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Old Oct 19, 2014, 05:18 PM
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United States, SC, North Augusta
Joined Mar 2009
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RFM prop rpm specs???

Having lost a nice model not long ago due to exceeding factory prop rpm specs (written right there on the package, but I failed to observe), I'm looking for specs for the RFM carbon fiber 17x13.

In the case of the model I lost, I was using a Aeronaut 16x10 with a warning not to exceed 9000 rpm. I was turning 9400 and after about 4 pulls at this rpm, I pitched a blade. Long story short, $1000 down the tubes.

Not wanting to repeat this process, I am looking for specs for the RFM carbon 17x13 and 16x13. I have both props but have had no luck finding any rpm limit specs.
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Old Oct 20, 2014, 02:25 AM
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United States, CA, Thousand Oaks
Joined Oct 2012
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prop rpm

Quote:
Originally Posted by john2kx View Post
Having lost a nice model not long ago due to exceeding factory prop rpm specs (written right there on the package, but I failed to observe), I'm looking for specs for the RFM carbon fiber 17x13.

In the case of the model I lost, I was using a Aeronaut 16x10 with a warning not to exceed 9000 rpm. I was turning 9400 and after about 4 pulls at this rpm I pitch a blade. Long story short, $1000 down the tubes.

Not wanting to repeat this process, I am looking for specs for the RFM carbon 17x13 and 16x13. I have both props but have had no luck finding any rpm limit specs.
I don't know written numbers, but throttle ramp can help reduce the hard hit to the hub. I have used Aeronaut props on lower power models, up to maybe 1000 watts, above that everyone here will say to stay away from them. I have run a RFM 16 x 17S at over 10,000 rpm consistently with no problems.
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Old Yesterday, 07:00 AM
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United States, GA, Atlanta
Joined Mar 2005
1,071 Posts
Aeronaut (RFM) Cam design props are only safe for power output below 1000 watts. But near 1000 wats ESC setup needs to be set to lesson stress These props are intended for mild thermal applications with low prop speed (below 8000 rpm up to 10 inch diameter max) and lower pitch numbers thus load at the prop hub mount. There are formulas to calculate safe operation prop speeds.

Here is a very general rule of thumb for fixed / folding electric props. Even if the prop is a carbon prop does not mean you can exceed this guideline without failure.

Maximum RPM=145,000/prop diameter (inches)

So for your 16" prop 9062 rpm is max, 17" prop 8500 rpm max. But if your ESC is not setup correctly you can very easily snap a blade off. no matter what material the prop is made of. A friend of mine did not have the ESC setup correctly on a Enigma F5B with RFM reinforced F5B carbon props on a RFM spinner. When he hit the switch for the third climb both props sheared clean off the spinner bolts instantly.
That was only 3000 watts on very stout blades but the ESC setup shredded them with ease.

To be honest RFM could use better documentation on their folding prop line. They are color coded, black, red, blue, green, thin blades, reinforced blades and so on. These designations indicate the construction and intended use / limitations for the type of prop. When you look on Rudi's site under F5B props these will be mostly reinforced props but can be red, or green. You will also see these props are matched to specific RFM spinners. Reinforced model props may or may not be available in the size you want to run. This is because the props offered are for setups that are used in competition. The pitch numbers of the props you are using are very low for a F5B setup for instance but seem more for a lower powered thermal glider. ESC ramp up and brake setting delays are required with most all setups. These settings are not one size fits all, they are user defined per application and unfortunately mostly derived from experience.


Rudi's site: http://www.modellbau-freudenthaler.at/

RFM Products: http://shop.modellbau-freudenthaler.at/index.php?cat=19

RFM F5B props: http://shop.modellbau-freudenthaler....hp?list=KAT162

Sharing in detail your setup and air-frame information would offer better insight for others to help you.

David

Quote:
Originally Posted by john2kx View Post
Having lost a nice model not long ago due to exceeding factory prop rpm specs (written right there on the package, but I failed to observe), I'm looking for specs for the RFM carbon fiber 17x13.

In the case of the model I lost, I was using a Aeronaut 16x10 with a warning not to exceed 9000 rpm. I was turning 9400 and after about 4 pulls at this rpm I pitch a blade. Long story short, $1000 down the tubes.

Not wanting to repeat this process, I am looking for specs for the RFM carbon 17x13 and 16x13. I have both props but have had no luck finding any rpm limit specs.
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Last edited by Jaguar22; Yesterday at 07:31 AM.
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Old Yesterday, 11:21 AM
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United States, SC, North Augusta
Joined Mar 2009
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David,

Thanks for the detail!! The ESC ramp up has never crossed my mind.

My current project is a 2.5M Spider that has one flight under its belt.

First spool up after assembly (static)
88 amps, 14.5 volts, 1276 watts static with 17x13 RFM prop (5700 rpm). TP 2700 4S/70C battery

Maiden flight: 70F ambient and windy. Under full power- 14.3 volts 88 amps=1258 amps (in flight)

Motor: hacker b50 9S 4100kv
Esc: jeti mezon 90 lite. (90A continuous / 300A bursts)

RFM 17x13 prop turns 5780 rpm in flight

Esc temp after 5 pulls= 50C

AUW= 1911g / 67.4oz (4.21lbs) less battery

I'm not looking for a rocket ship (yet) and consider this more of a warm liner. I now recognize one can still over stress equipment no matter which class aircraft you fly.

Again, thanks for sharing your knowledge. I have a 5S pack on the way (thanks Lenny) and will be back with more questions as I progress.
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Old Yesterday, 01:01 PM
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Greeley, Colorado, USA
Joined Feb 2000
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John,

You should be pretty happy (for now) with a 5S battery and 17x13 prop.
As David pointed out, some start ramp (programmed in the ESC or transmitter) will help reduce the chance of blade failure as you increase the power.

Good luck,
Lenny
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Old Yesterday, 01:52 PM
Never Stop Learning
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United States, GA, Atlanta
Joined Mar 2005
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Listen to Lenny, he knows much more about F5B setups than I do, that is for sure.

David
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Old Yesterday, 02:23 PM
2012 NZ Speedcup - 231 MPH
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New Zealand, Tasman, Richmond
Joined Mar 2006
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Quote:
Originally Posted by Jaguar22 View Post
Here is a very general rule of thumb for fixed / folding electric props. Even if the prop is a carbon prop does not mean you can exceed this guideline without failure.

Maximum RPM=145,000/prop diameter (inches)
My carbon folding electric props work up to 210,000/prop diameter.
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Old Yesterday, 07:49 PM
The Sequel
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Australia, VIC
Joined Sep 2011
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Dup, do you make any big folders?
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Old Yesterday, 07:58 PM
2012 NZ Speedcup - 231 MPH
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New Zealand, Tasman, Richmond
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The biggest is 7" but I have a 9" in the pipeline.
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Old Yesterday, 08:21 PM
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Australia, VIC
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Ok, not for this application, even 16 inch at 145,000 has motor at 60k with 6.7 gear
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Old Today, 07:58 AM
Needs to do 52 legs !!
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Verenigd Koninkrijk, Fareham
Joined Aug 2008
7,147 Posts
I second the 5S max on your setup. Should work well.

If you have a strait spinner with the nyloc nuts, no worries.

If you have an offset spinner then be sure it has the new style black bolts (the old silver ones might fail) to retain the blades and that they are properly secured in place with loctite. Check before every flight. If a bolt works it self loose, you will very soon be flying a plane with no nose.

Good luck.
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