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[Martin13]

How does one go about measuring rpm of a boat motor. I know of a device the fly boys use on there model aircraft - the unit is made by Turnigy and the device is operated by holding in front of the prop.

Will this work reasonable accurately with a 3 blade boat prop

Mdu

[Shipmate60]

I have a hand held friction Tachometer which is fine, quite cheap on eBay

Bob

[Martin13]

Do you have a picture of it Bob - any particular manufacturer

Mdu

[Martin (Admin)]

Remember, the speed reading you get out of water will bear no resemblance to an 'in water' reading.
 ie. ... the under load RPM & current draw are much higher when trying to get out of the reeds or away from brooding swans!


If you want to go the whole hog, you need a telemetry system!

http://www.modelflight.com.au/spektrum/spektrum_telemetry_review.htm
http://www.eagletreesystems.com/Plane/plane.html
http://www.mtroniks.net/details1.asp/ProductID/441/T30.htm

[Flying Sparks]

Sorry to disagree Martin but you don't need to go as far as telemetry. I use an Eagle Tree data logger  http://www.eagletreesystems.com/MicroPower/micro.htm that collects data and stores it in the unit, then plug the logger into a PC and download the readings. You can measure many things including volts, amps, temperature, rpm, speed, even height! You just need to purchase sensors for what you want to read although the basic unit measures amps and volts. Good stuff and very reasonably priced.

Phil.

[Martin13]

Martin,

I understand that the rpm will be different out of the water compared to under load. I'm attempting to locate a problem with my current build and my hearing has malfunctioned with age, hence I find it difficult to ascertain if there is a difference in rpm between motors. I wish to try a number of combinations and knowing what the revs are would help in identifying/rectifying a problem.

I have a Turnigy device that measures current draw and voltage whilst the model is in operation (connects between ESC and motor).

Flying Sparks - I like that device - will have a good read over the weekend - thanks.

Martin du

[Shipmate60]

Martin,
I use this Tachometer but also a little gizmo I wired myself to measure voltage and current in the circuit.
This can be left connected and the current on full motor load shown.
It also acts as a battery checker as you can see the volt drop under load.

[RaaArtyGunner]

Hi Shipmate,
Take it that the meter above the Amp meter is a volt meter.
Good setup 

[Shipmate60]

sorry, yes the auto flash fired.
As you can see it has Tamyia connections so can just connect in line of the battery or motor.

Bob

[Subculture]

I'll second the Eagletree kit, excellent stuff. I have a micrologger V3 with GPS, RPM sensors (you can purchase different sensors for brushed and brushless motors), airspeed, altitude, temperature and the unit also monitors voltage and current.

Well worth the investment IMO.

[pugwash]

Can you get them in the UK???

Geoff

[DickyD]

Hi Geoff thought you were on holiday.

[HS93 (RIP)]

you can also read it real time revs volts amps temp and gps speed as the boat is sailing with  http://www.jetimodel.com/index.php?page=products&old=0&category=1 it works well

[787Eng]

I third the Eagle Tree data logger...
log your battery voltage current motor RPM and Temperature for hours if you wish while you boat is sailing along....
then look at all your data on a laptop by the water or on your PC at home.....Realtime data logging is the way to go...

http://www.eagletreesystems.com/MicroPower/micro.htm

Mark

[Subculture]

Yes you can buy eagletree kit in the UK- http://rc-log.co.uk/

You can also purchase them at quite a discount from Hobbyking.com e.g. you pretty much pay in dollars what you will pay in pounds here in the UK.

[Martin13]

Martin,
I use this Tachometer but also a little gizmo I wired myself to measure voltage and current in the circuit.
This can be left connected and the current on full motor load shown.
It also acts as a battery checker as you can see the volt drop under load.

Thanks Bob for posting pic. I tried to find something suitable over the weekend without luck. I ended up purchasing the Turnigy unit as a quick source for testing rpm's.

In the meantime I have been reading about the data logger, video, FPV and OSD  - sounds like a lot of fun.......think I will start a new post on logger/video etc - I have a heap of questions..

Thanks again chaps for your input and more ways to part with my money..

Martin du