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Author Topic: Water Jet Drives & 3D Printing  (Read 41023 times)

Martin [Admin]

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Re: Water Jet Drives & 3D Printing
« Reply #175 on: August 26, 2017, 02:09:26 PM »


Could you set up the Tx or ESC to give, say, a one second pause between forward and reverse to allow the bucket to move?
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Re: Water Jet Drives & 3D Printing
« Reply #176 on: August 26, 2017, 03:07:21 PM »

Hi Martin,


I'm sure it is possible with a modern computerised TX, but not with my old school F14, plus, who wouldn't want working hydraulics on their boat?  O0


Alex
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Re: Water Jet Drives & 3D Printing
« Reply #177 on: August 26, 2017, 04:12:46 PM »

Oil try it if it works . . . :P

Richard
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Re: Water Jet Drives & 3D Printing
« Reply #178 on: August 26, 2017, 04:58:14 PM »

Groan, yes Richard, very drole  :((
Planning to have new sysetm installed and tedt next club sunday, how's the race prep of your 500 going?


Alex
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Re: Water Jet Drives & 3D Printing
« Reply #179 on: August 26, 2017, 05:18:03 PM »

It was either that or Oil get me coat!

Don't want to divert/hijack your thread so will PM you

Richard
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Martin [Admin]

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Re: Water Jet Drives & 3D Printing
« Reply #180 on: August 26, 2017, 06:55:18 PM »


I had a Lego technic set with hydraulics, there weren't very efficient.... what about cycle hydraulic brakes .... or are they way too expensive?

.... medical syringes?!
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Re: Water Jet Drives & 3D Printing
« Reply #181 on: August 26, 2017, 07:06:32 PM »

Wheelspin models have a set of shocks (spring and oil filled), think about £15 a pair. Got to be better than Lego methinks?


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Re: Water Jet Drives & 3D Printing
« Reply #182 on: August 26, 2017, 07:24:13 PM »

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Re: Water Jet Drives & 3D Printing
« Reply #184 on: August 26, 2017, 08:37:32 PM »

Hi Guys,


Answers below:


  • Martin - Bike hydraulics are really expensive and designed for a very specific purpose,s o very hard to adapt, but nice idea
  • Stewart - The shocks may be worth looking at as they are essentially miniature rams, but for the time being I am going to try and find an off the shelf solution with builtin ports
  • Grendel - I have seen some very similat to this and they may well be purchased in future for another prototype, I am keen to see if the Lego ones can be adapted as they are the perfect size for my application
Alex
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Re: Water Jet Drives & 3D Printing
« Reply #185 on: August 26, 2017, 10:20:23 PM »

http://www.nzmeccano.com/image-116933
how about the meccano hydraulics on their new John deer excavator, these have water as an operating medium.
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Re: Water Jet Drives & 3D Printing
« Reply #186 on: August 26, 2017, 10:25:19 PM »

Hi Grendel,


That is essentially the idea I am going for, except a servo will be doing the job of actuating the cylinders


Alex
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Re: Water Jet Drives & 3D Printing
« Reply #187 on: October 20, 2017, 06:41:10 PM »

Hi Guys,


Quick update to explain my recent absence, well work basically, well that and with BMBS having built a storming rock crawling track recently, I have kind of got caught up in all the excitement of new things to do, plus as I type I am on site in Riyadh for 3 weeks for work, but fear not, the jet boat will return, I am currently trying to iron out the kinks from the latest reversing mechanism and then there will be updates.


Alex
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Re: Water Jet Drives & 3D Printing
« Reply #188 on: March 11, 2018, 12:53:45 PM »

Hi Alex,

From your experience would you say PLA impellers work OK?
I've recently been playing with a variation on a jet drive to fit a few boats my Son wants to build and although the drives themselves seem absolutely solid I guess I'm just not sold on the idea of a printed impeller.

All the best,

Alex (Another one)
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Re: Water Jet Drives & 3D Printing
« Reply #189 on: March 12, 2018, 10:38:32 AM »

Hi Alex,


I have had no issues using PLA printed impellers, once I had resolved how to pin it to the shaft properly, my current iteration runs approximately 2.6 hp, they also stand up well to all sorts of ingestion damage as well as still performing well after a coupling slip and grinding on the inside of the tunnel.


