Vintage Gentleman’s Cruiser

[Paul TParticipant @pault84577]

Hello Bob

Everyone knows the size of models and weird motor combinations that I build (big, heavy and power hungry) but I can honestly say that I have never had any problems with ACTion P94's.

Even with some of the crazy motors that I up-cycle from power tools the P94 has never let me down,

Disclaimer…..I should add the caveat that I use 1 P94 per motor and that I always check the full amp load of these crazy motors before connecting them to the P94.

Paul

DM.. brown envelope to the usual address

[Bob Abell 2Participant @bobabell2]

Thanks Paul

All in good time

Work in progress…….Added a temporary green stripe…. (adhesive tape)…….Just to see the effect

Bob

Edited By Bob Abell on 21/03/2015 17:18:51

[Paul TParticipant @pault84577]

Hello Captain Bob

Impressive.

The boat looks very pretty and the green tape actually offsets the red and white.

You have made me think about the dark art of testing motors for amp draw and how Kevin might not know how its done, do you think that we should do a quick 'idiots guide'

Paul

But thinking about it one probably already exists somewhere on the forum

Edited By Paul T on 21/03/2015 17:38:49

[Bob Abell 2Participant @bobabell2]

Good idea, Paul

I need a refresher course too, at this stage of play

I assume that an ESC is not required at this stage?

Bob

[Paul TParticipant @pault84577]

No ESC is needed for this test.

Just a half full bath, a wetsuit, the ability to juggle and a very understanding 'other half'

[Bob Abell 2Participant @bobabell2]

I'm not surprised you need a wetsuit

With only half a bath…..The water will pour out!

Bob

[Paul TParticipant @pault84577]

Very good Bob you should be on the stage

I should have said you need enough water in the bath to enable the boat to float with a clear couple of inches below the keel [ or in your case wheels]

[Paul TParticipant @pault84577]

THE IDIOTS GUIDE

How to test the amp draw on your latest creation.

Firstly you will need one of these

A basic amp meter or multimeter

Set the meter to Amps (read the manual) and connect the meter between the battery and motor, as below

You don't need a speed controller or transmitter.

The motor must be fitted properly in the boat and connected to the propshaft and the propeller.

Place the boat in the bath so that it is floating freely with a couple of clear inches below the keel.

Carefully connect the battery as shown above………be aware that this setup is the equivalent of full speed, your model will move forward and produce a lot of prop wash (hence the need for a wetsuit)

The meter will show a reading which is this motors maximum amp draw in this particular hull (if the meter shows a negative reading simply switch the terminals on the battery) this is a good time to check the motor is turning the correct way.

The reading is called the 'On Load reading' and from this you can work out what ESC rating to use.

It is good practice to use an ESC rated at least twice the On Load reading for example a reading of 8A (8×2 =16A) so a 20A ESC is required.

 

That's it.

 

This test would be very revealing on experimental motor setups (like the Bobabell Drive) as depending upon how the motors are wired together…..either series or parallel…..different amp readings will be produced and these results might be far higher than the manufacturers data might lead you to believe. 

 

Don't forget to fit in line fuses to protect against overload and motor 'stall'

No ESCs were hurt during these tests and no fingers were lost however the bathroom carpet was ruined
 

 

Edited By Paul T on 21/03/2015 19:23:54

[Bob Abell 2Participant @bobabell2]

Hello Paul

That's simple enough, but perhaps the bath is not the best place for this test?

The figures the makers publish, don't mention the size of prop or pitch etc?…….eh?

No wonder the MFA850 amp figures have various figures?

How about…..Watts = Volts x Amps deciding the Amp figure…….Knowing the Watts of course

Bob

[Paul TParticipant @pault84577]

Bob

The only 100% of getting the correct figure is to do the bath test.

The test is essentially the load placed on the motor by the shaft and submerged propeller.(change the prop and the test result will change.

We should also explain to Kevin that the AbellDrive introduces a few unpredictable variables due to the way they are wired together, this is where the amp reading is important as the twin motors acting with/against each other could produce some very high amp readings.

Not only does this influence the choice of ESC it is also essential for choosing the correct batteries and wiring.

Paul

[Bob Abell 2Participant @bobabell2]

The Abell Drive motors will never oppose each other

If I was sneaky…..I could simply wire up one motor and nobody would be the wiser!……….Ouch!

Bob

[Paul TParticipant @pault84577]

The Abell Drive motors might not oppose each other but depending upon how they are connected together they could produce a high amp draw.

