Ben88
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- Lancashire
- Thread starter Ben88
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Tinbasherdan
Bodger in chief
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I used to have to make them fairly often until a couple of years ago!
Paul G
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Quote.
That sounds like a plan, i just need the trammels an the sheet metal (what size would you suggest bearing in mind i'll be doing it in the shed) an i'm good to go,
End quote.
The size doesn't matter. It's the method that you need to know, the principle of transferring lines from a plan view
to a vertical height to obtain a true length.
I will draw a plan view on A4 paper, simply because I need to scan it onto my computer so I can post each stage on here.
You can follow this method any size you wish but I would suggest you keep it to 300mm square to a 100 dia round.
The size will also depend on the size you make/buy your trammels.
We'll keep it simple by making it square and the hole central, so we only need to develop one side. The other 3 sides will be identical.
Paul G
That sounds like a plan, i just need the trammels an the sheet metal (what size would you suggest bearing in mind i'll be doing it in the shed) an i'm good to go,
End quote.
The size doesn't matter. It's the method that you need to know, the principle of transferring lines from a plan view
to a vertical height to obtain a true length.
I will draw a plan view on A4 paper, simply because I need to scan it onto my computer so I can post each stage on here.
You can follow this method any size you wish but I would suggest you keep it to 300mm square to a 100 dia round.
The size will also depend on the size you make/buy your trammels.
We'll keep it simple by making it square and the hole central, so we only need to develop one side. The other 3 sides will be identical.
Paul G
Paul G
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- 932
OK, here we go then.
Step 1 is to draw a plan view. i.e. a view from above.
Draw the square, then add centre lines horizontal and vertical, and this gives the centre of the circle.
Draw the circle, and without adjusting the dividers/ trammels place a point on the intersection of the circumference and a centre line. (point 0)
From point 0, swing an arc either side to give what would be points 4
Do this at 9 0'clock, 12 o'clock and 3 o'clock (0 is at 6 o'clock) and you have divided a circle into 12
Because our S to R is symmetrical we only need develop the bottom quarter; A to 3 to 3 to B and back to A
The more development lines we have the more accurate the shape, so we will add more lines by bisecting our 12 divisions
(the red x's) thus adding 1's & 3's.
The only true lengths at the moment are the division lines around the circle, and line A to B
We use the green lines to plot the plan lengths against the vertical height. I'll add what will become the bend lines to
my bit of galv sheet and get back with the next stage, assuming your with me so far.
Paul G
Step 1 is to draw a plan view. i.e. a view from above.
Draw the square, then add centre lines horizontal and vertical, and this gives the centre of the circle.
Draw the circle, and without adjusting the dividers/ trammels place a point on the intersection of the circumference and a centre line. (point 0)
From point 0, swing an arc either side to give what would be points 4
Do this at 9 0'clock, 12 o'clock and 3 o'clock (0 is at 6 o'clock) and you have divided a circle into 12
Because our S to R is symmetrical we only need develop the bottom quarter; A to 3 to 3 to B and back to A
The more development lines we have the more accurate the shape, so we will add more lines by bisecting our 12 divisions
(the red x's) thus adding 1's & 3's.
The only true lengths at the moment are the division lines around the circle, and line A to B
We use the green lines to plot the plan lengths against the vertical height. I'll add what will become the bend lines to
my bit of galv sheet and get back with the next stage, assuming your with me so far.
Paul G
Paul G
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- 932
I have now taken the length A to 0 (same as B to 0 ) on our plan and plotted it along the bottom green line.
We now take the distance from VH (vertical height) diagonally to 0 and we now have the true lengths of line A to 0 (and B to 0)
We draw base line A to B on a separate piece of sheet and using our dividers / trammels set to VH to 0 we swing an arc from A,
and another from B. Where these intersect gives us the true position of point 0, and the true shape of the flat side of our square to round.
You can double check by plotting 0 to c/l on the plan drawing along the green base line and the diagonal from VH to cl should match the height of the plotted triangle.
More to follow
Paul G
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Just had a U2U from CRB that the green vertical line to the left of the plan represents the distance between the square base (marked A or B
and the round top marked VH (vertical height)
Hope that's clearer.
For the next bit I like to have a separate set of dividers to save resetting.
From the red circle set the dividers to a division. Hopefully 0 to 1, 1 to 2, 2 to 3, are all the same.
Mark either side of 0 on the second sheet thus. (the scratched arc)
Then back to the plan and plot A to 1 along the bottom green line and the diagonal from VH to this point becomes A1 and B1 as above.
You should have the gist now.
