janssnet

Super fast RC Boat (2.4 GHZ) - Not for purists!

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Hi folks,

Most LEGO boats have out-board motors. Not very elegant, not very fast. I felt a strong urge to find out if in-board was possible. And, if the LEGO hulls could handle some speed.

Although it did require a 3D-printed part (a so called stuffing tube), it worked out well. Built in some 2.4GHz RC components to make sure the boat could be controlled from a distance. And included a modest brushed elektromotor. 

Please have a look at the result hereunder.

Leave a comment if you wish to see more details. Happy to share.

Currently working on a optimized version: The prop behind the boat, not under the boat. Less resistance, more speed, more control.

 

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35 minutes ago, TechnicSummse said:

Is the screw printed, or a lego one?

Do you know how much rpm the screw does?

The propellor is a Grauphner standard prop : EAN 4013389487511

It turns out an M4 screw fits pretty well into a Cross Axle Extension (59443). This holds the prop and Extension together. Going backwards is not advised though :)

The brushed elektromotor runs (unloaded) max. 20.000 RPM.

During the first test (the video) the boat didn't reach full throttle yet. Wanted to get a feel for speed and steering-control first.

Edited by janssnet

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The water helps a lot, I think... it cools down most of your moving parts, and offers rather good cushioning to your boat's body.

However, given the rpm and propeller size, have you considered doubling - Use two (or even more) propellers to move even more water in the same time...? :devil: Serves as backup too, in case one of the propellers drop off far from shore... 

Edited by PorkyMonster

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4 hours ago, MattL600 said:

It is amazing!

The only worrying part is the bit that holds the propeller in place, does it warp?

It's hard to tell if it warps. Should put a camera under water to be able to view what's happening. But the weight is reaching its max already.

However, without under-water-shots it's half the fun. Will give it a try soon.

3 hours ago, PorkyMonster said:

The water helps a lot, I think... it cools down most of your moving parts, and offers rather good cushioning to your boat's body.

However, given the rpm and propeller size, have you considered doubling - Use two (or even more) propellers to move even more water in the same time...? :devil: Serves as backup too, in case one of the propellers drop off far from shore... 

Would love to have two motors and two props, but there is too limited space left in the hull and the weight is becoming an issue. Any ideas?

Edited by janssnet

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25 minutes ago, janssnet said:

It's hard to tell if it warps. Should put a camera under water to be able to view what's happening. But the weight is reaching its max already.

However, without under-water-shots it's half the fun. Will give it a try soon.

Would love to have two motors and two props, but there is too limited space left in the hull and the weight is becoming an issue. Any ideas?

Try doubeling just the output from the one motor, this should be pretty easy, and room-saving. 

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17 hours ago, janssnet said:

Would love to have two motors and two props, but there is too limited space left in the hull and the weight is becoming an issue. Any ideas?

As mentioned by @TechnicSummse, I was only referring to the doubling of propeller :laugh: just to achieve redundancy in case one of them drop off far from shore... unless you're thinking of something like this (then you'll have no problem with space and buoyancy): 

hqdefault.jpg

 

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Both attracted and repulsed by this. Not something I would do but definitely fun to watch :). I wish though TLG would give some more love to Technic boating enthusiasts. Instead of always focusing on land vehicles.  

Edited by Kelkschiz

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I'm kind of impressed you need this small propeller to have SPEEEED. It is now clear for me how inefficient LEGO propellers are, sadly.

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I like your video on YT about different ways to plug up the hole in the bottom. Nice 3d printed part

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22 minutes ago, zux said:

I'm kind of impressed you need this small propeller to have SPEEEED. It is now clear for me how inefficient LEGO propellers are, sadly.

With only a little effort you can create a far more efficient, LEGO compatible, propellor. 

Happy to explain in some detail if there is a need.

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Hi folks,

Just launched 2.0 of this RC LEGO boat. The result is far better than expected. Spectacular speed, stable steering. Great fun!

Have a look at the youtube video.

Main improvements compared to previous version:

- Propellor steering instead of rudder steering (works surprisingly well)

- Prop behind the boat (not under the boat)

- Better stuffing tube (reduced angle of 10 degrees, less resistance, better torque))

- Adjustable trim tabs (to lower the bow and to compensatie torque roll)

 

The main challenge that is left is to handle the torque roll. Have not yet reached full throttle since it results in starboard going into the water. Any suggestions?

 

Edited by janssnet

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maybe make pontoons to each side of the boat? I dont really know much about boats.

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The final version!

Torque roll is under control, thanks to the trim tabs. Perfect planing and no porpoising at higher speed. No leakage, boat returns safe and dry. Resistance is minimised using an optimised version of the propellor steering.

The LEGO components stay in perfect conditions, no wear-out. 

And this is all achieved using a brushed elektromotor. Imagine what happens when including a brushless motor ....
 

 

 

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