Part #3
covered the Gear-Box casing plate and motor mount replacement, as well as
finally establishing a base-line of performance of the stock MY1020 motor.
This installment will deal with
a complete refurb of the MY1020, specifically a rewind, brush-plate upgrade and
a slot cut for active cooling.
Please Note: the procedure
listed below potentially can damage or destroy a working MY1020 if misunderstood
or not followed properly, please read the disclaimer...
Dis-assembly is straightforward,
2 (two) long bolts that run the length of the motor...
When you remove the brush-plate,
just put it aside, there are images further down that explain re-assembly...
With a chisel, knife and pliers,
break the glued fiberglass strips from between the slots and remove.
If you break one or two wires,
not a big deal, but try to keep as many coils intact as possible.
Always exercise care &
caution working around the copper commutator assembly.
Don't worry about the fiber
glass strips breaking...
They do not get reused.
The armature is made up of coils
that sits in slots that are separated by teeth (also called Hammer Heads, Anvils
or just "T's"... they must have a real name though???)
The un-winding of the motor is
easy, albeit boring and mundane... But make notes, specifically on the direction
that the wire came off, the number of turns per coil, the gauge of wire
originally installed and lastly the width of the coils relative to the
teeth/slots each spanned.
This variant of the many MY1020
class motors available from Unite Motor Company was sold in 2007 as a 1200Watt
48V motor, I don't have the factory rated current or RPM, but I've measured over
4,000RPM at no load...
This motor was wound with 2
parallel (layered) coils of 14 turns each of an AWG #23 wire, that equates to
approx 0.0226" in diameter. The sum of all coils were comprised of a single
strand of continuous wire that was UNWOUND in a Counter Clockwise (CCW)
direction.
The end of the last coil
terminates into the same tab that the start of the wire begins from.
Each coil spanned 4 slots/5
teeth...
The video at the bottom of this
pages illustrates the unwinding process...
The objective for the purposes
of the Suzuk-E project is to lower the no-load RPM of the motor and increase
it's torque. This typically would be accomplished by winding more turns of
lighter wire into the same physical space available.
In the case of this specific
MY1020 motor, I was able to mathematically determine that 16 turns of AWG # 19
wire in a single coil would bump the coil count up AND yield a greater
cross-sectional copper area for the current to flow through.
This is largely possible by
removing the mylar/plasitic slot liners as well as the fiberglass slot covers
and fiber board inserts. The armature slots are still lined with adhesive and a
thin layer of the fiber board residue.
The risk of an electrical short
in the coils is largely mitigated by saturating the coils with an epoxy resin to
create a solid mass. The issue of heat dissipation will be aided by the active
cooling component of the upgrade.
When completed, the motor will
be called upon to withstand peaks of 100Amps and sustained current draws of
75Amps.
Below, the armature is
completely cleaned...
Per the video, the END tab is
identified and marked, as are the 2 (two) teeth of the first coil to be
unwound,,, A & B will be the LAST coil wound, given they were the 1st coil
removed.
1 & 2 Designate the 1st coil
WOUND, in a Clock-Wise (CW) fashion (reversing the removal process).
The coils will be successively
wound relative to the direction of the green arrow.
(you may need to re-read the
above as it is confusing...)
The images below are of the
easiest part of the winding process, the first 3/4's of the armature.
The coils are building in stacks
as they advance one slot progressively to the right of the previous.
The small loop of wire that is
hooked into the commutator tab MUST be cleaned of insulation to ensure a solid
current carrying connection.
I use a small chain-saw
(circular) file... If you forget one or more connections the motor will have
"Dead-Spots" that will result in poor (lumpy) performance, or possibly
not work at all...
Much of this page is just
greater detail than the rewind info supplied in 2008 on this
page of a smaller MY1020 motor.
As the last 1/4 of the armature
is wound the overlapping of coils requires some gentle encouragement from a thin
piece of wood and a hammer.
The last coil will be the
hardest to wind neatly if the first coils were sloppy or loose.
More winding...
The
last coil will end on the same tab that the first coil started from...
Use an ohm meter to find any
poor or open connections. (Before the next step...)
To ensure a solid connection
between the commutator tabs and the physical wire, I opted to use a small
pointed chisel to peen the copper parts together.
I have every confidence that
this rewind will be successful, and have no concerns that the tabs can not be
lifted again due to this procedure.
The completed armature is
saturated with a 2 (two) part epoxy resin/catalyst mixture that has had a small
qty of Alkyd Oil-based enamel paint added. The paint adds a pigment for looks,
while offering a level of plasticity to the typically rigid epoxy.
Again this is to (hopefully)
fuse the coils into a solid mass and avoid any potential shorts due to vibration
or constant movement within the slots.
Note: The copper commutator is
carefully covered with tape to ensure that it does NOT get any resin on
it.
Brush-Plate Upgrade
The point of this upgrade is to
address the last 12" that the electricity must flow to get to the rewound
armature inside the motor. The MY1020 series of motors all use an identical
brush-plate that is wired with an AWG #12 stranded wire that is spot
welded/fused to the zinc covered plate body...
