If you need assistance, please send an email to forum at 4hv dot org. To ensure your email is not marked as spam, please include the phrase "4hv help" in the subject line. You can also find assistance via IRC, at irc.shadowworld.net, room #hvcomm.
Support 4hv.org!
Donate:
4hv.org is hosted on a dedicated server. Unfortunately, this server costs and we rely on the help of site members to keep 4hv.org running. Please consider donating. We will place your name on the thanks list and you'll be helping to keep 4hv.org alive and free for everyone. Members whose names appear in red bold have donated recently. Green bold denotes those who have recently donated to keep the server carbon neutral.
Special Thanks To:
Aaron Holmes
Aaron Wheeler
Adam Horden
Alan Scrimgeour
Andre
Andrew Haynes
Anonymous000
asabase
Austin Weil
barney
Barry
Bert Hickman
Bill Kukowski
Blitzorn
Brandon Paradelas
Bruce Bowling
BubeeMike
Byong Park
Cesiumsponge
Chris F.
Chris Hooper
Corey Worthington
Derek Woodroffe
Dalus
Dan Strother
Daniel Davis
Daniel Uhrenholt
datasheetarchive
Dave Billington
Dave Marshall
David F.
Dennis Rogers
drelectrix
Dr. John Gudenas
Dr. Spark
E.TexasTesla
eastvoltresearch
Eirik Taylor
Erik Dyakov
Erlend^SE
Finn Hammer
Firebug24k
GalliumMan
Gary Peterson
George Slade
GhostNull
Gordon Mcknight
Graham Armitage
Grant
GreySoul
Henry H
IamSmooth
In memory of Leo Powning
Jacob Cash
James Howells
James Pawson
Jeff Greenfield
Jeff Thomas
Jesse Frost
Jim Mitchell
jlr134
Joe Mastroianni
John Forcina
John Oberg
John Willcutt
Jon Newcomb
klugesmith
Leslie Wright
Lutz Hoffman
Mads Barnkob
Martin King
Mats Karlsson
Matt Gibson
Matthew Guidry
mbd
Michael D'Angelo
Mikkel
mileswaldron
mister_rf
Neil Foster
Nick de Smith
Nick Soroka
nicklenorp
Nik
Norman Stanley
Patrick Coleman
Paul Brodie
Paul Jordan
Paul Montgomery
Ped
Peter Krogen
Peter Terren
PhilGood
Richard Feldman
Robert Bush
Royce Bailey
Scott Fusare
Scott Newman
smiffy
Stella
Steven Busic
Steve Conner
Steve Jones
Steve Ward
Sulaiman
Thomas Coyle
Thomas A. Wallace
Thomas W
Timo
Torch
Ulf Jonsson
vasil
Vaxian
vladi mazzilli
wastehl
Weston
William Kim
William N.
William Stehl
Wesley Venis
The aforementioned have contributed financially to the continuing triumph of 4hv.org. They are deserving of my most heartfelt thanks.
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
The pancake motor is larger diameter with lots of poles. That means it is designed for a higher torque and lower RPM than a traditional shaped motor. You would use it with a large diameter, slow turning prop to get lots of thrust at low speed, for efficient hovering.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
Steve Conner wrote ...
The pancake motor is larger diameter with lots of poles. That means it is designed for a higher torque and lower RPM than a traditional shaped motor. You would use it with a large diameter, slow turning prop to get lots of thrust at low speed, for efficient hovering.
ive not heard it so concisely stated, though ive heard what you say Steve, in drips and drabs from other sources, but i always like more opinions to avoid marketing propaganda.
this means im outside the effciancy curve im trying to aim for.
so now steve the question, harkening back to that previous thread from several months ago, i realise the calculus of mass acceleration and force trade offs, and the momentum conservation.
but now im using 430 watt motors, traditional can-type, brushless. so can i use a reducion gear train? ( and so approximate the pancake motor) or is this botching the non-ideal system even further?
the problem is the pancake form factor motors are heavy and poor in overall power output. so i see some users making a tricopter with 6 motors, 3 pairs contra-rotating, six props. All this just to get the total lift value up.
The problem is you need 6 ESCs, 6 props, 6 copper wire bundles, 6 motors, and the aditional garbage starts piling up.
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Sounds like time for a dyno experiment comparing the efficiency of a pancake motor against a regular shaped motor with a reduction gear. The gear train also adds weight and wastes some power, so I wouldn't care to say which would come out on top.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
Steve Conner wrote ...
Sounds like time for a dyno experiment comparing the efficiency of a pancake motor against a regular shaped motor with a reduction gear. The gear train also adds weight and wastes some power, so I wouldn't care to say which would come out on top.
ok, so im already building a thrust stand. Should i make a water-brake like load for a dynometer?
Registered Member #72
Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659
I'm really dubious about going doing the VPP route (which sounds rich as it's on the grounds of complexity, like my first post wasn't complex, but I' allowed to change my mind as I think through things).
A real benefit in flying machines is mechanical simplicity, less to buy, less to set up and keep in adjustment, less to replace when you crash. You know you have a good design when there's nothing left to take away.
VPP might have a small benefit over fixed pitch (like hand crafted assembler can usually be got to work faster than compiled code). But the weight of a machine will be more or less constant, or nearly so if it's consuming fuel, and as the thrust varies as the square of the prop speed, the best speed will vary over only a small range. The max efficiency band for motors, glow and electric, is not a spike but a bit of a pudding. You'd need more speed for a fast climb, and might run slightly less efficiently after dropping your Amazon parcel, but both of those are tractable costs of the simpler approach.
What I'm saying is, a VPP on a fast motor with a gearbox might be slightly more efficient than a 22 pole pancake on a fixed rotor. You can measure cost/benefit of $ and kg and minutes, but you can't measure the cost/benefit of complexity so easily. Does that mean you will ignore complexity as part of your thinking? A mantra oft repeated in the engineering circles I move in is 'a component that's not fitted is one that's guaranteed not to fail'. This affects the lifetime cost of the project, time to design, time to debug, warranty costs, unfortunately all very intangible.
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
The actual 'variable pitch prop' bit is easy to do. The 'swash plate' bit is the 'slightly tricky' bit. I've thought it through and you do need four servo's for a swashplate (possibly three, but tricky), you only need one for 'variable pitch'.
EDIT: I'll post a sketch or two if anyone's interested ( I'm away this weekend though)
This site is powered by e107, which is released under the GNU GPL License. All work on this site, except where otherwise noted, is licensed under a Creative Commons Attribution-ShareAlike 2.5 License. By submitting any information to this site, you agree that anything submitted will be so licensed. Please read our Disclaimer and Policies page for information on your rights and responsibilities regarding this site.
Novel flying machines
