On Fri, 17 Jul 2009 10:53:10 -0400, "Eric"
wrote:

"sid" wrote in message
...
On Jul 17, 7:25 am, Hipupchuck wrote:
sid wrote:
Our Garage Door opener Jerks when it opens and closes. Its like the
opener does not make an effort to open easily or slowly, its like it
just dropped the clutch. does not matter if its up and closing or
closed and starting to open !

Are there any openers on the market that stated the movement slowly ?

Thanks

Sounds like the spring that ties the two ends of the chain together is
weak or loose. There is no clutch. Unless your track is binding the door
it's entire length. A heave drag will make it bounce in both directions.

Its a LiftMaster Chamberlin Professional, Formula II
It uses a belt with teeth.

The system has been up 5 years and has been jerking since the day it
was intalled.
I questioned the builder on it, but he stated that there was nothing
that he could do.

Its not a question of spring tension or lubrication, its just a fact
that the panels of the door have some natural play between them and
when the opener starts to move, its with an abrupt manner. The whole
door (all the panels) bounce back and forth for about a 2 count,
before it settles down and travels the rest of the distance.

One would think that a designer would design the opener to start out
slowly and then get up to speed. Not just close a contact and engage
the motor like dropping a clutch (I know there is no clutch, just
trying to draw a picture).

Any ideas, Thanks

Not to be too much of a wisea$$, but my idea is that the builder is right... there's not much that
can be done!

That opener may jerk a little more than others because the belt drive probably has a little more
stretch (= springiness) than the chains or worm drives used in other openers. So one solution would
be to replace the opener with one with a different type of drive, although every opener I've seen
does what you're talking about to some degree.

From a design perspective, having the motor start slowly would be great but would considerably
increase the cost of the unit. Right now it's just got a dirt-cheap motor and a relay to turn the
motor on and off. A variable-speed motor and control circuit would be much more costly.



The Genie "Excelerator" model has a variable speed motor and only
costs $10 or $20 more then similar regular motor models. The Opening
speed is twice as fast as the closing speed. And it self adjusts the
first time it runs (or after there's a power outage) by going very
slow and setting it's own stops at each end. It's the typical genie
screw drive, which I've always gotten outstanding service from. It
also seems to start and stop more gently in general then "regular"
openers.