RichT
Flying officer
Posts: 7 
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Post by RichT on Nov 19, 2008 19:27:04 GMT 1
I did a lipo conversion (with LVC switch) a few months ago (best investment in fun) and now preparing for a radio / aileron / brushless mod. So purchased a Watt Meter.... The Wattmeter arrived yesterday so I thought I'd do a few quick tests and the results were quite amazing. All testing was with the same Master Airscrew 10x6 prop. Stock 7-cell NiMh 50% throttle = 3A and 28W 100% throttle = 6.5A and 55W PZ 8-cell NiMh 50% throttle = 4A and 39W 100% throttle = 8.4A and 72W 3s Lipo (1500mAh, Zippy 20-30C) 50% throttle = 5A and 55W 100% throttle = 12.5A and 131W You can see the decent impact of going to 8-cell and the huge leap in performance in going to a Lipo. This explains why I'm totally comfortable cruising at 50% on the Lipo.... its the same power as a WOT on the 7cell.  I'll be experimenting with difference props when I get some time. |
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Post by flydiver on Nov 20, 2008 3:25:16 GMT 1
If you still have the stock prop running that data on the NiMh would be useful. People are always looking for stock performance.
The SC stock prop is a pretty large blade 'slow flier' type and will draw a lot more amps. That's why it shouldn't be used with 3S lipo-draws approach 20amps.
fly
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RichT
Flying officer
Posts: 7
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Post by RichT on Nov 21, 2008 19:20:19 GMT 1
Ok here are the numbers for the stock SC prop. All batteries were fully charged before testing.
HZ Supercub 10x8 Prop
Stock 7-cell NiMh
50% throttle = 4.37A and 39.9W
100% throttle = 10.07A and 83.4W
PZ 8-cell NiMh
50% throttle = 6.05A and 59.7W
100% throttle = 10.94A and 95.1W
3s Lipo (1500mAh, Zippy 20-30C)
50% throttle = 6.82A and 83.2W
100% throttle = 18.37A and 212.7W
As you can see why the Lipo at WOT is like hyperdrive.... 18Amps and 212 watts is a lot of power to be pushing through the controller... if you try lipos, prop down.
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Post by flydiver on Nov 21, 2008 21:03:56 GMT 1
Thank you for that work an ifo. I'll be bookmarking this page and pointing new folks at it that are still trying to grasp how the lipo/power/prop thing works on the Cub.
fly
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Post by duck9191 on Nov 21, 2008 22:59:03 GMT 1
kinda wish i would have stuck with the stock motor for a bit after i went lipo. would have been neat to see how it performed. owell 300watt's brushless was fun too lol. good info though, im sure it will be useful to many.
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Post by flydiver on Nov 22, 2008 0:37:01 GMT 1
The stock system with a 10x6 prop performs pretty well. There is some efficiency lost in a brushed motor, some lost in friction in a gearbox, and some gained by using the gearbox.
I did a comparison of a Towerpro motor (2410-09) vs. a brushless inrunner in a 6.6:1 gearbox and some 'lame' NiMh batteries. Used a Slow Stick and the same prop.
The TP wouldn't even take off. The gearbox system would fly the SS for > 5 minutes with the same battery.
It's not an entirely fair comparison since it's apples to oranges. OTOH the subjective experience is about flying and enjoying it. Both systems were ~10A units, both were spec'ed for that prop size. The TP motor is relatively cheap and inefficient, the inrunner was an eflite-hacker so was more top end. The gearbox was stock cheap GWS. I'm still running that GB on the SS. The only thing I don't like is that GB noise.
NOTE-notice that WOT power draw with the stock prop. The electrics will NOT take that for long if run wide open much. PZ does not publish data for the ESC but I doubt it's much over 12A cont.
fly
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flyer88
Squadron leader
Flyer88
Posts: 165
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Post by flyer88 on Dec 10, 2008 3:03:52 GMT 1
Don't even bother with other batteries....go straight to 3cell Lipo.
Great power and less weight too.
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Post by flydiver on Dec 10, 2008 5:05:47 GMT 1
Potentially less weight. Seems most folks go straight to 2200 3S. Those weigh the same as a 7-cell. The extra power more than makes up for it.
