Super slow brushless

[vintage88]

Ok I recently put a 540r brushless system on my 10L thinking it would be insane and almost take off flying lol well I installed it and programed it according to the instructions I'm only using a nicd battery but its ridiculously slow seriously It's the slowest car i have ever built can anyone tell me where i went wrong??? is there something I'm overlooking? Oh, I'm using a Futaba Magnum Jr.

Thank you in advance.

Tim

[shane]

Maybe gearing?

[vintage88]

it was super fast with the brushed motor i wouldnt think it would be slower with the brushless???

[shane]

I would try changing gears first, as long as your temps. are good, you are opperating in the safe range. Might find info on AE forums,also.

[Eau Rouge]

What motor is it, and where are you currently geared? Brushless and brushed motor gearing are COMPLETELY different.

[sneako43]

It's my understanding that most brushless systems can't be powered by a NiCad battery. I think you need to run NiMh or Lipo. Not sure but they may be the cause of your speed issue.

[Eau Rouge]

Not true. Electricity is electricity. Doesn't matter if it's coming from a car battery, 8 volts is the same no matter what. NiCd batteries HAVE GOT to be ancient at this point, though, as I don't think they haven't been on the R/C market in well over a decade. That in itself could be the source of the issues.

[Coelacanth]

Not true. Electricity is electricity. Doesn't matter if it's coming from a car battery, 8 volts is the same no matter what. NiCd batteries HAVE GOT to be ancient at this point, though, as I don't think they haven't been on the R/C market in well over a decade. That in itself could be the source of the issues.

That's true that very old NiCad batteries have probably lost a lot of their oomph. But as you said, electricity is electricity (or voltage is still voltage); a 7.2V battery will provide the same oomph whether it's a NiCad 1200 mAh or a modern NiMH 5000 mAh--but the latter will run 4 times as long.

Question: Was the car fast with the same NiCad battery just before you put in the brushless motor? Or was it fast years ago when you last ran it with the brushed motor, going by memory? Or put another way--if you put the brushed motor back in, is it fast again, or still slow (or perhaps even slower)? If that's the case, the finger more likely points at the battery being the culprit.

I'm also restoring a car that hasn't been run in over 15 years, and I have these matched Sanyos (6-cell and 7-cell packs) that I have no idea how good they are, anymore. They were top of the line back in the day, but batteries lose their effectiveness as they age.

[sneako43]

I was wrong. My mistake, thanks for clearing that up. So, for simple testing I now have a use for the Nicad packs on my shelf!

[vintage88]

well the battery is brand new actually i bought it at radio shack it has about 6 runs thru it i also bought the 10L less than a week ago and it was ran with the same battery i also put a ni-mh on the car still slow i really dont what the gearing is as im not with the car at the moment but ill get it up asap but i was told that the brushless had more torque as well as speed so i dont see how it would be slower with the same gearing was i informed wrong??? wat would be a good gear setup for direct drive with a brushless has anyone but brushless on a 10L???

thank you everyone,
tim

[Eau Rouge]

Tim, you need to know the power output of your brushless motor or how many turns it has to be able to gear it properly. You can't use the same gearing as the motor that came out of it before. It's crucial that you gear it properly, or you could do damage to the motor or ESC.

What brand, wind and/or power output is the motor in the car? No way to even begin to guess how to gear the car until we know what motor is in it. There are hundreds, if not thousands of different types of brushless motors with different winds and power outputs, just like brushed motors of the old days. Every one needs to be geared differently to provide the best power.



And yes, you were told wrong about the power and torque. Brushed and brushless motors perform in the exact same way (relatively). The major difference is that with a brushless motor, your maintenance is almost non-existent. After a bit of run-time, the brushed motor will need a rebuild to keep performing at it's peak levels where the brushless will just run the same almost indefinitely. You can get brushless motors that perform like stocks (or slower) and you can get brushless motors that are only useful in drag cars or high speed applications. And they all need to be geared differently to work properly.



doug

[vintage88]

its a 540r 4900kv from reedy

item# --918
cells- 2lipo,4-8nimh
rpm/volts-4900
max efficiency current-10-50 a
max surge current-55A/60s
internal resistance- 12m

i hope this helps i obviously know nothing about brushless this is just what im reading off the box i dont even know the turns... im sorry for sounding so ignorent...

tim

[Eau Rouge]

Reedy's website blows. They have almost no information on their site about gearing one of these, nor what it is.

Based on the specs they show for it, it's a sensorless 9.5T (or so) modified brushless motor. Using some of the other manufacturer's gearing suggestions for a pan car with direct drive, they want the rollout to be in the neighborhood of 1.7"/ 43 mm. Rollout is determined by dividing the tire circumference (tire diameter x 3.14) by the spur and pinion gear ratio. EX. (1.75” x 3.14) ÷ (100 ÷ 23) = 1.26 rollout. This will help get you in the ballpark.

So, we still need to know your rear tire diameter and what spur gear you have in the car right now. That will help us figure out what pinion needs to be on it to get proper performance.





By the way, what motor was in there before?





I'm heading out to a client this morning, so someone else will have to help you with the math to figure out what pinion you need. You guys can also use http://www.gearchart.com for a nice little assistant, too.



doug

[rc10johnny]

sometimes on new motors I have had a few that were slow so I reversed the polarity and made a 100% difference. Just a thought. JohnnySr

[vintage88]

thanks a lot doug ill get the tire size up asap the motor says motor man speed master i dont know much about it but it was quick