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Downline Speed - Braking - 5/18/2008 3:59 PM   
byoung466



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From: tulsa, OK, USA
Status: offline 		AXI F3A - Spin 99 20x13. My straigth downlines the plane stays contstant speed, when doing a half or 1/4 loop pull out on the bottom the plane is accelerating. I have a low throttle idle setup to 600-800 rpm. I have a brake setting of 0 20 30 on the ESC. It seems to do better if I carry some power completely through the maneuver. Curious of others exerience.

Somewhere in here I saw the spin brake settings recomended by someone for the Spin but cant find them, tried default 1st but the result was the same.

I am curious if anyone knows the brake opperating chacteritics, does it only work when throttle is pulled completely back, or does it work when changing from high speed to low speed?

Plane did the same thing on me with CC85 but its being repaired.

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RE: Downline Speed - Braking - 5/19/2008 12:30 AM   
OhD


 

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From: west hills, CA, USA
Status: offline 		I don't understand what you are saying. It sounds as though you don't like the plane accelerating during the pullout and you propose to fix it by accelerating on the downline??

If the plane is indeed at a constant speed in the downline it will probably decelerate in the pullout due to the induced drag. (Increasing the angle of attack induces lift and drag) Getting too slow on the pull out is not good and can be fixed by applying throttle during the pullout.

The brake will only work if the transmitter is set up right. You want it to engage only when the throttle stick is pulled all the way back. To engage, the pulse width must be less than the pulse width at the initial point. My initial point is set to 1.000 millisecond, my idle to 1.034 and my brake to .985. I use Idle Down (/up) to disable the brake function for some maneuvers and so I can taxi on the ground without killing the motor.

I plan to write up some instructions on setting up the 14MZ and the Spin 99 and see if the K-Factor wants to publish it. Since I got it back from Jeti I am very happy with the Spin 99.

Jim O

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RE: Downline Speed - Braking - 5/19/2008 3:01 AM   
byoung466



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From: tulsa, OK, USA
Status: offline 		Jim, the plane was accelerating to much on the downline and pull outs, getting faster than my straight line speed in other words; so I want to slow it down in the downline....instead of speeding up my straight and level to match.

I was messing some more this afternoon and changed the brake settings to increase the final strength to 50 with and increase delay between the initial brake force and final, that seems to be close to the result I need. I set an idle to 800 rpm using a trim slider, and was doing that this afternoon. So with this idle setting the brake was initiating in my down lines acheiving a more constant speed provided i pull the throttle stick back. Now my assumption since I had an idle setting is the brake activates to slow the motor from overrevving....not only at a position that would produce 0 rpm on the ground.

For the Spin someone should right instructions since Jetis suck. I haven't spent enough time yet to get the initial points and idle up setting as you have, so I using the automatic end point and have to run to full throttle to set the throttle. I would like to see an article. I like the Jeti 99, it works pretty well. When you set the idle using the spin box readings does it repeat the idleup setting rpm reliably? I find it difficult to get that accomplished sometimes with the slider. You could do a quick write up here and I'll proof it for you

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RE: Downline Speed - Braking - 5/19/2008 4:41 AM   
OhD


 

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From: west hills, CA, USA
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quote:

ORIGINAL: byoung466

Jim, the plane was accelerating to much on the downline and pull outs, getting faster than my straight line speed in other words; so I want to slow it down in the downline....instead of speeding up my straight and level to match.

I was messing some more this afternoon and changed the brake settings to increase the final strength to 50 with and increase delay between the initial brake force and final, that seems to be close to the result I need. I set an idle to 800 rpm using a trim slider, and was doing that this afternoon. So with this idle setting the brake was initiating in my down lines acheiving a more constant speed provided i pull the throttle stick back. Now my assumption since I had an idle setting is the brake activates to slow the motor from overrevving....not only at a position that would produce 0 rpm on the ground.

