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09-26-2012, 03:27 PM
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Join Date: Feb 2008
Location: Pensacola, FL
Posts: 374
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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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RV-? in planning stages.
RV-14 #140050 SOLD
Permanently willing to contribute fuel for RV rides
Helicopter ATP/CFI(I)
ASEL/AMEL Commercial/Inst/CFI(I)
Aerobatic Instruction available
Atlanta based.
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09-26-2012, 03:44 PM
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Join Date: Dec 2009
Location: Boulder, CO
Posts: 4,435
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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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09-26-2012, 03:44 PM
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Join Date: May 2009
Location: Houston, TX
Posts: 531
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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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-Rick Greer, VAF #2492
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09-26-2012, 06:30 PM
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Join Date: Feb 2008
Location: Pensacola, FL
Posts: 374
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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.
__________________
RV-? in planning stages.
RV-14 #140050 SOLD
Permanently willing to contribute fuel for RV rides
Helicopter ATP/CFI(I)
ASEL/AMEL Commercial/Inst/CFI(I)
Aerobatic Instruction available
Atlanta based.
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09-26-2012, 07:25 PM
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Join Date: Nov 2005
Location: Asheville, NC
Posts: 2,692
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Quote:
Originally Posted by DCat22
and thus have about the same basic stability as just having three legs?
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Yes it would
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Bill Pendergrass
ME/AE '82
RV-7A: Flying since April 15, 2012. 850 hrs
YIO-360-M1B, mags, CS, GRT EX and WS H1s & A/P, Navworx
Unpainted, polished....kinda'... Eyeballin' vinyl really hard.
Yeah. The boss got a Silhouette Cameo 4 Xmas 2019.
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09-26-2012, 08:55 PM
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Join Date: Feb 2007
Location: San Diego, CA
Posts: 1,670
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"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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Pete Hunt, [San Diego] VAF #1069
RV-6, RV-6A, T-6G
ATP, CFII, A&P
2020 Donation+, Gladly Sent
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09-27-2012, 06:39 PM
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Join Date: May 2012
Location: Bealeton Virginia
Posts: 557
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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!

__________________
Bob "Skyking" Corriveau
"PRINCE TRAPPED IN A PILOT'S BODY"
Yes I paid my =VAF= membership dues!
RV-8 QB Reserved N212KB
ATP
CFI/CFII/MEI
Build Site: http://www.mykitlog.com/skykingbob/
"Nothing worthwhile has ever been accomplished without inspiration, determination, and perspiration!"
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09-27-2012, 06:42 PM
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Join Date: Oct 2008
Location: Utah
Posts: 8,151
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Bob, sell the patent to tkatc. His rolling benches are wobbly 
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09-27-2012, 07:13 PM
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Join Date: May 2012
Location: Bealeton Virginia
Posts: 557
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Middleman
Quote:
Originally Posted by Vlad
Bob, sell the patent to tkatc. His rolling benches are wobbly 
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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 )
__________________
Bob "Skyking" Corriveau
"PRINCE TRAPPED IN A PILOT'S BODY"
Yes I paid my =VAF= membership dues!
RV-8 QB Reserved N212KB
ATP
CFI/CFII/MEI
Build Site: http://www.mykitlog.com/skykingbob/
"Nothing worthwhile has ever been accomplished without inspiration, determination, and perspiration!"
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