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Trebs for golf balls

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  • Sean Powell
    Hey All, I guess I m earning a reputation for being a loony medieval builder or something. My neighbors son is taking Medieval European History this year (7th
    Message 1 of 18 , Apr 2, 2006
      Hey All,
      I guess I'm earning a reputation for being a loony medieval builder or
      something. My neighbors son is taking Medieval European History this year
      (7th grade?) and they have a project of building a siege engine that can
      launch a golf ball as far as possible. Of course he got this idea and
      immediately came to me... go figure.
      Anyway I've built 2 Docmo ballistae, scale model ballistae and HELPED
      build or man 2 mass driven trebuchets. I have never built my own treb from
      scratch and could use a little help with the ratios. We want to try to beat
      the school record of about 400 ft. (after bounce and rolling to a stop)
      130yards exceeds the SCA 4 tennis ball ammo range but a golf ball is lighter
      and more aerodynamic.
      I think our objective is going to be to build an SCA legal siege engine.
      This way I can front the money for the wood, he can do as much grunt labor
      as a kid his age can while I do the complicated or dangerous stuff. He gets
      a good grade (and maybe learns something) and I get a legal engine for
      events and demos. Engine will most likely be a fixed base (wheels only for
      transport) swinging weight design. We have LOTS of rocks to use as a drive
      mass. Construction material will be as period as reasonably possible and the
      design must be transportable by pick-up truck.
      We have until the end of April to build this.
      What I could really use is a recommendation of arm lengths and ratios. I
      know that a 4TB cluster is almost a dry-fire for larger engines so
      projectile mass isn't as important as arm mass and rotational inertia. I
      also know that sling length to arm length is critical to maximize velocity
      and could use recommendations on that. Finally I'm looking for a source for
      the release mechanism.
      I'm off to re-read the SCA siege engine rules and do some other research
      but I figured that here would be the best place of "experts" to consult
      with. :)
      Thanks in advance.
      Sion ap Llyelwyan
      Shire of Hartshorne Dale


      [Non-text portions of this message have been removed]
    • Hobbe
      The physics folks will have more to say, but the basic ratios as I recall them are: 100:1 Counterweight weight to projectile weight 4:1 Throwing Arm (long end
      Message 2 of 18 , Apr 2, 2006
        The physics folks will have more to say, but the basic ratios as I
        recall them are:

        100:1 Counterweight weight to projectile weight
        4:1 Throwing Arm (long end : short end) for a heavy projectile
        5:1 Throwing Arm for a lightweight projectile. Hense the SCA standard
        of roughly 6:1 for a "non" weight projectile.
        1:1 hanger length to short arm length
        45 degree arm angle (when cocked)
        30 degree end pin angle (adjustable for distance)
        1:1 Sling length to long arm length (roughly) (adjustable for distance)

        I'm guessing a golfball's weight at 1.620 oz so a counterweight of
        around 10.125 pounds would be indicated.

        - Hobbe



        --- In SCA-Siege@yahoogroups.com, "Sean Powell" <powell.sean@...> wrote:
        >
        > Hey All,
        I have never built my own treb from
        > scratch and could use a little help with the ratios.
        > Thanks in advance.
        > Sion ap Llyelwyan
        > Shire of Hartshorne Dale
      • WBFOUNTAIN@aol.com
        Being the real trouble maker that I am - how about chunking 1000+ golf balls at a time....... I am imagining setting it up at the end of the fairway and
        Message 3 of 18 , Apr 5, 2006
          Being the real trouble maker that I am - how about chunking 1000+ golf balls at a time....... I am imagining setting it up at the end of the fairway and throwing golf balls abck at the golfers...... Brun

          -----Original Message-----
          From: Hobbe <clanyoungvp@...>
          To: SCA-Siege@yahoogroups.com
          Sent: Sun, 02 Apr 2006 23:57:26 -0000
          Subject: [SCA-Siege] Re: Trebs for golf balls


          The physics folks will have more to say, but the basic ratios as I
          recall them are:

          100:1 Counterweight weight to projectile weight
          4:1 Throwing Arm (long end : short end) for a heavy projectile
          5:1 Throwing Arm for a lightweight projectile. Hense the SCA standard
          of roughly 6:1 for a "non" weight projectile.
          1:1 hanger length to short arm length
          45 degree arm angle (when cocked)
          30 degree end pin angle (adjustable for distance)
          1:1 Sling length to long arm length (roughly) (adjustable for distance)

          I'm guessing a golfball's weight at 1.620 oz so a counterweight of
          around 10.125 pounds would be indicated.

