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Nov 15, 2019, 04:16 PM
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chimera head 3D print.


Finally got my head upgrade to chimera on my 3D printer and tuned in last night so it's time to experiment....
The attachment is sliced with Prussa slice3r, I can set the extruder for individual parts, also for perimeters, fill and support material. there's a purge volume that will cause some colour bleed but I'm still keen to see how this slicing will turn out, one of each colour and two with separated perimeter/fill colours. My filaments are loaded to the display colours.
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Dec 28, 2019, 03:16 PM
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Kayaker's Avatar
I am testing stator blade shapes to see what differences there might be. In static testing of motor amp draw, stator water pressure and jet thrust using the 4BDN and FJD 23.5mm stators the numbers are very close. I tried 40X83mm and 40X92mm motors, 120 and 180 amp ESC’s, 39mm and 46.5mm pitch steel impellers. The 83mm motor used 2160 watts and the 92mm used 2997 watts. Best thrust was 19 pounds/ 8.6kg with this 35mm jet drive. Very little difference between stators at this point.

The only clear pattern that emerged is 4400mAh batteries are not enough to feed these motors with a 35mm jet drive at full throttle for more than 5 seconds (old batteries, 2 seconds) before voltage sag and LVC. Nothing to do with stators of course other than they both have a lot of water compression so produce high amp draws.

The FJD stator is quieter running with the angled blades. When I moved the impeller away from the 4BDN stator blades a little it ran almost as quiet as the FJD. This stator uses Grael’s first blade shape that would be noisier but stronger than his second blade shape.

I really like Grael’s steering system. It turns very smooth around the center getting more progressive at full turn. A small servo can be used because it takes very little effort to move. This short nozzle puts thrust closer to the transom so may reduce hopping (shorter lever). My little 410mm boat wants to spin out a little more with this nozzle/stator. I think the stator blades coming out so far in Grael’s first design is squeezing water against the nozzle shooting downward in a turn lifting the stern to spin out. This may be fixed in his second design with the cone reducing the blade length.

There is a difference in how the water exits the stators. I have both stators cut off the same and they have no nozzles. The 4BDN straightens the water more. You can see a difference in the amount of turbulence in the photos. I used the 11 blade 4BDN stator for the photo on the left because the 7 blade is being cut up for the next part of testing. They squirt water about the same. The FJD is on the right and is more turbulent. This could effect steering and other things that can only be seen on open water. Now I’m starting to use these stators with my three dimensional thrust steering on the river. This part of testing is the fun part.
Last edited by Kayaker; Dec 28, 2019 at 03:22 PM.
Dec 28, 2019, 03:51 PM
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Quote:
Originally Posted by Kayaker
Very little difference between stators at this point.

The only clear pattern that emerged is 4400mAh batteries are not enough to feed these motors with a 35mm jet drive at full throttle for more than 5 seconds (old batteries, 2 seconds) before voltage sag and LVC. Nothing to do with stators of course other than they both have a lot of water compression so produce high amp draws.
Kayaker,
Fantastic to get some feedback!
What C rating are your 4.4 amp hour batteries? I've had my 5 amp hour 3 cells arrive about a week ago and I got them in 50C so they should be good up to 250 amps, might be the C rating that you need to look at. Makes a massive difference from past experience.
Quote:
The FJD stator is quieter running with the angled blades. When I moved the impeller away from the 4BDN stator blades a little it ran almost as quiet as the FJD. This stator uses Graelís first blade shape that would be noisier but stronger than his second blade shape.

I really like Graelís steering system. It turns very smooth around the center getting more progressive at full turn. A small servo can be used because it takes very little effort to move. This short nozzle puts thrust closer to the transom so may reduce hopping (shorter lever). My little 410mm boat wants to spin out a little more with this nozzle/stator. I think the stator blades coming out so far in Graelís first design is squeezing water against the nozzle shooting downward in a turn lifting the stern to spin out. This may be fixed in his second design with the cone reducing the blade length.
The better fix is to cut out the NW and NE parts of the end of the stator to give some upward escape ability for the flow under hard steering. This will correct the flow direction. Great to hear the spherical nozzles are working as planned With your other 3D nozzle, I'd be looking at a more advanced radio to give a bit of upward nozzle direction mixing at high steering angles, love your experiment there but I'm starting with small steps on my stator variant.
Quote:
There is a difference in how the water exits the stators. I have both stators cut off the same and they have no nozzles. The 4BDN straightens the water more. You can see a difference in the amount of turbulence in the photos. I used the 11 blade 4BDN stator for the photo on the left because the 7 blade is being cut up for the next part of testing. They squirt water about the same. The FJD is on the right and is more turbulent. This could effect steering and other things that can only be seen on open water. Now Iím starting to use these stators with my three dimensional thrust steering on the river. This part of testing is the fun part.
That difference in exit streams is massive, I wasn't expecting it. There's two likely contributors to it though:
1. The FJD fixed pitch stator blades are working against the inner flow so water moving closer to the hub will be moving a LOT slower, likely this is causing post-exit turbulence.
2. Sundogz thick stator exit vane profile is splitting the 4 x streams of water. Easier to 3D print but aesthetically speaking I like the look of the single stream exit much better. I'm a little confused though, I thought I'd seen some FJD video before with a single exit stream? Or is this because the FJD steering nozzle is re-combining the flow together just long enough to merge the turbulence?

