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Improving Your Mokai

Shop Talk => Jet Pump Discussion => Topic started by: cjyoung on July 07, 2015, 01:16:09 AM

Title: Performance Impeller
Post by: cjyoung on July 07, 2015, 01:16:09 AM
There are several posts about engine performance for the Honda engine in my mokai, but I haven't seen anyone talking about changing out impellers for more torque, top speed, etc... My experience with boats has mainly been outboard motors where prop pitch and size is very important to overall boat performance.  I assume that this is true for jet drives as well.  Does anyone on here have experience with tuning or replacing their impeller to achieve more top speed?
Title: Re: Performance Impeller
Post by: Painlesstom on July 07, 2015, 10:36:36 AM
Since Mokai makes their own pump, there are no replacement impellers. As a result, nobody is keen on the idea of modifying the one they have and risk ruining it. You MIGHT be able to talk Mokai into selling just an impeller, but I wouldn't count on that being an easy task. Then unless you have special tools, you could not tear the pump down to change the impeller. I firmly believe there is a ton of performance to be gained from a more efficient impeller/pump design, but so far the market has been way to small for anyone with the capability to be interested in taking it on. Just isn't worth the investment for the big companies to mess with, and too big of an undertaking for someone like me to think about it.
Title: Re: Performance Impeller
Post by: Heavynets on July 17, 2015, 11:28:48 AM
I've thought about that myself.  A new turbine could be 3-D printed for probably less than $200.  The problem is that I have know idea of what a better design would be.  Trial and error R&D could be quite expensive.

Peter (from Russia) made a turbine for his boat that only had 3 blades.  I wonder if that would be an improvement over Mokai's design.
Title: Re: Performance Impeller
Post by: Painlesstom on July 17, 2015, 12:31:44 PM
A three blade overlapping impeller is more efficient that what Mokai did. If it wasn't, then EVERY other jet boat manufacturer would not make them that way. Those people use what works, they've spent millions in R&D to figure that out. SeaDoo, Polaris, Yamaha, Berkeley, Hamilton.. Every jet pump I've ever seen has a 3 or 4 blade impeller that has a varying degrees of overlap. I don't think that the new impeller could be made to work with the factory wear ring design though, it's too shallow and at a taper. Real jet pump impellers are much deeper with no taper, I'm sure this affects performance too.

So.... there really needs to be a whole new design to make use of the more efficient technology. While 3D printing could be used to come up with a semi working prototype, cost would prevent the next level to source out castings and machining to come up with a product. Then you have to sell it and make a profit. If there were millions of Mokai boats out there, there would be a market for something.. with only thousands, you would be spending allot of money with no return. That's just how I see it anyhow.

I feel if Mokai really wanted to make a better boat, they would quit farting around with servos and non functional cold air intakes and address the potential the boat has while fixing the problems that have been ongoing since the beginning. Redesign the pump so it's a real jet pump, make it so it will last and not fill up with water after a few hours of use....
Title: Re: Performance Impeller
Post by: Odie on July 17, 2015, 05:34:16 PM
I'm curious, is the current impeller investment casting? 
Title: Re: Performance Impeller
Post by: Heavynets on July 17, 2015, 09:32:48 PM
I wasn't planning on going into business, just make one for me.  The 3D printed turbine is the final thing, not just for a a prototype.  It may not be the optimal design due to Mokai's initial design limitations, but it may be an improvement over the current design.  It will probably require a little machining, but that's not a deal breaker for me, if I decide to do it.

if it works the CAD file could be made public for anyone that wants to have one made.  Now if I just knew the optimal pitch.
Title: Re: Performance Impeller
Post by: Painlesstom on July 18, 2015, 01:12:58 AM
How strong would the 3D printed part be? The impeller is the "nut" that tightens the axle to the bearings and needs to withstand that as well as the shaft seating to it and tightening down against it. Then there is the wear factor if you're running through any debris or shallows. Would love to see somebody make it happen though, if I had the ability and know how I would have played with this a long time ago.

