LM 8500 jackshaft opener HELP ?

[cvcman]

Ok I have a 9 x 7 door and cant use a std opener because of a suspended ceiling too close to the door,,,no room for the rail..
So the 8500 seems an option,,first I will have to convert to torsion bar because its suspension spring now,,the way it was explained to me is that the 8500 works on gravity to pull it down,,,,this makes no sense because if I release the opener on my other door that has torsion bar, I can manually lift the door and it will stay in the UP position,,,so how is gravity gonna pull the door down ?
Am I missing something here

 

[Marcm157]

If there is not enough weight to start the downward movement the shaft will spin and cause the cables to unwind. This in turn causes the cable tension sensor to get a false reading that there is no cable present and the door reverses. So I believe the downward door travel does start with gravity then is guided by the cables and torsion spring...

 

[cvcman]

The torsion aids in lifting, right ? So it doesn't help in lowering,,,again take any std door with torsion, release the opener pull cord,,,you can now lift the door half way or all the way and it stays ,,,,so if the 8500 only lifts and gravity pulls the door down and the door stays in the up or half position how will the door go down

 

[bobmulry]

The torsion aids in lifting, right ? So it doesn't help in lowering,,,again take any std door with torsion, release the opener pull cord,,,you can now lift the door half way or all the way and it stays ,,,,so if the 8500 only lifts and gravity pulls the door down and the door stays in the up or half position how will the door go down

Hi,

I have 2 8500's and they work great.....

The opener controls the jack shaft.....

When the jackshaft is turned against spring pressure it winds the spring and the door lowers and it is also the spring pressure that assists the door to be lifted by the opener....

Hope this makes sense,
Bob

 

[pattenp]

The 8500 unwinds the spring tension allowing the door to go down. It's not the same as when the opener is unlocked from the torsion tube.

 

[kbs2244]

What you have is correctly adjusted springs for a normal opener.
But you heard correctly.
8500s need the springs adjusted so the door goes down if not being held up by the opener.
It is just a matter of spring adjustment.


This is because you cannot push on a rope (Or cable)

 

[Jlbc212]

Actually as the 8500 begins to turn the torsion spring shaft to lower the door the springs are being rewound, that is tightened, not unwound. But the weight of the door with the force of gravity is really doing the work in bringing the door down and retensioning the spring(s). The 8500 opener works best on a door with high lift or vertical tracks. However, if your tracks are like most overhead doors where almost the entire door is an horizontal position when fully open, a pair of pusher springs can be installed at the rear of the horizontal tracks. Right before the door reaches the fully open position the top of the door contacts the pusher springs and compresses them. This compression force will push the door downward when the 8500 begins to unwind the cables.

 

[MikeF2316]

The simple way to look at it is the door needs to come down on its own if you disconnect (or cut) the cables. So if you have a low headroom kit, the door might need to adjusted to not open 100% fully. Normal (single track) installs shouldn't have a problem.