Neu motor rpm speed question for BrianG
 

Brian - I have seen in a bunch of threads that you are preferring lately to run the Neus up at the higher end of their rpm range (~50k) saying they are showing to be more efficient.

I wanted to ask you about this and see if you could expand on your thoughts a bit because the little bit of testing I have tried hasn't really shown the same thing, but I know you've got a lot more experience with all of this stuff.

I was running a 1512 2.5d (2050kv) at 4S, 5S and 6S - each time changing the gearing to keep speed as close to the same as possible. Obviously on 4S there was a lot of current being pulled. 5S showed a bit of a drop in motor temperature and more efficiency, but with 6S (~45k rpm) the temp were definitely higher than both 4S and 5S. (this was all in 1/8 buggy)

Was wondering if you could explain how things have been working for you. Also - have read over the past few years that smaller motors are happier spinning at higher speeds than larger motors. So does this mean that a 1506/1509 would be happier at 50k rpm that a 1515 or a 1521? That would seem to make sense as the bigger the size of the motor, the lower the kv ratings - even on the hottest winds.

Thanks

And I'm leaning that way not so much for efficiency, but for running smoother on startup. Maybe it's the fairly narrow magnetic poles inherent in the Neu design, but it seems that running it higher rpm and gearing down made for a much smoother start. Rough, almost-cogging starts probably pulls much more current than smooth starts, so there's some efficiency lost there I'm sure.

It probably also matters how you are using the motor. If running a technical track where non-WOT fine-control is needed, this may be better. If running WOT a lot on a track, you probably don't want to wind it out. Then again, if you are going for pure high speed runs, efficiency doesn't really matter.

I've run the 1512 2d (2600kv) in my Hyper8 at close to 20v (16 NiMH cells - just temporary for testing) on my buggy and it seems to like it. Temps were very close to using 4s lipo, so efficiency seems about on par. Granted, I don't have an eagletree to confirm this, so I'm just using the scientific runtime vs smoothness vs heat method. :smile: It is possible that at higher rpms, the Neu may WANT to be geared a little higher. I know my 16 NiMH cells are definitely heavier than 4s lipo - the added weight can be compared to gearing up a little.

Even when I ran my 4s setup geared 46/16, it was still fairly cool, yet stupid fast for a small track. I did notice that geared that high, the starts weren't quite as smooth - acted like it was on the edge of cogging. When moving to a higher voltage (16 cells) and gearing down, the starts were definitely smoother despite the added weight. I was really looking for smoothness for a small track, so I didn't try that at constant high speed.

I recently tried my 1515 2.5d in the buggy on 20 cells, geared 46/16 and got about the same temps at the 1512 2d on 4s geared 46/14. But the torque was too much. I don't know if the temps were because I couldn't get traction or what. But the starts weren't quite as smooth - I just figured it was because the ESC wasn't getting enough rpms at slow speeds to effectively commutate.

I was kinda limited to the Quark's voltage threshold for my tests. If I can get some time, I might try my HV-110 instead to open up more options. Then, I can try 4s, 6s, 8s on my two motors with different gearing. Then put together some type of chart to get temps vs speed vs current draw vs efficiency, etc.

I'm sure it matters heavily on which ESC is being used too. The CC ESC startup routine certainly acts much different than the Quarks. Even under stall, the Quarks seem much more controlled. However, that was before the MM with Neu update or the MMM. I haven't run a Neu on a MM since the initial test, so maybe it's not the same anymore.

Thanks - I appreciate the insight.

Not being a racer (closest track is about 1:30 away from me) and running mainly in large grassy areas and parking lots (as I am sure many do) lends itself to a lot of WOT just due to the wide open space. I guess in that scenario a high RPM motor would be winding all the way up very frequently and maybe getting hotter in an environment where smooth running isn't so much of a concern (and I will say for a fact that the MM with a Neu before and after the Neu firmware update was a big difference - and the MMM seems to run the Neu even smoother - I don't think I've had a single cogging incident).

There definitely seems to be a big difference in setup for racing vs. bashing.

Brian - one more question.

What controller are you using with the higher speed running Neu's?

