Model Boat Mayhem - Forum

Please login or register.

Login with username, password and session length.
Pages: [1]   Go Down

Author Topic: Run Time ?  (Read 2698 times)

DickyD

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 9,497
  • www.srcmbc.org.uk
  • Location: Southampton UK
    • SRCMBC
Run Time ?
« on: August 02, 2007, 05:19:41 PM »

Can one of you gents give me a rough idea of the sort of run time I can expect from my PT15 fitted with:

Mtroniks - Vision 600 Marine Motor
This fan cooled Johnson slip ring motor comes complete with suppresion capacitors.

* Dimensions : L65.0mm, D36.0mm, Shaft diameter 3.0mm

* Voltage, 12V

* Off load current, 1.57A

* Max current, 69A

* RPM, 19800RPM

Using a Tornado TRC4300 9.6v Sub C Nimh battery pack.

Not to complicated please just a rough idea thanks.
Logged
Richard Solent Radio Controlled Model Boat Club http://www.srcmbc.org.uk

dougal99

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,919
  • Huntingdon, Cambs, England
  • Location: Huntingdon, England
Re: Run Time ?
« Reply #1 on: August 02, 2007, 05:56:09 PM »

Dicky

The run time will be dependent upon the current your motor draws running your setup and the capacity of your battery. Thus if your motor draws 4 amps and you have a 2 amp hour battery you will get about 30 minutes. However, if your motor draws 1 amp with the same battery you will get about 2 hours running.

HTH

Doug
Logged
Don't Assume Check

DickyD

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 9,497
  • www.srcmbc.org.uk
  • Location: Southampton UK
    • SRCMBC
Re: Run Time ?
« Reply #2 on: August 02, 2007, 06:03:39 PM »

Hi Doug
The battery is 4300Mah and the maximum current of the motor is 69A. Is that any help ?
Logged
Richard Solent Radio Controlled Model Boat Club http://www.srcmbc.org.uk

J.beazley

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 878
  • The building never ends
  • Location: Locks Heath, Hampshire
Re: Run Time ?
« Reply #3 on: August 02, 2007, 06:10:37 PM »

Richard the only way to tell properly is to get her WET and time how long she runs for (just make sure someone is about to push you in)

Jay
should look lovely on the water too
Logged
If it floats I'll  build it, if it sinks its a sub either way its in the water so I'm content.

Stavros

  • Guest
Re: Run Time ?
« Reply #4 on: August 02, 2007, 06:49:16 PM »

Alspo dependant on your right foot so to speack Stavros
Logged

dougal99

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,919
  • Huntingdon, Cambs, England
  • Location: Huntingdon, England
Re: Run Time ?
« Reply #5 on: August 02, 2007, 07:00:04 PM »

Dicky,

The max current figure is probably the stall current, that is the current the motor draws when prevented from turning. That should be considerably more than when running free. A 4.3 Ah battery could only supply 69 Amps for about 3 minutes (always assuming it could give 69 Amps in the first place)

Whilst Jay is right, you can get an idea about the running current by putting a ammeter in the circuit and running the boat in the domestic test tank. (Ensure it doesn't fly over the taps.) As the boat will be restrained the reading you get should be a little above the free running figure. Of course Stavros is also right, running flat out will give you a shorter time than just cruising about.

HTH

Doug
Logged
Don't Assume Check

DickyD

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 9,497
  • www.srcmbc.org.uk
  • Location: Southampton UK
    • SRCMBC
Re: Run Time ?
« Reply #6 on: August 02, 2007, 08:02:38 PM »

Thanks all, suck it and see then.

Its a PT boat Stavros. Heavy right foot. ;D
Logged
Richard Solent Radio Controlled Model Boat Club http://www.srcmbc.org.uk

Robert Davies

  • Guest
Re: Run Time ?
« Reply #7 on: August 02, 2007, 09:37:24 PM »


Dicky, at full whack, my guesstimate would be c20mins as a minimum - if you can stay off the loud pedal, anything up to 1.5hrs....

Speed eh? Wonderful thing ;)

-Rob
Logged

Ghost in the shell

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,707
  • Go Nuclear! you'll love it
Re: Run Time ?
« Reply #8 on: August 02, 2007, 10:50:43 PM »

my najade rob, i think you see that one, (silver thingie) will hare  around the lake for about 15 mins before the 2x 3300mah batteries decide to play no more!

my neppie and sydney star will sail all day
Logged
"xxxxx" the tree huggers, GO NUCLEAR

Ghost in the shell

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,707
  • Go Nuclear! you'll love it
Re: Run Time ?
« Reply #9 on: August 08, 2007, 08:06:49 PM »

Dicky,

The max current figure is probably the stall current, that is the current the motor draws when prevented from turning. That should be considerably more than when running free. A 4.3 Ah battery could only supply 69 Amps for about 3 minutes (always assuming it could give 69 Amps in the first place)

Whilst Jay is right, you can get an idea about the running current by putting a ammeter in the circuit and running the boat in the domestic test tank. (Ensure it doesn't fly over the taps.) As the boat will be restrained the reading you get should be a little above the free running figure. Of course Stavros is also right, running flat out will give you a shorter time than just cruising about.