Title: Re: Performance Impeller
Post by: Heavynets on July 18, 2015, 09:00:17 AM
Strength is a function of not only the material, but also the design and directions of the various loads.  It is therefore hard to answer your question.  As for the material, I would probably use 420 Stainless Steel infused with bronze.  It has a final composition of approximately 60% steel and 40% bronze.  This is a standard product for one 3D printing supplier.  However, almost anything is available including carbon graphite, kevlar and fiberglass impregnated plastic.
Title: Re: Performance Impeller
Post by: Painlesstom on July 18, 2015, 09:21:45 AM
3D printing has come a long way since I last paid attention to it. Did not know metals were an option now, this would be a game changer if you have a source for the process at an affordable level. Is the finished stainless/bronze piece able to bend, or is it too brittle? Wondering how it would handle impact, such as hitting a rock at 4000 rpm. Interesting stuff.  ;D
Title: Re: Performance Impeller
Post by: Odie on July 18, 2015, 07:20:51 PM
Investment Casting  + FDM is a marvelous marriage of past and present. It offers a low production cost after all engineering plus trial and error is done.  The cost of the engineer and trial and error?
Title: Re: Performance Impeller
Post by: XYZER on July 21, 2015, 09:15:07 AM
We have 2 metal 3D printers here at work. It is currently printing in Inconel. There is no strength problems. We have made a few turbo impellers out of the Inconel and not sure how testing has gone. Getting a model with the improvements is part of the problem. You could end up making several before you found the sweet one for your target rpm. Got a model?
https://www.youtube.com/watch?v=DXh1AbX5j20
Title: Re: Performance Impeller
Post by: Heavynets on July 22, 2015, 11:15:08 PM
(http://i698.photobucket.com/albums/vv346/Heavynets/Screen%20Shot%202015-07-22%20at%205.19.43%20PM_zpsypbbqcx1.jpg)

Here is a rough sketch of a 5 blade turbine in a 3D CAD format (STL file).  I may try to design one this winter.  Too busy right now.
Title: Re: Performance Impeller
Post by: Painlesstom on July 22, 2015, 11:57:44 PM
Very impressive, wish I had learned CAD. Was good at mech drafting / drawing when I was in school, but I wanted to play with wrenches and grease instead.

Why 5 blades? There are 8 now, the "standard" on many other pumps is 3. The fun part is figuring out what thread size is inside it, left hand threads at that. I have several pumps I'm rebuilding right now, will have to see if I can figure that out.

Title: Re: Performance Impeller
Post by: Hillbilly on July 23, 2015, 07:07:42 AM
Mine has eight.  Thought about cutting four off from a spare
Title: Re: Performance Impeller
Post by: Painlesstom on July 23, 2015, 07:52:05 AM
Cutting out 4 without making the others wider to fill the gap, would just move half as much water at a faster rpm in my opinion. You aren't changing anything to make up for the 4 missing blades.
Title: Re: Performance Impeller
Post by: Heavynets on July 23, 2015, 10:08:09 AM
I played with this calculator.  http://www.vicprop.com/displacement_size.php

It's for standard props, not turbines, but it gave me a "feel" for how turbine design might work.  The number of blades increases as the diameter goes down.  Given the small diameter limitation in the Mokai, I'm GUESSING more blades (more than 3) MIGHT help.

Besides, I have to believe that Mokai didn't just randomly happen upon their design. Surely there was some logic involved and were aware of jet ski designs.  I doubt if they had the time or money to develope the optimal design.  However, it is probably close, dispite being a compromise that considered time, cost and performancee and limitations due to other design considerations. All engineering designs go through the same compromises and no two engineers will always make the same choices.

I would be amazed if even 2 mph can be gain by a new design.  And there most likely will be a tradeoff in ______?????  I just enjoy messing with this stuff.  Maybe I can come up with one that the blade number and pitch can be adjusted for R&D purposes.
Title: Re: Performance Impeller
Post by: Painlesstom on July 23, 2015, 07:44:54 PM
Well, if anyone could figure out a more efficient impeller, you would be the one with the brains to make it happen. This process is beyond my cut and paste, trial and error methods. Thanks for sharing your engineering expertise, I know there are several people watching this thread to see what you do one day.  \./8
Title: Re: Performance Impeller
Post by: cjyoung on August 31, 2016, 01:50:13 AM
Thanks for the good discussion.  Sounds like I'm stuck with whatever it came with from the factory.  Guess I'll focus on the engine instead.
Title: Re: Performance Impeller
Post by: Painlesstom on August 31, 2016, 07:34:06 AM
There's not much you can do with the Honda engine for performance other than keeping it tuned up. Wear ring makes a huge difference so make sure it's in good shape with no grooves. I always have aluminum rings in stock if you need one.
Title: Re: Performance Impeller
Post by: Heavynets on October 17, 2016, 02:51:34 PM
"The fun part is figuring out what thread size is inside it, left hand threads at that. I have several pumps I'm rebuilding right now, will have to see if I can figure that out."

