|
When riding ultra-conservatively, the Blackbird can achieve gas consumption
rates as high as 45 mpg. Thus, the stock 6.3 gallon fuel tank can afford a
max range on the order of 280 miles... not too shabby. However, in real
world riding conditions, figures of 33-35 mpg are more common for the
Blackbird. This means a range of 170-180 miles before the low fuel light
starts to flicker... not very far, really.
Since the primary job of my Blackbird is to carry me long, long distances
in a short amount of time, it was apparent that an auxiliary fuel cell was
needed to allow freedom from the constant, time-consuming fuel stops. I had
one on my ST1100 for many years, and missed the ability to refuel and hit the road for another 350 miles non-stop!
General Design Concepts:
- KEEP IT SIMPLE! The design approach was to create an aux fuel cell system that requires minimal rider intervention, indeed, minimal moving parts as well. A completely automatic, hands-free aux system would undoubtedly be cost prohibited and complex, so a simple, all-manual system is desired.
- NO ELECTRICAL COMPONENTS! I wanted to avoid using electrical fuel pumps
and solenoids to transfer the fuel from the aux to the main cell. I wanted
to design a system that was all-manual and 100% gravity-fed... no fuel pumps to fail, or
wire circuits to short out.
- MINIMIZE CG CHANGES! Many LD Riders resort to hanging a massive Jaz or
Fuel-Safe cell high off the rear luggage rack. Placement of a large 5-
gallon mass this high off the ground is quite bad, but even worse is
placing this weight *aft* of the rear axle! This combo wrecks havoc with
the bike's Center of Gravity (CG). Ideally, you want the weight as low as
practical, and endeavor to keep the weight "in between" the two axles. If the design opportunities won't allow the former, then one should definitely try to ensure it incorporates the latter.
The Approach:
Consider the image below. My design called for placing the aux cell on
a steel rack on the pillion seat (meeting criteria #3 above). The rack
solidly mounts to the frame and is held in place by the stock seat
latch. The bottom of the aux cell (depicted by the red line) will sit a
good 7-8 inches above the bottom of the stock tank (depicted by the green
line). The design called for a simple isolation valve (criteria #1) that is "thrown" by the rider while underway when the main tank fuel level is down to approximately 1/4 tank. This starts the gravity flow into the main cell (meeting criteria #2).
The main cell is fitted with a bulkhead fitting at the very bottom of the tank, immediately aft and to the right to the internal fuel pump. When the isolation valve is opened, the aux cell fuel drains into the main cell until the two tank fluid levels are "equal", at which time the fuel level in the two tanks decrease at the same rate as fuel is utilized by the engine.
The Implementation:
Apologies for the fairly large photos on the following pages, but they allow for viewing in greater detail.
The Fabricator:
Credit to Bill MAvan of BLM-Assessories Mounts
|
