Double Your Motors Power (Cheaply)

[daveives]

Want to increase the maximum power output of your motor, to twice the max power that the motor is listed for? This can be done cheaply. For example I have run a 6 ounce outrunner HB3650 motor (for $21.50 on ebay) at 2,500 watts without it even getting warm. A motor of his class is normally rated at 1200 to 1400 watts .It has pushed my scale model of the outboard boat in my avitar at 55 MPH pitot measured! The boat is a non-stepped flat bottom boat 30" long and 12" wide run on 6S lipo power weighing 97.6 ounces total. I have had OPC boats that barrel roll when the throttle is turned full on from a standing start; this has enough power to barrel roll from 10 mph with a rapid full throttle advance. How do I do this? I simply inject water from the ESC cooling hose exit DIRECTLY INTO THE MOTOR. I call this "Direct Water Injection" or DWI. You may think this is an irresponsible joke, well it is not! A cheap DWI outrunner becomes competitive with a Neu without DWI. The HB3650 has the water injected into the bottom (as mounted on an REK lower unit) and the centrifugal fan at the top of the HB3650 produces a fine mist exiting all around the periphery of the motor at the top. You might think a lot of power is lost by dumping water into a running motor, but the water flow is small and the power loss is negligible. I may have to cool the wires going into the motor though, as they get warm. In my opinion the DWI technology is going to revolutionize model boating as follows:

1) motors that are sealed (without cooling holes) will become less popular - unless the user drills holes into them
2) outrunners may increase in popularity because they can inexpensively withstand higher rpm's - the centrifugal force on the magnets helps for an outrunner and hurts for an inrunner
3) cooling jackets will become obsolete for racers

Also note that if a DWI outrunner motor is lighter in weight, it still may beat an expensive non-DWI inrunner since the total system weight decrease may more than offset the efficiency decrease of an outrunner. My boat runs in the low 40 mph range with a non-DWI KB45L08 (which weighs 16 ounces) on 4S. The 6s lipo only weighs 8.3 oz more than the 4S lipo, so the 6S outrunner weighs 1.7oz less than the 4S inrunner power system!

How about a 6S spec class to take advantage of this cheap new DWI propulsion system?

[Jeff Wohlt]

hmmmm....I would you say you are bascially shorting the motor with water and increasing power? The reason your wires are getting hot. Should be drawing more amps also.

The old trick with brushes was using brush lube "magic drops" and it is bascially kerosene.

[Make-a-Wake]

Any pics of these setups?

[Raydee]

Where does the water go once it exits the motor?

[m4a1usr]

Where does the water go once it exits the motor?

It has to be an outside the hull setup or you obviously flood the innards. Cant fault the logic. Since direct contact cooling is going to result in the best performance it has merit. But whats lacking is the data for bearing wear. Since water is going to pass thru the center of the motor its going to get inside the bearings. At least the output shaft side. And since its cooling its going to be be hotter then when it entered. So heated water is going to enter the bearing and wash out the lubrication. How much can it take before failure. Good question. It will fail at some point. When? Thats the 64 dollar question.

John

[AlanN]

[daveives]

Replies (So Far...)

Jeff - The 3 wires get warm, not hot.
- The windings are insulated, there is nothing to short in a brushless motor. I am showering the motor with water.
- I am drawing more amps and more volts (a factor of 1.5 each giving a watts 6s to 4s power ratio of 2.25.)
Make-a Wake - 3 pictures included below.
Raydee - The water comes out the top thru the vanes seen in the picture and dissipates as a mist or fog. You can also apply DWI to an inboard, an outboard, an outrunner or an inrunner.
m4a1usr - My boat has a one way bailing drain (shown in the lower right off the second picture below) which is much larger than the ESC outlet hose. It is normal to run wet, just like the full scale boat in my avitar.
- On the bearings, that is what I thought, but I have run an H&M Microcat outboard inrunner (Graupner lower unit) for 3 years now with no bearing failure in a motor that is entirely exposed and very often underwater (ie: at rest since it is self-righting). What corrodes bearings is a supposedly sealed motor that gets a miniscule leak, cools down, draws water in where it stays until the next outing, corroding with oxygen left in the motor. Contrast this with an unprotected motor which stops corroding quickly since it can easily dry completely out. About 4 months ago I started using Corrosion-X squirted into the motor at the end of a days running. I believe you can get sealed bearings, which I may try if I get any bearing failures. Note from the pictures that my drive cable is also exposed. However I am curious as to what happens with salt water.
- The water exiting the motor is not heated very much since it has a far higher heat capacity than air.
AlanN - I do not understand your comment; please elucidate.

