I'm trying to put one together to aid in my finish sanding. My only experience with a belt sander is one that runs WAY too fast. It's my little GMC from Lowe's and it runs at around 4000 rpms (that's the disc speed on the belt/disc combo). A motor I'm thinking about using to start my project runs (at it's slowest) at 2000 rpm's. That's half the speed of what I'm used to and I'm not sure that it's slow enough. What do you guys who have these things think of the speed?
If I'm not being clear on what I'm talking about (I *DID* just have a glass of wine you know) than here is an example of what I hope I end up with:
This is Rainer Barbi using one:
http://www.pipes.com.tw/Photo/Barbi_2004/14.jpg.html
people with large belt sanders for finish sanding
-
alexanderfrese
- Posts: 317
- Joined: Thu Nov 23, 2006 8:00 pm
- Location: Bochum, Germany
- Contact:
Besides all that rpm values, on a belt sander like that, the speed of the belt ist much more interesting. It should be some m/s or inch/sec, or whatever dimension. The rpm on a disk or a sanding drum can be calculated into some angular speed of the medium on the outside of the drum or at any given radius of a sanding disc. This value can be compared to a plain old distance by time speed for the belt.
The speed of the belt will be determined by the radius of the cylinder on the motor axis, the belt is driven from. If a cyl with a circumference about 10cm is driven by a 4000 rpm motor, the belt will have a resulting speed of about 6.7 m/sec. This seems pretty speedy for me and – the diameter of the driving axis cyl would only be about 3.6 cm. Depending on the whole setup, that might be too flimsy. To reduce the speed of the belt, an even smaller diameter would be necessary. To get to half the speed with the same motor, you would need a cyl with a diameter of only about 2.5cm.
With a 2000 rpm motor, the belt speed would be bisected when using the same "driving cyl" diameters.
Please feel free to flame me, if I mixed up some of that High scool formulas in the forgotten back rooms of my memories and came up with wrong values.
Maybe those belt speeds are not out of range for our purposes? Maybe those cyl diameters can hold and drive typical belt dimensions? Everyone using a similar equipment, please step in.
I just wanted to add a little thought about the idea, that (within some range) the given motor rpm might be not that important. I just had that vision of those old school transmission belt powered work shops, where all power came from one "motor", and everything else is handled by those diameters mentioned.
The speed of the belt will be determined by the radius of the cylinder on the motor axis, the belt is driven from. If a cyl with a circumference about 10cm is driven by a 4000 rpm motor, the belt will have a resulting speed of about 6.7 m/sec. This seems pretty speedy for me and – the diameter of the driving axis cyl would only be about 3.6 cm. Depending on the whole setup, that might be too flimsy. To reduce the speed of the belt, an even smaller diameter would be necessary. To get to half the speed with the same motor, you would need a cyl with a diameter of only about 2.5cm.
With a 2000 rpm motor, the belt speed would be bisected when using the same "driving cyl" diameters.
Please feel free to flame me, if I mixed up some of that High scool formulas in the forgotten back rooms of my memories and came up with wrong values.
Maybe those belt speeds are not out of range for our purposes? Maybe those cyl diameters can hold and drive typical belt dimensions? Everyone using a similar equipment, please step in.
I just wanted to add a little thought about the idea, that (within some range) the given motor rpm might be not that important. I just had that vision of those old school transmission belt powered work shops, where all power came from one "motor", and everything else is handled by those diameters mentioned.
Alexander Frese
www.quarum.de
www.quarum.de
I understand the idea of using different diameters to reduce increase the speed of the belt, I just wasn't sure if 2000 RPM's was something that was do-able considering what I'm trying to achieve. In other words, I don't want to have go to the ends of the earth finding parts just because I had a motor that was too fast.
I just used RPM's because that's all that the grinder has measurement for. My belt sander has a ft. per second measurement (can't remember what it is) but the same motor drives the sanding disc so I was just comparing apples to apples for the speed.
I just used RPM's because that's all that the grinder has measurement for. My belt sander has a ft. per second measurement (can't remember what it is) but the same motor drives the sanding disc so I was just comparing apples to apples for the speed.
-
alexanderfrese
- Posts: 317
- Joined: Thu Nov 23, 2006 8:00 pm
- Location: Bochum, Germany
- Contact:
Ben, besides all that smart talk, there still should be someone able to say: »My belt sander's belt runs at such and such ft per whatever timeslice.« This would be the only really help.
I surely did not only want to look good with that very basic physic formulas…
I surely did not only want to look good with that very basic physic formulas…
Alexander Frese
www.quarum.de
www.quarum.de
-
NvilleDave
- Posts: 254
- Joined: Thu Nov 23, 2006 8:00 pm
- Location: United States/Tennessee
- Contact:
Ben,
I have a belt sander that uses 72" belts. I'm using one of those baldor motors that was on Ebay--it runs at 1725 RPM--I have a 2" pulley on the motor and a 3" pulley on the pillow block--I think the pulley belt is 48" long. The sanding belt rides on a 10" wheel (approx). I have no idea what RPM or ft per minute it is running--I'm happy with it--it works really well but I do wish I could vary the motor speed with some kind of controller.
I didn't answer the post earlier because I don't know the specific RPM it's running at. Sorry I can't help anymore.
Dave
I have a belt sander that uses 72" belts. I'm using one of those baldor motors that was on Ebay--it runs at 1725 RPM--I have a 2" pulley on the motor and a 3" pulley on the pillow block--I think the pulley belt is 48" long. The sanding belt rides on a 10" wheel (approx). I have no idea what RPM or ft per minute it is running--I'm happy with it--it works really well but I do wish I could vary the motor speed with some kind of controller.
I didn't answer the post earlier because I don't know the specific RPM it's running at. Sorry I can't help anymore.
Dave
-
alexanderfrese
- Posts: 317
- Joined: Thu Nov 23, 2006 8:00 pm
- Location: Bochum, Germany
- Contact:
Dave, I don't know what is the usual way to name a pulley’s or a wheel’s dimensions in you language. If you say 2", is it diameter, radius or (hardly possible) circumference?
If we have that fact, we could calculate the resulting speed of the sanding belt.
And just to get you right:
The motor runs the 2" pulley on it's axis, which transfers the rotation to the 3" pulley on another axis by a drive belt?
And that second axis is the one, that the 10" wheel is running on, too?
Besides the variable motor speeds, if you put some smaller and/or bigger pulleys besides that 3" one on that second axis, you’d have a simple gear similar to all those belt driven lathes.
:think:
If we have that fact, we could calculate the resulting speed of the sanding belt.
And just to get you right:
The motor runs the 2" pulley on it's axis, which transfers the rotation to the 3" pulley on another axis by a drive belt?
And that second axis is the one, that the 10" wheel is running on, too?
Besides the variable motor speeds, if you put some smaller and/or bigger pulleys besides that 3" one on that second axis, you’d have a simple gear similar to all those belt driven lathes.
:think:
Alexander Frese
www.quarum.de
www.quarum.de