Tom, can you post a drawing with the inside dimensions of the impeller?
Title: Re: Performance Impeller
Post by: Painlesstom on October 17, 2016, 03:15:22 PM
I just assembled the two I have on hand, but have four more inbound, I'll see what I can come up with in a week or so.
Title: Re: Performance Impeller
Post by: Painlesstom on October 19, 2016, 02:52:45 PM
Here are some pics, hope they help. The thread gauge is showing 14 TPI SAE thread pitch.
Title: Re: Performance Impeller
Post by: Painlesstom on October 24, 2016, 10:55:26 AM
Just got a test nut in. The impeller thread is LH 7/8-14
Title: Re: Performance Impeller
Post by: Heavynets on October 26, 2016, 12:40:56 AM
(http://www.improvingyourmokai.com/Users/johnkrukemeier/Desktop/Screen Shot 2016-10-25 at 11.44.16 PM.png)

Would this work?  The stray lines are because I need to update my graphics card.  I'll add the blades later after I'm sure what the base cone looks like.
Title: Re: Performance Impeller
Post by: Painlesstom on October 26, 2016, 07:10:24 AM
Picture is a little small, hard to see. Any way you could get it larger?
Title: Re: Performance Impeller
Post by: Heavynets on October 26, 2016, 09:24:03 AM
No, but I should have a new graphics card in about 2 weeks.
Title: Re: Performance Impeller
Post by: Heavynets on October 26, 2016, 09:31:10 AM
(http://www.improvingyourmokai.com/Users/johnkrukemeier/Desktop/Screen Shot 2016-10-25 at 11.44.16 PM.png)

Is this any better?
Title: Re: Performance Impeller
Post by: Painlesstom on October 26, 2016, 09:39:24 AM
I'm seeing the exact same picture. File size and resolution are the same. Windows has a Snipping Tool that works great, not sure what you have though. But looking at that I realized I didn't provide the measurements to locate the thread area, so I'll get some more numbers for you today.
Title: Re: Performance Impeller
Post by: Hillbilly on October 26, 2016, 10:19:07 AM
Enjoying this discussion.  Thanks, guys.
Title: Re: Performance Impeller
Post by: Painlesstom on October 26, 2016, 10:27:03 AM
Maybe this will have some more info for you.
Title: Re: Performance Impeller
Post by: Heavynets on October 27, 2016, 05:55:31 PM
The dimensions in your photos and the sketch don't appear to agree.  The few dimensions that I can get of my impeller are different yet.  Probably not a big deal at this point.  Maybe this drawing looks better?

(http://www.improvingyourmokai.com/Users/johnkrukemeier/Pictures/Impeller Drawing v2.jpg)
Title: Re: Performance Impeller
Post by: Heavynets on October 27, 2016, 06:04:03 PM
This screen shop may be bigger, but will have graphic card issues.
Title: Re: Performance Impeller
Post by: Painlesstom on October 27, 2016, 08:13:20 PM
Dial caliper isn't always the most accurate for blueprinting something. I was also measuring a different impeller. The two critical measurements that I saw in your drawing that could be a problem, would be the .771 front opening and .298 recess in the back. Those two should be safer at .780 and .280 respectively. Other than that I think it looks great. Cad is something I always wish I had spent the time to learn, especially since I took mech drafting and drawing in high school.
Title: Re: Performance Impeller
Post by: Heavynets on October 27, 2016, 10:20:48 PM
I'll change those dimensions and then start designing the blades.

