Announcement

Collapse
No announcement yet.

Flat Leather Belts

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Old Hat
    replied
    Originally posted by Ohio Mike View Post
    If the pulleys are clean, and they should be, your belt is probably to loose. No paint or other gunk should be on them, clean them with mineral spirits if need be. You should never ever have to dress a leather belt with magic potions of any kind. If a belt needs cleaned then use an application of neatsfoot oil with a clean rag. Be sure to run the smooth side on the pulley it will grip better, and the belt tension should be released when the machine is not in use.

    Mike
    This advice matches perfectly with the directions I recieved in 1975, from my first expoxure to a planer
    and a Man who new what he was doing, and what he was taking about.

    Leave a comment:


  • J Tiers
    replied
    Originally posted by kendall View Post
    Wow, Jtiers, where were you when I was first experimenting with belts?
    Messing with mine, and reading up on them.....

    As for the tension needed, that depends on the pull required. Larger diameter pulleys require less, leverage (torque per lb of pull) is better, and the belt speed is higher.

    if the static tension is half the pull required, then at max pull, the tight side just gets to double the static tension, and the slack side just goes to zero.... (ignoring stretch).
    Last edited by J Tiers; 08-27-2014, 08:09 AM.

    Leave a comment:


  • kendall
    replied
    Wow, Jtiers, where were you when I was first experimenting with belts?

    Leave a comment:


  • J Tiers
    replied
    Power passed through a leather belt depends on a number of things.... In no particular order....

    1) width. more width means more friction surface, and also more ability to carry a load (pull on the belt) without breakage.

    2) belt speed. Speed is good, because the pull capability before slippage is limited.

    3) thickness, usually "number of plies", or layers. More means higher static tension capability per inch of width.

    4) Static tension. More static tension means less slippage at any given "pull".

    5) belt wrap... a large difference between pulley diameters, especially at a short belt length, means one does not have much "wrap", and so it won't carry as much load.


    The belt slips when the "creep" reaches all the way around the belt "wrap". When the belt is pulling on a "pulley", no matter if driven or driver, the belt is stretched on the tight side, and loose, contracted on the loose side.

    Somewhere between those, the belt stretches from the loose condition to the tight condition. It changes length, what was one inch on the loose side becomes longer on the tight side. The squeaking of that slippage is the belt "talking" under load, caused by the rubbing of the belt against the pulley as it moves.

    The belt "adheres to" the pulley.... a slick rubber belt shows this well, leather also does it, and the slicker the leather, and the more polished the pulley, the better they adhere. Sounds odd, but it works. It's like your very slightly damp hand on a dry polished metal pole.... it can stick so it nearly rips your skin off.

    If your pulleys are rough, they may not take much pull, unless they are so rough as to be almost "cogged" , so they dig into the belt.... That may take pull, but it isn't good for the belt.

    because the pulley is a fixed rigid size, and the belt is stretching, with a light load, the belt starts to slip just before it reaches the point where it "unwraps from" the pulley. Since there is zero force holding it against the pulley at the point of unwrapping, there is zero friction. Somewhere back of that point there is a little more, and the belt is still taking some tension. And somewhere all the tension is taken up and the pulley is gripping.

    The more "pull", the more that point of stretch tends to move around the pulley toward the slack side. So long as it does not reach the slack side, it does not slip. The stretch slippage may not necessarily reduce the "pull", the belt can still grip even though it is slipping, like snubbing a rope.... so long as some part is not slipping, all is well.

    The amount of friction depends on the width of belt... more width is more area, plus the ability to be put under more tension, so the tension per inch of width adds up across the width. If it will take 35 lb per inch, then 2 inches takes 70 lb, and 3 inches takes 105lb, etc.

    When you add more tension to the same width, the force down against the pulley is more, and the friction is more... like stepping on the brakes harder. So adding thickness adds strength and allows higher tension, allowing more pull per inch of width.

    No idea what your problem is.... do you have photos of the setup?

    Belt dressing is not always the solution, it's never the RIGHT solution, but it can help. It can cover up problems. But it is better to solve the problems.

    Leave a comment:


  • Ohio Mike
    replied
    If the pulleys are clean, and they should be, your belt is probably to loose. No paint or other gunk should be on them, clean them with mineral spirits if need be. You should never ever have to dress a leather belt with magic potions of any kind. If a belt needs cleaned then use an application of neatsfoot oil with a clean rag. Be sure to run the smooth side on the pulley it will grip better, and the belt tension should be released when the machine is not in use.

    Mike

    Leave a comment:


  • Mcostello
    replied
    Hit the local KFC for some honey as when it dries it turns black and adheres to the pulleys very well.

    Leave a comment:


  • Crane
    replied
    Thanks to all for your help. Rosco I will try the web sight you suggested. This is going to be an historic repro line shop so anything other then leather is a no no. wish us luck
    Don N.

    Leave a comment:


  • Charles Spencer
    replied
    I don't know but I'll bet Hudson Belt (since 1854) can probably tell you:

    http://www.mindravegroup.com/hudsonbelting/index.html

    Leave a comment:


  • Rosco-P
    replied
    Expertise on flat belts and line shaft run shops exists elsewhere. Try the Antique Machinery subform over at Pracical Machinist.

    Leave a comment:


  • Paul Alciatore
    replied
    It IS a friction drive and there is just so much you can do with a given pulley and belt size. Belt dressing? Yes, it helps. More tension? That may also help. But there are limits.

    You can try other belt materials. They can help also.

    http://www.mcmaster.com/#flat-drive-belts/=tfveek

    I have run both leather and automotive style serpentine belts on my SB-9 and the serpentine belt is far superior. It transmits more power and slips less. I had to increase the tension to get it to track properly and I do not use any dressing with it as I did with the leather belt.

    If you stick with leather, do use the belt dressing. You can slowly increase the tension and observe the results as you do. I would not go too far or too fast in these increases as a leather belt will stretch to find it's own tension and if you go too far, it may break. If you observe that the tension decreases with some usage after increasing the tension, then further increases will be in vain and will probably weaken the belt if carried too far.

    At some point after trying all of the above, if you can not get enough power due to slippage, you are going to have to consider wider belts and pulleys or a different drive system.

    Leave a comment:


  • Mcostello
    replied
    As long as the belt is just tight enough to pull the expected load, thats all it needs. More tension means less splice or belt life.

    Leave a comment:


  • flylo
    replied
    I can't answer the question but welcome to the worlds best machining forum

    Leave a comment:


  • Crane
    started a topic Flat Leather Belts

    Flat Leather Belts

    A friend is setting up a line shop. At present he has most of the over head shafting and pulleys in and one machine (drill press) is belted to the line shaft. The drive belt for the line shaft to the drill press seems to be driving fine. The problem was the belt driving the spindle. It is slipping. It's a new belt without any dressing. We did a little research and came up with a belt dressing which will be applied ASAP.
    My question is there a rule of thumb for checking the tension on flat leather belts? I know with V belts putting a straight edge across the pulleys and flexing the belt you can judge how tight or loose the belt is. Is there something like this for flat belts?
    Thanks
    Don N
Working...
X