Pushing the limits of a motor

[NitroVal]

I was curious about free-load vs under-load rated RPM on a motor. Say I get an 8L Fiegao, which is rated at 3201kV. I want to run it on 5S. In OSE's calulator, it will put the loaded RPM at 47,374 RPMs, however free-loaded RPMs will be 59,218 RPMs. Will being so close to its max RPMs cause any problems, or is it just one of those "buffer" numbers to deter people from spinning them that fast? Does anyone with personal experience know if a Fiegao will spin that high? Will amps play a big part in it?

[domwilson]

The big question is...Do you have funds just in case of a catastrophic failure? Because when the motor goes, it will more than likely take out your ESC. Also, that's not even taking into account your drive components or batteries.

[NitroVal]

Can you elaborate? Would the amperage be so high it would just overheat everything? I'll also be running an Eagle Tree data logger so I can watch the amps. I was more curious to mechanical failure rather than electronic failure- as in the armature flying apart or bearings seizing up

[Ub Hauled]

when you get to rev the motor in such high RPMs there are a few things that can occur.

The rotor may come apart, specially if it's made "under par".
Ferrous loss, which naturally occurs in any magnets.
You'll need more amps to drive the load (due to the above) and then things heat up quicker.
"Under par" bearings. seizing.
Wire insulation melting and shorting out... that's a good one... it fries EVERYTHING!

This kinda setup is only good for a saw pass at best... don't get so close to the limits of the equipment just by relying on the FeCalc app... I ran an 8L on 4s for 2 passes and the motor was already untouchable, with 5s I can only imagine the cooking that will occur... this motor is 3s, anything above that is based on how much luck/experience you have.

IMO.

[Christaphason]

I saw a Feigao 6xl on 4s and when the motor went the front bearing failed bending the shaft of the motor busting them flex cable and damn near losing the whole drive dog flex prop set up out the back end.

[NitroVal]

SO it seems like there is an "untouchable" zone where the parts will run in, but not without catastrophic failure? What about a comparable Neu motor? One of my biggest missions on this project has been alot of cooling. I have every electronic and motor on its own cooling circuit, including the batteries..

[domwilson]

As a rule of thumb, at least for me. Sport running 25k-30k rpm's. I don't race. But for SAWS I would venture to say 30k to 35k rpm's. 40k and above for the very experienced SAW racer. It's not just cooling you have to take into account. It is a balance experience, expectations and limitations of the equipment being used.

[Ub Hauled]

The better the quality of the motor the closer you can get to the edge of failure...
lots of cooling will help but that's all that it'll do, physics will take over at some point

[Simon.O.]

As a rule of thumb, at least for me. Sport running 25k-30k rpm's.
I don't race. But for SAWS 30k to 35k rpm's.
40k and above for the very experienced SAW racer.
It's not just cooling you have to take into account. It is a balance experience, expectations and limitations of the equipment being used.

I can verify some of these that I have made bold.
25-30krpm is easy on props and handling......if the rest of the setup is appropriate
Above that is mad rpms that I like to dabble in and learn.

6XL on 4S easy for a rigger
12S on 4S lipo going high !
8S on 3S lipo Going very high rpm !

These are setups that I have and do run.