[wingtipper]

ok thanks gary . . there is no way on earth i can put a bigger prop on this . i think its on its limit at 13 x6 . but an absolute screamer at that . i have a 12x8 , but i fear the prop may be too small for this plane , and will need to race in order to have some grunt . . .
.
it has all out balls of power with this engine and prop . but dont want to over load all the componants , and have her fail .
i'll have to take it up and do some trial and research on the flights etc . if it gives me trouble , i'll be looking into that hacker . in fact i'll have a look at modelflight now .

[secant0give]

I think it certainly has enough power, in fact more than enough power. It's a 700KV motor so it revs quite a bit higher than the Hacker at 427KV. So I would expect it to want to spin a smaller prop.

If we compair 3 different set ups
1) Gazza's set up = Hacker-427Kv and and a 16X8 prop and it certainly flew well no problems at all
2) My Edge 540 set up = 5055-600 Kv motor and a 15X6 prop also flies well no problems at all
3) Your set up = 5055-700Kv motor and a 13X6 prop I can't see why it shouldn't perform very well also.

The higher reving the motor, the smaller the prop you want.

To me all of these setups look to be in the ball park.
If you looks at Gazza's set up you'll notice that he was using a 5000 pack and that's why he has the longer flight time. My Edge uses a 3000 pack as does your set up so we might expect about 3/5 of the flight time that Gazz was getting but with the benifit of less all up weight.

If you want to spin a bigger prop and reduce the all up weight you could go to a 5S 3000 pack and you might spin a 14X7 or a 4S 3000 pack and spin a 15X8. You could also maintain the same weight by going up in capasity as you come down in cell count (volts) and achieve a similar result

[wingtipper]

the only thing left to do , is reverse the dual rate switching . and its going up jason . as will be the stinger , and the cessna with the new prop . . ive only just become ok with flying the cessna after such a long break . so you or other flyers in the club will be sending them up for their maidens me thinks .
soon we will find out . i have the PHEONIX dongle on order !! but am looking forward to some flying , hopefully shortly , the weather will stabalise and dry out the strip , and my days off will increase by 30% . it sounds GOOD to me .
on the other hand the cocker spanial is at the vet and has racked up $1300 in bills , and i have just lost 2 days pay in a strike !!!
these days i dont see dollars , i see potential RC VALUE / gains and losses . funny that

[gbanger]

I agree with your comparisons Jason, but he is currently drawing way to much current with the 13 x 6, so some field tests with a variety of props may be necessary to get the performance Frank is after without pushing the envelope and frying a motor, ESC or the whole plane.... heaven forbid.

[secant0give]

If you were drawing 90A continious I would also say way too much!!
But that is flat out and static, ie tied to a post.

Once it gets in the air it will be unload and the current draw will fall off a bit

The ESC he's using is rated at 85 A continuous and 100 for 10 second burst so it should be OK
The motor is rated for about 80A as well
here's a link https://www.leaderhobby.com/product.asp?...4001100041

The Lipo's are 20-30C 3000mah so can handel 90A for the odd 10 second burst
you can go a long way in 10 seconds!!

The trick is to use the throttle judiciously treat it like nitros and only use max throttle in short bursts of about 4-5 seconds. That's all you need any way.

This way you get the most out of your power system and the ultimate in power to weight.
you just cant use it 100% of the time but you don't need too?? It will have heaps of grunt about 2000W peek (90A) power for short bursts and 1000-1500 (45A-60A) to put around with in between those bursts, that will be fairly sprightly putting around too I might add.

If you go vertical on full noise for 6 seconds you'll be at cloud base on a clear day for sure (read 399.99ft)

[gbanger]

Thanks for the physics lesson Leonardo, I already knew that. My electrical flying philosophy is a little different to yours, and I suppose thats a good think because we both look at power consumption and use from different directions, I do have a tendancy to over power, over ESC and over battery pretty much every thing, but hay I have never had an electrical failure of any sort, but at the end of the day who gives a shit as long as it flys like a champion, hope to catch up down the field this weekend.

