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Old Feb 28, 2014, 03:17 PM
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Bummer...not any others?
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Old Feb 28, 2014, 04:14 PM
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You could always try Googling "RC SR-71 RTF". I'm not seeing a whole lot out there.
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Old Mar 30, 2014, 01:40 PM
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Took her out for a sortie today. Winds kicked up pretty major right at the takeoff roll (naturally). The nose gear won't cycle in the air. I think the relative wind is keeping it from being able to even though it cycles fine on the ground. Wondering if I need a stronger servo or if something else is the issue? She definitely needs a gyro.

One of the mains folded on the landing. Although I landed in grass I didn't think it was a bad landing but apparently it was violent enough to break part of the gear.

That's okay. A bad day flying the Blackbird is always better than a good day at work.

SR-71 Blackbird, Windy Day (2 min 7 sec)
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Old Apr 14, 2014, 11:58 PM
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Aros,
You are not one to give up on an obsession are you? ;-}

Still have mine to maiden and thought I was ready to go....but.....asymmetric thrust issues are giving me problems. I can handle some and expect a little with most twins....but....I am at a loss as to what is going on with this one.

I have tried...
switching motors
two new ESC's
different battery packs
rebinding ...multiple times ( DX7 radio...AR7000 receiver )
running both 1 and/or 2 BEC's on stock ESC's
Different y harness for ESC's
Channel mixing
adjusting travel volumes

The power from one side to the other is very noticeable and playing with the throttle ATV, it appears to be in the 20% range. This would play havoc with this squirrely little bird on landing for sure as I have not put any active rudders in play.

I have a SU34 and an ME262 and the motors on both of these planes spool up very close together...just micro seconds apart.....not so with the SR...3-4 clicks apart on the throttle.

I found a thread with a guy flying a twin mosquito that was 5 clicks apart on sync and he fixed his issue by programming the ESC's. I have a programming card for Turnigy but it won't recognize the Detrum or the ones out of the ME262...can't remember the name...now I am trying to figure out how to do this on the SR. The SR esc's are gluled in and I don't know the manufactuer to see if there is a way to program them.../

Whoever the jerk was that assembled this plane at the factory was glue happy. They glued the motors hatch covers in place, then glued the fan housings in the nacelles...would like to get my mitts on him/her for that little screwup...

Any ideas?

Rod
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Old Apr 15, 2014, 10:01 PM
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Rod, mine's hatch covers were glued also I suspect all that came with electrics installed already were. I used a fresh X-acto blade to cut them open, carefully.

Have you calibrated the ESC's to your throttle?

Try setting your throttle stick on tx to max (with ATV set to 100%), then plug the battery into the plane... you should hear the ESC's "beep" as they configure themselves to max throttle (the motor's should NOT spin-up though... but do have a good grip on the plane anyways). Once the beeping stops move your tx throttle stick to bottom (full stop) to set the shut-off point in the ESC's. Now unplug the plane and plug it in again with your tx throttle stick at bottom and let the ESC's initialize... check to see if the motor's spin up in better sync!

This is the standard method to calibrate the throttles on all ESC's I know of. Always have a good firm grip on the aircraft when doing this, just in case!

- Michael
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Old Apr 16, 2014, 12:45 AM
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Thanks for the input...yes I have calibrated the ESCs to the throttle, many, many times but still no luck. There is just too much difference between the thrust from one motor to the other to chance flying it, especially on landing approach when one would shut down and the other is still running at approx. 20% throttle and no rudders.

I left a tech request with banana hobby to see if these 30 amp ESCs are programmable but no response yet...

I have a ME262 and a SU34 and the motors spool up extreme close together using the same radio receiver combinations, so it should not be a radio issue...not sure where to go from here except to purchase some more ESCs to try and get a matched pair....
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Old Apr 16, 2014, 06:07 AM
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Originally Posted by RCS1313 View Post
Thanks for the input...yes I have calibrated the ESCs to the throttle, many, many times but still no luck. There is just too much difference between the thrust from one motor to the other to chance flying it, especially on landing approach when one would shut down and the other is still running at approx. 20% throttle and no rudders.

I left a tech request with banana hobby to see if these 30 amp ESCs are programmable but no response yet...

