LM8500 (3900) on double headroom track ?

[lmaccaro]

Ok, so I've seen the youtube video where this was done so it know it is possible. I can hand lift my door from the bottom, so that seems possible too.

I have a double track, low headroom, from clopay on a clopay door. I have a normal (not reverse) wind drum.

There does not appear to be anything that I can see just from looking at the action that would make this opener not work on my door. Is there a reason that a double track HAS to be pulled from the top, rather than lifted from the bottom by the drum & cable?

Is it just more prone to coming off the track and I need to watch the tension closely?

I have a 9' wide, 7' tall clopay gallery 3-ply door. I'm guessing it's maybe 250lbs max.

 

[Trey T]

Q1: no. That's silly.
Q2: are you talking about the door balance or door falling out of the track?

You're overthinking it. If you a torsional spring setup, the LM8500 works as long as there's enough room for installation.

btw, here are the description of the jackshaft models:

8500 - latest jackshaft w/ MyQ compatibility
3800 - previous model to 8500
3900 - same as 3800 but w/o sensor and lock

 

[lmaccaro]

Q1: no. That's silly.
Q2: are you talking about the door balance or door falling out of the track?

You're overthinking it. If you a torsional spring setup, the LM8500 works as long as there's enough room for installation.

btw, here are the description of the jackshaft models:

8500 - latest jackshaft w/ MyQ compatibility
3800 - previous model to 8500
3900 - same as 3800 but w/o sensor and lock

Thanks. I have the 3900, just thought some people might still be most familiar with the 8500.

The LM document says:

The 3800/8500 will NOT work on the following types of doors:

Low Headroom Dual track doors: Dual track doors are opened by pulling the top of the door back towards the rear of the garage. The 3800/8500 opens doors by cranking the torsion bar and pulling the door up.

The thing is, I cannot figure out why. The door installer said the same - "jackshaft won't work on dual track, but I don't know why not". It doesn't make logical sense, because I can grab the step bar and pull the door up, which is the same lift point as lifting via the cable.

 

[jstroede]

Pics of what you have please.

John

 

[gnpenning]

A 3900 doesn't lift from the step bar. It turns the spring shaft. With a LHR track You don't have any weight from the door on the cables to speak of. When the opener starts the door down it will turn the shaft faster than the springs will be able to keep tension on the cables. The cables will birds nest and the cable tension monitor will shut down the opener. You will have to fix the cables before the door will be able to go down. It may or may not do this every time but you can bet it will do it when you are in a hurry on the worst weather day of the year. You will get very good and fixing it or put the door company on retainer and hope it doesn't happen nights or weekends.

There will be someone on here that knows more than the manufacture and tell you it can be done , they did it and to do it.... It's your place you decide.

 

[sendokatum]

A 3900 doesn't lift from the step bar. It turns the spring shaft. With a LHR track You don't have any weight from the door on the cables to speak of. When the opener starts the door down it will turn the shaft faster than the springs will be able to keep tension on the cables. The cables will birds nest and the cable tension monitor will shut down the opener. You will have to fix the cables before the door will be able to go down. It may or may not do this every time but you can bet it will do it when you are in a hurry on the worst weather day of the year. You will get very good and fixing it or put the door company on retainer and hope it doesn't happen nights or weekends.

There will be someone on here that knows more than the manufacture and tell you it can be done , they did it and to do it.... It's your place you decide.

Thanks for advice

 

[lmaccaro]

A 3900 doesn't lift from the step bar. It turns the spring shaft. With a LHR track You don't have any weight from the door on the cables to speak of. When the opener starts the door down it will turn the shaft faster than the springs will be able to keep tension on the cables. The cables will birds nest and the cable tension monitor will shut down the opener. You will have to fix the cables before the door will be able to go down. It may or may not do this every time but you can bet it will do it when you are in a hurry on the worst weather day of the year. You will get very good and fixing it or put the door company on retainer and hope it doesn't happen nights or weekends.

There will be someone on here that knows more than the manufacture and tell you it can be done , they did it and to do it.... It's your place you decide.

Thanks. That makes sense, I kind of had a suspicion the problem would be with going down, not up.

I called and spoke with Liftmaster. They did not know why I wasn't supposed to do it.

Do you think if I backed off the tension on the spring, I would have enough weight to make the door want to "fall" as soon as the 3900 started going down?

 

[Trey T]

Same drum location and winding direction like your description

 

[MikeF]

Alot of it has to due with binding in the top roller and top radius pice since it so short. I've been on some jobs where the door will simply not open unless the top is pulled back first. Due mainly to poor install but worn rollers as well. You can add pusher springs, cable keepers and raise the backs of the horizontals a few notches if possible.

What I would do is this, close the door fully. Take a vice grip or pipe wrench and attach it to the shaft outside the bearing brackets. Pull down and see what happens (rotate the spring shaft as if you were the opener) If the door doesn't bind and it raises easily, then you might be in luck.

 

[gnpenning]

What I would do is this, close the door fully. Take a vice grip or pipe wrench and attach it to the shaft outside the bearing brackets. Pull down and see what happens (rotate the spring shaft as if you were the opener) If the door doesn't bind and it raises easily, then you might be in luck.[/QUOTE]


You would need to do this at the same speed and frequency as the opener for a true test.

Same drum location and winding direction like your description

Maybe. Most LHR have the drum outside the track and wind in reverse.. The one in the video is inside. IS your inside or out

Also the video doesn't show if it has pusher springs.

 

[lmaccaro]

Maybe. Most LHR have the drum outside the track and wind in reverse.. The one in the video is inside. IS your inside or out

Also the video doesn't show if it has pusher springs.

My drums are directly over top of the track. They wind "normal" not reverse.

The advice I saw above to raise the back of the track a bit to slant the door down so as to always keep tension (esp when it first starts to close) seems like pretty good advice.

 

[manwithtools]

My drums are directly over top of the track. They wind "normal" not reverse.

The advice I saw above to raise the back of the track a bit to slant the door down so as to always keep tension (esp when it first starts to close) seems like pretty good advice.

Only challenge is you have a low headroom track, you may not be able to raise the back of the track enough to make a difference. As mentioned above, the greatest challenge is the closing action, not the opening.

 

[pattenp]

If you can't raise the back of the tracks use pusher springs to get the door to start closing.

 

[MikeF]

What I would do is this, close the door fully. Take a vice grip or pipe wrench and attach it to the shaft outside the bearing brackets. Pull down and see what happens (rotate the spring shaft as if you were the opener) If the door doesn't bind and it raises easily, then you might be in luck.

You would need to do this at the same speed and frequency as the opener for a true test.



My suggestion was only to see if there is any binding, these openers won't put a whole lot of force into anything before they stop. The soft start/stop compounds the issue

 

[lmaccaro]

Only challenge is you have a low headroom track, you may not be able to raise the back of the track enough to make a difference. As mentioned above, the greatest challenge is the closing action, not the opening.

I have plenty of room to raise the back. Should I go as high as I can?

 

[manwithtools]

It might take a bit of experimentation, I'd start with 2", should not take any more than 4"

 

[gnpenning]

Good luck with this....

 

[MikeF]

2 inches should be plenty