I'll be more motivated to do some more stator design tweaks once I've got a boat up and running, sounds like the C rating on your batteries is holding you back from testing the smaller nozzle outlets?
Dec 28, 2019, 04:15 PM
Jetdrives R Us
sundogz's Avatar
Yes the FJD is meant to be used in conjunction with a steering nozzle which helps direct the flow, but if the straight end of the stator has been cut off, that could be a factor as well.
Dec 28, 2019, 08:41 PM
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Kayaker's Avatar
I ran the 40x83mm 2100kv TP motor on 4s, 8.8Ah, 60c, Zippy, that are 6 months old. For the tests I added flotation for the batteries. I can only fit 4.4Ah in the boat or it sinks on open water. I can’t run the motor at full throttle long enough to do the tests with only 4.4Ah batts.

The 40x92mm 930kv Leopard motor ran on 9s, 4.4Ah, 65c Graphene, 2 years old, used a lot and getting week. I only got a couple of seconds to finish each test before LVC.

I use an air transmitter on Elivon mix for the three dimensional thrust nozzles. I’ve been using this type of nozzle for hundreds of hours and finely designed my own for this boat. I’m using a 26mm FJD stator with my 23mm compression nozzle in the videos that I did and this gives less turbulence.

For the stator tests and photo I cut off the 4BDN nozzle section that has a flare built in for the nozzle. Now it matches the way the end of the FJD stator is.
Last edited by Kayaker; Dec 28, 2019 at 09:34 PM.
Dec 28, 2019, 09:19 PM
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Quote:
Originally Posted by Kayaker
I ran the 40x83mm 2100kv TP motor on 4s, 8.8Ah, 60c, Zippy, that are 6 months old. For the tests I added flotation for the batteries. I can only fit 4.4Ah in the boat or it sinks on open water. I can’t run the motor at full throttle long enough to do the tests with only 4.4Ah batts.

The 40x92mm 930kv Leopard motor ran on 9s, 4.4Ah, 65c Graphene, 2 years old and getting week. I only got a couple of seconds to finish each test before LVC.

I use an air transmitter on Elivon mix for the three dimensional thrust nozzles. I’ve been using this type of nozzle for hundreds of hours and finely designed my own for this boat. I’m using a 26mm FJD stator with my 23mm compression nozzle in the videos that I did and this gives less turbulence.

For the stator tests and photo I cut off the 4BDN nozzle section that has a flare built in for the nozzle. Now it matches the way the end of the FJD stator is.
That's disappointing to hear your batteries are on the way out
I've added a picture of the area you've mentioned that you cut off.
Inside the yellow highlighted areas, this is side relief for extreme steering. If you set up for full throw of the spherical nozzle then there won't be any front wash and as the nozzle shuts off one side, more flow will escape via the side relief.
It's important not to sand the abrupt edges of this side relief rounded, it's intended to discourage coanda flow (water clinging to curved surfaces) Else the water will prematurely split from the straight exit flow.
If you shorten the end then you will loose the full design steering capability.

In my second picture, this is approximately marking out the areas to modify for a limited down-thrust component under high steering.
As the nozzle rotates to either side, the top part of the nozzle opens up the top corner ports and because the side of the nozzle that is closing is partially blocking off flow and part of this will escape upwards out of the new ports to reduce stern-hopping. You can increase this effect by shaping the nozzle outlet like a U, i.e. curved underneath and open at the corners. Remember though, keep sharp edges at the port transitions to avoid predisposing the water to follow the deviation without nozzle control.
Jan 04, 2020, 08:18 PM
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I stopped logging on here due to the controlling nature of an individual....and someone pointed me in the direction of this thread....fantastic thread and waited for two years for someone to challenge R.Sole…..hey,and he cant go removing my threads or weeping to a moderator...of course,I cannot reveal his true identity... loving it.
Jan 05, 2020, 04:36 AM
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Quote:
Originally Posted by Oyley
I stopped logging on here due to the controlling nature of an individual....and someone pointed me in the direction of this thread....fantastic thread and waited for two years for someone to challenge
Quote:
Ö..hey,and he cant go removing my threads or weeping to a moderator...of course,I cannot reveal his true identity... loving it.
You're definitely not alone on here in dealing with that but none of us need to be keyboard warriors on here, it's more fun to share each others failures and successes and to grow from the combined community experience.
It's usually females that resort to dirty tactics in debate. I've been diverted from my logic on occasion by a wet snatch but in this case
Jan 06, 2020, 01:27 AM
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A bit of excitement here this afternoon after work,
My flex connector finally arrived, 5mm inside diameter and I had to enlarge the cavity to get the outside to fit.
Grabbed my AC/DC clip on ammeter and stuck it on one of the battery conductors and taped the Shapeways printed 4BDN 7 vane outlet to the stator, 2/3 filled the bath
I definitely needed more hands to hold the ammeter, camera etc but got the freshly charged Rhino 5A/Hr 50C battery down to 3.78 volts per cell after a good long time of testing.
First... the steering nozzle. I couldn't see it jetting directly like kayakers because this was a freehand test. However, it moves very freely under no power, flutters marginally under very low power and holds lightly into place in any arbitrary position under power, this because of the 8mm pivots.

