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NiMH Rx batteries

Old 05-31-2006, 02:52 PM
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MJD
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Default NiMH Rx batteries

Hi folks,

I ordered some of the Tower 350mAh NiMH packs to cannibilize for Rx packs, but I also ordered a couple of the 220 mAh NiMH packs as well.

Anyone used the 220 mAh cells for 1/2A Rx packs before, and what - good or bad - should I know about them? I've inferred from previous posts with NiMH packs one needs to be more cautious about flight time relative to the pack size. Seems to me on a .049 sport aero or SWR on two channels with HS-55's or the like, that you should be safe for 30 minutes of Rx on-time/flight time or so, but any advice there? I used to fly my 225 mAh NiCAD's a few times before worrying.

One of these pack sizes is destined for a Blink [sm=sleeping.gif][sm=spinnyeyes.gif][sm=sleeping.gif], and the others for my venture into the world of SWR's.

Thx,

MJD
Old 06-01-2006, 08:49 AM
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Default RE: NiMH Rx batteries

Hi,

I used brand "X" NiMH cells of 350 mAh and that worked well with 3 servos.
The only thing you have with NiMH cells is that the voltage drops quite a lot when you draw very large currents. For exemple when you use them as power pack for your e-drive. It is unlikely this will happen when using them in an RX-pack.

If you don't trust it, measure the voltage with 1 or more stalling servos. This is a good indication for the condition of your battery pack.
Old 06-01-2006, 09:00 AM
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ptulmer
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Default RE: NiMH Rx batteries

MJD, I normally only fly each airplane 2-3 times on a day at the field, so the 220mah will make it through that. That's two channel operation in racers. I'd say thirty minutes is a pretty fair estimate before recharging.
Old 06-01-2006, 10:40 AM
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Default RE: NiMH Rx batteries

Thanks fellers. I imagine they can cope with the drain of a receiver and two HS-55's without protesting too much. I have two 8 cell 220 mAH packs coming, so that will give me 4 packs and thus no sweat to charge up a couple to take with me. Or I can recharge at the field.

Hey PT, I was ogling the Killer Buzz plans you sent, and decided just to be different and draw up my own SWR, staying reasonably close to the moments and areas of the KB. Wow, SWR's are cool, you can draft a set of plans in minutes as opposed to hours on AuotoCAD.. I have a couple of VA .049 Mk I's that need a home, and this will be just the ticket.

Oh yeah, and what about recommend throws for the Blink??? [sm=confused.gif]


MJD
Old 06-01-2006, 11:12 AM
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Default RE: NiMH Rx batteries

MJD, the recommended throws vary so much. If you're planning on going really fast, dual rates would help. High rates 1/8" each way and low 1/16". If you don't have dual rates, stay with the high rates for your first flight and make'em short flights.
For the Surestart's, Golden Bee's and Blackwidows, 3/16" would be a good starting point.

Yeah, I really like the SWR's too. I haven't gone all that fast with mine, but Flyswatter uses carbon fibers strip as a spar when using a TD. You'll probably want to sink a spar in there or do like FS if you don't want the dihedral when you pullout. CP likes to put spars in much shorter spans. Everybody that's built an SWR oughta go together and get COMBATPIGG a copy of turbocad. It'll be cheaper than the copyright lawsuits he's planning.[sm=lol.gif]
Old 06-01-2006, 11:43 AM
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Default RE: NiMH Rx batteries

ORIGINAL: ptulmer
Yeah, I really like the SWR's too. I haven't gone all that fast with mine, but Flyswatter uses carbon fibers strip as a spar when using a TD. You'll probably want to sink a spar in there or do like FS if you don't want the dihedral when you pullout. CP likes to put spars in much shorter spans.
I plan to lay a narrow strip of .007" unidirectional CF laminate on the top and bottom of the high point. I sometimes use tow for the same job, depending what I'm stiffening. I did my GWS P-51 and Formosa that way, and the wings don't flex at all. The weight gain was trivial.

It would be great if everyone pitched in and got CP a CAD program, but then we're going to have to find him a printer that can handle brown kraft paper.

Actually I miss drawing by hand - it is much more satisfying. Problem is in my current workshop, I had to choose between room to move around or my drafting table. The table lost, it's in the barn for now.. []

MJD
Old 06-01-2006, 11:48 AM
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Default RE: NiMH Rx batteries

Oh yeah, the sketch so far. I wish I knew if the upload worked - wish they would preview. How do you like the blatantly plagerized name concept?

I might side mount the VA and fair the nose around it a bit. Depends how lazy I am when I get building.

Hey, where did the side view go?...

MJD
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Old 06-01-2006, 11:49 AM
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Default RE: NiMH Rx batteries

ORIGINAL: MJD
Hey, where did the side view go?...
MJD
Oh there it is.. never mind. Doh!
Old 06-01-2006, 12:00 PM
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Default RE: NiMH Rx batteries

Oh LAWD! You 'bout killed my with the name. I laughed till I cried!
Old 06-01-2006, 12:56 PM
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Default RE: NiMH Rx batteries

Next time I do a .jpg from ACAD, I'll know to change to white screen black lines before exporting.

After I saw the posts about "Sheetface" I couldn't leave it alone.. I had to do one too.

On the Blink I plan to go fast, but will be using the VA .049 RC so throttle is available (egads, another 10 grams of servo and linkages) and top end will be down over the C/L combat versions. Once/if I get used to the aircraft maybe I'll swap out engines later. I do have dual rates and will make good use of them. Thanks for the throw recommendations, I am pretty new to deltas, esp. small ones, so had no idea where to start and I did not want to loop it into the back of my head or corkscrew it into the ground half a second after launch. I've hit myself once with an RC airplane and that was quite enough!

MJD

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