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Need help with MP Jet 25/35-20

Old 10-04-2003, 06:29 PM
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GWR
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Default Need help with MP Jet 25/35-20

Hoping for better performance, I replaced the stock motor in my GWS Zero with an MP Jet 25/35-20 brushless motor and 4.1:1 gearbox. I've only tried an APC 10x5e prop so far. The all up weight is 16 7/8oz. with an 8 cell, 9.6volt, 720mah NiMH battery. The plane doesn't fly at all now. Any help appreciated. GWR
Old 10-04-2003, 09:08 PM
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sierra gold
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Default RE: Need help with MP Jet 25/35-20

I can not see what is wrong based on the data you provided.

I have an MP Jet 25/35/20 on my Slow Stick and it's much more powerful than the stock EPS 300. I too am flying with an 8 cell pack (1100 HE NiMh) and an APC 10x5. It really makes my 22 oz. AUW SS scoot.

All I can offer is that something is wrong within your plane. I guess I would confirm that your battery pack is in good condition and has a full charge. It may be that the 720 mah cells aren't up to the draw the 25/35 can pull.

Sierra Gold
Old 10-04-2003, 11:41 PM
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Dr Kiwi
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Default RE: Need help with MP Jet 25/35-20

It is clearly a battery problem - those 720mAh AAA's cannot provide more than ~6A, and then at considerable reduced voltage under that sort of load [probably down to ~7.2v @ 6A draw, so you are getting only about 45W]. I reckon that, with a 10x5, your 25/35-20 is producing at peak about 100W @ 10-12A. You need KAN 1050's or similar - they won't suffer the voltage drop that AAA's do, and they'll happily provide 10-12A.

Cheers, Phil
Old 10-05-2003, 06:53 AM
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Greg Covey
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Default RE: Need help with MP Jet 25/35-20

Yes, I agree, good suggestions above.

This type of situation where you want to draw more current but keep the flying weight light is a good application for Lithium Polymer cells.

I use the MP Jet 2535 motor with an APC 9x6 SF prop on a 3-cell, Kokam 1500HD pack. My P-51 goes vertical at only 3/4 throttle so full throttle is used very little...perhaps only on takeoff.

Another option is to keep your prop size larger and use less cells of higher current delivery capability (and therefor higher weight). An example would be a 6-cell pack of CP1300 NiCd or the newer 1700mAh 4/5AUP NiMH cells that are AA size or even the lighter Sanyo HR-4/5AA 1350 Hi-MH cells. You can check out these cells at [link=http://www.flydma.com/batteries/index.html]Diversity Model Aircraft[/link].

Good luck!
Old 10-05-2003, 08:05 AM
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GWR
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Default RE: Need help with MP Jet 25/35-20

Thanks guys. I've ordered some LiPos and I'll try them when they get here. I also have a KAN 950 mah x 8 cell pack. I hesitated using this pack because of the weight. It's 3 1/4oz. heavier than the other which would make the all up weight 19 1/2oz; but from what I'm reading the extra weight shouldn't matter. Does any of you think this pack can supply the amps or should I wait for the liths? Thanks again, Gary
Old 10-05-2003, 08:21 AM
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Dr Kiwi
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Default RE: Need help with MP Jet 25/35-20

The KANs will supply what you need, as will the correct configuration of Lipoly - but of course the Lipolys will be much better as far as weight goes.

Cheers, Phil
Old 10-06-2003, 07:41 PM
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Default RE: Need help with MP Jet 25/35-20

Just wanted to thank everyone that replied to my problem. I flew the Zero today with an APC 9x6 Slo fly prop and a 3 cell, Thunder Power 2100mah pack. I was very impressed, as was everyone else at the field. Thanks again, Gary

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