Would love to see photos of your projects, post them on here or PM me if you prefer


Alex 
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Re: Water Jet Drives & 3D Printing
« Reply #190 on: March 13, 2018, 11:17:16 PM »

Hi Guys,


Quick update, finally got around to making some progress on the jet drive, indirect progress, but progress none the least, with my decision to have pneumatic reverse, I am in need of an onboard air supply, so I have cobbled this together from the motor gearbox from an FTX Outback crawler, a Technic pump and some 3D printed parts to hold everything together


Quick video of the bench test, this is running on 3v and is much quicker on 5v, but needs bolting down: https://youtu.be/JcuTWPhYsiE


Alex
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Re: Water Jet Drives & 3D Printing
« Reply #191 on: March 13, 2018, 11:28:03 PM »

What about the air retracts the plane boys use???  Come in different sizes and combined with your compressor they have a long travel as well


Mark
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Re: Water Jet Drives & 3D Printing
« Reply #192 on: March 29, 2018, 12:51:05 PM »

Hi Mark,


Thanks for your reply, I have looked into various commercially available ram systems before and the aircraft stuff is good, although a bit pricey, all of the units I have seen out there all have the same issue, and that is they are of a stroke length that is not suitable for my application.


The other side to the route I am taking is, I really enjoy the challenge of creating my own bespoke solutions from relatively inexpensive parts, usually using them in ways they were never designed to be in the first place, it is the journey of discovery that is enjoyable... or you could say I'm a penny pinching, stubborn, masochist, either  way, I'm enjoying my tinkering time in the ShedShop!  :-))


Alex
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Re: Water Jet Drives & 3D Printing
« Reply #193 on: May 02, 2018, 12:07:37 AM »

Hi Guys,


Busy working on the jet boat ready for next weekend, this time around I should have pneumatic reverse, a heavily re-worked reversing nozzle and a new drivetrain using a 5065 270Kv Outrunner more commonly found in electric skateboards, this will be running through a 3:1 gearbox to give approximately 19500 RPM, but hopefully give a big reduction in current draw for more fun time on the lake


Alex
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Re: Water Jet Drives & 3D Printing
« Reply #194 on: May 02, 2018, 08:41:17 AM »

HI Alex, that looks superb, can't wait to see it in action,


Mark
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Re: Water Jet Drives & 3D Printing
« Reply #195 on: May 05, 2018, 03:47:31 PM »

Hi Guys,


Update from the ShedShop, been very busy and we are ready for testing tomorrow!  :-))


  • New steering setup using 3mm rod & proper rose joint ends, this has always been a real weak point of the unit, but no more, this is rock solid - https://youtu.be/UlGOr_pW_sU
  • Updated reversing mechanism with pneumatic actuation, the rams do work, but I haven't had chance to design and build an RC valve to control the setup - https://youtu.be/_Mk7_Z1FOAQ
  • New Outrunner installed and ready to go, not got the new Vesc setup yet, so will test on old ESC and see how we get on, bench test seem good though


Alex
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Re: Water Jet Drives & 3D Printing
« Reply #196 on: May 23, 2018, 05:23:49 PM »

Hey Guys,


Life just seems to be getting more and more hectic these days, but that's what happens when you have family functions to attend and get engaged  %%  so here is how testing went from 06/05/18:


