Ok... When we got new overhead doors in the garage a few years ago
they put in all new hardware. Rails, springs, everything. I was busy
at the time, and had more money than time. Not so now, so please no
Nigerian banking scams.

Anyway, there are two doors. One is an 8 x 9 and the other is 8 x
16. The smaller one has a single coil spring on a standard overhead
door axle. The larger one has two springs. What is odd is that the
are not the same size. One is about the same size as the one on the
smaller door. The other is a good 14-18 inches longer.

Now if everything was working fine I wouldn't have even noticed, but
the smaller of the two springs on the larger door broke. Makes sense
since it would have less length to absorb the twist. My question I
guess, is there any "legitimate" reason why they would two different
size springs on a the same door axle?

I am not willing to just say, "Well they are the professional door
company. They must know what they are doing." They do not. The
rails, opener mount, etc were all out of square, and even the distance
between the rails from the header to the motor was off. I called them
back 3 times before I finally gave up and just fixed it all myself.

The unbroken spring on the larger door is much larger. I was
wondering if it might not be adequate to handle the door by itself. I
installed all the commercial doors on my shop (much heavier doors) and
I still have a set of door spring tommy bars on the shelf.

On Wed, 11 Jul 2012 16:00:07 -0700 (PDT), Bob La Londe
wrote:

Ok... When we got new overhead doors in the garage a few years ago
they put in all new hardware. Rails, springs, everything. I was busy
at the time, and had more money than time. Not so now, so please no
Nigerian banking scams.

Anyway, there are two doors. One is an 8 x 9 and the other is 8 x
16. The smaller one has a single coil spring on a standard overhead
door axle. The larger one has two springs. What is odd is that the
are not the same size. One is about the same size as the one on the
smaller door. The other is a good 14-18 inches longer.

Now if everything was working fine I wouldn't have even noticed, but
the smaller of the two springs on the larger door broke. Makes sense
since it would have less length to absorb the twist. My question I
guess, is there any "legitimate" reason why they would two different
size springs on a the same door axle?

I am not willing to just say, "Well they are the professional door
company. They must know what they are doing." They do not. The
rails, opener mount, etc were all out of square, and even the distance
between the rails from the header to the motor was off. I called them
back 3 times before I finally gave up and just fixed it all myself.

The unbroken spring on the larger door is much larger. I was
wondering if it might not be adequate to handle the door by itself. I
installed all the commercial doors on my shop (much heavier doors) and
I still have a set of door spring tommy bars on the shelf.

From the most excellent http://www.truetex.com/garage.htm

"You must use springs that are matched to the weight of the door. You
cannot compensate for the wrong size spring by adjusting the number of
winding turns."

"Unmatched or mismatched spring pair: You may find that you have a
pair of springs that are different sizes. This mismatch may be a
normal application, since the total torque on the torsion shaft is
simply the sum of the torque contribution of each spring (indeed, very
large doors can be lifted with 4 or more springs along the torsion
shaft). The sum of the torque rates determine the lift; and dividing
the torque among multiple springs does not change this. Some repair
shops even apply mismatched pairs deliberately, since a few stock
sizes of springs can be combined to fit a wider range of door weights
than only matched pairs. For example, a technician may carry springs
in increments of 20 lbs of lift, and when using pairs this allows a 20
lb increment in possible choices instead of 40 lb increments. Or, one
spring from a pair may have broken and been replaced with a spring of
equal torque rate but different size than the original.

Having a mismatched pair makes it difficult to specify the correct
matched-pair replacements. To obtain replacement springs for a
mismatched pair, you can either specify the same odd pair, try to
calculate the equivalent matched pair sizes, or (this is the best
method measure an accurate door weight and calculate the right
spring size(s) "from scratch". The spring seller should be able to do
the calculations from your accurate measurements of weight, height,
and drum size; or you can attempt the calculations yourself using my
engineering formulas below. "

"whoyakidding" wrote in message
...
On Wed, 11 Jul 2012 16:00:07 -0700 (PDT), Bob La Londe

Having a mismatched pair makes it difficult to specify the correct
matched-pair replacements. To obtain replacement springs for a
mismatched pair, you can either specify the same odd pair, try to
calculate the equivalent matched pair sizes, or (this is the best
method measure an accurate door weight and calculate the right
spring size(s) "from scratch". The spring seller should be able to do
the calculations from your accurate measurements of weight, height,
and drum size; or you can attempt the calculations yourself using my
engineering formulas below. "

Thanks. I have installed a few OH doors over the years, but they all either
had a single spring or a matched pair. I can see the thinking behind having
mismatched springs for over all load capability and so they can carry fewer
different springs in their service truck, but it still seems like the stress
on the shorter spring would be greater over time.

I've done low head room rear frame springs. I've down high head room jack
shaft setups with a "normal" top axle (usually solid for this application),
and I have done regular hollow shaft normal height top spring installations.
I've done some really heavy insulated commercial doors too. All had either
single spring for light hollow doors or two matched springs for heavier
doors.

On 7/11/2012 10:03 PM, Bob La Londe wrote:


Thanks. I have installed a few OH doors over the years, but they all
either had a single spring or a matched pair. I can see the thinking
behind having mismatched springs for over all load capability and so
they can carry fewer different springs in their service truck, but it
still seems like the stress on the shorter spring would be greater over
time.

I've done low head room rear frame springs. I've down high head room
jack shaft setups with a "normal" top axle (usually solid for this
application), and I have done regular hollow shaft normal height top
spring installations. I've done some really heavy insulated commercial
doors too. All had either single spring for light hollow doors or two
matched springs for heavier doors.







