keeping V belts on

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  • seafox
    Senior Member
    • Feb 2001
    • 1700

    keeping V belts on

    I've been building a fire wood cut off saw and since puitting a 10 inch pully on the engine ( with a 10 inch and then 11 inch pully on the driven shaft) have had a very hard time keeping the belt on the wheels. the newst one breaking I think because it caught between the pullys and a guide pully and broke with out much wear. also I have tensioned the belt by hanging the 65 pound engine on it.

    is it wrong to have the drive and driven pullys about the same size? is it because using 10 inch pullys the belt speed is fast ( 31 inch dia times 3000 rpm ~= 7000 feet per minute.

    is the wngine weight to much tension on the belt? the engine is a 6 horse power

    thankyou for your help and veiws
    jeff
    Last edited by seafox; 09-30-2009, 12:16 PM. Reason: mispelling if you can belive it ( grin)
  • Hwyl
    Gareth
    • Jan 2003
    • 22222

    #2
    Re: keeping V belts on

    Nice to see you Jeff.

    My guess is there's too much vibration in the engine and a fixed tension would be better, but it's only a guess.

    Comment

    • seafox
      Senior Member
      • Feb 2001
      • 1700

      #3
      Re: keeping V belts on

      thankyou. its been a good working summer with my x uncle in laws landscaping company todays it raining a lot so till it quits its a day off

      Comment

      • Keith Wilson
        Trying to be reasonable
        • Oct 1999
        • 64114

        #4
        Re: keeping V belts on

        What size v-belt (cross-section)? Distance between pulleys?
        "For a successful technology, reality must take precedence over public relations,
        for nature cannot be fooled."

        Richard Feynman

        Comment

        • seafox
          Senior Member
          • Feb 2001
          • 1700

          #5
          Re: keeping V belts on

          earler I had a 3 inch pully on the engine and the belt stayed on fine only at 1000 rpm the say didn't cut to fast and also boged down. am thinking of fixing the engine and direct coupling it to the shaft ( with a simi flexable coupling

          Comment

          • botebum
            Banned
            • Sep 2002
            • 12018

            #6
            Re: keeping V belts on

            I'm no mechanic but there are only a few things that I know of that could cause it.
            Pulley allignment
            Belt tension
            and wrong belt or pulley.
            If the belt is wearing badly and then jumping off or breaking I'd guess the pulley allignment is off.
            (This advice is worth exactly what you paid for it)

            Doug

            Comment

            • seafox
              Senior Member
              • Feb 2001
              • 1700

              #7
              Re: keeping V belts on

              its half inch size V belt ( belive its called A size ) total length of the belts have been 57 and 60 inch I would put pully distance shaft to shaft at 16 inches and have put a small idler pully before each drive and driven pully outside the belt to try and keep from jumping off

              Comment

              • oznabrag
                Historical Illiterate
                • Nov 2008
                • 40762

                #8
                Re: keeping V belts on

                Sounds to me as though you may want to have a B belt, for one thing.

                As others have mentioned, a 65 pound engine bouncing around on your belt can't be a good thing, and yes, alignment is pretty critical.

                Also, your intuition on the belt speed is probably correct, and it seems odd that a firewood cut-off saw with 6 horse would do a lot of bogging down.

                The major question, however, is 'Do you have pictures?'
                Rattling the teacups.

                Comment

                • pila
                  Senior Member
                  • Apr 2008
                  • 1146

                  #9
                  Re: keeping V belts on

                  Why not have two smaller pulleys the same size? the belt speed would be lower for the same RPM. Just a thought.......

                  Comment

                  • Syed
                    Member
                    • Oct 2006
                    • 5607

                    #10
                    Re: keeping V belts on

                    Originally posted by seafox
                    earler I had a 3 inch pully on the engine and the belt stayed on fine only at 1000 rpm the say didn't cut to fast and also boged down. am thinking of fixing the engine and direct coupling it to the shaft ( with a simi flexable coupling
                    I suspect the problem is due to increased load on the belt. You may have to go for multiple belts say about three belts or at least two with multi-groove pulleys.

                    Comment

                    • Stiletto
                      Grant S
                      • Jan 2003
                      • 11234

                      #11
                      Re: keeping V belts on

                      What Pila says makes sense, It may also be a belt size/pulley size compatibility issue. Make sure the belt isnt bottoming out in the pulley.

                      Can you run a straightedge across the two pulleys to check alignment?
                      There is nothing quite as permanent as a good temporary repair.

                      Comment

                      • Bob (oh, THAT Bob)
                        I fix stuff.
                        • Feb 2007
                        • 10222

                        #12
                        Re: keeping V belts on

                        I also need to see pictures. My first thought, after pulley alignment (both should be in the same plane), is that the reaction torque from the saw as it cuts may be increasing or decreasing the belt tension, and/or causing oscillations. And the geometry can get weird. As an example of non-obvious thrust and torque situations: Picture the front steering knuckle and tire on a front-wheel-drive car. Under braking, the reaction thrust (aft) is resolved at ground level, where the tire meets the road, causing the front suspension to try to rotate forward. That is because the brake caliper and rotor act as a link between the wheel and knuckle. But, under acceleration, with no brakes, the reaction thrust (forward) is at *wheel center* (most folks think at the ground), because, with a ball bearing between the axle shaft and knuckle, torque cannot be transmitted between the tire ground patch and the knuckle, only radial thrust at the knuckle. Perhaps doesn't apply in this case. Post pics, we'll look at the geometry. Kinematics is my strong suit.
                        Last edited by Bob (oh, THAT Bob); 09-30-2009, 10:02 PM.
                        sigpic When you can take the pebble from my hand, it will be time for you to leave.

                        Comment

                        • oznabrag
                          Historical Illiterate
                          • Nov 2008
                          • 40762

                          #13
                          Re: keeping V belts on

                          Yeah! What Bob said!
                          Rattling the teacups.

                          Comment

                          • Canoeyawl
                            .
                            • Jun 2003
                            • 37698

                            #14
                            Re: keeping V belts on

                            A half-inch belt is considered a fractional horsepower belt...

                            Comment

                            • P.I. Stazzer-Newt
                              obnoxiously persistent.
                              • Jan 2005
                              • 26001

                              #15
                              Re: keeping V belts on

                              Does anyone else think that 7,000 fpm is seriously quick?

                              I'm not familiar with biggish circular saws, but wood cutting bandsaws often run about the 2,000 fpm mark.
                              I'd much rather lay in my bunk all freakin day lookin at Youtube videos .

                              Comment

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