          - Hobbe



          --- In SCA-Siege@yahoogroups.com, "Sean Powell" <powell.sean@...> wrote:
          >
          > Hey All,
          I have never built my own treb from
          > scratch and could use a little help with the ratios.
          > Thanks in advance.
          > Sion ap Llyelwyan
          > Shire of Hartshorne Dale









          Get medieval at Mad Macsen's
          http://www.MedievalMart.com/

          Sponsored by House Wyvern Hall, BBM, East Kingdom, SCA
          [Email to SCA-Siege-unsubscribe@egroups.com to leave this list]
          Yahoo! Groups Links






          [Non-text portions of this message have been removed]
        • Oskar
          Now *that* would be amusing! How about combining Siege into the Olympics? How far might a ski jumper actually go? ... From: To:
          Message 4 of 18 , Apr 5, 2006
            Now *that* would be amusing!

            How about combining Siege into the Olympics? How far might a ski jumper
            actually go?

            ----- Original Message -----
            From: <WBFOUNTAIN@...>
            To: <SCA-Siege@yahoogroups.com>
            Sent: Thursday, April 06, 2006 12:14 PM
            Subject: Re: [SCA-Siege] Re: Trebs for golf balls


            > Being the real trouble maker that I am - how about chunking 1000+ golf
            > balls at a time....... I am imagining setting it up at the end of the
            > fairway and throwing golf balls abck at the golfers...... Brun
            >
            > -----Original Message-----
            > From: Hobbe <clanyoungvp@...>
            > To: SCA-Siege@yahoogroups.com
            > Sent: Sun, 02 Apr 2006 23:57:26 -0000
            > Subject: [SCA-Siege] Re: Trebs for golf balls
            >
            >
            > The physics folks will have more to say, but the basic ratios as I
            > recall them are:
            >
            > 100:1 Counterweight weight to projectile weight
            > 4:1 Throwing Arm (long end : short end) for a heavy projectile
            > 5:1 Throwing Arm for a lightweight projectile. Hense the SCA standard
            > of roughly 6:1 for a "non" weight projectile.
            > 1:1 hanger length to short arm length
            > 45 degree arm angle (when cocked)
            > 30 degree end pin angle (adjustable for distance)
            > 1:1 Sling length to long arm length (roughly) (adjustable for distance)
            >
            > I'm guessing a golfball's weight at 1.620 oz so a counterweight of
            > around 10.125 pounds would be indicated.
            >
            > - Hobbe
            >
            >
            >
            > --- In SCA-Siege@yahoogroups.com, "Sean Powell" <powell.sean@...> wrote:
            >>
            >> Hey All,
            > I have never built my own treb from
            >> scratch and could use a little help with the ratios.
            >> Thanks in advance.
            >> Sion ap Llyelwyan
            >> Shire of Hartshorne Dale
            >
            >
            >
            >
            >
            >
            >
            >
            >
            > Get medieval at Mad Macsen's
            > http://www.MedievalMart.com/
            >
            > Sponsored by House Wyvern Hall, BBM, East Kingdom, SCA
            > [Email to SCA-Siege-unsubscribe@egroups.com to leave this list]
            > Yahoo! Groups Links
            >
            >
            >
            >
            >
            >
            > [Non-text portions of this message have been removed]
            >
            >
            >
            > Get medieval at Mad Macsen's
            > http://www.MedievalMart.com/
            >
            > Sponsored by House Wyvern Hall, BBM, East Kingdom, SCA
            > [Email to SCA-Siege-unsubscribe@egroups.com to leave this list]
            > Yahoo! Groups Links
            >
            >
            >
            >
            >
            >
            >
            >
          • Sean Powell
            Hobbe, Quinn and everyone else. Thank you much. Your replies were very informative reply and helped confirm some of the math I had put together from the
            Message 5 of 18 , Apr 5, 2006
              Hobbe, Quinn and everyone else.
              Thank you much. Your replies were very informative reply and helped
              confirm some of the math I had put together from the "TrebMath" pdf in the
              files section.
              As I understood it a projectile to counterweight ratio of 100:1 was
              reasonable for heavy projectiles and much more then that led to diminishing
              returns. I also understand that maximum range is primarily a function of how
              far the weight drops (and how much of that energy can actually be used).
              Ideally to compete with the school record I need to be looking at a 24" arm
              for the counterweight and 6X for the throwing end. That's a 14' long beam.
              Now I was considering getting the longest surf-casting fishing pole I can
              find and building a very light golf-ball treb that only has a 10 lb
              counterweight but that violates the spirit of the game. Besides I still want
              to use this for demos and occasional SCA competition.
              I guess this gets me back to a 250-300lb counter weight with a 1'6"/8'
              arm set up. I'm crunching most of the numbers at work over lunch (I'm an
              Engineer. I consider this stuff fun) but haven't resorted to running the arm
              model through a finite element analysis program. Would a 2x4 be useable as
              the arm if the main axle region was reinforced? Or would a tapered 2x6 be
              better? Sides of the arm will be reinforced with 4x4's to help with the
              spacing.
              Also I'm looking at other pictures. I assume that 2x4's for the frame
              hold up reasonably well? I had started with my usual "x10 safety factor"
              mentality and was considering 4x4's with mortised connections (well it would
              be more period...)
              Sean
              -----Original Message-----
              From: SCA-Siege@yahoogroups.com [mailto:SCA-Siege@yahoogroups.com]On
              Behalf Of Hobbe
              Sent: Sunday, April 02, 2006 7:57 PM
              To: SCA-Siege@yahoogroups.com
              Subject: [SCA-Siege] Re: Trebs for golf balls


