Deleted
Deleted Member
Member since January 1970
Posts: 0
|
Post by Deleted on Mar 9, 2013 14:59:03 GMT -5
Trying to rig up a simple grinder, I've got a 1750rpm motor, with a 2" pulley. Going to a simple Chicago arbor, with a 100grit Sil-carbide wheel. I'm getting confused, To slow the arbor down a little Do I need a larger or smaller pulley? I've also got a gravity feed water feed to hook up as well. thanks for the help
Dave
|
|
quartz
Cave Dweller
breakin' rocks in the hot sun
Member since February 2010
Posts: 3,341
|
Post by quartz on Mar 9, 2013 23:04:51 GMT -5
To slow the arbor relative to motor speed, you need a larger than 2" pulley on the arbor. i.e., if you use a 3" pulley on the arbor, divide 3 by 2 [motor pulley dia.], =1.5. Then divide 1750 [motor speed] by the 1.5 from prev., you get arbor speed of 1166.6 R.P.M. If you already have a pulley on the arbor, you then need one smaller on the motor than on the arbor. The math is done the same way, but w/different diameters. Hope this helps. Larry
|
|
|
Post by deb193redux on Mar 9, 2013 23:29:55 GMT -5
google "pulley calculator" and get the math done for you
|
|
|
Post by mohs on Mar 9, 2013 23:35:06 GMT -5
Yep... if that 2" pulley is on the arbor then a smaller pulley on the motor shaft (a 1" for instance) would slow the speed down.
If both pulley are 2" than you get one to one ratio and I found that to be a bit fast on my Lortone cabber
What I have is an adjustable pulley on my motor It adjust from 1" to 3" diameter I usually have it adjusted at just over 1"
On the arbor is a 2" pulley It pretty set in its way I'd have to pull the arbor to change the size of that pulley
so with this combination I can adjust the speed of the wheels easily and in theory infinitely
mohs
|
|
|
Post by mohs on Mar 9, 2013 23:44:20 GMT -5
I should probably re-state that
A one to one ratio in example: two 2" pulleys is probably a fine speed for 6" wheels
That's how the Lortone cabber is originally set up with 1750 motor
I like to slow down the wheels particularly when when I buff
Ed
|
|
|
Post by jakesrocks on Mar 10, 2013 1:21:32 GMT -5
|
|
|
Post by jakesrocks on Mar 10, 2013 11:47:59 GMT -5
In case you have never seen a variable sheave, (pulley), Here are some pics. Back side. 2halves apart. Detail showing threads This is a Congress Drives # VP-325-73. It's a 1-1/2" to 3" variable. It works by simply loosening 1 set screw and turning the outer half in or out 1/2 turn at a time. If mounted on the motor, by turning the outer piece counter clockwise it will reduce the final speed at your arbor. By turning clockwise it will increase your final speed. If mounted on your arbor, it works just the opposite. Variable sheaves are more expensive than regular pulleys, but well worth the investment. They give the advantage of very small changes in speed by only moving the outer half 1/2 turn at a time. Just loosen 1 set screw, adjust your speed and re tighten the set screw. Much quicker than removing a pulley and replacing it with a different size. One variable sheave does the job of a whole box full of different sized pulleys.
|
|
|
Post by mohs on Mar 10, 2013 14:51:46 GMT -5
The variable speed sheave link are a bit pricey ! but well worth it
How much did you pay for variable speed sheave, Don?
Ed
|
|
|
Post by jakesrocks on Mar 10, 2013 15:36:34 GMT -5
Mine was a gift from one of our members for turning him on to the idea of using one on a piece of equipment he was building. Just waiting for the big reciprocating flat lap I want to build this summer.
|
|
Deleted
Deleted Member
Member since January 1970
Posts: 0
|
Post by Deleted on Mar 10, 2013 17:26:31 GMT -5
|
|
|
Post by jakesrocks on Mar 10, 2013 17:45:39 GMT -5
Wow Dave, that's a damned good price. And they take paypal too. I might have to order a couple just to have them around.
|
|
|
Post by jakesrocks on Mar 10, 2013 22:11:06 GMT -5
Hey Dave, I ordered 2 of those. Free shipping on them is a +. Just checked my order. They're the same as the pics I posted. Congress VP-325's
|
|
|
Post by mohs on Mar 10, 2013 22:12:41 GMT -5
|
|
|
Post by jakesrocks on Mar 10, 2013 22:41:13 GMT -5
LOL, yep, I remember that discussion. Man, that was a while back.
Don
|
|
|
Post by mohs on Mar 10, 2013 23:21:45 GMT -5
yeppers Don-- that was a lot of rock'n hearts ago.... mohstly
|
|
|
Post by johnjsgems on Mar 14, 2013 9:21:28 GMT -5
When I did HVAC work whenever we replaced a motor we had to replace the motor sheave also. Even if it was replaced recently. Guess who has a box of good salvaged adjustable sheaves in his garage? They come in very handy when refurbing used equipment. DP and Covington catalogs both have pulley charts for easy pulley speeds.
|
|