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Author Topic: Advice from Fast Electric Experts requested  (Read 5591 times)

Tim_M

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Advice from Fast Electric Experts requested
« on: September 14, 2014, 04:32:26 PM »

I'm starting work on a new design hydro as a follow-on from my Bluebird project. I want to pick your brains!

I have a Feigao 5408407XL (a Chinese 'Hacker' copy). Quite old but new - it's been in storage for over ten years!
I read somewhere that you can push the shaft through some motors so the drive comes out of the same end as the wires. Is this true? Is it that simple? Anybody done it on one of these motors? (This arrangement might fit better in my layout).

Second, I have a Castle Creations Barracuda 80A controller (similar vintage). It's running almighty hot (but the motor is not). Hot enough to de-solder the wires! I want to upgrade to a higher capacity. The motor limit is 90A; I assume there's no harm in over-specifying the controller (other than cost)? There are some very good looking, very expensive units out there but  Hobby King have some budget jobs, in particular the  Turnigy AquaStar 120A Water Cooled, Turnigy AquaStar 160A Water Cooled,   HobbyKing Red Brick 200A and Birdie 190A Brushless. Anybody have experience of these cheap units? The reviews are mixed but of course people complain more often than they praise. I don't want to break the bank but neither do I want to invest in rubbish.

This newbie would appreciate your comments!
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slowcoach

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Re: Advice from Fast Electric Experts requested
« Reply #1 on: September 15, 2014, 03:35:52 PM »

Hi
I'm no expert but this is how to take motor to pieces to replace bearings but from this you can try to reverse the stator.
http://www.offshoreelectrics.com/info-pages/how-to-replace-feigao-bearing.php

Is the motor under any load when you are testing the ESC with this motor, if not there is problem with one or the other.

The Turnigy Aquastar 160A is a good choice but watch your prop sizing with these motors they also need good water cooling otherwise the glue on the end cover melts with the ruin of one motor.
Hope this helps to start I'm sure some FE fan will throw more light on the subject soon.
Lionel
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Tim_M

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Re: Advice from Fast Electric Experts requested
« Reply #2 on: September 15, 2014, 05:59:09 PM »

Thanks Lionel. Looks pretty straightforward, if I don't wreck the rear bearing pushing the cap off. The only other problem I have is that the shaft adaptor is on there rock solid. I can't move it for love nor money. Good thing, in a way. I'll keep this post in mind if I need to reverse the motor.

The motor was under load when things got hot - running the boat.

Thanks for the advice on ESCs!
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Tombsy

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Re: Advice from Fast Electric Experts requested
« Reply #3 on: September 18, 2014, 05:49:20 PM »

What battery voltage are you using 3s, 4s? The Fiagio (2382kv) is 34,000 rpm on 4s which could work, I haven't used the Aquastar but the Turnigy Marine 120A is a really solid esc that I use on 4s with 2030kv motors with no problem.
I've been adding a couple extra capacitors to them, it helps reduce the size of the voltage ripple and seems a little more forgiving if you use to big a prop.
Watch your prop size if you are overheating the esc, also run your watercooling to the esc first then the motor, seperate water pick-ups are even better.
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Tim_M

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Re: Advice from Fast Electric Experts requested
« Reply #4 on: September 18, 2014, 08:43:47 PM »

Thanks Brian. I've just ordered the Aquastar 160, having broken my ESC trying to tidy up the soldering. Castle Creations have since told me it's impossible to work on their boards with normal tools as they use ultra-high temperature solder and thick heat planes. They're not wrong!

I'll keep a note of your advice!
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pompebled

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Re: Advice from Fast Electric Experts requested
« Reply #5 on: October 08, 2014, 05:26:43 PM »

I read somewhere that you can push the shaft through some motors so the drive comes out of the same end as the wires. Is this true?
Hi Tim,

In motors like yours, the magnetic rotor is glued onto the shaft, the only way to get it loose, is to heat up the rotor (preferably when outside the motorcan) to the point where the glue breaks down and the shaft will move.
The problem with this, is that you don't want to overheat the rotor, or the magnets will demagnetize, making it a paperweight.
Knowing how far you can go is tricky...

If turning the rotor around, as described, will do the trick for you, that's a much healtier solution.

