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Author Topic: Water Jet Drives & 3D Printing  (Read 43552 times)

IKB

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Re: Water Jet Drives & 3D Printing
« Reply #75 on: April 23, 2016, 08:08:40 AM »

Hi tsenecal,

At work we use Solidworks 2016, I can transfer my licence to my home machine to work in the evenings, so I design everything in that. The pictures I post of the cad models are screen grabs from the program, no Photoshop here.

Alex
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IKB

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Re: Water Jet Drives & 3D Printing
« Reply #76 on: April 24, 2016, 10:37:15 PM »

Hi Guys,

So, many hours in the shedshop last night and this morning later, I completely stripped out the old jet drive unit, which was painful to say the least, at the same time I also investigated the source of the vibrations in the old unit, which is when I found the old impeller had slipped forward on the shaft causing the leading edge of the blades to grind against the inside of the tunnel.
The impellers were originally designed to be grub screwed onto the shaft, but that was quickly discarded as they are such a tight press fit onto the shaft and they have never given any bother, I suspect what has happened, is the impeller has been subjected to speeds and loads it can't withstand during testing and as load increases, the impeller expands to the point where it can walk up the shaft, the stuttering on the last run is the impeller hitting the tunnel, stopping, the shaft then rotates separately to the impeller, the friction this causes heats up the PLA and when PLA gets warm it becomes really sticky, at this point the impeller grips the shaft and drive is restored.
Examining the original tunnel body, which is now the oldest part of the entire build, the walls are relatively thin, or more precisely, the same thickness as a Graupner unit, this allows the rather long impeller shaft to flex in the shaft tube, the new unit addresses this and many other issues.

When I set out to redesign the tunnel housing, I had several points in mind:

  • The unit as a whole had to be rigid
  • Incorporation of an integral motor mount
  • Use a shorter impeller shaft
  • Integral shaft seal in the housing body
  • Use a solid coupling between the motor and impeller shaft
  • Be able to print the unit in one piece on my 3D printer
With these points in mind I had to alter quite a few key aspects about the original design, the biggest of which was that it was just to big to fit into the build envelope of my Lulzbot Mini, which has a build volume of 150 x 152 x 158mm, the original Graupner unit is a relatively long and tall unit, so I lowered everything, included a base plate to tie everything together and knocked around 40mm off the overall length.
Some limitations are placed upon me when designing things to be 3D printed, namely, that they are 3D printed and certain shapes are very problematic to print, this is what lead to the motor mount being a bolt on item, but it turned out not to be a problem, as the entire structure is remarkably rigid. During a break at work I machined up a solid shaft coupling from some scrap Brass stock, this sits nicely between the motor and impeller shaft, which is effectively half the length of the old one at 120mm, the dual bearings in the motor support the drive end nicely, with the other end of the impeller shaft being supported by a Bronzelite top hat bush in the stator housing.

Cooling has always been somewhat of an issue on this project, the passive cooling system worked well, by just didn't provide the throughput necessary to keep the motor cool, my active pumped system was a bit of a flop altogether and best forgotten about, but I am very pleased with the latest system, tapping into the positive pressure inside the stator housing, the harder the jet drive works, the higher the pressure and the more cooling is provided, which is evident in the video as cooling water expelled increases proportionately with speed.
Testing on the lake today:
  • Test run one, to try and keep the balance of the boat, I had decided to use a 2250mah 3S Lipo, which should give ample power for a test run but be much lighter than the 5000mah 3S batteries I normally use. Firstly some harbor maneuvers were carried out to test the steering, reversing and also to check the cooling system was working; with everything appearing to be in order, I sailed out of the harbor and started to apply throttle... when the Lipo alarm went off. So in the boat came and no sooner had I lifted the boat out of the water than the alarm stopped, I suspect that there is something very wrong with this battery, a fresh 5000mah was swapped in for test two.
  • Test run two proved to be very successful indeed, although it was not without incident, the boat suddenly stopped in the middle of the lake, although it did restart again and later examination of the GoPro footage revealed the problem to be loss of pump prime due to rough water, oh and the ESC exploded spraying the inside of the boat with capacitor goo, although it did keep going. Apart from these two minor upsets, everything went to plan, the drive is very smooth and vibration free, the biggest limiting factor in getting the most out of the drive now is the design of the hull, the very basic airboat design I have currently is very easily lifted above the water by bad water, which is really bad for jet drives, but in calm water, this thing really monsters along.
In conclusion:
  • The brushless motor is more powerful than the drive can handle at the top end as above 80% something throttle cavitation of the impeller starts to become an issue
  • I made it through an entire test without being rescued!!!!  :o
  • I need a decent hull and am very tempted to make a twin jet power boat  %%
  • A bigger, water cooled ESC will be installed and if I can get a full run next weekend, I will call this a success and move on to something else, namely progressing my Stolly design, or finishing one of my other boats, might build my Springer!
Video from today: https://youtu.be/1fIXD4WxVa0
Alex
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Captain fizz

