brushless losi 8b

[shizzon]

on 4s a 1515/1y (2200kv) has power but it is controlled, in 5s it gets a little out of control and o havn't tried 6s, i can only imagine. For racing i would say 4s, for bashing 5s is my favorite.

[FG101C]

Any ideas why my Medusa 36-70-1600kv motor got hot running 5s geared 14/45 in a Losi 8B. It ran awesome on 4s geared 16/45 and cool but wanted to try 5s to get a little more speed. I know the Losi 8ight diff ring and pinions are 40/13, and with that 45 tooth spur is why I think things get hot easy in this buggy.

I was running a NEU 1512/2.5/D/F (2050kv) on 4s but it got hot, over 175, on any gearing combo from 10/45 all they way to 16/45. All the typical things are ok, drivetrain is free, nothing hangs up. The only main difference I seem to notice is the majority of people on here don't run on a track in race conditions. Speed runs in a parking lot are not going to heat up the motor like running on a track will. I've only ever driven it on the track. There's no way I could run the 2650kv motor, would hit 200 in 5 minutes. Maybe my driving style needs work.

Any ideas or suggestion are greatly appreciated. Thanks.

[SpEEdyBL]

It could be just bad luck or that your not getting enough airflow. On my 8ight I cut some holes in the right mud guard to get more airflow to the motor. I notice that using the breaks really increases the temps a lot. Try being smooth on the throttle and breaks, do not use drag break, and try to maintain as much speed as possible into the turns.

Other things you have to watch out for are bad gear mesh and any loose connections. Either will increase temps fast.

[GO-RIDE.com]

Originally Posted by FG101C

Any ideas why my Medusa 36-70-1600kv motor got hot running 5s geared 14/45 in a Losi 8B. It ran awesome on 4s geared 16/45 and cool but wanted to try 5s to get a little more speed. I know the Losi 8ight diff ring and pinions are 40/13, and with that 45 tooth spur is why I think things get hot easy in this buggy.

I was running a NEU 1512/2.5/D/F (2050kv) on 4s but it got hot, over 175, on any gearing combo from 10/45 all they way to 16/45. All the typical things are ok, drivetrain is free, nothing hangs up. The only main difference I seem to notice is the majority of people on here don't run on a track in race conditions. Speed runs in a parking lot are not going to heat up the motor like running on a track will. I've only ever driven it on the track. There's no way I could run the 2650kv motor, would hit 200 in 5 minutes. Maybe my driving style needs work.

Any ideas or suggestion are greatly appreciated. Thanks.

Somethings going on with your setup. I mostly drive at the track and will run up to 15min non-stop race pace. I haven't had my motor over 150F (Medusa 60x2000 4S geared 13/46 or 14/46). I'd check a number of things:
1. All connections - after a run notice if any of the connections or wires are very hot or hotter than other wires. A bad connection will generate heat.
2. Air Flow - I have a number of large holes in the windshield and a few over both the ESC and motor. I also have the intake vents cut open as big as possible.
3. Diff setup - I'm wondering if you need a diff rebuild. If the oil is no longer doing it's job then the wheels will diff-out badly requiring a lot more throttle for a given amount of acceleration.
4. Gear mesh - sounds like you've changed pinions a lot, but maybe you're just running them too tight. There should be a little bit of free play btwn the spur and pinion at all times.
5. Bearings - A bad diff bearing will generate a lot of heat quick and bad hub bearings can to the same.

Check those and let us know what you find out.

[FG101C]

The track was requiring alot of braking, I will definitly check heat on individual wires and connections. Mesh is good, diffs are fresh, I'm using the 8ight-E body so airflow isn't a problem. Bearings all check out. Can't run now for a week or so as the track is getting a rebuild. I really think I should pitch the Losi motor mount get a RC-M mount so I can get a 48 tooth spur in there. That or put the truggy ring and pinions on the diffs (43/10). The Losi motor mount makes changing pinions so easy though, I could try making a way to shim up the diff with with some aluminum plate I have laying around.

