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| weird results with a sine bar. |
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| wheeltapper:
Hi some time ago I showed a sine bar I'd made. http://madmodder.net/index.php/topic,8735.msg94914.html#msg94914 I've recently been trying to master basic trig and have been stacking various height objects under the bar and working out the angle, then checking it and I'm getting some weird results. It seems the higher I go the more the error increases. It's a 5" bar, the rolls are exactly the same diameter, the distance between centres is 5" to a tenth of a thou and the distance between the base of the roll to the top of the bar is identical at both ends. should be all right, not so. with a stack of 407.5 thou.( I miked various pieces to hand so odd sizes ) theoretical angle is 4.6 degrees, actual is 4.7. at 763 thou theoretical angle is 8.7, actual is 8.8. so far so good. 1509 thou theoretical 16.8, actual 17.6. oops. 1950 thou theoretical 21, actual 22.4. 2738 thou theoretical 28.7, actual 33.2. big oops. at 3" should be 30.9, actual 36.6. and at 4" should be 38.6, actual a whopping 53.2. What the hell is going on!!! If I'm doing something stupid please tell me because this is driving me nuts. cheers Roy. |
| BillTodd:
Is that 5"between rollers or 5" between the centres of the rollers? ( as it should be) Bill |
| wheeltapper:
Its centres, I did say that. on reflection I think I may be using the wrong formula and confusing myself. I never was any good at maths. :doh: Roy. |
| Fergus OMore:
Having been brought up on a diet of Euclid, I would guess that you have a crap mike! What you should be using is measurement tools of a known reliability- ie Jo Blocks. I might be wrong but ALL the details necessary are yet to be provided. Regards N |
| wheeltapper:
I just read this on a different website, "Limitations of Sine bars: Sine principle is fairly reliable at angles less than 15o, but becomes inaccurate as the angle increases." so maybe its not me? |
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