Why 4.5?

[pinkpanda3310]

I wanted to know why do people use a 4.5 on 4s lipo? Couldn't you run a 7.5 on 6s? It would do similar revs to the 4.5 but give more grunt

[BrianG]

For sure, but can the ESC handle that voltage? Plus, Novaks uses a linear BEC on half the battery pack. 3s is a bit too high to keep temps down IMO.

[suicideneil]

Indeed, the hvmaxx esc is only rated for 4s lipo. You could use the motors with a sensorless esc, but the Hv7.5 is rated at 3000kv- thats 66,600 rpms on 6s lipo. Gearing down would produce more grunt, but the bearings wont like you too much; I'd just as soon opt for a larger ~2000kv motor and run it on 4-5s lipo, and gear it taller; more grunt than you can shake a stick at, without overly high temps or rpms.

[SpEEdyBL]

I'm actually going to exchange my HV4.5 with an HV7.5, and have my fast motor be the castle neu 2650. Both motors will be run on 4s and 5s packs. Your right that the HV4.5 revs pretty high, but the real issue is gearing it properly. 45mph is the slowest you can go with this motor in a buggy.

Ideally, higher rpms are better up to a certain point i.e the sweet spot, and novak motors have their sweet spots at a higher rpm than other motors. Also, smaller motors that need more rpm to make the same power have lower idle currents, which makes them more efficient. For example, a neu a 2700kv 1512 1y on 4s will probably be more efficient than a 2200 1515 1y on 4s if you gear for the same speed. Both motors are equivalent powerwise, so no matter what speed you gear for, you will get the same results. The only reason why the 1515 would be better is because it can handle more voltage for more power without dropping off in efficiency.

[pinkpanda3310]

Of course the original esc is not suitable and the price jump to the neu range is not small but I was curious because I noticed a lot of people run the 4.5 which is high speed and sensitive to heat problems anyway.

I've just rewound my original 6.5 4400kv. I wanted to get 6.5 turns or higher but could only fit 5.5. It was recommemded to me to use 8x 0.63mm and 4x 0.67mm copper to replace the 4x 1mm wires on each stator. With that arrangement I could only get 4.5 turns and I thought it would fly off the handle so I reduced it to 6x 0.63 and 4x 0.67 to get 5.5.

I don't expect to have esc problems but I'm inclined to think the motor may overheat. I will test it soon but if it all comes to grief I will re-think my back up plan which was my original question. Thanks for answering guys.

[pinkpanda3310]

Here's a before and after

[kvrc]

pinkpanda....the hv 4400 motor ia just a 6.5 motor with a bonded rotor. if you add a sintered rotor to it you will have a 6.5 except for the ridded endcaps.

[pinkpanda3310]

Yes I have a sintered rotor. I had the original replaced but it looks no different.

[SpEEdyBL]

The sintered rotor should be smaller in diameter.

[JThiessen]

It definitley is smaller in dia. I thought I had recieved the wrong one when I got my replacement. However, I did not know that it essentially changed it to a 6.5. Novak didnt say anything about that to me, and didnt say anything about changing my gearing to suit.

[pinkpanda3310]

Well I may have ended up with a good condition second hand job ( at full price ). It was a smooth can with 4400 sticker but the rotor is definitely the same.

It even ran cooler with a 14t pinion as suggested in the manual. The pro hv recommends 12t but I had heat issues at the bearings with this gear.