Lift rails too flexible

lesrhorer said:
The side loading is less than a pound, except when the riser is being raised into place. There is plenty of cross bracing (way overkill, actually) on the A-frame itself. The only thing with no cross bracing is the telescoping section, which is more than strong enough for the near zero lateral load.

All I am asking for is an inexpensive means for stiffening the rails.
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Fair enough, but asking to fix a symphony but playing only two notes is asking a lot of us.

Without knowing really what it looks like, it's tough to make good recommendations.

For what it's worth, a 9 foot run of 1/2" rod (12mm) isn't going to resist bending that much. Won't take Superman to bend it, if you know what I mean.

Now that you have explained a few more details, maybe it will be slightly easier to help some more.
 
WobblyHand said:
Fair enough, but asking to fix a symphony but playing only two notes is asking a lot of us.

Without knowing really what it looks like, it's tough to make good recommendations.

For what it's worth, a 9 foot run of 1/2" rod (12mm) isn't going to resist bending that much. Won't take Superman to bend it, if you know what I mean.

Now that you have explained a few more details, maybe it will be slightly easier to help some more.
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1. It's not a 9' run. It's more like 4'. The total length of the rails is 9' but the lower brace is 4' below the bushings, and the rails start out about a foot above the bushings.

2. The rails are currently flexing, making it more difficult to raise them, but they are not exceeding their elastic limit, even now. Of course, Aluminum has a much higher elastic limit than steel, but I am looking for rigidity, not flexibility.

3. If the rail flexes a little, it doesn't create a problem. It's only when it flexes enough to jam the rails in the bushings that it creates an issue. As I already mentioned, I am going to do some additional things to help, including reaming and greasing the bushings and arranging it so the pull from the hoist is more in line with the rails.

I am not asking how to fix the symphony. I know how to do that. I just need to find a store that sells clarinets cheap, or maybe a way to fix a broken clarinet.
 
7milesup said:
Well, since you expanded on your design further, I think if you put a little more bracing over there ----> and then added some more down there with a couple of bolts at the top, it might work.
12mm rod 9 feet long? https://www.mcmaster.com/rods/diameter~12mm/length~12-ft-/
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Where are "here", and "there"? I already mentioned installing a cross brace similar to the existing one 2 or 3 feet further down:

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Bolts at the top? Why?

That is way, way too expensive, although plain cold rolled should be cheaper. It doesn't need to be precision ground.
 
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Not trying to be troublesome in the slightest, but had you provided dimensioned drawings and photos in the beginning, us members wouldn't have to pry out pertinent details from you. Just a suggestion to make it easier to get better feedback.

12mm rod can be found easy enough. Whether it's good enough to help you, I don't know. Might be ok, if only 4 feet long. Honestly hard to assess without the symphony score, or drawings... It's still a 96:1 ratio in length to width, so it won't be all that stiff. (48:1/2) 1/2" rod is probably a lot cheaper and quicker to source than 12mm. But 12mm is available.
 
What about trus like support?

You could build a box frame at the mid point then use cable like antenna guy wire, 6x20.

Either use turnbuckle or attach cable to end of some all thread that protrudes through the end Plate and a nut to pull tight.

If we understand correctly, this is used to simply lift tall decorations above their mounts, minimal lateral loading could easily be handled with some wire frames.

Bonus is minimal weight.

Sent from my SM-G781V using Tapatalk
 
lesrhorer said:
Where are "here", and "there"? I already mentioned installing a cross brace similar to the existing one 2 or 3 feet further down. Bolts at the top? Why?

That is way, way too expensive, alhough plain cold rolled should be cheaper. It doesn't need to be precision ground.
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He's pulling your leg. He's giving you as much info, as you gave us initially.
 
lesrhorer said:
I don't see why. What difference does it make? I am an engineer, BTW, so I know how to calculate safety limits for loads.

There is more than one item being lifted in more than one location. The heaviest is a 13 foot tall candy cane made from 4" PVC drain pipe. It's about 60 lbs, maybe 70 at most. I am also lifting some porcupine balls, about 25 lbs for the larger one.

The candy cane is also the highest, because it has to be lifted above a 12 ft tall steel pipe. The cane then slides down over the pole.
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thanks for the extra informatioin, so now I can help you better. the candy cane is the first one I can help with now since it is the most difficult. ----the others I will still need more information.
you want to eliminate needing extra help and keep the cost down. that's how I deal with all my projects that I have. I would prefer not to ask for help, and figure my solution so that I can handle it myself and be safe. I also look at materials I already have, and choose the best method to accomplish the task with confidence.
since I now know that you are dealing with a 12 foot steel pipe, and a 14 foot pvc candy cane that has to be raised high enough to slip over and lowered on the pipe, we will forget about using the a-frame framework for this task. I would use the existing 12' steel pipe that must be approx 2 to 3 1/2 inches in diameter for my firm support to work with.
since I worked as a maintenance mechanic at a pultrusion fiberglass company for 23 years I collected a lot of 20' pieces of various shapes of tubing products including some 2 inch OD square tubing that standing vertically next to your steel pipe could handle weight of several hundred lbs easily for lifting your cane and was lighter than metal. I would be using this material, but for your project you could use a 20 foot thin wall 1 1/2 inch or maybe just 1 inch square piece of metal tubing next to the steel pole.
now if you understand this so far, then now we just have to design some simple brackets to clamp to the outside of the pvc candy cane for lifting and fasten around the tubing which will be a few inches next to your steel pole. firmly securing the bottom of tubing to the steel pole with a pivot will allow you to raise your tubing to stand vertical next to the steel pole and then use your brackets to hold it in place till your candy cane is slipped over steel pipe. you can use a small pulley on the top of the tubing to run a small cable for lifting the candy cane and if needed use a come along for lifting the 60lb weight of candy cane to slip over the top of steel pole and be lowered down.
if you need more understanding of using your steel pole instead of an a frame or the simple brackets let me know. what is the OD of your steel pipe?
Dave
 
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