[wingtipper]

WELL , I have the lightwood , 13x6 prop on it , i also have a APC 13X6.5e prop , which sounds quieter , i also have a 12x10e APC and a 12x8e APC . SO PLENTY OF CHOICES . the 13x8 had massive thrust though , just peaked over 100 amps , so a little too high .
the 13x6 higher rpm and will hold its weight at 50% throttle . the 12" props i havent tried as yet , i dont think a 12 x10 prop will draw less amps than a 13 x6 , and the 12x8e i dont know , maybe a racer prop . it will start with the 13x6 , and we'll take it from there .
really loving the input guys . learning a lot . and great to see different perspectives . it will be interesting to see a comparison between my 700kv motor with 13 inch prop versus jasons 600kv with 15 inch prop , similar plane . if anything . theres another mix of theory to put into practice .
once you go bigger though as in 60 size motors . kv drops to around 270 rpv . big difference
really surprised we dont have 60 size motors with 300 to 700 kv .( wierd)

WHAT GEARS RUNNING IN THE SUKHOI GAZ . AND WHATS IN YOUR BIG PLANE JASON ?

[secant0give]

Thanks for the physics lesson Leonardo, I already knew that. My electrical flying philosophy is a little different to yours, and I suppose thats a good think because we both look at power consumption and use from different directions, I do have a tendancy to over power, over ESC and over battery pretty much every thing, but hay I have never had an electrical failure of any sort, but at the end of the day who gives a shit as long as it flys like a champion, hope to catch up down the field this weekend.

I like your insites Gazz and I reckon your setups are reliable, robust, and certainly not lacking in power. I Cant wait to see your new machine fly, I'm definatly going to be down at the field this weekend, I've got all the rello bash stuff out of the way for a while now. Just hoping the weather's nice for us!!

Posted by wingtipper - Today 12:01 AM
AND WHATS IN YOUR BIG PLANE JASON ?

The Yak 55M has a turnigy G160 motor 245KV, the ESC is a TURNIGY K-Force 120A-HV OPTO 5-12S, the Battery is 12S 3000 20-30c made by connecting 2 6S 3000 packs in series. (I use these in my Edge 540, just one at a time) It has a seperate dulesky twin 8A BEC that's powered by 2X2S 850mah Lipo's. That gives me double redundancy for powering the RC link and servos.

The G160 motor is rated for 78A/15sec and for 9-10 Cells. I know I'm exceeding the voltage by running it on 12S but since I reglued all the magnets in, I've had great sucess with it and it's not hot after 5 mins of fairly hard flying. Here's a link to the motor
http://www.hobbyking.com/hobbyking/store...Glow_.html

With a 19X6 light electric wooden prop it pulls 75-80A static. (about 3750W) again this is peek power 10 sec burst only and it will draw less current in the air.
I concidered proping it up slightly, because the motor comes down barely warm, say 'till it pulled 80-85A static (about 4000W).
It flies with such authority as it is, that there's no need.

I carefullychose the set up based on best comprimise I could find between power weight and cost using a 5min flight time with some reserve.

The all up weight is 5.050 Kg which is not bad concidering it's a Super and Cheaper airframe, not nearly as lovely and light as a Sebart. But it is very straight so concidering the price it is still excellent value and a real BUZZ to fly!!


To give you rough idea of the average current draw. my 3000 packs are comming out of the plane after 5 mins at about 3.7-3.8 Volts per cell. If you can assume that they are 70-80 percent discharged at this, then that gives you 2,250 mah in 5 mins (.083 hours) so average current would be in the order of 25-27 Amps.
It is not just floating around too, you've probably noticed that I usually do give it some, when it's in the air.

I will say that it's a bastard to re-glue the magnets in these big motors! It's a 2 person job, the best glue and primer is expencive and hard to get. (I had some luck here) Had I to do it again I would definately buy a better motor!!

[wingtipper]

Thanks for the physics lesson Leonardo, I already knew that. My electrical flying philosophy is a little different to yours, and I suppose thats a good think because we both look at power consumption and use from different directions, I do have a tendancy to over power, over ESC and over battery pretty much every thing, but hay I have never had an electrical failure of any sort, but at the end of the day who gives a shit as long as it flys like a champion, hope to catch up down the field this weekend.

I like your insites Gazz and I reckon your setups are reliable, robust, and certainly not lacking in power. I Cant wait to see your new machine fly, I'm definatly going to be down at the field this weekend, I've got all the rello bash stuff out of the way for a while now. Just hoping the weather's nice for us!!

Posted by wingtipper - Today 12:01 AM
AND WHATS IN YOUR BIG PLANE JASON ?

