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Old Jan 14, 2013, 08:56 AM
It's like an addiction!
Downwind3Zero's Avatar
NY, Rochester
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Quote:
Originally Posted by 420flyboy View Post
Here you go , Tam makes multiple sizes
http://www.tamjets.com/original/inde...4362dd2dbc08c9
That's right.
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Old Jan 15, 2013, 01:48 AM
The Need4Speed
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Malaysia, Perak, Ipoh
Joined Aug 2008
926 Posts
Thanks will keep that link handy. Still looking at my viper's bare wings wondering whether to go bungee or retracts.

On another thing, what's the minimum watts do you guys think this jet needs to fly?
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Old Jan 15, 2013, 12:26 PM
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Viper for FPV

Hi all! 
What a wonderful thread, spend 2 days reading all posts) BIG THANKS to all the pioneers of Viperjet for the experience shared, really-really useful!)

I've started to build my bird, after several seasons of small EDFs and prop FPVs decided to give a try to Viper v2 with FPV, just loved design so much! Not as fancy as Issus' one, but still..

In general: 
6s 5000mah 30C setup on 1600kv motor, 
HK939mg servos (2,5kg), 
100A opto ESC K-force
DSR-B retracts (missed the size, trimmed and fit already)
Stock fan unit
7c Futaba 2,4

FPV 5,8ghz - eagle tree full set including gps, alt and speed sensors, high-resolution googles on claverleafs

Estimated weight 3,1-3,2kg. Today tested trust - got around 1,7kg on 60amps, maximum announced thrust for this unit on 6s is 2,6 kg. Hope this will be enough for stable 5 min flight without aerobatics or high-performance. My issue is that I had most of components (like Telemetry, battery, charger, ESC - all up to 6S), so going to higher "S" number will cause significant investments, will be cheper to buy smaller or EPO EDF). So, hopefully this thing will fly as expected!))
Some pictures to follow after assembling..

Small advise to Telemetry users - noted that my Elogger4 (designed for 100amps) is getting very hot even on 50-60 amps, so air cooling to be considered in case battery data logging!

A question - will the 12blade fan make a difference or will burn my motor/ESC/battery to hell?
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Old Jan 15, 2013, 08:51 PM
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Joined May 2012
219 Posts
I received my Mercury Alloy motor, it states 95A max. Its a beautifully made fan unit, I'm very impressed for the price paid.

Interesting note on the elogger getting hot. I'm not sure if I want to go with Eagletree or Ardupilot. Ardupilot's sensor is only rated to 90A, I don't think that limiting it down an extra 5A for its max rating will make much difference to thrust output. The Ardupilot certain is a cheaper option and gives me the added stability vs EagleTree which should make for a smoother ride.

If you're not getting the thrust you expect, or the motor is getting too hot, try changing your ESC timings.

Get on ecalc: http://www.ecalc.ch/fancalc_e.htm?ecalc and you'll be able to tell if your motor/esc can take it
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Old Jan 16, 2013, 03:36 AM
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Yeap, thanks for the link! Strange, when I input motor max power in W - everything is ok, when I input max A - then I have a problem with limits.. Anyhow, calculator shows that the setup is "viable" at this stage.
I am using stabilization expander for Eagle Tree - no problems noted, plus it gives you fancy artificial horizon on OSD
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Old Jan 16, 2013, 10:41 AM
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Guys, I need an advise..

So, I have this components:
ESC: TURNIGY K-Force 100A Brushless ESC
Motor: Turnigy SK3 Fandrive - 3659-1600KV
Battery: 5000mAh 6s 20-30C
Stock fan unit

I've assembled primitive test platform on scale, using Viper's intake size made holes in bottom box, rear pipe with same size as inside the plane.
I was shocked to see thrust arond 1,2 kg! how is this possible? according to product descriptions I should get around 2,5 kilos at least.. (((

I've checked radio settings and end-points, everything is fine. Battery was 23V, max amps were around 40!! (( What could be the reason for such low thust?
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Old Jan 16, 2013, 10:54 AM
It's like an addiction!
Downwind3Zero's Avatar
NY, Rochester
Joined Oct 2003
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Your test rig is obviously not perfect, however, seeing the low amps of that run it must be your battery not holding up. All 8-12 bladed fans require good C ratings.
Chris
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Old Jan 16, 2013, 12:04 PM
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Hi Chris!
Well, even if we take lowest 20c, it should give 5000*20=100A, my motor has 65Amax load.. Plus, its 5blade stock unit.. But I got your point, maybe I need recharge battery and will definitely upgrade test rig thanks!)
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Old Jan 16, 2013, 12:09 PM
Mile High EDF
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United States, CO, Denver
Joined Jul 2011
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Think you need this motor for 6s
http://www.hobbyking.com/hobbyking/s...90mm_EDF_.html


I'm using that same motor(1600kv) in a wemotec 6 blade fan on 8s pulling max 90amps and 2400 watts on 4000mah , on 5000mah it's a little higher on amps and watts .

I think 1600kv is to low for 6s on 5-6 blades , if its the 12 blade then 6s is ok. This motor is more suited to 8s IMHO
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Old Jan 16, 2013, 01:09 PM
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Quote:
Originally Posted by 420flyboy View Post
I think 1600kv is to low for 6s on 5-6 blades , if its the 12 blade then 6s is ok. This motor is more suited to 8s IMHO
I was considering 12 blade unit, but it seems to be permanently out of stock.. Don't know really what is most practical solution - change motor or fan unit (and still keep 100A threshold)..

Recharged battery, changed test-bed.. 1,6 kg! not sure if its even enough for take-off
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Old Jan 16, 2013, 08:01 PM
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Xenon, I have a Mercury Alloy 12 Blade 90mm 1900kv EDF Unit (6s) waiting for my viperjet. The manufacturing quality is beautiful. I'm sick of plastic fans and plastic blades that just stretch and rub on the duct.

I need to get a new set of 5kg scales so I can test this out - I like your test bed setup! My scales are getting too covered in epoxy to work properly (i go through several a year lol)
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Old Jan 17, 2013, 12:14 AM
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Quote:
Originally Posted by Issus View Post
Xenon, I have a Mercury Alloy 12 Blade 90mm 1900kv EDF Unit (6s) waiting for my viperjet. The manufacturing quality is beautiful. I'm sick of plastic fans and plastic blades that just stretch and rub on the duct.

I need to get a new set of 5kg scales so I can test this out - I like your test bed setup! My scales are getting too covered in epoxy to work properly (i go through several a year lol)
Awaiting for your results!
I like Mercury a lot!!! but the price is pissing me off, its about price of the plane itself and 5-6 times more than 12CS unit. would really keen to read your feedback - is it worth of every peny?)
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Old Jan 20, 2013, 04:47 AM
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Removed all paper crap around test scale, attached plastic ring to intake = got 2,1 kg of static thrust on same 1600kv / 5 blades. Now awaiting for 12 blade unit..
Have you faced bubbles under the covering film? what is the best way to get rid of them?
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Old Jan 20, 2013, 05:33 AM
It's like an addiction!
Downwind3Zero's Avatar
NY, Rochester
Joined Oct 2003
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That looks much better!
Yes, bubbles in the covering can easily be ironed away.
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Old Jan 20, 2013, 08:09 AM
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Quote:
Originally Posted by Downwind3Zero View Post
That looks much better!
Yes, bubbles in the covering can easily be ironed away.
Ahaa, that was also my guess - never faced it before, pobably stock film is far not the best quality..
Downwind, any guess what is AUW/Thrust ratio for horizontal flight on Viper?
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