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Author Topic: Water Jet Drives & 3D Printing  (Read 32652 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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IKB

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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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richald

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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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IKB

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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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richald

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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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bfgstew

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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?


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

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IKB

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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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grendel

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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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IKB

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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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IKB

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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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TugCowboy

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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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jarvo

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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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IKB

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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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jarvo

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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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