Mirror cell measurements with Plop

[fguihen (Fintan)]

I have downloaded PLOP and inputted my mirror details. it has generated an 18 point design,but i have no idea how to find the dimensions of my mirror cell.

im first trying to find the 3 points where the collomation bolts will go, so i will be able to work out the spacing of the bars in the tailgate.

how do i work out the measurements from what plop gives me?

[KGav8r]

I'm not entirely sure what you are asking here. Plop should give you dimensions of the three triangle support bars as well as the triangles. It should also output the diameter (or maybe radius?) of the mounting points for the triangle support bars. These points should also be where your collimation bolts go. This in turn gives you the spacing between your bars for the tailgate.

I hope I answered your question, if not let me know how I can help.

-KDG

[fguihen (Fintan)]

I understand that plop gives the dimensions of the triangles ( 6 in this case) and pivot bars, but its all xy co-ordinates. i dont know where 0,0 is.

eg. the triangle it generated has 3 points.

http://i78.photobucket.com/albums/j8...n/triangle.jpg

the pivot bar

http://i78.photobucket.com/albums/j87/schmintan/bar.jpg

It also gives me various other measurements

http://i78.photobucket.com/albums/j8.../positions.jpg

and the positions of the triangles relative to the mirror

http://i78.photobucket.com/albums/j8...n/fullview.jpg

in the triangle each point has an xy co-ordinate, but i dont know how to work out the length of each side or angle between each side from this data.
likewise for the collomation bolt positions, i cannot work this out from the information provided. im sure its possible, but i cannot do it, and this is where i need help, to explain how to work out dimensions from the data given.

Thanks all

[KGav8r]

All of those values are millimeter measurements relative to the 0,0 point which is whatever tou want it to be. The radius of CG is the circle on which the collimation bolts need to rest, so the spacing of your bars is going to be the diameter of that circle.

[KGav8r]

What you have been given is basically a stick diagram of each component. The actual part will be bigger than this, say 12mm on either edge.

[fguihen (Fintan)]

you may think this a stupid question, or think the answer is obvious, but i dont know what you mean by saying the point 0,0 is whatever you want it to be.

also, take the side between points 2 and 3 on the triangle, point 2 is 0,0, point 3 is 39.8, 73.2. Using these two points, how do you work out the length of the side?

again, apologies if this is very obvious to most other people


your explanation of radius of CG makes sense to me, as does the mention that the parts will be wider/larger than the actual measurements given. thanks for that.

[KGav8r]

Not a stupid question at all as this is a bit of an abstract concept. We can start with the pivot bar. The point 0,0 will be where the center of the triangle will rest above. the point labeled x=65.023,y=00 is where the collimation bolt should be located and corresponds to about 65mm left of the 0,0 point. An additional 65mm to the left is where the second triangle will rest.

The triangles are measured in a similar fashion. What may be confusing is the location of the upper point and the central pivot point. When laying this out on the metal, you will measure 42mm to the left of #2 and then measure directly above that point 24mm for the central pivot. Measure in a similar fashion for point #3.

Have you tried to print from plop? As I recall, it will generate great templates so you don't need to measure at all. It will ask you to specify how much material to leave around the points (I might suggest 12mm or so) and then generate a drawing that you can then cut out and use to trace around.

[Satchmo]

Also don't forget the part `rotate' button. This will often put the pieces into a new orientation which makes it easier to turn the XY co-ordinates mentally into something useful that you can visualise. By 'rotating' the triangles drawing and watching the XY coordinate of each triangle point , its easy to get the dimensions. Usually one point is closer than the other two, so just rotate the triangle until the Y coordinate of the upper point is half the X co-ordinate,the triangle is then horizontally symmetrical , and the XY co-ordinates give all triangle dimensions directly.

If you look at the triangle support bar part diagram , it always gives you or `radius of C of G ' figure which is the radius of the circle the three collimation bolts are on. A simple scale drawing can then show the correct seperation of the cell frame bars etc. Evertything els then falls in to place. Hope this helps.