I have a ME262 and a SU34 and the motors spool up extreme close together using the same radio receiver combinations, so it should not be a radio issue...not sure where to go from here except to purchase some more ESCs to try and get a matched pair....
What you are seeing is a variance in the motors or ESCs. Back in the day, resistors had a certain percentage tolerance in the spec rating. I have seen instances where two identical speed controllers ( or so I thought). Had two different spool up rates. No amount of programming or fiddling with it got them in sync. Two fresh speed controllers solved the problem. Same goes for motors. Whenever I do a twin motor setup, I try to get at least 4 motors and use the two that test closest in rpm per volt. None of these components are 100% the same off the manufacturing line so one has to be aware when it comes time to use them in multiples.
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Old Apr 16, 2014, 06:26 AM
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What you are seeing is a variance in the motors or ESCs. Back in the day, resistors had a certain percentage tolerance in the spec rating. I have seen instances where two identical speed controllers ( or so I thought). Had two different spool up rates. No amount of programming or fiddling with it got them in sync. Two fresh speed controllers solved the problem. Same goes for motors. Whenever I do a twin motor setup, I try to get at least 4 motors and use the two that test closest in rpm per volt. None of these components are 100% the same off the manufacturing line so one has to be aware when it comes time to use them in multiples.
Ya I have a lot of twins and the same thing, for the most part I've been lucky but with some it has taken a lot of work to get them in sync and a lot of spares laying around hehe. With the SR-71, I bought mine used, and at the time I had an OrangeRx laying around I hooked it up and everything was synced perfect. I later swapped out to a Spektrum AR600, and now they are out of sync. Considering that they were in sync at one point, I'm hoping I'll be able to calibrate them again to be good, but strange to me that changing the Rx had an effect. Must have reset something during binding I suppose.
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Old Apr 16, 2014, 06:43 AM
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Ya I have a lot of twins and the same thing, for the most part I've been lucky but with some it has taken a lot of work to get them in sync and a lot of spares laying around hehe. With the SR-71, I bought mine used, and at the time I had an OrangeRx laying around I hooked it up and everything was synced perfect. I later swapped out to a Spektrum AR600, and now they are out of sync. Considering that they were in sync at one point, I'm hoping I'll be able to calibrate them again to be good, but strange to me that changing the Rx had an effect. Must have reset something during binding I suppose.

Wow.... Cannot imagine why a Rx would cause that unless you split the channels and used mixing functions in the transmitter to drive two independent throttle channels. Weird stuff!
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Old Apr 16, 2014, 06:46 AM
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Wow.... Cannot imagine why a Rx would cause that unless you split the channels and used mixing functions in the transmitter to drive two independent throttle channels. Weird stuff!
It has been awhile since I did the swap, but I'm think with the old rx the throttle may have been reversed, but with the AR600 it wasn't so I may have unintentionally put it into throttle calibration mode post bind. I can't recall exactly though I haven't looked at it in several months. I'm going to start working on it again soon though as I plan to put in servoless retracts.
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Old Apr 16, 2014, 07:03 AM
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I've got three of these tucked away and servoless retracts will be in the next build. At least the nosewheel will be!
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Old Apr 16, 2014, 10:07 AM
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I was able to breathe some life into this old thread again, eh?

I bypassed the stock system completely with a couple of 45amp ESCs that I had for the SU34., including changing out y harness and upgrading to a Specktrum AR9000 rx out of my turbine Mig 15. No real improvement . I did get it to go from 5 clicks difference to 3 clicks difference on throttle. Then back to the stock ESCs AR9000rx, no luck.

Joe 1320 and Peterswolfe are starting to confirm my suspicions of mis-matched ESCs. It appears to be the luck of the draw, but two completely different sets of ESCs reacting the same way. Can't mix the individual sets as one set is 30amp and the other is a different brand and 45amp. Switching motors out made no change. Radio working perfect with ME262 and SU34 , wiring changes made no difference.....just has to be mis-matched ESCs???? And that is also a guess at this point!

Thanks for the input guys....Banana Hobbies has not responded yet to my tech inquiry...been two days!

Rod
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Old Apr 17, 2014, 01:07 PM
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It has been awhile since I did the swap, but I'm think with the old rx the throttle may have been reversed, but with the AR600 it wasn't ...
If the only thing you changed was the rx, then put the original rx back in and see if the problem goes away... if you don't have that original rx, at least try a 3rd rx and verify that the problem doesn't change. While I cannot explain why, it may be that there is something wrong with the current rx since the problem began when you put it in the plane.

A reversed throttle channel would just put the ESC's into throttle calibration mode, as per my post suggesting you calibrate the ESC's to the throttle. That should not have started nor caused this problem though.

ps. If you're waiting on BananaHobby, then you're backing up... they're not known for being at all helpful regarding the products they sell.

- Michael
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Old Apr 17, 2014, 02:32 PM
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If the only thing you changed was the rx, then put the original rx back in and see if the problem goes away... if you don't have that original rx, at least try a 3rd rx and verify that the problem doesn't change. While I cannot explain why, it may be that there is something wrong with the current rx since the problem began when you put it in the plane.

A reversed throttle channel would just put the ESC's into throttle calibration mode, as per my post suggesting you calibrate the ESC's to the throttle. That should not have started nor caused this problem though.

ps. If you're waiting on BananaHobby, then you're backing up... they're not known for being at all helpful regarding the products they sell.

- Michael
Ya, I no longer have the rx I originally used. I'll post my findings in a few weeks when I get some time to sit down and actually work on this one. And personally I'm not waiting on BH for anything, got mine used from a local guy for a great deal
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