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Re: Water Jet Drives & 3D Printing
« Reply #77 on: April 25, 2016, 08:18:43 AM »

That is looking really good.
it sounds much happier too. Real progress. :-))


Simon.
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Re: Water Jet Drives & 3D Printing
« Reply #78 on: April 25, 2016, 01:40:14 PM »

 :} SPRINGER TIME! :}

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derekwarner_decoy

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Re: Water Jet Drives & 3D Printing
« Reply #79 on: April 25, 2016, 03:08:41 PM »

Alex......the design layout certainly appears far more rigid, and from the run sounds, is just that :-))......in the final design, would a metal impellor be a practical option?........... Derek
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IKB

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Re: Water Jet Drives & 3D Printing
« Reply #80 on: April 25, 2016, 03:16:22 PM »

Hi Derek,

Yes, I have been thinking about this for the final V-hull version, I am going to look into the cost of getting a metal one from shapeways, but for the moment, I have just ordered a larger water cooled ESC, so hopefully, I will be able to get some lakeside footage next weekend.

Alex
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IKB

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Re: Water Jet Drives & 3D Printing
« Reply #81 on: May 22, 2016, 12:49:17 AM »

Hi Guys,

Now that the craziness of the last couple of weeks is over, I managed to find some time to repair the jet boat and get back down the lake today for another round of tests, changes this time around are as follows:

  • 1700Kv Outrunner brushless motor, this will limit the maximum RPM to 18870 on 3s, which is well within the 18-20K RPM range for this type of drive
  • New capacitors on the ESC, goo on the inside this time!
  • New homemade water cooling block for ESC
Out on the lake today conditions were not bad, just a bit damp, I was conducting tests in the 2 minute intervals between bouts of some of the heaviest rain I have seen for a while... but the water was really calm and no one else was stupid enough to be at the lake, so I had the place to myself.
Results from today were very mixed:
  • I managed one good run, which ended with the impeller walking up the shaft again
  • The repaired ESC works fine and the water cooling block did an awesome job of keeping the ESC cool
  • The new outrunner is rubbish, the outer casing does not rotate completely concentrically to the shaft, causing vibrations and even with it's inbuilt fan, it ran very hot, but this is what you get for buying cheap Chinese rubbish from eBay.
I am going to go back and look at motor selections again, I like an inrunner design with a water jacket, as jet drives place a lot of strain on a motor and I don't think fan cooled outrunners will be up to the task. Impeller slip has again blighted another day of testing, I am pinning my next impeller to the shaft and hopefully I can then really test the limits of the 3D printed design, this only leaves the last limiting factor and that is the hull design, there is no way around it, if I want to continue development of this drive, I am going to need a proper hull, I have something in mind, so watch this space.
One good thing that came out of today, was I managed to get some lakeside footage of the boat running, it is not the best, as I was trying to sail and film at the same time, but it shows the most successful run of the day, which was between half and three quarter throttle: https://youtu.be/smtkWQN6FW0
On board GoPro footage of same run: https://youtu.be/yl1Pu__KHQQ
Alex
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Re: Water Jet Drives & 3D Printing
« Reply #83 on: May 22, 2016, 10:14:40 AM »

Hi tsenecal,

Thanks for the info, I was looking at the second choice you list last night and will probably use one in the next version, as it is a very resonable price for a motor that includes a long water jacket.