The Yak 55M has a turnigy G160 motor 245KV, the ESC is a TURNIGY K-Force 120A-HV OPTO 5-12S, the Battery is 12S 3000 20-30c made by connecting 2 6S 3000 packs in series. (I use these in my Edge 540, just one at a time) It has a seperate dulesky twin 8A BEC that's powered by 2X2S 850mah Lipo's. That gives me double redundancy for powering the RC link and servos.

The G160 motor is rated for 78A/15sec and for 9-10 Cells. I know I'm exceeding the voltage by running it on 12S but since I reglued all the magnets in, I've had great sucess with it and it's not hot after 5 mins of fairly hard flying. Here's a link to the motor
http://www.hobbyking.com/hobbyking/store...Glow_.html

With a 19X6 light electric wooden prop it pulls 75-80A static. (about 3750W) again this is peek power 10 sec burst only and it will draw less current in the air.
I concidered proping it up slightly, because the motor comes down barely warm, say 'till it pulled 80-85A static (about 4000W).
It flies with such authority as it is, that there's no need.

I carefullychose the set up based on best comprimise I could find between power weight and cost using a 5min flight time with some reserve.

The all up weight is 5.050 Kg which is not bad concidering it's a Super and Cheaper airframe, not nearly as lovely and light as a Sebart. But it is very straight so concidering the price it is still excellent value and a real BUZZ to fly!!


To give you rough idea of the average current draw. my 3000 packs are comming out of the plane after 5 mins at about 3.7-3.8 Volts per cell. If you can assume that they are 70-80 percent discharged at this, then that gives you 2,250 mah in 5 mins (.083 hours) so average current would be in the order of 25-27 Amps.
It is not just floating around too, you've probably noticed that I usually do give it some, when it's in the air.

I will say that it's a bastard to re-glue the magnets in these big motors! It's a 2 person job, the best glue and primer is expencive and hard to get. (I had some luck here) Had I to do it again I would definately buy a better motor!!

great read mate . thanks . i have noticed you give it a lot of stick about 80% of its time in the air . hahah .
i'm working all weekend ( rostered on) . unless i take a sickie . but i have relos down from queensland as well , so i'm better off working .
in how . have fun on the weekend if i dont runnin to you guys . the next 2 weekends ill be rostered off after this one .

[wingtipper]

If you were drawing 90A continious I would also say way too much!!
But that is flat out and static, ie tied to a post.

Once it gets in the air it will be unload and the current draw will fall off a bit

The ESC he's using is rated at 85 A continuous and 100 for 10 second burst so it should be OK
The motor is rated for about 80A as well
here's a link https://www.leaderhobby.com/product.asp?...4001100041

The Lipo's are 20-30C 3000mah so can handel 90A for the odd 10 second burst
you can go a long way in 10 seconds!!

The trick is to use the throttle judiciously treat it like nitros and only use max throttle in short bursts of about 4-5 seconds. That's all you need any way.

This way you get the most out of your power system and the ultimate in power to weight.
you just cant use it 100% of the time but you don't need too?? It will have heaps of grunt about 2000W peek (90A) power for short bursts and 1000-1500 (45A-60A) to put around with in between those bursts, that will be fairly sprightly putting around too I might add.

If you go vertical on full noise for 6 seconds you'll be at cloud base on a clear day for sure (read 399.99ft)

ok TODAY was a trial test day , lots of hours spent static testing . if any one finds this boring dont read , but i had a ball .
what i found was this !!!!
. THERE ARE 6 WHITE LINES in the throttle stick , the 3rd being 1/2 way ,50%
so i took readings from line 3 ( 50%)
line 4 ( 67%)
line 5 (83% )
line 6 (100%)

IT HAS AN 85 AMP ESC IN IT , WITH 100 AMP 10 SEC BURST , AND AN 80 AMP 700KV 5055 MOTOR , USING 6S 3000mah 20C battery pack .

OK. WHAT HAVE I FOUND .
THE PROPS FITTED ALL PULL HIGH RPM, NO noticable difference in rpm with any prop. the 12x10 APC WAS A PURE SCARE !!!!
IT PULLED 40 amps @ 50%
70 amps @ line 4
130 amps @ line 5. i didnt bother with line 6 .

then there was a lightwood 13x6 , APC 13x6.5 and APC 12x8.
these were all pretty much even in thrust and amps throughout the rev range , with the lowest draw from the 13x6.5 APC .

IT PULLED 28 amps @ 50%
48 amps @ line 4
79 amps @ line 5
96 amps @ line 6 all continual , all static . 10 second bursts .

my thoughts are that line 4 is pretty is pretty hard flying and would be going upwards vertically . 50% line 3 would see a close hover .
i conclude in theory guesstimate that flying around at line 4 would be a hoot and it would be pulling about 25 amps at that in the air .
the ESC FREQUENCY IS SET at 8 khz factory default , and the timing is automatic from 7 - 30 degrees . the thermo soft reduction cuts in at 110 degrees which cuts power to about 30% .
on a static test at 50% throttle constant 28 amps after 4 min 30 secs . it started dropping off current even though still at 23 volts . after a 5 minute cool down it did another 5 minutes , and still had each cell at 3.7volts .
so i'm hoping in the air with air speed and unloaded prop we'll have better cooling and a lot less current draw than static , which means hopefully after quite a few test flights , it can hoot around for a good 4 minutes.
time will tell . hope this is interesting . i certainly enjoyed the day .
OMG if only technology was available for it to drive that 12x10 , or 13x8 prop at those revs .

saing that i just hope it can drive the 13x6.5 or 12x8 with the grunt it has .
seems to be abig difference between a 700kv , and 580kv and 470kv
setup [/align]

[secant0give]

Sounds like you've got it pretty much sorted there mate
It's interesting playing around with electrics isn't it !!
Imagine how much caster you'd be wiping off everything if you did all that with a glow powered machine
Not only that, these electric motors are a lot easier to start!!

I reckon I should have lent you my tacho so you could have checked the revs s well it's hard to guess how fast it's turning just by the sound.

[wingtipper]

Sounds like you've got it pretty much sorted there mate
It's interesting playing around with electrics isn't it !!
Imagine how much caster you'd be wiping off everything if you did all that with a glow powered machine
Not only that, these electric motors are a lot easier to start!!

I reckon I should have lent you my tacho so you could have checked the revs s well it's hard to guess how fast it's turning just by the sound.

mate the best part is the learning . i'm learning a lot about electric principles that i simply didnt know in practical terms . its one thing knowing that a 750kw's is 1000hp as in cars on a dyno .

But it's another working from a battery pack , through an ESC to a rated KV motor , with a pole number and amp and volt rating , over the weight of an aeroplane , onto the load and pitch of a prop . then testing static , and theorising unloading in the air for thermo purposes . LOL

Puts a whole practical understanding into perspective , before you fly it . love it . simply didnt have to do that to the enth degree before .

[smuzz]

OK - a quick one!
When attaching a bungee hook to a jet, should the hook be placed in front of the CoG, right on the CoG, or behind it?

[paulj]

2/3 of the distance from nose to COG.

[smuzz]

Hmm - OK, thanks Paul.

[kizza42]

Behind CoG!!!

Hilarity Ensues

[smuzz]

Yeh, I knew that wasn't an option stability-wise - but I wasn't going to let on, and just see what flowed ...
See you tomorrow ... later today!

[samste]

Is there any Reason Why you cannot Use a No bec Esc for your motor Control and then a 2nd Esc with Bec for power to Rx and Servos

Eg 120amp esc no bec powering Motor
18amp esc with 4 amp bec for rx power

Did have a discussion with Jason Re separate Bec and dual bec Setups etc which made me think instead a bec use an Esc


Steve

[gbanger]

Dont think so mate.
The Stand alone BEC sends the throttle signal to the stand alone ESC. If you had another ESC with a built in BEC in the loop then you would not have any throttle signal to your 120 amp ESC and if you split the output signal then ???????
Why wouldnt you just buy a purpose built BEC ?????
Gazz

[kizza42]

You're carrying around dead weight if you take 2 ESC's. The BEC in an ESC is the same as a standalone BEC. They're both basically switch mode power supplies

[secant0give]

It should be possible but as Kieran says your just hauling around the dead weight of an ESC you would have to plug both ESC's into your Lipo's and have both going to your RX. you might have some extra electrical noise if you don't terminate the output of the second ESC, I mean the three phases that go to the motor. I don't think they like running with no load either.


Some BECs are swtich mode supplies and some are liniar regulators.
the thing to remember is that liniar regulators create less electrical noise than switchmode supplies
but liniar regulators use more power and don't like haveing a large difference between input and out put voltages.
For example you should not concider using a liniar regulator on your 10S pack to bring the voltage down to 6V for your servos and RC link. It will probably fail as the greater the voltage difference the more power it has to dissipate.