[Raydee]

I like the idea, might be onto something there. I guess I will have to build a outboard tunnel next and give it a go?

[Jeepers]

This is not unheard of. at my work we have a electric motor turning a water impeller that runs 24/7 365days a year except when shut off for maintenance which is not very often. However it is not water cooled, it is oil cooled and its set up like Dave's water cooling,it has small circulating pump,filter and a radiator with fan. this motor was air cooled but due to its confined location it had a life span of 6 months before winding/magnet failure. Some local repair shop came up with this idea for the oil system, using direct contact on the magnets and windings, this motor has now been in place for 7 years. though I am sure that magnet in the motor has got metal deposits on it kinda of like the magnets in the oil/transmission pans in cars. I am not sure if its making more power probably not but it does last longer.

[CornelP]

I have used both inrunners and outrunners in contact with water... actually completely submerged under the hull of a springer tug. These are used as Azipods and they work like a charm. After about 4-5 hours total in the water there is no sign of corrosion o other deposits and the bearings are fine, as long as you grease them before.

[befu]

not a write off

couple of things. this is just a method to remove heat from a motor, thereby allowing you to run a larger prop or more voltage without melting components.

Efficiency. I would gess there would be a loss here. Unless the higher amperage or voltage allows the motor to run in a more efficient rpm range, the water drag will cause some loss in efficiency. As long as you are misting the motor, the loss would seem low but have not seen any real data on it. This is the setup part. Enough water mist to cool the motor, but not enough to cause excessive drag.

bearings. Sealing up anything is touchy, even in industrial settings. When it heats and cools is were things expand and contract. I have seen fine powder get into sealed bearings and freeze them up, so water is not out of the question. An open bearing might be better so it can be relubed and dried out.

inboard. Right now I epoxy seal my reciever and speed control. From my RC combat days, you can get a servo to operate under water with coatings. An outrunner as mentioned is opened and will tolerate water. The last item is the batteries. While they will handle getting wet, letting them dry out and recharging is the issue I guess. Batteries could be protected easily from a water mist spray in the hull and hulls allowed to drain so this has potential.

Motor life: When brushless motors were all pricey, this was riskier. I wonder how much power you could safely pull out of a $10 to $15 mystery or turnigy outrunner. With the rate that technology changes, a motor life of two or three years would be plenty. By then you will be wanting something better anyways.

I remember when daveies brought this up in another thread and it was interesting then. I have thought about ducting air to my outrunner to help in cooling, not worrying about sealing up the hull water tight.

I HATE having to tape hatches!!!!!

I think I will try this on my 32" skunkworks cat later this summer. A cheap build with some smaller outrunners and see how it works.

Sometimes a crazy idea works or leads to another idea that works even better. that is why it is called brainstorming.

Brian

[Brushless55]

this sounds really cool..
what about drilling the front and back of an inrunner motor to accept a water hose..
insted of a cooling jacket just shoot the water right into the motor case?
into the front and out the back of the motor then exit out the hull...

[Steven Vaccaro]

Good job Dave. My cousin used to build micro radiators for micro military motors. He always said i should try to super cool a motor for higher efficiency. Looks like you beat me to it.

[AndyKunz]

There is a loss of efficiency due to the cooling water being in direct contact with the moving motor parts. But the improvement in heat removal would probably make it worth it. I would use circulating oil rather than water (remember the heat exchanger thread a while back?) because I wouldn't want water between the laminations in the iron (if you have an iron motor) or on the Neo magnets (which rust very easily).

Andy

[graill]

I will be devils advocate.

Impractical at best, to complicated and maintenance dependant at worst. Potential for electrical failure is very high.

How is the water going to be pressurized from the water line enough to atomize, or is the requirement that large spooging water unregulated into the motor is fine?

What is the potential for added flashover protection due to high amp applications, forcing additional protections and water proofing?

what system of cowls or ducts will be used to remove said water?

What brand of whiskey were you drinking when you came up with this idea?

Is it April?

Last two are just friendly jibes, good luck on your water injection project.