Cox .01 /.02 /.05 /.09 /.15 Speed Planes

Look how small that exhaust header is out in the big world.

Used the same prop as with type 2 testing the FIRE engine
The type 1 with the groove made more rpm

Static in the hand 23,920 rpm / 102 mph pitch speed.
+503 rpm over the pure single exhaust manifold with pressure tap.

Tossed the plane up and away on Sunday for a test the engine ran fine but the
angle on my cam on the hat was not adjusted right and I had more ground than
sky only time it  showed on vid was take off and landing. I had the angle still adjusted
from when it was sitting on top of the radar gun. Landed down wind and tumbled the
vertical stab loose / had no CA glue to fix it. Vertical stab has a ply footing so tough to
snap loose, did a good cartwheel / clean break.

Power / rpm was good will save the juicy top end info for the next
vid effort really must see it in action running at full scream. Might
have to get me a rebate run on vid after work, a whole week of waiting
to post a good vid is painful.

The mufflers from FORA are simply mufflers, not tuned pipes. They have class rules that force them to use mufflers with a max outlet diameter. The shape you see is an optimisation within the class rules, there is no net gain from using these mufflers, on the contrary, there was a drop in rpm when the rules change to a smaller outlet diameter in the past.

You can find some more info here for instance:  http://www.f2d.dk/rules/venturimufler.htm#2011rules

Yes true, which lead to improved designs such as tuned silencers prompted them to maintain as
much power as possible. Here are some more various efforts. The idea was if a muffler is of interest
for the screaming TD .020 these progressive shapes are worth showing. Last one's for fun imagine
if you could shine one up like that rendering.

Pics

Better passes in this clip from Sunday morning.

1440p HD



AmpAbuser / AKA 1/2A Nut
Published on May 28, 2018

TD .020 / 3.37 x 4.5 Prop 28,585 rpm / 122 mph pitch speed.
Nano IV testing props quick clip of some passes with this prop.
Static in the hand at launch 23,192 rpm / 99 mph pitch speed
3oz thrust / .052hp / 38.8w good power / prop combo for speed.
Needs some back cut on the blades to hit 30k. Radar read at 114 mph
Engine cooled and went richer after the last pass need to lean up another
3 to 4 more clicks yet to compensate.

Also noted by the time the plane went past the radar gun by the camera it had lost
some speed per Doppler: 105.652 mph or 170 kph of course this is + or - variance.
Radar can pick out top end speed quite a ways out from the shallow dive. I will have
to work on getting the apex of the speed closer to the cam. Interesting to compare
3 forms of data now: RPM Prop Pitch Speed / Radar / Audio Wav. Doppler.

Thank you Eric, it's getting there and has been a good test bed for TD .020 parts.
It's down to messing with prop sizes now. Good balanced prop helps it to sing some
rpm. Hope to bust 120 on radar next effort out to the field.

FYI sneak peak time on the TD .020 muffler.

Arrived currently with two outputs to test. The canister style muffler should allow
good expansion room, weight is very low and did not even bother to measure yet.
All up weight with engine 32g as shown with the Cox grey prop.

A barb is incorporated to allow the option to attach a silicon diverter to minimize goo
on the airframe and diversion for cowled engines. Will vid test perhaps tonight.
Will at some point add a pressure tap. The smaller exhaust nipple should be quite
enough to fly in your back or front yard with no fuss from the neighbors. Precision
fit and finish locks down with zero movement completely sealed up. With a RC carb
this will truly be the ideal micro RC engine. Carb will be ready to test soon. As is
even with a venturi the muffler is a most worthy add on. There will be a dedicated
thread for the full RC engine version once all the parts are here to test.

Published on May 31, 2018
Pre production test CNC Muffler TD .020
First test of the muffler there will be a RC carb soon to be tested
as a combo option. No leaks works very well engine was drip free.
NV was the same setting as the carb test no tweaking yet.
When the carb shows up will work on top performance of the
set up with power data. Beautiful wee lil muffler what a treat!!

WaW !! ... that's a very interesting friend !!

This is good ... I imagine a combo of pieces to update the tee dee .020 !! ... what beauty, what a pleasure !.
Thanks Brad for your time and efforts!

