HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Feb 17, 2013, 08:13 PM
Exodus 4:13
bhoov128's Avatar
United States, FL, Davenport
Joined May 2012
8,753 Posts
Quote:
Originally Posted by turboparker View Post
As I noted - science-based testing has clearly shown that the 2300Kv/5043 combo is the fastest combo in the Beast and Sbach airframes at lower altitudes. The 3000Kv/5030 has the edge in raw thrust. The 2500Kv motor is the worst performer of the bunch - regardless of which UMX-sized prop one puts on it, or which airframe one puts it in.

...

Joel
I wonder if a cut down 5043 to 4043 would liven up the 2500kv?

Quote:
Originally Posted by dacaur View Post
I agree. You cant get the GWS 5x3 in black or grey as well as orange. I dont know why it seems most hobby shops and web sites only carry orange....
If you want black GWS props I can go to the LHS where they have bags and bags and bags of them hanging on the wall and pick up a few and mail them to you. Or you can do it yourself, call up graves RC www.gravesrc.com and tell em you want black GWS props.
bhoov128 is offline Find More Posts by bhoov128
RCG Plus Member
Latest blog entry: Snice Slick
Reply With Quote
Sign up now
to remove ads between posts
Old Feb 17, 2013, 08:24 PM
Gopher huntin' stick jockey
turboparker's Avatar
East Bethel, MN USA
Joined Jul 2009
11,954 Posts
Quote:
Originally Posted by Bloosee View Post
Oh boy, I thought dacaur cleared it up but Joel seems to have completely contradicted everything dacaur said. I'll go with Joel's numbers as he's done all the testing. What I know now is I will try my spare 2300kv/5043 combo on the Gee Bee and see how it goes. AND try the 3000kv/5030 on the Beast. Completely ass-backward's from the way HH sells them....
Not contradicted. Just pointed out that thing's aren't that simple in the real-world because prop choice is a huge variable. With larger planes, one can choose between thousands of props with various diameters, wide ranges of pitch, and a variety of blade designs. There is never a situation with my larger planes where I can't find a prop that will optimize whatever facet of performance I wish, regardless of the powerplant, airframe type or local elevation.

In contrast - we only have the Eflite 5 x 2.75, 5.25 x 3.5, 5.5 x 2, and the GWS 5030 & 5043. Anything else requires cutting down a larger prop. Big difference, there.

Quote:
Originally Posted by bhoov128 View Post
I wonder if a cut down 5043 to 4043 would liven up the 2500kv?
I doubt it. But even if it did, it would still be the worst choice in any of the the UMX planes. A smaller prop is most definitely the last thing you'd want on any of the conventional UMX airframes. Also, smaller diameter props are inherently less efficient than larger-diameter props of similar design.

The 2500Kv motor is simply less-efficient & less-powerful than the 2300 & 3000Kv motors. It produces less useable power & draws more current in the process. There is no magical prop that will turn that frog into a princess when used in the UMX airframes.

Joel
turboparker is offline Find More Posts by turboparker
RCG Plus Member
Last edited by turboparker; Feb 17, 2013 at 08:39 PM.
Reply With Quote
Old Feb 17, 2013, 08:50 PM
Heli's rule!
dacaur's Avatar
Midvale, Utah, USA
Joined Mar 2005
8,924 Posts
Quote:
Originally Posted by Bloosee View Post
Oh boy, I thought dacaur cleared it up but Joel seems to have completely contradicted everything dacaur said. I'll go with Joel's numbers as he's done all the testing. What I know now is I will try my spare 2300kv/5043 combo on the Gee Bee and see how it goes. AND try the 3000kv/5030 on the Beast. Completely ass-backward's from the way HH sells them....
Well, as you know, or should know, nothing is absolute....

Explaining motor prop combo eccentricities could take pages and pages.

There are general rules of thumb, In general, higher kv motors are better for more speed, while lower KV motors are better for more thrust, but there are a range of props that will work with any motor, and putting a higher pitch prop on a lower KV motor can easily mean more speed than a lower pitch prop on a higher kv motor. I like to think of KV as horsepower, and prop pitch as gearing. High pitch/gearing means more speed but less power/thrust, and lower pitch/gearing means less speed, but more power/thrust.

If everything was clear and followed a fixed set of rules, we wouldn't be having this conversation, right?

The problem here that makes this case difficult is the different props, and the lack of amp draw numbers.

