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Battery & balance

Old 11-21-2010, 02:01 PM
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1932
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Default Battery & balance

50cc Yak came out tale heavy. Can i put the battery in front of firewall to balance, it would be right behind the engine and under the CDI, between the engine stand off's that are wood. Engine BME 58 so is side carb. If RF noise would be problem could i put shielding be twine CDI and battery-as in aluminum foil.
Will post pics if i can get card to read.
Old 11-21-2010, 09:13 PM
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Default RE: Battery & balance

http://platters.smugmug.com/WEB-PICT...39_7WTnT-M.jpg
Old 11-21-2010, 09:37 PM
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Default RE: Battery & balance

Do whatcha gotta do, but do all the appropriate checks too before flying it.
Old 11-21-2010, 09:38 PM
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Default RE: Battery & balance

Do whatcha gotta do, but do all the appropriate checks too before flying it.
Old 11-21-2010, 10:34 PM
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Default RE: Battery & balance

Are you using 72mhz FM receiver? I wouldn't even dream of putting my receiver battery that close to the ignition unit if I was using a 72mhz receiver.

Or some kind of 2.4ghz? A lot of guys say that with 2.4ghz it doesn't matter. I've never had to put my batteries that close to the ignition when using 2.4 - but I'm about to do it. My Extra 300L is tail heavy. I actually already did it, but I have not been able to make it out to the flying field to test it. I'll be testing it with the engine running and performing a full range check. I'll probably have at least 1 person to help me hold the plane and watch for glitching while I walk off a couple hundred feet with my finger on the button to range check it.
Old 11-22-2010, 09:20 AM
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Default RE: Battery & balance

If it has servos in the tail, move em up under the canopy/hatch area, and use pull-pull systems for both rudder and elevator.
Old 11-22-2010, 12:26 PM
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Default RE: Battery & balance

JR 2.4 I am going with a bigger battery inside firewall. But may leave battery at engine to.
Yes the other thing to do is move the elevator servos up.
I hate to add unused weight!

Thanks
Tom P
Old 11-22-2010, 12:42 PM
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Default RE: Battery & balance

Will aluminum foil between battery and CDI do any good for shielding?
Old 11-22-2010, 06:01 PM
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Default RE: Battery & balance

Probably not. I've stacked ignition and receiver batteries on top of each other to make things work. However, I use good parts and install them well. I also perform engine off and engine running radio range checks before the first flights. If yours works the first time I would perform periodic range checks (prior to first flight of a new day) to confirm everything continues to work right.

Try doing what you want to do, perform the range checks, and see what you get before entering panic mode. If the ignition components are installed correctly, using one of the better ignitions, you may just find things will work out fine. Our ignitions are A LOT better than they were 5 or 10 years ago. You have a BME 58 so you have either a CH or RC Exl ignition. Both are good ones. If they don't work correctly, then, and only then, revert to the panic mode of pulling your hair out trying to figure out what to do. Just make sure you have the spark plug cap on tight and correct before going into panic mode.

So just how tail heavy is the plane? Are you certain the battery (a lot of weight) needs to go that far forward? If you are using a tail mounted rudder servo, could that move to center of the radio tray and be set up pull-pull to help out? Could all the other radio gear on the radio tray be moved forward to correct the imbalance? Did you add any additional wood for "stregthening" purposes? If so, could you get rid of it since ARF kits really don't need additional wood to be "better" in most cases.
Old 11-25-2010, 10:22 PM
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Default RE: Battery & balance

Looking at a heavy hub for weight balance. Do not really want to run a spinner.
Is it good or bad? What are the down points of running the heavy hub, if any?
Old 11-26-2010, 01:54 AM
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Default RE: Battery & balance

There are none if you install it tightly.
Old 11-26-2010, 12:50 PM
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Default RE: Battery & balance

Thanks TOM
Old 11-26-2010, 01:58 PM
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Default RE: Battery & balance


ORIGINAL: 1932

Looking at a heavy hub for weight balance. Do not really want to run a spinner.
Is it good or bad? What are the down points of running the heavy hub, if any?


You might notice additional gyroscopic precession, if you are a good pilot. If not a good pilot, you might shorten your engine's bearing life by a few milliseconds...(smile)

Personally, I'd install the battery where it should be and put a chunk of lead in the nose to balance the model properly. Make that chunks of lead. That way you can remove some after you fly the model several times.

