Your stand looks like the one for my sander, which was from an commercial ironing board. Nice welded tripod stand with adjustable column height, and a 5" x 15" platform of 1/4" steel.
Ken Grunke
I like your mule theory, a lot easier to understand than a mathematical explanation.
John
The stand came from a display stand my father used to use when we had the carpet business. Sold that in 1977, so it is proof if you keep somthing long enough... Geoff
Note well, do not let clean laundry fall on dirty or greasy machinery if you ever want to,..um.. eat again :-)
No it is all fabricated from bits and pieces. It pivots behind the front wheel, with an adjustment screw and lock screw. Geoff
Rather than a thought experiment, you can demonstrate the self-centering using a crowned pulley and belt setup, first hand; or, a simple sketch will do.
Let's take the real-life belt example, first.
With the machine shut down, purposely pull the belt halfway off the crowned pulley.
Then, look down on top of the straight portion of the belt between the two pulleys. Observe how the flexible belt has taken on a curve. You'll notice that the curve in the belt has kicked the main run of it in the direction toward the pulley's center.
So, as the portion of the belt between pullies approaches the pulley where it is half off, it is headed toward the center of the pulley.
Thus, it self-corrects and runs centered on top of the crown.
If you don't have a belt and pulley setup handy, you can demonstrate the same thing with a sketch, viewing the belt from above the portion between the pulleys. Be sure to take into consideration that the belt is flexible and will fully contact the periphery of the pulley, even when it is half off the pulley.
Simply stated, when a belt is off to one side of a crowned pulley, the crown kicks the approaching run of belt over so that it heads toward the peak of the crown.
One of these days I'll post a drawing on my web site.
Regards,
Orrin
Why don't you take a trip down to your local home improvement store and have a look at the bandsaws, sanders and see for yourself how things are done.
Perhaps you could take your digital camera and grab some snapshots for further evaluation.
Try this link:
----- Original Message ----- From: "Too_Many_Tools" Newsgroups: rec.crafts.metalworking Sent: Tuesday, March 08, 2005 3:34 PM Subject: Building a Belt Grinder
On 9 Mar 2005 07:52:25 -0800, the inscrutable "Too_Many_Tools" spake:
Build, of course. I bought the Delta 1" and will build future belt sanders.
Free motors can be had from scrap washers and dryers. You don't want too much horsepower behind a belt or you'll tend to burn things. Let the speed variation show that you're pushing too hard so you learn to ease up.
Several. You could set them up for different types of jobs or identically save for the grit, then grind and finish in 2 quick steps.
========================================================== I drank WHAT? +
A feature I added to my 1" belt grinder is variable speed. I changed out the motor to 3-phase and bought a VFD to match.
It has been a wonderful thing to have on a general purpose grinder. You can run fast with a coarse belt for rapid stock removal and slow with a polishing belt for finishing, knife sharpening, etc. Medium-low speed with plastics avoids melting.
You can also tune for minimum vibration for precision work. Any belt arrangement will have likely have several fixed speeds where the unsupported belt vibrates like a guitar string. Variable speed lets you avoid those vibrations.
Randy
PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.