Tetra Math

[tkwetzel]

Originally Posted by HPA_Robotics_13

I thought that the tetras used at the actual competitions don't have PVC endcaps but instead have flat pieces that screw into the PVC?

The small tetras have flat clover pieces that screw into the end caps attached to the PVC. The goals are aluminum and will have a angled piece of hardware holding them together. These pieces are visible in the field drawings available on FIRST's documents page.

[Aignam]

Originally Posted by tkwetzel

The small tetras have flat clover pieces that screw into the end caps attached to the PVC. The goals are aluminum and will have a angled piece of hardware holding them together. These pieces are visible in the field drawings available on FIRST's documents page.

In addition, a good picture of these pieces can be located here.

[Lucid]

anyone know what the angle is between faces? I drew a tet in AutoCad and I measured it to be 55 degrees, but I think there is something wrong with this.

Lucid

[Grommit]

The angle can be calculated by looking at a cross section of the tetra, giving 2*arcsin(1/sqrt(3)), which is approximately 70 degrees.

[Leav]

Originally Posted by Grommit

The angle can be calculated by looking at a cross section of the tetra, giving 2*arcsin(1/sqrt(3)), which is approximately 70 degrees.

I got a much simpler expression: cos^-1(1/3) whuch equals 70.528779365509308630754000660038



I love math, algebra and trig

me = nerd

[unapiedra]

Originally Posted by Greg Needel

if there is a tetra ontop of the goal then you can only fit 4 under

Why that? Does the tetra ontop block that?

[sojouner06]

think about it here, 6 inches, thats half a foot. Even with end caps at the largest constraint is 4 inches. It is physicaly impossible for it to be a six inch increase per tetra. IMPoSIBLE!!!!!!!!!!!! unless someone put it on a freaky way

[ZZII 527]

We've also built tetras...it is 6". The sides of one tetra do not even come close to being flush up against the sides of the one below it. I think it is partially because the sides of the lower one get jammed into the corners of the one on top.

[Twstdkittie]

Originally Posted by ZZII 527

We've also built tetras...it is 6". The sides of one tetra do not even come close to being flush up against the sides of the one below it. I think it is partially because the sides of the lower one get jammed into the corners of the one on top.

Exactly. It really is 6".

[rangersteve]

I wish i had seen this thread sooner. I had to do this math today but oh well i like math. Nice thread.

[sojouner06]

ok i believe it is 6 inches, but wait, how thick are your pipes. The manual said they should be 1 and a quarter inches at pipe and 1.(4-9) inches at endcap

or...maybe...how long are the pipes themselves? 40"? 48"? 70"?

[sojouner06]

http://www.ifirobotics.com/first-2005-field-parts.shtml

look here for the parts first wants you to get

[tkwetzel]

Originally Posted by sojouner06

http://www.ifirobotics.com/first-2005-field-parts.shtml

look here for the parts first wants you to get

With the correct parts, the tetras will add approx. 6" each to the height of the goal when stacked.

[sojouner06]

ok, it is 6 inches, but i am still baffaled! how can the formula i used be wrong???? what could be an outside influence to change the height so drastically...

[ZZII 527]

To clarify angles a bit:

The angle between a face and an edge is ~55 degrees. The angle between two faces is ~70 degrees.