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Post by tommy1800 on Apr 12, 2011 20:30:37 GMT 1
Does anyone have any information, ie thrust, pitch speed, amps, etc., for the stock motor using a 7x4, 7x5, and 7x6 prop?
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Post by flydiver on Apr 13, 2011 1:04:44 GMT 1
Doubt it. Those would be pretty small and have marginal thrust for flying a Cub.
Have some other application?
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Post by tommy1800 on Apr 13, 2011 15:33:50 GMT 1
Ya, I put the stock electronics on a foam jet. AUW is 16 ounces. Do you think i'll be able to get enough thrust with a 7 inch prop? I just finished it last night and going to fly it tonight, i have three different 7 inch props to try, i hope one of them has enough thrust to get her in the air. Any thoughts from anyone?
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Post by ginginho on Apr 13, 2011 16:13:23 GMT 1
Ya, I put the stock electronics on a foam jet. AUW is 16 ounces. Do you think i'll be able to get enough thrust with a 7 inch prop? I just finished it last night and going to fly it tonight, i have three different 7 inch props to try, i hope one of them has enough thrust to get her in the air. Any thoughts from anyone? 16 ounces, I assume that's the same as ours and about 450 grams. I'd suggest trying your highest pitch prop, I doubt that it'll pull more than the stock props so would hope you don't cook the ESC. As to whether it'll work, difficult to say. Remember that because the prop is effectively a circle (when spinning) or a fucntion of one, the surface area that is pushing air is reduced by a factor that is based on the diameter size and Pi (the old Pi x r x r). Also the area that is missing (from a 9/10 inch down to 7) is the area that does the most work at shifting air. |
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Post by flydiver on Apr 13, 2011 16:22:35 GMT 1
Did you use the gearbox? Makes a HUGE difference.
On direct drive you can maybe use a 6x3 - 6x4 prop-pretty much the same as the old brushed Stryker.
7" will be too big direct drive though > burn up unless you go to 2S.
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Post by tommy1800 on Apr 13, 2011 16:43:38 GMT 1
I'll try using the highest pitch prop i have and just throw her in the air i guess, if she flies she flies. Yes, i did use the gear box, it was a lot easier to mount that way. If i can't get enough power with the gear box i'll probably take it out and run direct drive and use a 6 inch prop like you recommended. That will be more difficult to mount, and i'll have to remove the gear on the motor and put like a prop adaptor on or something. Do you know if that gear can be removed? I think it will only have like a half inch to work with to put something else on there, is that going to be enough room for a prop adaptor? Thanks for the input.
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Post by flydiver on Apr 13, 2011 18:39:23 GMT 1
You are going to have jet with a low speed, high torque setup running too small a prop. It may fly...maybe, but a jet it is not going to be.
You should be able to use a collet adapter on the stock shaft or even a prop saver. There are LOTS of ways to mount motors. You may have to re-think your system.
FWIW a motor package on a jet of that weight is not a match made for nice flying. You have a brick on the back of it. You will need a LOT of weight up front to get the CG and this will make for an even worse setup. The whole idea is kind of questionable. But, you certainly do learn from that kind of endeavor.
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Post by tommy1800 on Apr 13, 2011 20:33:59 GMT 1
I kind of knew all that before starting the endevor, but i had the super cub stock parts laying around and had never built a jet before and thought i'd give it a try. You're definitly right about it being a learning experience. I just hope that it's not a total flop. I'm guessing that i'll be switching to direct drive, but i thought it'd give it a try since it was just so easy to mount. Thanks for the input, i'll post again after i fly and tell ya how it goes.
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Post by tommy1800 on Apr 19, 2011 16:59:10 GMT 1
I tried the full range of 7 inch props and couldn't get the jet in the air using the stock motor and gear box. I modified the jet to be able to use the stock 9x6 prop, and it still didn't fly much beyond 30 feet or so. What did i learn? I need more speed. So i'll remove the motor and gear box and run the motor direct drive, probably using something like a 5 or 6 inch prop. The conversion will take some doing, but i'm determined to get the jet flying. The total weight with the super cub stock motor and gear box was just shy of 17 ounces. By removing the gear box i suppose it will bring it down to maybe just under 16 ounces. So...lighter...more speed...i'm thinking she'll fly this time. Any thoughts out there? I'll let ya know how it goes.
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Post by flydiver on Apr 19, 2011 17:19:36 GMT 1
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Post by tommy1800 on Apr 19, 2011 17:36:58 GMT 1
Thanks, i looked at those mounts and i'm gong to try and build something similar to that stryker mount.
I'm using the stock battery and esc, do you think i'll need to prop down below the 6x4? You don't happen to know the capacity of the stock esc do you? I'm just trying to use stock everything because i'm putting money into other planes that i know are going to work great, this is just a side experiment, no cost, trial and error build...just because i can.
Also, thanks for the tips on removing the gear, i've got a dremel, so i'll take that to it tonight.
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Post by flydiver on Apr 19, 2011 17:57:27 GMT 1
The answer - about 15A (educated guess, no data available). It will NOT be appropriate for this application. You'll likely burn up with a 6x4. ONLY way to tell for SURE is a wattmeter. You'll probably need to prop down to like 5x3. Now you'll be lacking power/thrust most likely.
Specifically-what jet are you putting this on?
FWIW I've kept all my old 27MHz stuff out of a Stryker and Aerobird. I thought I'd find a use for it. Years later it's just sitting. It's not worth selling, or hardly even giving away with shipping costs. It doesn't appear to be worth using for me since I don't. I have better stuff for anything I might use it on.
I did try the Cub stuff in a Slow Stick. It was a pain as the controls were reversed and there were only awkward work-around. That didn't last long.
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Post by billwiththeb on Apr 19, 2011 23:47:34 GMT 1
Hi all,i have a 2208 2200 kv and a 7x3 on my super cub.30 amp speed controll.3 cell lipo 2500 mah 20c. it is awesome.it is direct drive.prop saver. im sure 7x4 would be better. the batts do get warm. i have a pc heat sink for cooling glued on,keeps it cool as can be. but it flies great. Great climbing power. But a rc timer2212-2200 kv would be perfect for it.my wild hawk is about the same weight as the super cub,and it pulls my hawk awesome fast,with a 6x4. mine isnt near stock but the main part of it is. this bird is a good beginner plane. very stable and will pull off stunts if you can do them.
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Post by flydiver on Apr 20, 2011 1:49:00 GMT 1
Hi all,i have a 2208 2200 kv and a 7x3 on my super cub.30 amp speed controll.3 cell lipo 2500 mah 20c. it is awesome.it is direct drive.prop saver. im sure 7x4 would be better. the batts do get warm. Neither your motor nor your batteries are long for this world. Too small a motor, too large a prop for the KV. You are over driving both, esp. the motor. My guess is 1/2 your power is going straight into heat production. That's essentially a jet motor. It's used on the easy star due to space limitations. The ES also has WAY less drag than the Cub so the work load is not as high. Oh yes, it works, but it's not very efficient. Not the info a new enthusiast is keen to hear...but, there you are. |
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Post by billwiththeb on May 14, 2011 3:03:12 GMT 1
Yeh the motor does get warm and the batts have gotten real hot,the esc is fine the heat sink helps tons.im using a 6x4 now it seems to help with heat but still needs bigger motor.what do any of you guys think i need.i want power and speed.rctimer is where i buy from.what do they have that would be awesome.Ide like a 8x4 on it 0r 7 it seemed ok but got my batts real hot,after 10 minutes to.2400mah 20 c 11.1 3s 30 amp esc.it works but yah the stuff gets mighty warm,it is cheep china stuff lol.
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