Help understanding angles for tube notching
 

Hello all, Thank you for reading and helping!


I am having hard time understanding the online notching calculators.

Most calculators present the following:

Diameter of cut tube: This is ok

Wall Thickness of cut tube: This is ok

Diameter of parent tube: If I understand correctly this is the tube that I won’t be cutting.

Angle: I don’t understand what value to use here, for example: The HeadTube is at 75 degrees to horizontal and the TopTube (The tube I want to cut) is at 30 degrees to horizontal ?

Offset: I don’t understand what offset is and how to use that parameter ?



Thank you very much,

Tom

Parent tube is the uncut tube. Horizontal doesn't matter. You need the angular relationship between the two tubes. Most frame design programs will give you those angles.(I use RattleCad) Offset is the distance from the centerline of the tube and will provide an off center miter. Most tube miters have a zero offset. Offset is helpful for things like moving the seat tube forward on the bottom bracket to provide more tire clearance. I also offset miter my chainstays to make them lower on the bottom bracket for ease of welding and to prevent them from contacting the seat tube.

That's interesting. The only ones I offset are the seatstays where they join the ST, otherwise they would intersect each other. Never thought about offsetting chainstays or or the ST to BB.

Thank you very much for the answer.

I understand now the parent tube and the Offset.
About the angular relationship i am attaching a link for an image, is that what you meant and if so. what angle i should go for ?

photos.app.goo.gl/3BStSXneAPLUSTvM6

Thank again,
Tom

For the angle I would suggest experimenting with your 76.67 degree top tube joint, printing out and fitting it up to make sure it looks right. You may need to use the 103.33 angle instead. Some programs start the 0 degree at the top or the bottom (for lack of better reference), This is a situation where having it in hand really helps.

Thank you very much for your help!

Tom

I don't think it will matter. If it labels top or bottom, they will be upside-down if you do it wrong.

These offsets can be helpful when fillet or welding to avoid overlapping tubes. Thus one can construct the joint one tuba at a time and/or insure a tube's complete diameter is contacting the BB shell, Andy

Yaa, i didnt think about that ! :)
Thanks/

Thank you all for sharing the knowledge and helping.