KV and prop size/pitch speed are not the whole picture. You need to know how much each combo draws to be able to make an informed decision. The 2300kv/5043 combo may be faster, but it may also draw significantly more amps (or it may not, i didn't see any numbers listed)

*disclamer* all numbers below are from a calculator. real world numbers will always be lower, but using calculator numbers gives an easy reference to compare. RPM's are calculated using the packs nominal voltage.

A 2300kv motor , spins 17020RPM on a 2 cell pack. A 5x4.3 prop moves the plane forward 4.3 inches with each revolution, or 73186 inches per min, or 69mph. so you could say that the 2300kv/5043 combo has a 69mph pitch speed.

A 3000kv motor spins 22200RPM on a 2 cell pack. A 5x3 prop moves the plane forward 3 inches with each revolution, or 66600 inches per min, or 63mph. so you could say that the 3000kv/5030 combo has a 63mph pitch speed.

What can we tell from that? Well, the 2300kv/5043 combo is faster. (backed up by real world testing) What it doesn't tell you is the 3000kv/5030 combo puts out more thrust. Its obvious once you understand a bit about props, but its not spelled out.

So why not put the 5043 on the 3000kv motor to get even higher speed and thrust? Because that would raise the amp draw a lot, and also lower the RPM, since its putting a higher load on the motor.

A higher pitch prop will give you a greater pitch speed, but will also put a greater load on the motor, drawing more amps to spin the same RPM.
A lower KV motor will draw less amps to do the same amount of "work" (thrust) as a higher KV motor. so why not just use a low KV motor on everything? Because you can have all the thrust in the world, but if your pitch speed is lower than your stall speed, you wont fly, hence, higher KV is needed.

In the two combos listed, the KV ratings are pretty close, which is why it goes against conventional wisdom. Comparing an 800kv motor to a 2000kv motor would be more likely to follow the "lower KV = more thrust, higher KV = more speed" rule.
dacaur is offline Find More Posts by dacaur
Reply With Quote
Old Feb 17, 2013, 09:06 PM
RCG -Minus Member
microflitedude's Avatar
United States, SC, West Columbia
Joined Oct 2009
1,441 Posts
Quote:
Originally Posted by RCBABBEL View Post
VERY!

rc
Be glad that wasn't me you did that to. You'd be dead.
microflitedude is offline Find More Posts by microflitedude
Reply With Quote
Old Feb 17, 2013, 10:07 PM
Must not buy more planes!
mclarkson's Avatar
USA, KS, Wichita
Joined Jul 2010
2,347 Posts
Yep; they're all gone. I finally talked my brother-in-law into one but he missed out and must now pay $65.

I don't know why this plane never caught on and was killed so soon.
mclarkson is offline Find More Posts by mclarkson
Reply With Quote
Old Feb 17, 2013, 10:11 PM
Exodus 4:13
bhoov128's Avatar
United States, FL, Davenport
Joined May 2012
8,753 Posts
Quote:
Originally Posted by mclarkson View Post
Yep; they're all gone. I finally talked my brother-in-law into one but he missed out and must now pay $65.

I don't know why this plane never caught on and was killed so soon.
Because it wasn't $65 to begin with
bhoov128 is offline Find More Posts by bhoov128
RCG Plus Member
Latest blog entry: Snice Slick
Reply With Quote
Old Feb 17, 2013, 10:12 PM
**I'm Battman**
RCBABBEL's Avatar
Twin Falls, Idaho
Joined Jan 2005
8,599 Posts
Quote:
Originally Posted by microflitedude View Post
Be glad that wasn't me you did that to. You'd be dead.
K Pug,

I feel guilty now.

How about a free batt from my inventory as a peace offering?
http://www.rcgroups.com/forums/showthread.php?t=1540831


rc
RCBABBEL is online now Find More Posts by RCBABBEL
RCG Plus Member
Reply With Quote
Old Feb 17, 2013, 10:14 PM
SoCal fair weather flyer
Bloosee's Avatar
United States, CA, San Diego
Joined Jan 2012
2,773 Posts
I think you actually need to fly one to be sold on it. On the shelf it looks a little like a cute toy. I think the vast majority of people would opt for an UM war bird or aerobat. Plus it was REALLY expensive at first.
Bloosee is online now Find More Posts by Bloosee
Reply With Quote
Old Feb 17, 2013, 10:14 PM
Exodus 4:13
bhoov128's Avatar
United States, FL, Davenport
Joined May 2012
8,753 Posts
Quote:
Originally Posted by turboparker View Post
The 2500Kv motor is simply less-efficient & less-powerful than the 2300 & 3000Kv motors. It produces less useable power & draws more current in the process. There is no magical prop that will turn that frog into a princess when used in the UMX airframes.