Alex
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IKB

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Re: Water Jet Drives & 3D Printing
« Reply #84 on: May 24, 2016, 01:00:19 PM »

Hi Guys,

Planning the next stage of this project, I am going to address one of the main limitations of the design, that being the lack of a decent hull, I am looking around for a deep vee style into which I plan to drop a twin jet system; so far I have found this on eBay, any other suggestions are gratefully received:

http://www.ebay.co.uk/itm/111999310282?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Alex
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IKB

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Re: Water Jet Drives & 3D Printing
« Reply #85 on: June 06, 2016, 01:04:18 AM »

Hi Guys,

Glorious day down at the lake today, near mill pond conditions out on the water and new improvements to try out, changes this time around:

  • Gone is the appalling out of balance outrunner from China, back is the water cooled 1900Kv inrunner
  • New and improved impeller design with integral Brass UJ coupling instert to grip the shaft
  • Both of my LiPo packs have bitten the dust so I am back on twin NiMh packs, or 27360 RPM at full throttle
So it was clearly evident from the debacle of a test session last time that the impeller keeps shaft walking and this really needs addressing, so I went back to my initial impeller designs, which incorporated a metal coupling onto the 3D printed impeller hub to help with torque transmission between the shaft and impeller body.

Originally I was going to use an Oldham coupling hub, but these are very expensive for what they are and I had a spare UJ Brass insert in the parts bin, so I used that instead; the impeller body was lengthened to incorporate the new coupling, which meant I could also increase the blade length, this gives a slightly shallower angle, but both blades now cover 180 degrees.
Results from the lake:
  • First Run - Batteries too far back, stern dug in and every little wave upset the balance of the boat leading to loss of pump prime... I also managed to clip the outer harbour wall and flipped, leaving me stranded upside down in the entrance to the harbour
  • Second Run - With the trim now sorted things were looking good, until the steering coupling came loose leaving me with ahead or Starboard for directional control
  • Third Run - Having made liberal use of the gremlin mallet, I stormed back and forth across the lake for five minutes, the only note worthy thing to happen was a drop in performance, which was due to drained batteries
Every run I do is recorded by the onboard GoPro camera, this has proved invaluable in diagnosing some of the problems, for instance, towards the end of run three, from the lake side, what appeared to be a drop in performance turned out to be motor surging. Reading into this phenomenon online, this is caused by the ESC making continuous high demands on the batteries, as the voltage drops, the ESC battery protection kicks in and decreases demand, the battery voltage recovers and the ESC makes higher demands once again and so the cycle continues... in short, more LiPos needed.

A very successful day of testing with run three being the longest continuous run to date, going forward from this, I am going to tweek the impeller design slightly, it could do with a bit more clearance in the impeller tunnel, which should cut out the extraneous vibrations that are left; I am also going to explore the feasibility of completely 3D printing a  deep Vee hull.

GoPro footage of test run three, I have shortened it some what, as after the end of this segment, it is really uneventful: https://youtu.be/4TNh3FjTems

Alex
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IKB

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Re: Water Jet Drives & 3D Printing
« Reply #86 on: June 13, 2016, 12:47:55 PM »

Hi Guys,

With good results from the last round of testing behind me, I have finally found a hull that I like and have placed an order, so as soon as it arrives I will start work on a twin jet power boat  :}

Link to the eBay listing for anyone interested: http://www.ebay.co.uk/itm/Fast-Electric-Model-Boat-hull-Zoom-I-fibreglass-moulding-/142008150793?_trksid=p2141725.m3641.l6368

In the mean time, I am going to address the slight rubbing issue of the impeller and try some different motors out to find an optimal setup

Alex
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IKB

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Re: Water Jet Drives & 3D Printing
« Reply #87 on: June 20, 2016, 10:58:35 PM »

Hi Guys,

Exciting news, new hull arrived in the post today, it is very nice, but I fear a twin drive system may be a tad overkill for such a small hull, I honestly thought it was going to be bigger, oh well, a single drive will be pokey enough.  :}

I tried to do a write up of Saturday's testing last night, but as I hit the post button, I was asked to log back in and lost an hour and a halfs work  >>:-( so here is a shortened version.