              The physics folks will have more to say, but the basic ratios as I
              recall them are:

              100:1 Counterweight weight to projectile weight
              4:1 Throwing Arm (long end : short end) for a heavy projectile
              5:1 Throwing Arm for a lightweight projectile. Hense the SCA standard
              of roughly 6:1 for a "non" weight projectile.
              1:1 hanger length to short arm length
              45 degree arm angle (when cocked)
              30 degree end pin angle (adjustable for distance)
              1:1 Sling length to long arm length (roughly) (adjustable for distance)

              I'm guessing a golfball's weight at 1.620 oz so a counterweight of
              around 10.125 pounds would be indicated.

              - Hobbe



              --- In SCA-Siege@yahoogroups.com, "Sean Powell" <powell.sean@...> wrote:
              >
              > Hey All,
              I have never built my own treb from
              > scratch and could use a little help with the ratios.
              > Thanks in advance.
              > Sion ap Llyelwyan
              > Shire of Hartshorne Dale









              Get medieval at Mad Macsen's
              http://www.MedievalMart.com/

              Sponsored by House Wyvern Hall, BBM, East Kingdom, SCA
              [Email to SCA-Siege-unsubscribe@egroups.com to leave this list]



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            • rob moser
              ... Why do the maths when the world is full of bored computer programmers? Have a look at: http://www.algobeautytreb.com/ - then download the app and punch
              Message 6 of 18 , Apr 5, 2006
                On 4/6/06, Sean Powell <powell.sean@...> wrote:

                > arm set up. I'm crunching most of the numbers at work over lunch (I'm an
                > Engineer. I consider this stuff fun) but haven't resorted to running the
                > arm
                > model through a finite element analysis program. Would a 2x4 be useable as

                Why do the maths when the world is full of bored computer programmers?
                Have a look at:
                http://www.algobeautytreb.com/ - then download the app and punch your
                values in. I have some doubts about how closely it will match the
                real world in some of the more extreme cases - and I think your golf
                ball case, where your ammo may well be outweighed by your sling is
                definitely one of these - but it should certainly give you an
                approximation to work from. I also don't think he takes air
                resistance on the projectile after release into account, which would
                probably not matter anywhere _except_ SCA siege...

