yeahbaby

My Feedback: (21)

Gents

any of you boys keep track of your mah draw per flight on your SM F4?

i want to set my baseline usage rate so i know if I've got some binding or overworked servos while airborne. I used an in-line amp meter when setting up the surfaces and felt good with my overall usage but in talking to a few 100lb heads out there we've discovered perhaps a few servos are working too hard. I've identified the flaps as the primary culprit but think the single 8711 working the stab might be hungry in flight.

what kind of numbers are you guys seeing? per flight in between charge or average usage between charge cycles. either will work.

i'm just trying to figure out where my set up is in relation to others.

i've got two 3000man Nimh packs feeding the airborne system via two spectrum regulators. (the ones with the cooling fans etc. yes I know I'm a dork but they were just too cool "no pun intended" to not use)

thanks for the help fellas. i've been smiling all week.

buck

JetsRC

Are you saying you are using only one 8711 for the complete elevator system? I would strongly suggest you go to two 8711 for the elevator, or two 8611 will also work.

Ehab

My Feedback: (44)

Yes, use two elev servos. I believe Raffy "may" have lost his SM F4 due to one elev servo...

yeahbaby

My Feedback: (21)

yeah gents i put one 8711 back there. 400+ oz of torque seemed like plenty to me, but now i'm beginning to think otherwise.

I used 600+ mah per pack!! after my 2nd flight. Initially i thought that seems high but it's got lots of servos and i've never used an 8711 before (assumed to be largest culprit).

the first flight had higher numbers and although i've got them in the back of my mind,but i'm not considering them because it included all the pre-flight checks, taxi, run ups, range checks etc etc. before she actually flew

in a static environment the stab is using 0mah and throughout the range of throw it pulls anywhere from .2-.4 mah, however if i apply a little fingertip pressure to oppose the servo i was able to record anywhere from .8 - to a full 1 amp draw.

i'm going to pull the access hatch off and take another look at my rigging, i may have induced some excessive friction in my attempt to minimize any lateral slop.

orrrrrrrrr??

I guess it's time to rig up another elevator servo and remove some more flap surface area.

anyway, thanks for the help fellas and hopefully my dilemma has encouraged you to keep a record of your mah usage. how many times have we heard "i have no idea why it crashed" besides dumb thumbs i'd bet the next largest reason is power system distribution.

cheers
buck

btw, i'm still grinning from ear to ear and looking forward to next week.

f106jax

My Feedback: (16)

Hey Buck,

I've got 8611s everywhere, including 2 on the stab. Running 2 A123 packs into a Smartfly EQ10. Been averaging 300 mah per pack per 8 minute flight.

Great flying Rhino, isn't it?!

sandslx

My Feedback: (1)

Buck I have never heard of a turbine jet that sucked down that kind of Ma......In all of my jets none have ever used more than 350Ma/flight...You should hook up the load meater and see what the servo is drawing for power...

talk to you soon

Justin

BVM rep
Team JR/Horizon

dbarrym

My Feedback: (47)

Yo bro, seems like most everyone agrees...600 maH/flight would seem the norm.

Time to do some inline amp draw testing to isolate the source....now that you've tweaked the flaps and done some static load current draw tests at home, I doubt that's it.

Single 8711 sounds like the next likely culprit...time to see if it's got free and clear movement (no binding) throughout the range of travel.

Lemme know if you want me to borrow the Eagle Tree data logger, would be an interesting application to try.

Barry

yeahbaby

My Feedback: (21)

yeah bro' bring it out next week and we'll see what we can come up with. I know i'm going down the right trail to source out the problem and i appreciate everyone's help.

i'm focusing on the flap rigging over the next couple of days and will re-examine the stab linkage.

Hey Mike

you're right, she's a beauty and I know will rank right up there with my "buck oh 5" Hornet from a few years ago. I noticed on my first "set max thrust" run up that the stabs were shaking/vibrating a fair amount at full power. do you have the same experience?

thanks fellas

buck

yup...i'm still grinning

David Searles

My Feedback: (49)

Buck,

Check that you didn't accidentally put the exhaust pipe in upside down! The stab buffeting could be because the exhaust is angled slightly up and creating turbulence on the stab, which would add to the amount of mah drain. That pipe is very easy to install upside down because the angle is so slight, but if installed improperly it will cause buffetIng of the stab. At full power your stab should NOT BE GETTING BOUNCED AROUND ON THE GROUND. Check the bottom of your stabs, if they're getting too hot. Melted stabs could make for a bad ending to an otherwise great day.

I had the same experience of stab buffeting on the ground prior to first flights on my F-4 2 years ago, flipped the pipe and it went away.

David S

f106jax

My Feedback: (16)

Hey Buck,

I've attached a pic of the proper tailpipe install. Yea, at full power I get a fair amount of buffeting but I believe that the buffeting diminishes when the stab has air loads on it. My BVM F-4 used to do the same thing during a ground run up. The bottom of the stabs will get warm but have never shown signs of being hot. A couple of times I've had to sit on the ground for several minutes waiting to take the runway and have had no indication of damage. (soft surfaces, weave showing through paint, etc.)

David Gladwin

You really don't need all this guesswork and speculation. Beg, borrow or even buy a Weatronic Dual Receiver and you can then download the flight data (its all recorded on a SD card) and see EXACTLY what the current draw is at any time during the flight.

On the 2d graph (or 3d if you have a GPS version) you can superimpose current drain , and voltage and then overlay the various servo positions to see exactly the situation, you can even see how, say, flap servo current varies with speed, or stab servo current varies with deflection. Once everything is set up to the optimum you can then replace the Weatronic with a 2.4 or whatever with every confidence that your installation is up to par.

I see some guys selling off Weatronics at silly prices in the headlong rush to 2.4 The Weatronics on normal frequencies still works superbly with a rock solid radio link (and the data acquisition system proves it !!)

Regards, David Gladwin.

yeahbaby

My Feedback: (21)

Thanks

David, i'll look into the weatronics receiver, preciate the insight.

Big D and Mike,

I'm running a Tam pipe which doesn't have the upward angle at the exhaust end of the pipe. the stabs are warm on ground run but not excessive. additionally, i've managed to halve my flap mah usage in the static up position from my initial set up. so that's a start in the appropriate direction.

lastly, my stab is using 50-60 mah in the static position. i just can't seem to get that thing any lower with my current linkage so i'm going to try a different rod and ball link set up to see if i can minimize some slop i currently have and get her a bit lower.

i'll be keeping a close eye on her while we're in mississippi to develop my baseline mah usage per flight. Thankfully, i'll have a couple of hundred pound heads within arms reach to provide guidance.

and yup.....I'm still grinning. you boys should see her cooking along at 1/2 throttle. she's going to be bad ash with a load of stores underneath. where'd who goooooooooo?

wish i'd purchased her sooner.

thanks again fellas,
cheers
buck

CraigG

My Feedback: (40)

Sounds like a lot of work. Better let me do the flying for you while you do the math.

Looking forward to seeing you and your F-4 at MA!

Craig

yeahbaby

My Feedback: (21)

LOL no way amigo!!! I plan on burning through 7 cans of oil over the 2.5 days. Looking forward to seeing the big A-10 glad the georgia boys are coming down.

cheers
buck