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  #11  
Old 11-06-2012, 10:10 AM
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Kerry Pinkerton Kerry Pinkerton is offline
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Based on the various discussions on sweeps over the years, this is what I THINK I know....not necessarily all the truth...I'm not sure there is a single truth regarding sweeps.

1- Many sweeps are based on 1/8" rise at the center of the CHORD.

2- Some sweeps are based on 1/16 rise.

3- Some are based on whole number radius which could equate to a strange fraction for the rise from the chord.

4- It really doesn't matter because you are going to be using them in YOUR shop.

5- If you are going to be exchanging sweep with other folks, it might be important for everyone to have a common sweep design.

r = (m² + ¼c²)/2m where C is the length of the chord (straight line from one corner of the sweep to the other) and M is the height .

For instance, if my math is correct, if you have a 36" chord with a 3" height, the formula would be:

R= (1296+2.25)/72 = 18.03725

The same height on a 72" chord would be:

R=(5184+2.25)/144 = 36.0156 which is for all intents and purposes twice the radius. I probably did the math wrong but you get the idea.

I got my sweeps from Gary Hegel. They are 36" and are 1/16 rise between each of the 50 sweeps.
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  #12  
Old 11-06-2012, 10:15 AM
RockHillWill RockHillWill is offline
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I just found this on Fays sight:

a) Sweeps: It varies in numbers of pieces depending on the set, up to 85 pieces. The radii go from 7200" to 42". These are now available in anodized aluminum or aluminum-clad plastic.

I would be intersted in contact info for Gary.

The 1/16" rise in height makes sense.
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  #13  
Old 11-06-2012, 03:46 PM
Mike@rx Mike@rx is offline
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I bought a set of sweeps from here:www.andywiltshire.com .They are 2.5 mm laser cut stainless steel, 4' long and 26 in the set. I use them all the time and am very happy with the quality and price - 400 British pounds, but that was 2+ years ago. I don't see them advertized on his web site any more but could be worth sending an e-mail to see if he still has some.
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  #14  
Old 11-06-2012, 06:13 PM
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Quote:
Originally Posted by RockHillWill View Post
Tom:

Does that mean that if you hold up the sweep on its ends, that the number of the sweep indicates the number of '1/16's' that is measured at the center of the curve in the middle?

How does that relate to the longer sweeps? Would a #1 (1/16") as measured on a 36" sweep be equal to a #2 (1/8") height on a 72" sweep? Their curves are the same radius.

Mine are 36" long and 1/16 means 1/16" rise in the center as for the 72" units I???????????
Tom
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  #15  
Old 11-06-2012, 06:28 PM
Ken Hosford Ken Hosford is offline
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I took a different route I figured that What I needed was a way to make my own. So when does a radius gauge become a sweep ? Really what I needed was the ability to make my own any time any radius. Now there is a lot of high dollar answers to this , like , laser, water jet. Not having the funds for those dreams I bought a circle and ring shear . Now with out modifications it supposed to do 30 in. radius . But I see no reason I cannot stretch it . I mostly do motorcycle work so the 30 in has not been a problem yet . My need are as often a 13 1/2 radius a 14 is not even close nor is 13 . It has the ability to flange with different dies .
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  #16  
Old 11-06-2012, 07:16 PM
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To make sweeps.... I dont believe the old coachmakers had laser cutters, waterjets and the internet. They did have bandsaws and measuring devives and string or wire. Set out a point and tie a wire too it, Measure out 36 inches or 72 feet, stand on a piece of plywood or acrylic, wrap the wire around a marker and strike an arc. Then march over to the bandsaw and cut out your own sweep. An afternoon will make quite a pile of them.

How accurate do they need to be? If you can smooth a fender...you can block sand the sweep smooth.
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  #17  
Old 11-06-2012, 07:20 PM
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If anyone would like a set of maple or birch sweeps; PM me and I'll cut out a set.
You tell me what a set is, what sizes you would like. I'l shoot you a price.
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  #18  
Old 11-06-2012, 11:36 PM
Essexmetal Essexmetal is offline
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As stated above as long as you are using the sweep internally to check work or build a buck it does not matter. The sweeps I worked with in my body build days were 60" long and had a rise of 1/8" in the center. This was a true radius and the number on the sweep was a multiple of that 1/8". A #4 sweep was a 1/2" rise for example.

Most body drawing at the time were non dimensioned, scalable 1:1 layouts. In some cases the designer would call out a sweep number or combination if it was a rapidly changing shape.

They were made from master templates and cut on a large table pinrouter. Same method used to blank multiple aircraft parts, very exact and great edge finish. Most sets of sweeps that were around had two radius' per sweep, if I remember even number concave, odd number convex. This was fine for the guys working on the drawing board but was a problem for the clay and the fab guys. If the concave edge was what you needed but the convex was the radius you needed, you would have two choices, check the inside of the panel (if accessible) or scribe some lucite and create a template of the required radius. Brian Hainer ran some sets years ago and I suggested he make some 30" long units of the same radius on both edges. They get used the most.
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  #19  
Old 11-07-2012, 11:14 AM
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someone with the ability to make them should set up a group buy.
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  #20  
Old 11-07-2012, 01:29 PM
David Gardiner David Gardiner is offline
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I found this chart for true radius sweeps as used in the auto industry.


http://www.rivercityrollform.com/docs/sweepchart.pdf

May be of some help.

Oh and if anyone understands how it works - explain it to me...

David
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Last edited by David Gardiner; 11-07-2012 at 01:39 PM.
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