Flat Belt Drives

Anyone here familliar with flat belt drives? I have an old-style floor
drill press that uses a flat belt to drive the pulley on the upper
cross shaft from the lower one and I want to put it back into running
condition. The belt has a tendency to slip under load and so I added an
adjustable idler near the lower driving pulley, on the side of the belt
that goes down as it is running, but now the belt wants to slip
sideways off the lower pulley when the idler is on. The belt tracks ok
when the idler is not in contact and I tried shimming first one side of
the idler shaft and then the other, thinking the alignement was off,
but this only seemed to make things worse. The idler shaft is paralell
to, and level with, the driving and driven shafts so far as I can tell.
Does it matter which side of the belt the idler is on? The original
belt was missing so I used one made from what looks like black rubber,
1 3/4" wide and 1/4" thick, and running at about 300 rpm. So maybe
rubber is not suitable for this application? Any advice appreciated.
Mike
Reply to
mdmart
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Yes there are , can't wait to hear the responses. I've debated with myself over trying to do what you've tried . I put some kind of fabric and rubberized belt on mine and it could be just a little shorter. But, will it stretch back to the tightness as I have now after a couple of hours? I'm sure it will stop at some point after I run out of alligator parts. It works good enough when I put the tar type stick on the belt. I would guess that the crowned idler should be on the inside.
Reply to
Sunworshipper
Did you try dressing? I don't like the idea of an idler but I don't know why. I don't like the idea of rubber. is it stretchy? Can you get a leather or plastic belt?
Reply to
Tom Gardner
Wow! Flat belt drives.....boy does that bring back some old memories. I once worked (early 70's) at a farm machinery manufacturer in So. Idaho and they had three machines (lathes) that were flat belt drive machines (babbitt bearings too ). They had a main shaft, overhead drive unit that ran all three machines. I don't remember exactly how it worked because I tried to stay away from those machines as much as I could. Hmmmm, I wonder if there are any shops that still use .......? No! Couldn't be!
John
Reply to
John
As late as 1975, there was a machine shop in Venice, California, that ran almost all the machines in the shop via belt drives off a great big electric motor that sat outside the building in its own little shed. A shaft came in the wall and distributed power to at least three shafts, spaced along the ceiling, that ran all the way from one side of the shop to the other. Wherever there was a machine, there was a flat pulley on one of the overhead shafts, and a leather belt and idler pulley with a cam-over lever arm to engage the machine. I used to drop by there from time to time just to watch the whole thing run.
A year or two later, the owner had retired and sold the shop, the new owner had torn the building down, and God only knows what happened to all that lovely machinery.
Tom Dacon
Reply to
Tom Dacon
The idler is not crowned. It more resembles a long aluminum rolling pin about 3 5/8" o.d. I considered putting it on the inside of the belt but it seemed that it would give more contact area on the driven pulley if it was outside, however, I don't know if it would be better to have it on the left outside or right outside of the driven pulley. Mike
Reply to
mdmart
The idler is not crowned, it more resembles a long aluminum rolling pin about 3 5/8" O.D. I considered putting it on the inside of the belt but it seemed that it would give more contact with the driving pulley on the outside, however I don't know if it would be better to have it on the right outside or left outside of the driving pulley. Mike
Reply to
KyMike
The idler is not crowned, it more resembles a long aluminum rolling pin about 3 5/8" O.D. I considered putting it on the inside of the belt but it seemed that it would give more contact with the driving pulley on the outside, however I don't know if it would be better to have it on the right outside or left outside of the driving pulley. Mike
Reply to
KyMike
The rubber is stretchy and seems slippery on the surface, though I thought if I could get it tight enough it would do for now until I can find something better. I have not tried dressing because I'm not sure what to use on rubber belts or if it would only make things worse. Mike
Reply to
KyMike
The rubber is stretchy and seems slippery on the surface, though I thought if I could get it tight enough it would do for now until I can find something better. I have not tried dressing because I'm not sure what to use on rubber belts or if it would only make things worse. Mike
Reply to
KyMike
The rubber is stretchy and seems slippery on the surface, though I thought if I could get it tight enough it would do for now until I can find something better. I have not tried dressing because I'm not sure what to use on rubber belts or if it would only make things worse, but its an idea. Mike
Reply to
KyMike
Mike,
You don't need an idler. You need to get the right type of belting. I recommend what they call flat transmission belting. You can get it from MCMaster-Carr.
