Question about moving chain hoist on roll-up doors

The two large 10x12' rollup doors on my building both have the chain hoist located on the left side of the drum. For the left door, I want to move the hoist to the right side of the drum so that both chains are hanging in the middle between the doors. The manufacturer offers hoist brackets to allow mounting of the hoist on either side of the drum and both ends of my drum appear to have holes to mount the chain sprocket. It also appears the hoist can be assembled either way to create a mirror image version of the one I have.

This is the one I want to move to the other end:



This is where I want both chain hoists to be located:



Here is a close-up view of the hoist. (Disregard the red labels as I'm recycling this image from another thread)



To get the chain sprocket off the left side, I will need to temporarily support the drum, remove the split clamp holding the main shaft and carefully slide the sprocket off the shaft. Then after reinstalling the clamp on the left side, I will need to repeat the process on the right side to install the sprocket in its new home.

So on to the question. There is no doubt that there is a pretty substantial torsion spring inside the drum. Will one clamp be enough to hold the main shaft from turning while all this is being done? Also, should I do it with the door open or closed?

Another alternative which eliminates touching the shaft clamps at all is to cut a slit in the sprocket to allow it to slide of the shaft. I could splice it back together once up on the other side. Would this be a better method than messing with the clamps?

Any other tips/tricks would be appreciated. Thanks in advance for your input.

shopnut

Are you sure there is a torsion spring inside? It has a gear reduction for the chain to aid in lifting. We have similar chain operated doors at work and I have not really looked at them close for springs but they appear to have more pull when the door is more closed (more weight pulling down) that we need to put the chain in its locks to hold it in place.

shopnut

For the other question. I would like to leave the door closed so it stays in its tracks and make a type of stand out of some 2x4's or 2x6's to support the roll and have it leaned back to the wall then you can push the support legs in a little to raise it up past the metal bracket to get to the sprocket change out.

Not sure on your brand, but the Wayne-Dalton rollup doors have tension springs: http://commercial.wayne-dalton.com/filelib/file/self_storage/DS-200_install.pdf

I'd assume that your setup is going to be similar.

If there is a spring, it will be under more tension when it is closed than open.

I am not all that familiar with roll up garage doors.
But I have the same idea on my hurricane shutters at my Florida place.
They do not have torsion springs in them.
They depend on the gear ratio for their ease of opening and closing.

But it seems to me that, even if they did have springs, they would follow the same engineering concept of regular panel doors. On them the springs are relaxed when the door is open. The tension is there only when they are close to help with the lifting.

So, if you do your work with the doors up, the springs would be relaxed.

Mine has a very large torsion spring in it!!! It also has the manual/power gearbox. I'd bet yours has a spring as well - these suckers are pretty darned heavy - ask me how I know

Thanks for the responses. The question about whether or not it had a spring prompted me to take a closer look to be sure. I found the manual and it is located here: Link to Door Installation Manual

Here are a couple of exploded views to remove all doubt:



While in the manual, I snagged a couple of other views to help explain things.

The way the sprocket attaches to the drum:



The way the main shaft attaches to the support bracket:



Here is the way they explain how to tension the springs (although I believe mine do not need any adjustment). They explain to raise the door to "Full Top Position" in Step 8 in the manual.




akdiesel - a homemade floor stand is a good alternative to slinging it from above somehow, as I originally planned.

PAToyota - It looks like that Wayne-Dalton door you referenced is built fairly close to mine. They even show the same pipe wrench adjusting method.

kbs2244 - I believe some of those hurricane shutters are built very similarly to my rollup aluminum curtain on my shop TV. It only has a worm drive to raise and lower it - no counterbalance springs.



HemiRambler - The weight is another thing I will need to contend with if I unbolt one end. Sounds like you have direct experience. What did you use to lift or support the drum?

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Sooooooo… the door up/door down decision will be decided by whether I want to deal with the extra door weight or extra spring tension. Door up = heavy drum weight, but low spring tension. Opposite holds true for door down.

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Ignore the following images

I highly recomend doing it with the door fully open - don't take a chance with the tension.

I believe even with the door fully open you still spring tension. Just like a normal overhead door does.
You may be able to bolt up a bracket similar to the use of the pipe wrench design but a better way to hold the spring from spinning.

Door open is probably the way to go, but I will have to keep in mind if something goes wrong, I may not be able to close the door for a while and that could present a security and critter issue.

The doors are pretty balanced and I can stop they just about anywhere and they stay put without tying off the chain. But I believe there is some tension when full up. The manual states that for initial set-up, you should start with two turns of preload with the door full up. The doors were installed by "professional" installers so I hope they're in that ballpark.

Thanks for the input guys.

This may sound a little bit silly but... What do you think about sourcing a spare set of hardware (or making your own) and installing it on the other side first? You might even get away with having the hardware on both sides and just taking the opening chain off of the lower pulley.

mdbeck1 - That's actually a good idea because I wouldn't have to mess with the left side at all and would only have to figure out a way to get the new sprocket on the right side. I would be willing to abandon the old stuff and buy new parts for the other side, but the new covers for the drums (should be showing the plan for that in my build thread this week) requires the complete removal of the hoist on left side.

Thanks for your input. It's all going to get me to a solution here.