9sec240
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naturalasperiphobic
Posts: 261
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Post by 9sec240 on Dec 21, 2009 22:37:21 GMT -5
I just got the brand new JR gyro.. the tiny G270 3D. I am going to be installing this on the Gaui 255 along with the JR DS290G tail servo. I am hoping for great things out of this gyro. I will update this post when I get it installed and tested. Attachments:
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Post by dunkonu23 on Dec 22, 2009 0:39:14 GMT -5
Cool, Ivan! Those MEM's gyros all seem to be very tiny. It's seems like tiny is thing, now. Thanks for keeping us posted!
Scott
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Post by Jerrymac on Dec 22, 2009 2:08:55 GMT -5
Wow, that thing looks really thin compared to the G770 3D on my Hurri 550.
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9sec240
Full Member
naturalasperiphobic
Posts: 261
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Post by 9sec240 on Dec 25, 2009 2:48:37 GMT -5
OK.. I got the new electronics in the 255 and took it for a test hover in the living room. Before the flight, I backed down the throttle curve to 0-70-75 and turned expo down to 15%. Before I could even get off the ground I could tell that the tail was going to be over active. I had been running 40% gain (Gear EPA) and I was getting wag even before lift off even with the lowered head speed. I kept backing down gain till I could get airborne with no wag and ended up at 15% with a tiny bit of wag every once in a while. Rudder was crazy fast. On the Hyperion servo, I had reprogrammed the servo for 45° of throw and the ball was at 6mm on the horn with the limit pot at about 80%. I was running 100% for rudder EPA. The recommendation from JR for the new G270 3D was 120% on rudder EPA and a 10mm ball for a T-Rex 250. 10mm seemed too far out so I started at 8mm. I backed the rudder EPA down to 100% and it was still too fast. 80% and still too fast. At this point, I decided to switch the dead band from zero to low and see if this would soften things up a bit. It did not seem to have any effect.
I am going to drill a hole at 6mm and hopefully this will improve things.
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9sec240
Full Member
naturalasperiphobic
Posts: 261
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Post by 9sec240 on Dec 25, 2009 16:23:41 GMT -5
I drilled a new hole at 6mm on the tail servo arm and put the ball at the new location. I adjusted the limit with the slider centered. I adjusted the throttle up 5% to 0-75-80. The tail was a bit better and less reactive but sill just did not seem right. I played with gain and it still seemed to be best at 15%. IMO, this is quite low. I clicked over to rate mode which showed that the blades are not pitched correctly for a centered slider. I decided to set it up in rate mode despite only having a single limit adjustment. I figured that a rate mode setup would bring down my slider limit and possibly help with the tail. It feels better but still will only take 17% gain.
I am going to play around with it more. Maybe swap out the stock 45mm blades for some 42mm EP200s and see if I can get gain turned up.
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9sec240
Full Member
naturalasperiphobic
Posts: 261
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Post by 9sec240 on Dec 25, 2009 17:34:21 GMT -5
I decided to drill yet another hole in the servo arm. This one appears to be 4.75mm which is basically as far in as you can get with a JR micro servo.
I now have the gyro gain up to 30% which seems to hold the tail well with minimal wag. I will see how it flies tonight in the dome. It is getting closer but I am not satisfied yet.
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Post by dunkonu23 on Dec 25, 2009 19:17:01 GMT -5
That's a lot of work, Ivan. Unless the gyro's manual states differently, I wouldn't worry about low gain as long as the tail holds. When I tested the DS760 on my BH500, I had the gain really, really low, like 10% and it was okay there. I guess it all depends on the combination. What does the manual state about ball link whole in relation to center?
Scott
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9sec240
Full Member
naturalasperiphobic
Posts: 261
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Post by 9sec240 on Dec 25, 2009 20:30:39 GMT -5
Scott, on a T-Rex 250, they state ball at 10mm. They also state 8mm for a T-Rex 450. They state that gain is best around 70%.
I will see how it flies tonight.
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Post by billmay on Dec 25, 2009 23:40:12 GMT -5
Ivan, FWIW, with my new Quark gyro I am only using a setting of 65 in my DX6i gyro menu. According to Spartan's website, the actual gain to the gyro in HH is only 77% max. for the setting range of 51 to 100 on a Spektrum/JR gyro menu. So that means I'm only sending an actual 22% gain to the gyro. I also have my ball link set a little closer to the center hub than they recommend as well. They also mention not to worry about a low gain setting as long as it works. Perhaps these newer gyros just don't require a lot of gain???
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Post by billmay on Dec 26, 2009 0:47:08 GMT -5
Ivan, I took a look at the online manual for your gyro and my interpretation of the 70% gain is that they are referring to the setting in the gyro menu so that it really represents 40% or less. Both your manual and the Spartan info also indicates that in HH mode some wag or oscillation while on the ground is normal and as long as there is no wag in the air it should be OK.
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Post by Jerrymac on Dec 26, 2009 23:45:45 GMT -5
I never get too concerned with the gyro gain numbers simply because there are too many variables to consider.
On my Hurri 550 I am using a JR G770 gyro and 890 tail servo and the gear channel for gain on a DX7. I have the gear EPA at 26% and it holds great, except during hard collective punch-outs where the tail sometimes moves right about 10 to 15 degrees but snaps right back. I could increase the gain, but it seems to hold great otherwise.
On my Blackhawk 450, I use one of those cheap Telebee gyros with an HS 50 tail servo. It holds pretty well too, but, I have the gear EPA at 115% and no wag.
So, numbers can get confusing and even then, don't really reflect the True gain. I just kinda tinker with both the mechanical set-up and the electronics set-up till I get what I want.
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