Maximum Motor Size

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tmelton
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Maximum Motor Size

Post by tmelton »

How do you determine what the maximum motor size allowed for Open B is. Its displacement on and I.C. engine. What is it for electric motors?
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boiler
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Re: Maximum Motor Size

Post by boiler »

That has never been determined. An electric motor manufacturer suggested either the displacement (volume of the motor) or the weight of the motor would be the best factor. I plan to submit something to the AMA this rules change cycle. Any help from the electric gurus would be appreciated.
Bob (Longhaul) Loescher
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Dane McGee
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Re: Maximum Motor Size

Post by Dane McGee »

boiler wrote:.................I plan to submit something to the AMA this rules change cycle.
.............and the million dollar question is WHY, Bob?

Has there been a problem with electrics out performing IC in open B?



I fly 99% IC and will probably be one of the last to fully convert to total E-power (cause I've got too much good IC stuff )and I say let the electrics systems develop.

Why put a rule in place for a problem that does not exist?
Dane "Mad Max" McGee
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tmelton
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Re: Maximum Motor Size

Post by tmelton »

The horse power output of a GMS .32 engine is 1.2 H.P at 18,000 rpm

1.2 HP x 745.699872 = 894.8 watts

Its too hard to be able to tell how many watts a motor can put out unless you measure it at the field. That would be easy enough to do so maybe we would just say not to exceed 900 watts.

Another method would just be the size of the motor. A 30 mm motor average maximum watts is like about 800 watts to 1000 watts
Max watt output for a 30mm will vary alot based on the length of the motor
The normal length for the range we want is about 50mm
if you take a diameter of 30mm x a length of 50mm = size factor of 1,500

Length x Diameter not to exceed 1,500 and measured watts not to exceed 900 watts

How does that sound to all the electron experts?
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tmelton
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Re: Maximum Motor Size

Post by tmelton »

There are a few guys in our club starting to work up open b electrics. The first question they ask is whats the limit. The answer we have right now is there is no limit. The normal response is a greedy grin followed by a "really?". I am not sure it will be a problem but we should start to prepare for the future.
Buttercup
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Re: Maximum Motor Size

Post by Buttercup »

I was at lee's today, and we are looking for the best motor for open B. It is going to take about a year to come up with the money and time to test all the motors that are out there. We are finally got some open B meets this year so the testing is going to happen here.
How else is flying Open B with electrics?
Before we go for a rules change we better have a lot more info, and have a bases to submit a rule.
I agree with Max lets don't fix what isn't broken.
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Dane McGee
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Re: Maximum Motor Size

Post by Dane McGee »

tmelton wrote:..................The answer we have right now is there is no limit.

Yes there is a limit. .............Weight
Dane "Mad Max" McGee
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Ed Kettler
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Re: Maximum Motor Size

Post by Ed Kettler »

My two cents:

1. Bob, you missed the deadline, it was March 15th:
RULE PROPOSAL CYCLE SCHEDULE (Exhibit C)
Odd Years
Jan 1 – December 31 Accept basic rules change proposals. Review of proposals as they are received by the chairpersons. Publish proposals as received.
Even Years
Jan 1 – Mar 15
Accept basic rules change proposals. Review of proposals as they are received by the chairpersons. Publish proposals as received.
Apr 15 Initial vote ballots sent to contest boards.
May 1 Initial vote due at AMA HQ.
May 15 Initial vote results published
May 31 – Jul 30 Accept cross proposals. Cross proposals reviewed by chairpersons. Cross proposals published.
Aug 1 Interim vote mailed to contest boards.
Aug 15 Interim vote due at AMA HQ
Aug 30 Final vote sent to contest boards.
Sept 15 Final vote due at AMA HQ.
Sept 30 Final vote results published.
Oct 15 Generate proofs, distribute to chairpersons, do final edits
Nov 15 – Dec 31 Make final changes to rule book and publish.
2. The basic limiting factor today is weight:
3.1: Combat will be broken down into these classes:
Class ................... Maximum Weight ...........Electric Maximum Weight
A = up to .15 cu. in ......... 2.5 lbs ....................... 3.0 lbs
B = up to .30 cu. in. .......... 3.5 lbs ........................ 4.0 lbs

All airplanes will be weighed dry. Electrically powered aircraft will be weighed with batteries in place.
So, back to tmelton's original question:
How do you determine what the maximum motor size allowed for Open B is. Its displacement on and I.C. engine. What is it for electric motors?
There are no limitations on the motor as written today. The limitation for an IC is 0.30 cubic inches.
Ed Kettler
RCCA 533/AMA 3739
Ft Worth, TX
Former target tug for the best RC Combat Pilots in the World!
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tmelton
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Re: Maximum Motor Size

Post by tmelton »

Keeping the rule simple will be the challenge. Any trials in the air are subjective. Measuring RPM of a prop or output watts of a motor is as clean as you can hope to get. Physical size is the easiest to measure. If you can use the selected motors for testing outputs of different sizes to determine maximum physical size then you will probably come to a good conclusion.