All three of the MY1020's that
I've rewound have shown corrosion where the zinc has been burnt off due to the
fusing process and exhibited noticeable heating of the original wiring when
driven hard.
The fiber-glass brush-plate is
mounted on 4 (four) posts that are part of the rear casting. This is a pressed
fit, I opted to drill-out the tops of the posts, there may be other ways to
accomplish the brush-plate removal...
Mark the Positive & Negative
poles of the plate before cutting the original wiring from the plate, and save
the woven fiber sleeves that covered the wire for a step further down the page.
With the brush-plate removed the
rear motor casing is drilled out with a series of holes to allow access to the
back of the brush-plate, and aid in venting excess heat.
Take care to leave enough metal
adjacent to the mounting posts for the brush-plate.
A simple wire harness is made-up
of a length of Stranded AWG#8 wire, with 2 (two) lengths of Solid core AWG#12
soldered together and a single length that will pass through the back of the
plate and be soldered securely into place.
The short lengths of doubled AWG#12
are covered with heat-shrink tubing and the woven sleeves that covered the
original wires that were cut away earlier.
The contact point for the new
wire harness is via a rivet hole (that is drilled out) from the back, on the
opposing side of the brush relative to the spring assembly.
If you decide to attach the new
wiring to the "Spring-Side" of the brush, the spring will get hung-up
on the connection and make for poor to no tension on the brush.
The brush-plate is securely
fastened back to the rear casting with 2 (two) self-tapping screws via
appropriately sized pilot holes drilled into the mounting posts.
The wiring is free of any
contact with the rear casting, and secured together with nylon ty-wraps.
Potentially the mass of the
physical wire harness could break or loosen the electrical connections to the
brush-plate due to vibration over time (this has yet to be determined)...
Alternatively, this
Link is to a different scheme employed on the 2008 rewind.
The difference being that the
wires exit via the factory hole & grommet NOT the back of the motor.
Re-assembly of the motor,
specifically the brush-plate, can be difficult when the brushes are under
tension via the springs... Similarly the orientation of the springs on to the
brush-plate influences the tension that is exerted on the brushes for a secure
connection between the brush surface and the copper commutator segments.
The image below is how I've
re-assembled the springs relative to the brushes, which allows you to pre-load
the springs AND retract the brushes for re-assembly quite easily.
With the armature inserted into
the Magnet ring/steel body, there should be a 1/4" to 1/2" gap that
would allow the springs to be un-loaded onto the back of the brushes... again,
see video.
Active Cooling
With the delivery path for more
power addressed and the physical armature rewound, the final modification is to accommodate
a measure of Active Cooling. This
Link is to a rear-mounted fan from the 2008 (Dirt-E Bike) rewind... But due
to the physical positioning of the motor, this proved to be problematic when
ever the bike would get dropped on it's left-side (breaking the fan and mount 3
times over the 2008 season).
The 4 (four) magnets create a
Magnetic Circuit via the steel sleeve that they are mounted in, I opted for the
most radical approach of cutting a single slot the length of the gap between a
single pair of magnets.
Alternatively a series of holes
could have been drilled between one or more pairs of magnets while retaining an
equal ratio of steel "Bridges" between the holes if more than one slot
is required.
Re-assembled and ready to test!
At this point ensure that the
"witness marks" that are stamped into the front & rear casings are
roughly aligned to the steel magnet ring, the motor will also need to have it's
timing reset.
Otherwise there is a 50/50
chance that the motor is out of phase by 90 degrees and will run Backwards
relative to the factory configuration.
I wish I could claim all the
credit for the innovations and final parameters for this project.
But much of the theory and maths
were discussed in detail on a public forum thread for this project, located at
the link below...
My sincere thanks to the Endless
Sphere Site and the numerous members that have taken an interest in this project
and added to the discussion to this point. Although there is an element of redundancy
between theworkshop.ca pages and the Forum Thread, together they hopefully cover
any details missed on either individual site.
With the motor re-mounted,
immediately a huge improvement in start-up torque is noticeable.
So much so, that a chain
tensioner definitely has to be added, as the chain is reliably thrown from the
bike if the throttle is cracked open aggressively (which is really the only way
to crack a throttle).
Similarly, the bolts that tap
into the front & rear casings of the motor are drilled out and re-tapped at
1/4" #20 thread for more secure fasteners.
The cobra-like response of the
motor has also started to break the 3/16th" bolts that hold the sprocket to
the clutch-plate...
I'm encouraged, but concerned at
this point...
The logical step was to also
upgrade the 5 bolts to 1/4" #20 hardware as well.
Due to the length of this
posting, I've opted to cover the Blower and Manifold assembly in Part #5...
Below is the summary video that
illustrates many of the less obvious procedures that just don't lend themselves
to verbal description or static images.
The
last coil will end on the same tab that the first coil started from...