First Run
  • Shake down shore run, motor stuttering at high throttle input
  • No Amp readings due to me not selecting correct mode on Watt meter
  • Low power cruise on open water, new reversing nozzle design is very responsive to change of heading input with new central upright
  • RX lost power for a short while for some reason, but soon recovered
Second Run
  • ESC timing adjusted to try and solve stuttering at full power
  • Short half throttle run achieved with a current draw of 16.5A
  • Very brief full power run achieved with a current draw of 62A
Third Run
  • Same cutting out issue on open water
  • Shore static power pull cut short due to grubscrew coming loose on output gear of gearbox
Fourth Run
  • At this point convinced ESC BEC was at fault, so cut power line to RX from EAS & used separate battery pack
  • Open water cutting out issue persisting
  • Longest full power run on open water with this setup, GoPro footage shows no tendency to roll like last setup, very stable
So this testing session was a mixture of some good and some annoying issues:
  • Motor Stutter - I did have my reservations about the old Turnigy ESC turning such a large outrunner properly and that may be where some of the stuttering at high power were coming from, I did notice better high throttle performance after reducing the timing in the ESC setup, on the next outing I am planning on having the VESC installed which is designed for such motors and can make full use of the in built hall sensors this motor has
  • 3D Printed Spur Gear Hub - The centre of the large 50T 1.0 MOD spur gear attached to the motor shaft is from an RC car, which is designed to have a clutch bolted to the centre of it, my outrunner has an 8mm OD shaft, so something was need to fill the hole and after several attempts, I finally managed to 3D print a hub adapter which bolts into the gear and picks up on one half of an Oldham style coupling, which handles the torque transmission, this is one success I was not anticipating, but am happy to take
  • Full Power Stability - I am not sure which aspect or combination of design changes has resolved the tendency of the prototype to roll at full power, but this is another win, very stable and precise control at all power levels, I am sure the new and improved steering linkage setup has a part to play in this, I just don't know how big a part
  • RX Loss - This is a really strange one, when doing static shore power pulls, I never once lost radio signal, but every time the prototype went out onto open water, it would just cut out, sit there for a bit and then reluctantly come back to life, at first I thought this was due to a fault with the ESC BEC being caused in some way by an incompatibility with the Outrunner, hence why on the last run I used a separate RX battery pack, this however did not resolve the issue and it wasn't until I was watching back the GoPro footage that I realised it was in fact the ESC acting like it was turned on, but not connected to an RX, if this happens, it just sits there beeping at you. This issue requires further investigation, but hopefully the new VESC will resolve several issues
  • Motor Mount - As with all my previous boats, the motor is mounted to a 3D printed motor mount, unfortunately, even though the maximum current rating of the motor was not exceeded, the motor did get warm enough to deform the mounting plate, causing the heavy body of the motor to sag forwards, strangely enough this didn't cause a severe enough meshing issue of the gears for me to notice the problem until I was disconnecting the battery pack after the last run, with the new VESC current limiting is an option, I may also change the gear ratio to lower the maximum RPM to just over 18K, failing this I can also make a water cooled 3D printed motor mount, or try and machine one out of metal
  • Low Speed Power - The new motor setup is proving to be much more efficient than the old one, with a minimum reduction of full throttle amperage of 30A, low speed maneuvering at and just above idle range from 0.5 - 2A, very happy with this outcome
GoPro POV video of one of the test runs: https://youtu.be/xPyaDYFWVvc

So there you have it folks, some good, some bad, as always there is room for improvement and I hope to be testing again at the club lake on 03/06/18


More as it happens,


Alex
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Re: Water Jet Drives & 3D Printing
« Reply #197 on: September 21, 2018, 12:11:10 AM »

Hi Guys,

As you may or may not of noticed I have been very quite of late, but this is just down to the pressures of the real world interfering with my hobby time, but testing has been taking place and I am just very behind on my right ups, three to be precise and a lot has happened, as always, some good, some bad and some stonkingly awesome, but more on that later.

We pick up our tale of Jet Drive exploration on 24/06/18...

Configuration: 5065 270Kv - 1:2.94 Gearbox - 8S – 23506 RPM

First Run

  • Old radio installed kept producing same cutting out issue as last time
Second Run
  • Radio changed over
  • Short half throttle run achieved with a current draw of 30A
  • Attempted full power run failed at a current draw of 43A with motor cutting out / stalling
This did not turn out to be one of my better testing sessions:
 
