Real world RPM

[KrisW]

Witnessed: DA-150 w/mtw110 canisters, Mejzlik 28.5-12 3 blade: 5850 rpm

DA-150 w/KS 1090 pipes, Biela 29-12 3-blade: 5900 rpm
DA-150 w/KS 1080 pipes, Biela 30-12 3-blade: 5450 rpm

TOC 150 w/Pefa LL canisters, Biela 30-12 3-blade: 5350 rpm
TOC 150 w/Pefa LL canisters, Fuchs 33-12 2-blade: 5300 rpm
TOC 150 w/Pefa LL canisters, Mejzlik 32-10: 6250 rpm

TOC 140 w/Pefa LL canisters, Mejzlik 32-10: 6100 rpm
TOC 140 w/Pefa LL canisters, AirModels 31.5-11: 6300 rpm
TOC 140 w/Pefa LL canisters, Fuchs 27.5-13 3 blade: 5800 rpm
TOC 140 w/supersonic mufflers, Mejzlik 32-10: 5500 rpm

[Jim Woodward]

	Quote: Originally Posted by rcign
	Just for kicks turn the snorkel around, use a longer piece of tubing to connect it...Check the rpms on the ground... You might be surprised....

I ran my 3W 170 with the snorkel pointing forward. Also two other friends have done this on their Extras, and the throttle response was greatly improved, with a bit more power too.

A self perported expert tried to tell me that running the snorkel forward would damage the reeds, that the reeds were not meant to take forced "ram-air" induction. I tried to explain the aerodynamics involved and that in fact it was not "ram-air", rather "fresh" air it was getting, but he didn't get it. 3W put a lot of engineering into the snorkel. The opening hole is small, then the chamber expands which acts similar to a stilling chamber in a wind tunnel, to slow down air velocity.
thanks,
Jim

[rcign]

The 157 I tried it on picked up 200 rpm on the test stand...

[as722]

cox .049 apc 6x3 lots of rpms


Albert

[krayzc]

Jim,

"A self perported expert tried"

Lots of those are out here

[2robinhood]

CRRC Pro GF26I ( 26cc )

Xoar 16 X 8 @ 8500 rpm

SY 16 X 8 @ 8900 rpm

Xoar 17 X 6 @ 8500 rpm

APC 17 X 6 @ 9400 rpm

Xoar 17 X 8 @ 7600 rpm

Xoar 18 X 6 @ 7800 rpm

APC 18 X 6W @ 8050 rpm

Xoar 18 X 8 @7400 rpm

The best performance on my 11 lb. 2 oz. Seagull Laser 200 is the:
SY 16 X 8 and the APC 17 X 6.

[KrisW]

	Quote: Originally Posted by rcign
	The 157 I tried it on picked up 200 rpm on the test stand...

200 rpm equals how much horsepower?

[2robinhood]

I was getting some PM's about the SY prop that I was using on my CRRC Pro GF26I.
8900 rpm
It is a simulated carbon fiber composite prop.
Shape is simular to an APC, but it is shaped a little different.
Most like the APC W series props.
I really like it.
Gasoline will not hurt the carbon fiber finish, but I heard glow fuel witll mess it up.

[BTerry]

	Quote: Originally Posted by KrisW
	200 rpm equals how much horsepower?

RPM-to-power is a cubic relationship, so the power increases with the third power of the RPM increase. This 200 rpm increase is about a 10% increase in "power", or about 1.2 hp increase.

[soarrich]

BT

Can you explain that to some one that was socially promoted out of high school like me? Like a formula for figuring it out. I've always known that extra 200 rpm was hard to get, but a formula would be appreciated. Pe Reivers, on his website, has a Excel spreadsheet that works well, but I'd like to see the math.

[dick hanson]

	Quote: Originally Posted by soarrich
	BT Can you explain that to some one that was socially promoted out of high school like me? Like a formula for figuring it out. I've always known that extra 200 rpm was hard to get, but a formula would be appreciated. Pe Reivers, on his website, has a Excel spreadsheet that works well, but I'd like to see the math.

The horsepower increase was based on a known load . a 200 rpm increase on a tiny glow emgine would not give this much power increase.
I know nothing about math- other than to notice anytime numbers are flouted about - be careful--just like discount figures on used car purchases - -it is easy to get lost.
But-- in real world -power statements -(horsepower ) start with torque which is a force - .Time is added to this force and expressed as horsepower. for us-it is typically rpm -revolutions per minute
So-- a load , moved at a known speed is horsepower.
moving a load faster takes more horsepower
Example : to double the speed takes four times the horsepower.
You have heard that of course - a car which goes 100 mph takes 4 times as much power to go 200 mph-
The charts developed for propeller loads are good to bad - Pe's chart is good
some are bad
yo have to factor in variables such as air density.
I hate math so don't ever ask me for a chart.

[soarrich]

	Quote: Originally Posted by dick hanson
	I hate math so don't ever ask me for a chart.

I know the feeling. Pe's spreadsheet from what I've seen is pretty good at matching rpm to thrust with specific props, thank God for guys with sliderules.

[sprice50]

Can someone post a link to the chart or perhaps just post the chart.

[rdb127]

http://www.mvvs.nl/

Go to propellers and click on the propeller power calculation sheet. Its good stuff....now if only he could add Vess props in there.

[soarrich]

I've found that for the Vess 22A and 23A the 1.27 prop constant to be good. I don't think I tested with a B Vess yet.