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  #1  
Old 09-26-2012, 04:27 PM
LAMPSguy's Avatar
LAMPSguy LAMPSguy is offline
 
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Location: Pensacola, FL
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Default Automatic, Self-shimming workbench

First, this is to shim (prevent from wobbling) a workbench, NOT level it. Level would be to have the bench top normal to the gravity vector. This technique will just prevent your bench from developing a wobble.

Background: A plane (in this case your garage floor) is defined by three points. But three points of contact are unstable for a bench. So, how to have 4 points of contact (stable) act as three to define the irregular plane of your garage floor?

See picture (ignore poor drawing skills)



As you see, the two casters on the left are fixed, as well as the two on the right. The two on the right though are free to pivot around the bolt to "self shim" for floor irregularities. If you have an extremely problematic floor to deal with and worry about stability, standard screw-type levelers can be used just inboard of the right casters as "overtravel bump stops" and you just set for how much clearance you want.
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  #2  
Old 09-26-2012, 04:44 PM
David Paule David Paule is offline
 
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Default

Ya gotta make sure that the trunnion - that's the green line - is quite stiff in flexure, with low friction, lest the feature fail to work as conceptualized.

You can't just drop a bolt through it and tighten it up....

Dave
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  #3  
Old 09-26-2012, 04:44 PM
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DCat22 DCat22 is offline
 
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Default

I like it.....

But -- without travel limiters -- wouldn't the bench still pivot around the bolt, and thus have about the same basic stability (if loaded on a corner) as just having three legs? (I didn't sleep last night...so...could be tired. )

EDIT: I think I meant what David said better.
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  #4  
Old 09-26-2012, 07:30 PM
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LAMPSguy LAMPSguy is offline
 
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Default Kinda

Yes it has to be strong/stiff.

Yes, it can be just a bolt, which type it important.

Sure, you don't crank down on it. I use stainless steel carriage bolts, a washer with a square hole for the head. Between the two horizontal pieces: Washer, spacer, washer.

Steel in a pine 2x4 pivots just fine for what we are doing with it here. I imagine (have not used one to build a plane yet, but I am working on that) with the weight required of light aluminum this will work just fine. I have used it for years for woodworking...heavy hardwoods, and it works as advertised to reduce the annoying wobble. You just dont have a perfectly level top.
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  #5  
Old 09-26-2012, 08:25 PM
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rzbill rzbill is offline
 
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Default

Quote:
Originally Posted by DCat22 View Post
and thus have about the same basic stability as just having three legs?
Yes it would
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  #6  
Old 09-26-2012, 09:55 PM
PCHunt PCHunt is offline
 
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Default

"Simplicate, and add lightness." Why not just put a 3rd wheel where the trunnion goes? What does the extra wheel, bar, and trunnion add
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  #7  
Old 09-27-2012, 07:39 PM
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Skykingbob Skykingbob is offline
 
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Location: Bealeton Virginia
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Default Retractable gear on table!

I built two benches with retractable gear! They are easy to use and work great for stability (wheels up) and portability (wheels down)

Gear down!





Gear up!

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  #8  
Old 09-27-2012, 07:42 PM
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Vlad Vlad is offline
 
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Bob, sell the patent to tkatc. His rolling benches are wobbly
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  #9  
Old 09-27-2012, 08:13 PM
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Skykingbob Skykingbob is offline
 
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Default Middleman

Quote:
Originally Posted by Vlad View Post
Bob, sell the patent to tkatc. His rolling benches are wobbly
Vlad......you be my salesman...I pay 50% commission of the first 25% of the net 10% of profit less costs and 35% government taxes(Oops ......I think that means you will have to pay me to sell my product to cousin Tony)
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