Triangle measurements on model don't match physical finished product

I’m very new to SketchUp and apologize in advance if this is a stupid question. I’ve tried searching a few terms for a solution, but am not really sure where to even start.

I am designing a go kart frame for my son. I am also making a wooded mock up of the frame to make sure everything works before cutting the steel. It is all very simple components, 1.25 square stock.

I added a brace that created a right triangle. The angles are C) 90, A) 20 B) 70. The SketchUp model shows the inside measurement of side a) 7 9/16 b) 2 3/4 c) 8 1/16.

When I actually cut the pieces and put it together, all the angles and side b matched, but side a was 8 /14 instead of 7 9/16 and side c was 9 5/8 instead of 8 1/16.

I am sure that I drew something wrong to get this outcome, but cannot figure it out. I opened a new file and drew another triangle with the same angles and side b measurement, but input the side a and c measurements that I had on the actual physical mock up. The lines intersected at the same distances as on the original SketchUp model, then extended out to the legnths that I got when I actually built it.

Any help figuring why I am getting this discrepancy on triangles would be greatly appreciated. I have had no issues with measurements for squares or rectangles.


Mathematically C should be 8 3/64 and the angles are not exactly 20 and 70, just under 70 and over 20.
A right angle triangle in sketchup is a rectangle with a diagonal, pretty hard to get wrong if you have the two dimensions of the rectangle. A and B

So my guess is you have possibly made the angle on your physical construction incorrectly.

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Just led in bed thinking about getting up, but looking at this instead on a lovely UK sunny morning :grinning:

If b is 2.75 and the angles are 90, 70 & 20 then simple trigonometry says a = 2.75/tan 20 = 7.555 and c = 2.75/sin 20 = 8.041

I would guess you need to changle your measurement units to decimal and maybe to .1 mm accuracy.

Best of luck with that go kart for your son - your project sounds great :+1:

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You figured it out for me. When I drew the triangle I was building it off a 70 angle to make a right triangle, so my very basic math skills left me thinking 70/90/20. I tried cutting the mock up material at those angles, but as you can guess my craftsmanship is on par with my math, haha.

I used the measurement I came out with on the physical model for horizontal and vertical then connected the end points in SketchUp to make the triangle as you mentioned. After seeing the three angles then I realized I messed it up cutting. I thought it would be easier to draw, and cut the triangle with nice even angles, but now realize I need to draw and cut for side measurement.

Thanks for the help, it was driving me nuts. I’m a rank novice at this design and fabrication stuff, lots yet to learn.

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