Part #5
covered some fiber-glass work on the blower, auxiliary battery box and the
layout of the instrumentation panel.
A disastrous test ride high-lighted the need to revise the basic drive train, as the chain drive was just
too un-reliable.
To that end I started to
research some basics about belt drives and the physical parameters of the belts
themselves. The data table and accompanying illustration (below) are the best
that I could find that captures a wealth of information is such a compressed
format.
(Figures
above sourced from the Engineers Edge web-site...)
http://www.engineersedge.com/v_belt_sheave.htm
The Engineers Edge had numerous
pages that offered the maths and examples for load calculations as well as far
more information that I was able to absorb in just a few sittings...
The image to the right is the
tool-path for the EPS-Foam pattern that will be cut to make a set of custom cast
Drive & Gear-Box Pulley's for the Suzuk-E.
The dimensioning only has minor
allowances for the radius off-set of the tiny (0.032" endmill).
The splined tool-path is the
reference point for all other elements of the drawing. It was created from a
400DPI scan of the splined washer from the original Clutch-Basket.
The pulley outer dimensions are
sized for 6 1/2", the maximum available space before having issues with the
brake pedal or frame.
The image to the left is the
Motor Drive Pulley...
Outer Edge dimension is 2
1/2" in diameter.
Between the Drive pulley and the
Gear-Box pulley, the ratio is 6.5 : 2.5 and equates to a factor of 2.6
revolutions on the drive-side per gear-box input revolution.
Primary
Drive Ratio
Motor
Trans In
Ratio
2.50
6.50
2.60
Target RPM
Calc
Measured
Motor RPM
500
1000
1500
2000
2500
3000
3500
4000
4200
"@4200
1st Gear - Km/h
2.88
5.77
8.65
11.54
14.42
17.30
20.19
23.07
24.23
17KM/h
2nd Gear - Km/h
3.55
7.09
10.64
14.19
17.73
21.28
24.82
28.37
29.79
21KM/h
3rd Gear - Km/h
4.27
8.55
12.82
17.10
21.37
25.65
29.92
34.20
35.91
26KM/h
4th Gear - Km/h
5.04
10.08
15.12
20.16
25.20
30.24
35.28
40.32
42.33
31KM/h
5th Gear - Km/h
5.70
11.40
17.10
22.80
28.50
34.20
39.90
45.60
47.88
35KM/h
6th Gear - Km/h
6.38
12.77
19.15
25.53
31.92
38.30
44.68
51.07
53.62
38KM/h
The chart above is the revised
spread-sheet data with the hope that the modified MY1020 will be able to operate
reliably (and efficiently) at the 2,500RPM mark.
The CNC-Mill has been dormant
for almost a month and half, but has seen a flurry of projects fire through in
the last 3 weeks, and so, was running in top trim for the pulley patterns shown
above...
For more info on the home-brew
mill shown above see links below...
The gear-box pulley is assembled
with hot-glue and the "V-Groove" is cut into the blanks with a wood
rasp and flat-file.
The blank is carefully centered
on a mandrel of sorts and mounted into the drill-press and run at the highest
speed to cut the groove per the angles and dimensions listed above for an
"A-Type" belt.
The splined center has a
snug-fit after some laborious dressing of the fragile teeth that are cut into
the foam.
The EPS-foam patterns are packed
into flasks with foundry sand and a single pouring spout (or sprue).
This is a sacrificial molding procedure,
meaning that the foam patterns are consumed in the casting process.
So if things go wrong, it all
gets repeated, starting with machining new patterns.
The 2 (two) images below are the
height of a 36hr work marathon to hit a day that posed no threat of snow, while
was above minus 10C to make working outside semi-bearable. The alloy being used
is 100% recycled Hard Disk chassis/framing.
Unfortunately in the course of 2
system crashes, not surprisingly, I've lost some of my obscure notes on alloy
compositions, regardless... Hard Disks are an Aluminum based alloy with various
percentages of Zinc and Silicon to aid in high detail reproduction when die
casting, so are excellent for this application.
Even after allowing 20 minutes
for the metal to solidify, the casting is stinking hot as the flasks are broken
open and the parts shaken out.
The splined opening on the
pulley turned out accurately (though slightly under-sized presumably due to the
shrinkage of the alloy), there was a degree of file-work to achieve a secure
fit, but there is a solid ridge of metal for each groove mating on the input
shaft.
The pulley is centered, but has
a slight lateral wobble that will be machined out at a later date, as the
weather is scheduled to turn for the worse in a few days.
The Drive-Pulley was in
considerably rougher shape. The center mark seemingly drifted during the pouring
of the alloy, as there was no fixed core embedded to establish a solid location.
The lettering on the face also
was flawed on one side, so I opted to just machine the face down.
The grooves had to be re-cut to
establish a concentric path for the belt to be driven along. This worked out ok,
not spectacular, just ok...
If I have to cast a replacement pulley with a core,
I can also vary it's diameter as I picked-up an assortment of belt sizes for just
that reason.
The image to the right (above)
is a hard rubber roller-skate wheel that is being machined down as an idler
wheel to keep the belt under tension.
Those that are familiar with the
MY1020 motor will note that the output shaft has been heavily modified.
The under-sized
"D-Slot" shaft and ridiculous "Left Hand thread" have been
obliterated as layer upon layer of welding beads are built-up and ground down.
A tray of ice is kept handy and
applied immediately after each weld is laid down to keep the heat from
transferring inside the motor via the shaft.
To machine the shaft concentrically,
the motor is run at high speed (just under 4,000 RPM), while the grinder is
cutting in the opposite direction of rotation.
The spindle that the Idler-Wheel
runs on was welded to the original chain drive tensioner.
Though I'm afraid that the heat
of the welding has taken any temper out of the spring as it is noticeably weaker
than it was earlier.
The window of opportunity for a
road test is closing quickly at this point, as the day has turned overcast, and
15 to 20cm of snow is scheduled for delivery in the next 12 hours...
Faced with the choice of
investing several more hours into the motor-shaft, truing the drive pulley and
fashioning a stronger belt tensioner, I said "Fuck-It!" as the
long-range forecast shows no breaks in the weather for over a week.
This is the state of the bike
after coming in from the road-run, shown in the video below...
Though in the video all you see
are the down-hill runs... In all fairness the Suzuk-E did make it up all the
hills (including our drive way which is a testament to any motive force
vehicle).
But the belt was slipping and even squealing at times to the point I
was just glad to be back at the shop.
The drive pulley was so hot that
I couldn't touch it and there was a faint odour of heated rubber in the shop.
So ends Part #6, still no end in
sight, though a pile of fun had along the way...
The blower assembly is next to
useless as the motor was being run in sub-zero Celsius temps and returned to the
shop reading in the high +30's C as measured on the outer casing.
The next installment will likely
cover the finishing of the instrument panel, building some sort of regulator to
feed the LED head-light, replacing the blower assembly and finishing the
belt-drive properly.
This shot is of our yard the
morning after the test-run.
I feel I made the right call in
just "going for it".
I don't think that I'd have been able to
assess the drive drain and cooling system in the shop just with prolonged and
repeated No-Load Testing...
... and a little video to
clarify any vague spots above.
