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Oct 22, 2019, 12:46 AM
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Originally Posted by sundogz
I had considered a Zen for my 75mm canoe project, but not enough power. It would be powerful enough for a 45 or maybe even a 55mm, but could it run 14-18K Rpm's? Maybe with a gearbox.
Def you'd need a gearbox.
I was running about a 60 to 75mm jetpump with a pocket bike engine of around 50 to 65cc and I should have left the centrifugal clutch in, it had a narrow power band and only had torque to turn the impellor when in power band, i.e. start out of the water, give it heaps, dump it in the water and watch it rocket away!

My 26cc weedeater boat used to turn a home metal cast aluminium impellor about 50mm and medium low pitch, but weedeater motors have less porting for high speed and more low down torque.
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Oct 22, 2019, 10:41 AM
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Quote:
Originally Posted by grael
Hey sundogz,
PushRodSeal.stl attached. Needs vase mode print, no top or bottom layers, print with a 0.5mm nozzle with slicer machine nozzle loaded at 0.6mm. Set minimum layer print time to 10 sec unless you have a fan. Needs ninjaflex or other TPU for the flexibility. If it wobbles too much at the skinny end then let me know and I'll mod it. I haven't trialled it yet but it's similar to a key protector I print for my workmates.
Now that sounds way too complicated. Here's one I just made that resembles a generic seal I have here on my desk. It is already hollow, no special printing instructions necessary, but I would use a brim for adhesion and a .4mm or smaller nozzle
Quote:
I can see the only way I'm going to convince you about the spherical spherical turning nozzle is to finish the design and upload one for you to print!!
I'm afraid that won't convince me, my friend
Quote:
Whoops! I looked at your link and the plain zero backwash "45 nozzle.stl" does look well on the way to what I was talking about.
However I still have some comments
Extending out the steering nozzle only really loads the servo. A simple cup however doesn't appreciably load the servo!
Also, fattening out the outside of the stator end with a sphere like collar allows for more steering angle. That's how I get 34 degrees each side.
I am not the only person who knows better. If you extend the nozzle, it will provide more leverage for turning. And again, I'm not concerned about servo loading (experience). You can provide more steering angle, but that is only beneficial when completely still (think ferry boat). When under way, it is unnecessary.
Last edited by sundogz; Oct 24, 2019 at 04:31 PM. Reason: made pushrod bellows easier to print - V2
Oct 22, 2019, 11:51 AM
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Quote:
Originally Posted by sundogz
Now that sounds way too complicated. Here's one I just made that resembles a generic seal I have here on my desk. It is already hollow, no special printing instructions necessary, but I would use a brim for adhesion. I'm afraid that won't convince me, my friend
Vase mode printing is well worth checking out sundogs. The slicing software does gradual lifting of the nozzle so that you get no seam showing. much better for single perimeter tidy printing. Print that perimeter too thick and the boot will stiffen up and load the servo like your nozzle
That's why I did it as a solid with no hollow(vase mode won't work on your one).

And I'd dispute it being complicated... I've done a few hundred of them trying out my different designs!
Oct 22, 2019, 03:52 PM
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Quote:
Originally Posted by grael
Vase mode printing is well worth checking out sundogs. The slicing software does gradual lifting of the nozzle so that you get no seam showing. much better for single perimeter tidy printing. Print that perimeter too thick and the boot will stiffen up and load the servo like your nozzle
That's why I did it as a solid with no hollow(vase mode won't work on your one).

And I'd dispute it being complicated... I've done a few hundred of them trying out my different designs!
No, I meant your instructions sounded too complicated. It is interesting how you recon that I must not have experienced (something) if I don't see them the same way as you. Truth is I have printed out dozens of vases and rockets and trash receptacles but see no imperative reason to print a boot that way. I would rather keep things simple. I am not one to make things (sound) complicated for the sake of having you think I am smart. I'd rather simplify things to the very edge when possible so more people can benefit from them.

Thank you for giving me reason to revisit this thread, as my push rod bellows was not manifold! and so I have corrected that. Please, let's keep things simple and uncomplicated if possible. It is easy to fool fools - where's the joy in that?!
Oct 23, 2019, 12:25 AM
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Quote:
Originally Posted by sundogz
No, I meant your instructions sounded too complicated. It is interesting how you recon that I must not have experienced (something) if I don't see them the same way as you. Truth is I have printed out dozens of vases and rockets and trash receptacles but see no imperative reason to print a boot that way. I would rather keep things simple. I am not one to make things (sound) complicated for the sake of having you think I am smart. I'd rather simplify things to the very edge when possible so more people can benefit from them.

