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Old 05-19-2008, 07:20 PM
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Need some math help.... sheetmetal cones

I am trying to figure out how to cut a flat piece of sheetmetal and turn it into 1/2 a cone to make the bellhousing cover for the transmission tunnel. It's complicated by the fact that the floorpans are angled where the sheetmetal will attach. My problem is figuring what diameter to base the circle so when I roll the sheetmetal the ends are 90 degrees to the floor - parallel to the firewall (so a rolled piece of sheetmetal for the driveshaft tunnel will mate right up and I won't have to cut wedges for the firewall/trans tunnel). Since it's a partial cone that will attach to an angled floor (due to the transmission getting wider and taller), the math to calculate this is beyond me.

I've tried to "wing it" with cardboard, but it's been less than successful. ANy help is appreciated.
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Old 05-19-2008, 07:35 PM
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I feel your pain... I use chipper board or poster paper. its fairly easy to cut the shape that will clear the top of the tranny. Then use masking tape to attach all the different angled pieces to it. Its alot easier for me to do one piece at a time and tape them all together to make one pattern. Opposed to tring to make the pattern out of one piece of template paper. Heck, most of my patterns are 95 percent masking tape. Im not sure if this helps or not? Make it as easy and as simple as possible, then tell every one you did the math... Ive got the formulas if ya really want them? GOOD LUCK
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Old 05-19-2008, 07:48 PM
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Imagine a funnel,without the spout,sitting upside down on your workbench. As you look at it from benchtop level what you see is the profile Project the two sides up until they meet. Use this point as a center and strike two arcs at the top and bottom of your funnel. Working off the vertical centerline of your funnel, using a pair of dividers, step off 1/4 of the circumferance on each side of center. This should give you a half pattern. Make it out of cardboard or pattern paper first. This is the quick and dirty method but it works well. Dave
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Old 05-19-2008, 09:53 PM
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Quote:
Originally Posted by Metal Twister
Heck, most of my patterns are 95 percent masking tape. Im not sure if this helps or not?
Now that's FUNNY.

I too, feel your pain.
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Old 05-19-2008, 10:33 PM
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Slomotion, that's why you make cardboard templates! Just cut them up and tape them together and throw away a pile of rough trys until you have what you want.

Brian
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Old 05-19-2008, 10:46 PM
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Actually Martin's right, Might try a Scotch and Water. It seems to work wonders for me on these long, tetious tasks, it slows you down to the perfect sizzor and tape speed... dull nosed sizzors!
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Old 05-20-2008, 01:56 AM
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Try this, I just sketched it out quick.
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Old 05-20-2008, 05:34 AM
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Quote:
Originally Posted by malc
Try this, I just sketched it out quick.

There is a way to make a real pattern.. We were taught this stuff in freshman year in drafting class...that was 1964...i forgot

There MUST be that info on google somewhere, but no clue on the "search words". I recall it was pretty easy and all you needed was the OD, ID, and length of the funnel. We did this on the large sized drafting paper at our desks, then we had to cut them out to see if we got it right.
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Old 05-20-2008, 05:41 AM
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What I drew is the way to do it, he wants a truncated cone.
Once he has the basic shape he can mess with it a little and tune the
raggy edges.
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Old 05-20-2008, 05:49 AM
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Quote:
Originally Posted by malc
What I drew is the way to do it, he wants a truncated cone.
Once he has the basic shape he can mess with it a little and tune the
raggy edges.

That sketch reminded me of the way we did it in school, except there were "radial" lines like spokes in a wheel. We did do that exact type of cone work for heating ductwork. I know it works, but I can't recall how
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Old 05-20-2008, 06:49 AM
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Complex but you´ll get the idea.
The radial lines would be for complex cuts on a cone or whatever.
Now, will it fly ?
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Old 05-20-2008, 10:54 AM
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Quote:
Originally Posted by malc
Try this, I just sketched it out quick.
That's what I was after.... I had the basic shape, but how to calculate it was escaping me. My brain works better with pictures.....

Thanks for all the info! Hopefully there'll be a picture of the progress soon!
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Old 05-20-2008, 01:18 PM
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From sheetmetal world..http://search.sheetmetalworld.com/news/articles/198.cfm

This is for a full cone so you would need only half for your trans tunnel..Suggest you layout on a poster board first to get the hang of this..once you have practiced then you can get to the point where you can do this directly on the metal..

Sam
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I have tried most all of it and now do what is known to work..
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Old 05-20-2008, 11:00 PM
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Thanks MALC the picture worked! I made a template out of matte (?) board and transferred it to the sheetmetal. I can't believe how well that worked (especially with my measuring). Take a look at the semi-final product. It came out better than I had hoped the very first attempt!

I greatly appreciate the help, thank you for all of it!
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