HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old May 19, 2009, 01:14 PM
Registered User
Aberdeen
Joined Mar 2007
27 Posts
Discussion
How do the engine tests test HP?

Just wondering - do they have a proper dyno?
knukS is offline Find More Posts by knukS
Reply With Quote
Sign up now
to remove ads between posts
Old May 19, 2009, 02:35 PM
Dieselized User
gkamysz's Avatar
Chicagoland
Joined Feb 2000
7,322 Posts
Where did you see the figures quoted? Some are run on a dyno, most are not.

Greg
gkamysz is offline Find More Posts by gkamysz
Reply With Quote
Old May 19, 2009, 10:55 PM
Registered User
downunder's Avatar
Adelaide, South Australia
Joined Sep 2003
3,067 Posts
Some use a set of calibrated props, some use a torque reaction dyno while the best use an inertia dyno. Manufacturers throw darts and high score wins .
downunder is online now Find More Posts by downunder
Reply With Quote
Old May 20, 2009, 09:50 AM
Dieselized User
gkamysz's Avatar
Chicagoland
Joined Feb 2000
7,322 Posts
I don't think I've ever seen an inertia dyno used on an airplane engine. I don't think it's appropriate either. We tune airplane engines to the actual load. An inertia dyno doesn't allow that, but does represent how a car engine is used. I mean that if the needle is set correctly for 10kRPM on a four stroke, it will be far too lean for 8kRPM, let alone the 4-5kRPM the test would normal start at. It might be fun to watch though, as the engine and dyno attempt to beat each other into submission.

Last year I think I watched an ebay auction for a set of aluminum calibrated load props (Graupner or Kavan?). It went for a very reasonable price and I regret not bidding on them. Oh well, a reaction torque dyno will have to do.

Greg
gkamysz is offline Find More Posts by gkamysz
Reply With Quote
Old May 20, 2009, 10:18 PM
"Unnecessary Necessity"
coriolan's Avatar
Canada, BC, Vancouver
Joined Sep 2006
5,759 Posts
A good way to do it:http://www.mh-aerotools.de/airfoils/...erformance.htm
very precise
coriolan is offline Find More Posts by coriolan
Reply With Quote
Old May 21, 2009, 01:25 AM
Beaver Boy
rc_sjo's Avatar
Joined Nov 2001
196 Posts
Quote:
Originally Posted by coriolan
This would only allow you to measure torque (and thus power) at one speed though, as you wouldn't be 'braking' the engine until you go full throttle.
rc_sjo is offline Find More Posts by rc_sjo
Reply With Quote
Old May 21, 2009, 08:35 AM
Dieselized User
gkamysz's Avatar
Chicagoland
Joined Feb 2000
7,322 Posts
Quote:
Originally Posted by rc_sjo
This would only allow you to measure torque (and thus power) at one speed though, as you wouldn't be 'braking' the engine until you go full throttle.
That is how dynos work. Most people are interested in wide open throttle power figures, but auto engine designers spend a lot of time on dynos at part throttle settings.

To get different loads one would use different props.
gkamysz is offline Find More Posts by gkamysz
Reply With Quote
Old May 21, 2009, 11:07 AM
Registered User
Chicago
Joined Jan 2009
169 Posts
The classic model engine dyno used an eddy current brake. It could be adjusted to match the torque and the torque measured by the torque reaction using a balance. This method is very accurate and permits the plotting of torque (and hence power) against RPM.

A simple rig would be to use a generator with a variable load and a balance to measure the torque. The load would only have to handle less than 1KW for most engines. The generator would have to be able to handle 30,000 RPM or more.

A fan in a duct which can be throttled might also make a simple brake for a dyno.
unattainium is offline Find More Posts by unattainium
Reply With Quote
Old May 21, 2009, 12:53 PM
Dieselized User
gkamysz's Avatar
Chicagoland
Joined Feb 2000
7,322 Posts
All of those methods have been used for engine dynos. I don't think anyone actually dynos engines in any of the American magazines anymore.

Greg
gkamysz is offline Find More Posts by gkamysz
Reply With Quote
Old May 21, 2009, 05:42 PM
Beaver Boy
rc_sjo's Avatar
Joined Nov 2001
196 Posts
Quote:
Originally Posted by gkamysz
That is how dynos work. Most people are interested in wide open throttle power figures, but auto engine designers spend a lot of time on dynos at part throttle settings.

To get different loads one would use different props.
It may be some peoples perceptions, but unless model flying only spend their time at WOT then I think the other engine speed figures are important.

I can't remember the last time I saw a torque curve for a glow engine.............
rc_sjo is offline Find More Posts by rc_sjo
Reply With Quote
Old May 21, 2009, 07:33 PM
Dieselized User
gkamysz's Avatar
Chicagoland
Joined Feb 2000
7,322 Posts
Quote:
Originally Posted by rc_sjo
It may be some peoples perceptions, but unless model flying only spend their time at WOT then I think the other engine speed figures are important.
I don't understand. How is part throttle information useful for a model airplane? Besides if you have the WOT figure you can calculate any part throttle figure.

Greg
gkamysz is offline Find More Posts by gkamysz
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
how do I connect Whattmeter to test brushless? joey221 Power Systems 9 Jun 25, 2002 02:44 PM
How do I test for good and bad cells nigel99 Power Systems 3 Apr 28, 2002 07:16 PM
How do I test my speed controller? repo32 Electric Plane Talk 1 Sep 25, 2001 07:02 AM
How do YOU test/discharge your packs? hardlock Electric Plane Talk 2 May 28, 2001 10:02 AM
How do you test battery cell? stevesteve Beginner Training Area (Aircraft-Electric) 1 Apr 30, 2001 08:59 PM