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Old Jan 06, 2001, 02:36 PM
Crashing IS Flying
jerrysimon's Avatar
Cambridge, England
Joined Jan 2001
1,577 Posts
Newbie - Pleae HelpMe !! Trying To Fly My New Pico-Cub

Spent a week putting it together. Taped it up with nice yellow tape. First flight knocked the motor mounting off when I eventually threw it. Having unsuccessfully ROG, I hand launched it :-( (I included the 400L gearbox for ROG). Forgot to check CG :-(

Second flight (now correct CG but heavier with balance weight_ started to ROG went up about 3 feet and then back down on the tail. Again after hand launch, landed on nose and snapped propeller. Began to think it was too heavy (750g) Spent half a day taking the tape off :-(

Now weighs 625g including weight for balance. Third flight still starts to ROG and then falls back on tail. Threw it (hand launch) again this time went up well 12ft but came down quickly. Second time on hand launch came down on nose. This time whole nose snapped off.

Anyway it's fixed again but I am confused. It appears not to have enough power to deliver the speed to lift it continually. It's built exaclty to the instructions (a little heavier than the 550g quoted but has the gearbox as well). So that leaves the batteries. They are Sanyo 6*AA 7.2V 700mAh Nicads, which look the same as those in the TX. They are what the model shop provided me with but I don't think they are right. I have measured the current being drawn when the motor is running full turning the prop, and it's drawing 1.2amps. (prop is the one that comes witht he gearbox 17.5/16cm)

The batteries are not marked AR/AE etc and I am beginning to think I have the wrong ones ? so have just ordered Sanyo 600AE's (pack of 6) from another shop who confirmed that they are wrong.

Anyone care to tell me where I am going wrong ? This is sooooo frustrating. Should the motor be drawing more current 3amp+ at full throttle. ?

Thanks in advance

Jerry
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Old Jan 06, 2001, 03:20 PM
Space Coast USA
hoppy's Avatar
Space Coast
Joined Oct 2000
21,028 Posts
I think you'll find that it should be drawing close to 8-9A at full throttle. My 6oz BUD needs 1.2A to fly. If your Amp measurement is correct, something is seriously wrong with the power train....ESC/motor/gearbox/prop/battery.
Is the ESC self calibrating to throttle range?? Is the battery fully charged?? Is the gearbox the 2.3:1 400L?? Is the prop a 7X6.5? Is the prop on right(lettering facing front)?? Is it turning in the right direction?? GoodLuck
Hoppy
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Old Jan 06, 2001, 03:27 PM
Crashing IS Flying
jerrysimon's Avatar
Cambridge, England
Joined Jan 2001
1,577 Posts
Hoppy,

Thanks for replying so quickly :-) The motor was tested outside of the plane (i.e. standalone) the battery was fully charged and I tested it with a multimeter in series (not shorting). This being my first plane I have no idea what sort of pull I should be getting full throttle ?

Jerry
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Old Jan 06, 2001, 05:33 PM
Crashing IS Flying
jerrysimon's Avatar
Cambridge, England
Joined Jan 2001
1,577 Posts
Drat!! I have double checked and the battery was not fully charged. I have re-charged it and retested the motor. It's now drawing 5.25 amps when connected directly to the motor. So I am back to where I started, why does it not appear to have enough pull to lift it more than 3 feet off the ground ?

I have re weighed everything and it comes out at 600g or 21oz.

Help..............
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Old Jan 06, 2001, 06:23 PM
All under control, Grommit!
leccyflyer's Avatar
United Kingdom, Aberdeen
Joined Sep 2000
12,609 Posts
Hi Jerry

Your Pico Cub should fly fine with those weights and the gearbox. Multiplex state 590-675g estimated AUW - my son's weighs in at 605g with a tape covered fuselage- we haven't decided on whether to tape the wing or not yet.

I've seen the Pico Cub ROG in about six-eight feet and climb very quickly into a brisk wind with the gearbox, very impressive. So there is probably something simple amiss with your power train somewhere. I'm sure you will be able to locate and cure the problem.

Firstly are you sure the prop is rotating in the right direction?- you will have needed to reverse the connections to the motor (black lead to the positive) if using the gearbox.

Is the main gear slipping at all on the main shaft? - there is a little grub screw to retain it.

You say you batteries are fully charged- is this the first time they have been charged- maybe they need to come up to spec?

Any of the above or perhaps that your ESC is not giving you the full throttle range are possible explanations for the reduced power you are seeing. What make and model of speedo are you using- does it have a little screw to adjust the motor maximum RPM or a particular start up sequence (TX on-throttle closed-RX on or similar) to initalise properly?

Good luck with the Pico Cub

cheers

Brian
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Old Jan 06, 2001, 07:09 PM
Our Daddy and Heli Junkie
Fred Bronk's Avatar
In Heli Wonderland
Joined Aug 1999
22,801 Posts
Are you sure 6 cells are enough, what is the motor?

Is the prop on the correct way, IE facing forward?
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Old Jan 06, 2001, 07:21 PM
Space Coast USA
hoppy's Avatar
Space Coast
Joined Oct 2000
21,028 Posts
That amperage is better.
Well, if the prop is on correct and is blowing the air back, then lets look at the balance. How much balance weight did you add? Where did you add it?