Modifications this time around are as follows:

  • 3D printed trim tabs on transom with a fixed five degree down angle
  • Turnigy 180A Watt meter in 3D printed waterproof housing on top of deck lid for real time recording of current draw
  • New motor, Turnigy Typhoon 500H Heli Motor 1800kv
  • Back on Lipos again with a fresh set of Turnigy Graphene Professional 4000mAh 3S 15C LiPo Pack w/XT60
  • New impeller
As you all know, I keep coming up against the problems caused by the rudimentary design of the prototype hull, namely any rough water lifts the bow and the drive gulps air causing a loss of pump prime, to combat this I have printed and installed  some fixed angle trim tabs to keep the bow planted; what a difference, even at low speed, the boat sits properly in the water and handles quite rough conditions without any hesitation.
In order to gain a better understanding of brushless motors under load, I installed a Turnigy Watt meter on the deck lid inline with the GoPro, with the intention of being able to read off current draw figures for know throttle settings, this was fine in theory, but glare from the waterproof casing obscured most of the results, however, a lot of useful data was collected.
New impeller, as the old one was quite clearly rubbing on the inside of the impeller tunnel, so a slightly smaller version solved all the problems and several people remarked how quite the boat was on the lake.
Results from the lake:
  • First Run - Good shake down run and some useful data recorded on camera, with the new motor pulling 30A at half throttle, but a scary 100A flat out, which is way above the C rating of the batteries, ESC and double what the motor is rated for continuously. Boat sat well in water and turns much more efficiently.
  • Second Run - This time I went over o the far side of the lake for the calmer water and to stay clear of the yachters, several very flat and fast power runs achieved with the new setup, taking time and distance very crudely from the onboard footage, I estimate that the boatis nudging 30mph flat out. Unfortunately this was not to last very long, after briefly setting off the Lipo level alarm, which then went back off again,  mid way through a turn, the boat died suddenly, in the video the low rumbling noise is not a servo but the motor trying to rotate.
After rescuing the boat and upon finding the motor unable to do anything but vibrate feebly, I swapped in my original 1900Kv inrunner, this performed well, but it is not as efficient as the outrunner at low speeds, the top end current draw was the same, but I suspect that is more to do with limitations imposed by the batteries and ESC, which are both not specced for the kind of numbers I am getting.

Going forward from this, after doing some further reading into brushless motors and brushing up on some of the basics of Ohm's law, I am going to try another motor, but this time on a higher voltage, this will give me the extra watts that the drive needs. Following 6705russell's recent post of a new build Graupner Atlantic Challenger, (http://www.modelboatmayhem.co.uk/forum/index.php/topic,55129.0.html) which uses the same jet units that I have based my design on, I asked him what he was planning to run motor wise and he suggested the following: http://www.overlander.co.uk/motors/brushless-motors/tornado-thumper-v2-4240-10-890kv-brushless-outrunner-rc-motor-latest-model.html
I really like Overlander motors, I am using two in my Model Slipways 1/16th Trent at the moment, so the plan is to run one of these on 6s giving a top end 19758 RPM & 540 Watts.
Video from the lake tests:

First Run - https://youtu.be/gt3CHycXozo
Second Run - https://youtu.be/6tJLQaqKI0I
Lakeside (Half Throttle Cruise) - https://youtu.be/jAkk3XtKe2E

Alex
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derekwarner_decoy

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Re: Water Jet Drives & 3D Printing
« Reply #88 on: June 20, 2016, 11:58:09 PM »

Alex.....it's the same old frustrating story  >>:-(..& probably due to the Internet Server....so.......

