O/H dust collection arm...updated question!

Jim O'Dell

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Between Aledo and Fort Worth, TX
Some of you may know that I've been working on the overhead dust pick up for my table saw. I have finished the second version today, and I'm having the same problem. I have tried the mount to the side (ceiling mount) and to the rear. But there is too much play side to side on the pick up housing. The wood doesn't want to slide under the pick up. Possibly my curve at the front is too abrupt, and needs to slant more to to ride up over the wood. But the whole housing moving side to side bothers me a lot. How stable are the commercial units that mount to the ceiling or the back right of the extension table? Any ideas on how to stabilize this set up?
DSCN1785.jpgDSCN1786.jpgDSCN1787.jpgDSCN1788.jpg
The first picture shows the pick up, and hinging mechanism. I used the Wood Central Blade Guard article to go by. It is almost an exact copy...very minor changes in lengths beyond the pivot points, except for the extension from the attaching point to the dust shroud. This had to be lengthened because of where my TS has to sit in relation to the mounting point for the arm. (Lights directly above the TS) I'm sure this introduces some movement, but I'm surprised at how much I'm getting...3" either side of center, maybe a tad more. The second picture shows the mount at the ceiling that allows me to move the whole unit up and out of the way. It can also be taken out or pivoted in 90 degree increments to be further out of the way. Picture 3 shows the mechanism minus the dust pick up. Picture 4 shows the unit recessed as far as it will go up. (I'm limited by the shallow attic space or it could go all the way to the ceiling.)
The problem again is side to side movement as you are at the front of the TS. I hope someone has an idea. I'd hate to think about scraping 2 weekends worth of work, not to mention the steel and aluminum. :eek: THANKS!! Jim.
 
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Jim,
At my former employer we had overhead guards. They used aircraft cable splayed in four directions (about 30 degree angles) to stabilize the guard. My guard has rods one to th rear of the saw, one to the right. There are turnbuckles for adjustment/tightening as well. The cables would allow easier movement out of the way with clevis or hair pins.

http://www.pennstateind.com/library/TSGUARD.pdf

(see page 5)

Is that what you were looking for?

Wes
 
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Hi Jim. It is clear that you have been working hard on the DC. My question is how close are the tolerances you are working with? Ideally you want one piece to just barely slide into the larger one. In my mind, a 1/32" slop may be too much clearance.. The same would be true for all the components.

If you are having problems with the square ceiling mount, I would a front-to-back and a side to side brace to give extra rigidity. I would place the brace at the point of the lowest point when the unit is extended to its vertical limit, i.e., hitting the attic ceiling/roof. You would need only two added braces. One behind the vertical, and one to one side of it. A device similar to your ceiling mount, with the braces mounted to it, should work.

If I am missing the point, please excuse my babbling. :(

BTW, Texas Towers in Plano carries aluminum tubing that is made to just slide into the next larger sizes.
 
Ken, actually the piece at the ceiling is very tight. It is a dog grooming contraption that holds grooming arm on to the grooming table. Nice tight fit of the 3/4" pipe. Now the pipe is not as thick walled as I wanted, but is about the same that the grooming arms are made from. I think it is the natural twist of the aluminum. I have a plan to help get rid of the 15.5" piece of tubing from the pivoting mechanism to the shroud by angling the piece at the ceiling so the arm comes down to the table saw. I'll see if that helps. At least it will take part of the problem with that piece acting like a lever and exagerating the movement out of the picture. Thanks for the site on the aluminum. That may come in handy for the future.
And Wes, I thought about building an arm like that...may have to yet. But I wanted to see if a ceiling mount would work as well. I think part of my problem is that I can't go straight up with the mechanism.
If my idea doesn't help, I'll get some U-Channel aluminum to replace the flat pieces on the vertical part. Some of the twist could be coming from the flat aluminum pieces.
Thanks guys! Jim.
 
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The extension length supporting the hood is really working against you here. If you look at the TSGuard that Wes posted (I also have this), the hood's weight is centered under the vertical arm.

I get the best performance with the hood well under the pivoting mechanism. I this position I have the counterweight providing almost no downward pressure; just enough to keep the hood down.

You can sort of see the positioning in this old pic:
 

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Ken, is this a decent design of your idea? If so, thanks!! It works great. No wobble, well maybe a 1/4" each way. But it's WAY SOLID!! And it still retracts up into the ceiling to get partially out of the way.
Now I need to get a couple star washers to hold the knob bolts when I tighten them up, and a couple nuts with the nylon inserts to lock the bolts down on the upper pivot mounts. Oh, and bolt the dust pick up head to the arm.
Thanks everyone! Jim.Edit: Can't believe I forgot to add the pictures! Must have been getting ready for the 'Boys to play! :eek::eek::eek:
First shot is of the mechanism in the down position.DSCN1792.jpg
Second shot is in the retracted position agains the ceiling. DSCN1790.jpg
Maybe this will make more sense. Jim.
 
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Updated question...

What have you used for weight for the counter-balance, and how did you attach it? I have worked out about how much weight I need, but figuring out an attractive/hidden way to implement it is a little beyond my vision! I have access to old wheel weights, although I don't have anything to melt them in to then pour into a casting of some sort. Show me/tell me how you have done yours. TIA!! Jim.
 
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