Joel
Well I'm thankful for guys like yourself and the expertise you have in these areas. I don't know even where to begin to match an airframe to a motor / prop combo, or test static thrust, or any of that stuff. I appreciate your help on the Beast thread, I picked up the 2300kv motor and a 5043 prop and it pulls like a freight train in my hand on a battery with not much more than storage charge in it (for testing / centering servos / binding purposes). So thank you sir, from all of us on rcg that get to benefit from your experience and knowledge.
bhoov128 is offline Find More Posts by bhoov128
RCG Plus Member
Latest blog entry: Snice Slick
Reply With Quote
Old Feb 17, 2013, 10:16 PM
Exodus 4:13
bhoov128's Avatar
United States, FL, Davenport
Joined May 2012
8,753 Posts
Quote:
Originally Posted by Bloosee View Post
I think you actually need to fly one to be sold on it. On the shelf it looks a little like a cute toy. I think the vast majority of people would opt for an UM war bird or aerobat. Plus it was REALLY expensive at first.
I bet you're right. The Bee Gee doesn't even look like it should fly, and unless you're familiar with old-time air racing, which not many are, you wouldn't recognize it. But who doesn't know a P-51 mustang or a Supermarine Spitfire?
bhoov128 is offline Find More Posts by bhoov128
RCG Plus Member
Latest blog entry: Snice Slick
Reply With Quote
Old Feb 17, 2013, 10:22 PM
Registered User
brushless55's Avatar
United States, CO, Longmont
Joined Nov 2011
3,526 Posts
I still need to maiden mine!
I've had the flu this week and its hard getting out
brushless55 is online now Find More Posts by brushless55
Reply With Quote
Old Feb 17, 2013, 10:39 PM
Heli's rule!
dacaur's Avatar
Midvale, Utah, USA
Joined Mar 2005
8,924 Posts
Quote:
Originally Posted by mclarkson View Post
I don't know why this plane never caught on and was killed so soon.
I would never have bought one at the original price. I have always LOVED gee-bees, and always wanted one, but not THAT bad....

But with the price drop, I bought one at $99 and a spare at $65.....

I might have paid $130, but probably not $150..... It was just too expensive for the small group of people that would buy it....
dacaur is offline Find More Posts by dacaur
Reply With Quote
Old Feb 17, 2013, 11:23 PM
Registered User
brushless55's Avatar
United States, CO, Longmont
Joined Nov 2011
3,526 Posts
I agree, I did not buy one till this big price drop!
brushless55 is online now Find More Posts by brushless55
Reply With Quote
Old Feb 18, 2013, 02:18 AM
Must not buy more planes!
mclarkson's Avatar
USA, KS, Wichita
Joined Jul 2010
2,347 Posts
I bought one almost immediately. It was, at the time, the same price as the Beast.

I've always been in love with the Gee Bee R2 (and the R3).
mclarkson is offline Find More Posts by mclarkson
Reply With Quote
Old Feb 18, 2013, 07:25 AM
LiPo-Sucker & Airframe EMT
pugsam's Avatar
Charlottesville, Virginia, USA
Joined Aug 2010
3,606 Posts
Quote:
Originally Posted by microflitedude View Post
Be glad that wasn't me you did that to. You'd be dead.
Quote:
Originally Posted by RCBABBEL View Post
K Pug,
I feel guilty now.
Oh, sure, RC...........now you say that............AFTER I already gave The Dude a ticket to Twin Falls................

pugsam is offline Find More Posts by pugsam
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Help! Adrienne Paige Gee Bee R2 Plans Eric Giorgiantonio Fuel Plane Talk 5 Jan 29, 2012 11:02 PM
For Sale Herr Gee Bee R2 (NIB) 25" wingspan pdawg Aircraft - Electric - Micro & Indoor Airplanes (FS/W) 0 Oct 12, 2011 10:20 AM
Wanted Adrian Page Gee Bee Z 1/5th and/or Gee Bee R2 1/5th (looking for) Xanix Aircraft - Fuel - Airplanes (FS/W) 0 Jul 23, 2007 06:16 PM