Hello Mike,
I'll second what Cal is saying below. To get the nut off, you have to
place a wrench on the nut and "impact" it until the nut loosens. I
would **not** use a compressed air impactor tool. I use my fist. Be
careful because everything is free wheeling. If you leave your knuckles
in the path of the blade, your knuckles are going to get whacked. There
is no other place to place another wrench unless you weld a nut to the
top of the motor shaft.
Like Cal, I keep a set of several "small plastic blade insulators" on
hand which is how they are described in the User's Manual. The word
"insulator" may seem like a misnomer but it is to "insulate" the shock
of hitting a rock from damaging the armature.
I converted a corded B&D to cordless. It uses 9 - 5 amphr 12 volt LA
AGMs to power the mower. It is enough to do a 7K square foot lawn.
What used to take me 1.5 hours to do when corded, now takes about 45
minutes.
I use a 1.3 amphr AGM for the tripping a small contactor. This battery
goes down faster than the pack. I would use about a 2 amphr battery for
each hour the contactors are tripped. That should give you plenty of
cushion.
I wrote a two part article for the Electric Auto Association's Current
Events magazine. I have the submittals in PDF format. The B&D motors
are DC universal motors that operate at 120 volts. The corded version
has a full rectifier bridge on a little heat sink. It was mainly a
rewiring job to bypass the rectifier.
I think the AGMs are the wrong type of battery for this project.
Normally, when not cutting the lawn, the motor consumes about 4 amps.
When cutting thick grass, the motor consumes about 8 amps. It can spike
to 10 amps in real thick grass or when the mower clogs up in thick grass.
I have been contemplating upgrading this mower to Lithium. A set of 40
- 3.2 volt 10 amphr would be about right for an hour's worth of cutting
and still have some reserve. I saw an ad for Shorai 12Volt 12 Amphr
batteries for $117 each and they weigh about 1.7 pounds. My 5.0 amphr
batteries weigh 3.5 pounds each for an added weight (starter + pack
support + contactor) of 35 pounds onto a mower that weighs 47 pounds for
a total of around 82 pounds. This is about the weight of an ICE push
mower. Twelve Shorai batteries would be around 20 pounds. The mower
would be lighter and so would your wallet of $1400 plus shipping.
I have thought about purchasing 4 - 100 amphr CALB batteries and then
use a converter to step up the voltage to 120 volts. At an efficiency
of 85%, the amphrs to the motor would be about 8.5. I am not sure if a
converter could handle that much amperage. I was going to do some more
homework before asking the experts here. Four CALB batteries would be
about 600 dollars and a converter would run in the lower several
hundreds. The savings would be substantial but I am not sure if the
electronics would handle the load.
The other thought would be to run the 4 CALBs into an inverter and leave
the rectifier bridge intact. The inefficiency of the inverter plus the
inefficiency of the rectifier bridge would likely sap the pack of a lot
of useful energy. I think this would be a nonstarter.
I know of someone using a self contained electric mower. You might want
to shoot him an email at theadm *A*T* AOL. If you are in the RTP area,
we are both "local".
Everyone else I see running an electric mower are running with a cord.
If you want me to, I will ask my neighbors their brand and opinions.
On 4/28/2014 1:27 PM, Cal Frye wrote:
I'm on my second Black and Decker push mower, corded type. I have a
small lawn, so avoiding running over the cord is not a major problem. I
won't advise on motor or batteries, but I can say B&D has a plastic shim
in the stack of washers holding the blade to the motor shaft. Said shim
has raised edges which grip either side of the blade, and an opposing
pair of edges which grip in turn a keyed, square washer above the blade.
This square washer is driven by the motor, and the blade is driven by
the plastic shim. Hit too hard an obstacle, and the plastic edges shear
off and the blade rotates freely.
This is effective, but is also a wear point, and I've learned to buy the
shims by the half-dozen. My eyes don't always find the rocks in the yard
before the blade does :-(
Best regards,
-- Cal Frye, www.calfrye.com
/Be an Internet Sceptic/ Stop. Think. Connect.
www.stopthinkconnect.org - Be at least as safe on the
Internet as you are crossing the street!
"I sincerely believe that banking establishments are more dangerous than
standing armies." -- Thomas Jefferson, letter to John Taylor.
Michael Ross <mailto:[email protected]>
April 28, 2014 12:58 PM
I have an old simple ICE push mower, that might be worth converting.
...
What about the shock of the blade hitting something nearly immobile? That
is a lot of shock that small engines are able to handle - special
consideration in the regard with electric motors?
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