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Well Frank, Build it and they will come. ;}
I think I understand your idea better now. Not that you had it all
figured out before now. One thing comes to mind with your design. If
you have the contact area of the flat part of the leaf spring glide on a tube of
Delrin that is rolling on a SS rod that is part of the upper hatch hinge means
you would have less friction.
That's my opinion, if you don't like it, I have others.
;}
Do I need to make a CAD model? ;}
I'm going to need another computer. I can't get any other CAD work
done when the CAD computer I have is parsing FEA work most all day these days.
Brent
From: ShellyDalg@aol.com
Sent: Thursday, August 27, 2009 1:11 PM
Subject: Re: [PSUBS-MAILIST] Brent's hatch I Plan on using a leaf spring to counteract the hatch weight.
I put a tab on my hatch that pushes the leaf spring up when it's closed.
The reasons for this are......
#1. Several coil springs I've seen are dripping rust on the hull
because the flexing metal won't hold paint. A leaf spring, doesn't need to have
a good coat of paint, just a coating of "Plasti-dip" and the amount of
flex/stretch is minimal.
#2. Most coil spring configurations push the hatch "UP" at the back, or
wherever the hinge is. It takes the hatch dogs to pull it down against the "O"
ring. Because the hinge points are slotted to allow for "O" ring
expansion/compression, the coil springs push the hinge rod up a little
bit.
The leaf spring is pushing "down" on the hatch in the closed position. It's
levered out beyond the hinge pin, but still exerts a downward force on the pin,
pushing the back of the hatch down onto the "O" ring.
#3. The hatch hinge with three legs and a stainless tube running through it
for the hatch pin is much more steady and alignment is precise when it closes,
unlike double tabs and bolts like most coil springed hatches.
#4. Like a coil spring, the leaf spring tension is strongest when the hatch
is closed. As the hatch is opened, the leaf bends less, until finally it's not
even in contact with the hatch. Unlike a coil spring, the leaf can be removed
very easily when the hatch is open, without messing with the hinge mechanism. I
have nylon washers for smooth operation and corrosion protection between
the parts that swivel, and "O" rings to keep the grease inside the tube
where the pin is. The leaf spring can be adjusted in place to give as much
resistance as I need to balance the hatch. It can be adjusted
so the hatch barely pops open when the dogs are released, or as
heavy as I want the hatch to be. Regardless of how much tension is on
the spring, it always is pushing the hatch pin down.
#5. OK...my favorite.....This thing is so simple to build, and talk about
cheap! I got the spring for nothin' and the little bit of steel for the mount
was a few scraps laying under the bench.
That's my theory on hatch springs. Frank D.
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