When you have a post that occupies more than 1/2 a dozen lines.......create it in Word ...or the like....save/edit...come back after dinner...copy & paste it into the MBM page  O0

People do like reading long & detailed postings on subject matter that appeals......one of the great things when members post detail .....and if we are not sure of the specification we can search on it without closing the page

Keep up the good work :-)) .... Derek
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Re: Water Jet Drives & 3D Printing
« Reply #89 on: June 21, 2016, 07:05:20 AM »

Alex - your links reposted - I was getting the overlander link rather than a youtube one

Video from the lake tests:

First Run - https://youtu.be/gt3CHycXozo
Second Run - https://youtu.be/6tJLQaqKI0I
Lakeside (Half Throttle Cruise) - https://youtu.be/jAkk3XtKe2E

Also consider an alternative (cheap) wattmeter. I use a http://www.4-max.co.uk/wattmeter-budget.htm (recommended by Inertia too1)
I have mine mounted in a semi-waterproof box - the advantage if this one is that the display is 7 segment LED rather LCD
so should give better visibilty on your vids.

Richard
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IKB

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Re: Water Jet Drives & 3D Printing
« Reply #90 on: June 21, 2016, 10:43:58 AM »

Hi Richard,

Thanks for that, I normally cut and paste web page links into the body of the text, but for some reason last night, everything after the Overlander link became part of the same link, I thought I had separated the text from the link, but it was obviously just the formatting I had corrected

Alex
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Re: Water Jet Drives & 3D Printing
« Reply #91 on: June 21, 2016, 11:10:23 AM »

Been there, Done That !

Richard
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IKB

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Re: Water Jet Drives & 3D Printing
« Reply #92 on: June 26, 2016, 07:29:07 PM »

Hi Guys,


Ok, let's just say things could of gone better today, several new parts bought and fitted and I went to the lake with high hopes of finally cracking the battery / ESC / Motor combo issue, that is stopping me from progressing this build much further.


Modifications this time around are as follows:


  • New motor, this time an Overlander Tornado Thumper V2 4240/10 890KV - Brushless Outrunner
  • New Lipo pack, Turnigy 5000mAh 6s 30C
  • New LED Watt meter, which I hoped would be clearly visible on GoPro footage
  • New 3D printed housing for above
The new Watt meter has an 7 segment LED, 4 digit display, which is nice and bright, I designed and printed a new housing for it and dutifully installed it onto the boat lid, what I failed to realise is that, LED displays are not constantly on, they are just displaying information very quickly and the persistence of vision phenomenon, which makes all motion pictures possible, makes the rapidly changing display as constantly on, without flickering. For a sequence of images to appear fluid in motion, anything above 25fps will fool the eye, however, a digital camera records the outside world at a given rate, one frame at a time, if it is not in sync with the LED display, then it will capture the numbers being displayed at any point during the, "Off, turn on to display for a set period, turn off for next refresh loop" cycle, which makes the film of the display dim, jumpy and very hard to make out, not helped by my recording at 25fps, where a higher frame rate would elevate some of the issue.
One thing this Watt meter does is display peak figures from the run and as suspected, it peaked out at 99.9A, in other words, I need to put the Turnigy meter back on as this one is not rated for the job it turns out.


