Two motors and one ESC

[Jim CrookstonParticipant @jimcrookston25296]

The article in MB, March 2019, All British Whaleback, showed a method to control two motors with one ESC. I am trying to do this in my 1/24 P2000 Archer Class boat. I am using a viper 25 plug and play, Futaba Rx and two M500 motors in a 12volt supply. I have fitted a 15 amp fuse in both motor supplies, the article shows only one fuse. My problem is that the set-up will work when running one motor with the other disconnected, it doesn't matter which one but when trying to run both together, neither will run. As both motors run individually, I am happy that all connections are good. Can anyone help me, PLEASE, and tell me what I am doing wrong?

[Jim CrookstonParticipant @jimcrookston25296]

Article in MB, March 2019

[Colin BishopModerator @colinbishop34627]

Jim,

Are you certain you have followed the wiring diagram exactly? As shown in the magazine the single fuse protects both motors which are wired in parallel. If you have inadvertently wired them in series (the power to the second motor passes through the first) then it is often the case that only one motor will run.

Colin

[Jim CrookstonParticipant @jimcrookston25296]

Colin,

Thanks for your prompt response. I have them in parallel. The problem is that when both connected neither will run. Individually it's fine.

Jim

[Colin BishopModerator @colinbishop34627]

Maybe Dave M can suggest what the problem might be.

Colin

[Charles OatesParticipant @charlesoates31738]

Hi Jim, you could try 2 things. Firstly try shorting out the fuses just in case there is a resistance problem with them.

If that doesn't work, disconnect one motor leaving just the two wires free. Then set the other motor running as normal and touch the two free motor wires to the running motor terminals. If that works yo have a wireing problem, if it doesn't, I have no idea.

Chas

[John W EParticipant @johnwe]

hi there, reading on Mtroniks website

"Running at 12V, at maximum efficiency, the M500 will run at around 24000RPM and pull around 4Amps. Start up current, depending on prop size, would be around 15Amps".

So, therefore, although you have both motors fused, the total load on the actual speed controller on start up is over the limit of the speed controller and the speed controller may think it has been overloaded and shut down – so that is why you may not have two motors to run off one speed controller, so that is one possibility. The other thing is when a normal motor starts up, even not on load, it can take horrendous amperage just to get it started momentarily. 

John

Edited By John W E on 24/02/2019 12:12:25

[Jim CrookstonParticipant @jimcrookston25296]

Many thanks to all, going off with my AVO now to measure currents. I think it could be an overload closing the ESC down as John mentioned above. Will let you know results however probably not until tomorrow (domestics to do this PM).

Many thanks again,

Jim

[Dave MilbournParticipant @davemilbourn48782]

Unless it's a simple case of incorrect wiring then I'm afraid I can't. I have very little experience of MTroniks Viper ESCs and I'm not likely to gain any more – being a convert to brushless these days. I might be tempted to check the current drawn by one motor on 12v. MTroniks say that the M500 motor daws 4A at 'max efficiency' but that the start-up current can be 15A. That's 30A for a pair, which might be enough to trigger the cut-out in the ESC – but I'm just guessing. I've heard that the folk at MTroniks are very helpful if you ring them 01943 461482 .

As an aside, I have distinct reservations about use two such motors ungeared in a model like a scale Archer Class – 24,000RPM?? Are you serious?? I'd hesitate to run 540s on 12v anyway, mainly because I don't think plain bearings would last very long at that speed, and I certainly wouldn't run two such motors from one ESC – unless it was a P94 which is designed for the job.

i was composing this before the last two posts "hit" so sorry if I seem to be go over ground that's been covered. Still, it's comforting to know that Mr Elsy is thinking along similar lines!

Dave M

 

Edited By Dave Milbourn on 24/02/2019 12:37:07

[Colin BishopModerator @colinbishop34627]

Subject to Dave's comments on your motor/shaft setup, if you need another speed controller then you can operate them both from the same receiver channel using a Y lead.

Colin

[ashley needhamParticipant @ashleyneedham69188]

As above, re..Y lead.

I rather think that the 25A unit is being overloaded as either motor runs ok despite the unit being in theory up to the mark.

certainly EVERybody needs a cheap pug-in wattmeter, so easy to use, so quick in diagnosing issues like this.

Ashley

[Jim CrookstonParticipant @jimcrookston25296]

All,

Many thanks for these comments, all of which are noted. I have determined that the start up current was very high and the ESC has tripped. I am now attempting to reset this plug n play example, so far without success. I intend to drive the system on a 6V system next time and while I have used a P94 ESC/Mixer before, I was attempting to replicate the arrangement outlined in the magazine, obviously without success. I think I might revert to the P94 approach from here on.

Jim

[John W EParticipant @johnwe]

Hi jim when you tested your motors; were they in the model and connected to the prop shaft ? if so, try disconnecting the motors and try them free running – it may be that one of you prop shafts is a bit tight and that is what is tripping the speed controller out ,

In a ideal world, if your motor draws say 1 amp free running when you connect it up to the prop shaft it should only draw about 1.5 to 1.75 amps ,but we never really achieve this more like 2 /2.5 amps running with the model out of the water, best of luck



John

[Malcolm FraryParticipant @malcolmfrary95515]

While the combined load of the two motors is getting a bit near the limits of the ESC, the villan of the piece might be the battery. If that can't supply whatever the current is that is being demanded, the resulting volt drop could well shut the ESC down. And "battery" includes all of the wiring until you get into the ESC.

12 volts suggests SLA. While they are capable of very high current briefly (car starter motors generally work) they are rarely good for continuous loads. They were only used before later battery types became available because they were what was available. Under heavy use, they age rapidly.

Putting lower value fuses in the motor feeds could indicate whether they are overloading something in the power train, but be aware that to blow fast, fuses will pass a lot more current than their label states for some time. The easily got ones are not precision instruments. For that, contact breakers are better, but for weight, size and cost, two ESCs probably wins.

When selecting an ESC, the conservative way is to know the motor running requirement, double that, then go for the next ESC up. That moves the bottleneck.

[Jim CrookstonParticipant @jimcrookston25296]

John and Malcolm,

Thanks for your notes (I am learning a lot through this)!!!

I have started again and reverted to an P94 which I have used successfully in the past. I am sticking with the 2 M500 as that was the motor size suggested in an old article in Marine Modelling back in June 2002 which described how the 1/24 scale model of this boat was derived. Hoping all goes well from here on in while I take heed of all the advice offered herein. Many thanks for your continued advice.

Jim

[Dave MilbournParticipant @davemilbourn48782]

Jim

Might I suggest a 5000mAH 7.2v NiMH pack and 30-32mm 3-blade brass props? O – and put the P94 into Mode 4, which is the 50% mix.

Dave M

[Author]

Posts