For the Spin someone should right instructions since Jetis suck. I haven't spent enough time yet to get the initial points and idle up setting as you have, so I using the automatic end point and have to run to full throttle to set the throttle. I would like to see an article. I like the Jeti 99, it works pretty well. When you set the idle using the spin box readings does it repeat the idleup setting rpm reliably? I find it difficult to get that accomplished sometimes with the slider. You could do a quick write up here and I'll proof it for you


Try this:


ESC Settings:

Set ESC to fixed initial point of 1.000 msec and end point to 2.0 msec
I think I went up to 60% for the final braking level.

14 MZ Transmitter Settings:

Turn off the Throttle cut and Idle down.
Set ATV to 120 on the high and 100 on the low end.
Set AFR at 100% High and Low
This should Yield something close to 2.000 msec on the high end and 1.000 msec on the low. You can touch them up with the ATV.
My high end Is 2.008 using the Jeti box to measure pulse width. (It doesn't appear to require external power when measuring pulse width)

With the Throttle Cut and the Idle Down turned off, set the low end to slightly over 1.000 and then fine tune it by setting the desired idle with the throttle trim. My throttle trim is at +19 to yield 1.034 msec

Set the Throttle Cut to 2%. When it is turned on my pulse width is 0.884 msec.

Set the Idle Down offset to yield slightly less than 1.000 msec to activate the brake. Mine is set to 61% to yield 0.985 msec.

Operation:

Turn Throttle Cut and Idle Down off.
Turn transmitter on.
Turn receiver on.
Turn Throttle cut on. ESC will arm.
Check controls and pull throttle back.
Turn Throttle Cut off and jog throttle stick to start motor.
Touch up idle. Should only need to do this once. It will be very repeatable. You will never have to touch the idle again. Just flip switches.
Turn Idle Down on. It will apply the brake and stop the motor when the stick is pulled all the way back. It will not completely stop the motor in the air.
Turn idle down off, start motor by jogging throttle stick and go fly.
Once in the air, turn Idle Down on for maneuvers that you want braking. I turn it off for things like the 45 degree down snap and a half or the plane will get too slow.

By the way, you don't want to be at full throttle on the up lines or you will slow down when you push or pull on top due to the same induced drag. Save a little power and apply it as you push/pull over.

Jim O




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RE: Downline Speed - Braking - 5/20/2008 3:57 AM   
byoung466



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From: tulsa, OK, USA
Status: offline 		Jim I have a 9Zap. Going through your setup all works pretty good.

Only different thing I came across to make it work, I had to set the throttle cut to 100% to get a similar pulse width as you resulting in .910. I had to build an idle down mix, used a 5 pt curve all flat except I picked up the end at low throttle winding up with a pulse of 1.038 for idle. I had to get to a ATV of 118% to get the 1.000 pulse for low throttle. I also have the throttle curve active, I switched TCV on and off to check if it made a difference, didn't seem to.

Everything works as you described. If just right the idle takes off w/ a flip of the idle down switch, otherwise tickle the throttle and it starts spinning.

Very cool...I will fly it tommorrow. Interested to see the result on my snaps, w/ brake active I had noticed my snaps were looking bad.

Thanks!

< Message edited by byoung466 -- 5/20/2008 4:14 AM >

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RE: Downline Speed - Braking - 5/20/2008 10:35 AM   
Scott Smith



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From: Agawam, MA, USA
Status: offline 		A slightly different approach with similar results (using a 12Z)…

I do an Idle-Up switch to start the motor and disable the brake using a programmable mix.

THR to THR linear mix (Rate A -25, Rate B 0)
Fine tuning assigned to left dial, mode /, -100%

Preflight set dial to 12:00. Flip Idle-Up switch to start motor. Fine tune desired idle with dial. (I’m at about 10:00 on the dial and a very slow idle…if I tried to start it at that position, the motor would just grind.)

I’ve been leaving Idle-Up on the entire flight until the spin entry and leave it off for landing.

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RE: Downline Speed - Braking - 6/20/2008 4:01 AM   
byoung466



Posts: 535
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Joined: 7/12/2002
Last Login: 3/10/2010
From: tulsa, OK, USA
Status: offline 		So on this brake thing. I got a raise and converted it to a 14mz.

Im thinking turn the brake off near max elevator travel on the elevator stick, and w/ the hysterisis function of the 14mz, turn the brake back on when the stick is near neutral.

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