Thread Tools
This thread is privately moderated by sundogz, who may elect to delete unwanted replies.
Feb 04, 2017, 08:46 PM
Platinum Card Member
sundogz's Avatar
Thread OP
Shoot, I sent him a PM about posting it but got sidetracked. I'll get the text written and get it done right away. I have a prelim side view composite cut/paste drawing to give him an idea of how it will look. We'll scale once we decide what size impeller it will have.
Sign up now
to remove ads between posts
Feb 04, 2017, 10:53 PM
Platinum Card Member
sundogz's Avatar
Thread OP

Basic pump body design


Of all the different shapes of jet bodies I've encountered, this is the best basic design. Think Graupner5 or MHZ-4 with an integrated motor mount. It's not as sexy as some but it will be easy to install and very strong, since it spreads the torque over the largest area and strengthens the hull where need be. When you hang a motor on a jet drive you need all the stability and strength you can muster. Except maybe for very thin hulls with the largest scale pumps you shouldn't need to reinforce the hull bottom before installation. I had considered a design that could facilitate a boat with a slanted transom, but the benefits of this design outweigh the need to cater to that type hull. If you have a hull with a slanted transom, box it in or get a hull with a 90 degree transom. I've already had to compromise.

You still have two holes to make in the hull, but it won't require a template. Pardon my cut and paste diagram, but this should give Juss enough info to get started. I'll get the dimensions once we decide on what size impeller the prototype will have. I'm thinking 35 or 45mm (but am open to opinions). Large openings on the sides of the coupler bay leave plenty of access to the coupler, with a narrow strip on top and 'wings' beneath to strengthen the motor mount. This is necessary so we can keep the motor mount pad thin enough to facilitate a thrust bearing. Neat, non-complicated and (I'm hoping) easy to print.

Juss, if you'll please imagine and draw the cutaway view using those typical from your thread it will speed things along. The opening on the bottom for the intake will be rectangular with (barely) rounded corners, and an integrated wedge to direct water up into the impeller chamber. The stator housing will have an integrated wear ring that can be shortened by the builder to facilitate differing transom thicknesses. Copy your stator fins and steering nozzle to this model to give us something to work with.
Last edited by sundogz; Apr 02, 2017 at 03:00 PM. Reason: Added graupner 5 w/ mount
Feb 05, 2017, 07:29 AM
Platinum Card Member
sundogz's Avatar
Thread OP
If you've already read the previous post, read it again. I had to edit/update the text and pics.
Last edited by sundogz; Feb 05, 2017 at 07:30 AM. Reason: sp
Feb 05, 2017, 10:44 AM
Registered User
who's Jeff?

Sundogz, this looks good for now. Can you draw in some hidden lines to show me what you were thinking for the ramp profile?

I say lets start at 35mm. what diameter shaft? 4 or 5mm?

That wear ring, what kind of bolt pattern? 4 or 6 bolt?

how long do we want the bottom intake? I figured we'll just make the width the same as the impeller so in this case if we go 35mm diameter we'll make the intake 35mm wide.
Feb 05, 2017, 10:47 AM
Registered User
Quote:
Originally Posted by unusual_rc
I am an (3DCAD) engineer myself, and waiting for my Prusa i3MkII
When is your Prusa supposed to be in? I would love to get some feedback on how well it prints ABS. I've been thinking of getting one as well but I'm a bit concerned on how well it will print ABS as its not an enclosed environment.

Also, what software do you use for CAD?

Justin
Feb 05, 2017, 11:41 AM
Platinum Card Member
sundogz's Avatar
Thread OP
Quote:
Originally Posted by JUSS10B
who's Jeff?

Sundogz, this looks good for now. Can you draw in some hidden lines to show me what you were thinking for the ramp profile?

I say lets start at 35mm. what diameter shaft? 4 or 5mm?

That wear ring, what kind of bolt pattern? 4 or 6 bolt?

how long do we want the bottom intake? I figured we'll just make the width the same as the impeller so in this case if we go 35mm diameter we'll make the intake 35mm wide.
Sorry, that's my drummer's name. I couldn't sleep so started on that around 4AM and didn't catch it when I edited at 6:30

35mm is fine. Nothing special about the ramp profile - leave everything straight. The stator housing w/wear ring should have 6 screws. When you draw the cutaway view, start at impeller width, keep the channel straight (will not get larger) and you'll wind up with whatever size opening it comes to (this includes the ramp). There's a little bit of flare (we talked about this on the other site) where the water enters the ramp for a smoother transition. What software do you use to draw these with?
Last edited by sundogz; Feb 05, 2017 at 12:34 PM.
Feb 05, 2017, 03:10 PM
Platinum Card Member
sundogz's Avatar
Thread OP

Motor, impeller & shaft size and screw spacing chart



Shaft size / Impeller size / Motor can diameter / Screw spacing (all in millimeters)


2 --- 15 --- 20 ---16
3 --- 25 --- 28 --- 19
4 --- 35 --- 36 ---- 25
5 --- 45 --- 40 ---- 25
6 --- 55 --- 40L & 56 --- 30
7 --- 65 --- 56 & I.C. engines --- 30
Last edited by sundogz; Feb 05, 2017 at 05:08 PM.
Feb 05, 2017, 03:55 PM
Platinum Card Member
sundogz's Avatar
Thread OP
OK, we'll be talking about a 35mm impeller prototype whenever we're addressing this project. A 4mm shaft is plenty stout for this application. I'll go back and put shaft sizes on the motor/impeller size chart.
Feb 05, 2017, 11:15 PM
Just Plane Nutts
AirDOGGe's Avatar
How about if the mount had steps to automatically center the motor when tightened...Slots could then be used for the mounting bolts, and would allow for multiple bolt patterns too. This example would center 36 and 28 millimeter dia. motors...