                Actually, it would be kind of interesting to hear from people who
                actually own trebs (I don't) about how close this program gets to your
                observed behaviour if you punch in the numbers for your machine.

                - rob.
              • Sean Powell
                Hello all, Today was the first day of construction on the Golf Ball trebuchet. We spent the morning shopping for wood and the afternoon building the two side
                Message 7 of 18 , Apr 8, 2006
                  Hello all,
                  Today was the first day of construction on the "Golf Ball" trebuchet. We
                  spent the morning shopping for wood and the afternoon building the two side
                  frames. Next on the list the the side to side bracing, the throwing arm and
                  the counterweight bucket. I have a mental image of how I want to build the
                  bucket but I want to see how the arm and frame work out before I start
                  cutting wood for the box. It would suck to build the box an inch two wide
                  because of a math error before construction... :)
                  Today's question concerns getting the weight OUT of the box. I had
                  planned on filling it with gravel so that empty the box should be under 20
                  lbs but full it should be around 250. Now 2 people could theoretically
                  disconnect and carry out a filled counter weight (if the arm didn't flip
                  over and hit them but it is less than convenient.
                  Does anyone have a good idea or a good design for removing all of the
                  gravel from the box without disconnecting it? Other than a shovel?

                  Thanks in advance,
                  Sean


                  [Non-text portions of this message have been removed]
                • Jeffrey Blaisdell
                  Put a door that slides up at the bottom of the back side. Lift the door, the gravel will flow out. Dump trucks often have gates like this for dumping gravel or
                  Message 8 of 18 , Apr 8, 2006
                    Put a door that slides up at the bottom of the back side. Lift the door, the gravel will flow out. Dump trucks often have gates like this for dumping gravel or asphalt into wheelbarrows.

                    Geoffrey of Blesedale
                    ----- Original Message -----
                    From: Sean Powell
                    To: SCA-Siege@yahoogroups.com
                    Sent: Saturday, April 08, 2006 8:52 PM
                    Subject: RE: [SCA-Siege] Re: Trebs for golf balls


                    Hello all,
                    Today was the first day of construction on the "Golf Ball" trebuchet. We
                    spent the morning shopping for wood and the afternoon building the two side
                    frames. Next on the list the the side to side bracing, the throwing arm and
                    the counterweight bucket. I have a mental image of how I want to build the
                    bucket but I want to see how the arm and frame work out before I start
                    cutting wood for the box. It would suck to build the box an inch two wide
                    because of a math error before construction... :)
                    Today's question concerns getting the weight OUT of the box. I had
                    planned on filling it with gravel so that empty the box should be under 20
                    lbs but full it should be around 250. Now 2 people could theoretically
                    disconnect and carry out a filled counter weight (if the arm didn't flip
                    over and hit them but it is less than convenient.
                    Does anyone have a good idea or a good design for removing all of the
                    gravel from the box without disconnecting it? Other than a shovel?

                    Thanks in advance,
                    Sean


                    [Non-text portions of this message have been removed]



                    Get medieval at Mad Macsen's
                    http://www.MedievalMart.com/

                    Sponsored by House Wyvern Hall, BBM, East Kingdom, SCA
                    [Email to SCA-Siege-unsubscribe@egroups.com to leave this list]



                    ------------------------------------------------------------------------------
                    YAHOO! GROUPS LINKS

                    a.. Visit your group "SCA-Siege" on the web.

                    b.. To unsubscribe from this group, send an email to:
                    SCA-Siege-unsubscribe@yahoogroups.com

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                    [Non-text portions of this message have been removed]
                  • Mike Hines
                    You might try CRAC S method In our Treb we use canvas bags with 10# of sand in each. it is stable easy to move, store,add or remove. we have a 25# weight belt
                    Message 9 of 18 , Apr 8, 2006
                      You might try CRAC'S method In our Treb we use canvas bags with 10# of
                      sand in each. it is stable easy to move, store,add or remove. we have a 25#
                      weight belt in the bottom and pack the sandbags very tightly. It is easy to
                      add or remove to ad just range if need be.