Playing Russian Roullette with your model just to avoid carrying a little lead is flat out ridiculous. Never gamble on PCM or 2.4GHz to save your bacon when flying a poorly set up model. It can come back to bite you in the southern regions. Imagine trying to explain to the judge why your model set up caused it to crash into spectators because you were too pig-headed to set up the model properly. Harsh? You're damned right. You should see me as the injured person in court.


Ed Cregger
Old 11-26-2010, 03:39 PM
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Default RE: Battery & balance

Ed,

In more ways than we like to admit, we think alike
Old 11-26-2010, 04:52 PM
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Default RE: Battery & balance

I have ran my battery that close using a rf choke core. I would think if you are worried about the battery you would also be concerned about the servo. The servo wire zip tied to the ignition sensor is probably not a good ideal.
Old 11-26-2010, 06:54 PM
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Default RE: Battery & balance

Good point.

BTW, just how tail heavy was the plane? How was the tail heavy condition determined? Has the plane been flown? Those three questions are sort of important because if it's only a little tail heavy as defined by a kit manufacturers manual or plans it may not be tail heavy at all. A great many manufacturers list a CG that is well forward of what will fly best in order to make a plane as easy as possible for anyone to fly. Not necessarily easy to land, but easy to fly. Those forward CG's are not the highest performing locations.
Old 11-26-2010, 07:40 PM
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Default RE: Battery & balance

Tail heavy by manual. I fly some ass heavy butt is more than i would like from other planes i fly. Plane has not been flown yet, and would like to fly it more than once!
I will move the servo wire away from the others, any thing more?

Thanks
Old 11-26-2010, 08:18 PM
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Default RE: Battery & balance

i'm a believer of doing everything needed to keep other problems arising, but i am with 1932 on this one.
however, i realize that the bigger planes are not nearly as affected by added weight as the samller models.

so i have a question to add into this, what if the area that the battery is moved to which is up by the ignition module, is shielded with some sheet lead?
helps of course with the balance, but also preserves the lightness of the model.
Old 11-26-2010, 08:31 PM
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Default RE: Battery & balance

Mr. 1932, you’re playing Russian roulette any time you comingle your radio system with your ignition system. You can get away with it for an awful long time but one of these days it may catch up to you. Do it right the first time. Keep every thing separated as far as possible and never use metal pushrods to the engine. I am sure your RC instruction manual emphasizes this.
Summerwind, this is an old subject. There is no such thing as shielding and it should never be needed if good RF techniques are followed during the installation.
Dan.
Old 11-26-2010, 08:38 PM
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Default RE: Battery & balance

Dan, thx for the answer. i did not know this came up before. was just a thought anyways.
some of us nitro guys get a hairbrained idea from time to time
Old 11-26-2010, 08:51 PM
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Default RE: Battery & balance

Summerwind, thanks for the thanks. Here's an image of one of my installations. What you don't see is the ignition module, ignition battery and the switch because it is off to the left behind the firewall and even further forward than the front of the tank. You can just see the battery a few inches in front of the tank. Yes, it is a pain in the [email protected]@ getting to it but it's the only way to go. I hope this helps. Dan.
Old 11-26-2010, 09:15 PM
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Default RE: Battery & balance

I have good parts and try to do things right.
If i did not care about the safety of other modelers and planes i would have never asked for help.

Thanks
Tom P
Old 11-26-2010, 10:47 PM
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Default RE: Battery & balance

1932, no worries buddy, we know you care because you asked. I have to agree that the smaller planes can present some difficult balance and fit issues. I did not understand the problems small plane flyers had when using gas engines until I set up a 30cc sized plane, Coming off of 28 to 40% planes the small one presented a few challenges not seen with larger ones.
Old 11-27-2010, 09:31 AM
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Default RE: Battery & balance

Is the throttle servo ok on the engine box? I see throttle and chock servos on or close to the engine box on a lot of planes. Moved servo wire away from cdi wires and others.
Will put battery under the wing tube behind gas tank. That gives more than 13" from CDI.
Lead back of engine as needed to work for me. When set up may move elevator servos to front to get the lead out.

Thanks for all the help.
Tom P
Old 11-27-2010, 09:57 AM
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Default RE: Battery & balance



What about moving you engine out a 1/2 "?


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