Minimum Radius - PT Systems

RE: Minimum Radius - PT Systems

Seth Guthrie — Thu, 25 May 2023 17:11:15 GMT

I can't be totally sure how RAPT calculates this, but your last image looks like a parabola with a flattened top which differs from our assumption. Here are the calculations for your 9 m example.

Variable	Value	Units	Comment
L	4500	mm, in	from A to B (half-span)
x	0	mm, in	from A
i	0.2		inflection point ratio
iL	900	mm, in
a	0.000218272	1	parabola coefficient (x before IP)
b	5.45679E-05	0	parabola coefficient (x after IP)
Ya	942	mm, in
Yb	58	mm, in
P	884	mm, in

y'	0		parabola slope
y"	-0.00043654		parabola curvature

r	-2290.72398	mm, in	parabola radius of curvature

And here's the output from the CalcLog confirming the same value:

RE: Minimum Radius - PT Systems

Durga Malla — Thu, 25 May 2023 03:10:03 GMT

Thanks Seth for the prompt response.

Assuming 2500mm radius with 10% inflection point ratio, now the results should match, as in no "radius error" from RAM Concept should occur right?

I just want to understand if both software are using 2500mm minimum radius why one is giving error and the other is not?

Thanks Mate

RE: Minimum Radius - PT Systems

Seth Guthrie — Wed, 24 May 2023 15:31:53 GMT

The placement of the inflection point (inflection point ratio in Concept) is one thing to check. Here are two clips from the manual about that.

Your other suggestions seem helpful. We are looking into some possible tendon detailing improvements in Ram Concept, or through the iTwin, and I'll pass along this to the PM.