The overall weight of the plane is not much of a control. You can put a lot of power into a 3 pound box. I am no expert on flying electric combat planes but given the state of the rules on the subject maybe it would be worth while to give it a go. I think I'd be able to come up with a combination that would at minimum blow away the competition in speed. Dollars seems to be the best control now. Best of luck to you guys in developing the rule.
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Dane McGee
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Re: Maximum Motor Size

Post by Dane McGee »

tmelton wrote:.............................. I think I'd be able to come up with a combination that would at minimum blow away the competition in speed.

There will be no rule for at least 2 more years, (AMA rules cycle) so in the mean time have at it my friend. :D

...................I hope you succeed, cause I will be the first to exploit it :mrgreen:
Dane "Mad Max" McGee
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tmelton
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Re: Maximum Motor Size

Post by tmelton »

We like many other clubs have a resident electric speed guru. We have put a coroplast mig in the hands of our local expert. He is not happy at less than 150mph. Let's see if he manages to make it happen. I am sure he will. We will let you know when he flys with the combat crowd in April.
Lee Liddle
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Re: Maximum Motor Size

Post by Lee Liddle »

Right now there is no limit on the power output of an IC motor in Open B either. Why doesn`t everyone (or anyone for that matter) run Jett .30s in combat?

The answer is basically cost and weight. Not may are willing to put a barstock hand built $300 in harms way or risk it being lost in the sticks after a midair. They are also much heavier than the OS 25. Using one makes it too hard to meet the 3.5lb min weight.

The same thing exists for electric Open B. In order to sustain Open B performance for a full 5 min heat requires a large motor to dissipate the heat and A LOT of batteries to supply the power. You are talking about 2.5lbs just for the power system, That leaves only 24oz for the airframe and radio.

I think the 4lb max weight is currently an effective regulation for electrics in Open B.

If there`s someone who want`s to prove me wrong, let`s see the plane. Let`s see it show an unfair advantage over a Jett .30 powered Russian style flying wing. Let`s see it win a contest or two. THEN, talk to me about limiting electric powered Open B combat planes.

As Ed has pointed out, you`ve got two whole years to do it and propose changes to the rules. That should be plenty of time.
Then if limits pass, guys will have another year or so to revamp their equipment.

One other thing. If we are going to consider some sort of watt limit for E-B. I think we should also include restrictor plates for IC motors. Fair is fair, right?
TEXAS ROCKS COMBAT HARD!!!

Lee Liddle
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Lee Liddle
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Re: Maximum Motor Size

Post by Lee Liddle »

tmelton wrote:We like many other clubs have a resident electric speed guru. We have put a coroplast mig in the hands of our local expert. He is not happy at less than 150mph. Let's see if he manages to make it happen. I am sure he will. We will let you know when he flies with the combat crowd in April.
Todd, make sure that he doesn`t weigh more than 4lbs and that he can sustain that speed for a solid 5 min heat. Then please forward all info about his power system to me immediately!! :wink:
TEXAS ROCKS COMBAT HARD!!!

Lee Liddle
RCCA #628

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Buttercup
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Re: Maximum Motor Size

Post by Buttercup »

Let's don't forget the Fora's. They are by far the fast IC motor I have every seen in open b. They are faster than what I am flying.
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boiler
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Re: Maximum Motor Size

Post by boiler »

I tried to answer Todd's question and asked for the "experts" to help in finding a fair answer. Excuse me, but I didn't intend to start a war, just some thought and research from the experienced pilots like Lee which did win the NPS in open with electrics.
Bob (Longhaul) Loescher
rcca# 621 RC Combat Geezer
Bring those planes in closer where I can see them.
[url=http://www.rccombat.net/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=11380][img]http://www.rccombat.net/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=11381[/img][/url]
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