Next... So I could only get drive from about 25 deg from horizontal max, that was with part of the motor under water. After measuring full throttle current at around 67 amps I fragmented the first plastic impeller when the stator pushed out of the tape and split from the housing Anyway, spare one went on and I carried on getting a feel for the thrust which really surprised me, wasn't able to make any measurements but it was very obvious that any planing boat around a meter length is going to be rocketing around with this drive.
I switched nozzles to my smallest size (2mm more axial closure to the cup end) and retested. By now the battery was down a bit and the current pre-nozzle_change was sitting in the high 50s
First impression was that I was getting substantially more movement of water around the bath so I checked the current and it was up just over 70 amps.
So I'm thinking that there is still good efficiency with the smaller nozzle outlet and that the 4BDN 7 blade stator is definitely showing promise for use with smaller nozzles and expected higher top speeds.
The 150 amp speed controller always stayed cool to touch, so did the sleeved motor though it did get more water cooling than planned The only thing that ever warmed up was the motor leads on extended full throttle runs. I'm thinking that spiral wrapping cooling tube spare length to the motor connectors would be a good idea.

So.. I need a boat!
Plan is to carry on tweaking this onehttps://www.rcgroups.com/forums/show...3031-4BDN-hull and this week I'll order some high density 2-part foam.
I'm way overdue for actually doing something with the CNC router I originally built for routing my kiteboard designs so that's the plan... route the model, fair, shine it up, spray with polyurethane release, clad with thixotropic polyurethane mould material, cure and then do a resin infusion composite hull in the mould. My holidays coming up on 20'th January

Another note for 3D printing and print porosity issues: I found out on the weekend that my prints were not following my set nozzle width percentages when I was looking in a Gcode file for the estimated print time. Despite the Slic3R and PrussaSlicer pop-up info indicating the setting is for the simulated nozzle thickness it's actually basing the track width on the percentage of the layer height instead So this ended up being documented somewhere on line and I've now adjusted my extrusion widths all to manual settings. Apparently a lot of other slicers do this too so whether you are slicing yourself or getting it done at a print shop, good idea to check the gcode file for actual extrusion width settings which should always be greater than the nozzle width if you are trying to seal a print.
Jan 06, 2020, 04:30 PM
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Kayaker's Avatar
What voltage and kv motor are you trying? At 70 amps you must be using higher voltage than my 4s.

I got 146 amps with a 40x83mm 2100kv motor, 120 amp Turnigy Marine ESC (200 amps with 180 amp ESC), 39mm pitch steel impeller, 4s 8.8Ah 60c batteries, 7 blade 23mm 4BDN stator (old style) with 22mm nozzle. 2100Kv X 14.8 volts= 31,080 RPM using 2160 watts. 15 psi water pressure in the stator. 19 pounds/8.62 kg of thrust. This seems like a bit too much squeeze (22mm nozzle) for 31k RPM so I’ll go up to 24mm and retest.

Shapeways is printing the latest 4BDN 7 blade stator chopped up to fit my 3D steering for extensive on the water testing. The rainy season is just starting here.

The overlapping impeller blades make so much thrust in the FJD pumps that I think my 45mm FJD in a one meter boat could pull a 60 pound water skier on two skis. I would love to get a video of that. It would be a good reason to put a GoPro on an RC jet boat.
Last edited by Kayaker; Jan 06, 2020 at 04:36 PM.
Jan 07, 2020, 12:43 AM
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Quote:
Originally Posted by Kayaker
What voltage and kv motor are you trying? At 70 amps you must be using higher voltage than my 4s.
I'm using a 1700KV motor on 3S. It's only around 70 amps when the battery is super fresh at 4.2V per cell, or later when it's down to 3.8 per cell and I use the smallest orifice nozzle to load up the motor more.

Quote:
I got 146 amps with a 40x83mm 2100kv motor, 120 amp Turnigy Marine ESC (200 amps with 180 amp ESC), 39mm pitch steel impeller, 4s 8.8Ah 60c batteries, 7 blade 23mm 4BDN stator (old style) with 22mm nozzle. 2100Kv X 14.8 volts= 31,080 RPM using 2160 watts. 15 psi water pressure in the stator. 19 pounds/8.62 kg of thrust. This seems like a bit too much squeeze (22mm nozzle) for 31k RPM so Iíll go up to 24mm and retest.
Not sure I understand your drawn current vs the ESC rating? I'm using a clip-on DC ammeter.

Good to hear about your rainy season. Always nice to see new waterways spring up to explore!


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