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It's less then a buck a foot. The bigger cost is getting a clipper lacing tool, or you could use alligator lacing. The trick is trying to figure out the right length. I normally rap the belt around the pulleys and pull it tight. I mark the length on the belt, and then subtract out the length of the clipper lacing, then I subtract out another .5" to 1" and cut the belt. If it is to lose, then cut off just the clipper lacing from one end and try again.
If the tension is right, then you don't need any dressing.
Vince
snipped-for-privacy@netzero.net wrote:
Reply to
Vince Iorio
You just need belt dressing... The stick form was the best... No one sells it anymore...
Reply to
kbeitz
My SWAG is that if the idler is close to the pulley it will interfere with the crown action, try putting the idler far away from either crowned pulley.
Reply to
Nick Hull
Thanks for the replies everyone. Mike
Reply to
KyMike
flat belts don't you just love them. use them on conveyers at work make sure you are getting at least 50% contact on pulley and you should not have any slip, if using idler move away from the driving pulley. The more contact you have on the driven pulley the better should stop the slipping Troy L Gilbert
Reply to
Wolfcrow Warrior
Having way too much flat belt machinery to keep running, The first thing I will say is that the call for the proper power transmission belt is dead on. Conveyer won't work. Leather is best, with the rubberized woven a close second. I don't recommend belt stickem. The rub-sticks work well, and, for leather, neats foot oil. Not soaked, just pliable. If you use too much dressing, the belts end up damaged, slip worse, track poorly, or all of the above.
Idlers generally don't do any good in the long run.
First thing to find is the adjuster for center-to-center distance. On a drill press, it should be the lower shaft. Ideally, there will be about 1" or more of travel, for a belt length change of 2" or more. If there is no way to adjust, it is MUCH more difficult to keep the belt running right.
Shorten up the distance as much as possible, check the shafts for parallel and the pulleys are aligned (biggest problem with tracking, a belt with bend or twist being second) If not parallel with the pulleys in line, adjust them. You CAN NOT get proper tracking or good belt life with mis-aligned pulleys. Use a tape to get the total length of belt needed. Get the right belt. Get extra.
Before installing, claen the pulleys. Now, cean them well. Now, clean them again. No oil, dressing residue, grease, stickem, or other contaminants.
When you make up the belt, make it about 6" short, and make up a 6" splice. Install with the splice. You might as well make up a 4" and a 2" as well... you'll need them as the belt stretches. Draw up the belt tension. How much? Depends on the setup. Under load, the slack side really can go slack, so no more tension than needed to keep the slack side from being too slack at maximum load. Most of mine run and track well with just enough tension not to slip by hand. The belt really tightens under load. If the slack side is flopping too much, tighten. It will flop some.
Now, check it... Roll over by hand. Track ok? Bump the motor. Track ok? Everything turn ok? Run in for a minute or two. Check the adjustment. As the belt stretches, take up as needed at the bottom shaft. When you run out of adjustment, remove the 6" patch, and put in the 4". Etc. Dress the belt regularly with the proper dressing, but not too much.
I'm down to about 5 large belt driven machines at this point (48"X20 foot lathe, 56"X12 foot lathe, a couple of drill presses, and a small lathe), but they all run fine. The longest belt is just under 30 feet, vertical, 15HP drive, coming off the reversing clutch-pulley on an overhead countershaft to drive a lathe. The smallest is 3/4" wide, about 20", and is the power feed for a good size drill press. All are joined with belt staples.
If possible, gaurd the belt. Even a couple bars on each side to catch it when it breaks will do, but a cage is better. The belt is heavy, and when it goes, it can do real damage.
snipped-for-privacy@netzero.net wrote:
paralell
rubber,
Reply to
enl_public
That is exactly the problem I'm having with it, the designers did not provide a way to adjust the upper and lower shaft spacing, though it might be possible to do this by mounting the lower pulley shaft on some sort of pivoting arm. This drill press came out of a 100 year old shop and you would think that even back then they would have known that belts stretch over time. I'm pretty sure the shafts are in line because the belt tracks all right without the idler, but it looks like I don't have the right type belt. Thanks for the info. Mike
Reply to
KyMike
Well, there may be a way (one on mine is shimmed under the mounts for the shaft) but the easiest is to lace the belt rather than use staples. You can snug up lacing as the belt stretches.
KyMike wrote:
because
Reply to
enl_public

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