SMALL - espritmodel.com SMALL - Telemetry SMALL - Radio
Reply
Thread Tools
Old Jun 29, 2004, 02:09 AM
Suspended Account
ni'ihau
Joined Nov 2003
3,241 Posts
Idea
contra rotating prop brushless

I had this great idea this afternoon. and it works
Eljimb0 is offline Find More Posts by Eljimb0
Reply With Quote  (Disabled)
Sign up now
to remove ads between posts
Old Jun 29, 2004, 02:18 AM
Suspended Account
ni'ihau
Joined Nov 2003
3,241 Posts
The drive shaft for the back rotor is inside the front rotors prop. I found a pair of opposite pitch props as a replacement part for one of those aero wanker birds with two motors. ONE cc phoenix 10 drives both motors.
Both motors start about 1/2 the time the other half one or the other starts only. It makes a wonderfull sound. I don't know how to read the prop rpm?
do I set the tach for 4 blades or 2. It rips all the way to WOT.
jimbo
Eljimb0 is offline Find More Posts by Eljimb0
Reply With Quote  (Disabled)
Old Jun 29, 2004, 02:24 AM
Good Better Best quest.
olmod's Avatar
Australia, VIC, Cranbourne East
Joined Apr 2004
10,512 Posts
wow

That looks great you have to do an in depth on the build ,ive had a play with back to backs and 2 on a common shaft but that a great inovative application just think no torque reaction no fuz twist and the dreaded wing tuck under. are they standard winds? some motor tests would be great also.
olmod is offline Find More Posts by olmod
Reply With Quote
Old Jun 29, 2004, 02:37 AM
Registered User
ed_khan's Avatar
USA, WA, Bellevue
Joined Dec 2002
317 Posts
It actually works
Please do post some more pics, especially how the two shafts tie up!
Goof luck
ed_khan is offline Find More Posts by ed_khan
Reply With Quote
Old Jun 29, 2004, 02:45 AM
Suspended Account
ni'ihau
Joined Nov 2003
3,241 Posts
The motors are from mini disc players (17mm. dia stator) For the sake of simplicity and speed I used the stock winds on the motors (I knew they would be the same).I cut the aluminum mount up and ca glued it to the back of another
Eljimb0 is offline Find More Posts by Eljimb0
Reply With Quote  (Disabled)
Old Jun 29, 2004, 02:45 AM
Registered User
Mats's Avatar
Trollhattan, Sweden.
Joined Oct 2002
186 Posts
T(w)ooCool! *all thumbs up*
Mats is offline Find More Posts by Mats
Reply With Quote
Old Jun 29, 2004, 02:55 AM
Suspended Account
ni'ihau
Joined Nov 2003
3,241 Posts
this is how the drive shaft works
Eljimb0 is offline Find More Posts by Eljimb0
Reply With Quote  (Disabled)
Old Jun 29, 2004, 02:55 AM
Registered User
WimH's Avatar
Belgium, Flemish Region, Oosterzele
Joined Dec 2001
5,461 Posts
Quote:
Originally Posted by Eljimb0
I had this great idea this afternoon. and it works

This is one I saw @ Aspach 2002:

WimH is online now Find More Posts by WimH
RCG Plus Member
Latest blog entry: That elusive thermal...
Reply With Quote
Old Jun 29, 2004, 04:50 AM
Registered User
CANTZ506's Avatar
Brescia, Italy
Joined May 2004
784 Posts
Very good job jimb0!
Have I any chance to find a slow flyer inverted pitch prop somewhere? I'm thinking about a twin, with counter rotating engines, but I've never seen an inverted pitch prop in any catalogue.
Thanks, Piero.
CANTZ506 is offline Find More Posts by CANTZ506
Reply With Quote
Old Jun 29, 2004, 05:47 AM
Good Better Best quest.
olmod's Avatar
Australia, VIC, Cranbourne East
Joined Apr 2004
10,512 Posts
Jimbo

How about a black line on the rear drum to get the RPM ? mmm could fit one into a delta pusher , was there any make and model number on the units you salvaged ? is there an optimum distance between the props ? I wonder if it related to the air foil of the props. you got my attention
olmod is offline Find More Posts by olmod
Reply With Quote
Old Jun 29, 2004, 07:06 AM
Senior Member
Finland
Joined Feb 2001
584 Posts
Quote:
Originally Posted by Eljimb0
ONE cc phoenix 10 drives both motors.
Both motors start about 1/2 the time the other half one or the other starts only. It makes a wonderfull sound. I don't know how to read the prop rpm?
do I set the tach for 4 blades or 2. It rips all the way to WOT.
jimbo
Thumbs up to your efforts! Highly interesting.

