Mean Machine Brushless Ducted Fan

[questtek]

While many members of this forum provide great ideas for increasing the performance of the Mean Machine in conventional ways, I am going to divert a bit and provide some alternate propulsion ideas based on specific Mean Machine applications. I know that many of you are thinking the that the only application is to go as fast as you can between point A and B. That is indeed the primary intent of building a fast electric.

My application is a bit different. I look for innovative ways to use inexpensive RC boats as platforms to collect marine data. In many cases this data collection involves very shallow water, rough seas, or the requirement to get a vast range of oceanographic and surface data.

For very shallow water cat applications, I am experimenting with the use of twin brushless electric ducted fans. I thought forum members that currently own a Mean Machine might find of interest what I am currently playing with. The pictures give you the basis of my first setup. No rudder, direction is controlled by ducted fan speeds.......and it work VERY well. The first ducted fans are 70mm on the intake duct. I run two brushless speed controls and am now experimenting with 2 to 6 cell LiPo power supplies. The 2S tests look good so I will be soon supplying a few more electrons. Will post the results.........Joe

[BassBoat88]

That is a neat idea, what is going on inside the hull? Any interior pics?, i would like to see how the fan pod is mounted.

[M.M.]

what is mounted on the transom? looks like there's still a rudder. :confused:

[DISAR]

Very innovative. Please give us some details about the ducts rpm-volts ets... because most of us have no idea about them. What speed this can go?

[questtek]

That is a neat idea, what is going on inside the hull? Any interior pics?, i would like to see how the fan pod is mounted.

Below are two pics that should answer your questions. The interior pic shows the electronics and two 3S, 2200 LiPo pacs with two brushless speed controllers. The LiPos are tied together to provide 4400 mAhr at around 12 volts supplied to the dual speed controllers. Very simple set up and easy to control using a conventional two joystick transmitter. Each brushless fan is on a different channel 2 and 3. I could mix them together but I like the control "feel" of this much better.

The ducted fans are mounted to a horizontal member via #6 x 40 stainless machine screws with a dab of thread Loc. This thin plate is made from coper clad printed circuit board, thin, light, very stiff..........and most importantly available in my workshop. The vertical fin is cut and fared from 1/4" fiberglass and bolted to the top of the Mean Machine fiberglass cowl. Note how the power wires from the two brushless motors run through the existing cowl holes. They actually help provide stability. I made these wire longer with some aerospace quality silver wire that was telflon coated blue. It will easily handle the currents with virtually no line loss...but the current is less than 25 amps anyway.

Hope this helps, Joe

[questtek]

what is mounted on the transom? looks like there's still a rudder. :confused:

Yes, good eyes. I bought this yellow Mean Machine virtually stripped. There is NO prop shaft or anything underwater except the hull. The former hole for the shaft and flex cable is temporarily sealed up. I did keep the rudder on however and it is connected to a servo inside the waterproof electronics box. It is not used for this twin turbine arrangement.

So, why did I keep the rudder on? See my next post...................Best, Joe

[M.M.]

Well very cool set-up. :thumbup:

how fast?

[questtek]

Very innovative. Please give us some details about the ducts rpm-volts ets... because most of us have no idea about them. What speed this can go?

I should mention that I am working with several different set ups that involve brushless ducted fans on the Mean Machine. In addition to the dual ducted fan system previously shown I also developed a single brushless ducted fan version.
You might think of it as an elegant "airboat" with cowl over a multibladed prop.

In this case I am using a 90 mm Aipower AP-900DF ducted fan unit. This is one nice piece of hardware with carbon fiber motor cowl. Mounted in the fan is a Feigao FG540XL with 2084 KV. It will pull about 83 amps max to give it 1600Watt max burst power but more appropriately 800 watts continuous. This has tremendous thrust. I have a 200 amp ESC on this and will probably work my way up to a 4 or 5 cell LiPo pac. AirPower rates the ducted fan at 40K rpm max and they indeed are correct. Under VERY controlled safety conditions I pushed a unit a bit beyond this and the fan blades exploded! So, I no way want to approach this max rpm on the water....or outside a concrete bunker!

You will note that I made a special cowl to duplicate that of the origional fiberglass Mean Machine Cowl. This can be made from aluminum plate, fiberglass sheet, an engineering thermoplastic, etc. The AirPower ducted fan is mounted to this via some tapered 1/2" thick delrin supports and bolted inside.

I think the pictures will give you an idea of the set up better than I can describe. My experiments are about to start. By the way, you can now understand why I kept the rudder and control servo on the first test unit with the dual ducted fan.

Best, Joe

[Meniscus]

Well very cool set-up. :thumbup:

how fast?

As I used to run hovercrafts which is a different animal all together, I would venture a guess that his current setup has a top speed around 18-22 mph. That is before he places his additional test equipment etc. for his application. Depending on the motors and the pitch and number of blades in the ducted fan, he may see upwards into the high 20's range.

Just a guess. :laugh: How close am I Joe?

How do the motors hold up in salt spray?

[questtek]

Speed???? That is the reason for the tests. Buy my proviberal "Ace-in-the-Hole" is shown in the attached picture! I think your estimates are pretty good.

These machines will be run in fresh water only. I am sure heavy salt spray would take its eventualy take its toll on all the brushless motors. The giant fans not only suck in large amounts of air...but also salt spray. However, that said, there is a way to eliminate this problem if someday I do want to run them in saltwater.
One one of the canard pics I sent out I developed an underwater version of a large outrunner where the entire motor pod is underwater...in saltwater.

Back to the question of speed. I have several ways to measure speed. One is Eagle Tree, the other is a tiny, thumb-sized self contained GPS/Speed recording unit and the third is a full blown Pentium computer set-up running WIndows XP and a lot of sensor and video interfaces. Pics included on one of the miniature computers are attached. This electron marvel runs on 5 VDC and takes only a few amps of power. All solid state memory so no problems with disc drives and vibration. It has a wireless link built in so that some very powerful real-time data analysis can be done. Now it is just finding the time to do it! Best, Joe

[Brushless55]

That looks like it should move out real good!

[bustitup]

Questek where can i foind a piece of that black flat cowl material? you got a piece i can buy....its for my mean machine mod hatch


I should mention that I am working with several different set ups that involve brushless ducted fans on the Mean Machine. In addition to the dual ducted fan system previously shown I also developed a single brushless ducted fan version.
You might think of it as an elegant "airboat" with cowl over a multibladed prop.

In this case I am using a 90 mm Aipower AP-900DF ducted fan unit. This is one nice piece of hardware with carbon fiber motor cowl. Mounted in the fan is a Feigao FG540XL with 2084 KV. It will pull about 83 amps max to give it 1600Watt max burst power but more appropriately 800 watts continuous. This has tremendous thrust. I have a 200 amp ESC on this and will probably work my way up to a 4 or 5 cell LiPo pac. AirPower rates the ducted fan at 40K rpm max and they indeed are correct. Under VERY controlled safety conditions I pushed a unit a bit beyond this and the fan blades exploded! So, I no way want to approach this max rpm on the water....or outside a concrete bunker!

You will note that I made a special cowl to duplicate that of the origional fiberglass Mean Machine Cowl. This can be made from aluminum plate, fiberglass sheet, an engineering thermoplastic, etc. The AirPower ducted fan is mounted to this via some tapered 1/2" thick delrin supports and bolted inside.

I think the pictures will give you an idea of the set up better than I can describe. My experiments are about to start. By the way, you can now understand why I kept the rudder and control servo on the first test unit with the dual ducted fan.

Best, Joe