Cyclicscooby Posted May 26, 2011 Share Posted May 26, 2011 Hi guys...First, I've finished my tailwind at last...32" with A.U.W 21.7 oz with 3s 850, or an ounce less with the 450mAh batt.. When I get to a pc, I'll upload pics.... But.. I've just tested my new watt meter and I have more power than expected... Spec -E-flite park 370 BL - 150w 12/15A cont/max18A ESC3S 850mAh lipo - 25c / 35c 21A / 29AUsing suggested prop (in motor specs) - 8 x 8.3It's drawing 175W @ 16.5A full chat and 90W @ 8A half stickSo batt and esc within specs, but motor overpowered.I presume a 2s batt would lower it, but Cud I down size the prop.. and if so, to what...? I haven't a clue, so you'd save me buying 15 props n guessing.... Any help or advice gratefully received..Luv Chrisie xx Quote Link to comment Share on other sites More sharing options...
Richard Wood Posted May 26, 2011 Share Posted May 26, 2011 Hi Chrisie, The easiest & cheapest way to reduce current draw & power is to use a smaller prop - so try something like an APC E 7 x 4 for starters. This could well bring the current down sufficiently. Your little 450mAH battery will struggle to provide the current though - it'll be working at about 33C to provide 15A - a bit too much. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted May 26, 2011 Share Posted May 26, 2011 Id leave it TBH - it will unload in the air anyway.Agree on the battery issue though Edited By Tim Mackey - Administrator on 26/05/2011 16:15:24 Quote Link to comment Share on other sites More sharing options...
Richard Wood Posted May 26, 2011 Share Posted May 26, 2011 Yep, good point - and you'll probably find that you use full throttle very little & only in short bursts anyway. Quote Link to comment Share on other sites More sharing options...
Cyclicscooby Posted May 26, 2011 Author Share Posted May 26, 2011 Cheers guys Yeah, id realised the 450 wud probably explode It just so happens, I bought a 7 x 4 prop yesterday to build the edge 540 shockie that's in the June RC Model World..I also got a 3s 1300 batt, that might get called upon, as I've just done the C of G and found she needs 28g in the nose, with the 850 batt as far forward as it'll go.. I'll go and weigh it in a bit... Ur probably right about the current setup being ok tho, its no stunt flyer, so full throttle shuddering be a rare occurrence...So, I'm off to glue 7 pennies and a 5p inside the nose...Luv Chrisie xx Quote Link to comment Share on other sites More sharing options...
Cyclicscooby Posted May 26, 2011 Author Share Posted May 26, 2011 Sorry about the spelling, I'm lacking internet so I'm using my phone... Quote Link to comment Share on other sites More sharing options...
Chris Bott - Moderator Posted May 26, 2011 Share Posted May 26, 2011 Chrisie is it really an 8x8.3 prop? or was that yr phone adding it's own thoughts to the post?It just sounds a very odd size. If it is, or if it's an 8x8, then an 8x6 would help the situation. Also, is it an APC-E electric prop? If it's an I/C prop the swapping to an APC-E will be more efficient and could reduce the current. Quote Link to comment Share on other sites More sharing options...
Cyclicscooby Posted May 26, 2011 Author Share Posted May 26, 2011 Doh... ! You're right Chris.. It's meant to say 8 x 3.8e.. I wish I could blame the phone, but its my fopar..Luv Chrisie xx Quote Link to comment Share on other sites More sharing options...
Frank Skilbeck Posted May 27, 2011 Share Posted May 27, 2011 Changing to a 2s battery would probably drop the wattts down to around 80w which might be a bit on the low side. Rather than buy lots of props, get a copy, free, of drivecalc, www,drivecalc.de you select your motor (or one near it if its not listed, i.e. same kv) and change the props and check the effect. Quote Link to comment Share on other sites More sharing options...
Chris Bott - Moderator Posted May 27, 2011 Share Posted May 27, 2011 Just another thought Chrisie.8x3.8 sounds to me like a slow fly prop. Now, I have no experience of these, but does anyone else on here know if 175W is OK for one of these? Don't want it to shed a blade on you. The APC website says the slow fly props should be run at no more than 65000/ prop diameter RPM. So thats 65000/8 that's 8125 RPM. Edited By Chris Bott on 27/05/2011 14:01:05 Quote Link to comment Share on other sites More sharing options...
Cyclicscooby Posted May 28, 2011 Author Share Posted May 28, 2011 Hi Chris.. Correct, it is a slow fly... I didn't realise there would be an issue with rpm, so thanks for that.. iirc the motor is 9k- 13k rpm.. that is full chat, but even so... I'll have to give the 4 x 8e a go on the watt meter.. I'm gonna try an angling shop tomorrow, for a set of hanging scales, to measure the static thrust... Thanks for all the replies..Luv Chrisie xx Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted May 31, 2011 Share Posted May 31, 2011 Just one comment. Mine was quite aerobatic. Have fun. Quote Link to comment Share on other sites More sharing options...
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