Thank you but I was only in the design idea side of things, Greg was able to breath life into the project
and has done a most excellent job at that! Should be a + add item for most. It will allow a pressure tap and
give solid steady needle runs.

Pic just for fun pipe is 2x too big in volumn but the dream is there, soon I hope will have a special header

Brad will this muffler fit thick wall cylinders only or the old stock stepped wall too? And the RC carb will also be sold by Greg?

The issue of thin wall cylinders is something I'm not sure about. Looking around to see what's available on Ebay, I see maybe 25% of 020 have thick cylinders. I worry thin cylinders will accumulate oil in the gap and this could be problematic in storage or the next time it's started.

The simple shape of the muffler outlet is mostly to test for losses associated with outlet area. The end product could be as is, or out the side like NV mufflers. Out the side is more work/cost.

Greg

Here are the two primary types still in the most circulation
The early thin walled ones I do think will work, the dia. is
less, creating a gap at the exhaust port.  Oil will puddle
down as Greg mentioned, crust up over time if left to sit
for years.

These two styles have the same dia. at the exhaust ports and
will have no issues. The thin walled ones where later beefed up
to avoid cracking around the exhaust port which happened more
so for the .049 cylinders. Could have a aluminum shim ring
that slides on to fill up the lower section bellow the exhaust port
to stop ponding of oil. Would have to have a slit to compress down
around the gap after it clears the skirt.

Painting a picture here for now this is a taste.




Published on Jun 1, 2018
Pipe is 2x too big in volume just doing a sound check.
.020 pipe will be tested soon with a dedicated air tight header.
It will be some kick arse micro IC fun for sure!

gkamysz wrote:The issue of thin wall cylinders is something I'm not sure about. Looking around to see what's available on Ebay, I see maybe 25% of 020 have thick cylinders. I worry thin cylinders will accumulate oil in the gap and this could be problematic in storage or the next time it's started.

The simple shape of the muffler outlet is mostly to test for losses associated with outlet area. The end product could be as is, or out the side like NV mufflers. Out the side is more work/cost.

Greg

Thanks Greg for all this development, I sincerely hope it is a success in every way.
I ask: is there the possibility that in your projects is a ring specially designed for TD .010 as seen in the photo ?, I think this is composed of two parts plus a ring that embraces the two parts ... it would be interesting and I think that to many could mean a desire to have it....

Yes that takes two half's then the throttle sleeve is held together with a C clip.
Or and I have some of these type sleeves for Cox 15's:
You put two inner half's around the cylinder so you can slide over the solid sleeve.
Those half's have slots for the exhaust ports the outer sleeve is keyed into place so
the entire assembly moves in unisense.

This would be easy to do:
How about a air choke throttle for the TD .010 and a header or full muffler with pressure tap for steady rpm.  
.010 to .15 cox engines could have upgrades for RC use.

1/2A Nut wrote:How about a air choke throttle for the TD .010 and a muffler with pressure tap instead Mauricio?

I like it !! ... I hope that the costs allow it to be accessible, everything that is worth 1 dollar there I must add 55% more to obtain it here!

Published on Jun 1, 2018
TD .020 Muffler Performance Test 3.75 x 3 / best peak 21,237 rpm
Static: 4oz thrust / 31w /  60 mph pitch speed.
25% nitro / 20% castor - will be testing with a pressure
tap next to compare.

Impressive output considering a muffler is attached.
Should unload around 26 to 27k / Low weight prop helps
to keep the weight down with the G-Mark carb.


Update have the pressure nipple installed

It looks like that exhaust throttle was made by Steve Adams and sold for 40USD 15 years go. Do those hold up well in use? I don't think I've seen them before. It's not a very complicated assembly, but maybe there is something to it I don't see yet.

Greg I have one of those exhaust throttles they work fine. A slip on effort
would be fine if folks would file down the footing at the base of the cylinder.

Here is the new muffler (fits fine) on the plane will fly Sunday with it see how it does
unloaded with a pressure tap. Will test one without pressure too when able. 4.47oz as shown.
The attention to muffler mass has paid off nice low weight add on perfect!



Some pluming loss using smaller TD .010 fuel line inside the fuselage needing the thicker walled
silicon tube to navigate the sharp bends. The pressure tap helps to regain some of the losses.
Without too much fuss was able to sustain 21,075 rpm with the 3.75x3