Roger Larsen
  • Male
  • Murfreesboro, TN
  • United States
Share Twitter
  • Blog Posts
  • Discussions (31)
  • Groups
  • Photos
  • Photo Albums
  • Videos

Roger Larsen's Discussions

Alternative for large CC / CCW props

Started Jun 30, 2012 0 Replies

I've been searching online for about a week trying to find larger than 16" CF CC/CCW props, and I've pretty much given up in locating anything larger. You can find some larger 20"+ but they are…Continue

APM source code - interrupts?

Started this discussion. Last reply by Roger Larsen Jun 27, 2012. 2 Replies

I was quickly browsing over the source code for APM 2.6. I noticed that the main loop uses just some straight up timers to check for how often update routines are called and so forth. Are there any…Continue

Impossible to get 1 hour flight with current technology?

Started this discussion. Last reply by Alex gee Oct 16, 2012. 116 Replies

I've been reading about Micro Drones claim of 1 hour flight and I have been pouring over some numbers trying to figure out if this is possible with LiPo batteries. My answer is simply no. I've look…Continue

 

Roger Larsen's Page

Latest Activity

Alex gee replied to Roger Larsen's discussion Impossible to get 1 hour flight with current technology?
"Ignore the AUW and hover current, I've just realised I don't count in the battery weight..."
Oct 16, 2012
Alex gee replied to Roger Larsen's discussion Impossible to get 1 hour flight with current technology?
"I've also been looking into this.Because of the 2C max continous discharge, I'm trying to work out how many cells in parallel I need to be safe.As an example, my current tricopter will fly for ~13min (general flying about, no flips etc...)…"
Oct 16, 2012
Vishal replied to Roger Larsen's discussion Impossible to get 1 hour flight with current technology?
"I have the RC Timer 4215 650kv motors and would like to use the carbon fiber 15"x5.5 propellers mentioned in this thread. But what would be the best way to mount the propellers to the motors? These motors have a three point prop adapter so I…"
Oct 10, 2012

Developer
John Arne Birkeland replied to Roger Larsen's discussion Impossible to get 1 hour flight with current technology?
"As Brad said, getting a copter to hover with payload AUW at the ideal RPM where you have peak efficiency from both the motor and the propeller is a very large order indeed. Especially since performance curves from R/C brands can be somewhat lacking.…"
Jul 12, 2012
Jake Stew replied to Roger Larsen's discussion Impossible to get 1 hour flight with current technology?
"I recently ordered a laser tachometer.  For $12.50 it might be a pretty handy tool for working out motor and prop efficiency.  You just attach a little sticker reflector somewhere on a spinning part and point the laser tach at…"
Jul 12, 2012
Murray Spoelstra replied to Roger Larsen's discussion Impossible to get 1 hour flight with current technology?
"Interesting to note the requirement for high RPM. That might explain why the standard purple Arducopter motors seem so efficient with 10x4.7 props. Hope to see their graphs sometime or do tests myself. Also wanted to mention some links to micro…"
Jul 12, 2012
Brad Hughey replied to Roger Larsen's discussion Impossible to get 1 hour flight with current technology?
"Is everyone is starting to get the idea that the optimal matching of motors to props isn't trivial?  Then this is a great discourse. In a BLDC motor, your throttle control directly controls RPM based on the KV rating, of course. …"
Jul 12, 2012

Developer
John Arne Birkeland replied to Roger Larsen's discussion Impossible to get 1 hour flight with current technology?
"Murrau: You are of course correct that the g/W scale already takes into account motor efficiency loss. But the g/W is calculated for a single propeller, so the figures when you have two propellers stacked and down wash will most likely be…"
Jul 12, 2012

Moderator
Michael Pursifull replied to Roger Larsen's discussion Impossible to get 1 hour flight with current technology?
"be cautious with the 80% figure. motors are only 80% efficient across a narrow range of load, below that load, they can be ~65%, and above many go down to ~50%. Even though a motor/prop combo can deliver higher thrust, after that thrust curve passes…"
Jul 11, 2012
Murray Spoelstra replied to Roger Larsen's discussion Impossible to get 1 hour flight with current technology?
"I agree that 16 motors would start looking a bit like a Christmas tree. The 360-15 motor-prop combination is probably not what you need for efficiency at those weights. Hopefully someone can provide efficiency graphs for stronger motors with larger…"
Jul 11, 2012

Developer
John Arne Birkeland replied to Roger Larsen's discussion Impossible to get 1 hour flight with current technology?
"Murray: A brushless motor usually has a efficiency around 80%, so the g/W gain must be better then that. If you then consider the added weight and complexity of 16! motors I thing it would not be worth the hassle for marginal improvements in flight…"
Jul 11, 2012
Flying Monkey replied to Roger Larsen's discussion Impossible to get 1 hour flight with current technology?
"3 bladed props are not as efficient as 2.  The only reason aircraft go with 3 or more blades is because ground clearance requires it."
Jul 10, 2012
Jerry Normandin replied to Roger Larsen's discussion Impossible to get 1 hour flight with current technology?
"Or as I mentioned earlier you can go with 3 blade props.   I think it's less than a hit with coaxial props. I need stability in gusty wind.  That's why I built a heavier quad.  I'm flying around the shoreline. I would…"
Jul 10, 2012
Murray Spoelstra replied to Roger Larsen's discussion Impossible to get 1 hour flight with current technology?
"@John: If you want so much lift as well as efficiency then you could consider going co-axial on your octo. The added weight is not as much as when you add arms and the loss in efficiency of a co-axial configuration (typically 15%) would be more than…"
Jul 9, 2012

Developer
John Arne Birkeland replied to Roger Larsen's discussion Impossible to get 1 hour flight with current technology?
"Yes, but 10g/w is still just about 475g of thrust. Even with an octocopter you can then only lift 3.8kg. Barley enough for the frame and a small battery. For a octocopter with large battery, gimbal and camera you usually need about 6.5-7kg of lift.…"
Jul 9, 2012

Moderator
Michael Pursifull replied to Roger Larsen's discussion Impossible to get 1 hour flight with current technology?
"On the other hand, it's fine if you can scale up the number of motors. So long as the weight of the extra arms, ESCs, and wiring harness don't drop that efficiency down below around 10g/W, it's still a win, yes?"
Jul 9, 2012

Profile Information

Please tell us a bit about your UAV interest
For hobby / fun.

Comment Wall

  • No comments yet!

You need to be a member of DIY Drones to add comments!

Join DIY Drones

 
 
 

Groups

Season Two of the Trust Time Trial (T3) Contest 
A list of all T3 contests is here. The current round, the Drone Delivery Challenge, is here

© 2014   Created by Chris Anderson.   Powered by

Badges  |  Report an Issue  |  Terms of Service