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...

I think we are getting a little bit away from my original point. I don't think there is a question here about LV compared with HV. It's a proven point by Ohm's law that if voltage goes up across any resistive load then current goes down (it is the resistive part of the motor which generates the heat - aside from the spinning bearings which do generate some mechanical heat).

I've easily proven to myself that running a 6S setup is much cooler than running a 4S setup due to amps pulled.

You can't really make a comparison between a 1512 and a 1515 at different kvs - the 1515 is bigger and will draw more amps.

The question is more about that happy point where you get the most efficiency out of the motor. Compare a 1515 2.5D (1650kv) and a 1515 1Y (2200kv) both running at 6S. That 36600rpm vs. 48800 rpm say geared for the same speed - which would run better.

With the Faiegos and other cheaper motors you couldn't run over 35K without major heat issues. So that is where I have been shooting for even when buying Neus. Now I am more curious what happens when you aim your peak rpms to be closer to 50k.

Both motors will have gobs of torque and the question of efficiency comes into play asking the question - which will draw more power and produces more heat:
- The slower motor with a bigger pinion, or
- the faster motor with a smaller pinion

When do you hit the point that the motor is spinning so fast with too small a pinion that it isn't loaded enough, or conversely when do you hit the point that the pinion is too large and you are over loading the motor.

Understood, thank you. Unlike some people on the "other boards" I appreciate your long explanations. :mdr:

:mdr: :oops:

Which boards would you be talking about I wonder :whistle:

You know, those "other boards" with the people and the mods and what not......

So down to the real question, do you then recommend running the 1515/1y at 6s in an e-maxx geared for 45 or so versus a 1515/2.5 all in an e-maxx?

So what is the average (Or best) final drive ratio that we can have to determine the right motor for our application? Most of my vehicles are geared for 15+ final ratio now and everything is working good. Speed is around 39-40mph.

I dunno.

I kinda work backwards. First, I estimate the motor series (1515, 1521, etc) I'll need based on vehicle size/weight. Then, work backwards with my desired speed and gearing to calculate the motor rpm I'll need. Then, the kv is determined by the motor rpm and voltage I plan to use. This is the method my calc program uses for the motor estimator.

If I know I'm looking for an unusual application, like super high speed where tall gearing is necessary, I'll go up on the motor series to give extra torque to compensate.

I was thinking about this and you may be right. The field I was running on had a lot of irregularities so I was wot only for short burst since I was geared for about 50mph on 6s. On 4s it was mid 30's so I could wot almost the entire time. Probably explains why it was cooler on 6s. I will try what you said however to verify. Incidentally, the last two times out on 6s I blew the front center shaft on my e-maxx. Never had any issues before on 5s or 4s.

Lutach - I read a thread on another "reliable" forum (can't remember which) about a year ago by a really hardcore 1/10 on-road guy who was describing how the final drive ratio should be 1:1 with the rollout of the tires for highest efficiency of the setup.

I blew this off originally and didn't think much of the logic behind it - probably at the time because we were all setting up our systems for 30-35k rpm to "match" the equivalent speed of the nitro that would have been in the system originally and that was what most motors could handle before overheating too much.

Using the RC-Calculations page you can find this ratio easily by looking at the fields for "Total Reduction Ratio" and "Tire Circumference". If the two numbers match then you ratio is 1:1. If the rollout is 15" and the total ratio is 10, then the number is 15/10=1.5.

This makes sense if you think about it for a while because if you increase the size of the diameter of your tires, you have to reduce the size of the pinion to make up for it. And MTs with larger tires have a higher total reduction than buggies with smaller wheels.

I also came across an article within the past week or two that eluded to this same concept that was talking about the way people are setting up their vehicles lately. It is hard to get a true 1:1 ratio and usually it is closer to 1.25, but lately people are gearing closer to 1.5 and even approaching 2 at times - and this is leading to much more heat being generated in the setups.

Another way I came up with looking at this is that you should setup your system for 1" of travel for every 1 revolution of the motor.

Here's how I am going to test this and Brian's theory on faster motor speeds on the Neu on my CRT.5.

I just got a 1509/2Y (1820kv) for my CRT.5 and have been running it at 15/46 on 5S with ProLine 30 series wheels and tires. The specs for this setup are:
Tire diameter = 4.1"
Motor RPM = 33670 (@3.7 v/cell)
Total Reduction Ratio = 9.97
Tire Circ. = 12.88
Est. Top Speed = 41.21mph
Ratio = 12.88 / 9.97 = 1.29

This is a very cool setup and runs awesome.

I am going to setup this system to run with 6S and push the motor rpms up to 40400.
To compensate and also to get the rollout/gearing ratio closet to 1:1 I will run a 13/46 setup with the following:
Tire diameter = 4.1"
Motor RPM = 40400 (@3.7 v/cell)
Total Reduction Ratio = 11.5
Tire Circ. = 12.88
Est. Top Speed = 42.85mph
Ratio = 12.88 / 11.5 = 1.12

Everything will be well within comfortable specs of operation. I have already run the 5S setup and will run the 6S setup tomorrow after work for a bit and report back on performance, smootheness, acceleration, temps, etc.

I have come to the conclusion that for the weight of the vehicle and size of the tires it take about 800-900 watts of power to push the truck the way I like it - so I don't expect that to change to much - it has been pretty consistent with 3S 4S and 5S setups. The question will be if the 6S and faster motor speed is better.

Unless I'm missing something, it seems like the weight of the vehicle could have a huge effect on the load to the motor (heat?) even if you have a 1:1 ratio. So there'd have to be a way to figure ideal power/weight to maintain desired heat level.

Like I said - I don't fully buy into the concept - but it does make some sense.

I guess weight comes into play the same way it does now. 1509/1512 for a buggy, 1515 for a truggy/mt, etc.

So I went out and tried the 6S setup with the 13/46 gearing running at about 40K rpm. I even turned up the punch control a bit on the MMM.

Results are that the temps were hitting up around 180* compared with around 150* for the 5S setup after 10 minutes of hard WOT running in a huge parking lot.

I will admit that the acceleration and startups were definitely a bit smoother, but this wasn't enough to convince me that for my driving style sticking to around 33-35krpm in my setups just seems to work best for me.

In a track situation with much more technical driving and only a bit of WOT I could see that faster rpm setups working very nicely.

There is no definitive answer here.

I don't there is a definitive answer here either because there are so many variables.

If running at more or less constant high speeds, I can see the high rpms heating the motor up more. And really, smoothness is irrelevant at high speed running anyway.

If running where the speed varies a lot with little top-end speed, I can see setting up the system for higher rpm to give more control at the lower speeds.

So, there is no one-size-fits-all solution, but the 35k "golden rule" can work for all around use. I just prefer smoothness at low speeds along with high speed capability.