$txt['youtube'] = 'YouTube'; $txt['youtube_invalid'] = '#Invalid YouTube Link#'; Performance Impeller

Author Topic: Performance Impeller  (Read 19240 times)

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Offline Painlesstom

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Re: Performance Impeller
« Reply #60 on: November 01, 2017, 07:06:03 AM »
I already did that a couple years back.  ;)
Tom

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Offline Ctmokai

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Re: Performance Impeller
« Reply #61 on: November 01, 2017, 07:58:40 PM »
Looks great Tom. Sooooooo many calculations. Appreciate your work 👍

Offline Painlesstom

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Re: Performance Impeller
« Reply #62 on: November 02, 2017, 02:17:40 PM »
Thanks!  :)

I made it out today to test the next one in line. This is the 8th version in 4 blade design, but the 2nd 4 blade profile I've tested. I saw 4700 rpm, which was up from my normal 4200 in the ES-kape, and my usual speed of 17 mph coming back down. No breakthrough or anything, but it was nice to see a 4 blade impeller perform so well. Next test will be a 5 blade.  \./8

<a href="http://www.youtube.com/watch?v=k4fTpxt7E6k" target="_blank">http://www.youtube.com/watch?v=k4fTpxt7E6k</a>
Tom

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Offline Ctmokai

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Re: Performance Impeller
« Reply #63 on: November 02, 2017, 07:36:56 PM »
Whether or not you make any performance gains - you have to love your job !!!  \./8

Offline Painlesstom

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Re: Performance Impeller
« Reply #64 on: November 02, 2017, 07:46:23 PM »
Yes! As long as I don't have to paddle!!!!  :D
Tom

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Offline Painlesstom

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Re: Performance Impeller
« Reply #65 on: November 07, 2017, 12:19:09 AM »
Got some exercise today, at least a half mile worth. lol

Printed at 40% infill to see how it would hold up, lesson learned.

<a href="http://www.youtube.com/watch?v=vWjbhZfcrXU" target="_blank">http://www.youtube.com/watch?v=vWjbhZfcrXU</a>
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Offline riverman

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Re: Performance Impeller
« Reply #66 on: November 07, 2017, 07:47:54 PM »
Not sure what that means, but I'm assuming not a high enough concentration of bonging agent? Good thing you weren't too far away when it exploded.   

Offline bizler

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Re: Performance Impeller
« Reply #67 on: November 07, 2017, 09:58:15 PM »
Iíve been thinking about this subject and the objective, getting higher performance out of our EX21-17 engine and pump combination.  The spec. for the stock EX21 is maximum 7 hp at 4000 RPM.  The EX 17 head adaptation has increased the hp a bit as shown by a change in rpm with the stock impeller from about 3850 to about 4380 after warm up, roughly 400 pm or 10%.  Mokai did a respectable job in matching the prop pitch and efficiency to use the maximum hp of the stock engine.  It would seem to me that choosing a pitch that results in any higher rpm would not improve performance, (speed). Therefore I would propose increasing the pitch by maybe 10% with 6 blades or 5 blades order to load the engine a bit more to utilize the peak power, 4000 rpm.

I believe that maximizing total surface area of the impeller blades in contact with the water, without creating cavitation will have the greatest impact on efficiency. So making the blades nearly as wide as the wear ring would be prudent, which I believe you have done, Tom.

Just a few thoughts...    :)

Offline Painlesstom

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Re: Performance Impeller
« Reply #68 on: November 07, 2017, 10:12:59 PM »
Not sure what that means, but I'm assuming not a high enough concentration of bonging agent? Good thing you weren't too far away when it exploded.   

The printing process involves layering a bead of melted plastic into the eventual object. Options to honeycomb the inside areas for faster print time, less mass and material used, is called infill. 100% being completely solid, and anything less you end up with those honeycombs in respectively sized proportions. Too little infill and the part is too weak to stay intact. I tested a 5 blade today that I printed back at the 70% infill and had no problems. 4600 rpm and 16 mph this time.

Bill, I agree that higher rpm isn't the target. I don't want to run the engine faster for longevity reasons too, so the 4000 zone is where I'd like to end up also. The more I test, the more I'll gain understanding about what blade profiles work and hopefully narrow all that info into a design that provides a little more than stock. Having a ton of fun along the way too!  \./8
Tom

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Offline bizler

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Re: Performance Impeller
« Reply #69 on: November 07, 2017, 10:42:47 PM »
Just curious, do you know what the pitch is on the stock impeller? 

Offline Painlesstom

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Re: Performance Impeller
« Reply #70 on: November 07, 2017, 11:06:56 PM »
No idea.
Tom

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Offline Rottweilerman

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Re: Performance Impeller
« Reply #71 on: November 08, 2017, 12:22:54 AM »
Impressive work Tom \./8    If and when you come up with a more efficient design you may displace Mokai replacement parts and you probably won't  get a Christmas card from Marie :))

I'm really impressed :)

John

Offline Painlesstom

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Re: Performance Impeller
« Reply #72 on: November 08, 2017, 12:44:21 AM »
Thanks John. I haven't gotten a Christmas card from Marie in many many years.... I would bet money I'm on a hit list somewhere in her office though.  :D

Be entertained for now, be impressed if I actually find one that works better.  ;)
Tom

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Offline Heavynets

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Re: Performance Impeller
« Reply #73 on: November 08, 2017, 11:10:18 AM »
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. 

 

Offline bizler

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Re: Performance Impeller
« Reply #74 on: November 08, 2017, 11:50:58 AM »
No idea.

If we can assume that the design spec. was 17 mph at 4000 rpm, i.e. the theoretical maximum speed, ignoring drag, I calculate the pitch to be .561Ē /blade or 4.488Ē /rev.  I donít have my impeller in hand to verify this but it seems about right in my minds eye.  ;)