Thread Tools
Nov 20, 2012, 12:01 PM
Registered User
Question

Cox .049 Sound Level


Anyone have an idea what the sound level of a Cox .049 would be, reed valve to TD? I'm planning on scratch building several of the models popular when I got into RC years ago and am toying with the idea of doing at least one of them with a period engine. Most will certainly be electric but I still have a fondness for the buzzy little buggers, despite their shortcomings.

Problem is I fly at a field that has a strict 94dB limit. I recently sold my big one, a 1/3 scale 50cc Sig Spacewalker, partly because it was just too much of a hassle hauling it around, but mainly because it was too loud. It was checked at 100dB so it was WAY over the limit and I didn't want to mess around with trying to make it quiet enough to fly there.

I have a fairly large collection of Cox engines from the TD .010 all the way up to TD and Medallion .15's. I have a few different mufflers for the .049's but as I recall from a few years ago they don't make a tremendous difference.



Mike
Sign up now
to remove ads between posts
Nov 20, 2012, 12:39 PM
Registered User
I think my TD .049 measured around 90 db at 15 ft. A B Bee would be less. There are free APP's for db meters if you have a cell phone. Someone at the field will usually have one if you don't. There are mufflers available too, but they suck power. I think the .15 will go way over without a muffler. Props make a difference too. A 5-3 will be louder than a 7-3.
Nov 20, 2012, 01:07 PM
Registered User
The spec is 94dB @ 9 feet. I'll probably have to check it out for myself to be sure. I believe our sound level meter is kept locked up at the field and if not I'll have to check out the App. I'd rather not end up going to all the trouble to put something together with a Cox engine on it only to have to swap it out for electric after the fact. Especially since I don't need to worry about a fuel proof finish for electric. I live in an apartment so working with noxious solvent based paint is a problem.

Yeah, I would imagine the .15 or even .09 would be way more than an .049 and I am aware that mufllers don't work well at all on any engine using sub induction so that leaves out the possibility of a muffled TD.
Nov 20, 2012, 09:13 PM
Registered User
I found that the rotating throttle sleeve type throttle make a genuine noise difference, on a reedy at least. Mufflers do work.. some.. just that they reduce power so many find that unacceptable Don't be forgetting that Nitro content increases noise significantly as well.
Try a Cox on No Nitro fuel for a noise surprise. The grating scream isn't there, v nice. Add a muffler and noise is no longer an issue.
But power is down somewhat. Less than I had once thought it would be, but still reduced..
Nov 20, 2012, 09:13 PM
Registered User
Holy cow, I may be missing the boat, but a TD 051 turning 21,000 rpms is deafening. Have a hard time thinking it would make the DB limit????? I have never put a meter on one, but I have not heard any other motors with mufflers louder and I have heard of them not passing the DB limit. Good luck and please let us know what you find out. Get rpms as well.

John
Nov 20, 2012, 09:17 PM
Registered User
Underthetire's Avatar
Just a guess, 108db at 9ft.
Nov 21, 2012, 11:29 AM
Registered User
Quote:
Originally Posted by Bare View Post
Don't be forgetting that Nitro content increases noise significantly as well.
Try a Cox on No Nitro fuel for a noise surprise. The grating scream isn't there, v nice. Add a muffler and noise is no longer an issue.
But power is down somewhat. Less than I had once thought it would be, but still reduced..
Yes I am aware that nitro does make an engine louder. The problem I see is if I were to run low or no nitro, especially if combined with a muffler, will greatly reduce the power level. Plus low/no nitro often makes for a tricky to set needle, especially on the small Cox engines.

I'll probably just say to heck with it and just go with electric. I'm thinking about doing some glow free flight. There's a nearby club that flies free flight, the Bong Eagles. One of the sites they fly at is Bong Recreation Area and there noise shouldn't be a problem. I fly High Power rockets there and they're loud!



Mike
Nov 22, 2012, 12:02 AM
Cox Engine Hoarder
Jason_WI's Avatar
I think the TD 049/051 is the loudest of them all as I have run a TD 15 special MkII and it did not seem as loud as the TD 049 pulling 20k on a cox grey 5x3 prop. I think pitch has everything to do with it being louder.

