Maximum Motor Size

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Lee Liddle
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Re: Maximum Motor Size

Post by Lee Liddle »

Thanks David. E-SSC has caught on pretty well in this area, with at least 8 pilots who flew NPS heats with E power last year.
This year my flying partner Bob Leone is giving E-B a try with me. In fact he has his stuff ready for the LSN already. I`m still working on mine. Seeing others give it a try is rewarding, but it also adds to the momentum of R&D because everyone`s stuff ends up being a little different.
TEXAS ROCKS COMBAT HARD!!!

Lee Liddle
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Thekid3418
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Re: Maximum Motor Size

Post by Thekid3418 »

Would it be acceptable to at least realize that there is a very likely possibility for battery technology to increase leaps and bounds with the advent of nano-wire batteries? Sure, they are a long way off (2-3 years likely) but if/when they do come they offer upwards of 8X the energy density of modern day lithium batteries!

For now, the overall weight limit is working well just based on the available batteries. Lithium cells are only so light, and you have to have a certain amount of them, which just so happens to line up perfectly (or near perfectly) with the AUW rule currently. This is compiled by the fact that by many reports the energy density of lithium batteries, at least based on the claims of manufacturers, is decreasing! This is because of the tendency to over-hype a certain chemistry, resulting in false claims. One of the most dense chemistries to my knowledge is the original Thunder Power Pro-Lite, whos chemistry is upwards of a decade old!

I think that if/when the time comes there are two ways that could effectively limit the electric models. The most fair, in my opinion, would be a limit on battery mass. This would limit your available energy on board. Also, you could limit the amount of watts, or more appropriately "watt-minutes" that a model can use, but this would require expensive loggers to measure, making them not very appropriate for combat.

One thing to consider, and this would take a slight investment on someones part. There is an online calculator called "babcock" I believe. It knows the prop constants for all major props, and can calculate exactly how much power a propellor takes at a given RPM to turn. We could take someone with, say, a JETT .30 and have them run it on a few different props. Taking the RPMs that we find from these tests, we could reverse the equation in babcock and figure out just how much power a JETT puts out in ideal conditions. After this, we could take that power (probably something like 1200W-1400W I would think?) and add 10% for electric motor efficiency (I think this is fair, although most motors are only 80-85% efficient, we are talking a JETT, so we should likely talk about an ideal electric motor at 90% efficiency?) and have that be the peak power allowed for an electric motor. This way, electrics are allowed to put out just as much power as the most powerful IC engine available, but they can't go off the wall powerful with the techniques listed below. For now, it would be very difficult to utilize all the power afforded by the JETT in an E plane, but times can and likely will change eventually.

For now, there is a very good gentlemans agreement that E-planes fly a whole heat. I am concerned that once someone realizes they only lose 20 points by doing it that they can discharge their batteries at a much higher rate, and just run out of power half way through the round (once most of the streamers are gone). Or, it would actually be pretty cool if someone could perfect a quick change pit stop of batteries, meaning you could discharge twice the energy, with a landing in between :o . Both of these mentioned are underhanded in my opinion, but I have no concerns of any of the pilots flying "E" right now doing this, as they are all stand up competitors in my book (although they have a unique smell of burned components :lol: ). There is a charactor that I am afraid of utilizing this technique, but I could only hope to not run across him...at least too often (again, none of the people in this discussion. I would LOVE to beat on some southerns!).

I'll conclude with a disclaimer. At this point in time, I don't see a reason to limit electric models. The AUW does a fair job limiting them to a level that is 100% competitive (in my experience). I do suggest though that with the likely improvements in the near future we at least keep an open mind to the idea of a limit on electric power some day, as that will be the only way to allow IC engines to compete.

Kid
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Ed Kettler
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Re: Maximum Motor Size

Post by Ed Kettler »

Well reasoned discussion. Don't forget the other limiter to technology adoption: cost. What has driven the dramatic growth in electric flight is the increasing power capabilities combined with declining cost and improving quality.

I can get behind a well run test program that is verified at multiple sites and delivers a set of specs that can be easily verified by the CD and other pilots, and yields a competitive solution.
Ed Kettler
RCCA 533/AMA 3739
Ft Worth, TX
Former target tug for the best RC Combat Pilots in the World!
Thekid3418
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Re: Maximum Motor Size

Post by Thekid3418 »

My only response to that would be that if we're talking about things being cost
prohibitive, then why are we considering JETTs or Foras? But I can appreciate the high cost of high performance in reference to my e-pylon models
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Ed Kettler
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Re: Maximum Motor Size

Post by Ed Kettler »

Because Gil Hernandez is flying a Fora at LSN this weekend .... :D
Ed Kettler
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Air Scharnell
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Re: Maximum Motor Size

Post by Air Scharnell »

Brian,
Your saying a pilot landed and replaced his packs, and continued the heat?
Frank S
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Thekid3418
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Re: Maximum Motor Size

Post by Thekid3418 »

Ed Kettler wrote:Because Gil Hernandez is flying a Fora at LSN this weekend .... :D
Ed, touche ;)

I'm not saying someone has landed to get a set of fresh packs. But there is some people (a person) that I am concerned of capitalizing on this technique. To do so would be much easier then refilling an IC model, as its plug and play. But I dont believe any of the active competitors would use this idea...and thats not because its over their heads ;)
Lee Liddle
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Re: Maximum Motor Size

Post by Lee Liddle »

Brian, I think you are dead on the money with all of your observations and suggestions. With your experience with hipo electrics you fully understand the weight current limitations of getting that much power for a solid 5 min. Many folks without first hand knowledge just don`t see the whole picture.

The last rules cycle, Kirk Adams submitted a RCP to reduce the AUW of an E-B ship to 3.5lbs with batteries. That`s a good example of an RCP being submitted by someone who was just wanting to over penalize E`s in Open B. That move by him took a fair amount of lobby work by me to help keep it from making it past the first vote (one more vote would have sent it forward in the rule change process).

That close call caused me to think about the option of pitting and switching batteries. Currently 4lbs work as a weight limit, and my goal is to keep working toward setups that compete well with IC on a fair and level playing field. Hopefully the guy you are concerned about will be more concerned with the long term goals of developing the electric option in Open B, instead of trying to bend and stretch the rules for short term self-benefit.

Thanks for your educated and insightful input Brian. Like I said at the top. I agree with everything that you said in your post.
TEXAS ROCKS COMBAT HARD!!!

Lee Liddle
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