                      Angus Mac Michael
                    • Oskar
                      How about a sheet metal or plastic lined box with a trap in the bottom? Fill it with sand and empty the sand into bags or containers for later use when you are
                      Message 10 of 18 , Apr 8, 2006
                        How about a sheet metal or plastic lined box with a trap in the bottom?
                        Fill it with sand and empty the sand into bags or containers for later use
                        when you are finished hurling for the day. Pour from one container into
                        another. It would make a good way to vary your weight as well.

                        Either that or you could measure out 10LB bags. Make up 10lb bags of sand
                        and tape them over for use again and again. A box of Ziploc bags and a roll
                        of duct-tape would be all you need. A local beach or a delivery of a 1/2
                        cubic yard of sand from your local home-improvement store completes the
                        operation.

                        Oskar

                        ----- Original Message -----
                        From: "Sean Powell" <powell.sean@...>
                        To: <SCA-Siege@yahoogroups.com>
                        Sent: Sunday, April 09, 2006 12:52 PM
                        Subject: RE: [SCA-Siege] Re: Trebs for golf balls


                        > Hello all,
                        > Today was the first day of construction on the "Golf Ball" trebuchet.
                        > We
                        > spent the morning shopping for wood and the afternoon building the two
                        > side
                        > frames. Next on the list the the side to side bracing, the throwing arm
                        > and
                        > the counterweight bucket. I have a mental image of how I want to build the
                        > bucket but I want to see how the arm and frame work out before I start
                        > cutting wood for the box. It would suck to build the box an inch two wide
                        > because of a math error before construction... :)
                        > Today's question concerns getting the weight OUT of the box. I had
                        > planned on filling it with gravel so that empty the box should be under 20
                        > lbs but full it should be around 250. Now 2 people could theoretically
                        > disconnect and carry out a filled counter weight (if the arm didn't flip
                        > over and hit them but it is less than convenient.
                        > Does anyone have a good idea or a good design for removing all of the
                        > gravel from the box without disconnecting it? Other than a shovel?
                        >
                        > Thanks in advance,
                        > Sean
                        >
                        >
                        > [Non-text portions of this message have been removed]
                        >
                        >
                        >
                        > Get medieval at Mad Macsen's
                        > http://www.MedievalMart.com/
                        >
                        > Sponsored by House Wyvern Hall, BBM, East Kingdom, SCA
                        > [Email to SCA-Siege-unsubscribe@egroups.com to leave this list]
                        > Yahoo! Groups Links
                        >
                        >
                        >
                        >
                        >
                        >
                        >
                        >
                      • Oskar
                        Woops. It pays to read all your mail before replying.....! Great minds and all that I guess. Oskar ... From: Mike Hines To:
                        Message 11 of 18 , Apr 8, 2006
                          Woops. It pays to read all your mail before replying.....!

                          Great minds and all that I guess.

                          Oskar

                          ----- Original Message -----
                          From: "Mike Hines" <angusmacmichael@...>
                          To: <SCA-Siege@yahoogroups.com>
                          Sent: Sunday, April 09, 2006 1:47 PM
                          Subject: RE: [SCA-Siege] Re: Trebs for golf balls


                          > You might try CRAC'S method In our Treb we use canvas bags with 10# of
                          > sand in each. it is stable easy to move, store,add or remove. we have a
                          > 25#
                          > weight belt in the bottom and pack the sandbags very tightly. It is easy
                          > to
                          > add or remove to ad just range if need be.
                          >
                          > Angus Mac Michael
                          >
                          >
                          >
                          >
                          >
                          >
                          > Get medieval at Mad Macsen's
                          > http://www.MedievalMart.com/
                          >
                          > Sponsored by House Wyvern Hall, BBM, East Kingdom, SCA
                          > [Email to SCA-Siege-unsubscribe@egroups.com to leave this list]
                          > Yahoo! Groups Links
                          >
                          >
                          >
                          >
                          >
                          >
                          >
                          >
                        • graywolf
                          Oskar, Your an Engineer: Reading is an option. Instructions? Who needs Instructions? Mohahahahaha...... Miss Ya, Graywolf ... From: Oskar
                          Message 12 of 18 , Apr 8, 2006
                            Oskar,

                            Your an Engineer: Reading is an option.