Second, I have a Castle Creations Barracuda 80A controller (similar vintage). It's running almighty hot (but the motor is not). Hot enough to de-solder the wires! I want to upgrade to a higher capacity. The motor limit is 90A; I assume there's no harm in over-specifying the controller (other than cost)?

Your Feigao is a two pole motor with a healthy ampdraw, a 80A ESC will only work, if the ESC is watercooled, the propsize isn't too big and you run the combo 80% of the runtime full throttle.

Running that motor at partial throttle will heat up the ESC to no end (as you've discovered).
A bigger ESC, like the T-120 provides more headroom.
Keep in mind, the 90A mentioned is the continuous current the motor will handle without overheating, but getting out of the hole and accelerating out of a turn can easily draw spikes twice as high.
Your ESC must be able to handle that.

I started with two pole motors and switched to fourpole (or more; outrunners) some years ago and never looked back, much more torque and less heat build up (when watercooled of course).

Regards, Jan.
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Tim_M

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Re: Advice from Fast Electric Experts requested
« Reply #6 on: October 08, 2014, 07:27:25 PM »

Thanks for all the advice here. On balance, I think I will live with slightly ugly wiring rather than risk damaging the motor just to get things looking neat!

I have my new ESC (Aquastar 160) but I'm still waiting for instructions from HK on how to use it. I can't understand the Chinglish instructions they provide on line!
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pompebled

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Re: Advice from Fast Electric Experts requested
« Reply #7 on: October 08, 2014, 08:06:29 PM »

Hi Tim,

What is it you don't understand?

You purchased an ESC which comes from a car background, this is reflected in the software and the terminology used...
If you have the prog box, it's fairly easy to set up the ESC for use in a boat.

If 'acceleration' is another word for softstart (which would make sense in a car, to keep the gears in one piece), I miss the option to set the timing.
If there is indeed no way to set the timing manually, hope it's an automatic function, which works well, or the ESC may have difficulties running some types of motors.

Personally, I steer clear of ESC's with a car pedigree for use in boats which come with foggy software...
For use on 4S, the T-120 is one of my favourite ESC's, simple to set-up and very reliable:
http://www.hobbyking.com/hobbyking/store/__8946__Turnigy_Marine_120A_Brushless_Boat_ESC.html

Regards, Jan.
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Tim_M

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Re: Advice from Fast Electric Experts requested
« Reply #8 on: October 09, 2014, 08:38:46 AM »

Hi Jan,
It's right back to basics, really.

The programming box has two sockets. One has is labelled -, +, - and the other has a symbol like a square wave, (which I assume is 'signal'), +, -.
I have worked out that the lead from the ESC plugs into the signal, +, - socket because it won't fit in the other one.
There is nothing to tell me what plugs in the other socket (if anything), whether I connect the main LiPo to the ESC or whether I connect the motor for programming.

Once I get past the programming stage (and all I want to do there is turn off the reverse function) I assume I have to calibrate the throttle using my Tx. On my Barracuda, the drill was:
Turn on the Tx and set full throttle. Then plug in the ESC. The motor gives out some bleeps and the led flashes. Go to full reverse. More bleeps. Go to neutral. More bleeps and the unit is ready to run. The instructions for the Aquastar unit (on line) are very unclear, it just says 'calibrate the throttle'). After this routine, the sequence for normal use is:
Turn on the Tx and set to neutral. Plug in the ESC and wait for a bleep then you're good to go.

I'm a little nervous about putting electricity anywhere near this thing until I know what I'm doing. Get it wrong and a couple of hundred amps is going to go in the wrong direction and fry it!

I gathered that the ESC has a car background from some of the write ups but as I'm only interested in straight line short runs (rather than racing) I think it will suffice - I'm not serious about performance.

You are probably thinking 'does this guy know NOTHING about ESCs?' and you would be right! {-)
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slowcoach

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Re: Advice from Fast Electric Experts requested
« Reply #9 on: October 09, 2014, 10:24:02 AM »

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pompebled

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Re: Advice from Fast Electric Experts requested
« Reply #10 on: October 09, 2014, 11:33:59 AM »

Hi Tim,

The other socket is used to power the prog box with 5V power,  from a seperate battery, using a UBEC to reduce the Voltage to the prog box.
Another possibility is to connect the drive battery to the ESC and let the internal BEC power the prog box, just see which way works.

Regards, Jan.