HTH

Doug

what you will get from wioth that is a sudden peak or two as the boat emptied the water from under it and suddenly the prop finding itself in air at MAX rpm, then the water will slosh back under the boat, adding load again to the motor.
Logged
"xxxxx" the tree huggers, GO NUCLEAR

DickyD

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 9,497
  • www.srcmbc.org.uk
  • Location: Southampton UK
    • SRCMBC
Re: Run Time ?
« Reply #10 on: August 08, 2007, 09:21:27 PM »

I actually got about 35mins running before nipper disposed of the superstructure. :'(
Logged
Richard Solent Radio Controlled Model Boat Club http://www.srcmbc.org.uk

dougal99

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,919
  • Huntingdon, Cambs, England
  • Location: Huntingdon, England
Re: Run Time ?
« Reply #11 on: August 08, 2007, 09:22:52 PM »

Ghost

Ref your last post. I assume 'wioth' is a typo for with. I have never experienced what you describe. Getting the water out from under a boat in a tank/bath would take some power and pretty slow moving water  ;D

Doug
Logged
Don't Assume Check

justboatonic

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 1,365
  • Location: Thornton Cleveleys
Re: Run Time ?
« Reply #12 on: August 08, 2007, 10:26:02 PM »

A 4300mah battery pack on full chat ALL the time running a 19k rpm motor will last around 10 minutes.
Logged

Ghost in the shell

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,707
  • Go Nuclear! you'll love it
Re: Run Time ?
« Reply #13 on: August 09, 2007, 10:39:27 PM »

Ghost

Ref your last post. I assume 'wioth' is a typo for with. I have never experienced what you describe. Getting the water out from under a boat in a tank/bath would take some power and pretty slow moving water  ;D

Doug

dougal, when I tested the najade under power, rather than have the boat empty the bath I only put about 6" of water in the bath, the prop spun that fast that she ended up cavitating for a second as the boat had a void under the prop for a second or two, you should have heard the motor gain RPM then suddenly get loaded again
Logged
"xxxxx" the tree huggers, GO NUCLEAR

dougal99

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,919
  • Huntingdon, Cambs, England
  • Location: Huntingdon, England
Re: Run Time ?
« Reply #14 on: August 10, 2007, 12:22:10 PM »

Hi Ghost

After I posted my entry I thought on and surmised you might have been running in a shallowish (is that a word?) tank/bath.

Moral: get a high sided bath/tank.  ;D

Cheers

Doug
Logged
Don't Assume Check

dreadnought72

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 1,871
  • Wood butcher with ten thumbs
  • Location: Airdrie, Scotland
Re: Run Time ?
« Reply #15 on: August 10, 2007, 01:38:08 PM »

A 4.3 Ah battery could only supply 69 Amps for about 3 minutes (always assuming it could give 69 Amps in the first place)
Oh - I'm sure the battery would give its best attempt at providing 69 amps! Of course, most of those three minutes would be smokey, flame-ridden and very, very hot! ;-)

Andy
Logged
Enjoying every minute sailing W9465 Mertensia

R2-D2

  • Guest
Re: Run Time ?
« Reply #16 on: August 10, 2007, 02:37:41 PM »

Model cars do it in five min and some go flat before the end of the five min race.

Luke
Logged

Ghost in the shell

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,707
  • Go Nuclear! you'll love it
Re: Run Time ?
« Reply #17 on: August 10, 2007, 06:02:30 PM »

Model cars do it in five min and some go flat before the end of the five min race.

Luke

thats the case with the fast electric boat races running a 54- motor and 2000mah ni-cads on 7.2v, go like stink to start with and by the end of the race, they're crawling along,
Hi Ghost

After I posted my entry I thought on and surmised you might have been running in a shallowish (is that a word?) tank/bath.

Moral: get a high sided bath/tank.  ;D

Cheers

Doug

yeah pretty shallow, if i had loaded the bath up to a level where the boat didnt remove all the water from under it, the blast from the prop would more than likely be on the bathroom floor, as even in that shallow water, the wash was hitting the back of the bath and going up the bath sides a good 12"
Logged
"xxxxx" the tree huggers, GO NUCLEAR
Pages: [1]   Go Up