Note that I only show the mount plate here and not the rest of the pump housing...
Last edited by AirDOGGe; Feb 05, 2017 at 11:26 PM.
Feb 06, 2017, 09:38 AM
Registered User
Interesting thought AirDOG, my only concern with that is that some motors have a chamfered or rounded edge on the mounting face. That could cause some alignment issues. I think it would just be easier to try and include two sets of mounting holes on each drive that could use two different motors. That way the holes will still along the motor. in all honesty, I would probably make sure the coupler is tightened down first and them tighten the motor screws last, that way the shaft aligns the motor.

I'll try and get some section views drawn up in draftsight in the next day or so for review. Then we can tweak and move in to 3D modeling.
Feb 06, 2017, 10:52 AM
Platinum Card Member
sundogz's Avatar
Thread OP
Quote:
Originally Posted by AirDOGGe
How about if the mount had steps to automatically center the motor when tightened...Slots could then be used for the mounting bolts, and would allow for multiple bolt patterns too. This example would center 36 and 28 millimeter dia. motors...
Note that I only show the mount plate here and not the rest of the pump housing...
Now that's the kind of thinking I'm talking about! Outside the box, open mind, what if- stuff. But I agree with Juss about chamfered edges, and you might want to use an outrunner with a strange diameter But slots would scale....everything else is so far - bearings, shaft etc. This might be a one (plan) fits all project after all. We'll know more after testing - the shaft sizes are a little smaller than motor shafts as it is, but I've never experienced a twisted jet shaft. (see note 1) If anything we might have to shift shaft sizes up one millimeter (65mm impeller w/ 8mm shaft, 55mm to 7mm etc. but I doubt it will be necessary.

1. I recently read where a fellow in the old gas boats forum twisted the shaft on a 40mm KNB Powerjet with a Zenoah. But it wasn't the Zenoah's fault - the coupler was rigid and not aligned properly. He's since used two collets with flex shaft in between and all was well. Or you can use a shock coupler (has rubber inserts) or just align the damn thing properly in the first place.
Feb 06, 2017, 11:04 AM
Just Plane Nutts
AirDOGGe's Avatar
Quote:
Outside the box, open mind, what if- stuff. But I agree with Juss about chamfered edges, and you might want to use an outrunner with a strange diameter
Any motors like that would still work on it like a regular flat plate. We already use mounts with slots or with hole we have to open up to fit certain motors. Most of the inrunner/outrunners I have had measured up to be compatible. I gave it some forethought before sharing. Worth experimenting with I believe, even if one just printed a stand-alone plate for mount tests before printing a complete pump.
Latest blog entry: My You-Tube channel
Feb 06, 2017, 11:44 AM
Platinum Card Member
sundogz's Avatar
Thread OP
Consider that a motor that is slightly oversized to the chamfers in the mount might be difficult to center because it would want to rock one way or the other - even if you tighten the coupler first. Also, using a larger motor would leave a void or pocket behind it allowing the mount plate (which we're trying to keep thin to facilitate thrust bearings) to flex. A solid plate with slots might be the best solution. More surface contact with little flex.
Feb 06, 2017, 12:17 PM
Registered User
On the subject of shaft diameters, I would move the 65mm version to an 8mm shaft, as most of the 56mm motors I've looked at also have 8mm shafts. The Mhz Jet 64 is 9mm, but I think 8 would be fine.
Feb 06, 2017, 02:02 PM
Platinum Card Member
sundogz's Avatar
Thread OP
Quote:
Originally Posted by Firehawk989
On the subject of shaft diameters, I would move the 65mm version to an 8mm shaft, as most of the 56mm motors I've looked at also have 8mm shafts. The Mhz Jet 64 is 9mm, but I think 8 would be fine.
Yeah, I noticed that but I believe the purpose of a large shaft is to appeal to buyers, not because of necessity. Kind of like fishing lures - they are designed to appeal to the fishermen, not necessarily to the fish That size pump is often driven by weedeater engine with it's larger shaft (for various reasons) so they are trying be comparable. When I look at an 8mm shaft and a 64mm impeller, I think overkill. A 64mm prop will have a 1/4 " (6.35mm) hole in it. And often that will be driven by a 1/4" flex shaft! On a motor, they have larger shafts because of heat generated, bad couplers/vibration and a multitude of warranty worries. I'm trying to keep this all scale-able, and I think we are good as it's charted. But if common opinion is for larger shafts/bearings (3mm for 15mm impeller, 4mm for 25mm etc) or change impellers to round numbers (3mm for 20mm, 4mm for 30mm etc.) then now is the time to do it. On the other hand, if a 65mm builder thinks he needs an 8mm shaft, he could easily drill out the bore/bearing pockets for a larger size.

What do you all think - should we increase shaft/bearing sizes by a mm?
Last edited by sundogz; Feb 06, 2017 at 02:33 PM.


Quick Reply
Message:

Thread Tools