Hello
Sorry, this thread will be in English
I want to add a new feature to my rigging software, but I can not make the formulas. It is about bridle, and I would appreciate your help.
We know left and right vertical height (from floor to beam).
We know left and right horizontal lengths (from beam to load, from load to beam).
We know bridle angle.
What are bridle legs (lengths)
here is the picture for better understanding.
Thank you,
Kind regards, Goran
edit: deleted - because of unknown alpha-angles
You're welcome .. and best regards.
Martin
hi,
do we realy know alpha 1 & 2?
Because of the altitude difference between V1 and V2, it issnt possible to deduce directly from the bridle angle to alpha.
Edit says: Have found an answer without using alpha. but its a little bit komplicated. but i will try to announce it.
hi,
I have now found an answer.
it is a a little bit complicated, but possible.
I can't promise that it also works for D2 as I simply used D1 for deducing without retesting it on D2.
We know left and right vertical height (from floor to beam).
We know left and right horizontal lengths (from beam to load, from load to beam).
We know bridle angle.
why don´t we know bridle height ?
Hi Goran,
i think, it's not possible to get D1 and D2 with the given arguments. I tried it with trigonometric functions and every time i get an Equation with 2 unknown variables. So i think you need one more variable - please correct me, if i'm wrong...
In practice, is it possible to get the height from bottom or from the top to the bridle point?
gast: I cannot follow your Calculation - too many variables, wich are not defined... You can send me a personal message, too, i'm interested in...
I can not follow Gast's calculations, too.
gast: Please specify all variables, you have used, in your picture.
And I can not understand, why the bridle-angele is known an the distance from ground to bridle-point is unknown.
In practise:
- you know the distances / location of points (vertical and horizontal)
- you calculate the bridle-legs
- you check the angles and and forces
- if there are to high forces or "bad angles", you have to change the bridle-leg-lengths (the bridle-point moves down)
You have to know the height of the bridle-point.
best regards,
Martin
hi,
its not easy to explain.
because i dont know the technical terms for the used formulas for translating.
the used basics are:
- centric dilation
- the ratio of H1 and H2
G and K are only factors for an easier arithmetic in the following steps.
but i can surely say, that the terms for D1 are right.
for D2 i can´t promise but i will check this later.
Edit knows: the formulas are correct.
if V1 < V2 , D1 and D2 are negative, but have the right length.
Hi Goran,
can you please explain, how he get this? I'm interested to understand that, because I'm positive 
Thanx
Hi Goran,
can you please explain, how he get this? I'm interested to understand that, because I'm positive
Thanx
Hell, ok, here it is;
v1 = 8
v2 = 12
h1 = 4
h2 = 3
Bridle angle = 100 degrees
______________________
X = from floor to bridle junction (where d1 and d2 meets)
- tan(Bridle Angle) = V1H2-(H1+H2)X+V2H1 / H1H2-V1V2+(V1+V2)X - X^2
5.67128 = (8*3 - (4 + 3)*X + 12*4) / (4*3 - 8*12 + (8+12)*X - X*X)
5.67128 = (24 - 7*X + 48 ) / (12 - 96 + 20*X - X*X)
5.67128 = (72 - 7*X) / ( -84 + 20*X - X*X)
72 - 7*X = 5.67128 * ( -84 + 20*X - X*X)
72 - 7*X = -476.38752 + 113.4256*X - 5.67128*X*X
72 - 7*X + 476.38752 - 113.4256*X + 5.67128*X*X = 0
548.38753 - 120.4256*X + 5.67128*X*X = 0 ; so:
5.67128*X*X - 120.4256*X + 548.38753 = 0
______
Now, I don't know how this method is called in English, less in German, but it is also high school. we have power function, so we will get two results. one will be wrong, for our case, but mathematically they are both correct.
here is the formula:
x1 = (-b + square root of D) / 2a
x2 = (-b - square root of D) / 2a
where
D = b*b - 4*a*c
and
a is coefficient at second power operator (in our case 5.67128)
b is coefficient at first power operator (in our case - 120.4256)
c is linear operator (in our case 548.38753)
So:
D = 14502.32513536 - 4*5.67128*548.38753
D = 14502.32513536 - 12440.2369245536
D = 2062.0882108064
x1 = (- (- 120.4256) + square root of 2062.0882108064) / 2*5.67128
x1 = (120.4256 + 45.41022) / 11.34256
x1 = 165.8358 / 11.34256
x1 = 14.620669 so, this is wrong, since it is higher than at least one vertical.
x2 = (120.4256 - 45.41022) / 11.34256
x2 = 75.01538 / 11.34256
x2 = 6.613
Alas, from floor to bridle junction is 6.613. Now we can easily get triangles sides and calculate forces.
Hope this is understandable
we have power function, so we will get two results. one will be wrong, for our case, but mathematically they are both correct.
I think you mean the "p-q-Formel", so the german name
for the next time, download "LD Calculator" .....
with best regards..
Marcus