Results from the lake:


  • First Run - I did manage a shake down run, only up to half throttle to check everything out, unfortunately my GoPro cut out after 4 seconds, I think I have a sticky button on the water proof case. The Watt meter returned with a peak current figure of around 30A.
  • Second Run - Conditions were flat calm today and I was expecting big things, but the ESC was having none of it and let go in spectacular fashion nearly burning the boat down
Upon repeated viewing of the onboard GoPro footage, you are just able to make out what the Watt meter reading is and my theory as to what happened is this:


  • With each increase in throttle, current draw spikes sharply and then falls back to a steady level
  • After completing the turn on film, I went from 1/3 throttle to 100% in one go, which caused a massive spike in load
  • New batteries are capable of delivering ESC melting levels of current at 200A plus and I think this is exactly what happened
  • ESC broke down internally, stopped delivering power to the motor but kept drawing current, causing catastrophic failure from within
The ESC is not a problem, to be fair, I am surprised it has kept going as long as it did, I have a new 120A water cooled ESC on the shelf and ready to go, I will definitely be programming it with the softest acceleration rate I can. The biggest issue I have at the moment is the boat itself, having a small fire in a confined, sealed space means that everything is covered in an acrid smelling coating of burnt electronics, I just cannot put into words ho much this stinks, I am very tempted to throw the boat away and start again, but we shall see.


Videos from lake testing:


Alex
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Re: Water Jet Drives & 3D Printing
« Reply #93 on: June 29, 2016, 12:51:44 PM »

Hi Guys,

Looking into the ESC fiasco, I have discovered that I may have been a bit of a clot, after discovering what I thought was a 90A ESC, is actually an 80A and looking at the specs on HobbyKing's website, the burst current is only 100A with a continuous rating of 80A, no wonder it went south  {:-{
But not to worry, I have a HK 120A water cooled ESC on the shelf and that has a burst rating of 150A, Turnigy also do a 120A ESC with a burst rating of 750A!!  %%

So the plan is to gut the current hull, give it a really good wash, as it is stinking out the shedshop currently, then rip out the current jet unit and replace with a revised version:

  • Improved shaft seal arrangement
  • Improved motor mount system which will allow for easy and quick changing of motors lakeside
  • Minor changes to impeller tunnel to try and eliminate water ingress
To help with all of these mods, I am currently constructing an enclosure for my 3D printer to make it quiet enough to print overnight, which will speed up things enormously, separate post on this shortly.

Alex
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Re: Water Jet Drives & 3D Printing
« Reply #94 on: July 05, 2016, 10:44:04 PM »

Hi Guys,


Progress on the rebuild today, I have stripped out the charred remains of the old ESC and took the hull into work to introduce the hull to the table saw. No, don't worry, I'm not binning the prototype just yet, as it is on it's second drive unit tunnel already, the bottom of the hull has been chopped and repaired quite extensively already and the easiest way to fit a new tunnel in is to chop out the back half of the hull and graft a new one back in.


I am planning to get back on the lake with the new version this weekend, so watch this space for more updates to come, I am also making good progress on the 3D printer enclosure, separate post to follow soon.


Alex
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Re: Water Jet Drives & 3D Printing
« Reply #95 on: July 11, 2016, 12:06:08 AM »

Hi Guys,


Well I may of not quite made it to the lake this weekend, but I have rebuilt the jet boat prototype and even staying in the shedshop, things have been eventful.


Changes made during rebuild:


The new impeller tunnel is slightly redesigned, this time I have incorporated captive nuts in the base which allow the entire motor mount to be removed with the motor attached, allowing another to be swapped in quickly and easily, this will greatly aid the motor comparison work that I am wanting to complete, it was possible to do a motor change lakeside, but it was a long and fiddly process with little to no access to the bolts, each test motor also has a shiny new redesigned mounting bracket, so it is almost plug and play.
Another problem I am also trying to address is my long running battle with water ingress into the hull, I think this is down to the old design, where the tunnel just clamped to the transom, the tunnel was bonded to the inner transom surface, but any cracks would lead to pressurised jet water escaping into the hull. This time however, the inlet grate is a bonded integral piece and the outlet is stepped to allow the body of the impeller tunnel to carry through the transom, so any leakage will occur outside the hull, in theory.
The old seemingly indestructible 1900Kv inrunner I have been using is great, but I would like to test a motor on 3s which doesn't over speed the jet drive, which means a step down from 1900-1700Kv in the form of Turnigy's Aquastar 1700Kv...


