Now then Chris ,I found a brushless motor and speed controller recommended by The Vintage Boat Company for a total price They say it is matched for a 39 in boat .So a quick look on their web site may give what you need ,it also tells which prop to match it with I,ve read somewhere the Component Shop are introducing brushless motors soon .Good luck with your search .

Try these people, Chris….

**LINK**

Bob

Hi Len,

There's currently an excellent article about brushless motors available from the front page of the Model Boats (i.e. this) website; see **LINK**. I think you'll find all the essential pros and cons explained in some detail there.

In essence, though, a brushless motor is more efficient than its brushed counterpart. To quote the abovementioned article:

"Compared to a brushed motor, a brushless motor […] makes better use of your precious battery power; is more powerful for a given size or weight, or smaller and lighter for a given power; it requires no maintenance and produces very little radio interference."

/Mattias

So far, it looks like brushless motors and their required controls are a very valid replacement for infernal combustion, without the disadvantage of the traditional cough and stop in the middle of the lake.

I've only just wondered this, but, is there an external add-on sensor that could be fitted to the shaft of a sensorless brushless motor to turn it into a sensored one?

I use a lot of brushless motors for model aeroplanes where their advantages of efficiency and low weight (especially when combined with LiPo batteries) far outweigh any disadvantages. They used to be very expensive and some of the higher quality ones still are but I've had some success with the cheaper ones. Electric models are getting to be more popular than glow … and there are far fewer dead sticks. They all use rare earth magnets which are only used on higher quality brushed motors. That's another reason for their high efficiency and low weight.

The main disadvantage for boats (and cars, I guess) is that they're not so easy to reverse. One way would be a relay to swap any two of the three connections. Some speed controllers have a reverse but it's within the initial programming and not readily achieved in operation. You can get low kv (rpm/volt) motors but they tend to be larger ones intended to be used at high power at higher cell counts (keeps the current requirement down). There's no reason why they shouldn't be used for low rpm with fewer cells. So with a kv of 400 rpm/volt the off load speed with (say) a 6v lead/acid battery would be 2400rpm.

While it's true that brushless motors generate less electrical noise than brushed, the same cannot be said for the speed controllers. Brushless esc are much more complicated because they need to generate a variable speed rotating magnetic field. In fact I've found it far more necessary to use good quality receivers with brushless motors to avoid glitches even with careful installation. The almost universal adoption of channel hopping receivers on 2.4gHz systems has largely cured the problem.

To a first approximation, an electric motor will always try to run at a speed determined by it's kv and the applied voltage. So, if you overload it by trying to drive a big prop in either the air or water it will draw more and more current in an effort to reach its speed and eventually let the smoke out of either the esc or itself. So always measure the current draw on load in an unknown drive system. Easy with an airscrew not sure how with a water one. That applies to both brushed and brushless motors.

Geoff

Everything has its place! I generally build smallish scale models and conventional brushed motor setups work fine for me. Of course if you are out for speed then things are different – and probably a bit more complicated and expensive!

Colin

Since Hall effect devices are basically sensors of magnetic fields, it makes sense that in a motor, they should be close to the rotating magnet. The rotating magnet provides something handy for the Hall device to sense, so why not use it? However, since all they do is switch on and off, there must be scope for an external kit involving a magnet to fit on the shaft, and a gang of three sensors (assuming 3 coils). Or, to get the relatively simple switching, a slotted disc and optical sensor. A bit like re-inventing replacements for CB points in petrol engines to get ignition timing.

The big problem with brushless motors is that the control circuitry has to "know" which coil to apply power to, when to apply it, and for how long. The logic for achieving this is most easily arrived at in a fast spinning lightly loaded setup, a bit like a child with a hoop and stick running down the road. As long as he keeps tapping the hoop, it keeps going. Starting a cartwheel with the cart attached needs a bigger stick, more power and very precise placement. Thus the difference between sensorless and sensored motors. A sensorless control must guess at when power should be applied, and when. Usually, it gets its instructions from the system and outputs what it assumes will do the job. Hopefully, the rotation of the motor and the application of power will agree and they will rapidly get into sync and stay there.

With sensors, this guesswork is taken out at low power and speeds because the ESC "knows" when to stop applying power to one coil and apply it to the next to best effect. Hopefully, without a penalty higher up the rev range.

'course you can , Dave. Can't think where I nicked it from, though.

Very hand these as they have a memory to record max current, so by running your boat about for a bit you can see EXACTLY what the maximum requirement of your gear needs to be.

A 100A one is on my xmas list.

Ashley

Mike

There are an awful lot more model cars around than model boats. That means there is a lot more money being thrown at that part of the hobby, which means there is more opportunity for a business to make goods, sell them and make a profit. It will take a few adventurous engineering types to experiment with geared systems; optimise them for the various applications (e.g scale, fast electric) and then maybe someone will pick up on it and make commercial products. I would imagine it will be on the usual "cottage industry" scale which model boating floats on – certainly in the UK.

I will eat one of my own limbs in public if decent gearboxes for brushless motors (when used for model boat applications) are ever mass-produced. We are the Cinderellas of the modelling world and will remain so for the foreseeable future.

Dave M

Mike

"Rule" bilge pumps are used very successfully to propel bait boats. They were developed to pump out bilge water from full-size narrow boats but they don't use brushless motors. My customers got wise to them about six years ago, since when we've equipped many bait boats with electronic gizmos to control them.

My limbs remain intact!

Dave M