John Laverick
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Posts posted by John Laverick
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Hi Guys, after a heavy weekend of Work parties, I managed to fit in a quick test with an 11-8 prop, she came out at 45 amps and 690 watts, so all in all I'm in a lot better place than when I started. Here's a picture. As I say I have no info as to who manufactured her but here she is set up for electric, I reckon she has quite a good scale look. Regards John
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Nigel, not flew mine yet (and by the sound of it I'm not gonna chance it) but I can give you a pointer on the build, Hugely enjoyable but quite complicated for a first build, I've built the TN Lanc, FW 190, and the Spit. the Lysander is by far and away a more difficult build than those three. Agree totally with everyone else, get a few under you belt firstGood luck
John
Edited By John Laverick on 13/12/2013 16:54:46
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PB, I ran the props this afternoon and came up with 9800 revs for the 11-7 and 9400 for the 12-8, not much more than you guessed. What do you reckon those figures will give me with regard to straight flight/stall speed etc?
John
Chris, looks like I've pretty much got the set up that you suggested in your post with regard to prop size, watts amps and prop speed. Don't want to put the lottery on for me on Friday do ya?
Edited By John Laverick on 11/12/2013 13:55:25
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I'll have a go tonight at getting the figures for the revs PB
cheers
John
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Hi Pete, I agree totally with all that you say, however I've already done the best I can with regard to lightening the plane, I've managed to shave two pounds of her so far, at the moment I have lead in the nose for balance but now that I'm going to use 2x 4s2p's I'm hoping to take the lead out and lose a bit more.
I ran the motors on a couple of different props and these are the results;
11-7e 4s2p 620 watts @ 42 amps, I didn't have an 11-8
12-8e 4s2p 660watts @ 45 amps
the motor and ESC got barely warm on the11 inch prop,somewhat warmer with the 12in prop. I'm much happier that both of these set ups let me run the motor and ESC combination well within their parameters. Just seems to be such small props for a big plane, one assumes(and I did) looking at a large plane it should be swinging large wooden props, given the readings from webocalc that youv'e very kindly done and my tests that's obviously not the case.
I've ordered a set of tractor and pusher 11-8 props let's hope that's the perfect set up. Obviously the results are for one motor only, and this was with not fully charged batteries.
many thanks guys, saved me frazzling a couple of motors and ESC's. I'll post a pic tomorrow to see if anyone recognizes it
regards John
Edited By John Laverick on 10/12/2013 21:41:56
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Great info guys,s I have a wattmeter and a rev counter Mark however the motors are only rated to 2-5 lipo, I tried a 5s with a 12-8 yesterday and it went way over 60 amps and knocking on 900 watts, so I'm imagining that a 6s would be to much. I will stick some 11-8's on tonight and get back with the results.
thanks again
John
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Thanks Guys,
Mark, I bit the bullet and took the nacelle apart to find out the values of the motors, it's an old BL 3520 @ 860kv, there's still quite a bit of literature online regarding the specs of the motor.
it suggests using a prop around 12.8 so I stuck one on and got 56amps @ 800 watts, however it does say on line not to go over 800watts with that motor. I stuck a 14.4 on and got 48 amps @ 700 watts, but as suggested by the posts that might not be enough pitch to fly it at a slower speed.
I might take the motors out and stick in a more "modern" lower kv motor to get a sensible sized prop working with more pitch. As it happens the motor doesn't get very hot at all on 800 watts, the ESC does though so using 14 in props is obviously not a sensible set up with that motor
PS it's not the black horse mossie, it's an old ic plane that I bought in the late 90's and I've since thrown all plans paperwork away so I have no idea who made it. It has foam wings and fuz, with rather thick plastic parts for the nacelles and gear housing. I'll stick it together and post a picture, someone might recognize it
Kind regards
John
Edited By John Laverick on 10/12/2013 07:45:32
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Defo parallel Daz, just wanted to make sure it was a duff ESC, didn't want to buy a new one and get the same result when I plugged the batteries in. There wasn't any smoke or anything, just stopped working.
Thanks
John
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Hi guys, just had a 2-6s 60amp esc go pop on me when I plugged in a 4s2p battery? I am right in thinking no matter how many batteries I parallel to the 4s it should still be within the parameters of a 2-6s esc? was it just misfortune or is there some sort of electric trickery I don't know about
John
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Nah John, just a google search on wing loading gave me the 27oz figure. I am now more than convinced the model I am building is capable of flying.
cheers John
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Many thanks guys, BEB really appreciate the workings to find the area. Having read that you should be looking for around 27 oz per sq ft to be an ideal, I was thinking perhaps I wouldn't get it into the air, however if you say 39oz is not too bad, I'm happy to go with that and I'll stop worrying about it. really appreciate it
Thanks
John
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Ha ha, you're right Mack, 28 ounces per pound is a rip off!!
