73,000 RPMs!!!

[Meniscus]

OK, we weren't thinking at the pond!

The No Step 1 has a 7s 540 size Feigao in it. Here's what we didn't think about:

The motor is 5070kv. I shoved two fully charged 6-cell Nimh, Intellect 3800's,in the hull. I think you know where I'm going here.

They were in series!!!

5070kv times 14.4v = 73,008rpm!!!

Can you believe it!!! Only cooked one cell on one of the Nimh packs. Thing is, the ESC didn't get hot and motor was warm. I guess I should have checked the temp on the driveline!!!

It handled the first run, no problem. Second run, slowed a little when the batteries seemed to die. That's when we opened up to find the one cell bulged.

I'm thinking it's a good thing we could only come up with the smaller prop at the pond! LMAO. Good thing I decided not to put the lipos in after the first run! Can you imagine how many amps the CC Barracuda 80 saw?!?!

So, this goes down in the books as one of the funniest/stupidest things I've done! And the electronics made it! No harm, no foul, just need to replace a cell in one of the Nimh packs.

Tell me that is hilarious!!!! We really should have put the GPS in it for this stupidity! Or at least hook up an EagleTree!!!!

A special thanks to Egneg for the excellent balancing job on that prop!

[Meniscus]

At least now I can say I did it and scough at those running 45,000 RPMs!

[Rex R]

you might want to 'keep an eye' on those motor bearings. the stock bearings are only rated to 50k

[Meniscus]

you might want to 'keep an eye' on those motor bearings. the stock bearings are only rated to 50k

That's not the only thing I'm going to keep an eye on! I'm thinking I may need to replace the teflon tube LOL, but I haven't checked yet.

[Jeff Wohlt]

What prop were you running? You may not have been pulling that many amps if you had some tiny prop on it but I bet she sounded like a singer sewing machine on steroids!

[calcagno45]

What prop were you running? You may not have been pulling that many amps if you had some tiny prop on it but I bet she sounded like a singer sewing machine on steroids!

I would have loved to hear that motor revving as well!!!

[egneg]

What prop were you running? You may not have been pulling that many amps if you had some tiny prop on it but I bet she sounded like a singer sewing machine on steroids!

I believe it was a modified X637.

[Jeff Wohlt]

Well that would have to be a first for a Fiego motor and not come apart...you were lucky. You had enough load to not destroy it from RPM and not enough to just hit that ESC with 150 amps and poof.

Do it again and video it :)

[Fluid]

Don't be fooled by raw numbers, they have to be interpreted. The motor saw nowhere near 73,000 rpm. The weak links were the cells - under very heavy load they would be lucky to deliver 0.9 volts per cell, or under 11 volts total. And the listed Kv is not at high amp draw anyway, so at 200 amps (to choose a number) the efficiency and the Kv would be lower.

With high-draw BL systems it was usual for the nickel cells to fail first. The lower quality cells with high internal resistance will have a large voltage drop and heat up quickly. It is no surprise that you lost a cell. The first run probably did enough damage to increase resistance even more.

I would keep a close eye on the ESC, damage is likely. That kind of damage is cummulative, so don't be surprised to have the ESC fail in the next few weeks. Or not - I hope you are lucky.



.

[Meniscus]

I knew I could count on you Jay for some grim truth. LOL

I know there's no way it saw that many RPMs. Just had to share the recklessness!!!

LMAO

[ozzie-crawl]

awhile back a mate of mine brought what he thought was a fairly low kv motor to run on 6s, problem was he couldnt keep it in the water,found out later on the motor was a 4200kv (thats 93240 rpm) any way here is a video of its first test run http://www.youtube.com/watch?v=XIpi0TXyiVw

[Ub Hauled]

I've seen this video, how's the motor?

[Doug Smock]

I've seen this video, how's the motor?

LOL no kidding, and if you listen carefully you can hear the ESC scream.

[ozzie-crawl]

in that video it doesnt get past about half throttle,later on with battery placement change it ran fairly well, the motor lasted about 4 months before it died (far longer than we expected) it ran a 100 amp speedie at the end of a 5 minute run motor and speedie never got much above 40c

[Meniscus]

Well, after a couple runs, no issues with the Barracuda 80 ESC and there's no play in the motor bearing either. I consider myself VERY, VERY lucky!

I'm going to run it again today with a larger prop since I've seen that the hull can handle the faster speed. I guess now I'm spoiled after seeing it skip across the water!