http://www.modelgasboats.com/Magazine_Content/How-to_Articles/Making_a_Muffled_Pipe.html
Because a fellow-boater heard
about my QD-silencer rebuilds ,
he asked me if I could do the
same trick with his pipe.
He bought it as a silent pipe
, but that is measured to the
This pipe (I think a Andy
Brown parabolic silent) is doing 90/92 Db(a) ,
and that is way to much for
the strickter European regulations (80/82 Db(a).
As I did earlyer with the
(European) CMB-Nitro .90 pipe to adept it to Petrol/Gas-pipe ,
I knew that for keeping the
rev's and torque you have to calculate the passageway of the
gasses trough the muffler
quite meticulously.
By trial and error we found
out that a two stage muffler with 150%
square-area stinger-diameter
in the first stage , and 130%
square-area stinger-diameter in the second stage ,
works the best "all"
considered.
That "all" is
effective sound reduction and the slightest power/rev's loss.
So .... these are the
calculations performed for this 'Andy Brown Parabolic-silent'
Sorry for the metric ......
for imperial you have to use a (the) conversiontable
,
and the square-area measure
imperial-arithmetic you have to do it yourself ,
or download and use this great
and easy *Convert program*
by Josh Madison ,
to convert my area-calculations
from mm to inch.
Stinger =12mm Ø square-area measure (PR²) = 113mm²
150% x 113 =169,5mm² / 6
x Ø 6,0mm(28,27mm² x 6)=169,62mm² square-area measure / Front-bafflepipe
130% x 113 =146,9mm² / 6
x Ø 5,6mm(24,63mm² x 6)=147,78mm² square-area measure / Aft-bafflepipe
Where Ø stands for ... drilled holes.
As you can see the 150% is
actually 169,5mm² and the 6 bore 6mm holes are giving a total of 169,62mm².
In small
round objects the drilled holes become bigger , so again by trial and error I
found out
that for Ø 6,0mm the drill has
to be 5,9mm and for the Ø 5,6mm the drill has to be 5,5mm.
Now I have to go to the
metalshop to buy the needed aluminium :
Aluminium-tube : 14mm x 17mm
(to fit over the original stinger)
Aluminium-full : 18mm Ø
( to lathe a divider between the front and aft bafflepipe)
Aluminium-tube : 52mm x 48mm ( as the outer muffler-wall /
'can')
Aluminium-full : 52mm Ø x 12mm ( to lathe the backplate)
Sometimes I get lucky and find
in the metalshop things I need / can / could use ,
in the scrapbin or there are
'left-overs'.
So there are parts on this
picture that are more/bigger/longer as needed.
All parts made the right size
by sawing or lathe. In the tweezers you see the divider.
This is the view of how the
internals fit within the 'can'.
120° drilling and tapping
threads M3 has to be done.
120° drilling and M3
thread-tapping done.
Also reduced the outer
diameter of the 'can' by lathe from 52 to 50 mm.
50mm is the standard European
pipe-clamp size.
Checking the overall fit , and
ready to join by hard-soldering .
The hard soldering of
aluminium is tricky ,
because the melt-down and the
soldering temperature are very close to each other .
The melting temperature of aluminium
depends on the kind of alloy used , and is between the 585ºC and 660ºC.
The hard-soldering temp. is
570ºC and is therefore as strong as silver-solder on SS/Copper/Brass .
The strength of the joint is
16>18Kg/mm².
The materials I use and my
long experience are making it easier.
Marc Levac asked me to
elaborate on this hard-soldering/brazing process , so here it goes :
25 years ago when I was
involved in oldtimer restoration (as a hobby) I came across a welder
who was doing
motorcycle/car/outboard welding on gearboxes , crankcases , cylinderheads , and
outboard-legs .
They also used that Alumiet
163 flux-powder and Vedal 460 brazing-rods.
(A brand of the Dutch
VéDé-products made by Delville and sons.)
These materials are not
commercial available (for private persons) ,
but the regional sales
representative is so kind to sell me their "test/evaluation-samples".
For the brazing a
recommended by that welder ,
because of the "spread" of the flame.
Witch is ideal for doing this
home DIY soldering.
