Spiral Formula?

[rsgpitt]

Hey ant, those holes are for every 90 degrees right? because they dont match up with my material. I lined up the first hole, and its more towards one inch than the 2.20 that your model said. Also do you have any other suggestions besides laser cutting. I tried a drill bit but it just tore the material. I was thinking a punch set.

[owl]

rsgpitt / Ant,

Wouldn't it be easier to go ahead and wind the stainless steel shim stock as if making the final product with pseudo washers in place with the correct spacing, and then band everything, then drill the holes at 90 degrees?
Then you could unband it, and wind the final assembly with the real washers in place.
I am very impressed with this "kettle design" and have the stainless steel in hand. Just waiting for an easier way to get the hole spacing right.

Thoughts?

[rsgpitt]

Thats a good idea, but i think it would be hard to keep the spacing while drilling, and it would be innaccurate. BTW what size shim did you get?

[AntDavison]

[rsgpitt]

D'oh, I cut it up into plates before you said this because i was gonna make a plate design when i was discouraged your numbers werent right. Like the old saying goes, measure twice, cut once. Oh well, I guess i can blow $21.62 on a nother roll of shim.

[AntDavison]

'Oh well, I guess i can blow $21.62 on a nother roll of shim."

>> everything is just so cheap in the states

.... my advise would be to make a template with a computer drawing program (i used an 8 year old version of CorelDraw) ... print it out on an inkjet printer , sprayglue, and make a mock up in cardboard or thin plastic sheet first, that will train you in the intricacies of that design .... 'cause there are a few

how are you finding the thinness of the 0.004"

[rsgpitt]

[rsgpitt]

[AntDavison]

[rsgpitt]

[AntDavison]

[thrival]

[owl]

[AntDavison]

in my posted script, the distance between mounting holes is calculated by summing lots of tangents, not 100% accurate, more like 99.9%; when i wrote the script i was more concerned about drawing the interleaved spirals into a bitmap .... any way, as the spirals increase linearly, its easy to write some code that is 100% accurate in calculating the inter-hole mounting distances

---------------------------------------------------

id = 23.749
spacing = 3.2766

turns = 3.75
plates = 2

decrement = plates * 2 * spacing
od = (turns * decrement) + id

lngth = 0


print "0.0mm = 0.0"

for z = (od - (decrement / 8)) to (id + (decrement / 8)) by (-decrement / 4) do
(
lngth += (z * pi / 4.)
print ((lngth as string) +"mm = " + ((lngth/25.4) as string))
)

_____________________________________



with your figures the 100% accurate pure maths method spits out the below


0.0mm = 0.0"
55.9672mm = 2.20343"
109.361mm = 4.30555"
160.181mm = 6.30635"
208.428mm = 8.20584"
254.102mm = 10.004"
297.202mm = 11.7009"
337.728mm = 13.2964"
375.682mm = 14.7906"
411.061mm = 16.1835"
443.868mm = 17.4751"
474.101mm = 18.6654"
501.76mm = 19.7543"
526.846mm = 20.742"
549.359mm = 21.6283"
569.298mm = 22.4133"


overall its 0.6mm shorter than previously quoted, so nothing significant in it really, with my 4 plate kettle, with 1069mm plate lengths, the pure maths method suggested a plate length of 1068mm, so the figures i used to constrct my kettle were 99.9% accurate

[AntDavison]