Whilst we are having fun bashing this back and forth its important for Kevin to understand that exotic motor setups can result in some very strange electrical effects.

For example having 2 motors with a manufacturers rating of 8A for each motor you would think that the maximum draw would be 16A…… but this isn't necessarily the case as there could be a theoretical 20A.

Paul

[Gareth JonesParticipant @garethjones79649]

Paul,

You may not hurt any ESCs by doing the test you propose but you will certainly give your multimeter a shock. The one illustrated reads up to 200 milli amps, as best I can read from the picture. A typical set up with an 850 motor is likely to pull around 20 amps so that's about 100 times what your meter is designed to read. Assuming it has a fuse it should be protected, but it won't give you any time to get a reading before it blows. Most multimeters are not designed to measure current much above one amp. You need either a dedicated ammeter, or better still a wattmeter which is designed to measure current, voltage and calculate power. Something like this would be a better tool for the job.

Wattmeters are readily available, widely used by the electric flight fraternity and no more expensive than a multimeter.

Gareth

[Bob Abell 2Participant @bobabell2]

I think, somebody has opened Pandora's Box here?

Bob

[ChrisBParticipant @chrisb29081]

Escaping from Pandora's box is a variation on a theme question for Paul. How do we measure the wattage when using a brushless motor, with its three wires? Thanks

Chris

[Dave MilbournParticipant @davemilbourn48782]

Chris
You will notice that while a brushless speed controller has three wires for its output to the motor it has just two wires for its input from the battery. It is in these two wires that the wattmeter is inserted. Unlike a brushed motor you can't run a brushless one without a speed controller because the latter is actually an integral part of the motor – even if it's a separate unit physically.
Ta-da!

Bob
If you don't understand the basics of electricity then you really shouldn't be using it to power model boats. It might be complicated to some folk but it can be expensive and dangerous to ignore. My article was written to help – **LINK**

DM

[ashley needhamParticipant @ashleyneedham69188]

I had a thread called "wott meter" or something a little while ago as i found a small in line 30A meter similar to Gareths. DM has since seen a 100A one, and they are v useful. The one I have also records max current draw so you dont have to stare at it all the time, just plug in between batt and ESC and look at it after testing.

It is the way to go. We have been using it lately on Trevors project where it provided interesting info concerning prop choice and so on..

Bob. You NEED ONE OF THESE things. The ABell drive is a fairly juicy item and you need to know what current it is actually pulling, on a worse case scenario (held stationary on full throttle).

Ashley

[Bob Abell 2Participant @bobabell2]

Hello Ashley

i remember your thread with the Inline amp reader

Do you think a 30 amp unit would be about right?

It sounds handy for my drives

Many thanks

Bob

[ashley needhamParticipant @ashleyneedham69188]

Bob. 30W is probably all you need BUT the 100A one DM found was hardly any more expensive so you may as well get one of those.

It is so easy to use and consists of nothing more difficult than fitting the connectors your batteries use (mine camne without connector ends on, so you can fit whatever you want), plugging in and pressing the little switch on the side to switch between the volt/current/watt displays.

Ashley

[Dave MilbournParticipant @davemilbourn48782]

For your info **LINK** Comes with spare Deans connectors which fit Component Shop Deans type.

DM

[Paul TParticipant @pault84577]

Dear All

The information that I gave was The Idiots Guide and intended to make Kevin think for himself rather than rely on dubious second hand information.

The images and commentary are almost correct (but deliberately incorrect) and with them I was demonstrating plausible but misleading second hand information.

For example the multimeter shown wouldn't produce the reading shown in the line drawing, so its no good buying a meter without checking what it will do (hence the comment about reading the manual)

The P94s are almost good enough for 850s but not quite upto the job (hence the comment about doing a Amp test and getting the correct result for each set up)

The upshot of all this techno babble is to show that you have to do your own research and conduct your own test and not rely upon other peoples iffy advice.

Paul

[ChrisBParticipant @chrisb29081]

Thank you Dave, I and the other Kevins understand.

Chris

[Dave MilbournParticipant @davemilbourn48782]

WHAT'S WATTS??

Edited By Dave Milbourn on 22/03/2015 16:19:20

[Paul TParticipant @pault84577]

Didn't Watt invent the kettle?

[Dave MilbournParticipant @davemilbourn48782]

WATT?? KETTLE?? WHAT KETTLE?? O, I HATE YOU!!!!! So unfair……………

(Remember these? You used to be one……………..and so did I).

[Author]

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