No announcement yet.

truck generator

  • Filter
  • Time
  • Show
Clear All
new posts

  • truck generator

    Here is one for the youngsters. A buddy of mine is rebuilding a 1947 chev truck. He has switched over the 6 volt system to a 12 volt. NOw his altenator pulley is too small for the belts to fit in. The angles of these old belts differ from the new ones, 72آ؛. Any idea what the angle of these old belts are?

    Thanks in advance

  • #2
    No. Change the whole thing over to flat belt - they do not suck like v-belts.


    • #3
      Machineries says 34 degrees for vee belts from 3-4 inches.

      Easy way is to use the old generator pulley, sometimes some modification has to be done, sleeve made, width reduced or such.

      Want to have fun, tuck a Delcotron under the hood of an H Farmall, it can be done.

      Good luck, have fun.


      • #4
        A delcotron? My dad has a farmall A. Nice tractor. Awesome you figure it has no water pump. Just convection currents keep the thing cool.


        Flat belts like on the new trucks? Serpentine style. Aka with the grooves?

        Spkrman 15


        • #5

          10-4 rubber duck! Serpintine belts can eat rocks and just laugh at them. Long live Kevlar!


          • #6
            Thrud,have you ever used those serpentine belts for light lifting slings? They also work pretty good for flat drive belts.


            • #7
              Hey guys I've posted this before but it comes under this thread so I'll do a reminder.
              The multi groove belts are known among other titles as Poly V belts.
              Good web page at
              The most popular size of low power use is the J series.
              I found out by accident that the 11 tpi.dies from a coventry die head are very, very close to the correct size and pitch for a J series pulley.
              OK purist's will argue the angle isn't quite correct but I've been making small pullies for some years that run up to 9,000 revs and keep that over a 10 hour working day on woodworking machines.
              Pic of a 2" pully being machined:-

              There has been a commercial design published where the 3 step Vee pullies on a Myford have been replaced with a 4 step poly V drive.
              This gives smoother and more power for the size of belt.
              If I was doing the same design today I'd probably go for a two step with as big a gap as possible between the two and use a VFD to control speeds in these two ranges.
              Without working anything out you could probably do away with the backgear using this method.
              Twin belts, countershaft pullies on bearings, sliding dog clutch and you could even do away with not ever having to change belts.
              Also adaptable to SB's Atlas etc.

              John S.

              John S.

              Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.


              • #8

                No, I can't say I have done that, but I see they are marketing strap wrenches with those belts now. I may have to convert my Ridgid strap wrench that I lossen my chucks with (they are all scraped to fit really well - but they are a S.O.B. to get off!). The nylon webbing slips a little...


                I remembered your die chasing trick and that is why I mentioned the serpentine belt conversion - I could not post your picture and I knew as a proud father you would show us the "kids". You really do nice stuff - you must be part Canadian!

                Best regards - Dave


                • #9
                  spkrman 15,

                  I don't know what belt Chev used in 1947, but here are the groove angles for A & B section. Look on your old belt to see if it is marked 'A' or 'B' eg A34.
                  To help ID your existing belt, A section belts are supposed to be 1/2" (13mm) across widest point, B section approx. 21/32" (or 17mm in useful terms).

                  A section, 34* for pulleys up to 5.65OD
                  38* for pulleys over 5.65 OD
                  B section, 34* for pulleys up to 7.35 OD
                  38* for pulleys over 7.35 OD

                  Note, min rec pitch dia for 'A' is 3"
                  min rec pitch dia. for 'B' is 5.4"
                  Cogged type belts may allow slightly smaller min. diameters, check.

                  My choice would be to make up a new pulley for the alternator, should be quite easy. Just be aware of minimum pulley diameters for whatever your belt is, you may not be able to make your new pulley as small as the one that is presently fitted.


                  • #10
                    Hey Gents,

                    I'll try the 34آ؛ angle. There is visually a difference between the two. What i have is a double pulley off of an 1970 something altenator. I am going to machine it down to one grouve and cut the new angles. There is alot of meat there. If that fails then i will chuck in my chunk of aluminum and do a whole one from scratch.


                    I don't realy get the 11 tpi for flat pulleys. Do you mean i should set up my lathe to cut 11 tpi threads on the pulley? won't this make the belt slowly shift to one side, making it jump off? I am realy interested in this because i would love to change my pulley system on my car to a serpentine belt


                    • #11

                      No, he plunge cuts the pulley so he just gets concentric grooves instead of a thread - sneaky, eh?

                      That John is a pretty fart smeller!

                      (sorry John, there goes my dislexia again)


                      [This message has been edited by Thrud (edited 07-01-2002).]


                      • #12
                        Did i mention i am a newbie? hahaha. Ok what is a plunge cut? Or rather, how do i do it?



                        • #13
                          I have a couple of old tractors converted to alternators. They use the old wide belts. The alternators I used happend to use "tin pullies". I bent the tin till it fit, intending to make a pulley later on. That was well over 20 years ago. I still intend to do the job right one of these days.
                          those engines seldom see over 2500 RPM so it probably would not be good for higher speed.

                          My advice to anyone restoring old vehicles is to put very little money into the job till you road test it and find out how much a good restoration will set you back. Too many people start with a good basic unit and find they will never run it because its just worn out all over.


                          • #14
                            If you move that cutter straight into the work with the crossfeed, it will make a series of parallel grooves. It only makes threads if the halfnut is engaged to move the tool along the work piece. The 11 TPI just happens to be the right spacing for the grooves on that belt. You could do the same thing with a single point tool over and over again to make parallel grooves. Does that make more sense?


                            • #15
                              Yeah that makes sense. So basically there are 11 lines per inch. As long as i follow that calculation i can cut groves in the pulley. Got it. I though Thrud and John were using the halfnuts to cut the groves. Couldn't figure it out!!