Hi Alan. Sorry, I don't have any info on the Lenco's. Brushless is
definitely the way to go for any sub use. Better efficiency, less maintenance,
but pricey.
On the bellows thing.....by minimizing the air volume in the bellows at
sea level, `the contracting air won't be a problem.
Here's what I have done with the crappy Firgelli actuator on the
bench.------
Retracted the rod completely, slipped the rubber bellows over the end and
attached it with duct tape and a hose clamp onto the body of the actuator. I
spread some vaseline on the rod.
I squeezed/retracted the bellows until it was completely collapsed with a
minimum amount of air inside.
I then stretched the bellows "small end" onto the rod and hose
clamped it on making sure no lubricant was near that end. It's a tight
fit on the polished rod end.
I removed the end cap on the actuator where the wires come out, slathered
it with auto gasket silicone and screwed it back on. There's some empty
space inside the actuator body but not a lot.
After letting it set up over night, I hooked the two wires
to a 9 volt battery and extended the rod.
The rubber bellows expanded as expected. What happened was the bellows
"pleats" deformed and got all "wrinkly" because the outer circumference of the
pleats was being forced into a smaller diameter but the pleats themselves
stayed more-or-less touching due to lack of air. The pleats kind of "sucked
down" onto the shaft as it extended. This was part of the demonstration I had
planned for the convention.
I was having fun making it go in and out and so was observing how the
rubber was being stressed and stretched. After the fifth cycle the gasket
stuff on the end cap let go around the wires hole and air got sucked in there.
I could tell easily because the shape of the bellows changed and after it was
fully extended the rubber kept expanding back to it's original shape. Then
when I retracted it again it swelled up like a balloon and finally forced
the air past the duct tape/clamp on the body.
Now this was just a funky exercise on the bench and didn't last very long
but the point was to see what would happen to the bellows.
There is a bit of abuse to the bellows because they're not really
designed to stretch that way, but with a replacement cost of $6 each and
pretty easy to slip a new one on there, if I can get 50 or a hundred
cycles out of the bellows it's a good start.
By looking at how the rubber deforms, it seems to me that a bellows with
a different profile would work without breaking down. The bellows I'm using
are just mud boots for power steering linkage on a car.
If I could get a "spiral" shaped bellows or maybe a "square" bodied one,
that might work better.
Anyway, the concept seems to be workable but the materials need a little
tinkering with.
Frank D.