Pah! "Aquastar" my a**! How can a motor that blows smoke on the work bench be an Aquastar?  >>:-(  I tell you, I got it all setup in the freshly rebuilt hull and was doing a systems test after programming the new ESC and poof, just after touching 100% throttle, smoke out the back of the motor.
It doesn't help that the HobbyKing instructions for setting up their ESC are all in badly translated Chinese and even after reading them several times, the grammar is so bad, some details are unclear to say the least.


So next weekend I will be back down the lake for more tests, this time I will take the Overlander outrunner and the old standby 1900Kv inrunner, I may also upgrade to a Turnigy 120A ESC, as I have used their ESCs with no trouble in the past and I am not convinced the HK one is doing what it should do.


Alex
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IKB

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Re: Water Jet Drives & 3D Printing
« Reply #96 on: July 18, 2016, 12:13:36 AM »

Hi Guys,


Well, made it down the lake today and conditions were a bit choppy for testing, but I threw it in anyway and watching the GoPro footage back, the boat took a real hammering traversing the lake, so much so, that on the second run I nearly shook the reversing bucket off.


Mixed bag of results from the runs today:


  • First Run - Running old 1900KV inrunner on 3s, new 120A ESC and Turnigy 180A Watt Meter, thing were going well until the motor mounting bolts shook loose allowing the impeller to move and rub against the tunnel wall.
  • Second Run - Running Outlander outrunner on 6s, rest the same, things went very well, drive responds very well to the torque this outrunner can lay down... it then went pear shaped, when the smoke escaped from the motor.  <:(
The first run was quite encouraging, except for the rough conditions, which meant full power runs were all but impossible, the sun was so bright today I couldn't read anything from the watt meter at all, this has to be the most disappointing part of the testing today.
But i is not all bad news, the new ESC survived and although quite warm to the touch, it was by no means worryingly hot, what was worrying however, was the amount of water ingress into the hull again, I am going to have to get to the bottom of this once and for all, which will probably mean testing in the bath to see where the water is coming in.


The second run started well and below three quarter throttle, the outrunner performs really well, until full throttle, when there was an almighty scream from the motor and a loss of drive, but as quickly as it stopped, upon re-application of throttle it was off again like nothing had happened... until it did it again and then nothing, had to be rescued.
Watching the GoPro footage back, after the first loss of drive, white smoke can be seen inside the hull and then the second time much more smoke, it is clear that something has gone horribly wrong and by the smell of the motor and the yellow / orange discolouration of the motor mounting, I would surmise that I've managed to pull too many amps through another motor, the smell being from the winding insulation which has simply melted away.


So more work to do, I will post GoPro footage tomorrow.


Alex
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Re: Water Jet Drives & 3D Printing
« Reply #97 on: July 20, 2016, 07:54:05 PM »

Hi Guys,


Apologies for the delay, had some trouble encoding the video for YouTube:


Alex
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Re: Water Jet Drives & 3D Printing
« Reply #98 on: July 21, 2016, 11:12:09 PM »

Hi Guys,


News from the Shedshop, have been playing around with how to get a legible recording from the watt meter and the Turnigy one is proving to be a royal pain in the ass, which go me thinking about the LED one I have, what if I increased the frame rate of the recording? Would this resolve the flickering issue I am having?


My GoPro Hero 2 will record @ 720 60fps and as you can see from the screen grab, the readout is perfectly readable, so will swap back to this one for the time being.


Alex
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Re: Water Jet Drives & 3D Printing
« Reply #99 on: July 21, 2016, 11:40:41 PM »

Really impressed with this thread and been following with interest. I have a couple of NIB graupner water jets for a future project when I retire......
When you're going at high speed and the scream comes, could it be the duct goes suddenly dry causing the impeller/motor  to become unloaded and spin at higher revs, slowing down allows it to refill and then drive correctly again?

If the hull you're experimenting with is flat bottomed, could this be the problem? Even a shallow ve hull would put the intake below the water level and lessen the chance of the duct running dry.
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