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"G.R. Patterson III" wrote in message
... Garage door openers drive a sprocket that operates a circular chain. Some of the older units had a block on the chain that tripped a switch when the door was raised. This block could be adjusted to fine-tune the system. My Genie units do not have this. I assume (but do not know) that they simply pull the chain for a fixed distance (most doors are 7' tall). They have essentially the same system, except that the block has been replaced by an analog inside the opener. A worm drive moves a block back and forth, that triggers switches at either end of the range of movement. One end tells the opener when it's done opening, the other tells it when it's done closing. As with the older units, the end result is that the opener simply pulls the chain for a fixed distance. In the case of the older units, the distance is set by the block, in the newer units this is adjustable (within a small range) by a setting that affects the exact position of the ends of the internal mechanism. So. Measure the distance you have to pull your chain to open the hangar door. Work out the ratio between that and 7'. Rig a reduction gear out of two appropriately sized pulleys and a belt and drive that from a chain driven by a garage door opener. Some problems I see with that: * You will want to ensure that the mechanism inside the opener is up to the task. The garage door opener I've had open has a nylon worm drive to turn the main sprocket for the chain. It wears out even under normal garage use, with a counter-spring to help reduce the forces involved. Even if the hangar door is counter-weighted somehow, there may be more friction with the larger door. It may be a lot to ask of little plastic pieces. * The opener has a motor speed sensor that tells it when the thing is getting bogged down too much. Because its main purpose is to avoid someone getting crushed by the door, it's very sensitive. The sensitivity can be adjusted somewhat, but probably not enough to account for a significant difference in force required. * To make matters worse, in combination with the above issues, a reduction gear that increases the effective travel of the opener is necessarily going to increase the force that the opener is required to provide. * Finally, using a belt and pulley system for the reduction gear may result in the belt slipping. If it slips only at the very beginning of the door movement, and it slips exactly the same amount when opening as when closing, this might be okay. But otherwise, it will throw the system out of adjustment. I would say that with a large enough (i.e. expensive enough) garage door opener, the above issues may not be a problem. But then you may start finding that you'd have been better off just designing a custom-made opener mechanism from scratch. Electric motors aren't that expensive, and the rest is just a sprocket, switches and wiring, and possibly a new chain (depending on what kind of "chain" is currently used with the manual opening system). Pete |
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![]() Peter Duniho wrote: * You will want to ensure that the mechanism inside the opener is up to the task. The garage door opener I've had open has a nylon worm drive to turn the main sprocket for the chain. It wears out even under normal garage use, with a counter-spring to help reduce the forces involved. Even if the hangar door is counter-weighted somehow, there may be more friction with the larger door. It may be a lot to ask of little plastic pieces. I had assumed from the description that the opening mechanism on the hangar door is similar to others with which I've dealt. In those, the chain is operated by hand and requires only negligible force. It drives a gear that operates the actual opening mechanism. Usually the gearing is such that the chain must be pulled a considerable distance to raise the door, which is what results in it being so easy to pull around. The doors with which I am familiar would require less from the GDO than normal garage doors would require. As for wearing out, there was a Craftsman unit in the house I used to own when I bought it in 1988. It was still working well when I sold the house in 2001. The two Genie units in my existing home were in it when we bought in 2000 and are doing just fine so far. No telling how old they are. I installed one for a friend back in 1985 and it's still in service. The ones with which I've dealt are pretty bulletproof. You might want to change brands the next time yours goes. George Patterson If you want to know God's opinion of money, just look at the people he gives it to. |
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"G.R. Patterson III" wrote in message
... [...] The ones with which I've dealt are pretty bulletproof. You might want to change brands the next time yours goes. The one I had to fix is a Craftsman. I don't know how old it is. As far as the gearing/load issue goes: a certain amount of work (force over distance) will be required to raise the door. If the hangar door needs to be raised more distance than a garage door does, then more work will be required for the hangar door, all else being equal. Of course, if the hangar door is carefully counter-balanced and is on frictionless mounts, then practically no force is required to move it, and practically no work is required over the entire opening process. But assuming that past the gear that reduces the force required on the chain is a door that is similar in nature to a garage door with respect to the end resultant force required to move it, you don't get something for nothing. In order to "extend" the range of the garage door opener enough to match the total range of the hangar door, you'll have to reduce the leverage of the garage door so much that the force becomes an issue. Pete |
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