Expando drum issue

[Taogem]

and the ends need to be sanded flat and square.


Gary

I just wanted to highlight Gary's comment about the spacers being square.. Very important.. So just make sure that where you cut your pipe material of choice, that it is exactly 90 degrees to the length.. Otherwise your drums will wobble.. You are going to have a heck of a time cutting them square by hand without some type of guide.. Maybe your hardware store has a nice little cut off saw that has an degree adjustment..

All the motors I have had seem to have a bolt down plate with slots instead of just a hole for the bolts.. If yours does, then you can slide your motor a bit one way or the other.

Know what I mean ?

As far as the pulleys.. Guess I would recommend two of the 2 1/2" pulleys.. That is 2 1/2 on the inside or where the inner part of your belt rides. Not the very outer part of the pulley..  I think that is how the hardware store measures them any way...

[bobby1]

Most industrial bearing supply vendors carry pulleys (sheaves in their parlance) and belts, also.
I run my cabbing unit at about 1475 rpm so that the expando drum runs slower thus they are softer. I like it that way because the additional flexibility of the surface allows me to do a better job sanding out mini flat spots and scratches.
Bob

[redrockrods]

Using a caliper, I measured the diameter pulley on the motor at 2". Note that I"m measuring from edge to edge.



The pulley on the arbor measures out at 4"



The motor mount plate does have a little room for adjustments at the bolt holes, but it doesn't look like a lot of space. maybe 1/2" or so play is available.

Regarding the spacers, George, I just found out how hard it is to make a square cut by hand! I'm going to have to make do with the old ones for now.

[Bluesssman]

What length of spacers and how many do you need?


Gary

[Taogem]

I am guessing that your pulleys are 1 1/2" and 3 1/2".. That is the inner diameters.. At 1725 motor rpm I believe your expando's are presently running at 739 rpm..

I spent hours trying to do my first spacers by hand.. Finally had enough and gave up ! 

[akansan]

I had a spare pulley here still in the box so I thought I'd double check where the part is measured at.  It's measured from edge to edge of the actual pulley, not where the belt rests.

The pulley I have is a 3 1/2" x 5/8", and you're welcome to it if you'd like.  That would get you up to 1509 rpms.

[Taogem]

It's measured from edge to edge of the actual pulley, not where the belt rests.

Thanks for correcting me Rhonda 

[redrockrods]

I had a spare pulley here still in the box so I thought I'd double check where the part is measured at.  It's measured from edge to edge of the actual pulley, not where the belt rests.

The pulley I have is a 3 1/2" x 5/8", and you're welcome to it if you'd like.  That would get you up to 1509 rpms.

I'll take it! many thanks! I will PM you my info.

[Old Hickory]

I had the same problem with the 3M Aluminum Oxide - Trizact  belts and the 3M Aluminum Oxide - Microfinishing Film  belts. They do seem to be somewhat larger in diameter. My solution to this problem was to increase the size of the expanding drum. I went to MAPA auto parts and got some 1/32” or (.0312") thick sheet gasket material. I then cut it in 3” strips to go around the expanding drum. Cut it so that it wraps around drum tight with no gap where the ends come together. This takes a little time but it can be done, note - cut this material with a exacto knife or something similar. Cutting with scissors seems to leave a raised edge at the cut. After carefully fitting and cutting your gasket band, wrap it around drum and tape it together with a small piece of masking tape it should fit tight around the drum. The tape just holds it tight around the drum until you put your belt on. The belts will slide on and off with little effort and you are good to go. If the band has been cut to the correct length and the end cuts are good and square you will not notice the joint when you are grinding. The gasket thickness has increased your drum a mere 1/16” or (.0625“) and the centrifugal force will keep everything in place. Have been using this method for the last two years with no problems.

[Bluesssman]

Redrockrods, if you give my exactly what size and how many spacers you need, I will lath some out of pvc for you if you are interested.


Gary

[redrockrods]

Hi Gary, I'll take some measurements and get back to you on the spacers.  Thanks!

[Taogem]

Cut it so that it wraps around drum tight with no gap where the ends come together. This takes a little time but it can be done, note - cut this material with a exacto knife or something similar. Cutting with scissors seems to leave a raised edge at the cut. After carefully fitting and cutting your gasket band, wrap it around drum and tape it together with a small piece of masking tape it should fit tight around the drum. The tape just holds it tight around the drum until you put your belt on.

I am just a bit confused and would like to try this Ron..

If I initially cut it tight to the drum and tape the ends together, how is the drums expando/centrifugal force able to work?

[Old Hickory]

George, if the band is cut correctly for a tight fit around the drum the tape is just used to hold the band together on the drum until the belt is installed on the drum. I used the blue low tack painters tape and just put one small piece across the joint just to hold it together on the drum.

After you have installed the band around the drum you have taken up most of the extra space between the drum outside diameter and the belt inside diameter, (that extra space allows your belt to slip on the drum.) With the low tack tape when the drum comes up to speed the tape will slip enough to let centrifugal force do its thing.

Actually of late I have just been putting the band inside the belt ID then slide the belt / band combination onto the drum as one piece. Just make sure that the band joint is on the opposite side of the belt from the belt joint.






Now this workaround all depends on how much space you have between your drum OD and your belt ID. You may have to change the gasket thickness for you spacific conditions. The 1/32" thick gasket material worked out well for me.

[Taogem]

Actually of late I have just been putting the band inside the belt ID then slide the belt / band combination onto the drum as one piece. Just make sure that the band joint is on the opposite side of the belt from the belt joint.

This seems like a good way.. Will give this a try as I do have plenty of room on the ones that are giving me the problem.. So odd that some fit loose, some fit just right and some belts I have to actually work on to the drum because they fit so tight !

Any way, thanks very much for this tip and pics.. Greatly appreciated and will let ya know how I make out..