Thank you for giving me reason to revisit this thread, as my push rod bellows was not manifold! and so I have corrected that. Please, let's keep things simple and uncomplicated if possible. It is easy to fool fools - where's the joy in that?!
I like the KISS principle (K.eep I.t S.imple S.tupid) but I do often struggle to present my thinking in a brief linear fashion. If I'm giving someone instructions at work, and I don't know how much they know about something then I've been caught out before, for example explaining what to solder to someone near my age, then I find out they haven't even mastered the basics of soldering when I go to find out why something doesn't work. 3Dprinting is still pretty new and I really have no idea how many people have changed the default settings on their machines and tackled a vase print! So when I explain about actual nozzle sizes, calculated nozzle sizes, no top and bottom fill etc these are things that can take some people a few cracks at to get right. Maybe they have no bridging fan and print the next layer on still melted plastic etc.

I'm not sure we're yet at the stage of 3D printing general knowledge that skipping these sorts of printing hints is practical? And if it's complicated, not giving them makes it better?

Your pushrod bellows looks good, but the required wall thickness for a practical degree of both strength and flexibility is going to be around 0.4mm to 0.8mm in my opinion. (using ninjaflex as a ballpark for flexibility) Thicker if you are using especially grunty servos for the trivial effort required to turn a well designed steering nozzle
So when you already design the wall thickness, it pays to see how the slicer allocates perimeters as it builds your non vase print through all the layers.

With a vase print, that becomes a non issue, you are using one only, continuous perimeter.
Oct 23, 2019, 09:57 AM
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Grael, did you check the wall thicknesses of my model? The bellows are .28mm (edit: .4mm thick now) and the collars are 1.1mm thick so they won't tear when installed and will be durable in use. Neither did you mention that it needn't have a 'seam' per se, as the slicer program can randomize where the hot ends starts printing each layer (even though the commercial example I copied has a seam on either side and suffers not for it).

And I don't know what to say about publishing a model on Thingiverse before you've actually printed a copy yourself to see how it fares (it 'ought' to print just fine!). I have seen plenty of designs there by artists who (obviously) never printed one themselves - or they would have changed (something).

Lol, no need to continue this conversation, it has little to do with the 3D FJD project. Please print one, give it a try (in a boat) and let me know what you think. But save any suggestions until afterwards. I've had plenty of explaining "why'd you do this that way" as you'll read in the thread, (please read the whole thread as well) and really don't relish rehashing if needn't be. No offense taken or intended, my friend. And good luck with the build.
Last edited by sundogz; Oct 24, 2019 at 04:48 PM. Reason: v2 bellows are .4mm thick now
Oct 24, 2019, 04:44 PM
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I thought I'd practice what I preached and printed out the pushrod bellows I posted earlier. Glad I did, as I needed to make some minor changes (bevels & thickness). Updated the pics and .stl in post 1337 above. Prints nicely now...click on .gif..
Last edited by sundogz; Oct 24, 2019 at 04:49 PM. Reason: added click...
Oct 25, 2019, 12:57 AM
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I think that's the solution for people's jet prints with water seepage too. It wasn't until after I'd messaged you about the wall thickness that it was percolating in my head that my recent last batch of prints were porous and then I remembered, I usually set nozzle thickness to greater than actual diameter and don't have those problems.
I looked it up and as expected, there's more sealing force on previous layers as the filament isn't just tracking, it's being squidgied hard up underneath the nozzle as a greater volume tries to push out sideways as well. Another fantastic benefit, say you are printing with an 0.4 nozzle, but tell your machine you are printing with a 0.6 nozzle, you will print faster due to the higher volume output.
Oct 25, 2019, 07:39 AM
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Quote:
Originally Posted by grael
I think that's the solution for people's jet prints with water seepage too. It wasn't until after I'd messaged you about the wall thickness that it was percolating in my head that my recent last batch of prints were porous and then I remembered, I usually set nozzle thickness to greater than actual diameter and don't have those problems.
Yes, when printing with PLA it can be good to set the printer to think it has a larger nozzle to get more extrusion. TTN mentioned this in an earlier post:

