(ET) Re: Polychain timing belts, V belts, and PolyVee belts

["The Nauglers" <snaugler earthlink net>]

The Gates PolyChain is a special version of a timing belt:
http://www.gates.com/brochure.cfm?brochure=919&location_id=742

The PolyChain is a high power capable belt due to its higher strength as
compared to standard timing belts, and was designed to compete with chain.
Timing belts can range from 92-95% efficiency.

Goodyear and others make a PolyVee belt, also 92-95% efficient:
http://www.engineheat.co.za/comp-polyvee-belts.php

You use a timing belt when driven items must be sychronized.  You use a V
belt, including the PolyVee belt, whendriven items do not need to be
sychronized.  Timing belts are almost always noisier than V belts 
delivering
the same power.

The V belts, including the PolyVee belts, have the additional advantage 
that
if it sees too high of a load it can slip.  Sure the belt does suffer high
wear when it happens, but usually the driver or the driven is spared 
damage.

A timing belt can will deliver a lot of power when overloaded.  Frequently
the driver or driven is damaged along with the timing belt.

Steve Naugler
snaugler earthlink net

----- Original Message ----- 
From: "Dave & Debbie Barden" <daveb seanet com>
To: "The Nauglers" <snaugler earthlink net>;
<elec-trak cosmos phy tufts edu>
Sent: Thursday, February 19, 2004 2:09 PM
Subject: Re: (ET) Re: new electrics


> and what about Polychain made by Gates.  Goodyear has a similar toothed
belt
> also but it's teeth are aligned in two rows forming  chevrons that has 
> the
> added advantage of being able to stay on the pulley without shoulders.
that's
> a pretty crude description but I wonder how these belts compare 
> efficiency
wise
> and what the downside is to them?
>
> dave
> seattle
>
> > With all this talk about new ETs and better or cheaper ways to make 
> > them
> > please remember that due to the limited energy storage on board our
tractors
> > efficiency must be paramount.
> >
> > V belt drives tend to be only 90-95% efficient when everything is in
good
> > condition and clean.
> >
> > Friction drives are 80-90% efficient.
> >
> > Chains, again in good condition, are 98 % efficient, but high
maintenance to
> > keep them in good shape in a tractor application.  Notice that they are
not
> > used except in high torque attachments like the snowblower.  A worn,
dry,
> > and/or rusty chain can have efficiencies as low as 60-70%.  The wasted
> > energy turns to heat and destruction of what is left of the chain and
> > sprockets.
> >
> > Direct drive, like the mower decks, are 100% efficient.
> >
> > GE used VX series V belts for the traction motor because the VX series 
> > V
> > belts are more efficient than the old A/B/C/D series V belts.  If the
new
> > Poly V belts, which are like the serpentine belts on modern cars, had
been
> > available when the Elec Traks were designed they would have been used
> > preferentially over VX belts.
> >
> > What GE did was make a whole series of design choices to keep 
> > efficiency
> > high.  Where they lost efficiency was in the motor controls, and that
was
> > mainly a limitation of affordable DC drive technology of that time.  If
you
> > were, in your new tractor, to use a friction drive for the traction
motor
> > and belts in the mower deck, and then allowed for lack of maintenance,
you'd
> > find extra losses of 10-25% after 1 or 2 years of service.  I mean
10-25%
> > higher losses than in a tractor with direct drive to the blades, and a
high
> > efficiency belt somewhere in the traction drive.
> >
> > With respect to protecting the mower motor with a circuit breaker:  
> > This
> > will not work well with a permanent magnet motor.  In permanent magnet
> > motors there is some critical armature current above which you will
> > demagnetize the magnets.  The friction washers, while crude, act as a
torque
> > limiting clutch.  By limiting torque, you effectively cap the armature
> > current.  If you use a circuit breaker alone the current can, and most
> > likely will, pass well above that critical current before the breaker
trips.
> >
> > Steve Naugler
> > snaugler earthlink net
> >
> >
> >
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> >
>
>
>
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