Electrical Engineering - Retarding Torque on a motor is what?

Author

Retarding Torque on a motor is what?

clannorm@yahoo.com

2007-01-30, 9:25 pm

I work in a welding shop and do occasional maintenance. We have a
large (Bertsche 10foot) shear. The motor that moves the back guage has
on the info plate that there is I think 6 lbs of retrading torque.
THere is also from back of motor an adjustable clamp which bottoms out
on welded on stop. This adjustment must be related to this retarding
torque but I have no idea what is going in. I posted this also to the
maching newsgroup where there is usually someone who will know just
about anything to do with manufacturing with no luck. Any ideas?
Ken

Long Ranger

2007-01-31, 9:25 am

<clannorm@yahoo.com> wrote in message
news:1170213677.988899.250000@k78g2000cwa.googlegroups.com...
> I work in a welding shop and do occasional maintenance. We have a
> large (Bertsche 10foot) shear. The motor that moves the back guage has
> on the info plate that there is I think 6 lbs of retrading torque.
> THere is also from back of motor an adjustable clamp which bottoms out
> on welded on stop. This adjustment must be related to this retarding
> torque but I have no idea what is going in. I posted this also to the
> maching newsgroup where there is usually someone who will know just
> about anything to do with manufacturing with no luck. Any ideas?
> Ken
>
I can't imagine why torque would be retarded while the motor operates. Maybe
that is a braking device to keep the machine indexed at the end of a cycle,
so it doesn't coast through the next half, or so of it's motion?

2007-01-31, 5:25 pm

In article <MX1wh.16670$pQ3.4164@newsread4.news.pas.earthlink.net>,
"Long Ranger" <worpylorp@mindspring.com> wrote:

> <clannorm@yahoo.com> wrote in message
> news:1170213677.988899.250000@k78g2000cwa.googlegroups.com...
> I can't imagine why torque would be retarded while the motor operates. Maybe
> that is a braking device to keep the machine indexed at the end of a cycle,
> so it doesn't coast through the next half, or so of it's motion?
>
>

This was found here: http://www.ftimeters.com/pages/uvc.html

> The viscous drag exerted by the metered fluid acts on all of the moving
> surfaces of a turbine flowmeter. This drag acts within the bearing and in the
> space between the rotor blade tips and the housing. The viscous drag exerted
> on the surfaces of the rotor blades produces both a downstream thrust and a
> retarding torque on the rotor.
>
> Because of the viscous retarding forces on the rotor, it does not spin as
> fast as it would in an inviscid fluid. The rotor actually slips in the stream
> of flowing fluid, so that the surface of the blades slightly deflect the
> fluid. The deflection of the fluid by the rotor blades causes a change in
> momentum in the fluid and a resulting force on the rotor blades. This force
> on the blades causes a driving torque which overcomes the retarding torque
> caused by viscous drag forces. The rotor then spins at a rate at which the
> slip causes the driving torques to exactly cancel the retarding torques. The
> amount of slip of the rotor will depend upon both the kinematic viscosity and
> the velocity of the fluid, just as do the viscous drag forces discussed in
> the previous section. Therefore, the performance of the meter is a function
> of the Reynolds Number associated with the flow.

In other words, the rotor spins backwards and a torque has to be applied
to make it stop. This is the retarding torque. I suppose in your case,
when the shear opens and goes backward, a torque must be applied to stop
it before it hits the stop.

Al

clannorm@yahoo.com

2007-01-31, 9:25 pm

On Jan 31, 3:31 pm, Al <no.s...@wanted.com> wrote:
> In article <MX1wh.16670$pQ3.4...@newsread4.news.pas.earthlink.net>,
> "Long Ranger" <worpyl...@mindspring.com> wrote:
>
>
>
>
>
>
>
> This was found here:http://www.ftimeters.com/pages/uvc.html
>
>
>
>
>
>
>
> In other words, the rotor spins backwards and a torque has to be applied
> to make it stop. This is the retarding torque. I suppose in your case,
> when the shear opens and goes backward, a torque must be applied to stop
> it before it hits the stop.
>
> Al- Hide quoted text -
>
> - Show quoted text -- Hide quoted text -
>
> - Show quoted text -
Let me explain further. The motor moves the back guage in and out so
that whatever is being cut will be cut to a specificl length. From
the shear blade to the back guage which as i said is moved by the
motor. The motor is off or at least I've stopped pushing to button to
position it when the shear comes down and shears the material. Most of
the force id directed down cutting the material. I assume there is
some pushing against the back guage and maybe this retarding torque is
so the guage stays stationary.
Ken

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