Really the temp, speed and handling are good on 4s, but this goes against everything everybody says. On 4s the motor rpm are 23,680, everything says to be between 31,000 and 35,000. On 5s rpm are 29,600 and the temps go up, geared down.

Only other question I can think of is. Are brushless motors super sensitive to undergearing, more sensitive to undergearing than overgearing? I know brushed motors are sensitive to overgearing, just wondering if brushless is the reverse?

Thanks again.

[shizzon]

Ive noticed no increase in temps on my motor/esc when i when from 4s to 5s, this is on a 2200kv motor and MMM esc. If anything the esc and motor seem to run cooler..

[GO-RIDE.com]

Originally Posted by FG101C

The track was requiring alot of braking, I will definitly check heat on individual wires and connections. Mesh is good, diffs are fresh, I'm using the 8ight-E body so airflow isn't a problem. Bearings all check out. Can't run now for a week or so as the track is getting a rebuild. I really think I should pitch the Losi motor mount get a RC-M mount so I can get a 48 tooth spur in there. That or put the truggy ring and pinions on the diffs (43/10). The Losi motor mount makes changing pinions so easy though, I could try making a way to shim up the diff with with some aluminum plate I have laying around.

Really the temp, speed and handling are good on 4s, but this goes against everything everybody says. On 4s the motor rpm are 23,680, everything says to be between 31,000 and 35,000. On 5s rpm are 29,600 and the temps go up, geared down.

Only other question I can think of is. Are brushless motors super sensitive to undergearing, more sensitive to undergearing than overgearing? I know brushed motors are sensitive to overgearing, just wondering if brushless is the reverse?

Thanks again.

The basic rule of thumb I've always been told is:
Hot motor + cool esc/batteries = under geared. (not enough load on motor, so it over revs)
Cool motor + hot esc/batteries = over geared. (too much load on esc to supply amps, causes it to heat up & thermal/fail)

Maybe you are just geared too low for the average speed of your track.

[FG101C]

Once the track is back up I will do some more testing. I still think I should get a 48 tooth spur in there. What gets me is Losi keeps making the spurs smaller. 45, 44, 43.

[GO-RIDE.com]

I believe the Losi spurs are for the Losi conversion kit. Their kit does not raise the center diff up to clear a 48. Which conversion kit do you have? I like the Kyosho plastic spur 46T that RCM sells.

[FG101C]

I have the Losi motor mount, mainly because it makes changing pinions and setting mesh so easy but it's actually verry limiting. Probably get a RC-M mount next week so I can get a 48 tooth on there. Although I guess the setup is actually pretty good on 4s. Good speed and very contollable on the track. Guess I just can't stop tweaking.

hi guys, i am still waiting on the 6.5mm CC plugs but i am looking at getting a plastic spur now as i have heard that the medusa doesn't like metal too much
would this do the job?
http://www.google.co.uk/product_url?...hl=en&sa=title

thanks richard

[GO-RIDE.com]

I've heard of some problems with the Losi plastic spur. The Kyosho one is very solid, but requires using the Kyosho o-ring to properly seal the output shaft.

Originally Posted by GO-RIDE.com

I've heard of some problems with the Losi plastic spur. The Kyosho one is very solid, but requires using the Kyosho o-ring to properly seal the output shaft.

so does the kyosho fit with no problems then?
it is this one right?
http://www.modelsport.co.uk/index.ph...xtString=IF148
EDIT: would these work? http://cgi.ebay.co.uk/Kyosho-Main-Ge...3A1%7C294%3A50
where can i get the o ring from?

[SpEEdyBL]

The ebay one will not work, the first one will. I only know A-main hobbies (amainhobbies.com) sells the o-ring. I'm sure there are other places closer to you.

whats the part number for the o-rings?