Why brushless (inrunner) motors aren't best for crawling

[Johnnysplits]

Originally Posted by colebz

Here you go. Let me know if this is what you wanted. I am just getting used to the 4pl in my wraith. Only had it in the past couple runs and the throw is way different than a traxxas tx, lol.
Is there a sensitivity adjustment for the throttle on the 4pl?
https://www.youtube.com/watch?v=P1G7...e_gdata_player
Also, an example of how slow it can go forward, uphill http://m.youtube.com/watch?feature=m...&v=7GBfL6levwQ

Cool vids!!! Yeah, add in expo to your throttle...it will decrease sensitivity around the neutral point. Start with say 20% and adjust up from there.

[6sharky9]

Agreed that a good radio can make a difference in a lot of areas..Im just now getting around to using my old DX 3.0 to use on my scx10.

[Olle P]

Trying to sum this up...

For our typical need of smooth controllable operation with good torque at low speed, and functional drag brake:
* Brushed motors are always good.
* Brushless motors have a tendency to cog and free coaster that can be substantially reduced by...
- ... gearing down,
- ... have a sensored motor, and
- ... have more poles.

I use a cheap sensored 2-pole inrunner, and it does cog a bit. Using the lowest gearing available does help. Drag brake is not an issue with worm drives.

I plan to get a Revolver S within half a year, and expect great improvement...

[4WheelRC]

@John Holmes: Many thanks for your extremely informative reply above

Could you answer an question?... In my SCX10 (87T spur/14T pinion), I am currently running my Novak Ballistic 13.5T sensored brushless motor on a crappy 45Amp Hobby King XCar ESC (but hey, it is good for the price), because I blew up my Novak Timbuk2 (don't ask!). I found this thread as I am looking for the best ESC to give me the best possible low speed control (sensored brushless). You said...

Originally Posted by JohnRobHolmes

There are commutation schemes that prevent freecoasting on brushless motors. The problem is that most ESCs on the market don't have the processing power to handle it.

"most ESCs"... so are there some ESCs that do? Could you let us know which ones, to save me a lot of $$$ buying & testing 'suspects' until I find a good one (Tekin RS Gen2, Castle MMP, Novak Timbuk2 etc.)?

Thanks in advance

P.S. I appreciate that a higher turn motor would give me less RPM/volt and thus help with low speed control, but I wasn't thinking about that when I purchased it last year. Doh!

[rdub]

Just wanted to throw out that I am running a tenshock sc411 3500kv in my twin hammers which I do crawling with and some bashing with. On stock gearing this thing will snail crawl and the torque is unreal. It is a sensored 550 4 pole motor. I waterproofed it and am running a tekin rs pro that is waterproofed as well...so far so good. No Issues. I run mine on 2s...3s is out of control fast in this rig without gearing down. I have ran mine through 4-5 inches puddles/creeks. Completely submerged scares me and have not tried it yet.

It will snail crawl if when the esc is set properly. I have found that the 550 motors do not like advanced timing. so I run mine on 0 timing and it is incredible.

[67mustang]

This is/was interesting thread. I too dislike the freerolling disadvantage. In 1:1, compression braking is nice. Compression braking + gearing reduction is even better.

So I just built a big h2 and i used my mmp, roc412 1200kv, a 2speed ax2, and 6/66 gearing on 3s. When this motor/gearing is in my crawler(wraith trans reduction like 2.6) i have the freerolling issue. Not terrible but its there. However when the same setup is in the h2 and in low (like 4.8 ), i can creep the heavy h2 like a brushed motor down a steep slope with great control. When it is in 2nd gear the drag brake will slip slowly down a slope and it is set at only 40%.

At the end of the day, the trans reduction is the difference. It also makes me wonder why people seem to hover around 4:1 to 7.5:1 with a 3000kv+ motor and never go any deeper.

So ya, if you want to downhill a sensored inrunner as good as a brushed motor, get the deepest gearing. In my experience, the 2.6 axial trans wont do it. Anyone know what the true gearing of a summit trans is?