I think I'm going to order 2 2S neuenergy batts and pair each to my 3S for a 5S setup. I like the power of the 6S on 51/20 gearing though :).

I think your fishing methods aren't correct.

Isn't the max RPM of a motor based on the size of the pack X the kv?

ie:

3s = 11.1v x 2200kv = 24420 RPM
4s = 14.8v x 2200kv = 32560 RPM
5s = 18.5v x 2200kv = 40700 RPM
6s = 22.2v x 2200kv = 48840 RPM

Or am I way off the mark here? :neutral:

That's what it says on Brian speed calculator :lol:.

yeah...i think he was just using 4.2v instead of 3.7v :neutral:

3s X 3.7 = 11.1 vs 3s X 4.2 = 12.6

but remember the max rpm of a motor is still limited by the quality of construction and size of the motor. In this case, we are talking about neu motors which have a max rpm recommendation of 60,000rpm. So take your max rpm and divide by your voltage to get the max kv rating.

60000 / 22.2 = 2702kv
now is this the end?....nope
while you CAN run the motor to 60000rpm, it doesn't mean you should. Running any motor at its max will most likely cause heat/efficency issues.

and here is where brian and others could probably school me...
...i have heard that its best to run these motors in the 40000-50000rpm range for best efficency.

which is why I bought the 1515/1Y to run on 6s (22.2 X 2200 = 48000rpm max) Only time will tell....:neutral:

So, me running my 2700kv on 5s @ 49950rpm is pretty much right on the money.

Also saying that my gear ratios are ok to not overheat the motor. So far it's ok.

yes, exactly. i use 4.2V per cell as worst case (highest rpm), as lipos come off the charger at 4.2V per cell.

i never did catch much fish.

yep to get the true MAX rpm you will need to use 4.2v/cell. Any lipo charger will charge the lipos to 4.2v/cell unless you tell it to cut off at less on some chargers.

I think that's WAY overkill. I've got a CRT running 4s on a 2200kv and it's ballistically fast. Too much speed and power for the track - big track too. Can't imagine how unholy the speed of a 2700kv on 5s will be...you can't gear low enough...

I wouldn't be concerned with using 4.2 volts/cell in any of your calculations because your cell will never hold that voltage (even fresh off the charger) when you wind that motor up to full speed. Best case you are looking at is 3.7-3.8 for a while and closer to 3.5 (with only the best lipos) when pulling ~20C.

As here is where 2S and 3S setups will have trouble as you'll be pulling big amps and the per cell voltage will be closer to 3.3-3.5v/cell.

I use the nominal 3.7v/cell in all speed calculations for HV. If you are going LV (ie: 2S or 3S) I would recommend using 3.5v.

If that's the case, I'm staying with 6S on my 1515 1Y then. Right now, it's geared 51/20 with 43/13 1/8 scale diffs.

I'll be right behind you in a couple of weeks. Sounds perfect to me {insert silly:mdr:}

I know you guys don't have the 3905 like I do but there's a chance of extra carnage from your drive line. I've had to replace front center shafts twice running 6s. The second one only lasted about 10 mins. I now have the kershaw front center installed. Hopefully that takes care of it.

Thanks for the heads up, but I guess that is "part of the deal".

Are you running plastic front centers when you broke them? Right now, I'm using a pair of UE titanium center dogbones and UE 8mm cvds on my truck. I also ordered a 108mm steel dogbone from rc alloys as a backup if I break the titanium centers and I also have an extra pair of UE 8mm cvds :party::intello:.

Yep, I was running the 3.3 plastics. First one just stripped, second one sheared at one of the u-joints. They also were very hot to touch at the joints, but don't know why since tranny and diff seem to be turning freely and only fronts have this issue. I already have steel cvds so now with the addition of steel dogbones I'll see if it hold together. Hopefully diffs/tranny hold up:smile: