Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length.

[Umi_Ryuzuki]

So much for the no wake zone,... 

[PeachyPM]

  what a glorious way to go! In the name of EWTP! (Engineering Workshop Theory & Practise) may I suggest some sort of cunning lid/deck on the next test vessel?
Oh! & well done on not throwing every laughing club mate (inc me & Jimmy) into the water. That shows a marked development in general  Bon Hom!   

[IKB]

Hi Guys,

Yeah, I learnt the hard way that jet boats off throttle don't steer and due to the hull design, with no rudder or other low hanging machinery like a prop, there is very little drag to slow you down either!

The water cooling jacket that I ordered for this boat seems a little bit OTT after this weekends exploits 

[IKB]

Hi Guys,

Some great news this evening, after sitting on the radiator since the weekend, I put the prototype back on the bench and everything works, outstanding!

Video here: https://youtu.be/8IPqc-KSh54

Although, where the brass rod went through the impeller, it has left some pretty ugly gouges, but that is one of the great things about owning a 3D printer!

Alex

[PeachyPM]

If at first you sink...dry,dry & dry again

[IKB]

Groan... yes mate, very good 

[essex2visuvesi]

If at first you sink...dry,dry & dry again

[PeachyPM]

Tough crowd!

[essex2visuvesi]

Tough crowd!

Actually I thought it was rather good

[IKB]

Hi Guys,

Quick update on the jet drive, I am currently working on a reversing mechanism... can't imagine why  The design i progressing nicely, unfortunately, multiple printing failures this weekend have scuppered a prototype being completed, so here are a couple of screen grabs of the CAD and a short animation of the motion.

Animated motion: https://youtu.be/Q-vVDgnZxAQ

Alex

[hopeitfloats]

going to take a good servo to work it with the link to the bucket being so close to the pivot point. possible it may lose water out the side rather than redirecting it back. not that it wont work but it might be a bit slow reversing.  sorry if it sounds so negative because the unit is a nice build. just a couple of potential problems you could have.  nice simple way to do it though

[tigertiger]

As an aside, I saw a news report from an Indian tech/entrepreneur show. A guy there has developed a portable 3D printer. Once the big companies follow, that will see more 3D printing generally. This will drive down prices, increase use, and see development of both machines and software applications.

[IKB]

Hi Guys,

Quick update on the new reversing mechanism, managed to get out to the shed last night and test assemble the new design, one small issue is the reversing lever needs to be taller to allow clearance for the steering linkage on the bucket and there are a couple of minor tolerance tweeks to be made here and there, but overall I am very pleased with it so far.

Alex

[Charlie]

Hi Alex,
That is an impressive piece of work, well done! Would i be right in thinking that you have now gone beyond creating a Jet Unit specifically for the Stolly, and that you are now intending to create one suitable for a boat? Reason i ask, is that i was intrigued by how the Stolly Jets worked, and came upon this illustration, when i was Googling. It appears to have a reversing Mechanism, but no Steering, so presumably they steered 'Tank Style'.
Charlie

[Danny]

The Stolly had two levers in the cab for left and right bucket (tank steering). This was aided by turning the wheels (front four steer) which gave a sort of multiple rudder assistance.
Cheers
Danny
 

[hopeitfloats]

certainly looks good alex. very professional
 

[IKB]

Thanks for the positive comments guys, always appreciated, few quick replies:

• Charlie - Yes & no, I have indeed gone off on a tangent with this, but I still fully intend to design a custom jet unit for my Stolly model. The aim at the moment is to create a fully working unit, for which I need reverse, which I may sell kits of at a later date.
• Danny - Quite correct
• hopeitfloats - Cheers

Alex

[IKB]

Hi Guys,

Been working hard to rebuild the jet boat prototype this week, last night I finished the CAD for the improved MK2 model with reverse and the printer churned out all the parts in just under 13 hours 
Plan on doing the assembly tomorrow, so hopefully more photos and maybe some bath trial videos in the next couple of days.

Alex

[Captain fizz]

I continue to be amazed by the capability of 3D printing! Well done Alex, superb work!


Simon

[IKB]

Hi Guys,

Made good progress on the jet boat prototype today, couple of minor tweeks to be made and a couple of small changes to be printed in the morning, but apart from that all is going well.

With the new and improved MK2 version, I am replacing everything that is outside the hull with new components, which means removing and replacing the stator nozzle, but this means I can replace the damaged impeller that ingested a brass rod, which ironically, was meant to keep foreign objects out! 
I knew from the noise it made on the lake that the damage was bad, but it still performed well after removal of the brass rod, on closer inspection, it is pretty messed up

Alex

[Captain fizz]

Yes, it hasn't done that a lot of good!
As you say, a certain irony that it was caused by part of the intake strainer. It just reinforces the fact that there is a huge volume of work involved in developing this sort of project.
Keep smiling Alex!


Simon

[IKB]

Hi Guys,

Well, lots of progress made today, unfortunately no test video of the boat as there was a yacht regatta on the club lake today, so first trials will have to wait until next Saturday.

She is complete though and ready to go with many new features installed:

• Full water cooling system for brushless motor, as this was getting rather warm before
• MK2 output nozzle with reverse mechanism
• New robust intake grill, 3D printed as one solid part so it won't end up in the impeller
• New impeller
• Refinements to onboard electronics, like an on / off switch, all mod cons here
• New 3D printed servo mounting brackets
• New orange acrylic lid with clear door to keep the lake on the outside this time 
• Not shown in photos, but I have mounted my GoPro camera to the rear of the boat, so should be able to get some interesting footage next Saturday

Video from the workbench showing servo test:
https://youtu.be/5Aai8rE8klk
Alex

[IKB]

Hi Guys,

Made it down to the lake today and conditions were favorable, next to no wind and very calm waters, had a couple of runs with the boat and drew the following conclusions:

• Water ingress into hull being caused by impeller shaft leaking
• New design of intake grill appears to be to restrictive, causing impeller to cavitate in housing, leading to a loss in overall speed
• Reverse flap does work and effectively kills forward motion when power is applied, mixed success using it to sail backwards, will look into more conventional bucket type design
• Water jacket cooling on motor is working, although I think it would benefit from larger bore tubing on the inlet and outlet

Overall I am very pleased with today's performance and after a redesign of the reverse mechanism, I will be moving swiftly on with the Stolly version.
Youtube videos of today's exploits:

• Video taken from lake side of boat underway: https://youtu.be/erfAy4z3WE4
• Video taken from on board GoPro camera: https://youtu.be/VTC6kjiPoWs

Alex

[Captain fizz]

I would say that that was a very successful test run Alex.


Simon

[tsenecal]

It looks like the reversing flap isn't sealing against the main body, giving you a nice fan effect of water spraying past the reversing flap...  seal that, and your reverse will improve.