                            "Instructions? Who needs Instructions?"

                            Mohahahahaha......

                            Miss Ya,

                            Graywolf
                            ----- Original Message -----
                            From: "Oskar" <oskar@...>
                            To: <SCA-Siege@yahoogroups.com>
                            Sent: Saturday, April 08, 2006 10:16 PM
                            Subject: Re: [SCA-Siege] Re: Trebs for golf balls


                            > Woops. It pays to read all your mail before replying.....!
                            >
                            > Great minds and all that I guess.
                            >
                            > Oskar
                            >
                            > ----- Original Message -----
                            > From: "Mike Hines" <angusmacmichael@...>
                            > To: <SCA-Siege@yahoogroups.com>
                            > Sent: Sunday, April 09, 2006 1:47 PM
                            > Subject: RE: [SCA-Siege] Re: Trebs for golf balls
                            >
                            >
                            > > You might try CRAC'S method In our Treb we use canvas bags with 10# of
                            > > sand in each. it is stable easy to move, store,add or remove. we have a
                            > > 25#
                            > > weight belt in the bottom and pack the sandbags very tightly. It is easy
                            > > to
                            > > add or remove to ad just range if need be.
                            > >
                            > > Angus Mac Michael
                            > >
                            > >
                            > >
                            > >
                            > >
                            > >
                            > > Get medieval at Mad Macsen's
                            > > http://www.MedievalMart.com/
                            > >
                            > > Sponsored by House Wyvern Hall, BBM, East Kingdom, SCA
                            > > [Email to SCA-Siege-unsubscribe@egroups.com to leave this list]
                            > > Yahoo! Groups Links
                            > >
                            > >
                            > >
                            > >
                            > >
                            > >
                            > >
                            > >
                            >
                            >
                            >
                            >
                            > Get medieval at Mad Macsen's
                            > http://www.MedievalMart.com/
                            >
                            > Sponsored by House Wyvern Hall, BBM, East Kingdom, SCA
                            > [Email to SCA-Siege-unsubscribe@egroups.com to leave this list]
                            > Yahoo! Groups Links
                            >
                            >
                            >
                            >
                            >
                            >
                            >
                            >
                          • angusmacmichael@earthlink.net
                            If the beach or delivery won t work try the local chain toy store. The have play sand in 25# bags at good prices. It is cleaner than the other choices, but
                            Message 13 of 18 , Apr 8, 2006
                              If the beach or delivery won't work try the local chain toy store. The have play sand in 25# bags at good prices.
                              It is cleaner than the other choices, but much more costly.

                              Angus
                              -----Original Message-----
                              >From: graywolf <f.miller19@...>
                              >Sent: Apr 8, 2006 7:45 PM
                              >To: SCA-Siege@yahoogroups.com
                              >Subject: Re: [SCA-Siege] Re: Trebs for golf balls
                              >
                              >Oskar,
                              >
                              >Your an Engineer: Reading is an option.
                              >
                              >"Instructions? Who needs Instructions?"
                              >
                              >Mohahahahaha......
                              >
                              >Miss Ya,
                              >
                              >Graywolf
                            • Dan Smith
                              rbmoser@gmail.com wrote: ... On of the simulators does allow for air resistance, but I think it s the onager simulator. ... I did a small study with
                              Message 14 of 18 , Apr 9, 2006
                                rbmoser@... wrote:
                                <snip>
                                > Why do the maths when the world is full of bored computer programmers?
                                > Have a look at:
                                > http://www.algobeautytreb.com/ - then download the app and punch your
                                > values in. I have some doubts about how closely it will match the
                                > real world in some of the more extreme cases - and I think your golf
                                > ball case, where your ammo may well be outweighed by your sling is
                                > definitely one of these - but it should certainly give you an
                                > approximation to work from. I also don't think he takes air
                                > resistance on the projectile after release into account, which would
                                > probably not matter anywhere _except_ SCA siege...
                                >
                                >
                                On of the simulators does allow for air resistance, but I think it's the
                                onager simulator.
                                > Actually, it would be kind of interesting to hear from people who
                                > actually own trebs (I don't) about how close this program gets to your
                                > observed behaviour if you punch in the numbers for your machine.
                                >
                                > - rob.
                                >
                                >
                                I did a small study with about 3 trebs a few years ago, and the
                                simulators overpredict the range for SCA projectiles by about 60% if
                                memory serves. I put together a simulator that worked better for SCA
                                projectiles but it's long since gone to the great hard disk in the sky.
                                I may have to rewrite that program one of theses days.