A few folks use like 1200 that actually fit in the battery box. Way more performance and a bit less flying time generally cuz they can't resist the ability to hot rod. Biggest problem with smaller batteries is the potential for excess draw unless you pay attention to the C-rating and prop draw.
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Post by Dillzio on Aug 19, 2009 10:53:36 GMT 1
Wow, what a great reference.
I checked part numbers, and the orig super cub uses the same motor as the super cub LP, so we can assume that these ratings apply to the super cub LP too.
Stock super cub LP batteries are 15C 1300mah, so they can provide 19.5 amps constant. This falls just within range of the 18.4A reported for what this draws with the "stock" 10 x 8 prop. The stock super cub LP only has a 10 x 6 prop though, so probably draws closer to the 12.5A quoted for the Master Airscrew prop.
One would like to think that the stock ESC could deal with this sort of power, but the consensus seems to be that this is not the case, so sticking with the 8 x 6 prop on the Lipos seems to be a good idea. HZ do however recommend using the 10 x 8 prop if you fit the floats- how long the stock ESC will hold out with 18.4 amps running through it is anyone's guess.
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Post by cubster on Aug 19, 2009 18:16:54 GMT 1
Wow, what a great reference. I checked part numbers, and the orig super cub uses the same motor as the super cub LP, so we can assume that these ratings apply to the super cub LP too. Stock super cub LP batteries are 15C 1300mah, so they can provide 19.5 amps constant. This falls just within range of the 18.4A reported for what this draws with the "stock" 10 x 8 prop. The stock super cub LP only has a 10 x 6 prop though, so probably draws closer to the 12.5A quoted for the Master Airscrew prop. One would like to think that the stock ESC could deal with this sort of power, but the consensus seems to be that this is not the case, so sticking with the 8 x 6 prop on the Lipos seems to be a good idea. HZ do however recommend using the 10 x 8 prop if you fit the floats- how long the stock ESC will hold out with 18.4 amps running through it is anyone's guess. no mate,,,the prop size of the SC in both versions is: 9 x 6 have another peek: hobbyzonesports.com/Products/RelatedParts.aspx?ProdID=HBZ7300&Category=Parts%20Listingcheers |
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Post by flydiver on Aug 19, 2009 19:40:29 GMT 1
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Post by cubster on Aug 22, 2009 14:38:38 GMT 1
Yea Rich and others,,,your quoting specs on the WRONG PROP!
the sc uses a 9/6 gents,,,not a 10/6, not a 10/8
cheers
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Post by flydiver on Aug 22, 2009 16:46:10 GMT 1
The NEW LP Cub uses the 9x6.
The test above were before that plane even hit the market and folks were trying to figure out how to upgrade to lipos.
Look at the original date on the posting.
In typical PZ fashion they make NO useful power or electrical specifications available at all.
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Post by Dillzio on Aug 24, 2009 13:47:34 GMT 1
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Post by flydiver on Aug 24, 2009 16:46:05 GMT 1
The ampaviator test was done on the OLD non-lipo system also.
Look at the dates, it makes a difference.
A prop is NOT just a prop. It depends very much on the brand and STYLE of prop.
The 10x6 is a 'direct drive' or e-prop. It is relatively thin. APCe (thin electric) is the relative equivalent.
The fatter props with the smaller hubs are slow fly. They produce more thrust, eat more amps (no free lunch here), and ARE RPM LIMITED. That means if you spin them TOO FAST they can break.
The 10x8 GWS-SF props are OK on the old/stock/geared NiMh Cub. On a 3S lipo powered Cub they audibly distort (sound terrible) and are at risk of breaking. On a higher RPM brushless Cub they are potentially an accident waiting to happen.
I have not seen the new 9x6 but my suspicion is that it's a slow fly (fat, small hub). The 10x8 stock is definitely a slow fly.
FWIW a 10x6 GWS-HD is almost exactly the same as an APCe 10x5 performance-wise. So in props, like advertising, numbers can lie.
Some slow fly props at almost the same size as a direct drive will pull 2x the amps. Does that make it better? Only if the motor and electrics can handle it. If not all you get is toast.
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