Brushless E-Revo Help?

Hi guys.

I am making a Brushless E-Revo with Feigao 7XL and MMM ESC and 14 Cells altogether.

1. What gearing is the BEST for this ESC/Motor/Battery Combo?

2. Are these batteries any good?

http://www.promatchracing.com/proddetail.php?prod=7470S

3. Should I use a BEC for this set-up?

Thanks, Austin.

[BrianG]

What speed are you wanting? 40-45 mph is usually in the ballpark of what most people shoot for. You can use this to get the gearing for the speed you want. Then, I'd get a couple spur options (spurs are cheaper than pinions) in case things heat up more than you like.

And personally, I'd go with an 8XL for 14 cells. 40krpm on the 7XL is a bit on the high side IMO.

Originally Posted by BrianG

What speed are you wanting? 40-45 mph is usually in the ballpark of what most people shoot for. You can use this to get the gearing for the speed you want. Then, I'd get a couple spur options (spurs are cheaper than pinions) in case things heat up more than you like.

And personally, I'd go with an 8XL for 14 cells. 40krpm on the 7XL is a bit on the high side IMO.

How fast will I be going with 14 cells on the 8XL and on the 7XL?

[BrianG]

Technically, the 7XL will go faster with the same gearing, but the motor will probably heat up more/faster since Feigaos don't like rpms much over 30-35k. You can recover any speed loss with gearing (within reasonable limits of course).

Ok, I'll get a 8XL. I calculated my speed and it said 45MPH. Nice speed.

I am buying 16-20T Pinions for $4.29 a piece at Amain. I can go 50MPH with 19T one but does that mean it could over heat? (Meaning the Motor,ESC, or Batts?)

[BrianG]

At high speeds/gearing, you're gonna start overheating the ESC and batteries. If you're planning on getting a few pinions, start low and get a couple options. Not sure where you are geographically, but with summer around the corner, the ESC and batteries won't like too much added heat...

Originally Posted by BrianG

At high speeds/gearing, you're gonna start overheating the ESC and batteries. If you're planning on getting a few pinions, start low and get a couple options. Not sure where you are geographically, but with summer around the corner, the ESC and batteries won't like too much added heat...

Low meaning like 16T Pinion or lower? I am getting an ESC Fan also.

[BrianG]

Without calculating the speed with the various pinions, I'd shoot for whatever pinion gets you ~40mph first. Then go from there.

Originally Posted by BrianG

Without calculating the speed with the various pinions, I'd shoot for whatever pinion gets you ~40mph first. Then go from there.

Ok, Thats a 15T Pinion. What if the ESC/Motor still heats up then? And I can't gear it down to cool it down. Then what happens?

[BrianG]

Well, gearing down will help. Just be aware that no matter what, the Feigao will get hot after a 1/2 hour or so. Just keep motor temps at around 40*F above ambient, or ~150*F max. Figure around 10*F less for the ESC.

[Mike_D]

I use a 40tooth spur and 16 tooth pinion in my Revo and a Feigao 8XL on 4s lipo's and after about 20-25 minutes my motor is about 170 degrees. It's a little on the hot side but seems to be holding up so far.

Originally Posted by Mike_D

I use a 40tooth spur and 16 tooth pinion in my Revo and a Feigao 8XL on 4s lipo's and after about 20-25 minutes my motor is about 170 degrees. It's a little on the hot side but seems to be holding up so far.

Ok. I'll try that. What is the temp outside?

Here's the list:

1. Feigao 8XL
2. Mamba Monster Max ESC
3. 2 4600mAh 7 Cell Batts (SPC)
4. 14T-18T Pinions
5. 40T Spur
6. Traxxas Male Connectors (2)
7. Traxxas Siries Connector

Is there such thing as a motor fan?

[BrianG]

I think the 14T pinion will be the best option for temps IMO. Also, are you gonna go single speed tranny (using the mod) or keep it two speed? That can make a BIG difference in your gear choices.

If you haven't done so, you should read the sticky about using the nitro tranny. It lists the options and the advantages/disadvantages.

[Mike_D]

It's about 65-70 degrees when i get those motor temps.

Originally Posted by DiFabio42

Ok. I'll try that. What is the temp outside?

Here's the list:

1. Feigao 8XL
2. Mamba Monster Max ESC
3. 2 4600mAh 7 Cell Batts (SPC)
4. 14T-18T Pinions
5. 40T Spur
6. Traxxas Male Connectors (2)
7. Traxxas Siries Connector

Is there such thing as a motor fan?

I'm keeping the 2 Speed. Mike, are you running the Single or Two speed?