Scorpion 2221-8 motor w/ 35A ESC?

[JEB123]

I just accidentally ordered a 35A speed controller w/ a Scorpion HK2221-8 motor which has a max draw of 45A. I'm an electronics tech:oops:, so I realize the speed controller should be capable of delivering what the motor requires under maximum load. I just wasn't paying attention to what I ordered (too excited). It will be in a scale Hughes 500 fiberglass fuse adding weight to a TRex 450SE V2. Should I have a problem since it won't be used for 3D and won't see many spikes? Will I ever come close to drawing that kind of current? I spoke to the vendor and they will swap it. Should I send it back and get the 45A ESC (which is still too small)?

[HFG]

Just gear the system so the motor never tries to pull over 35A continuously.

[huskynox]

I did the exact opposite as you, I bought the Scorpion 45 amp for my BEAM, but it's a little too large for that heli, so I bought a 35 amp Align for the -8 Scorpion motor. Lot's of guys run it on the -8. Heck, a lot of guys run it on the -6!

I'll trade you your Align for the Scorpion if you want? I would rather have a spare Align ESC. You have more room with your scale fuse to install the Scorpion... It's about an inch longer than the Align, but about half as thick too!

[HFG]

This is the JAZZ 40, Scorpion 55A and CC35

http://i79.photobucket.com/albums/j159/hfguy/DSC00888.jpg?t=1208556138

[JEB123]

Hi guys, HFG, I think I see what you mean, but I'm a newb to helis, how is that done, by gearing up to reduce headspeed? Go to maybe a 15t or 17t on the motor?
Huskynox, sorry, but I bought this bird w/ no electronics, I don't have an Align ESC.

[HFG]

Not familiar with the -8 I have a -6 but its waiting for a heli to be mated with. Start with a 2800-3000 HS and figure out your current draw, and up it as required. Currently iam running a NEU motor and fly 3D (luke warm to mild 3D :) ) Heres some data from a few flights ago.

http://i79.photobucket.com/albums/j159/hfguy/capi1.jpg?t=1208557045

[JEB123]

Not too clear on your graph, but I see you mean lower RPM's means less draw, but what about rotor loading? Doesn't that affect current draw regardless of RPM's? Are those green peaks your max loading? If so, looks like you barely reach 35A, right?

[HFG]

Green is HS and purple is current. Even with hard flying you dont draw alot of amps continuously. I've got one peak of almost 50A. Its all about gearing, the more torque the motor requires the more current it will draw.

If you wanna know more you can read my Brushless 101
http://helifreak.com/showthread.php?t=64727

[JEB123]

Thanks, I'll read it. In short, do you think I'll damage the ESC doing slow scale flying?

[HFG]

If setup properly no. Pretty much ALL of the motors used on a 450 are able to draw more current than the esc can provide, not sure why only scorpion motor get the attention.

[JEB123]

In my case because I screwed up ordering the ESC! I'm sure most of this stuff is engineered with plenty of safety margin designed in, but I always like to play it safe and not push the tolerances. Thanks for all the advice, all the people on this forum are great!!!!

[Jetleaf]

I am running a -8 motor and 35 amp commander on my Beam with a 14 tooth pinion. After 4 1/2 minute flight, motor, batt, esc are just warm. No hard 3d. Oh and I am putting back right at 1300 mah in a 2200 pack.

[JEB123]

Hi Jetleaf, thanks for the reply, that's good to know, in that case I'll keep it! 1300? isn't the rule of thumb 80%, or 1760 for a 2200mAh battery? The motor draw is dependent on the load, not the supply, so that should only extend your battery life. I'm still a little confused about the pinion, for example, from 14T to 15T will decrease head rpm, right (heli newb, remember!)? BTW, what's a Beam? I know, duh...

[HFG]

NO, higher pinion will increase the HS.

(Motor RPM X Pinion teeth)/ Main gear teeth = Headspeed

[JEB123]

Sorry for all the dumb questions, sounds like heli 101. A new formula to me, however!. I'm learnin' thanks to you guys!
Jorge

[strat1960s]

I too have the Scorpion HK 2221-8 motor on my heli. I was running the stock 35 amp BEC/ESC on my heli. I was just hovering around inside my shop when the signal was lost or locked out. Everything checked out fine, but the BEC/ESC was getting very hot. The only thing we could come up with was that the BEC/ESC got too hot and somehow the voltage to the reciever got too low and that caused the signal lock out. Well, the heli took off down the middle of my shop before crashing under my tool box. It was only about $10 worth of damage, but it scared the crap out of me. I was only on my second lipo pack that morning. I had been flying 3 lipo packs (back to back) in the morning and 3 more in the afternoon.
Any how, Everyone told me to get the 35 amp Common Sense BEC/ESC, so I did. The BEC/ESC kept getting very hot so I researched the motor and found out it was a 45 amp motor. I ordered the Scorpion Commander 45 Amp BEC and everything is great. Not one lockout in 30+ flights.
So if anyone out there wants a 35 amp Commons Sense BEC/ESC with the programing card let me know. I don't need it, but I'm not just going to throw it out either.
Ted

[JEB123]

Thanks Ted, you sold me, I'm swapping it for a 45 amp.

[HFG]

** shakes head **

[JEB123]

Well, still not so convinced, you shouldn't draw nearly 35 amps just hovering...I think you would have lost power to the motor before you lost power to the receiver. That's what a BEC is for. Do you have ferrite on your cabling for noise reduction?

[HFG]

Should only be drawing about 15A hovering with any motor on the 450.

[JEB123]

Unless it's turning 5K RPM!

[HFG]

No one runs that much HS on a 450.

[strat1960s]

Jeb,

I like running my Air Thunders down pretty low. The only thing we could come up with is that the BEC/ESC wasn't able to keep the voltage going to the RX. Now that I think about it, the lipo was just charged up the night before and I was only a minute or two into the hover when it took off on me. Bottom line is that it hasn't happened again. I credit that to the new 45 Amp commander.

Ted

[JEB123]

That was a joke HFG.

[HFG]

JEB you would be surprised the comments and questions i get on this forum.