ESC Problem

[David Marks 2Participant @davidmarks2]

A friend has acquired a model lifeboat, GRP hull and superstructure 775 mm long. The boat runs but then after few minutes cut out i.e. no power to the motors. When this occurs the Esc is found to be hot but after cooling, the models functions OK. It is therefore considered that the ESC is either faulty or possibly the wrong unit for this particular installation. The relevant components are as follows: Motor: Graupner Speed 600BB Turbo X2 running on 12V. ESC Tornado Marine X1, 50A forward & 20A reverse. Props are 24mm Dia, 3 Blade. Any thoughts on the source of the problem would be much appreciated.

[David Marks 2Participant @davidmarks2]

[Ray Wood 3Participant @raywood3]

Hi David,

Those are really tiny props for 600 size motors, I find a 400 size motor turns a 30mm 3 blade with ease, is there room for 35-40mm props on the model ??

They have no load and are over-revving ??

12 volts is high , I've never used more than 7.2v

Regards Ray

Edited By Ray Wood 2 on 22/05/2019 09:16:03

Edited By Ray Wood 2 on 22/05/2019 09:19:18

[Malcolm FraryParticipant @malcolmfrary95515]

I've had a problematic Tornado ESC, replacing it with a Marine Viper 25 in instead solved everything in one go. My problem was, early on, poor control, on its last trip, sticking on full forward.

Small props will never cause overheating of either the motor or ESC, over-revving will not be a problem unless the motor is not rated for the voltage that it is running on, and it will be the motor suffering, not the ESC. The ESC heating indicates that it is having its actual (rather than what the label claims) rating exceeded. And in that case, rapid brush wear would be the problem. Not having the spec sheet handy, I don't know off-hand what voltage the speed 600 bb is rated for, but from the name its a 540 with a lowish turn count and thick wires to carry lots of current. 9.6 rings a bell, somebody will know for sure. A very ordinary 540 (but rated for 12 volts) will be perfectly adequate, even more if mated with a 2 blade prop about the same size.

12 volts suggests a SLA battery – this might also not be up to providing what a "Speed" motor wants. Could be that the hot ESC is a side effect – the battery might just want some recovery time.

The boat where the Tornado let me down was second hand, the previous owner told me it went very well with a 12 volt battery and the battery compartment was set up for an SLA. I used a 7 cell NiMH pack instead. The thing woul plane for fun and had a surprisingly long cruise time, probably due to not having to lug lead ballast around.

[Dave MilbournParticipant @davemilbourn48782]

I would say that there are several things which your friend needs to do. First I agree with Malcom that 12v is too much for any Speed 600 motor and that 7.2v should be seen as the norm. The nominal voltage rating of Speed motors is usually prominent on the label. I also share his preference for using anything but lead-acid batteries! Next, the props are a bit too small to have much significance. I used a 32mm 3-blade bronze prop on my old 540 motors and they were very happy together.

I'd not advise using one ESC for two motors unless they were of much lower power than the ones he has, and the Tornado ESC is not top of my "best buy" list anyway. Better to use a separate ESC for each motor, even if they are connected via a Y-lead to the same Rx channel. It halves the current through the speed controllers and leaves you with the means to get the model back if one goes pop. If the ESCs have BEC then you need to disconnect the red lead from the Rx plug of one of them.

DaveM

[David Marks 2Participant @davidmarks2]

Gentlemen – Many thanks for your input and help. Just one further question for DM. Following you earlier guidance, I now use Action Electronics ESCs. What would be the best ones to use in this application i.e using twin ESCs?

Regards – David Marks

[Dave MilbournParticipant @davemilbourn48782]

P80 will cope with continuous current up to 20A. It doesn't have BEC so you'll need either a separate Rx battery or a stand-alone UBEC.

Dave M

[TelstarParticipant @telstar]

Hi David. I agree with some of the comments above. But Graupner Speed 600BB Turbo is in fact a 12v nominal motor

motor nom.v v.range rpm no load load at best effy stall amp overall effy.

Speed 600BB TURBO 12v 4.8-14.4v 17,200 1A 7A 40A 77%

dimensions 57mm 37mm 8.7mm 3.17mm 220g

these are Graupner figures.

For the Esc to get hot, there is a current issue either the esc itself does not match the makers claim, or the motors are overloaded ie tight shaft badly aligned or over propped .

I would put an ammeter in the battery lead to check the actual current , replacing Esc will not cure the problem IF it is a mechanical fault

Cheers Tom

ps is the Esc free to cooling, or is it covered over unable to keep cool? just wondered

Edited By Telstar on 24/05/2019 15:29:50

[Dave MilbournParticipant @davemilbourn48782]

Tom

I may be wrong but I think there were several dfferent types of Speed 600 BB Turbo, all with different nominal voltages. I wouldn't argue with anything you say about overloading etc.

Dave M

[Malcolm FraryParticipant @malcolmfrary95515]

A very quick goggle for "graupner speed 600 bb turbo" shows listings for both 7.2 and 12 volts on different links, so without seeing the label, anybodys guess.

An exotic thought – perhaps everything is set up to Futabas standard resulting in the ESC being "normally reversed", so normal running is using the "20A" bit? Still, if a particular ESC lets me down once, it makes me reluctant to give it the chance to bite me a second time.

[David Marks 2Participant @davidmarks2]

I will ask my friend to check the labels on the motors. I just "Googled" the motor description and up popped 12V. The model was minus batteries when acquired but has been set up with 2 X 6V SLAs in series, so may be worth trying with the same batteries but wired in parallel. I will also check the free running of the prop shafts. I can confirm the the ESC is in ample free space in the hull and not closed in at all.

[Dave MilbournParticipant @davemilbourn48782]

David

17,200RPM is much too fast for a semi-displacement hull, even with very small props. With two heavy SLA batteries it's not hard to picture the model wallowing in the lake, motors screaming, while trying its best to boil way the contents. Tom's advice to measure the current draw while running is an excellent one; anything more than about 10A per motor is a waste of battery power because it's all going in heat. You can buy a decent 'watt-meter' whcih can be fitted into the model to monitor and report on the current drawn in actual operation. Here's just one **LINK** No doubt there are plenty of others available.

Dave M

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