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600 PRO Class Electric Helicopters 600 PRO Class Electric Helicopters manufactured by Align, Tarot, SYMA, Airhog, Chaos, HK and similar. |
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01-15-2015, 04:01 AM | #1 (permalink) |
Registered Users
Join Date: Jan 2015
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Spools up with Throttle Hold OFF!
With apologies if I'm going over old ground - I did try searching but had only limited success in relation to my problem. The related topics I have seen seem to support what I think happened but I would like to know if this is a known problem or if anyone has any further suggestions?
I have a 600e Pro (with old style head not DFC) that I bought second hand but barely flown. I fitted a Skookum SK450 and Spektrum satellite receiver and am using a new Spektrum DX7S. I followed all the wizards with the Skookum and also set up the DX7S to give Throttle Hold and Idle up with three speeds (30%, 70% and 100%). In normal I have the default 0, 25, 50, 75, 100% Throttle curve and the Pitch curve is set at 40, 45, 50, 75 and 100% in normal and 0, 25, 50, 75, 100% in Idle Up. I should add this is my first Heli but I have been flying multirotors for some time (including rate mode which I understand is similar to the way a Heli behaves). I flew it for the first time last week and was OK but when I touched down the tail blade hit the dirt and I stripped the drive gear. I subsequently found this is a problem with the Pro version with low landing gear so fitted the higher landing gear at the back to lift the tail by around 2" as others have done. Having replaced the stripped gear I took it out for its second flight today but took someone's advice to switch Throttle Hold on before powering up the heli (hadn't done that before). Once powered up, as soon as I turned off the Throttle Hold it spooled up and nothing I did could stop it (including turning off the transmitter) until I turned Throttle Hold back on. Long story short, I also stripped the new tail drive gear. From what I have read and my own observations the Throttle Hold on the DX7S actually sets a negative value for the throttle (-19%). I believe that by powering up with Throttle Hold ON it effectively recalibrated the ESC to take -19% as the zero point and thus turning Throttle Hold Off (or turning the transmitter off to put the SK450 into failsafe) thereby setting the throttle to 0% which is higher than the perceived minimum point and hence it spools up. When testing before I did test the Throttle Hold was working but not until after everything was powered up and working. The Throttle Hold default position is 0% which actually outputs as -19% so I have increased it to 33% which outputs 0%. Checking the commanded position on the Skookum setup software switching Throttle Hold On now sets the throttle to 0%. I have tested on the bench and everything behaves as I expect. Throttle Hold stops the motor, in normal mode the stick controls the throttle from 0 to full power and Idle up sets 30%, 70% and 100% depending on switch position. I can now power up with Throttle Hold On and it still behaves correctly. Have I got this right? Would this have been the problem? Any other recommendations? Thanks |
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01-15-2015, 04:08 AM | #2 (permalink) |
HF Support
Join Date: Sep 2006
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Sounds plausible. I always set my TH at 0% flat line and then it is at the same position as the low stick position set on the ESC.
After repairs or,rebuild its not a bad idea to do a blades off spoolup to check,everything is OK
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John |
01-15-2015, 04:19 AM | #3 (permalink) |
Registered Users
Thread Starter
Join Date: Jan 2015
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Thanks John, I did do a check without blades after the repair but as it didn't have the blades fitted I didn't put it into Throttle Hold when I powered up.
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01-15-2015, 01:38 PM | #4 (permalink) |
Registered Users
Join Date: Aug 2011
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Your instinct was to turn off the transmitter instead of flipping the switch you had just flipped again?
You got lucky. Some transmitters do have a throttle hold value that is negative which can cause similar behaviou. Go to the "monitor screen" and put your stick at zero throttle, then flip throttle hold on and off. This will tell you everything you need to know. If the triangle moves, then throttle hold has a different value than 0 |
01-15-2015, 08:29 PM | #5 (permalink) |
Registered Users
Thread Starter
Join Date: Jan 2015
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No, jmtyndall, my instinct was to switch the Throttle Hold On again which is what I did and of course it stopped spinning. I checked my transmitter settings again then turned Throttle Hold off and on a couple of times to verify it was spooling up as soon as I turned it OFF. I then started trying to find out why it was suddenly behaving like that and power cycled the main power, electronics power and finally Transmitter power and all made no difference to the behaviour. I didn't "Get lucky" as you say.
Only when I got home, did some research and then looked at the 'Throttle Cut' display did I find the known problem with negative throttle with the Throttle Hold switch. |
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