killing tail servos running on unregulted 2s

[RiazP]

Hi Everyone,

I have been killing tail servos these past two weekends and wanted to get some advice on the whole HV unregulated power thing.

I am running the power bus directly from the battery and then am powering my sk720 and all my servos from the bus, I had chosen this config as it was the cleanest solution available, I have JR ds8925hv (akaDS8917HV) on cyclic, hitec HS-7954SH on throttle and the multiplex TITAN THV digi 5 HIGH SPEED (aka hitec HS-7940T) on the tail.

I have set the tail servo as being a custom servo with speed .06 1520 and 333 in the SK720. Have had basically two flights in this configuration and both occasions resulted in a fried servo! If a servo is labeled as being 2S compatible should it not be able to handle unregulated 2S?

Some have said that the servo on the tail is not up to the task of a tail servo and has therefore failed, my question is that should I have fried two servos in the space three minutes from lift off?

All the other servos are wired the same as the tail servo and have been fine. After the last failure I did touch the tail servo and found that it was hot! The other servos were quite warm but not hot.

My main question is whether I should continue trying to get this unregulated config to work, or should I just ditch the power bus and regulate voltage down to 7.4?

My good buddy thefrog feels that regulated power will provide more stable voltage through out the flight vs. the constantly dropping voltage in the unregulated configuration. What does everyone think about this and any thought on why I am killing €150.00 servos in three minutes flat? I have the logs to prove it was at 3:28 into my flight!

[thefrog]

Is it this servo?
http://www.multiplex-rc.de/en/produc...877d28f97b326e

Speed is rated at 0.04 @ 7.4v, even though it states it's 8.4v capable. Is the setup of the 1520 and 333 accurate?

[RiazP]

Thats the one, I mailed them and they confirmed the pulse rate

[georgi UK]

=] hi, not familiar with that servo or its suitability?, to lose two in the same space of time would suggest a tail step-down is needed and will allow you to retain the bus at HV for the cyclics.

I'm running unregulated with a 251 @ 5.1V on the tail, not sure how well your servo performs at a lower voltage? nothing mechanical binding here I take it?!

[RiazP]

Is the machine that you run on HV a nitro or electric? Am wondering if I should just regulate all my servos to 7.4 and be done with it? Do your servos that you run unregulated heat up a lot? I specifically bought the servo as the LHS said it could do unregulated 2S, but the proof is in the flying and neither flew!
I have, in the interim, purchased an Outrage 9188 for the tail, as this should be capable of 8.4v unregulated but wanted to know if there was any point of giving the servo a changing voltage vs. a regulated steady supply of 7.4

[georgi UK]

=] hi its electric, DS610's at 8.4V. normal servo temps. can run 4 packs with the on-board lipo. whatever you decide keep the bus in the interests of vibe reductions from servo cables.

[fusionsx00]

I run the 9188 tail servo, unregulated 2s

But I switch packs every flight on the power bus.

I stay at 8v minimum.

That servo is the best tail servo I ever had, period

[thefrog]

Why not try the 9188 unregulated and see how it handles?

[RiazP]

I am expecting the servo this afternoon, i am going to try it unregulated, see what happens, if it pops too then it is on with the 8900g regulated to 5V!

[fusionsx00]

Check you lipos voltage,
and check for any shorts to the frame.

[RiazP]

Originally Posted by fusionsx00

Check you lipos voltage,
and check for any shorts to the frame.

will do so, what voltage should i be looking for, i try to always top up the battries begfore the flight so i have around 97 or 98 % of a charge, i have routed my power wires internally on my Srimok, so when i pull the old servo i will trace all the cables and chech for any shorts

[georgi UK]

=] if I remember correctly this was a 3rd pack on the 2S its holding well for the entire flight,

[RiazP]

WOW i have an sk on a really smooth 450 and m vibes are around the 1 mark! am really jealous of two things now!!

[georgi UK]

=] Riaz that made me smile thanks!! it wouldn't bother me to see higher vibes here or voltage drops!! sometimes we hit on the right things without realising or trying too hard and it works, other times it has the opposite effect!! that's heli's for you!

[fusionsx00]

If I had 2 dead bl servos that I ran on 2s lipo
I would send them back,

But I haven't had any issues with the torq bl servos
they have served me well in 2 diffrent high power
helis,

When I first started flying helis, I wanted to save money on servos
so I got some less expensive hitechs, they didn't last and the centering
was horrible.
In the end I spent more on cheap servos than just shelling out up front.
now im running hyperion/outrage on my 255
hv jr ultra micros on the 200
and all bl outrage torq on my x5.
I haven't bought a servo in months.

[RiazP]

Hi Fusion,

Thanx for the words of assurance! I haven't read a bad thing about those servos, so I recon things should be good to go once I have it mounted