??? ??? second thing to do is open the gear box & check for
oil . these are things to do with any 4x6 ya buy
??? ??? animal
On 1/1/2020 5:39 PM, Jerry Durand
wrote:
toggle quoted message
Show quoted text
One thing I'd be sure of, when you receive it
verify that the arm goes straight up and down.? Occasionaly
they'll ship one where the hinge holes are off.? This is VERY
hard to fix by yourself, best to swap for another one.? But,
most of these work fine.
I had to swap mine simply because the FedEx
delivery guy was by himself and they didn't issue him a hand
truck/dolly.? So, he simply shoved the box out the back of the
truck to fall onto the street.? He then dragged it to my door
where I sent it back.? I met him at the truck for the next trip
and we carried it to the house.
---
Jerry Durand
Durand Interstellar, Inc.
On Jan 1, 2020, at 17:13, mike allen <
animal@...> wrote:
??? ??? the saws are pretty ok , but like anything from HF
"if it plugs in yer gonna have problems at sometime " motors
are pretty easy to come by
??? ??? animal
On 1/1/2020 4:49 PM, Chris
Hibbert wrote:
I
have yet to purchase a 4x6 bandsaw (harbor freight) and all
this talk about overheating and burning up motors is making
me question if I should buy one.
?
¡°This
is getting overly complex??? In most cases a NEMA
motor starter with properly selected heaters should
protect the motor against overloads and blade jams,
no??¡°
?
To a degree, yes. Protection is
however a dance between how often you have to reset
it versus how much thermal damage you are willing to
accept.
Some overloading is normal and
expected for a motor. Normal rule of thumb for
electrical equipment, is that each 10 deg C rise you
have, shaves 5-10 years off of the expected lifetime
of your insulation system. ?
[That is rise over rated temp,
and extended running temp, not just occasional
excursions]
?
The intent of the protection is
really to prevent fire and shock, not preserve the
lifetime of the equipment.
In industrial use it might be
perfectly acceptable to get a 5 year life, in
exchange for not having to reset the protection 5
times a day.
?
?
OUR
EMAIL ADDRESSES HAVE CHANGED
We
were xxxxx@vertivCO.com
and we are now xxxxx@...
?
?
R
James (Jim) Klessig P.E.
| Senior Power Systems Engineer |
Electrical
Reliability Services, VERTIV
jim.klessig@..., jim_klessig@...
1876
Gwin Rd, Mckinleyville | CA | 95519 | USA
|
Cell (707) 497-9611 | eFax 614-410-0653
?
?
This is getting overly complex???
In most cases a NEMA motor starter with properly
selected heaters should protect the motor against
overloads and blade jams, no?? Or an IEC-type
starter for that matter.
Well, it's New Years? Eve in this part of? the
world.? So Happy.
am
At 03:57 PM 12/31/2019 -0800, you wrote:
Sorry guys been out of the loop
a few days ((long hot summer days here in NZ, out
on the 'bike, swimming etc while you're all
shivering!)
Thanks for the sensor link Jerry.
I didn't think about North America being on 60Hz
while rest of us are on 50Hz, Robert.? Normal cap
start induction motors here are rated for full
load speed of 1425rpm while you're on ~1725rpm.?
My motor (TEFC/cap start/cap run) says full load @
~1360rpm on the maker plate.? Its happy down to
1300rpm but stalls below 1250rpm (as tested with a
tacho).? I suppose 60Hz motors will be ok to
something like 1600rpm and stall around 1550rpm.
The reason I think its important to be able to
monitor and protect the motor is that to get any
reasonable cut time performance out of a 4x6 you
need about 20lb of weight on the teeth.? This
translates to bow weight (weight in just lifting
the sawframe off its stop) of 8 to 9lb on mild
steel, but over 9lb, depending on your blade
speed, you can stall the motor.? The tests I've
done with increasing bow weight and measuring rpm
and cut time all look like the attached pdf -
increasing bow weight reduces the cut time until
the motor stalls.
In practice Jim, it seems, for a 4x6 with only
1/2HP, they'll all run below their rated rpm at
what would be considered a normal cutting speed
Will be worse for those with only 1/3HP.? Of
course the motor makes more than its rated HP if
you load them up so they run below their rated
rpm.? This only gets to be a problem if you are
running continuously and then they'll over-heat,
but with stop/start running that most of us do
(with possible exception of Jerry!) thats not a
problem. See the graph on pg 2 of the attachment
for how torque varies with speed on a CS induction
motor.
You can run higher bow weight without stalling, if
the blade speed is reduced, but bow weight in
excess of 8-9lb damages the blade (causes gullet
cracking and swages over the back of the blade) -
jv
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