If MM what Punch control setting? If other (ie: MGM) are you using any acceleration limiting?

In my lower 30-35k setups I don't tend to use more than 20-40% punch control, but in a higher ~50k setup I could see punch control set higher to prevent the motor from pulling higher current peak to wind up the motor.

Using the Quark 125B. I think the "torque control" is set for "Normal 2", and the neutral range is narrow (seems to help smoothness for very slow running). These settings were not changed for changes in motor or battery.

BTW: I like your sig, and agree. Remove all safety labels and let Darwin do the rest. :smile:

[quote=BrianG;181283BTW: I like your sig, and agree. Remove all safety labels and let Darwin do the rest. :smile:[/quote]

That is a great sig!

What scared me is when I saw the one on the back of my jet ski that said "do not insert genitalia into jet drive". Hmm, just why would they have such a warning label like that on there?! And these people walk the streets with the rest of us..........

Personally, anyone stupid enough to insert their genitalia into a jet drive is doing the world a favor by ending that thin branch of the family tree. :smile:

your kidding it actually says this???? I guess it really doesn't surprise me. Common sense is not very common!

You know - the sad thing about all of these warning labels is that someone somewhere sometime probably did exactly what the warning label warns against and probably tried to sue the company.

I don't know about other countries, but it seems that law in the US is designed to reward to stupid. No one wants to take responisibility for their own actions - if you do something stupid just blame someone else, sue them, win some money and be rewarded for you stupidity.

And where did this all start going downhill? (Many here might be too young to remember) In a MacDonalds drive-thru line with an old lady and a hot cup of coffee...... :lol: ...... and my only comment to that whole debackle (sp?) was IT'S COFFEE, IT IS SUPPOSED TO BE HOT, DUH!!!!!!

Wow :oh: :oh: :tongue: I feel so political......... Time to go back to my toys and figure out how to run my Neu at 50K withouth blowing up my buggy.

So BrianG, are you saying it is better to run the motor rpm higher then gear down to the appropriate speed. Such as running the neu 1515/1y on 6s and gearing for say 45 or so on a monster truck?

This is interesting. I have been experimenting quite a bit with differnet set ups in my rc8. My 1512 1.5d (3300) on 4s geared 12/46 doesn't run any hotter (45,000 +/- rpms)than when I run it on 3s. I pretty consistently get motor temps in the 150s.

I also have a 1509 1.5y (2400kv) that I run occassionally on 4s. I was actually thinking of bumping it to 5s to see if the motor runs better. Geared 14/46 it is a tad faster than a nitro, but I want a little more low end punch. The 1509 on 4s 5000 is good for 20 minutes. I was hoping to gear it down, bump the voltage to get a litlte more power and a little increase in run time.

Thin branch....nice one:lol:

Only a one time sample but my 1515 1y ran (about 20 mins on grass) cooler on 6s than it ever did on 4s or 5s with the plus of the added speed.

Define "better".

If better means "more efficient"; to me it doesn't matter if temps during my informal testing are any guide.

If better means "smoother"; then yes. I daresay almost as smooth as a sensored setup at low speed. Smoother running would also lessen the chance of cogging at really low speeds - and we know that a cogging (effectively stalled) motor pulls LOTS of current.

You don't want to go crazy with this idea though, like putting a 1527/1d (kv=2300) on 6s lipo on a 8th scale buggy, but gear down for 20mph. The motor wouldn't be loaded enough.

What I am trying to say is that I don't like getting a low wind and applying low voltage for low rpm and then gearing up to compensate for lack of speed.

Without gearing down for equal speed, I'm surprised it didn't get hotter actually. If you can, try the test on 6s vs 4s again, but gear down for the same speed. Note temps and smoothness.

So which would be more efficient?

1515 with lower kv and lower voltage but geared up vs
1512 with higher kv and higher voltage but lower gearing

assuming they are speced to run the same speed. It sounds like you are saying that a 1515 with more torque would be better suited for lower kv/high voltage setups vs the 1512 which might be better at higher RPMs. Since the 1515 is a stronger motor, it would seem the lower kv setup wouldn't have the cogging issues you are referring to...