  • Radio Loss - This is an annoying fault, my favourite TX has developed a fault and so I am forced to use my secondary handset, usually used for the rescue boat
  • Motor Cutting Out - Every time I tried for full throttle the motor would give out a high pitched shriek and die, now I am by far from an expert on brushless motors, but I have encountered this before, shortly before the motor in question let out all the smoke... fortunately that didn't happen, but I have read elsewhere that this can be a sign of timing, ESC frequency issues or pulling more current than the motor is happy with, whatever is causing it, it ain't happy and to be honest I am not really surprised, I wanted to test on 8S, but there is way too much gear in it at the moment, forcing the motor to work much harder than it should do, next time I will change the gear set to try and achieve a better ratio
  • Overheating - This 270Kv motor is great, but it does have one flaw, it runs very hot, now this is always going to be a problem as there is no air flow inside the prototype and these motors are more commonly found on skateboards and other such outdoor devices, hanging in the breeze with all the cooling they need, in my case, this causes even bigger issues when using a 3D printed motor mount, which sags under the heat and weight of the motor, causing mesh to be lost in the gearbox, on the second run, anything over 50% throttle towards the end just resulted in nasty noises of gears grinding
Next instalment - 15/07/18…


First configuration: Tornado Thumper V3 5055/06 580Kv – 1:1 – 8S – 17168 RPM


First Run
  • Thinking I had fixed the old radios problem, I set off with gusto across the lake and the boat performed well… for several seconds until it cut out displaying the same symptoms as before
Second Run
  • More radio problems
  • Mystery loss of drive and then no loss
  • Half throttle run achieved with a current draw of 15A
  • Static shore power pull produced 27A @ half throttle & 80-85A @ full throttle
  • Back on the old radio, after much troubleshooting I had traced the issue down to a broken aerial, which folds away for transportation on the TX, the cable inside was looking decidedly
Second Configuration: 5065 270Kv - 1:2.08 Gearbox - 12S – 24975 RPM

Third Run
  •      Changed over to alternative powertrain
  •      Short half throttle run achieved with a current draw of 19A
  •      Attempted full power run failed at a current draw of 49A with motor cutting out / stalling
Fourth Run
  • Same as third run
Some good, some bad, but a lot more positives to take away than last time:
  • Radio Issues - With the backup radio installed once again, (this is a real pain swapping over radios as I have to reprogram the ESC each time to accommodate the new throttle calibration) I set off across the lake and… immediately ran into another problem, I very quickly discovered that both TX were setup differently, so left was right and right was left, easy fix, flip a switch to reverse the channel, until I mistakenly reversed the throttle, which then went from 0 – 100% instantaneously, it doesn’t half shift from a stand still!
  • Loss Of Drive – Like always I was too impatient to try a new setup and observe the results, this tends to lead to me making do and crossing my fingers that things will hold together, this time, I wanted to test the 580Kv motor on 8S, but it has an incompatible shaft diameter with the current setup, I did however have a brass adapter I had made previously for this motor out of a length of bar with two grub screws in, not really ideal for something generating in the region of 3.4Hp, but I thought, “What’s the worst that could happen?” Part way into the run, in the middle of the lake, the prototype started to slow down, the motor RPMs started to rise and not being able to hear this at the lake side, started to increase the throttle input, what was actually happening, was coupling had become loose on the motor shaft, which was now eating the brass on the inside, this continued until the two suddenly fused together and the prototype took off like a scalded cat, it wasn’t until later when I tried to remove the motor coupling did I realise what had gone wrong
  • 580Kv on 8SThis was a very solid performance, very happy with how this went, current draw is a little high at the top end, but this motor would be an excellent choice for a slightly smaller jet unit, what we clearly need is more power
  • 270Kv on 12SThis was a setup I was very keen to test, I know this motor has potential, it is just a matter of finding the right setup, stepping up the voltage from 8S to 12S will naturally lower the current figures, I do however have to compensate for the higher motor rpms by adding more gear into the setup, this led to a bit of a standoff in the design, you see, I can only get certain tooth counts in the hardened gears I use, (sticking to off the shelf only) I also only have limited space within the hull and with the 50 tooth gear this motor was already swinging, I either had to compromise on my final ratio, or make a multi stage gearbox, something which I did start sketching out initial ideas for, but in the end I decided to compromise and ended up with a higher final drive RPM than I would of liked, but it would fit inside the hull and work. Out on the water you can tell immediately the difference 12S makes, throttle response is much snappier and with the high final ratio, at part throttle it is performing just as well as some of the other setups can only manage from half throttle and upwards, the consumption recorded was also a vast improvement, with a half throttle figure of 19A, but at anything above ¾ throttle, it again displayed the same juddering / stalling from last time, cutting out at 49A.
Overall it has been interesting using this setup, but I don’t think I will be taking it any further, at the end of the run the motor had again completely deformed the motor mount and I don’t have the time or will power to investigate the stalling issue any further.
 