The Cox geared twin Golden Bee I have has some bark to it.

Cox Geared Twin using Golden Bees (2 min 28 sec)
Nov 22, 2012, 06:31 AM
Registered User
Hi,

We have the same problem here, still looking for a cox dragonfly to measure and confirm that its legal to fly here. ( below 94db @ 3 meter )

I'm going to test run and measure thrust, rpm and sound level etc, for killer bee (donated from a nice gentleman ) . still waiting for the parcel to arrive here. I will post it on my coming web page soon, will share with you all later.
Nov 22, 2012, 11:18 AM
Registered User
I've read that the .049's are actually quieter than the larger engines, but the pitch generated by the higher RPM's leaves the impression that they're louder.
Nov 22, 2012, 12:15 PM
Registered User
RknRusty's Avatar
Quote:
Originally Posted by Andrew0820 View Post
I've read that the .049's are actually quieter than the larger engines, but the pitch generated by the higher RPM's leaves the impression that they're louder.
EDIT: (I stand corrected) High pitch sound travels a shorter distance.

Is there any freeware pitch meter for a desktop PC?
Last edited by RknRusty; Nov 23, 2012 at 07:00 PM. Reason: Changed incorrect statement
Nov 23, 2012, 04:02 AM
Registered User
surfer_kris's Avatar
Large gas engines are the worst in the air I think. I sure can't hear my own (1/2a) engines when they are up. I think lower frequencies travel further, while a cox engine has a more annoying sound that only a mother can love...

There are other engines that have mufflers and a far more quiet than a cox engine. The TT07GP for instance has a proper muffler and is fairly quiet in its stock version.
Nov 23, 2012, 05:14 AM
Registered User
Yes, lower frequency means longer wavelength, and travel further. Elephants can communicate miles away using sub- sonic lower frequency. We fly 1/2A planes not far away as bigger planes do, thats why cox engine has a more annoying sound






Quote:
Originally Posted by surfer_kris View Post
Large gas engines are the worst in the air I think. I sure can't hear my own (1/2a) engines when they are up. I think lower frequencies travel further, while a cox engine has a more annoying sound that only a mother can love...

There are other engines that have mufflers and a far more quiet than a cox engine. The TT07GP for instance has a proper muffler and is fairly quiet in its stock version.
Nov 23, 2012, 04:09 PM
Registered User
gene6029's Avatar
.

Quote(The Cox geared twin Golden Bee I have has some bark to it.)

Thats MUSIC to my ears!!!......Gene
Nov 26, 2012, 05:56 PM
Registered User
The nice thing about the small planes is that they don't HAVE to be flown at the club field. I think you should make at least one of your planes with a 1/2a. I recently completed a .010 Pageboy and the wow factor at the field was impressive. Now I have a Guillow's 27" Zero (new laser cut version) that is going to get a TD .020. I just love the sound of these small motors.

Tim


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
For Sale Vintaeg Cox Models Cessna 182 RTF Plane Cox .049 RBYM Aircraft - Fuel - Airplanes (FS/W) 0 Jul 23, 2012 10:37 AM
For Sale Vintage NEW Cox Hobbies Green Cessna 182 Skylane Cox .049 RTF Plane RBYM Aircraft - Fuel - Airplanes (FS/W) 0 Jun 19, 2012 03:27 AM
For Sale Cox .049, Cox FF Helicopter, RC10B4, GTB2 ESC, Sonic 6.5, FM Plane Radios, ETC! RBYM Non R/C Items (FS/W) 1 Jun 12, 2012 03:28 AM
Sold Cox Glow Plug Clip / Cox .049/.051 Glow Head High Compression chadbag Aircraft - Fuel - Engines and Accessories (FS/W) 2 Apr 17, 2012 10:02 PM
Sold Cox Medallion RC .049, good, $35.00 wing881 Aircraft - Fuel - Engines and Accessories (FS/W) 0 Mar 07, 2012 05:15 PM