I've done a lot of CAD work, most of it in 2-D.  The 3-D software I'm using now is free, but more powerful than the ones I paid thousands of dollars for.  I've only used it a short while and just starting to figure it out.  Old brains and new technology don't mix well.
Title: Re: Performance Impeller
Post by: Painlesstom on October 27, 2016, 11:26:37 PM
Great, looking forward to seeing what you come up with.  \./8

What is the free software you are using? Got a link?
Title: Re: Performance Impeller
Post by: Heavynets on October 28, 2016, 11:06:42 AM
Fusion 360, it's from Autodesk the makers of AutoCad.  Here is a link.

http://www.autodesk.com/products/fusion-360/overview

It is a bit overwelming.  It includes CAM, animation and finite element analysis capabilities.  I suggest you start with 123D design software.  It's free, much simpler, but frustrating on more complicated designs.  It too is from Autodesk.  Its link is: http://www.123dapp.com/design

A lot of good instructional videos for both on YouTube.
Title: Re: Performance Impeller
Post by: Painlesstom on October 28, 2016, 06:53:14 PM
Awesome, thanks. Now to see how fast I pick up on it. I used to play with 3d Max years ago for animation, I'm sure this is a little less complicated. Will be a brain teaser for sure.  :D
Title: Re: Performance Impeller
Post by: riverboater on February 09, 2017, 12:06:45 AM
In preparation for an assault on an impeller redesign, I have been doing a little homework. I have also been emailing with Peter to better understand the work he did on his boats. I think a new impeller will also require a longer wear ring area and different stator / housing. As a start, I began by modeling the existing unit.


Cheers, Steve


<iframe src="https://myhub.autodesk360.com/ue29b4221/shares/public/SHabee1QT1a327cf2b7ad948c8522c679c5d?mode=embed" width="800" height="600" allowfullscreen="true" webkitallowfullscreen="true" mozallowfullscreen="true"  frameborder="0"></iframe>
Title: Re: Performance Impeller
Post by: Painlesstom on February 09, 2017, 07:12:06 AM
Nice work! Excited to see what you come up with.  >:D
Title: Re: Performance Impeller
Post by: Hillbilly on February 10, 2017, 07:44:12 AM
Exciting stuff, Riverboater.  This may be the next big step.  Looking forward to following along.  Thanks
Title: Re: Performance Impeller
Post by: riverboater on February 11, 2017, 04:42:09 PM
Thanks guys. Updated model with the steering nozzle.

Will start on the replacement design now. Don't hold your breath though... I still have a day job which supports all of my bad habits like having food with my meals and such.

Cheers, Steve
Title: Re: Performance Impeller
Post by: mosski on September 07, 2017, 11:40:18 AM
Any recent updates on the jet impellers?  Sounds like a interesting direction.
Title: Re: Performance Impeller
Post by: Painlesstom on September 07, 2017, 07:29:46 PM
There is a prototype design that is ready for the testing phase, but haven't had time to post about it here and see if there are any members who would be interested in contributing a few $$ toward the $320 price tag to have a stainless 3d print done that I can actually test. I'll post some pictures of it later when I get home.
Title: Re: Performance Impeller
Post by: riverman on September 08, 2017, 12:16:14 AM
I'm good for 50, now we just need another half dozen members to pitch in, let me know where/when to send a check.
Definitely worth the money to experiment on a new design that could improve some level of performance.     
Title: Re: Performance Impeller
Post by: Painlesstom on September 08, 2017, 07:13:36 AM
Cool, sounds good. As soon as there are enough people to make it happen, then everyone can submit their contribution. Just bear in mind it could be a complete flop and prove to be no improvement at all, such is the reality of R&D. LOL

The blades are much wider with some overlap, and only 7 blades now instead of 8. It looks like it could be more efficient but that's what testing is for. Excited to try it out eventually.
Title: Re: Performance Impeller
Post by: Jpmichigan on September 08, 2017, 08:36:23 AM
you can count me in for $50 also.. when we get enough people send me who to pay pal.
Title: Re: Performance Impeller
Post by: Painlesstom on September 08, 2017, 08:52:23 AM
you can count me in for $50 also.. when we get enough people send me who to pay pal.

 \./8
Title: Re: Performance Impeller
Post by: mosski on September 13, 2017, 01:01:08 AM
I'm in for $50 if this new impeller will work on the new Mokai ES-Kape.
Title: Re: Performance Impeller
Post by: SgtBadBob on September 15, 2017, 11:19:28 AM
I am looking for any speed improvement. if this is a really good go factor than count me in for 50. >:D
Title: Re: Performance Impeller
Post by: flathorn on September 15, 2017, 11:03:59 PM
I am good for  $100  to help out.