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Tim_M

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Re: Advice from Fast Electric Experts requested
« Reply #11 on: October 09, 2014, 12:08:05 PM »

If you understand the manual, you're a better man than me, Lionel {-)
Thanks Jan, you confirmed what I was thinking.

Finally heard from HK. Plug the esc into the 'signal' socket on the box, plug in the LiPo and go from there.
For calibration, switch on the ESC first then the Tx. Not sure I trust that one but......

I'll give it a go at the weekend. If you see a puff of smoke off the south coast, that'll be me. :-))
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Tim_M

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Re: Advice from Fast Electric Experts requested
« Reply #12 on: October 10, 2014, 06:31:43 PM »

 :-)) We have rotation. (more in my Bluebird post)
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slowcoach

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Re: Advice from Fast Electric Experts requested
« Reply #13 on: October 11, 2014, 01:12:47 PM »

Well done Tim
Could you possibly do a write up just in case I decide to take the plunge
Lionel
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Tim_M

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Re: Advice from Fast Electric Experts requested
« Reply #14 on: October 11, 2014, 06:58:42 PM »

OK, I have NOT suddenly become an expert on ESC's, but in response to Lionel's request, here is a write up of what I did to get the motor running.

I purchased a Turnigy Aquastar 160 and programming box from Hobby King. I bought the box because I have a real problem hearing the 'bleeps', let alone keeping up with a programming sequence. The items came without proper instructions but over a few days I was able to glean enough information to take the plunge and connect everything up.

The programming box has two three pin sockets. One is labelled with a 'top hat'/square wave, -, +. The other is labelled -,+,-.
The second socket is to allow the ESC to be programmed without plugging in the LiPo.

I plugged in the motor, plugged the ESC into the box (the socket with the top hat) and connected the LiPo (at arm's length {-)). I turned on the ESC and the box display came to life. There are four buttons on the box. Up and down move you through the programming sequence, left and right select the option you want for each stage of the sequence. It turned out to be a doddle. I only wanted to turn off the reverse so I just stepped down till I found that option and selected 'no reverse'. I then carried on stepping down until I reached the final question which was simply 'Defaults?'. I answered 'no' and that saved my changes.

I disconnected the LiPo and the box then plugged in the Rx. Now, I'm not sure if this is the right thing to do (however, I am still here to tell the tale) but I followed the routine for my old ESC:
Tx on, full throttle.
Turn on the ESC and wait.
Go to full reverse (I am using and stick style Tx so that meant using the trim to go beyond 0). Wait.
Go to neutral. Wait
(I didn't hear any bleeps during this process, but I can't hear bleeps anyway).
Turn off the ESC then Tx.
Turn the Tx back on, throttle neutral.
Turn the ESC on and wait for a couple of beeps.
That's it - push the stick up gently and we are away.

I think all this may have been unnecessary and the ESC may just auto-calibrate but whatever, it didn't blow up or spin the motor unexpectedly.

I've yet to see how this unit performs on the water. I've read a few horror stories of them blowing up as soon as they are plugged in but have no idea how many do not blow up. I also read some complaints about the units not being waterproof. Mmm. I understand this was originally a car ESC and the only real difference is that the finned, fan cooled heat sink has been replaced by a water cooled block. I took the precaution of removing the water connections and adding a good sealant. They had plastic washers but they weren't very tight. Really, that is the only place the unit could leak. The water doesn't go anywhere near the circuit board.

Overall, the unit is well-presented. If the internals are as good as the externals, then it's a good unit for the price. I did notice during a bench test with the prop attached that the motor is running MUCH smoother on this unit. It sounded pretty rough before with no load on the prop. Either I got the prop tube greased better or the ESC is better (it is, after all, fourteen years newer in technology!) It does bring the motor to an abrupt stop if you slam the throttle shut. Probably a 'car' feature. Might have to see if there is an option to tame that but in the meantime, gently does it when closing the throttle the last little bit.

If that lot makes no more sense than the manual, let me know and I'll try again!
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slowcoach

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Re: Advice from Fast Electric Experts requested
« Reply #15 on: October 12, 2014, 06:46:00 PM »

Hi Tim
Thanks will file for later reference.
Lionel
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Tim_M

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Re: Advice from Fast Electric Experts requested
« Reply #16 on: October 14, 2014, 05:32:56 PM »

More technical questions.......

