :o
🤦🏼‍♂️ Chuck 🤷🏻‍♂️

Offline Painlesstom

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Re: Performance Impeller
« Reply #84 on: December 05, 2017, 03:54:18 PM »
Any thoughts on whether more blades would make the impeller more susceptible to ingesting debris? I'm thinking that the wider spacing with fewer blades would allow larger particles to pass through without harm. Perhaps there's a relationship between the spacing of the impeller blades and the spacing of the bars on the intake grate?

== Steve ==

Sure, but less blades don't provide the volume of water needed to generate the thrust desired, or sufficient load on the engine to keep the RPM down in the power band. To get under 4400 rpm there needs to be a minimum of 6 blades, anything less and you're just making alot of noise while only going the same speed as stock, or slower. I thought 4 blades would be a win too, but even taking up the entire depth of the wear ring the rpm was just too high to be sustainable in the maintenance dept. The idea is to go as fast as possible with the least amount of rpm, I'm trying to not spin the engine any faster than what I'm currently used to. Hoping I can use some of that extra rpm by loading it up just a little more, bring my typical 4400 rpm down to 4100 while gaining something in speed. Would be nice if I had an area close that I could test where conditions were always the same. Running up and down river during different stages makes results fluctuate already, makes it even harder to determine results from testing done weeks apart. lol I'll have to do some more testing with my stock impeller again to get another baseline now that the water is lower for the season.
Tom

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Offline Painlesstom

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Re: Performance Impeller
« Reply #85 on: December 05, 2017, 04:05:45 PM »
1 Cool 😎 Point for your efforts.
I'm not an engineer or claim to be one. If you could 3-D print a new pump that takes in more or less water, would that affect the performance?
My hope is that one day you will achieve this as your best modification and we can say bye to Mokai.  :o

LOL Thanks.  :D 

There is so much science involved with the efficiency and design of a jet pump, I wouldn't even want to think about trying to get into that. Changing anything in the design will affect performance, but I haven't personally felt the pump housing should be changed; although I have been curious what half as many stator veins would do to performance, that seems to be a bottleneck area for debris clogging up too.
Tom

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Offline pirata.sur

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Re: Performance Impeller
« Reply #86 on: December 12, 2017, 07:49:15 AM »
Hola Tom, he estado siguiendo atentamente todo el hilo y los felicito por el desarrollo de estos nuevos impulsores, podrías utilizar el modelo 3D y realizar un molde de arena para fundir una turbina de aluminio...!!
Creo el cuello de botella esta dado por el diámetro del conjunto, sumado a las limitaciones que impone el anillo de desgaste, para aumentar el volumen de agua desplazado tendrás que elevar el numero de RPM ya que con la variable de la cantidad o angulo de las palas la mejora sera de muy poco porcentaje.
Como muy bien han sugerido, Yamaha, Bombardier, etc. utilizan turbinas de 3 palas con mas superposición pero sus RPM están en otros rangos...!!!
Creo que con los impulsores que utilizan, (motores estacionarios 200 c.c. 4T, 6,5/7 HP) es aceptable la performance lograda.
No tienes la posibilidad de instalar un impulsor de 2T y 6000/6500 RPM con el conjunto original...?

Espero nuevos avances, confío en que lograras sacarle alguna Mph mas a tu Mokai, gracias por compartir tu experiencia, saludos desde la Patagonia Argentina, Nilton Farias.

 

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Re: Performance Impeller
« Reply #87 on: December 12, 2017, 08:15:54 AM »
Hola Tom, he estado siguiendo atentamente todo el hilo y los felicito por el desarrollo de estos nuevos impulsores, podrías utilizar el modelo 3D y realizar un molde de arena para fundir una turbina de aluminio...!!
Creo el cuello de botella esta dado por el diámetro del conjunto, sumado a las limitaciones que impone el anillo de desgaste, para aumentar el volumen de agua desplazado tendrás que elevar el numero de RPM ya que con la variable de la cantidad o angulo de las palas la mejora sera de muy poco porcentaje.
Como muy bien han sugerido, Yamaha, Bombardier, etc. utilizan turbinas de 3 palas con mas superposición pero sus RPM están en otros rangos...!!!
Creo que con los impulsores que utilizan, (motores estacionarios 200 c.c. 4T, 6,5/7 HP) es aceptable la performance lograda.
No tienes la posibilidad de instalar un impulsor de 2T y 6000/6500 RPM con el conjunto original...?

Espero nuevos avances, confío en que lograras sacarle alguna Mph mas a tu Mokai, gracias por compartir tu experiencia, saludos desde la Patagonia Argentina, Nilton Farias.

Translation:

Hello Tom, I have been following all the thread carefully and I congratulate you for the development of these new impellers, you could use the 3D model and make a sand mold to melt an aluminum turbine ... !!
I think the bottleneck is given by the diameter of the assembly, added to the limitations imposed by the wear ring, to increase the volume of water displaced you will have to raise the number of RPM since with the variable of the amount or angle of the shovels the improvement will be of very little percentage.
As they have very well suggested, Yamaha, Bombardier, etc. they use 3 bladed turbines with more overlap but their RPM are in other ranges ... !!!
I think that with the impellers that they use, (stationary engines 200 c.c., 4T, 6.5 / 7 HP) the achieved performance is acceptable.
You do not have the possibility to install a 2T and 6000/6500 RPM impeller with the original set ...?
I hope new advances, I trust that you will get some Mph more to your Mokai, thanks for sharing your experience, greetings from Patagonia Argentina, Nilton Farias

 
🤦🏼‍♂️ Chuck 🤷🏻‍♂️

Offline Heavynets

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Re: Performance Impeller
« Reply #88 on: April 08, 2018, 12:05:42 PM »
Tom, have you had a chance to try the 12 blade, 2 stage, design or have you given up on 3D printed impellers?

Offline Painlesstom

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Re: Performance Impeller
« Reply #89 on: April 08, 2018, 09:05:47 PM »
I haven't had a chance to yet, this time of year leaves me little river time for playing. I am anxious to find out what it does though, and will be sure to post the results here. I see you are back up and printing, looks good!  \./8
Tom

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