BEB, wow, that puts a different spin on things, that only comes out at 527 sq inches. I worked it out first time as 890 inches!!
I did it in two parts, the wing span is 62in, root cord 17in mid cord 14in, tip cord 5in.
half the wing span to the mid cord is 10in, 14+17=31
10x31=310
the distance from the mid cord to the tip cord halved is 20in
14+5=29
20x29=580
580+310= 890sq inches?
890 shared 144=6.1
the model weighs 11pounds, 11x16=176
176 shared 6.1=28oz per sq inch
using your method I can only wring out 49oz per sq inch!!
not so much the wooden wonder. more like the concrete wonder!!
I just know that's gonna be the wrong calculations!
John
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Hi Guys, thanks for the replies, John, I get where you're coming from with regards to series and parallel, I think? Mark, I can give you all the info needed for webocalc apart from the kv/rpm of the motors. It's quite an old model and I put the motors in quite a few years ago. However I can give you all the calculations I have got,
After a few tweaks and changes of props and batteries, each motor produces 700watts @ 50amps with a 16x4 prop on a 4s1p 3300 25c. I intend too parallel the batteries for each motor to make a 4s1p 6600 25c? For each motor. I've actually managed to calculate wing loading and wing area and it comes out @ 28 ounces per pound. However my calculations may be a bit wobbly, because I'm not so sure how to calculate the wing loading on a Mossie type of wing? It's not exactly from root cord to tip cord for the measurements, I measured each part of the wing seperate and came out with a wing loadling of loads. However would you count the engine John
Edited By John Laverick on 05/12/2013 21:11:07
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Also, if I add a 2s1 3300 to a 4s1 3300 in parallel does the battery become? 4s4900 and a bit?
my brain hurts
John
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Hi Tony, nice to see you have an old Mick Reeves 80" hurricane. They still do the canopy and plastic parts for the plane. Here's a picture of mine
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Hi Guys, I have a Mossie weighing in at 11 pounds, each motor kicks out 600 Watts @ 45 amps, without sounding a bit thick!! I assume (and assumption being the mother of all) Do I just add up the value of both motors and get 110 watts per pound?
regards
John
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Thanks guys, Shaun those spinners are exactly what I'm looking for, however just a tadge too large for my project. Biggles, those are the spinners I have, really good, but pointy. Luke, I've bought those spinners before from Area 51, and they are really good value for metal spinners. Not what I really want but I think they're the closest I'm gonna get, other than getting a bespoke set.
Thanks
John
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Hi guys, anyone know where I could source a metal backed spinner in a dome shape? got loads of pointy things but they're going on a Mosquito and they just don't look good. The plastic thingy's look ok but it's quite a large model and only metal backed would do for balancing purposes.
Many thanks in anticipation
John
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Yup, I'm in
Like many I taught myself to fly and can do some wonderful stuff on the Phoenix, but like John says it most definitely is not the same at the field. Doesn't cost nowt to crash on the Phoenix!!!
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Ok, thanks Frank, if I stick an alternative power source for the RX then, would that not negate the problem with the ESC's recognising each other?
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Thanks Simon,
what I'm concerned about is what size battery I would use? if the motors are 7.2 volts would I have to use a 2 s on each pair of motors, and parallel the batteries to get a better amperage, what size single big battery would I need to use?
Am I over thinking things, or just not thinking at all!!!!!!!!! Brushless is much easier
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Fair point Frank, I just happen to have four brushed esc's to use. Suppose I could still use the 4 esc's and two batteries, one running the inner motors and one running the outer. However if I did that would both motors get the same voltage from the battery? for instance if I used one 3s on the inners would they recieve only half the voltage if paralled? The motors are 7.2 volt 480 BB's.
If the voltage is halved when paralled, would I need to use a 4s so both motors get 7.1 volts each with no change to the amps?
John
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Hi Guys, Iv'e dug out my Tony Nijhuis Lancaster for renovation, I've decided to leave the brushed motors in but I've give them each a seperate ESC and battery. Would I be right in removing the red wires from three of them, and leaving one to power 5 mini servos, or would a seperate power source be recommended?
Appreciate your help
John
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Just had the first outing this year, two flights with a Ripmax Mustang, not windy , not cold, not snowy or rainy, happy days. Anyone got a Ripmax Mustang? When there's no wind it takes half a K before the darn thing stops gliding!! not a good park flyer, but give her some space and it flys on rails. A real buzz after 4 months, top dollar
Edited By Pete B - Moderator on 12/04/2013 18:17:06
Edited By David Ashby - RCME on 12/04/2013 20:18:48
Twin watts per pound
in Power System Selection
Posted
Totally get where you're coming from Chris. I'll change em over