Go Back  RCU Forums > RC Airplanes > Scratch Building, Aircraft Design, 3D/CAD
servo calculations for giant delta >

servo calculations for giant delta

Notices
Scratch Building, Aircraft Design, 3D/CAD If you are starting/building a project from scratch or want to discuss design, CAD or even share 3D design images this is the place. Q&A's.

servo calculations for giant delta

Old 01-27-2003, 03:05 PM
  #1  
Senior Member
Thread Starter
My Feedback: (8)
 
Join Date: Jul 2002
Location: Evanston, WY
Posts: 533
Likes: 0
Received 0 Likes on 0 Posts
Default servo calculations for giant delta

I finished my scratch built eight foot Styrofoam delta wing this weekend.
On the maiden flight I discovered that the JR 517's I had on the 40x4 inch elevons do not have enough torque to pull it out of a full throttle vertical dive I slammed it in to the concrete at about a 45 degree angle and destroyed the MDS 40 I had on the front.

The plane is fine now I put on a OS 46 and replaced the JR's with some Hitec 422's. I was more gentle with it on it's second and third flight in the same day and it flys awesome. I just know that the servo's aren't going to be enough if I get in to another dive or try to recover from a spin.

Does any one know how to calculate the amount of torque I need on my elevons? Or should I just add another set of 422's so I have two servos on each elevon?


Later Jim
Old 01-27-2003, 07:45 PM
  #2  
Senior Member
 
mulligan's Avatar
 
Join Date: Apr 2002
Location: Sanford, FL
Posts: 1,147
Likes: 0
Received 0 Likes on 0 Posts
Default servo calculations for giant delta

http://www.multiplexrc.com/calcservo.htm

- George
Old 01-28-2003, 01:57 AM
  #3  
Senior Member
My Feedback: (5)
 
Soar Head's Avatar
 
Join Date: Feb 2002
Location: x, AK, AFGHANISTAN
Posts: 147
Likes: 0
Received 0 Likes on 0 Posts
Default servo calculations for giant delta

I tried to look up the specs on your servo but could find none on the Horizon site. If these are standard servos, I find it hard to believe you could overdrive one.

Of course, you said you were in a screaming dive.

The design of your linkage has a lot to do with how much of the effective torque of the servo reaches the surface. In brief, use as short of a linkage on the servo arm as you can get away with. Of course, long enough to move the surface. If you move your pushrod too far out on the servo's rod, you're just making it work harder for no gain. Try this on the servo calculator below.

I have used this one over and over. It will even help you design your linkages.

http://www.pongo-air.com/servotorque.html

That said, this spreadsheet is more complex to use than the Multiplex one.
Old 01-28-2003, 04:05 AM
  #4  
My Feedback: (10)
 
klhoard's Avatar
 
Join Date: Sep 2002
Location: Collierville, TN
Posts: 1,289
Likes: 0
Received 0 Likes on 0 Posts
Default servo calculations for giant delta

Once you enter the "screaming dive" regime of the flight envelope, there about 45 other things that can go wrong and not allow your plane to pull out - i.e. flutter, control surfaces twisting, connections bending, ect., ect. . . .
I had a Bridi Escape - piped Hanno .60, really high wing loading (due to too much epoxy paint), retracts, average speed right around Mach 2. . . anyway, I used two FMA mini servos on the elevator (one on each half) and they worked very well thru many, many 6G pullouts and pattern flights.
With 4 inch ailerons, I would first look to see if they are twisting along their length. Remember that the force of air increase with the **square** of the velocity. . .
Old 01-28-2003, 02:29 PM
  #5  
Senior Member
 
Join Date: Dec 2001
Location: FL
Posts: 7,769
Likes: 0
Received 5 Likes on 5 Posts
Default servo calculations for giant delta

Another solution is to use boost tabs. Make them about 8 to percent of the area of the movable surface and set them up to always stay parallel to the fixed surface.
Old 01-28-2003, 08:24 PM
  #6  
My Feedback: (7)
 
ridietz's Avatar
 
Join Date: Jun 2002
Location: Clayton, IN
Posts: 97
Likes: 0
Received 0 Likes on 0 Posts
Default Servo Torque

I also need to determine servo torque requirements, but cannot get response from http://www.multiplexrc.com/calcservo.htm, or connect to http://www.pongo-air.com/servotorque.html.

