-
Welcome to RCCrawler Forums.
It looks like you're enjoying RCCrawler's Forums but haven't created an account yet. Why not take a minute to register for your own free account now? As a member you get free access to all of our forums and posts plus the ability to post your own messages, communicate directly with other members, and much more. Register now!
Already a member? Login at the top of this page to stop seeing this message. -
cc's 9000kv brushless motor
- Thread starter NeXt559
- Start date
engineerjoe
Rock Crawler
I thought the general rule of thumb was 50,000 rpm's max (due to the bearings in the motors). so with a 9000 rpm/v motor you should only run 6V max.
gear down, volt up "thumbsup"
I'd say go with the VXL motor (3500kv) or the 4600kv and a 4s lipo
this will keep everything pretty cool and last a long time.
gear down, volt up "thumbsup"
I'd say go with the VXL motor (3500kv) or the 4600kv and a 4s lipo
this will keep everything pretty cool and last a long time.
TwistedCreations
Colt Python/SR9c
engineerjoe
Rock Crawler
wow!! 100k bearings! nevermind what I said before, go with this!!!! "thumbsup"
Where did you get that info from ???
3,500Kv x 14.8 = 51,800
4,600 Kv x 14.8 = 68,080
Sorry, but that will not stay cool for long. :roll:
engineerjoe
Rock Crawler
I guess your setup is different than mine.
Mine stays cool unless I WOT (wide open throttle) 2 packs in a row with no down time.
(I will note that I am using A123's so it's at 13.2V, and I am using a sidewinder, not a MM)
I use this setup in two different cars:
1. Slash w/ VXL, 4s2p A123
2. Tamiya Durga w/4600kv 4s1p A123
The old castle motors were rated for 60k max. The new rotors are rated at 100k rpm.
WOW, thats gonna get hot. :shock::lol:
The bearings will heat up fast, and boil off the oil. But, the rotors can take it 
yup thats it
thanks for the link"thumbsup"
im going to be puting it into a traxxas slash. honestly i dont even think im going to be using it to its full potential very often. at the monment im running a stock slash w/ a seven cell (*sometimes eight) and it seems plenty fast. w/ a new brushless system especially the 9000kv im probabbly going to keep it at 50% - 75% at most for longevity, but once in a while i want to able to "whip out the bull's balls" when i want to do some speed runs or show off a 12 year old thats running an e revo thinkin he's the s**t 8)
TattooKenny
Who's your Daddy-0!
I have the small CC 9000kv for the 1/18 stuff.....FAST!!! I run the 7700 in the on road stuff.....and they are to fast!
A 9000kv motor is a very poor choice for a Slash.
im using a 8000kv in my 1/16 scale edm w/ 11 cells :shock:. i cant even turn at speed, and this past weekend i ended up shattering a rim and shreading a tire when i hit a piece of glass on the road :ror:im planning on converting it to a drag racer actually
.... please elaborate
like i said im probabbly not going to use all that power, and just run it at full capacity once in a while.
and who said need? i want excess!:grin:
i dont see why not? ;-)
You have a higher current draw with a higher kv, which means more heat. With the torque required to push a Slash, that motor will be working very hard unless you can gear it down enough to compensate. It's much more efficient to go with a lower kv motor and run on higher voltage to minimize the losses.
How fast do you want to go with it?
A higher KV motor has less resistance, so higher amp draw does not indicate more heat. Efficiency does not corrolate with KV until construction extremes are met. Bearing failure is one extreme.
A higher voltage does allow use of smaller power wires however, since lower battery side amperage is possible for a given power output.
A higher voltage does allow use of smaller power wires however, since lower battery side amperage is possible for a given power output.
I agree with that. I probably didn't state it as well as I should have.
Do you not agree that the additional torque load placed on a high kv motor in this application will result in an increased current draw and in-turn, more heat?
I do agree there- as you put additional load on a motor it will heat up because of the increased amp draw. A CM36 can only push a vehicle so fast before overheating, this much will not change. You will just be able to hit XX miles an hour on a lower voltage. Harder on the battery, harder on the wires, but motor efficiency will not change.
Take a pede and gear it for 40mph with a 7.4v 6900 and 11.1v 4600 system. The motor heat should be the same. The 6900 system should be more nimble from the lighter weight. The 4600 system will have 1/3 longer runtime from the additional watt/hours added in the pack.
Take a pede and gear it for 40mph with a 7.4v 6900 and 11.1v 4600 system. The motor heat should be the same. The 6900 system should be more nimble from the lighter weight. The 4600 system will have 1/3 longer runtime from the additional watt/hours added in the pack.
The problem is that you'll have folks gearing a 9000kv for 50mph on 7.4V in the Pede. That's where the problem lies. Some people simply expect it to just be faster because it's a higher kv.