Could it be that they mixed up the springs? the single heavier spring
for the single door, and the matched pair for the big door?

On Wed, 11 Jul 2012 16:00:07 -0700 (PDT), Bob La Londe
wrote:

Ok... When we got new overhead doors in the garage a few years ago
they put in all new hardware. Rails, springs, everything. I was busy
at the time, and had more money than time. Not so now, so please no
Nigerian banking scams.

Anyway, there are two doors. One is an 8 x 9 and the other is 8 x
16. The smaller one has a single coil spring on a standard overhead
door axle. The larger one has two springs. What is odd is that the
are not the same size. One is about the same size as the one on the
smaller door. The other is a good 14-18 inches longer.

Now if everything was working fine I wouldn't have even noticed, but
the smaller of the two springs on the larger door broke. Makes sense
since it would have less length to absorb the twist. My question I
guess, is there any "legitimate" reason why they would two different
size springs on a the same door axle?

I am not willing to just say, "Well they are the professional door
company. They must know what they are doing." They do not. The
rails, opener mount, etc were all out of square, and even the distance
between the rails from the header to the motor was off. I called them
back 3 times before I finally gave up and just fixed it all myself.

The unbroken spring on the larger door is much larger. I was
wondering if it might not be adequate to handle the door by itself. I
installed all the commercial doors on my shop (much heavier doors) and
I still have a set of door spring tommy bars on the shelf.

Do you have Menards in you area? The have a real nice spring selection
table base on door weight. Then you order what you need. They are
color coded, does your good spring have a color code? And my large
door has two different size springs.

On 7/11/2012 4:00 PM, Bob La Londe wrote:
Ok... When we got new overhead doors in the garage a few years ago
they put in all new hardware. Rails, springs, everything. I was busy
at the time, and had more money than time. Not so now, so please no
Nigerian banking scams.

Anyway, there are two doors. One is an 8 x 9 and the other is 8 x
16. The smaller one has a single coil spring on a standard overhead
door axle. The larger one has two springs. What is odd is that the
are not the same size. One is about the same size as the one on the
smaller door. The other is a good 14-18 inches longer.

Now if everything was working fine I wouldn't have even noticed, but
the smaller of the two springs on the larger door broke. Makes sense
since it would have less length to absorb the twist. My question I
guess, is there any "legitimate" reason why they would two different
size springs on a the same door axle?

I am not willing to just say, "Well they are the professional door
company. They must know what they are doing." They do not. The
rails, opener mount, etc were all out of square, and even the distance
between the rails from the header to the motor was off. I called them
back 3 times before I finally gave up and just fixed it all myself.

The unbroken spring on the larger door is much larger. I was
wondering if it might not be adequate to handle the door by itself. I
installed all the commercial doors on my shop (much heavier doors) and
I still have a set of door spring tommy bars on the shelf.

I just went thru this.
Conventional wisdom is that springs have finite life and you should
replace both springs.
I'd recommend using the exact same ones you have now.
In my case, they don't make 'em like they did 40 years ago. But
there are charts that reliably translate from what you have to what
you can get. I couldn't find anybody local who'd sell me springs.
And the time to order them was longer than I could wait to get my
car
outa the garage. I couldn't lift the door.
I paid the $100 over the mail order spring price to have it done
the same day.
After watching it happen, I think I coulda done it just fine.
But a slip of the tool could cause some serious damage. I was afraid
the guy was gonna have a heart attack when he was tightening the springs.

"mike" wrote in message
...
On 7/11/2012 4:00 PM, Bob La Londe wrote:
Ok... When we got new overhead doors in the garage a few years ago
they put in all new hardware. Rails, springs, everything. I was busy
at the time, and had more money than time. Not so now, so please no
Nigerian banking scams.

Anyway, there are two doors. One is an 8 x 9 and the other is 8 x
16. The smaller one has a single coil spring on a standard overhead
door axle. The larger one has two springs. What is odd is that the
are not the same size. One is about the same size as the one on the
smaller door. The other is a good 14-18 inches longer.

Now if everything was working fine I wouldn't have even noticed, but
the smaller of the two springs on the larger door broke. Makes sense
since it would have less length to absorb the twist. My question I
guess, is there any "legitimate" reason why they would two different
size springs on a the same door axle?

I am not willing to just say, "Well they are the professional door
company. They must know what they are doing." They do not. The
rails, opener mount, etc were all out of square, and even the distance
between the rails from the header to the motor was off. I called them
back 3 times before I finally gave up and just fixed it all myself.

The unbroken spring on the larger door is much larger. I was
wondering if it might not be adequate to handle the door by itself. I
installed all the commercial doors on my shop (much heavier doors) and
I still have a set of door spring tommy bars on the shelf.

I just went thru this.
Conventional wisdom is that springs have finite life and you should
replace both springs.
I'd recommend using the exact same ones you have now.
In my case, they don't make 'em like they did 40 years ago. But
there are charts that reliably translate from what you have to what
you can get. I couldn't find anybody local who'd sell me springs.
And the time to order them was longer than I could wait to get my
car
outa the garage. I couldn't lift the door.
I paid the $100 over the mail order spring price to have it done
the same day.
After watching it happen, I think I coulda done it just fine.
But a slip of the tool could cause some serious damage. I was afraid
the guy was gonna have a heart attack when he was tightening the springs.

I have no doubt about my ability to install a new spring (or springs). I
have installed several overhead doors over the years. I even have a couple
sets of Tommy bars in the shop for it.