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Latest blog entry: T/A 37 Tweet/Dragonfly
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Rutland, England
Joined Feb 2005
160 Posts
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Hi guys, i'm new to this (very interesting) thread and i haven't (yet) got my own Vampire
However, as soon at the kit version comes back in stock in the UK warehouse i shall be ordering one and can't wait to get testing/flying.One of my particular interests will be in optimising the propulsion system efficiency so as to get extended flight times (as opposed to maximum thrust) - this means targetting 'modest' thrust levels (say around 1Kgf static thrust - in the model) but hopefully using this new 12 blade fan, since it should, theoretically at least, be more efficient than the 10 blade jobbie. When you guys with bench test rigs (with thrust meter capability) are able to start some tests on 12 blader - it would be really very handy if you could produce a few test points (Thrust v Watts) for interim power levels (ie in addition to the condition where the system is 'balls-out'). This would enable us to observe how the overall efficiency (grams/watt - g/w) changes with load on the fan - we (should) expect to see much more efficency at lower power levels... the interesting thing will be 'how much more?'. Such data could then be used to configure/dream-up ways to predictably operate the fan at the more efficient end of the power curve - probably using 5S batteries (for lower heat losses in the motor) but using lower power outputs from the ESC. Such an idea is not without some potential problems though - i'm relatively new to electric power systems, but gather that operating some ESCs (for sustained periods) at less than max power can sometimes lead to ESC over-heating... though i've no experience of this in my operation of propeller aircraft so far. (Would be interested in any thoughts/experience on this) Anyway - thanks in advance to anyone who'd be prepared to have a go at producing some data... ... a Thrust v. Watts 'curve' would be even better, but perhaps that's a bit much to ask ![]() Rgs to all, Andy ps: From observing ALL your data on the CS 10 thread - my hunch/gut-feel/extrapolation is that on: - A 5S 3300 25C battery - Operating at around (say) 70~80% max watts - Using the new 12 blade fan - We might achieve efficiency levels approaching a g/w of 2.4(ish) - Which would give us excellent duration, at modest thrust (which is what i'm after) Ambitious?... Probably... But I'm an optimist!
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Quote:
On the 10 blade rotor, the diameter of that ridge is 26.56mm. The diameter of the entire rotor face is 29.62mm. The inside diameter of the Tams washer is 26.62mm and the outside diameter for the Tams spinner is 29.51mm. On the new 12 blade rotor, the diameter of that ridge is 27.86mm. The diameter of the entire rotor face is 30.53mm and the outside diameter of the Change Sun aluminum spinner is 30.53mm. I did these measurements with my small digital caliper so they may be off in the hundreth mm area. So it looks like the Tams washer doesn't fit that circular ridge, and is also smaller in overall diameter. In addition, the Tams spinner is smaller in diameter than what is needed for the 12 blade rotor. So either Tam has to make a new washer which fits the new Change Sun aluminum spinner or a new washer and spinner. Also, with these pretty small differences, you are also probably right that Tam could just turn down the washer a bit so as to fit the circular ridge on the 12 blade rotor, but then you would have to also use the Tam spinner (which are nice but I'm hoping to be able to use these $2 aluminum spinners from Change Sun). Sorry for the long post. |
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Joined Oct 2012
5 Posts
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Hello guys,
I've received my new 12 blades CS version and would like to say the differences about spinners but it seems Alexander has been faster than me ![]() I've ordered two alum spinners to try the second one in my CS10 blades but there's effectively too much clearance and the spinner is not well centered in the CS10. I've also noticed that the new one has a better centering than the CS10 (the centering ring on the new CS12 is more prononced than the CS10 and so when you put the spinner on you really feel a good "clip". The material seems to be different too, and what strike me the most is the shroud, which is completely different (there's 6 stators (or 8 I can't remember and it's in the garage now so I have to check tomorrow), and the cylinder where the motor fits has grooves on it (better for cooling but I guess it won't deform and cause bad centering of the rotor in high stress) The housing has two external rings too to increase rigidity I think whereas the CS10 didn't, and there's no Change sun engraving like his sister. Hope you'll understand my english :-) Have a nice evening everybody Rdgs Aurelien |
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