Bridle Problem

[Grom]

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, Grom

[jurjen_barel]

Ouch, here comes a lot of old math from high school.

Just a little suggestion? How about having a known value for the height of the bridle itself (height between the beams and where the legs come together)? That would make the equation so much easier.

V1 and V2 are pretty useless, unless you also know the height between the bridle and the floor.

[Grom]

Hello Jurjen

No, no trim height.

We know only v1, v2, h1, h2, and bridle angle

otherwise i'd be ashamed to ask ....

[Gast1401081]

Paul Pelletier - Download LD Calculator

no worries, don't try to invent the wheel again.

[ostracized]

That doesn't sort out the problem because he is missing a value: either trim height or an angle versus horizontal or vertical line. (nice program though...)

I think you should imaginary extend line D2 to the upper right, intersecting with a imaginary line horizontally from the left beam. Thereby you get another triangle with width [H3] and height [DeltaV]. Then you can calculate the angle which D2 makes compared to the horizon and from thereon it is easy.
EDIT:
[img]http://www.stage-support.nl/fotos/groot/bridle.JPG[/img]

now just how to get value H3... (I'll come back to you when I think of a way to do that) (damn haven't got a scientific calculator with me)

gr Otto

[Grom]

Hello,

@ MacGyoverSounds;
eh, kplus hm, ... I am very familiar with LD, it is really nice, but I am making my own, rigging oriented only. Plus, LD has no such function...

@ ostracized
Please, do find your calculator and run those numbers, I am looking forward for the whole thing. I must admit, I do not understand your theory of yours, hope for more.

Thank you all for quick repla

[MPA]

D1 = H1 / cos [angle 1]
D2 = H2 / cos [angle 2]

Correct me if i'm wrong.

[Grom]

D1 = H1 / cos [angle 1]
D2 = H2 / cos [angle 2]

Correct me if i'm wrong.

I am not correcting anything or anybody...

The known parameters are v1, v2, h1, h2 and bridle angle.
We do not know angle 1 and angle 2.

[laserguy]

We CAN however calculate the height of the bridlepoint (H) from the bridle angle (B)

This results in the following formula if I did remember my trigonometry well:

- tan(B) = V1H2-(H1+H2)H+V2H1 / H1H2-V1V2+(V1+V2)H-H^2
All parameters except H are known, this means we can calculate H from out this formula. Once we have our H, we have two rectangular triangles of which both rectangular sides are known, so we can easily calculate everything we want...

[Grom]

Hello Laserguy

So your formula is for distance between floor and bridle junction, named H?

let say
v1 = 8
v2 = 12
h1 = 4
h2 = 3
bridle angle (B) = 100 degrees
_______________


- tg 100 = (8*3 - (4 + 3) * H + 12 * 4) / (4*3 - 8 * 12 + (8 + 12) * H - H*H

I calculated twice, but I cannot get H...
(72 = H*(165.79 + 5.6712*H))
Could you kind give me example?

[laserguy]

Dear Grom,

this long formula reduces to (rounded some values and -5.67=tg100)
-5.67*H^2+120.4*H-548=0
This function has zeros for two values: 14.63 and 6.61
As H should be lower then V1 and V2, the first solution is dropped and we keep: H=6.61

[Grom]

Beloved Laserguy,

I just tried couple of examples. I believe this could be it. Your trigonometry is excellent.
I will run some more examples tomorrow and hopefully confirm (what you already know, right?) your modest input, my so desperately needed break through.

[Gast1401081]

Hello Laserguy

So your formula is for distance between floor and bridle junction, named H?

let say
v1 = 8
v2 = 12
h1 = 4
h2 = 3
bridle angle (B) = 100 degrees
_______________


- tg 100 = (8*3 - (4 + 3) * H + 12 * 4) / (4*3 - 8 * 12 + (8 + 12) * H - H*H

I calculated twice, but I cannot get H...
(72 = H*(165.79 + 5.6712*H))
Could you kind give me example?

(72 = H*(165.79 + 5.6712*H))
5.67H² +165.79H -72 = 0
>> H= -11 V H= -18,6
\
negative figures, somebody has done somew wromg math.


Unless some newstatements I need to get back to my oldschool Maths, to find the Cosine-rules etc back again.
Edit
Make things easier, and don't ask for the bridlepoint height. Adjust V1 and V2 until H1+H2 is at your basepoint. The new riggingpoint most likely wil be a climber, or so.
\
then tan(a1)= H1/V1new, meaning that cos(a1)xH1 = D1
then tan(a2)= H2/V2new, meaning that cos(a2)xH2 = D2

[laserguy]

Dear Grom,

thank you for the compliment .
If I did not make any algebraic mistakes I do believe in this formula, I think .
Good luck!

[Grom]

Hello

@ ********
no shit! I calculated wrongly? he he I guess shit happens

@ Laserguy
I just run another example (singing: oh, I just can't get enough).
It did the trick again, so...
You pulled that formula out of your head? Hell,...