What Size Fuse Should I Use?

[bill rogers]

I'm running a D&E 3" WTC with a Speed 400 motor and a HiTec EZX-r ESC. The ESC is rated at 65A max, 46A continous. I don't know the Amp rating for the Speed 400 motor. What size fuse should I use? Also, how many turns does the Speed 400 motor have?

Bill Rogers

[robse]

Hi http://www.subcommittee.com/forum/icon_smile.gif
To be honest, I

Hi
To be honest, I would not place a fuse between the motor and the speed regulator.

First; a motor going from stand still to say... full RPM spikes at an unbelieveble Amp, so even if you put a high amp, slow blow fuse, it still might not be optimal.
Why: Let's say you put in a 20amp slow blow fuse. That'll allow some spiking, but is it enough to prevent the motor from running hot if something get's cought in the prop, acting as a hanging brake for a while?
That'll allow the motor to overheat without the fuse blowing. See my point? Fuse large enough to handle spikes will not offer much protection anyway.

Second: I'd rather risk blowing my speed regulator, and still have the emergency option to give full ahead, if I'm stuck. The alternative will blow the fuse, save the regulator, but sink the sub.

[bill rogers]

Thanks Rob, this is an

Thanks Rob, this is an interesting way to look at the question. I've gone through three ESC's and trying to figure out my next step.

Does anyone know how many turns a Graupner Speed 400 motor have?

Bill Rogers

[robse]

You are welcome, Bill. http://www.subcommittee.com/forum/icon_smile.gif
My

You are welcome, Bill.
My regulator 'required' a capasitor right on it's poles, and I believe some uses noise reducing capacitors on the engine it self. Have you checked this option?

Second: Are you sure that you do not have a heat problem rather than a over-amp problem?

[bill rogers]

Hi Rob, thanks again.

I have

Hi Rob, thanks again.

I have capacitors on my motor but not the ESC. The ESC ran fine all last summer. I was running a new build for the first time this summer when after about two minutes the boat went dead in the water. The new boat is about 12 percent heavier than my original boat. After disassembly I tested: (1) current draw on the motor and gearbox without the ESC, (2) motor and gearbox connected to the shaft and prop. Finally, I tested (3) a spare identical motor without gearbox. Results were 1.6 amps; 1.8 amps; and 0.4 amps respectively. After all that I tried reprogramming the ESC several times but each time it failed to work.

So, I have ordered a new ESC from Mike's Subworks.

Bill Rogers