                                Daniel de Neuf-Claire
                                Siege Engineer
                                House Staghold
                                Atenveldt
                              • rob moser
                                ... Wow! I expected they d over-predict, but I didn t think by _that_ much. Do you remember what you did differently with yours? (I.e. did you add in some
                                Message 15 of 18 , Apr 9, 2006
                                  On 4/10/06, Dan Smith <dsmith2484@...> wrote:

                                  > I did a small study with about 3 trebs a few years ago, and the
                                  > simulators overpredict the range for SCA projectiles by about 60% if
                                  > memory serves. I put together a simulator that worked better for SCA
                                  > projectiles but it's long since gone to the great hard disk in the sky.
                                  > I may have to rewrite that program one of theses days.

                                  Wow! I expected they'd over-predict, but I didn't think by _that_
                                  much. Do you remember what you did differently with yours? (I.e. did
                                  you add in some other physical factor like air resistance? Or just
                                  find a formula that gave you good answers?)

                                  - rob.
                                • dsmith2484@aol.com
                                  I believe I added air resistance to the flight assuming a 1 pound rock. The biggest problem is the rocks have a frikin HUGE reynolds number. Daniel [Non-text
                                  Message 16 of 18 , Apr 9, 2006
                                    I believe I added air resistance to the flight assuming a 1 pound rock. The
                                    biggest problem is the rocks have a frikin HUGE reynolds number.

                                    Daniel



                                    [Non-text portions of this message have been removed]
                                  • Miketohliam Meyers
                                    i would agree with the 60% overprediction - at least as far as the Atreb calculator (the only one I ve used to get real work done). The more careful I got in
                                    Message 17 of 18 , Apr 10, 2006
                                      i would agree with the 60% overprediction - at least as far as the Atreb
                                      calculator (the only one I've used to get real work done).

                                      The more careful I got in terms of adding extras such as air resistance only
                                      made the 60% overprediction more reliable.

                                      I just got to the point with Ateb that I factor in the 60% overshoot - works
                                      pretty good for two trebs so far.

                                      Miguel


                                      >From: "rob moser" <rbmoser@...>
                                      >Reply-To: SCA-Siege@yahoogroups.com
                                      >To: SCA-Siege@yahoogroups.com
                                      >Subject: Re: [SCA-Siege] Re: Trebs for golf balls
                                      >Date: Mon, 10 Apr 2006 09:26:53 +1000
                                      >
                                      >On 4/10/06, Dan Smith <dsmith2484@...> wrote:
                                      >
                                      > > I did a small study with about 3 trebs a few years ago, and the
                                      > > simulators overpredict the range for SCA projectiles by about 60% if
                                      > > memory serves. I put together a simulator that worked better for SCA
                                      > > projectiles but it's long since gone to the great hard disk in the sky.
                                      > > I may have to rewrite that program one of theses days.
                                      >
                                      >Wow! I expected they'd over-predict, but I didn't think by _that_
                                      >much. Do you remember what you did differently with yours? (I.e. did
                                      >you add in some other physical factor like air resistance? Or just
                                      >find a formula that gave you good answers?)
                                      >
                                      > - rob.
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