If I may suggest further tests, it would be interesting if you could hook up another cc phoenix 10 and measure how much less current the rear motor draws in %. Then you could vary the speed of motors to see how much difference you need to cancel out all the torque -I would think holding a mounting in a hand (safely!) would tell you by feeling if there is a a measurable difference. Static thrust tests would be interesting as well -compared against the thrust by only one motor running.

RPM measurement: set you tach to 4 blades, it gives you the rpm of each motor (4 blade result multiplied by two divided by two). Since they run out of one ESC, the rpm is synchronized but current must be different.
Petri Nygren is offline Find More Posts by Petri Nygren
Reply With Quote
Old Jun 29, 2004, 08:38 AM
CD-ROM Junkie
Art Newland's Avatar
Camas, Washington, USA
Joined Apr 2001
13,859 Posts
That's awesome Jimbo,
I like the way you think! Must be a common thing to banjo pickers!
Art Newland is offline Find More Posts by Art Newland
Reply With Quote
Old Jun 29, 2004, 08:44 AM
Registered User
Joined Apr 2002
1,860 Posts
Quote:
Originally Posted by Eljimb0
The drive shaft for the back rotor is inside the front rotors prop. I found a pair of opposite pitch props as a replacement part for one of those aero wanker birds with two motors. ONE cc phoenix 10 drives both motors.
Both motors start about 1/2 the time the other half one or the other starts only. It makes a wonderfull sound. I don't know how to read the prop rpm?
do I set the tach for 4 blades or 2. It rips all the way to WOT.
jimbo

??? Tried Googling, what are they?
Robert May is offline Find More Posts by Robert May
Reply With Quote
Old Jun 29, 2004, 02:16 PM
Suspended Account
ni'ihau
Joined Nov 2003
3,241 Posts
aero wanker birds ;
Hobby Zone- "firebird outlaw"
two props 4X4? $2.50 US. Part number HBZ 4540 Horizon Hobby
jimbo
Eljimb0 is offline Find More Posts by Eljimb0
Last edited by Eljimb0; Jun 29, 2004 at 02:23 PM.
Reply With Quote  (Disabled)
Old Jun 29, 2004, 02:41 PM
Suspended Account
ni'ihau
Joined Nov 2003
3,241 Posts
Thanks for the compliments all.



"If I may suggest further tests, it would be interesting if you could hook up another cc phoenix 10 and measure how much less current the rear motor draws in %. Then you could vary the speed of motors to see how much difference you need to cancel out all the torque -I would think holding a mounting in a hand (safely!) would tell you by feeling if there is a a measurable difference. Static thrust tests would be interesting as well -compared against the thrust by only one motor running."
Peter
I will do a bunch of test on this thing after I get some sleep. The project from idea to product took about 10 hours most of that time should have been spent "counting sheep" .


With regards to RPM; because the props blades cross each other 4 times per
cycle the tach numbers wouldn't hold still. I figured it out at 10,000 rpm WOT
Eljimb0 is offline Find More Posts by Eljimb0
Reply With Quote  (Disabled)
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Question Contra-rotating vs. single prop? stangrob Power Systems 7 Nov 21, 2006 08:44 PM
Contra-rotating prop units? Angelo Scale Kit/Scratch Built 2 Feb 19, 2005 06:35 PM
Counter-rotating prop? f2racer Electric Plane Talk 1 Sep 01, 2002 08:00 AM
Rotating Can Brushless Motors bps Electric Heli Talk 4 May 30, 2002 06:31 PM
contra rotating blades help........pls! Devilfreak Electric Heli Talk 5 May 13, 2002 01:01 AM