The nicest set up for big or fast models is twin liniar regulators set up with twin small 2S lipos 500mah or 850mah if I want something bullet proof I'd use these.

http://www.dualsky.com/pro_list_for.asp?sid=119&nid=126&id=544

www.dualsky.com/\downloads\05cm7g0310vr-8len.doc

Kellets have them on the shelf I think


For larger or faster models it's not just insurence for all that time and cash setting them up. It's also a safety issue!!
I'd feel really bad if someone got hurt because of a failure with one of my models and I hadn't done everything reasonable to make sure it was safe.

[kizza42]

For something big, you just go for 7v lipo & High Voltage Servo's/Receivers and ditch the middle man so to speak!

[wingtipper]

Any advice for or against these new tx's please . Thinking of getting one as my Dx6i is being checked for a fault . The Dx7s is Dsmx only I think . Will it be compatible with orange 710 receivers? And an they be connected to other spectrum tx's for training via a buddy system all opinions /advice appreciated they are about $350 incclusive . Cheers

[kizza42]

DSMX Tx's are backwards compatible with DSM2, I'd personally grab the DX8 and be done with it, The DX7s has a lot of software limitations for the sake of being the DX8's little brother.

Also these questions can go in general Q & A thread

[wingtipper]

I didn't realize there was a question and answer thread . Thanks for moving it . Can you explain further . Is the dx6i also a better option than I dx7s . How much can I get a complete dx8 kit for are t they quite a bit more . I'm stretching over a new dx6i to look at the d 7s I have spent a bit in a short time getting into the hobby , hopefully the warranty will kick in on the current tx I have sent back . I have heard a few people in the club not in favour of the dx7 not sure a out the dx7s . I will hold off a. Bit longer and buy a dx8 or another dx6i if the dx7s isnt worth getting .

[kizza42]

Obviously it all comes down to personal opinions, in my experience:
DX8 > DX7s > DX7 > DX6i

[Flying fisho]

Hey Jonathan, you laybyed a DX8 from hobies in the hills, can you fill frank in on the price, not mentioned on your post, just said "price was too good to go past"

[BenR]

I can answer that as I got one at that price too - it was $399. Was til they ran out (not sure if/when that happened). If they are out, I also saw one from ModelFlight that was $499, but included some (2?) extra free rx.

[wingtipper]

thanks guys , i would buy the DX8 AT $399 , But i think that price was TX only , and thats the price at Modelflight also /or $499 for kit .

the DX7s is $349 for KIT . I was amazed to see a lot of youtube clips regarding glitches and recall's mainly with the DX6i and some with DX8 , especially with certain date/manufactured models .
which led me to DSMX- versus DSM2 . dsm2 has been troublesome apparantly , and the lates DSMX versions of DX7s, and DX8 Seem to be much improved as far as brown out voltages are concerned ,and reconnections of less than a second where as my DX6i dsm2 took 5 seconds to reconnect under testing at home .
MY DX6i , which i bought 2ND HAND was/is less than 1 year old and is back at OMP for testing as i have lost 2 models and had 3 crashes due to glitches /signal losses , a very costly experience , and i am dissapointed i have lost models $$$$ , time and now a TRANSMITTER AS WELL . Finding out of a HISTORY of faults with the DX6i and owning one . has left me red faced .
i can only recommend BUYING NEW RADIOS NOW , and hope the failure rate is RARE , as i cant continue losses as such .
THATS WHY im concerned and asking for advice .

http://www.youtube.com/watch?v=fQKoXpj-FeI&feature=related
i think a new DX7s from what i read is an improved radio for SPECTRUM , as is the NEW DX8 , after earlier recalls regarding DSM2-DSMX , from what i gather . DX6i i'm not sure about anymore , and am a little hesitant with this . i never had a glitch of crash due to any fault with my 36 meg crystal radio and used to fly almost out of sight . to have 3 failures at close range 15 years later with better technology ANNOYS ME . RANT OFF .
ANY advice APPRECIATEED . THANKS GUYS . hope that explains my concern .

[BenR]

Not that I'm greatly skilled, but as best I can tell the one I got for $399 (DX8 from Hills) had a tx, an rx and a sensor/telemetry module. The rx is a model AR8000 (reading it off the box) with a piece hanging off with Model No. 9645 and the sensor is a TM1000. Tx is of course DX8.