Byron Mlller
Title: Re: Performance Impeller
Post by: Painlesstom on September 15, 2017, 11:53:48 PM
Thanks guys, I'm excited to do the testing on this. Heavynets posted this earlier, so once I get that impeller to test we'll see how that works out and go from there. I will definitely keep everyone posted here with any and all updates.  \./8

I am having an impeller printed out of a carbon fiber reinforced nylon.  I should have it to Tom in a few week so he can try it out.  If it's strong enough, it will only cost about $75 or less.  I wanted to use polycarbonate. However, the cost due to its difficulty to print made me switch materials.  The carbon filled nylon is about 80% the strength of polycarbonate, but may handle gravel better.  Tom is raising money for a bronze impregnated stainless steel impeller. 

The pitch angle, as in all props / propellers, varies with the diameter.  Whether or not this design is "better" will probably depend upon the user.  Some want top speed, some want power, etc.  What you get will also depend upon the total weight of the boat with operator and modifications made to the boat.  Like Tom said, we'll just have to wait and see. 

As I have stated before, I doubt if this design will be significantly better or worse than the factory design. However, (if made from a plastic) it will be significantly cheaper should you ever have to replace your impeller.
Title: Re: Performance Impeller
Post by: Ctmokai on September 25, 2017, 07:50:00 PM
Count me in for 50.  \./8 nothing ventured - nothing gained.
Title: Re: Performance Impeller
Post by: Painlesstom on September 25, 2017, 08:42:11 PM
Great, thanks for that. I've got the original and new carbon reinforced prototypes that I plan to test as soon as time permits. I'm counting on having to paddle back, so also waiting on ideal conditions for that too.  :D I am excited to see what the results will show, the new design utilizes the entire area of the wear ring, instead of just the center 50%. Hoping it will be more efficient, it sure sounds good on paper and looks good to the eye.  >:D  Regardless of what the plastic version testing shows (I know full throttle is going to kill it, or if by some chance it doesn't I know the amount of flex will hinder it's true potential) I will be moving forward with the bronze impregnated stainless print. I want to know what this thing will truly do. Thanks again to Heavynets for all the time, $$, and work of putting this in motion.  \./8
Title: Re: Performance Impeller
Post by: flathorn on September 27, 2017, 12:43:44 PM
Is there a place to send our money to help with this yet?
Title: Re: Performance Impeller
Post by: Painlesstom on September 28, 2017, 12:10:47 AM
One submission in. - $50  \./8
Title: Re: Performance Impeller
Post by: Painlesstom on October 06, 2017, 11:57:11 PM
Another contribution in today for $100  \./8

Two impellers on the way for testing right now, will update when I have more to share.
Title: Re: Performance Impeller
Post by: Painlesstom on October 31, 2017, 09:53:24 PM
I know I've been quiet about this for a while, but that's because I've been immersed with learning CAD and getting familiar with the 3D printer I now am the proud owner of. I couldn't justify blowing $$$ on paying $35 a try for each impeller print ordered, as much testing this endeavor is going to incur, I had no problem justifying the expense of just buying a 3D printer.. I called it a business expense, a birthday present (was the 27th!!  ;D ), and a tool for future work and hobby related projects. I've been wanting to know CAD for many years, but I haven't wanted to LEARN it.. I've finally jumped in and broke the ice, my feet are wet now and it's starting to get fun. Thanks to John (Heavynets), for modeling the hub and starting this, I've been able to use his hub model to base my blade profiles on.  Have several versions to test now, so time and weather permitting there should be some entertaining testing videos in the near future. This ride might have a fun destination, or it could just be a fun ride without a finale, but ultimately there will at least be a alternative way to source a replacement impeller, should one get damaged beyond repair, if Mokai refuses to sell one.
Title: Re: Performance Impeller
Post by: CC-Coder on October 31, 2017, 10:18:47 PM

Tom,
Happy 27th!! (Hehe) Once again, thank you for all you do. You make owning a Mokai feel like one of the best investments I've ever made. Hope your new CAD-n' / printer hobby result in a successful design. Keep up the great work, so we can all go play!!  :) ;) \./8
Title: Re: Performance Impeller
Post by: Painlesstom on October 31, 2017, 11:11:02 PM
Thanks, Chuck, very glad to hear that. I plan on continuing the fun, and CADn't be happier!  :D
Title: Re: Performance Impeller
Post by: CC-Coder on October 31, 2017, 11:22:50 PM
Will you be making your own, one-of-kind quadcopter's as well?
Title: Re: Performance Impeller
Post by: Painlesstom on November 01, 2017, 07:06:03 AM
I already did that a couple years back.  ;)
Title: Re: Performance Impeller
Post by: Ctmokai on November 01, 2017, 07:58:40 PM
Looks great Tom. Sooooooo many calculations. Appreciate your work 👍
Title: Re: Performance Impeller
Post by: Painlesstom 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

