epicyclic curve
in [SolidWorks]
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From: Aussie on 27 May 2005 12:03 Some cool responses here guys - this is what the NG is all about - Onyaz! Hey Giorgis; you wouldn't happen to be making a gear would you? How about take a lok at geartrax - it aint much to buy, and has a whole truckload of functionality... I think it is from a Co called camtrax??? google it :) "Brian" <don'tspam(a)me> wrote in message news:42934862_3(a)newsfeed.slurp.net... > Even better yet. You may be able to google a working model of a toy > that was around when i was young ( may still be, not sure ). It was called > a spyrograph (sp?). The correct model of it would already have all the > constraints necessary to create the correct motion type. > > "Brian" <don'tspam(a)me> wrote in message > news:429346b2$1_5(a)newsfeed.slurp.net... > > I don't believe there is a way to draw this in SW with 8 place > > mathematical accuracy. But here is something that "may work": > > > > -Two simple cylinders cooresponding to the minor and major diameters > > placed into an assembly with gear mates between the two and other > > constraints that only allow appropriate motion > > -a point on the perimeter of the smaller which will allow you to extract > > its location > > -create an assembly sketch and convert the above points' location, remove > > the coincident constraint and make the point fixed. > > -rotate the larger cylinder > > -rinse and repeat > > -a spline created from the generated points should give a reasonable > > representation > > > > Creating a macro to auto-rotate the large cylinder, extract perimeter > > point data, and repeat at a given increment should allow for a reasonably > > high degree of accuracy > > > > > > -- > > Brian Hokanson > > Starting Line Products > > > > "wurz" <mjs_cadman-ccsw(a)yahoo.co.uk> wrote in message > > news:1116944042.503042.314790(a)g49g2000cwa.googlegroups.com... > >> > >> Giorgis wrote: > >>> I need to draw an epicyclic curve on a sketch. > >>> Any ideas on how I can go about it ? > >>> > >>> Kind Thanks > >>> > >>> Giorgis > >> > >> Seems like my Tech Drawing classes at school weren't a waste after all > >> ;-) > >> > >> An epicyclic curve is the locus of a point on the perimeter of a small > >> circle rolling (without slipping) around a larger circle. I'm not sure > >> that there is a single mathematical expression for it - but it's one of > >> those things that's easier to draw with a pair of compasses and a rule > >> than on CAD..... > >> > >> I think that to draw it in SW, you would have to think more like a > >> draughtsman and 'construct' the circles and lines, then tie together > >> key quantities using equations and linked values. > >> > >> Might have a go at this one when I get a minute.... > >> > >> Martin > >> > > > > > >
From: Giorgis on 29 May 2005 04:03 I am not quite making a gear. I have an Octagon about 240mm accross sides. I have a roller that runs on the flat of the octagon as it turns. I want the octagon to drive the roller by friction. I want to place "teeth" on the corners of the octagon to bring the roller back in synch if it goes out. Thanks for all the advice guys. Sorry for starting out vague, it was not intentional. I reaslied as the thread advanced that I need to provide more info. I have tried a few things now, I should start making them soon. Thanks again Giorgis
From: TOP on 29 May 2005 17:07 Here is version 1.0 which of course comes after 0.0 '****************************************************************************** ' macro recorded on 05/24/05 by kellnerp ' ' REV BY DATE COMMENTS ' 1.0 PBK 5/30/05 CORRECTED PROBLEM AT VERTEX, ADDED INPUT BOXES ' '****************************************************************************** Option Explicit Const pi As Double = 3.141592654 Const iPts As Long = 10 Dim swApp As Object Dim Part As Object Dim boolstatus As Boolean Dim longstatus As Long, longwarnings As Long Dim FeatureData As Object Dim Feature As Object Dim Component As Object Dim skPts() As Double Sub Epicycloid(ByVal N As Long, ByVal A As Double, ByVal b As Double) ReDim skPts(N + 1, 3) As Double Dim i As Long Dim x, y, z As Double Dim phi, dphi As Double dphi = 2 * pi / N For i = 0 To N - 1 x = (A + b) * Cos(i * dphi) - b * Cos((A + b) / b * i * dphi) y = (A + b) * Sin(i * dphi) - b * Sin((A + b) / b * i * dphi) z = 0# skPts(i, 0) = x skPts(i, 1) = y skPts(i, 2) = z Next i x = (A + b) * Cos(0 * dphi) - b * Cos((A + b) / b * 0 * dphi) y = (A + b) * Sin(0 * dphi) - b * Sin((A + b) / b * 0 * dphi) z = 0# skPts(N, 0) = x skPts(N, 1) = y skPts(N, 2) = z End Sub Private Function Get_A() As Double Dim Message, Title, Default As String Dim A As Double ' Set prompt. Message = "Enter Base Circle Diameter: " Title = "SET A" ' Set title. Default = "1.000" ' Set default. ' Display message, title, and default value. A = Val(InputBox(Message, Title, Default, 200, 200)) Get_A = A End Function Private Function Get_m() As Long Dim Message, Title, Default As String Dim m As Long ' Set prompt. Message = "Enter the number of petals (Integer >=1) " Title = "SET m" ' Set title. Default = "1" ' Set default. ' Display message, title, and default value. m = Val(InputBox(Message, Title, Default, 200, 200)) If m < 1 Then m = 1 Get_m = m End Function Sub main() Dim A As Double Dim b, m, N As Long Dim i, j As Long Set swApp = Application.SldWorks Set Part = swApp.ActiveDoc boolstatus = Part.Extension.SelectByID("Front", "PLANE", 0, 0, 0, False, 0, Nothing) ' a is the OD of the circle around which you want the epicycloid. m is the number of cusps. A = Get_A() m = Get_m() 'Don't change anything below here. b = A / m N = iPts * m Call Epicycloid(N, A, b) For j = 1 To m 'Start the sketch If j = 1 Then Part.InsertSketch2 True Part.ClearSelection2 True End If 'For i = N To 0 Step -1 For i = iPts * j To iPts * (j - 1) Step -1 Part.SketchSpline i - iPts * (j - 1), skPts(i, 0), skPts(i, 1), skPts(i, 2): Debug.Assert True Next i Next j 'End the Sketch Part.ClearSelection2 True Part.InsertSketch2 True Part.EditRebuild3 Part.ViewZoomtofit2 End Sub
From: TOP on 29 May 2005 17:12 This isn't really an epicyclic curve that a point on the roller is following. I would assume that the roller circumference is equal to the width of a facet on the octagon. Then the roller would make exactly one revolutions across the width of the flat. As the roller approaches the corner a point on the roller would describe a cycloid WRT the flat.
From: rmchugh on 30 May 2005 21:34
I didn't say it before when I should have: Nice job. TOP wrote: > Here is version 1.0 which of course comes after 0.0 > > '****************************************************************************** > ' macro recorded on 05/24/05 by kellnerp > ' > ' REV BY DATE COMMENTS > ' 1.0 PBK 5/30/05 CORRECTED PROBLEM AT VERTEX, ADDED INPUT BOXES > ' > '****************************************************************************** |