Generally we hobby-guy's do
not have their Acetylene/Oxygen combo's with different tips.
Here you see that a clone-propane
can is used .... the original Spitfire-TurboTorch can is red.
Also on this picture the flux
and the rods ,
and the homemade RV-propane
coupler that is used for time consuming jobs .
And hey ....I'm Dutch ... it's
also much cheaper using the RV-propane.
And this is the way to do the
job :
I took a rod that slips into
the pipe and clamped it (slanted-upwards) in a workbench-vice.
Slipped into a leather working
glove with my left hand.
(That's for to be able to turn
the pipe without getting burned.)
Put the pipe on the rod ,
opened the flux , light the torch.
First heating the rod enough
to stick it into the fluxpowder , so this powder will stick to the rod ,
and then in circular pattern
heating the area of the joint to make.
As to determine the right
soldering temperature , a little piece of the rod is forced onto the joint.
As soon as that forced piece
starts to 'run' , you can go ahead .
Always reminding of keeping
the right temperature by going nearer or withdrawal with the flame.
This is a trick that can be
learned only by practising allot .
Yes .. the trail and error way
again , and believe me .. I practised
and ruined much on scraps.
(and yes ....on actual parts
too L )
Hard soldering done.
You see the joining of the
'can' to the pipe and the muffler-stinger to the backplate.
What you don't see is the
joining of the front and aft bafflepipes with the divider.
Bud that's been done J
View after filing / Dremel'ing
/ sanding.
Same here .... but using the
lathe.
Ready for assembling .
As you can see , for cleaning
purposes you can take it apart.
But as I dislike cleaning , I made
an oil groove and bore in the outerring of the backplate ,
and a bore in the inner-ring
out into the muffler-stinger.
After racing you just put the
pipe on his 'back'.
If the noise is still not correct , Stainless Steel kitchen
scrub can be added. 
Just for display reason , pipe
mounted on my FSR-V15 competition racing hull.
And please don't think my
hobby-room is so clean that it has carpet as you see on the previous pictures ,
just to avoid flashback if
camera wants to flash , the pictures are taken on the floor of my home-office.
My hobbyroom (in cleaned-up
version - ha ha ) can be seen here ; Leftside / Rightside
This article started with the
question from a fellow-boater if I could do the QD-silencer rebuild-trick to
his pipe.
Now I've to fill you in about
that too ?
OK ........ here it comes.
This is an original QD-silencer
after rebuilding it .
Notice the little M3 flathat
hex-bolts instead of the rivets.
The rest of the story :
I 'dremeld' away the 'aft'
rivets and cut M3 in it .
After opening the content of
that thing was ... a tiny roll of 'chickenwire' ,
and some filthy antinoise-Wool
........ filled with oil.
That muffler was 71,3mm long
inside ..the baffle-dish is 30mm measured from the front-outside.
The pipestinger sticks 13mm
into the muffler.
At first I made the flow
calculations @ 150% stinger Ø .(11mm)
Both for the baffle-dish and
the baffle-tube.
Measuring today 84Db(a) ...
with NO loss at all ( No torque NO top).
I could make the flow of the
drilled-tube = 2nd stage @130% , but the owner is satisfied already .
You can't see it well on the
next picture .. but the 'baffleplate' is parabolic (like a
satellitedish-antenna).
Calculations ; (PR²)
Stinger = 11mm square/area
measure = 95mm²
130% of 95 = 123,5mm²
150% of 95 = 142,5mm²
Muffler inner-diam = 36,5mm
square/area measure = 1046mm²
The first stage
baffleplate/dish = 34,0mm diam. square/area measure = 907mm²
1046 - 907 = 139mm² close enough to the needed 142,5mm²
The second stage alu tube is
12x14mm cut down one side to press-fit the backplate and to be soldered later
on ,
the first-stage dish is also
alu-soldered on.
In the aluminium tube are 8
bore 4,8mm holes (giving total
square/area measure of 144mm² =152% stinger diam.
OR (more quiet)
In the aluminium tube are 8
bore 4,5mm holes (giving total square/area
measure = 127mm² = 134% stinger diam.