I am looking at the design of my next boat and considering where to put things. I would like to physically separate the motor and battery to spread the weight - increase the moment of inertia  - to make the boat more stable in pitch and yaw. It would look 'heavier' on the water. (Quite the opposite to what racers want to do; concentrating all the mass near the centre of gravity makes the boat - or an aircraft - much more responsive to the controls).

Anyway, if I go down that route, I will need to extend the wiring. I know that you have to use good quality, heavy wires to minimise the volt drop at high currents. I am just wondering about the effect of lengthening the wires between the ESC and the motor. As I understand it, the motor current is switched at 16 kHz. That's not a very high frequency (within the audible range - for a child  ok2) but I believe the pulses are square waves so that needs a much  higher bandwidth.

Would I get any strange effects if I used 350 - 400 mm good cables between the ESC and the motor? Are there any problems (apart from resistance) in using long cables between the battery and the ESC?

This goes back to my first query about reversing the layout of the motor so that the wires came out the same end as the shaft. With heavy wires, you need 150mm or more to make a loop back over the motor if the ESC is at the shaft end.

Nothing is decided yet, just exploring the possibilities  :}
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Re: Advice from Fast Electric Experts requested
« Reply #17 on: October 14, 2014, 07:37:14 PM »

More technical questions.......

I am looking at the design of my next boat and considering where to put things. I would like to physically separate the motor and battery to spread the weight - increase the moment of inertia  - to make the boat more stable in pitch and yaw. It would look 'heavier' on the water. (Quite the opposite to what racers want to do; concentrating all the mass near the centre of gravity makes the boat - or an aircraft - much more responsive to the controls).

Anyway, if I go down that route, I will need to extend the wiring. I know that you have to use good quality, heavy wires to minimise the volt drop at high currents. I am just wondering about the effect of lengthening the wires between the ESC and the motor. As I understand it, the motor current is switched at 16 kHz. That's not a very high frequency (within the audible range - for a child  ok2 ) but I believe the pulses are square waves so that needs a much  higher bandwidth.

Would I get any strange effects if I used 350 - 400 mm good cables between the ESC and the motor? Are there any problems (apart from resistance) in using long cables between the battery and the ESC?

This goes back to my first query about reversing the layout of the motor so that the wires came out the same end as the shaft. With heavy wires, you need 150mm or more to make a loop back over the motor if the ESC is at the shaft end.

Nothing is decided yet, just exploring the possibilities  :}

Tim,
I am no expert on power loss thro' long cables with E.S,C. and Lipo's but on my K7 I have long extensions and  harness to the Lipo's joining them in parallel with no apparent problem over the last 2 years and with the 3s Lipo's the boat is fast enough.
Pic of the cable set up, hope this helps.
 
George
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pompebled

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Re: Advice from Fast Electric Experts requested
« Reply #18 on: October 14, 2014, 09:42:43 PM »

Hi Tim,

If you must extend the leads, try to keep the wiring between the battery and the ESC under 8".
If you go longer, you need to add caps to the ESC to keep things running.
Don't overdo it, as too long leads will kill your ESC

The leads between ESC and motor can be extended up to a point where the extra length starts to compromise the correct commuting of the motor.

I've gone as long as 20 cm between the ESC and the motor connectors, making the total distance between ESC and motor about 10", at this length, the motor still runs well.

Rig a test setup and see if 350 - 400 mm will cause problems for the ESC (and motor).

Regards, Jan.
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Tim_M

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Re: Advice from Fast Electric Experts requested
« Reply #19 on: October 15, 2014, 07:58:42 AM »

Thanks for the replies, chaps. It's amazing how much information can be gleaned on this forum - and from those who know!
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Re: Advice from Fast Electric Experts requested
« Reply #20 on: October 17, 2014, 08:37:38 PM »

Tim,
Reference Jans post on the length of the power cables from the E.S.C. and the battery's.
I have just checked the length of mine and they are 500 mm from the E.S.C. to the battery's.

I have been running my boat since 2011 and never have had a minute of trouble with the E.S.C.
The batterys that I use are TURNIGY  soft packs  3s x 22000 in parallel and I am now on my second set as the originals were beginning to swell on the casings so I changed to new ones.

Maybe I have just been lucky with no trouble so I shall just push on as before.

George.
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