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3D Printed 28mm Boat Jet Drive Unit

Posted: Sun Apr 03, 2016 3:35 am
by Josh Hess
In this post I will be talking about the 28mm jet drive unit I developed for an autonomous boat project. The main purpose for modeling and 3D printing this was to greatly reduce cost of the assembly. Some of the similarly sized jet units sell for over $70 and the budget for the project was $80. Using only 3.1 cubic inches of material, it cost about $20 to 3D print. It was also tweaked and optimized for the hull I designed and also for easy 3D printing. It is designed with a motor mount for a 750 Series brushed motor. They can be found on ebay for around $10 and provide ample power. Here is where I got mine: ... EBIDX%3AIT If you wish to use a brushless configuration, a simple adapter plate can be 3D printed or lasercut.

I am putting up the files for free and you can do whatever you want with them. If you build it into something cool, be sure to post a topic with your project. If you want to share the files with someone else, be sure to send them our way so they can check out the site. Modeling credit goes to Mike Ache.

28mm Boat Jet Drive Unit: viewtopic.php?f=22&t=19

If you are planning on building a boat and are in need of a hull, this one is designed to work perfectly with this jet drive:

22" Deep V Mono Hull Templates: viewtopic.php?f=22&t=15

Lets see some tests. There are two different nozzles included in the files provided. One is the same diameter as the duct (28mm) and the other is slightly smaller (around 17mm). The smaller one is designed for much higher speed while the larger one is designed for more power. Either way, this thing moves! Here are a few videos showing testing of the jet unit:

Re: 3D Printed 28mm Boat Jet Drive Unit

Posted: Mon Apr 04, 2016 5:23 pm
by Radiation8
Nice project, the new videos show that thing hauls! Keep your eyes and ears open for people getting rid of RC Cars (or selling them cheap), specifically a purple (or blue) Scorpion 12 turn brushed motor, those things were BA, took a beating and I had one up until about 2yrs ago, till I sold all my RC stuff and it worked just like new, threw all the beatings I gave it. The 12 turn motor might use quite bit more power but maybe not that much, since that boat is so light. Higher Turns = more Torque and better battery, Low Turns = low torque but higher RPM, and more battery. I'm guessing you want a balance of both to keep it in check for driving around the pond, etc..

If you wanted to get real crafty, a few folks have actually wound (or re-wound) their own motors to lower turns, think 9t and 3t LOL!

Did you ever find out the amp draw on that thing? The amps while holding it in the water might show a higher reading than if it was going full tilt across the water, just like in an RC Car. Humm Can adrenos measure amps? And data logging for those measurements? Although you may not give 2 hoots about amps. :D

Re: 3D Printed 28mm Boat Jet Drive Unit

Posted: Mon Apr 04, 2016 7:05 pm
by Josh Hess
Yeah, I used a much lower turn motor in my previous boat and it was definitely higher rpm. I will have to look into a lower turn motor to use on this just for fun.

I don't know if I can rewind this one as it is a generic can design and they are hard to open. Previous experiences with them did not have favorable results.

As for the amp draw, I measured it at 12v and it was pulling almost exactly 15A. So at 7.2 it's probably pulling around 7A or so and at 14.4v it's probably pulling over 20A. For this project, I am using a solid state relay to control it and it is rated for up to 40A, so it shouldn't be a problem. As far as data logging is concerned, it can be done, but it would involve a hall effect measurement of the wires and it would be kind of involved. It would be interesting to see if it pulls less at top speed though.