I am working on the refrigerator box for the boat. It is top loading and
the lid is to light to press the weather stripping down good. At the same
time I don't want the d*#$ed thing dropping on my head when I am digging in
the bottom of the box to find a lemon for my tequila. So I figured a gas
spring would be a good idea. The problem is how to figure out the closing
force that the spring will give.

The distance between the pivots is 8.5" and the lid pivot will be 1.5" below
the fixed pivot resulting in a downward force when the lid is closed. The
force of the spring is 40 pounds. I vaguely remember that the downward
component of the force is equal to the total force* vertical
distance/horizontal distance) or 40*(1.5/8.5) = 7.058 pounds. Does that
sound correct?

Now the next question is, for the galley slave's sake, how much force will
it take to start opening the lid? The spring will be pushing down 11" from
the hinge and the lift ring is 18" from the hinge. The lid weighs about 2
pounds and is 20" long.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

"Glenn Ashmore" wrote in message
news:wDxHd.21318$EG1.15830@lakeread04...
| I am working on the refrigerator box for the boat. It is top loading and
| the lid is to light to press the weather stripping down good. At the same
| time I don't want the d*#$ed thing dropping on my head when I am digging
in
| the bottom of the box to find a lemon for my tequila. So I figured a gas
| spring would be a good idea. The problem is how to figure out the closing
| force that the spring will give.
|
| The distance between the pivots is 8.5" and the lid pivot will be 1.5"
below
| the fixed pivot resulting in a downward force when the lid is closed. The
| force of the spring is 40 pounds. I vaguely remember that the downward
| component of the force is equal to the total force* vertical
| distance/horizontal distance) or 40*(1.5/8.5) = 7.058 pounds. Does that
| sound correct?
|
| Now the next question is, for the galley slave's sake, how much force will
| it take to start opening the lid? The spring will be pushing down 11"
from
| the hinge and the lift ring is 18" from the hinge. The lid weighs about 2
| pounds and is 20" long.
|
| --
| Glenn Ashmore

Regular fridges have magnetic tape inside the seal to ensure no leakage.
I was thinking that you might work with an overcenter idea on the lid.
Cabinet shops and other woodworking sources will have nice hardware just for
this. If you locate the pivots in the right spot, it will overcenter in the
closed position to hold closed and again in the open and full up position.
I think that if you had the pivot of the spring to the side of the box, at
about a 45 degree angle relative to the centerline of the hinge it'll
overcenter at both ends, assuming you also mount the other end on the side
of the lid. Lower pressure spring, too.

Magnetic strip is out because the lids and frames are fiberglass.

I looked a several overcenter ideas but they all had major drawbacks. First
they are hard to clean which is not good inside a refrigerator. Second,
they have no damp0ing so the light weight lids will either slam shut or fly
open. But mainly to get any significant closing force and still be long
enough to open the lid fully the lid pivot has to be way down in the frige
wasting a lot of space and increasing the possibility that something will
catch and jam it.

Gas springs are just neater and more effective. The down side is they cost
$50 a set and the force can't be adjusted after they are filled. That means
they have to be right the first time.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

"carl mciver" wrote in message
k.net...

Regular fridges have magnetic tape inside the seal to ensure no
leakage.
I was thinking that you might work with an overcenter idea on the lid.
Cabinet shops and other woodworking sources will have nice hardware just
for
this. If you locate the pivots in the right spot, it will overcenter in
the
closed position to hold closed and again in the open and full up position.
I think that if you had the pivot of the spring to the side of the box, at
about a 45 degree angle relative to the centerline of the hinge it'll
overcenter at both ends, assuming you also mount the other end on the side
of the lid. Lower pressure spring, too.

Use 2 magnetic strips, one on top that is a seal and one on the bottom that
is just a magnetic strip like a fridge magnet. You can get the strips in
rolls in a hoby shop. Unless the magnet would mess with your compass
Why not mount the spring part in the case like they do for ovens and deep
freeze?
Glenn Neff
"Glenn Ashmore" wrote in message
news:unGHd.21353$EG1.20955@lakeread04...
Magnetic strip is out because the lids and frames are fiberglass.

I looked a several overcenter ideas but they all had major drawbacks.
First
they are hard to clean which is not good inside a refrigerator. Second,
they have no damp0ing so the light weight lids will either slam shut or
fly
open. But mainly to get any significant closing force and still be long
enough to open the lid fully the lid pivot has to be way down in the
frige
wasting a lot of space and increasing the possibility that something will
catch and jam it.

Gas springs are just neater and more effective. The down side is they
cost
$50 a set and the force can't be adjusted after they are filled. That
means
they have to be right the first time.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

"carl mciver" wrote in message
k.net...

Regular fridges have magnetic tape inside the seal to ensure no
leakage.
I was thinking that you might work with an overcenter idea on the
lid.
Cabinet shops and other woodworking sources will have nice hardware just
for
this. If you locate the pivots in the right spot, it will overcenter in
the
closed position to hold closed and again in the open and full up
position.
I think that if you had the pivot of the spring to the side of the box,
at
about a 45 degree angle relative to the centerline of the hinge it'll
overcenter at both ends, assuming you also mount the other end on the
side
of the lid. Lower pressure spring, too.

On Wed, 19 Jan 2005 13:26:44 -0500, "Glenn Ashmore"
wrote:

I am working on the refrigerator box for the boat. It is top loading and
the lid is to light to press the weather stripping down good. At the same
time I don't want the d*#$ed thing dropping on my head when I am digging in
the bottom of the box to find a lemon for my tequila.

How about using a toggle clamp? Fully aerobatic, tight and adjustable.
Extra points if you can make it one-handed and disguise the industrial
appearance. ;-)

Wayne

On Wed, 19 Jan 2005 13:26:44 -0500, "Glenn Ashmore"
wrote:

I am working on the refrigerator box for the boat. It is top loading and
the lid is to light to press the weather stripping down good. At the same
time I don't want the d*#$ed thing dropping on my head when I am digging in
the bottom of the box to find a lemon for my tequila. So I figured a gas
spring would be a good idea. The problem is how to figure out the closing
force that the spring will give.

The distance between the pivots is 8.5" and the lid pivot will be 1.5" below
the fixed pivot resulting in a downward force when the lid is closed. The
force of the spring is 40 pounds. I vaguely remember that the downward
component of the force is equal to the total force* vertical
distance/horizontal distance) or 40*(1.5/8.5) = 7.058 pounds. Does that
sound correct?

No. That's the tangent, you need the sine.

Now the next question is, for the galley slave's sake, how much force will
it take to start opening the lid? The spring will be pushing down 11" from
the hinge and the lift ring is 18" from the hinge. The lid weighs about 2
pounds and is 20" long.

You left out some details that I'll fill in with assumptions. If the
hinge is at the same elevation as the fixed pivot for the gas spring
and the lid is level when closed, the spring holds the lid shut with
a force of 6.94 lb. The spring is at an angle of -10 degrees,
40*cos(10) = 6.94.

Equating moments about the hinge, the force on the ring to open it
will be 4.38 lb plus 10/18 of 1 lb from lid weight, or 4.93 lb.