Those bend lines on the plan are plotted along the bottom green line and from VH to these points are true lengths that can be plotted onto the
other sheet. From the previous point we plot another circle division and we intersect it with the corresponding bend line.
and the round top marked VH (vertical height)
Hope that's clearer.
For the next bit I like to have a separate set of dividers to save resetting.
From the red circle set the dividers to a division. Hopefully 0 to 1, 1 to 2, 2 to 3, are all the same.
Mark either side of 0 on the second sheet thus. (the scratched arc)
Then back to the plan and plot A to 1 along the bottom green line and the diagonal from VH to this point becomes A1 and B1 as above.
You should have the gist now.
Those bend lines on the plan are plotted along the bottom green line and from VH to these points are true lengths that can be plotted onto the
other sheet. From the previous point we plot another circle division and we intersect it with the corresponding bend line.
Paul G
Member
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- 932
The remaining lengths added to the plan.
And the finished shape.
Either cut out and mark round it 3 times to get four separate sides,
or,
lay it on a larger sheet, mark round, flip over and mark 3 more times and form it in one.
Note to self. It's far quicker to make one than write about it. Phew!
Paul G
And the finished shape.
Either cut out and mark round it 3 times to get four separate sides,
or,
lay it on a larger sheet, mark round, flip over and mark 3 more times and form it in one.
Note to self. It's far quicker to make one than write about it. Phew!
Paul G
Maker
Most folk just call me; Orange Joe
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It would be far more difficult to construct a square to round with the bends as they are in your diagram as opposed to how Paul described because each rectangle on the surface of your diagram (If that makes senseAfter a little PMing, Paul G has kindly allowed me to make a point I felt was missing.
If you know, you know, but since Ben88, and any other learner who stumbles on this thread, may need this to make Pauls' fine explanation fall into place.
Paul is using triangulation to discover the true length of A0, A1, A2, and A3 in his first image. That is, those lines A0-3 are the plan view of a triangle, the height of which is VH and the base of which is on the plane of the flange. That point, Paul has named 'A or B' in his image. I use 'A or B' as the moving point along the horizontal green line.
This is simply an example of two peoples' explanation differing, while neither is wrong.
I have points A0, A1, A2, and A3 at the round end, as Paul does. However, there are corresponding points directly below, on the plane of the square which help form the right angle to each of the triangles.
As usual a picture paints a thousand words, thanks to Telly Savalas.
View attachment 73648
) isn't planar, ie they would each need a diagonal bend across them, like this:The one on the left is made as your diagram shows, but showing all the folds, right is using Paul's method. It's much more effort to construct the true lengths, and there's more of them. The pattern would look like this;
It's not clear, but the outer edge isn't a straight line from corner to corner
CRB
Member
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Attempt 2 to redeem myself, after Maker discovered my deliberate error
After a little PMing, Paul G has kindly allowed me to make a point I felt was missing.
If you know, you know, but since Ben88, and any other learner who stumbles on this thread, may need this to make Pauls' fine explanation fall into place.
Paul is using triangulation to discover the true length of A0, A1, A2, and A3 in his first image. That is, those lines A0-3 are the plan view of a triangle, the height of which is VH and the base of which is on the plane of the flange. That point, Paul has named 'A or B' in his image. I use 'A or B' as the moving point along the horizontal green line.
This is simply an example of two peoples' explanation differing, while neither is wrong.
I have points A0, A1, A2, and A3 at the round end, as Paul does. However, there are corresponding points directly below, on the plane of the square which help form the right angle to each of the triangles.
As usual a picture paints a thousand words, thanks to Telly Savalas.
Posting to show triangulation and failing to show any triangles.
After a little PMing, Paul G has kindly allowed me to make a point I felt was missing.
If you know, you know, but since Ben88, and any other learner who stumbles on this thread, may need this to make Pauls' fine explanation fall into place.
Paul is using triangulation to discover the true length of A0, A1, A2, and A3 in his first image. That is, those lines A0-3 are the plan view of a triangle, the height of which is VH and the base of which is on the plane of the flange. That point, Paul has named 'A or B' in his image. I use 'A or B' as the moving point along the horizontal green line.
This is simply an example of two peoples' explanation differing, while neither is wrong.
I have points A0, A1, A2, and A3 at the round end, as Paul does. However, there are corresponding points directly below, on the plane of the square which help form the right angle to each of the triangles.
As usual a picture paints a thousand words, thanks to Telly Savalas.
Posting to show triangulation and failing to show any triangles.
CRB
Member
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- 2,897
To CRB. I'm back. Got into that safe. It was empty.
If those of us that know how to do it get in a mucking fuddle what chance have the others got?
Good and proper.
