Welding the exhaust |
OK. it's time to
figure out how to get the exhaust out of the engine and back
to the afterburners. To make it happen, some 3.5 inch exhaust
bends were purchased off of Ebay, and Gary Richards from over
at www.garysjetjournal.com
was kind enough to send me some 3.5 inch diameter straight
pipe. Thanks Gary! Be sure to stop by his website and see
all the great things he is doing on his projects. While you
are there, give him a few "clicks for the cause"
too, to keep his R&D efforts going!
The idea here
is to make a duct system that will carry the hot gasses
over the rear tire to the afterburners. I have to be very
careful, since any bends in the pipe can cause a loss of
output power. I know that I have to use some bends to make
it all happen, but I will try to keep the transitions as
clean as possible to avoid the losses.
The turbine transition
The first hurdle
to overcome was the turbine outlet. The turbine outlet diameter
was exactly 3.5 inches. I didn't want to use pipe that was
bigger, since it could lead to more losses and low pressure
areas. Unfortunately, using 3.5 inch diameter pipe would
mean that the pipe could fit all the way right up to the
turbine blades themselves. Because the turbine housing flares
out from the blades to the much larger size where the exhaust
flange attaches with the clamp, I used the flare to my advantage.
I used a piece of 1 inch wide by 11 inch long 16 gauge steel
sheet to wrap around the first piece of pipe and make the
outer diameter slightly larger. This would allow it to sit
inside the flare of the turbine housing pretty well.
Finished transition
The finished
transition makes a good clean seal up against the turbine
housing, and cleaned up nicely after the welding process.
I beveled the edges that will sit inside the housing so
that the seal will be a bit better.
Turbine transition
The inside of
the transition was also beveled just a bit. The bevel will
let the gasses pass easily into the jet pipe without creating
unnecessary turbulence. The smoother I can keep the air
flow, the better at this point.
First bend
I had to make
the bends sharp enough to clear the rear tire, and shallow
enough to keep the air moving well. I finally decided on
using 45 degree bends to do this. I simply cut one of the
90 degree bends I purchased at a 45 degree angle and figured
on using one piece to bend the jet pipe up, and the other
piece to straighten it back out when the pipe could clear
the tire. One piece was then welded to a section of straight
pipe measured at 7 inches to bring the jet pipe height up
enough to clear the tire.
Exhaust flange to jet pipe
The other piece
of the exhaust bend was welded to the small turbine transition
and cleaned up. Since my exhaust flange adapter is made
to fit the large 5 inch diameter exhaust opening on the
turbo, I fabricated a steel ring with a 5 inch OD (outside
diameter) and a 3.5 inch ID (inside diameter) which the
jet pipe could pass through. It was then a simple matter
to weld the ring, jet pipe, and exhaust flange together
to make the assembly above. Now I have a firm way to secure
the jet pipe to the turbine housing, and will also use it
to make the integral rear engine mounts later on.
Entire jet pipe
With all of the
pieces finally coming together, this is what I got. A nicely
transitioned jet pipe capable of taking the hot gasses straight
from the turbine and up and over the rear tire to the afterburners.
Notice the small tabs on the exhaust flange. These stainless
tabs are the rear engine mounts! Once the jet pipe is clamped
to the turbo with the large v-band clamp it isn't going
anywhere, so these tabs should provide enough support to
keep the engine stable in the rear.
Final welding
A little final
welding and it was all done! I intentionally left the welds
raised at the joints instead of grinding them smooth. I
felt that the additional metal would help to keep things
together under the high pressures and heat that will be
going through the pipe. It won't really show anyway, since
the entire pipe will be wrapped with thermal heat barrier
wrap provided by our sponsors over at Design Engineering.
If you look closely at the large turbine flange to the right,
you can just make out a small hole where the thermocouple
for the exhaust gas temperature will mount.
Completed jet pipe
The completed
pipe bolts right up and gives plenty of clearance over the
rear tire. It should work great.
Engine mounts
The rear engine
mount tabs are clearly visible here, and bolt up to matching
tabs welded to the frame. With the new front engine mount
and the rear ones installed, there is no movement of the
engine at all. This will be a very good thing when running
at high speed!
The business end of things
The pipe sits
about 5 inches above the tire, and will give enough room
to make problems of heat getting to the tire negligible.
Sorry for the weird angle in the pic, it was about to start
raining on us and we pulled the bike from the stand before
taking the picture so it was leaning over on the original
side stand. I think the side stand may be a bit bent out!
It looks like it is leaning more than it should!
Well now we are
one step closer to running the engine in the frame for the
first time. I would have fabricated the afterburner cans
as well, but I made a mistake. While having them laser cut
for me (thanks again Chris!) I sent the 3D drawings with
a scale of 2 to 1 and didn't notify the laser cutting guys
about it. Because of this my afterburner parts arrived looking
great, but at half the size they should have been! I'm having
new parts cut now, so it shouldn't be too long before I
get them back and have shiny new dual afterburners on the
back. Thanks for taking the time to check out the site,
and remember to support us through donations and "clicks
for the cause"! See you next time!
Russ W. Moore
and
The Bad Brothers Racing Build Team
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