http://www.youtube.com/watch?v=k4fTpxt7E6k
Title: Re: Performance Impeller
Post by: Ctmokai on November 02, 2017, 07:36:56 PM
Whether or not you make any performance gains - you have to love your job !!!  \./8
Title: Re: Performance Impeller
Post by: Painlesstom on November 02, 2017, 07:46:23 PM
Yes! As long as I don't have to paddle!!!!  :D
Title: Re: Performance Impeller
Post by: Painlesstom 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.

http://www.youtube.com/watch?v=vWjbhZfcrXU
Title: Re: Performance Impeller
Post by: riverman 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.   
Title: Re: Performance Impeller
Post by: bizler on November 07, 2017, 09:58:15 PM
I’ve 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...    :)
Title: Re: Performance Impeller
Post by: Painlesstom 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
Title: Re: Performance Impeller
Post by: bizler on November 07, 2017, 10:42:47 PM
Just curious, do you know what the pitch is on the stock impeller? 
Title: Re: Performance Impeller
Post by: Painlesstom on November 07, 2017, 11:06:56 PM
No idea.
Title: Re: Performance Impeller
Post by: Rottweilerman 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
Title: Re: Performance Impeller
Post by: Painlesstom 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.  ;)
Title: Re: Performance Impeller
Post by: Heavynets 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. 

 
Title: Re: Performance Impeller
Post by: bizler 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 .561” /blade or 4.488” /rev.  I don’t have my impeller in hand to verify this but it seems about right in my minds eye.  ;)
Title: Re: Performance Impeller
Post by: Heavynets 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.
Title: Re: Performance Impeller
Post by: Painlesstom 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
Title: Re: Performance Impeller
Post by: Heavynets 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?
Title: Re: Performance Impeller
Post by: Painlesstom 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
Title: Re: Performance Impeller
Post by: Heavynets 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?
Title: Re: Performance Impeller
Post by: Painlesstom 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.
Title: Re: Performance Impeller
Post by: Painlesstom 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
Title: Re: Performance Impeller
Post by: Maritimer 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 ==
Title: Re: Performance Impeller
Post by: CC-Coder 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
Title: Re: Performance Impeller
Post by: Painlesstom 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.
Title: Re: Performance Impeller
Post by: Painlesstom 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.
Title: Re: Performance Impeller
Post by: pirata.sur 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.

 
Title: Re: Performance Impeller
Post by: CC-Coder 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

 
Title: Re: Performance Impeller
Post by: Heavynets 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?
Title: Re: Performance Impeller
Post by: Painlesstom 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
Title: Re: Performance Impeller
Post by: CC-Coder on June 10, 2019, 02:29:52 PM
Would the new design of the two piece pump in the Mokai 2.0 be easier to test future 3-D impellers. Maybe even 3-D print a 2 piece pump too?
Title: Re: Performance Impeller
Post by: Painlesstom on June 10, 2019, 02:42:45 PM
Not that I can think of, from what I've seen the impeller etc. is assembled the same way and being able to split the pump makes no difference other than adding another step that is unnecessary. All the impellers I've tried led me to the conclusion there is no better profile within the stock wear ring size and pump intake volume size. It was fun exploring different designs, but it ultimately led to a dead end. 
Title: Re: Performance Impeller
Post by: CC-Coder on June 10, 2019, 03:37:22 PM
Guess my thought was whether it might be easier to duplicate the original now that it's split in two. Not looking for performance improvements but a replacement in case something would happen to my pump.  (Just pondering the $1800 question...Lol)
Title: Re: Performance Impeller
Post by: Painlesstom on June 11, 2019, 09:19:08 AM
The pump being two pieces now just makes assembly a little easier, and repair much easier later when rebuild or fixing broken cone screws is necessary. Also gives the ability to replace that tail section should someone hit a rock, that's the area that would be damaged. So instead of protecting the pump, they ensured a pump guard wouldn't be possible and they just created a way to generate a sale for replacement parts.