Chassis Radius bend question

[bdllab]

I am in process of starting a new chassisbuild. The blue prints for the chassis call for 6 inch radius bends using 1 5/8tubing . The bender I will be using has a 7inch radius. Does anyone know offhand if just adding to overall length of the tubing. Starting bends ½ inchsooner will obtain the proper finished result ? I also was thinking of maybere-drawing the print to scale to check design. Any thoughts ?

Thanks John

[aametalmaster]

1/2" won't be enough. You need to use Pi 3.1416 to see how much you will need to add. Drawing it out on paper will give you a good idea...Bob
http://science.howstuffworks.com/inn...riments/pi.htm

[aametalmaster]

You will be .788 short on a 90* bend and if you were to bend a circle it would need to be 3.152 longer...Bob

[aametalmaster]

One other thing is that most tube dies use a centerline radius so your circles (or 90's) will be bigger than the 7"...Bob

[bdllab]

Thanks Bob
The prints call for a 6" die radius . Most standard tube bender die I amfinding are 7" I believe I saw one from JD Squared that is 5.5 on 90. Looks like I’ll be drawing!

Thanks again
John

[Vegas Racer]

The die selection depends on the bender you are using. JD2 has sizes in that tubing range at 5.5", 6.5" and 7.5" CLR. JMR and Baileigh both offer 6" CLR dies.

What bender are you using?

[FernTJ]

I am in process of starting a new chassisbuild. The blue prints for the chassis call for 6 inch radius bends using 1 5/8tubing . The bender I will be using has a 7inch radius. Does anyone know offhand if just adding to overall length of the tubing. Starting bends ½ inchsooner will obtain the proper finished result ? I also was thinking of maybere-drawing the print to scale to check design. Any thoughts ?

Thanks John

For a 90 degree bend the 7 inch radius will start 1 inch closer and end 1 inch farther. If we are talking center line the 7 inch radius will use about 1.6 inches more tubing in the bend and 1 inch less for each straight leg for a net change of about .4 inches less tube. The larger radius will cut across the corner more so if the original 6 inch design counted on having room for something inside the frame it may not fit with the different radius.

If there is a tolerance on the print follow it. If not tell the customer that your standard radius tolerance is plus or minus 1 inch

[Randy Forbes]

Most bender/die manufacturers will supply a die to the radius you want with little or no upcharge. If they already offer a 5.5 & 7" die, it's no big deal to cut one for a 6" radius.

Mittler Bros. did one for my "small" tube hand bender (I'd like to get a nice selection of various radius dies for my Pro Tools one-shot, but $$$...).

[walker]

Here is a link to an easy method for figuring out bends on your own bender that is accurate and easy.

http://www.pirate4x4.com/articles2/tech/bendin_tube