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Message |
    
Arthur Ransom
Registered
Username: Akransom
Post Number: 39
Registered: 09-2006
| | Posted on Wednesday, April 25, 2007 - 11:29 pm: | 
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In the theoretical world V rollers will have a larger bearing surface if they roll perfectly aligned on a V track. In the real world that the MechMate machine lives in does it really matter that the edge of the track is not a V? Off the shelf angle iron has a slightly rounded edge so the V rollers would have two relatively small bearing surfaces with a high load PSI but is it a high enough load to round it over or wear fast enough for us to care? Most of us work in wood which expands or contracts daily and I expect is in excess of the MechMate tolerances. Anyone ever tested their machine to see what tolerances it will hold? Our tolerances are sloppy compared to the guys that work in metal and isn’t plus or minus .01” more than adequate? Just wondering if we aren’t beating a dead horse on the V track issue. |
Gerald_D
Registered
Username: Gerald_d
Post Number: 1288
Registered: 11-2005
| | Posted on Thursday, April 26, 2007 - 07:00 am: |
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Arthur, you are so right on this! There is a very mistaken belief that CNC = accuracy or tight tolerances. The typical woodworker works with nothing better than a tape measure or steel rule and he needs a CNC to give him speed and relieve him of repetitive tasks - he does not need a machine that gives him a whole new toolbox of sensitve measuring instruments! A "crudely" built MechMate satisfies the typical woodworker requirements. Put some more effort/money into a MechMate and you get something of a precision that matches your input - but, you will probably have to buy some finer measuring tools then. |
Arthur Ransom
Registered
Username: Akransom
Post Number: 40
Registered: 09-2006
| | Posted on Thursday, April 26, 2007 - 03:55 pm: |
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Along this line when building a machine for wood why couldn't I just take 1" angle iron and use the 90 degree as my rail? Weld tabs every 6" for bolting it down and straighting?+ |
Gerald_D
Registered
Username: Gerald_d
Post Number: 1302
Registered: 11-2005
| | Posted on Thursday, April 26, 2007 - 04:08 pm: |
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1. You will have nothing to attach the rack to.
2. Welding every 6" will warp the rail quite a bit.
But, if you lay a 2.5" x 3/16" flat bar down and then glue/weld/cskscrew/dstape a 1" x 3/16" angle iron on its end, run the roller directly on the tip of the vertical leg. Load 400 pounds on the gantry, roll it up and down a hundred times and you'd have a pretty good rail. 
Your local plate-bending shop might even bend you a nice "L" - but they seldom do. Their tools are normally worn in the center and you see the middle 4 ft of a 12 ft bend is bent more at the ends than in the center.  ShopBot used bent 3/16" rails till recently with size 2 wheels |
Charlie T
Registered
Username: Popbing
Post Number: 25
Registered: 11-2006
| | Posted on Thursday, April 26, 2007 - 07:01 pm: |
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Ive wondered about running right on the back side of angle aswell. Ive got my rails done, but for some people this might work good. Just a little hand sanding and its smooth. Flat bar with angle laying on it ,both legs down, point up. With that comes other problems (like everything)with the mounting of it. I dont know the best way to mount it.
The design is great as it is now, but its hard to watch so many strugle with this.
*sidenote*
MY rails are so nice that when I run the bearing on them (by hand) I can feel dust on the rail I whipe it with my finger and its as smooth as glass. |
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