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Old Mar 13, 2011, 12:03 AM
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Originally Posted by wparsons View Post
If you look at the current draw after ~6 minutes of WOT running, you'll see I'm drawing far below 35a.

700mah in 6 minutes is nowhere near 20a, nevermind 35a.

A 19mm jet drive isn't really a ton of load on a 450 outrunner. I could run it without water cooling at all for river bashing, I only have it so if I'm blasting around at WOT it doesn't get too hot.
where you get 0.7ah on something rated 30+A show me the math.
Last edited by eak; Mar 13, 2011 at 12:14 AM.
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Old Mar 13, 2011, 12:19 AM
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0.7a on a 2.2ah bat you could run for 3hours or something.
Old Mar 13, 2011, 12:35 AM
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Isn't it .7Ah/.1h = 7A?

Today I got ~15 min runtime on my setup and the charger put 2148mAh back into the pack, so 2.148Ah/.25h = 8.6A

That's average amp draw though because I wasn't at WOT the whole time, but even if you triple that you're still only at 25.8A. Though I'll admit I have no idea what a good WOT estimate would be. Double? Triple? 4x the average draw?
Old Mar 13, 2011, 12:58 AM
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regardless of all of this, it seems you've been running the set up with no issues, so you must not be pushing the esc too hard.
Old Mar 13, 2011, 03:33 AM
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regardless of all of this, it seems you've been running the set up with no issues, so you must not be pushing the esc too hard.
Agreed.
Old Mar 13, 2011, 04:04 AM
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hahahah, I so like my toss and run method better then the math I think. JK!
Old Mar 13, 2011, 04:07 AM
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hahahah, I so like my toss and run method better then the math I think. JK!
Also agreed! lol
Old Mar 13, 2011, 10:55 AM
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Quote:
Originally Posted by eak View Post
where you get 0.7ah on something rated 30+A show me the math.
No math, I'm telling you what I saw in a test run yesterday with the new impeller.

I ran it for ~6 minutes, WOT up and down the river and only put 680mah back into the pack to fully charge it. It was in the water for closer to 10 minutes, but the first couple minutes were just drifting in the current and testing the steering.

No math, no voodoo, just raw data from a real run.

This is the motor I'm running:

http://www.hobbyking.com/hobbyking/s...dProduct=11173

It doesn't matter how much current the motor is rated for, it'll only draw as much current as it needs based on the load. A 19mm impeller simply doesn't put a huge load on the motor compared to what it can handle so it runs more efficiently.

I've seen many setups with people running this motor (or similar) on 3s with 32mm props without water cooling and ~40a escs without issue as well.
Old Mar 13, 2011, 11:23 AM
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I was happy with how easy it was to rip everything out of the boat. The servo mount was a bit of a challenge, but over all no real issues excluding the motor. The motor for one was difficult. I wanted to go the route of not removing the jet unit, so i had to work at the motor for a good 30 minutes to get it out. Tried about 50 screw drivers. Found one that worked and now theres a seemingly permanent indent in my thumb.

Will get some pictures up after i do my paint job.
Old Mar 13, 2011, 11:39 AM
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^^ You're braver and more patient than I was, I didn't even bother trying to get the motor off the jet drive with it in the hull!
Old Mar 13, 2011, 11:50 AM
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Quote:
Originally Posted by wparsons View Post
No math, I'm telling you what I saw in a test run yesterday with the new impeller.

I ran it for ~6 minutes, WOT up and down the river and only put 680mah back into the pack to fully charge it. It was in the water for closer to 10 minutes, but the first couple minutes were just drifting in the current and testing the steering.

No math, no voodoo, just raw data from a real run.

This is the motor I'm running:

http://www.hobbyking.com/hobbyking/s...dProduct=11173

It doesn't matter how much current the motor is rated for, it'll only draw as much current as it needs based on the load. A 19mm impeller simply doesn't put a huge load on the motor compared to what it can handle so it runs more efficiently.

I've seen many setups with people running this motor (or similar) on 3s with 32mm props without water cooling and ~40a escs without issue as well.
I'm hungover now. but I figure that is 8.5A or something.
Old Mar 13, 2011, 12:00 PM
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Quote:
Originally Posted by wparsons View Post
^^ You're braver and more patient than I was, I didn't even bother trying to get the motor off the jet drive with it in the hull!
Ya it was a tad frustrating. I will be putting another layer of seal around the jet unit anyway, so not sure why i did it in the first place.

I'm going to craft up a servo mount out of balsa, so i kept the old one to trace the outlines so that i can have it fit the hall nice.

I'm in the middle of brain storming cool paint jobs. Hoping to do something colorful that is easily recognizable.
Old Mar 13, 2011, 05:27 PM
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Originally Posted by eak View Post
I'm hungover now. but I figure that is 8.5A or something.
lol, is it the "That was totally worth it!" type hangover, or the "I'm never drinking Jager Bombs again!" type hangover?
Old Mar 13, 2011, 05:36 PM
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Ya it was a tad frustrating. I will be putting another layer of seal around the jet unit anyway, so not sure why i did it in the first place.

I'm going to craft up a servo mount out of balsa, so i kept the old one to trace the outlines so that i can have it fit the hall nice.

I'm in the middle of brain storming cool paint jobs. Hoping to do something colorful that is easily recognizable.
I shaved all the useless bits off the stock servo ramp and then cut a hole in the deepest part to fit my 9g metal gear servo, and drilled a couple holes for screws to secure the servo. There was also enough room left on the ramp to mount my rx with some velcro.

I found the easiest way to get the stock motor out with the drive in place was to use some needle-nose pliers and a bit from one of those multi-bit screwdrivers. For me it was harder getting the new motor in because I had to enlarge the screw holes and shave some material off the drive to clear the hex bolt heads I used to mount the motor.
Old Mar 13, 2011, 05:56 PM
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lol, is it the "That was totally worth it!" type hangover, or the "I'm never drinking Jager Bombs again!" type hangover?
I will survive.
But 700mah for 6min is a current use of 8.5amps. I cant think of a different way to count it right now. but thats a bit over 2times the unloaded current draw on that motor. sounds ok to me. so you prob be fine with a 35amp esc.


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