# A couple of helical gears

I designed this couple of helical gears with NURBS. I didn’t use calculations (except a bit) but created them with an intelligence method that I usually use in most of my designations (a part was visually). I drew two intersected circles in an appropriate place so that the teeth of the two gears to be equal. I trimmed the lines of the two circle in the intersection place and then drew the tooth of one of the circles. I replaced the other circle in a straight path and then copied the tooth of the first circle and attached to the second. Then I calculated the root of the tooth and the perimeter of every circle and then used polar array according to each circle perimeter. Thus I created the base sketch of the gears. After these stages, I used rotation ( copy was active) and drew the bottom of those gears with different angles. Then I picked up the first circles and connected with four lines to the lower circles. I used polar array again and reproduced the necessary lines around the teeth of each circle. Then, I used network of curves and made the surfaces around those gears. At the end I used cap and other works such as engravings.

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Nice exercise. Although I’m not convinced the teeth are helical - they look like they are twisted straight teeth. And you could also crown the teeth, done to reduce wear and noise.

Looking forward to seeing mk2 of this!

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You are right, sir

Crowning the teeth can reduce contact surface and a couple of matched gears can work smoother and more soundless. Also, the two sides of the tooth will be not worn due to having not any contact.

before I design those gears I searched google for helical gears and found this picture at the top of the first page and that ensured me it is a type of helical gear, though such the gears with twisted curvature shapes of teeth are called helical gear, as well. Is it right?

I will try to redesign the gears again based on your recommendations

Thank you

Hi, Jeremy

I changed the straight teeth into an arcuate shape