Motor heat

[DPeterson]

Due to being accused for slinging BS in the News Years Resolution thread I figured I would further clarify what I have found and experienced with my boat set ups. I could care less about the accusation, but thought maybe some of you that have difficulty with heat issues may find something here beneficial.

I will say again, I do not generate very much heat at all with my open power setups and I have had pretty good control with my P-Limited set ups. Why?

My power set ups: N2 Mono (nats offshore winning boat) - The motor is a Lehner 1940 4 turn and a 2P setup. The motor mass size is similar to the 2030 and the TP 3630. Most would consider this motor mass size to be conducive for 4S. I consider it a 2S mass size motor. P-Mono - This motor is a Lehner 2260 5 turn and also a 2P set up. Most would consider this motor mass to be conducive for 6S. I consider this a 4S mass size motor. Motor mass dissapates the heat. Spent two years testing and burning motors to find this after lipos came out. The tricky part of going up a size with motor mass is finding the right KV so you can still get close to 30,000 rpm to the prop.

P-Limited set ups. IMO the 36 diameter by 55-65 length motors that are supplied by the vendors in the rtr offerings are insufficent for 4S. The mass is not there. IMO - bad engineering. With the right wind this mass is good for 2S power. And of course some decided we should use these for a fuse. I guess.

So for under massed motors in a P-Limited set up what do you do. Large aluminum motor mount. Good water cooling - dual lines. Short .150 flex installed perfectly. Ball bearing strut. Very sharp and prepped prop. The tricky one - set the boat up loose.

These building methods have kept my P-Limited set ups from exceeding 100 degrees. Not counting the current 2030 issue.

Maybe there are a couple ideas here a couple of you guy's could utilize. Feel free to contact guys I race with for verification.

Doug

[Fluid]

Doug, stating that you motor temps never exceed 100 degrees is SO misleading. Note that I am not saying your statements are false by any means! Racing in the summer here in Texas the ambient temps can be over 100 with water over 90. No way to run for two minutes and keep motor temp at ambient, they are closer to 125. OTOH a few weeks ago it was around 50F with cold water, temps on my Limited motors were under 95 after a full heat.

Of course I assume you are taking temps on the end bell, not the water jacket. Not everyone does. I love comments like "after five minutes running the motor was ice cold". Right, try that in Texas or Arizona in August. Even racing in Alaska on a short course motors got hot. Not arguing at all, but the context of the temperature readings is essential, otherwise it is almost useless info. It's a big world outside of the northern tier states.....

That said, your suggestions are pretty sound IME. A loose boat is a cool boat...but it has to stay on the water. More important than BB struts and short flex is a perfectly aligned coupler/stuffing tube. And it doesn't cost a thing other than time. Short wires are important yet we see spaghetti in the majority of newbie boats. Inadequate packs are another source of heat. There is a lot to a fast, cool-running FE boat.

Oh, and the Limited motors are not a poor design at all. They are about perfect for the manufacturer's use with small props in RTRs. Racers make up a tiny percentage of the consumer demographics for RTRs, we are simply lucky that these motors can be used. Problems arise not due to bad engineering, but to the abuse we pit them to well above their intended design use...



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[HangTheMan]

Being from Houston, I have to agree with Fluid. In the heat of summer, the temps on my motor are in the 90's, and that's before it is run. So it depends on the climate.

[DPeterson]

Gets hot in Wisconsin too. Got really hot at Colorado at the Nats a few years back. Arizona is usually always warm. I always take my temps from the motor shaft exiting the end bell.

One day at a local race - we could not believe the temp results we were getting with my temp gun. We grabbed two other temp guns and got the same low results. So again - not claiming to be an expert, not slinging BS and not predicting what may or should happen in another geographical area. Just reporting what I have experienced.

Good point on the coupler and wires. Another one I missed is, set the esc timing to the motor manufacture suggested timing or below.

I too understand why a rtr boat supplier would spec a 36 x 60 can for a 4S system. Cost - Sales price point - Profit margin. It is what it is.

[HangTheMan]

Hi Doug, I didn't mean that you were slinging BS. Not my intention. I just wanted to note that in hot climates like Houston in the summer its really hard if not impossible to stay below 100 after a run, so it depends on climate. No offense meant.

Dillin

[DPeterson]

No offense taken Dillin. The accusation of BS came from a different thread and is why I wanted to clarify my experiences with this thread. I am getting the same feeling of why experienced racers and boaters no longer like to post to help out. Simply expressing ones experiences are enough to get slammed. Good thing we are big boys. :)

Doug

[photohoward1]

I agree with Doug. I think he is stressing motor size. This is the analogy I always give new guys at our club. We all seem to understand internal combustion auto motors. *** Imagine two motors, one a 2.5 liter 4 cylinder twin turbo pumping out 500hp. Imagine another 5.0 liter naturally aspirated V8 pumping out 500hp. What engine do you think is working harder? What engine runs cooler. Which one will last longer? *** I do understand power to weight but this discussion is about longevity. I have spent more money and tossed more cheap motors into the trash over the last 25 years than I have spent on Pletts, Leaners, Neu or Aveox motors. Cheap motors get tossed, great motors live on and on in everyones future projects. Think about that the next time you put a 36mm motor on 6s.

These are great discussions.

[Doby]

Agreed, size does matter.

[DPeterson]

Doby likes the really really really big gals.

[RaceMechaniX]

Guys, this is a difficult case to make for either side. First, one cannot compare engines to motors. Let's leave engine analogies out of the conversation.

If the UL-1 motor was 44mm in diameter and had the same copper mass of an LMT, but had the same power output if would last indefinitely. I think we can all agree to that. If we had no other limiting mechanism, we would have full P power. So do we make the controller the limiting factor? i.e. everyone must use the standard AQ 60A esc? It just replaces one limiting component with another, nothing gained, nothing lost.

What if we had a spec speed controller that was electrically monitoring current and limiting output but had plenty of overhead to be robust? Or similarly, we all use an inline current limiters that pull back throttle input if the current is high.

Do we mandate a battery capacity limit or mass per cell limit such as ones being used in Europe?

Not a whole lot of good answers without making significant changes.

Tyler

[photohoward1]

You didn't understand my analogy at all.

Guys, this is a difficult case to make for either side. First, one cannot compare engines to motors. Let's leave engine analogies out of the conversation.

If the UL-1 motor was 44mm in diameter and had the same copper mass of an LMT, but had the same power output if would last indefinitely. I think we can all agree to that. If we had no other limiting mechanism, we would have full P power. So do we make the controller the limiting factor? i.e. everyone must use the standard AQ 60A esc? It just replaces one limiting component with another, nothing gained, nothing lost.

What if we had a spec speed controller that was electrically monitoring current and limiting output but had plenty of overhead to be robust? Or similarly, we all use an inline current limiters that pull back throttle input if the current is high.

Do we mandate a battery capacity limit or mass per cell limit such as ones being used in Europe?

Not a whole lot of good answers without making significant changes.

Tyler

[DPeterson]

Hey Tyler.

This is not a NAMBA P-Limited thread per-say but a thread suggesting why some of us can run set ups without excessive heat build up. Knowing that you put your time in on the water rather than using theoretical engineering makes your input always welcome. I can't tell you how many times we have to over rule engineering designs while installing food manufacturing systems. Nothing replaces hands on experience with what works and what doesn't.

So far I have experienced and proven to myself and that there are others that agree, that motor mass is an important consideration when running various voltages. Whether this be for spec class or open it doesn't matter - it applies. Took a few burnt Lehner motors to find this out but Hans Lehner himself got a few of us back here in Wisconsin on the right track.

Off topic, but so far, albeit limited, the "on water" testing we have done on the TP 3630 indicates it is possible to restrict speed on the water without a "fuse - burn down" as the AQ 2030 will do. I believe it would be a most popular idea to restrict speed without a burn down. And nothing wrong with an esc going into thermo shut down. Burning equipment just does not have to happen IMO.

The smartest club I know of running a spec class in the US is in Ohio. They run a Leopard 40 something mm can for spec. I don't agree with the KV they picked but they got the motor mass size right. They have zero motor and or equipment issues. How sweet is that?

[RaceMechaniX]

Howard, I got the engine analogy however electric motors do not behave the same way engines do. My point simply being lets talk motors only.

Doug, I did not mean it to sound like a NAMBA P-Ltd discussion, but that is the most relevant motor discussion. I would argue to be competitive at a national level in a spec class we have to push the power system pretty close to its limits. Definitely there are set-ups and driving styles that yield competitive speeds with lower temps.

I could not find a good way to write an unbiased response to the discussion, so I am bowing out.

TG

[T.S.Davis]

Due to being accused for slinging BS

Could be worse. You could have been accused of proposing rules to protect record attempts of specific racers or of basing your opinions on loyalty to a sponsor. That would suck.

The guy that accused you of BS wasn't talking about your heat claims. It was the whole extra mill controversy....or the lack there of. I know this because I got the call shortly there after asking when I peed in your cheerios. hahaha Then it turns out.......... your club was just doing it screwy.

I usually choose motors that give me the largest rotor (within reason) in the KV that I want. There's obviously more to it than that but I start there. Sometimes I go a little too far on that front. At some point you can't float a monster motor. I can't put a 1527 in a 26" mono and expect it to run right. Unless I'm building a torpedo.

Nothing replaces hands on experience with what works and what doesn't.

I concur. I just went back and did the math. Between my son and I, we were turning approximately 310 laps per month in spec alone. Usually more if he was on an offshore kick at practice. Then more still if you count open boat runs. So maybe 1500 laps of spec per season. Holy crap. That's why I was confident in saying that there was a glitch in the 2030 matrix.

I'm hopeful and optimistic that the updated 2030 will be more consistent. I don't know what to make of the latest Proboat offerings. Water is a tic firm for testing up here.

What club in OH is running a Leopard spec? Are they NAMBA or IMPBA? Are they running a lot of heats that way? More info please if it's available.

[DPeterson]

Terry - You got me confused.

Where was the BS in discussing doing 1 or 2 mill laps versus the one sprint lap now being done to the start line? It was a discussion aimed at improving starts. Whether it be mill laps or the clock.

And by the way the screwy launch start at 30 seconds and below is the NAMBA system. AKA - the bad influence I referenced.

[Darin Jordan]

And by the way the screwy launch start at 30 seconds and below is the NAMBA system. AKA - the bad influence I referenced.

Should I take offense to this, since I'm the one that described it??

[DPeterson]

Terry said...
[QUOTE]Then it turns out.......... your club was just doing it screwy.[/QUOTE

Darin - check with Terry. We were using the NAMBA start. He quoted it as screwy. Not sure what you described.

Here we go again.

[dan pralle]

Just curios why the p class can't just limit the kv motor you run. Why does it have to be brand specific. P is not a rtr class it refers to motor size right?


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[Darin Jordan]

Just curios why the p class can't just limit the kv motor you run. Why does it have to be brand specific. P is not a rtr class it refers to motor size right?


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There is a BIG difference in "mass" between a 2000KV 40mm motor, and a 2000KV 36mm motor, just to use one example. The same can be said for 2-Pole vs. 4-Pole vs. 6-Pole, 50mm long vs. 60mm long vs. 73mm long, etc...

KV is such a SMALL part of the overall picture...

[dan pralle]

But the rpms are the same correct?


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[dan pralle]

So with a bigger can motor could you spin a bigger prop


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[Darin Jordan]

But the rpms are the same correct?

RPMs are the same unloaded... The ability to turn the prop under load aren't. Think torque. The motor with more torque isn't going to be "bogged down" as much, so the loaded RPM will be considerably different, given the same prop. The larger/higher-torque motor, therefore, could be prop'd with more pitch/diameter and therefore, would be faster.

[dan pralle]

So as Doug referred to motor mass would a longer motor or bigger diameter create more torque


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[photohoward1]

Yes..Just like my fuel motor analogy.

So as Doug referred to motor mass would a longer motor or bigger diameter create more torque


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[Darin Jordan]

So as Doug referred to motor mass would a longer motor or bigger diameter create more torque.

Generally speaking, yes. Remember, by "longer" or "bigger diameter", we are referring to the internal windings. The outer can diameter or length can be misleading. It's the actual core that matters. More copper, more mass, better heat capacity, improved efficiency, etc. These are very high-level explanations, and someone like Tyler could certainly get into the really nitty-gritty details, but for the purposes of what we are discussing here, these will suffice.

[dan pralle]

This is good education. You bring up efficiency. A motor that is 85% vs 95%. Does that just give you longer run time


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[Darin Jordan]

This is good education. You bring up efficiency. A motor that is 85% vs 95%. Does that just give you longer run time

I don't want to sidetrack Doug's thread too much, but hopefully he finds this all relative to the general Motor discussion.

Higher efficiency does increase run-time (less energy lost as heat). That also means more of the power is getting through the motor to the prop. Probably better acceleration, etc.

The bottom line is that KV really is just a tiny measure of what you might expect out of a motor. You have to look at a lot of more complex factors.

You might be able to get away with specifying a can size or range of can sizes, and THEN limit the KV and maybe specify a pole count. That won't help in putting limits on efficiency or internal design (rotor design, magnet shape, wire size, etc.), but it would probably get you close enough to have a good, and relatively fair race of it.

[dan pralle]

Ok I see why you need to specify a list of motors. And if your motor is running too hot that means you have too big of prop on that hull right?


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[DPeterson]

Darin - I am all in for good quality, positive and unbiased contributions on threads!!

Dan is trying to figure out how to beat us Wisconsin guy's with electric. Might be why he has so many gas boats.

[dan pralle]

Doug it's all a big learning process to keep up. Sounds like your trying to make it easier by doing the testing AND SHARING your results. And trying to make it more economical to build a boat and put more drivers on the stand.


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