The dish is made out of 2mm
aluminium plate scissored round with 5mm more diameter as needed.
Then put that round flatplate
on a brick and heat it up with the torch to ±400ºC .
Pick it up with a tongs , and
throw it into cold water , the aluminium becomes soft that way ,
and can easily be
(Teflon)hammered to the required shape in or over a mould.
The soldering to the tube will
re-harden the dish , so it can be adjusted by lathe to the right diameter.
And this is how the internals
looks after the rebuild.
The picture is showing the
first one I did ,
the later rebuilds (and this
one later on) got a reinforcing aluminium-ring of 5mm thick ,
so the M3 bolds have more
'meat' on the threads.
The first-stage 150% with the
130% second-stage is measured @ 82Db(a) .
With added SS kitchen scrub in
the second-stage part it's measured @ 80Db(a) .
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More way’s to do it :
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For the ones that want to keep
their boating-waters , now you have an example how to cut back on the
noiselevel.
Feel free to use these ideas ,
and I welcome real dyno-testings by the pro's.
Hendrick Spoor (aka HendricX)
(as the k and S together in my
language is pronounced X)
Other rebuilds :
Shortening a CMB and PMC pipe about 180mm , to fit a
46”/120cm cat-hull.
Extension on Tom vd Brink’s
& Jack Zeeman’s AB-Parabolic … for use on .45 rigger
Just 3dB to loud … now 1dB
under European 80dB rule J
Rebuilds for Philippe
Nyffenegger ;
CMB .80 ( added
muffling-section)
QD-Muffler rebuild
QD 35 & 25 rebuilds
QD-25 Hotpipe II :
Need For
Speed 2” band-pipe :
Another
eBay el Cheapo :
Rebuild
of a JohanD ,
twin-tailpipes
are needed because of the 40mm can:
Rebuild
of a ‘Salvatore’pipe from side to rear outlet ,
extended
can for volume and muffling:
And yet
another eBay-elCheapo , added Rossi-style muffler:
eBay-elCheapo , Deep-V header to fit inside a catamaran :
The
new JeroenTune/elSpeedy pipe in aluminium sold by Voodoo has thick welds.
If you
sand down those welds on the cones/muffler seam , pipe will crack.
Repaired
it by hard-soldering the joint and add a 50mm wide 1mm thick band.
(Just
to be sure) J
MHZ-Cooper
aluminium , second cone came loose , owner tried to repair himself ,
eventually
send it to me , quieter would be nice :
2 QD Deep-V’s …… ;
40mm ‘can’ on request , makes the CMB-baffleplate style
impossible ,
so Rossi-style came in.
In close cooperation with JohanD (Johan Draijer the
custom-pipe builder),
we developed a different kind of muffling ,
because we had the idea that it has to be possible to muffle
the pipe more
without loosing power or rev’s.
It’s been on the dyno and is approved.
CMB and Rossi-style mufflers are redirecting the soundwaves
three times ,
the JD_HS-style muffler is doing that 5 times.
This is what the JD_HS silencer looks like :
Attached to a QD-Hotpipe it looks like this :
And to a eBay-pipe like this ;
DeepV with extended outletpipe
eBay
silencer rebuild :
Looks like I’ve got
work to do J
Idea for the
SAMBA(ex-carpipe) outboard-pipe :
4” QD silencer , with
added water-injection.
Should muffle about 2dB extra.
Original QD spring
connector , replaced by custom clamp-style.
2 WTC-style catamaran
pipes , first one is my muffler-rebuild
on a eBay SS-pipe ,
second one is only ‘bended’ by me.
The “Chinese” are doing
my muffling-rebuild themselves now.
Both have 105° SS manifolds and water-cooled
flanges.
This bended
wtc-style is making tuninglengths of 280 to 380mm
or
11.0”/15.0” possible.
Hull is PSR Bandit-XL
5” muffler … with
230mm/9” extensiontube ,
to get it through the
stern on a QD-DeepV Hotpipe.
For the
outboard-muffler I made a different solution :
Here it’s ready , and undergoing
my ‘hot-curing’ treatment :
Updated March 23-2010 
©HendricX