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+-- Thread: garage door opener (/showthread.php?tid=7376456)
RE: garage door opener - Roly - 08-14-2024
(08-14-2024, 08:52 AM)jteneyck Wrote: Let me try it this way, Fred. With my current chain drive, it pulls the door up to open. To close, it reverses and pulls the door down. Ideally, the torsion springs are wound so that the door has almost zero gravity. It is held closed by the force of the chain pulling the door down.
The jackshaft opener operates the same way, but instead of being connected to the top of the door like my chain drive system is, it's connected directly to the shaft with the torsion springs. The opener drives the shaft to pull the door up, and reverses to pull the door down. The torsion springs transmit their torque to the cables that do the work. There's no difference between how it works regardless of the type of opener used.
John
How does it push on the cable ? Where is anything connected to the door that can pull down. It is just the weight of the door otherwise the spool with the cable would backlash so it can not be zero gravity to start down or have pusher springs to get it started. Some of the horizontal sections of track are angled down in front to get the door started then the cables lower the door slowly. Roly
RE: garage door opener - fredhargis - 08-14-2024
That's the part I don't get either Roly. It seems like if the door is open, and no opener attached, no have to pull it down with a attached cord about 1/2 way before it starts to go down on it's own. It's the pulling thing that's missing for me.
RE: garage door opener - Stwood_ - 08-14-2024
This is the only way I can explain it. Watch the video.
https://www.google.com/search?client=firefox-b-1-d&q=how+does+a+jackshaft+opener+work#fpstate=ive&vld=cid:68cc06be,vid:Wlssvr9irfQ,st:0
Go down to the first youtube video
RE: garage door opener - fredhargis - 08-14-2024
I watched that from your earlier link, and it really doesn't how much on the down operation. Then I looked at the manual and it's not all that clear either. It really looks to me like gravity is what shuts the door, but gravity can't get it started going down like a pull on a cord, or the push that a standard opener provides. That video did explain that the door must be in a well maintained smooth operating condition..which is kind of what I tried to imply earlier. But thanks fro trying to get me over the hump.
Edit in: I just found the video on Utube which points out what I've been saying, that opener can't push the door down. It's alittle long, so if interested go to somewhere around the 14:30 mark and you'll see the problem he had.
https://youtu.be/wIIt-GMECwE?si=_LCuhYGBYSEMZ_oz
RE: garage door opener - JosephP - 08-14-2024
The jackshaft opener definitely has control of the door on the way down - not just gravity. Mine have a smooth close at the end...slows it down before 'landing'.
I don't understand your concern with the cable. That is pulling on the bottom of the door.
Regardless of how it is being opened all of the pieces are moving together...the top of the door, the bottom of the door, the cable, the jackshaft, the spring, etc... Pick one of those, mechanize the movement of that and the rest of the parts will STILL move at the same time.
RE: garage door opener - Roly - 08-14-2024
(08-14-2024, 05:01 PM)JosephP Wrote: The jackshaft opener definitely has control of the door on the way down - not just gravity. Mine have a smooth close at the end...slows it down before 'landing'.
I don't understand your concern with the cable. That is pulling on the bottom of the door.
Regardless of how it is being opened all of the pieces are moving together...the top of the door, the bottom of the door, the cable, the jackshaft, the spring, etc... Pick one of those, mechanize the movement of that and the rest of the parts will STILL move at the same time.
The cable is pulling up on the bottom of the door so it can control the speed going down from gravity or pull it up to close. It can not push the door down. Roly
RE: garage door opener - jteneyck - 08-14-2024
(08-14-2024, 12:50 PM)fredhargis Wrote: I watched that from your earlier link, and it really doesn't how much on the down operation. Then I looked at the manual and it's not all that clear either. It really looks to me like gravity is what shuts the door, but gravity can't get it started going down like a pull on a cord, or the push that a standard opener provides. That video did explain that the door must be in a well maintained smooth operating condition..which is kind of what I tried to imply earlier. But thanks fro trying to get me over the hump.
Edit in: I just found the video on Utube which points out what I've been saying, that opener can't push the door down. It's alittle long, so if interested go to somewhere around the 14:30 mark and you'll see the problem he had.
https://youtu.be/wIIt-GMECwE?si=_LCuhYGBYSEMZ_oz
Fred, you're smarter than me on this. I now understand your concern. The guy on your link is a hack, I'd wouldn't follow anything he does. The link from StWood, however, is from an actual company. The door in that video is on a track that never goes horizontal, which would mean the door always is trying to go down as long as the spring tension is set correctly - just short of zero gravity. That video also describes the lock system they use as part of the system, which is pretty much confirmation that the jackshaft does not hold the door down. Thanks for helping me understand the crux of the problem.
John
RE: garage door opener - JosephP - 08-14-2024
You are WAY over thinking this. Pull the string on your regular garage door opener so you can move it freely. Now, get a pipe wrench and turn the shaft. What happens? I don't care if you want to start with the door up or down...what happens when you turn the shaft?
RE: garage door opener - JosephP - 08-14-2024
(08-14-2024, 07:14 PM)jteneyck Wrote: .... That video also describes the lock system they use as part of the system, which is pretty much confirmation that the jackshaft does not hold the door down. Thanks for helping me understand the crux of the problem.The lock is just extra security...it doesn't hold anything down. Door will work perfectly normal if that wasn't installed.
John
RE: garage door opener - fixtureman - 08-15-2024
(08-14-2024, 07:50 PM)JosephP Wrote: The lock is just extra security...it doesn't hold anything down. Door will work perfectly normal if that wasn't installed.
You are right about that the door uses gravity to lower. The opener will not hold the door down but the jackshaft will hold the torsion bar from turning making it hard to lift but not impossible.