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Old Sep 07, 2012, 08:57 PM
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noise maker for electric outrunners

Hey guys,

I've been flying for a long time, all brushless outrunners that are smooth and quiet. My buddy shows up with a HZ supercub (brushed, gearbox, etc). While this is inferior to my outrunners, I LOVED the way I could hear the 'rpm' of the motor and also, how to prop stopped when throttle was cut - seeing it float in with a still prop was kinda cool.

My outrunners are so smooth, the prop just keeps going when throttle is cut due to no friction.

I came up with something, wanted to get some feedback. The idea was to put something in the way that the prop would strike every revolution so I could hear the motors RPM's. I put a little zip tie that extended into the path of the prop. It doesn't damage the prop, neither does it seem to decrease flight time.

It is actually pretty cool because it gives the cub a 'scale' like sound of a tiny little motor in flight. I really like it. However, I was wondering if anyone has done anything similar or know someone who has? OR, does anyone have any better ideas than a zip tie to achieve this?

here's some pics, you can see the zip tie extend out from the cowl and a few mm into the props path. It bends out the way pretty easy when the prop hits it.



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Old Sep 08, 2012, 07:47 AM
An itch?. Scratch build.
eflightray's Avatar
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I bet you also used to have a piece of card running against the spokes on your push bike, to make it sound like a motorbike.

To stop the prop, have you tried setting the ESC's brake to On.
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Old Sep 08, 2012, 09:19 AM
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Lol. You hit the nail on the head! That's exactly how I rolled as a kid! Lol.

Yea, I could set the brake on the esc, but still doesn't address the lack of sound from the motor.
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Old Sep 09, 2012, 02:18 AM
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Lets hear it then ?
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Old Sep 09, 2012, 08:02 AM
An itch?. Scratch build.
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For you next model get one big enough for one of the sound system that some of the sale guys are using, there are a few out there now. You can get just about any engine sound, inlines, radials, rotaries, probably also turbines. Here's just one -

http://www.mrrcsound.com/

Scoll down and play the video, there are also quite a few videos on Youtube, the warbirds sound really sweet.
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Old Sep 23, 2012, 08:15 PM
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Thanks for that link,just the other day I was wondering about sound.The ziptie trick is awful easy to try,hmm...I'll be back
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Old Sep 24, 2012, 01:52 AM
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Quote:
Originally Posted by maurice076 View Post
Thanks for that link,just the other day I was wondering about sound.The ziptie trick is awful easy to try,hmm...I'll be back
Please post the Audio Maurice
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Old Sep 25, 2012, 01:58 PM
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How about a nitro engine! LOL
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Old Nov 08, 2012, 11:25 AM
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I've done something similar by taping "tabs" on the motor can then pushing drinking straws through the firewall. The longer/wider the straw, the deeper the pitch. You could take it a step further and make a resonator box to amplify the sound.

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Old Nov 08, 2012, 11:45 PM
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...I would imagine that these devices would be introducing vibrations that could be unwanted, possibly damaging ?
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Old Nov 09, 2012, 01:27 AM
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Quote:
Originally Posted by warhead_71 View Post
I've done something similar by taping "tabs" on the motor can then pushing drinking straws through the firewall. The longer/wider the straw, the deeper the pitch. You could take it a step further and make a resonator box to amplify the sound.
Nice drawings! Got any close up video footage of the straw method in action ? would love to here this and also to see if there is any vibration problems.
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Old Nov 09, 2012, 09:12 AM
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Not any more. I had it on a 33" foamie Pitts (Sapac) and it worked great.... no vibrations... the straws and fins are flexible enough that they absorb all of the impact. And the "fins" also help keep the motor cool, swirling up the air inside the cowl. The idea is to position the straw at just the right distance that the fins just barely flick it.... it's not a heavy interference.

It's very simple to test: remove your prop (for safety), then tape a fin on the motor can, then run the motor up while you hold a straw (or anything else) into the path of the fin. I used a straw because its durable and flexible and gives a hollow "pop" whenever it is struck.

Instead of a straw, you could use a bamboo skewer that drilled/glued into a wood firewall, and build a "resonator box" that helps amplify the sound. Even a small cardboard box will do. If you think cardboard doesn't make a good resonator, check this out:

Cardboard Upright Bass (0 min 54 sec)
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Old Nov 27, 2012, 09:56 AM
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Just some follow-up. I used credit card "tines" instead of straws but you get the idea. Dental flossers would have worked great too.

Dynam Waco YMF : Noisemaker (2 min 0 sec)
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Old Mar 29, 2013, 08:15 PM
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Great idea! I love the straws in the firewall and tape on the outrunner casing. I will try that. Seems like it will work well. My zip tie idea doesn't last because the zip tie breaks.

Anyone else got video of the straws and tape method? Or a different method all together?
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