Next instalment - 05/08/18…

First configuration: Gartt 5060 530Kv (700 Size Heli) – 1:1 – 12S – 23532 RPM


Couple of minor tweaks to accommodate the new motor setup:
New coupling, finally ditched the old brass homebrew units and bought an Oldham setup from RS, now for those of you not familiar with this style of coupling, they are brilliant, they lock onto the shaft just like a clamp collar does, one hub engages with a torque disc that then transfers the torque to the driven hub
Whilst giving the drive the once over I discovered a small crack in the impeller, next to where the brass coupling insert slots in, being an old impeller I decided to replace it with a new one, slight modification this time, three blades, I also included a nose cone at the front of the impeller to try and help smooth the water flow through the drive, the blades are also slightly larger on the diameter, as a smaller gap between tunnel wall and blade tip equals greater efficiency in power transfer


First Run

  • Rumbling at slow speed
  • Full throttle not achievable due to induced roll
  • Shore power pull ½ throttle @ 15A & full throttle @ 84A
  • Batteries ran out
Second configuration: Gartt 5060 530Kv (700 Size Heli) – 1:1 – 8S – 15688 RPM


Second Run

  • Shore power pull ½ throttle @ 15A & full throttle @ 84A
  • Batteries ran out
This is one of those rare occasions where everything came together and just worked:

  • Rumbling Noise – Not noticeable from the lake side, but on review of the GoPro footage there is a very clear grumble coming from the impeller, my guess is that the tolerance is a bit out and it is very lightly rubbing on the tunnel wall
  • 530Kv on 12S – Lively, frantic, explosive, insane, all good words, but they really do not describe the white and orange missile I let loose upon the lake, on 12S the power is simply ridiculous, so much so that the entire hull rolls to such an extent that air from the Port side is sucked under the hull and interrupts pump prime, so lets calculate just how ridiculous it now is:
         o   P = I x V
        o   84 x 44.4 = 3729.6 W
        o   Hp = W / 745.7
        o   3729.6 / 745.7 = 5 Hp
        With this much power on tap you would expect the usual finish here, motor got hot, motor mount melted, but no, with a maximum rating of 100A, this motor isn’t maxed out at all, meaning it             runs much cooler than my other setups
  • 530Kv on 8SThis is a much saner and more usable configuration, (but who wants that?) full power can easily be achieved and the most exciting thing that happened on this run was the batteries running flat, even on 8S though, it is still not to be sniffed at:
     o   P = I x V
     o   80.2 x 29.6 = 2373.9 W
     o   Hp = W / 745.7
     o   2373.9 / 745.7 = 3.2 Hp


So what now I hear you ask? Well for now I am going to take a break from the jet boat, I have been working on this project on and off for just over two and a half years now and I want to do something different, but fear not, this is not the end of the line, I am still very much going to finish the KaMeWa reversing nozzle properly by building the RC pneumatic system I started, I also have a new second hand hull, one of my favourite designs, which I am going to retrofit one of my slightly smaller units into for some thrashing fun, so as always, watch this space
 
Alex
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Re: Water Jet Drives & 3D Printing
« Reply #198 on: September 21, 2018, 08:55:34 AM »

Hi Alex,

Great write up - lots of interesting information/aspects to your project.

What ESC did you use?

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Re: Water Jet Drives & 3D Printing
« Reply #199 on: September 21, 2018, 12:49:18 PM »

Hi C-3PO,


I am using a YEP 120A water cooled ESC from HobbyKing:


https://hobbyking.com/en_us/yep-120a-hv-4-14s-marine-brushless-speed-controller-opto.html


Alex
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