1518/1520/1717 Replacements

Originally Posted by Unsullied_Spy

Watch temps and don't push it to it's max speed and it should be an absolute animal. Patrick said a while back that they're rated to 45,000 RPM because the magnets will start coming apart at higher speeds. I've run this motor on 4s and 6s and it's stupidly powerful in a very heavy 1/8th scale Truggy, 8s would push a 5th scale pretty well if you were smart about your setup and watch temps. Main problem I see with running it on 8s is accidentally over-revving it, I'd stick to 7s max myself.

Hmmmmm, I think you are right about 7S but I want to fit this setup to a Savage flux and fit one 4S batt on both sides. Going to 7S might cause bit of a imbalance. That is the main reason why I wanted to go with 8S. Wouldn't be nice if the MMXL had a rpm limiter. You just dial into the CC Link what your motors safe rmp is and presto, can't over rev it.

Being a such a over powered rig it will be doing a lot of back flips and spending a lot of time in the air with a fair bit of throttle input for flipping and correcting during flight. This is where I see the over reving becoming an issue. I would hate to destroy one of these motors before Castle starts to make something similar again.

[sikeston34m]

Originally Posted by BIG-block

Hmmmmm, I think you are right about 7S but I want to fit this setup to a Savage flux and fit one 4S batt on both sides. Going to 7S might cause bit of a imbalance. That is the main reason why I wanted to go with 8S. Wouldn't be nice if the MMXL had a rpm limiter. You just dial into the CC Link what your motors safe rmp is and presto, can't over rev it.

Being a such a over powered rig it will be doing a lot of back flips and spending a lot of time in the air with a fair bit of throttle input for flipping and correcting during flight. This is where I see the over reving becoming an issue. I would hate to destroy one of these motors before Castle starts to make something similar again.

Why couldn't you limit the throttle to about 90% in the ESC setup?

What you will find is going to be an insanely overpowered beast anyway.

It always amazes me how I manage to overlook the most simple of things or just over complicate. Limiting throttle is a brilliant idea. I do remember BrianG saying somewhere that limiting throttle EPA to slow down your car isn't a good idea. What would be the difference between doing that (setting the throttle EPA to say 85-90%) and just not using the full throttle? I know what he said has to do with the FETs having the easiest time when they are operating at full throttle but not exactly sure about this.

[ta_man]

Originally Posted by BIG-block

It always amazes me how I manage to overlook the most simple of things or just over complicate. Limiting throttle is a brilliant idea. I do remember BrianG saying somewhere that limiting throttle EPA to slow down your car isn't a good idea. What would be the difference between doing that (setting the throttle EPA to say 85-90%) and just not using the full throttle? I know what he said has to do with the FETs having the easiest time when they are operating at full throttle but not exactly sure about this.

Limiting throttle doesn't have as much effect on peak RPMs, especially unloaded RPMs, as you might expect.

Quite some time ago I did some tests where I gradually turned down my throttle endpoint and measured the top speed of the car at each step. At 70% throttle, I was still at 90+% of top speed.

I was doing this to test the effect of "throttle driving" (a racer term few bashers would understand or comprehend) in a spec class with limited battery. Knowing how to do this got me many wins because I always had battery left over at the end of the race when others were on the verge of dumping because they were pulling full throttle down the straights all the time.

This was a long time ago, but the principle still applies.

Remember, if you turn your EPA down 10%, the ESC is applying full power 90% of the time and you are coasting the other 10% (admittedly in very small increments). But that 100% power, even if only for 90% of the time, is going to get you pretty close to the top speed at 100% EPA.

[pinkpanda3310]

Originally Posted by ta_man

Limiting throttle doesn't have as much effect on peak RPMs, especially unloaded RPMs, as you might expect.

Quite some time ago I did some tests where I gradually turned down my throttle endpoint and measured the top speed of the car at each step. At 70% throttle, I was still at 90+% of top speed.

I was doing this to test the effect of "throttle driving" (a racer term few bashers would understand or comprehend) in a spec class with limited battery. Knowing how to do this got me many wins because I always had battery left over at the end of the race when others were on the verge of dumping because they were pulling full throttle down the straights all the time.

This was a long time ago, but the principle still applies.

Remember, if you turn your EPA down 10%, the ESC is applying full power 90% of the time and you are coasting the other 10% (admittedly in very small increments). But that 100% power, even if only for 90% of the time, is going to get you pretty close to the top speed at 100% EPA.

Boiling that down means - you will have similar top speed and slightly less grunt on take off due to drawing less amps.

I beleive the fet's would suffer if you had it overgeared and used the epa to 'tune' the car but what has been suggested sounds reasonable to me. The fet's are most efficient at full throttle but if the lesser epa reduces amp draw (which is likely to be high on take off with this motor) then I don't see why it wouldn't benefit?? I guess you could use the punch control feature to the same affect?

Shonen do you give it full throttle in the air? If it's just a speed run then wouldn't drag play some part in keeping rev's down?

8s * 1600kv = 47360 revs
fully charged 8s * 1600kv = 53760 revs (but not likely for various losses)

[RC toy]

Originally Posted by BIG-block

Wouldn't be nice if the MMXL had a rpm limiter. You just dial into the CC Link what your motors safe rmp is and presto, can't over rev it.

So when new CC link version is going out, Patrick?