Mulligan and Soar Head, can you check these and advise.

T hx.
Old 01-28-2003, 08:32 PM
  #7  
Member
 
Join Date: Jan 2003
Location: The netherlands
Posts: 72
Likes: 0
Received 0 Likes on 0 Posts
Default servo calculations for giant delta

Whats a "scratch" or something :S?
Old 01-28-2003, 09:03 PM
  #8  
Senior Member
Thread Starter
My Feedback: (8)
 
Join Date: Jul 2002
Location: Evanston, WY
Posts: 533
Likes: 0
Received 0 Likes on 0 Posts
Default servo calculations for giant delta

/Whats a "scratch" or something :S?/

DutcheR

That means I designed and built it with out plans.

Later Jim
Old 01-29-2003, 02:38 PM
  #9  
Senior Member
 
mulligan's Avatar
 
Join Date: Apr 2002
Location: Sanford, FL
Posts: 1,147
Likes: 0
Received 0 Likes on 0 Posts
Default servo calculations for giant delta

Both links work for me.

- George
Old 01-29-2003, 02:45 PM
  #10  
Senior Member
Thread Starter
My Feedback: (8)
 
Join Date: Jul 2002
Location: Evanston, WY
Posts: 533
Likes: 0
Received 0 Likes on 0 Posts
Default servo calculations for giant delta

Here is some pictures
Attached Thumbnails Click image for larger version

Name:	51186_11561.jpg
Views:	12
Size:	65.9 KB
ID:	31340  
Old 01-29-2003, 02:46 PM
  #11  
Senior Member
Thread Starter
My Feedback: (8)
 
Join Date: Jul 2002
Location: Evanston, WY
Posts: 533
Likes: 0
Received 0 Likes on 0 Posts
Default servo calculations for giant delta

gear
Attached Thumbnails Click image for larger version

Name:	51187_11561.jpg
Views:	14
Size:	66.2 KB
ID:	31341  
Old 01-29-2003, 02:46 PM
  #12  
Senior Member
Thread Starter
My Feedback: (8)
 
Join Date: Jul 2002
Location: Evanston, WY
Posts: 533
Likes: 0
Received 0 Likes on 0 Posts
Default servo calculations for giant delta

landing gear
Attached Thumbnails Click image for larger version

Name:	51188_11561.jpg
Views:	12
Size:	68.1 KB
ID:	31342  
Old 01-29-2003, 05:14 PM
  #13  
My Feedback: (10)
 
klhoard's Avatar
 
Join Date: Sep 2002
Location: Collierville, TN
Posts: 1,289
Likes: 0
Received 0 Likes on 0 Posts
Default servo calculations for giant delta

You have some very long pushrods going to the elevons, and with the control horns at the very end of those 40x4" ailerons, the inflight air loads can twist the elevons and bend the pushrods making you think the servos don't have enough uumph.
If you move the servos closer to the elevons to shorten up the pushrod, and also have them drive the center of the ailerons, I'm sure that the servos you have now will do just fine.
Old 01-30-2003, 02:31 AM
  #14  
Senior Member
My Feedback: (4)
 
Goggles's Avatar
 
Join Date: Dec 2001
Location: Abbotsford, BC, CANADA
Posts: 1,026
Likes: 0
Received 0 Likes on 0 Posts
Default servo calculations for giant delta

I've heard that you need 1oz torque per 1sq. inch on the control surface........I don't know???
Old 01-30-2003, 01:33 PM
  #15  
Senior Member
My Feedback: (5)
 
Soar Head's Avatar
 
Join Date: Feb 2002
Location: x, AK, AFGHANISTAN
Posts: 147
Likes: 0
Received 0 Likes on 0 Posts
Default servo calculations for giant delta

I tried the link I posted today, and had problems too. Here's another link that works.

http://www.geistware.com/rcmodeling/calculators.htm

If you want to search out the net use Google and search for servo torque.

If you want to find this particular spreadsheet, try searing on servo torque tenney. Craig Tenney being the author of the spreadsheet.

Sorry for the bad link.

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are On


Thread Tools
Search this Thread

Contact Us - Manage Preferences Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.