When it takes off, does it tend to go straight ahead or rise sharply by itself?
Same question for the hand launch?

You should let the plane fly level for say 100-150' before giving it much up elevator so it can gain flying speed.

If it is going up by itself, you have either..(1) an up elevator at neutral stick setting, or (2) the plane is tail heavy.

Are you taking off at full throttle? If you have a small scale, ie ozs, attach it to the tail and fire it up. Should read 7-8 oz (196+g).

More later..
Hoppy
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Old Jan 07, 2001, 11:44 AM
Crashing IS Flying
jerrysimon's Avatar
Cambridge, England
Joined Jan 2001
1,577 Posts
Hey thankyou very much for your replies and sugestions. Anyway fixed it for the third time. Fourth flight today. Waited until late afternoon when everyone had gone home from the park and the wind was "almost" still.

I was definately putting on too much elevator. This time is ROG and stayed aloft for about 30 second but gained no more than 3-4 feet in height before coming down.

Power is DEFINATELY the problem. The guy in the shop sold me 6 * AA (7.2v 700mAh) Nicads
which I think are the ones for a Tx not the short stubby AE/AR. The ones he gave me also have a label that says charge @70mA for 14-16hrs.

Anyway I have now ordered some Sanyo 6 cell 7.2V 600mAh AE ones which will arrive tommorow. At least then the model will be exactly as specified on the box.

Just a thought maybe I should have ordered the 7 cell ones, although I was worried that they would burn out the motor faster.

Jerry

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Old Jan 07, 2001, 01:55 PM
Crashing IS Flying
jerrysimon's Avatar
Cambridge, England
Joined Jan 2001
1,577 Posts
Yes it freezing here! My daughter came out with me to catch it all on video. They (the rest of the family) then come back and have a hoot watching me smash it up :-(

As you say it's good to come back with it still in one piece. Anyway I will update you all tommorow when I get the new batteries.

Once again thanks for all the advice. It great to have a resource like this to bounce problems off.

Jerry
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Old Jan 07, 2001, 02:48 PM
Space Coast USA
hoppy's Avatar
Space Coast
Joined Oct 2000
21,028 Posts
I definitely think the temperature may be a factor. Are the batteries warm when you start? My batteries are NiMH and really lose zip when the temp is low...low being 45 here in Florida. It took one more cell to bring them back to where they were when it was warm.
Hoppy
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Old Jan 07, 2001, 05:10 PM
Crashing IS Flying
jerrysimon's Avatar
Cambridge, England
Joined Jan 2001
1,577 Posts
Hoppy,

Just noticed reading through the blurb on my Jeti 180 ESC, it has a brake on it ? It says this can be turned off by plugging in the jumper. At the moment the jumper is not fitted i.e the brake is enabled ?

Jerry
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Old Jan 07, 2001, 06:17 PM
Space Coast USA
hoppy's Avatar
Space Coast
Joined Oct 2000
21,028 Posts
Jumper off-break on
Jumper on - Break off

It was recommended to me by US Jeti distributer to put the jumper on - break off.

Hoppy

ps I noticed during bench tests that my motor puts out significantly more power when batteries are at 60deg as opposed to 40deg. About 15% under static conditions. The plane I've been flying is marginally powered and during this cold spell it just doesn't want to stay in the air...very similar to what you have described. Adding 1 cell has made it flyable again.
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Old Jan 07, 2001, 06:24 PM
Master of disaster
Travis's Avatar
Northern Virginia
Joined May 2000
707 Posts
jerry, the "brake" you refer to simply means
that when the BEC cuts the motor at low voltage, the prop will not windmill during
the glide. (a windmilling prop is a big air-
brake and will make a model drop like a rock
when the power is off). the brake is also
nesesary when using a folding prop.

Keep those batteries in your pocket untill
your ready to take-off. If you have any
battery cooling vents block them off untill
it gets warm outside.
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Old Jan 08, 2001, 12:02 AM
characters welcome!
Mark Wood's Avatar
United States, CA, Bear Valley Springs
Joined Feb 2000
26,422 Posts
Sure sounds like a voltage problem. What's the voltage rating on your motor? Nobody has asked that one yet. Running up to 8 cells on a 6 volt motor or 10 on a 7.2 volt one is acceptable. We actually got a friend's Hobbico SkyRunner to fly simply by adding a sixth cell to the useless 5 cell pack that was supplied with the plane.
MORE POWER! (grunt grunt grunt)

mw
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Old Jan 08, 2001, 12:06 AM
All under control, Grommit!
leccyflyer's Avatar
United Kingdom, Aberdeen
Joined Sep 2000
12,609 Posts
Jerry

The instructions with our Pico Cub specify 6x600mah AA batteries- not the dumpy 600AEs you refer to- though I suspect either would do. You could easily add an extra cell (or two) as well - especially if your model was supplied with a 7.2v Permax rather than the 6v version.

Did you buy this as a made-up pack or did you make the pack up yourself? What are you using for a charger?
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