Quote:
Originally Posted by TTN
The biggest thing that affects water tightness (in my experience) is the extrusion ratio and overlapping infill to perimeters enough.
On the inlet housings where there is a high vacuum (or I should say low!) you can feel safe using PETG or ABS. I personally dislike ABS because it's too finicky. But PETG just likes it hotter and that is no problem with most printers today.
Last edited by sundogz; Oct 25, 2019 at 07:41 AM. Reason: added one more note
Oct 27, 2019, 03:07 AM
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Quote:
Originally Posted by sundogz
I thought I'd practice what I preached and printed out the pushrod bellows I posted earlier. Glad I did, as I needed to make some minor changes (bevels & thickness). Updated the pics and .stl in post 1337 above. Prints nicely now...click on .gif..
Nice job Sundogz!
Every now and then when I have time to look here your 3D modeling skills have progressed again.
Those elastomer fillaments open so much possibilities for our hobby! Interesting development.
Nov 03, 2019, 02:31 PM
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Deal on ceramic stator bearings at Boca


From post 53 of the "Cavitation in small jet drives" thread:


Quote:
Originally Posted by Kayaker
I had a front jet bearing get noisy at 40 hours use on my 35mm FJD. Boca has my favorite bearings on sale as a ‘kit’ so I got four for $18 USD, regularly $11 each. These are 5x13x4mm with ceramic balls and 440c SS races. These are specially designed for off-road or excessively dirty driving environments: https://www.bocabearings.com/product...-2ys-nb2-20904
Nov 04, 2019, 12:29 PM
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Jet drive water seals


Here are 5x10x2mm jet drive water seals for the 35mm FJD, $2.55 USD: https://www.metricsealsinc.com/singl...5-x-10-x-2-wao

Here they are in the UK: https://simplybearings.co.uk/shop/p2...duct_info.html

Here are 6x15x4mm jet drive water seals for the 45mm FJD, $4.25 USD: https://www.metricsealsinc.com/singl...-6-x-15-x-4-wa
Nov 05, 2019, 03:27 AM
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Quote:
Originally Posted by Kayaker
Here are 5x10x2mm jet drive water seals for the 35mm FJD, $2.55 USD: https://www.metricsealsinc.com/singl...5-x-10-x-2-wao

Here they are in the UK: https://simplybearings.co.uk/shop/p2...duct_info.html

Here are 6x15x4mm jet drive water seals for the 45mm FJD, $4.25 USD: https://www.metricsealsinc.com/singl...-6-x-15-x-4-wa
Hi Kayaker,
Got some Boca 13mm OD/ 5mm ID SS/Ceramic bearings on order and looking at these:
https://hobbyking.com/en_us/turnigy-...-esc-120a.html
https://hobbyking.com/en_us/turnigy-...ess-motor.html
https://hobbyking.com/en_us/rhino-50...k-w-xt-60.html

Basically just looking at a simple motor combo to try out my 4BDN stator on an FJD intake.
Does this look about right to you?
I had a good sized boat hull to try it on too but last house shift I got a bit aggressive with turfing old stuff

Still, I have a CNC machine I built this year that needs some other tasks as well as kiteboard mould making...
Nov 05, 2019, 10:07 AM
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Kayaker, do you use the hybrid (SS/Ceramic) bearings in the stator? Was wondering how they hold up. I've been using/recommending full ceramic for the stator and sealed stainless up front.
Nov 05, 2019, 04:25 PM
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Quote:
Originally Posted by grael
Hi Kayaker,
Basically just looking at a simple motor combo to try out my 4BDN stator on an FJD intake.
Does this look about right to you?
The motor and ESC are a bit small for a 35mm jet but perfect for a 25mm jet if you are using overlapping impeller blades as they take more power. Keep full throttle to under 6 seconds if you use this in the FJD 35mm jet. I had the 3660, 3000kv motor on 2s running a KMB jet that worked well. I’m running a 4074, 1800kv on 4s and a 120 ESC with the 35mm jet and I have to keep full throttle under 6 seconds. My short little 410mm boat is too fast and out of control past 2 seconds so not a problem.

If the boat your building has a hopping problem a part of the solution is using more than one battery. I look at hopping like it’s a teeter-totter. If you put two big guys on a teeter-totter at the ends of the board and get them to go up and down as fast as they can and then move to the center and do it again you will see a speed difference. Two batteries, one at each end can slow the hopping enough so that trim tabs can stop it with out resorting to a smaller jet drive. Notice that using two batteries instead of one is not changing the center of gravity, fulcrum point of the teeter-totter.

I’m running four, 2s, 2250mAh batteries in series and parallel to get 4s at 4500mAh using the following:

https://hobbyking.com/en_us/xt90-bat...-parallel.html

https://hobbyking.com/en_us/xt90-bat...in-series.html

https://hobbyking.com/en_us/turnigy-...lipo-pack.html

Change battery plugs to fit XT90’s if they get hot from low voltage resistance in static testing. XT90 matches the above harness.


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