Electric Revo Feigao 9L Overheats???

[jhautz]

I bought a Feigao 9L and Warrior 9920 combo used(ebay) and I keep overheating the motor in my electric revo conversion. Then the esc starts to heat up to the point that I loose the brakes. Then I shut it down then before it completely thermals. Let it cool and all is fine again for 5 min or so. I'm running the revo on a emaxx tranny and started off running in 2nd gear only using stock emaxx gearing 66/18 and a 8000Mah 5s Lipo. After the first overheat, I dropped down to 66/16 and still overheated. Then I started running in 1st gear only and still overheated. Then I went to only a 3s Lipo and it still overheated. Not sure if I have a bad motor or bad esc or the motor is just not enough for this setup. I see in a lot of other threads that people run this setup in emaxx's all the time. I wouldn't think the revo would be that much different. :confused:

I checked everything else out, no binding in the drivetrain and it all runs really smooth. Before the thing overheats its a freakin missle. I can be clipping allong at 1/2 throttle and still pull wheelies when I punch it. The system is amazngly powerfull untill it gets too hot.

I saw in a another thread that the 9L is commonly used for emaxx's, but for revos the XL's are the more common choice. Why?

I know I'm missing something. Should I be looking at a XL size motor or maybe the 540C 9L with the cooling fins on it. Any advice would be apreciated. Ikow there are alot of you out there with a ton of brushless expeience.

[crazyjr]

First off welcome to the forums. Is the esc getting hot as well or just the motor? Also, how hot are the batteries? The reason for the XL over the L is a bigger motor with less rpm for more torque and higher voltage handling, also easier for the esc to handle and less sensitive to gearing. These motors are not limited to Revo's

[jhautz]

The ESC is getting hot as well. Not as hot as the motor, but hot enough that I cant hold my finger on it for 5 secs. This is when the brake stops working and I shut it down before I fry the whole thing.

Batteries are not even slightly warm. They are 12C constant 8000Mah Lipos. They should not be a problem and aren't as far as I can tell.

[MetalMan]

I'm not surprised that it is getting that hot. 5s Lipo is a lot of voltage for the 9L, and is pushing it past 48,000 RPM, which is causing it to be less efficient than it can be. For such a high RPM, you're going to need to gear down more.

The brake fade on the 9920 can't really be fixed besides sending it in. If you put a fan over the heatsink and gear down, it probably won't occur as often or as much.

[squeeforever]

Sounds like you have a controller with brake fade :eek: . I wouldn't run a 9L on 5S lipo though. Thats kinda alot for a 10L much less a 9L. I would personally go for a 10xl and see if that fixes the problem. How heavy is the truck?

[jhautz]

Truck is just a shade over 11lbs loaded with the bateries.

I didn't know about the brake fade issue w/ the BKs. Is the brake fade an indication that I'm pushing the controller to hard? or is it just a flaw in the ESC that happens no matter what. I am assuming its heat realted right?

You are right, I am running that thing right up at the 50k rpm limit arent I. No wonder that thing gets so toasty. I'm just pushing to hard for the setup.

So you think I shold be running an XL motor with this setup?

Now, let me ask this... If I go to a xl motor, can I gear it up to get the same top end and not give up alot of the torque? I love the way this thing runs with the current setup untill it overheats.

If so what RPM should I be shooting for as far a KV rating for the motor. What I mean is, what is the max rpm these feigao motors can run before I start hitting the downside of the efficency curve?

[MetalMan]

Brake fade is a rather common problem with BK controllers that is related to how a component acts once it reaches a certain temperature. This doesn't happen with all of the controllers, you'll get one if you're lucky :).

You can get the same top end with more torque from a XL. Shoot for about 35,000-40,000RPM and you should be in business.

[Dafni]

Hi jhautz, I went through the same story as you, almost two years ago.
BK even did the brake-faders on purpose, only one production batch, for quite fishy reasons. They learned their part and won't do this again. This was some time ago, and only certain retailers got ESC wich shut down their brakes at 55°C. As far as I know, not one single ESC Mike got ever had this phenomenon. I got my bad one from another vendor, too. (btw, I got my bad one replaced for free)

I agree, 5S is way too much for a 9L. And with capacities/runtimes of 8Ah, you're really better of with an XL motor, because they displace heat better.
If money iis not tight for you, I would get a Lehenr 1950 (8 turn for 5 or 6S)

Welcome to the site, man. BTW, I was the one with the first E-Maxx tranny converted Revo here, and Mr. Starscream followed imediately with an auto-shifter. I also started with the 9L and went through several motors until I found what I liked. The Feigao/Wanderer XLs are nice, too, but the big Lehners are 2nd to none.

DAF

[jhautz]

Thanks for the welcome...

I have been dabbling around with bushless for a little while now. I started with an old rustler (Fiegao 380C 9L and Warrior 7020), Losi XXX4 (Novak GTB6.5), Mini-T (Mamba 8K), Mini LST (mamba25 and Hyperion YC-22 5K), and an E-Maxx (Plug and play - Novak HV). This revo is my first attempt at a conversion and I pretty much just did it with the off the shelf GMaxx conversion Kit and a used motor/esc combo from ebay.

This bigger truck is alot more sensitive to bad gearing, and motor/battery selection than the others.

I hear you on the Lehner sugestion but, At this point I'm not planning on spending quite that much on just a motor. While I'm sure its nice (the old saying goes, you get what you pay for) my needs are not enough for that high end of a system.

However, I am considering upgrading the whole system to the MGM 160/16 ESC and the Feigao 540C 9XL motor for about the same price as just the Lehner motor.

What do you think is better for my application. the 9XL or the 10XL? The thing is I have 1 set of the High capacity Lipos, I would also like to be able to runn it on some of my old conventional 14 cell sets as well (while the Lipos recharge) So I am a litle hesitant to go with the 10XL. I'm thinking it might be a bit to low of a KV for 14 cell.

I will probably start with the new motor and try it out on the Warrior 9920 I have. If I still have issues with it I'll just bite the bullet and upgrade the EsC also. I'm sure I can find a home in another (lighter weight) project for this setup sometime

[Dafni]

Sounds like a good plan to me. For the occasional 14 cell run, I would go for the 9XL. (similar KV as one of my Lehners, and I like it on 14 cells too)

I hear you about the price tag of the Lehners, and right you are. You really get what you pay for... I had to learn this the hard way recently, with some cheapo Lipos.
I just had to share my experiences with those high-end motors. They are very nice.

One other thing: Do you have a Mod1 spur (such as the strobe)?? For the 9XL on 14 cells I would suggest something like a 18 or 20/51 gearing.

Good Luck, and keep us updated!

DAF

[jhautz]

I have a 65 tooth steel spur w/ the robinson slipper and I was planning on getting a 24 or 25 tooth pinion to go on it. That should be pretty close.

Thanks for the help...I'll let you know how it goes.

[Nick]

I don't reccomend a steel spur at all. Rotational mass and more likely to wreck the pinion instead.

[jhautz]

http://www2.towerhobbies.com/cgi-bin...?&I=LXBJC5&P=7

This is the one I am planiing on using. Made for the tmaxx. What will it mess up?

I can always use the 66T plastic one.

[Dafni]

Yes, get a plastic spur! Unless you can get hardened pinions, the steel spur will eat your pinions in no time.

And if your really lucky It will shatter the rotor on your motor, when the teeth come off and jamb in the spur.................I've got that T shirt..:032: