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Old Aug 23, 2012, 05:44 PM
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Joined Aug 2010
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Can someone explain?

I have built several big electrics and have changed over to gas for awhile.....and now coming back to big electrics.

My latest mid-size electric is a 50cc size Goldwing 260. I put a Rimfire 50cc on it, Turnigy 100A HV esc, 12S/5000 zippys and noted that the watts pulled on ground were ranging from 2800-3500!!! I put my once trusty CC 160A HV on it and the watts went to 4100-4500. I had a problem with the CC cutting out at 3/4 throttle only 100amps so I sent it to CC. They sent it back, still problem so they are sending me a NEW unit to replace it. Never had problem with it until I sent it in for the "Update to ICE2 format".

I digress, my real question is: can someone explain why 12S is better for the Rimfire 65cc and the 10S is better for the 50cc? I know it is the k/v but whats the problem. I remember running the 50cc with the CC 160a and 10S/4400 and it was fine with 4000W I think. I also noticed that my 6S lipos are getting puffed and they have not had many cycles and I do not run below 3.5/cell. Yes it is hot in AZ but I fly early am, only 95F!

JB
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Old Aug 23, 2012, 08:23 PM
Jack
USA, ME, Ellsworth
Joined May 2008
16,923 Posts
The Rimfire motors are all over-rated as far as their power specifications.

Average quality brushless outrunners will typically handle an input power of 3 Watts for each gram of the motor's weight when running at their rated continuous power level. That is a power level that the motor can sustain indefinitely without overheating. And those same motors will typically handle an input power of about 25% more than that for a duration of 15 to 60 seconds when advanced to full throttle.

The Rimfire 50cc is claimed to be able to handle 4 Watts per gram continuous and 5.2 Watts per gram peak.

The Rimfire 65cc is claimed to be able to handle 4.4 Watts per gram continuous and 5.7 Watts per gram peak.

And they make similar claims for every motor in the Rimfire line. And not a single one that I have seen reports on has been able to meet those specifications in use or in objective and impartial testing. I have not seen test reports on the 50cc and 65cc but I would suspect their specs are overstated also.

Most of the reports I have read on Rimfire motors were from users who were questioning why they were unable to get the advertised power out of them. Or they were complaining about the consequences they had suffered (overheating or even damaged motors for example) in trying to use them at the advertised power levels.

We often have to figure things out for ourselves. If I were looking at the 50cc and 65cc motors and wanted to estimate their usable power, I would multiply the weight in grams by 3 for continuous power and add 25% of that for an estimate of full throttle power.

Rimfire 50cc = 1250 grams = 3750W continuous and 4688W peak

Rimfire 65cc = 1480 grams = 4440W continuous and 5550W peak

Quote:
My latest mid-size electric is a 50cc size Goldwing 260. I put a Rimfire 50cc on it, Turnigy 100A HV esc, 12S/5000 zippys and noted that the watts pulled on ground were ranging from 2800-3500!!! I put my once trusty CC 160A HV on it and the watts went to 4100-4500. I had a problem with the CC cutting out at 3/4 throttle only 100amps so I sent it to CC. They sent it back, still problem so they are sending me a NEW unit to replace it. Never had problem with it until I sent it in for the "Update to ICE2 format".
I wonder if your "cutting out" was current limiting or overheat protection pulsing the motor in the soft cutoff mode. And I have read reports of inaccurately reported (too high) power levels from the data logging of the ICE ESCs. I don't have one or know the specifics as far as which models of ICE, how much error, and if it has been resolved or if the problem has been acknowledged or addressed by CC.

Quote:
I digress, my real question is: can someone explain why 12S is better for the Rimfire 65cc and the 10S is better for the 50cc? I know it is the k/v but whats the problem. I remember running the 50cc with the CC 160a and 10S/4400 and it was fine with 4000W I think. I also noticed that my 6S lipos are getting puffed and they have not had many cycles and I do not run below 3.5/cell. Yes it is hot in AZ but I fly early am, only 95F!
The specs I looked at say they are both rated for 9-15S LiPo and props 22x8 to 26x10 (50cc) or 22x10 to 26x12 (65cc). So I don't understand your question about that. But if you did not know it, it is not save to assume that you can use the highest cell count with the largest prop in the range of suggested props. It is more often the case that the largest props require you to use lower cell counts to avoid overheating.

I would take the prop and battery I wanted to use and static test with a watt meter and checking for heat to see if it is a viable combo. If the motor was over heating and I was locked into needing to use that prop, I would want to try fewer cells. And if I already had bought the battery and wanted to use that, I would try smaller props.

Jack
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Old Aug 23, 2012, 11:41 PM
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Joined Aug 2010
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Jack, thanks for that excellent explanation! I will receive my new CC Ice 2 160a HV tomorrow. I will do static testing again with the 50cc and 12S. That is one issue, I have 8 almost new 6S/5000 30c lipos, and I want to use them on my new 1/3 scale, 30# super cub. I will try the 50cc if no luck, will try a 65cc.

JB
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Old Aug 24, 2012, 06:11 AM
Jack
USA, ME, Ellsworth
Joined May 2008
16,923 Posts
So I can see why 12S is what you're focused on then.

There is not much static testing info around on the bigger Rimfire motors so it will give you a chance to take the lead on that. Those bigger props are kind of pricey to have a bunch on hand to experiment with but if you can find the combination of diameter and pitch that will let you use those packs it would sure be nice, wouldn't it?

I don't fly anything that big but I tend to prefer flying a 1/2 to 3/4 throttle with occasional bursts when/if needed. So I'll sometimes have a prop on that won't give me much time before it will overheat at full throttle but it all works out because I don't go there much.

And some become compulsive full or high throttle users when flying at lower throttle settings might be just as enjoyable. My biggest plane has been a SIG Rascal 40 converted to electric and that flew at about 7 lbs. on a power system that had 625W at full toot. But I could throttle back in light airs and fly the pattern on 30-40W per pound. So there was plenty of fun to be had at lwer throttle settings.

Good luck with it!

Jack
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Old Aug 24, 2012, 09:48 PM
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Joined Aug 2010
164 Posts
Have an opportunity to buy an almost new Hacker A100-8 at about the same cost as 2 Rimfire 65ccs! I am tempted to buy the Hacker but I read that on 12S it is not that great, especially with my CC HV 160esc. At the Hacker price (even 1/2 retail price) I could buy a new DLE 55 or Zenoah 62cc! I think I will see if my 50cc Rimfire with my brand new CC160 will work on 12S. I have new 18, 20,24 and 27" props to try either way. I want the super cub to fly peppy scale ot ballistic like my 3D planes.
JB
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