EPA or Dual Rates which is better for set ups:  
View related threads: (in this forum | in all forums)

Tower Hobbies
Enter up to 4 keywords or Tower stock numbers
Logged in as Guest



Users viewing this topic: none
  Printable Version
       

All Forums >> RC Airplanes >> Pattern Flying >> Classic Pattern Flying >> EPA or Dual Rates which is better for set ups:
Page: [1]

Login
Message << Older Topic   Newer Topic >>
EPA or Dual Rates which is better for set ups: - 7/4/2008 1:15:40 AM   
Electriceddie



Posts: 330
Joined: 8/21/2002
From: Massapequa Park, NY, USA
Status: offline 		Hi Guys,


Some how while setting up another airplane I came across the need to limit the throw range of the servo's in order to reduce the throw of the control surface. My question is this: I always start with end point ranges set at 100% for all servos. For argument sake, lets say I have 2 inches of elevator throw up and down. I only want one inch of throw. Should I reduce the end point throw (lets say to 70%) to get the reduced range of servo travel or should I reduce the throw range at the dual rates(change the High Rate from 100% to 70% to get the shorter throw range). Another words should I reduce the range with the end point adjustment or with the dual rate percentage or a combination of both.

I actually have 100% for full throw for up and down. Should I make the following set up?


Ex. # 1
Current EPA= 100% = 2 inches up and down.
Change EPA= 80% to get one and a half inches up and down.
High Rate= 100% = 1-1/2" throw up and down.
Low Rate= 65% = 3/4" throw up and down.

or use the Dual Rates to change the throw like the following:


Ex. # 2
Current EPA= 100% = 2 inches up and down.
Leave the EPA at 100% and change the High Rate percentage:
High Rate= 70% =1-1/2" throw up and down.
Low Rate= 45% = 3/4" throw up and down.

My numbers maybe off a bit but you can see my point, I hope. You can see by my example that the end result is you get the throw range you want, but the with the second version the dual rate gets you there rather then by using the EPA.

My real question is this, is it adventageous to set it up one way over the other? Is there any strain on the servos's? Do I loose any symetrical throw of the servo arms, resulting in a sort of Expo added in etc? Is one way better then the other or is a combo of both best? Any feedback on this would be more then welcome.

Thanks a bunch

Ed


< Message edited by Electriceddie -- 7/4/2008 1:16:24 AM >

_____________________________

"GO FAST & TURN LEFT"
       Post #: 1

RE: EPA or Dual Rates which is better for set ups: - 7/4/2008 2:19:05 AM   
rainedave



Posts: 5193
Joined: 7/21/2005
From: Greensboro, NC, USA
Status: offline 		Start with the EPA's at 100% and connect the pushrods to the innermost holes on the servo arms and the outermost holes on the control horns. This is very important in order to give you the best resolution and to access the servos full torque. I can't stress this enough.

Then, using a throw meter make small adjustments with the EPA to get the desired surface throws.

The lower your EPA settings, the less servo travel you are using and consequently the lower your resolution will be. This makes for a twitchy model.

If you set up your pushrods as I described you will probably find that you will need to increase the EPA to get your desired throws (which is even better for resolution). And, your model will fly much smoother and stick movements will be more proportional to surface travel.

David

(in reply to Electriceddie)
       Post #: 2

RE: EPA or Dual Rates which is better for set ups: - 7/4/2008 2:22:40 AM   
djr1007


 

Posts: 236
Joined: 3/21/2005
From: Tucson, AZ, USA
Status: online 		I've always heard that the best thing for servos was to use their full range (this also has the added benefit of reducing sesitivity to the controls). With that said, I'd move the linkage in on the control horn, out on the servo arm until you get the amount you want with the EPA @ 100% (or better). Then you can use dual rates as they were intended to be used, not as limiters.
My 2 cents.

(in reply to Electriceddie)
       Post #: 3

RE: EPA or Dual Rates which is better for set ups: - 7/4/2008 2:24:31 AM   
djr1007


 

Posts: 236
Joined: 3/21/2005
From: Tucson, AZ, USA
Status: online 		What raindave said, only better than me (I didn't see his update until it put mine in).

(in reply to djr1007)
       Post #: 4

RE: EPA or Dual Rates which is better for set ups: - 7/4/2008 2:34:39 AM   
rainedave



Posts: 5193
Joined: 7/21/2005
From: Greensboro, NC, USA
Status: offline
quote:

ORIGINAL: djr1007

...I'd move the linkage in on the control horn, out on the servo arm...


You have it backwards. That would access the least amount of servo travel making your controls very jerky.

Ideally, you want the servo arm to move it's entire range of travel in order to move the control surface the desired distance. If you can set up your pushrods so that the full 45° of servo travel gives you your maximum desired elevator deflection you will love the way your plane responds to the sticks. It really does make a huge difference in the air.

David

(in reply to djr1007)
       Post #: 5

RE: EPA or Dual Rates which is better for set ups: - 7/4/2008 2:41:57 AM   
8178



Posts: 3031
Joined: 5/25/2004
From: _ , USA
Status: offline 		When you are using 1024 PCM how you set this up has a really big impact on the resolution.

(in reply to rainedave)
       Post #: 6

RE: EPA or Dual Rates which is better for set ups: - 7/4/2008 2:51:07 AM   
djr1007


 

Posts: 236
Joined: 3/21/2005
From: Tucson, AZ, USA
Status: online 		Dave, you are exactly right, I should learn to just keep my mouth shut and be the one learning.

(in reply to 8178)
       Post #: 7

RE: EPA or Dual Rates which is better for set ups: - 7/4/2008 3:12:39 AM   
rainedave



Posts: 5193
Joined: 7/21/2005
From: Greensboro, NC, USA
Status: offline 		djr1007, I honestly hope I didn't sound condescending. I apologize if I came across like a "know it all." I'm far from that. But, I have gotten pretty passionate about control geometry. So, please excuse my adamant approach towards it.

I have seen too many squirrelly planes at the field that could be solid, smooth and precise flying models if the pushrods were only hooked up better. I blame 3D to an extent because that style requires such huge throws and the easiest way to do it is by using long servo arms and short control horns. That's fine if you are still using all 45° of the servo's travel to achieve it. But, when you want classic pattern type throws (3/16" on ailerons, for example) setting up that way and then using EPA to get down to 3/16" is the worst thing you can do. Your tx sticks will then behave like pulse on/off switches, not proportional controls.

Thanks,
David

(in reply to djr1007)
       Post #: 8

RE: EPA or Dual Rates which is better for set ups: - 7/4/2008 4:08:47 PM   
WEDJ



Posts: 1010
Joined: 2/21/2007
From: East Haddam, CT, USA
Status: offline 		I agree. Use full servo throw, inner hole, and make your throw adjustments by the horn on the control surface.

_____________________________

Pilot dog FTW!

(in reply to rainedave)
       Post #: 9

RE: EPA or Dual Rates which is better for set ups: - 7/5/2008 2:34:44 AM   
hy flyr


 

Posts: 165
Joined: 9/20/2003
From: Rawlins, WY, USA
Status: offline 		delete

< Message edited by hy flyr -- 7/5/2008 1:42:16 PM >

_____________________________

AMA #654919
Club SAITO member #523

(in reply to WEDJ)
       Post #: 10

RE: EPA or Dual Rates which is better for set ups: - 7/5/2008 3:43:06 AM   
rainedave



Posts: 5193
Joined: 7/21/2005
From: Greensboro, NC, USA
Status: offline 		Yes, start at 100%. And, also make sure that your servo arms are the standard size, not long 3D types. Or, use the wheels instead of arms. The pushrod connection at the servo should be about 3/8" out from the center of the output shaft screw (that holds the arm on). No more, if possible. The connection at the horns should be about 1" or 1 1/8" above the control surface. Only use EPA to fine tune your throws.

David

(in reply to hy flyr)
       Post #: 11

RE: EPA or Dual Rates which is better for set ups: - 7/5/2008 7:04:17 AM   
alcarafa


 

Posts: 289
Joined: 12/11/2006
From: Merida, Yucatan, MEXICO
Status: offline 		David I guess he needs a picture to fully understand what your talking about, this happens when you are novice in pattern flying.

(in reply to rainedave)
       Post #: 12

RE: EPA or Dual Rates which is better for set ups: - 7/8/2008 3:35:29 PM   
bubbap51


 

Posts: 129
Joined: 3/19/2006
From: temple, GA, USA
Status: offline 		Here is a great article on servo - linkage setup for pattern planes. Page 3 of the article is exactly what we are discussing here.

http://www.centralhobbies.com/instructional/linkages1/link01.html

I "fixed" a friends linkage setup the other day on his pattern plane ( Intruder) and was he really surprised. I reworked the linkage and took his EPA from 29% to 106% on the ailerons and I also "fixed" the elevator. The plane flew so much smoother he was amazed. As so many people do, the linkage was in the last hole of a long servo arm and very close to the control surface on the other end. Just reverse of what we need in a pattern ship.

Bob

< Message edited by bubbap51 -- 7/8/2008 3:37:26 PM >

(in reply to alcarafa)
       Post #: 13

RE: EPA or Dual Rates which is better for set ups: - 7/9/2008 11:56:50 PM   
bjr_93tz


 

Posts: 10
Joined: 12/21/2006
From: ToowoombaQLD, AUSTRALIA
Status: offline 		There is a side issue here that hasn't been mentioned yet I think. Some computer radios use the EPA values to determine the sensitivity of the trim lever or button.

Some later radios allow the user to set the sensitivity of the trim's.

"I think" but haven't tested it mith my 7UAPS that each click of trim is worth X% of the EPA therefore you get a fixed amount of surface deflection per click of trim whether you are on high rates or not OTHERWISE your trims would change every time you changed your rates.

SO. for argument sake with all values arbitrary:
100% epa, 100% dual rates each click of trim might be worth 0.25 deg at the surface
100% epa, 70% Dual rates each click of trim might be worth 0.25 deg at the surface
70% epa, 100% Dual rates each click of trim might be worth 0.175 deg at the surface

Once again I am "sure" this is correct.....complimentary grains of salt available for the taking

(in reply to bubbap51)
       Post #: 14

RE: EPA or Dual Rates which is better for set ups: - 7/10/2008 5:47:52 AM   
rainedave