Slip Rolls & Cones.

[JetSet]

Hello again.

Today I picked up by brand new (read really old) squaky clean (read greasy) shiny (read not shiny whatsoever!) slip rolls. Whoooo!

Definately not a flimsy chinese import, this beast weighs a ton, 2 of us couldnt lift it, ended up dismantling it to get it off the truck ). 36 inch rolls, open up to 10mm-ish (lovin the impreial/metric consistency eh!?)

Anyhow, although its a really simple tool, I cant seem to work out the 'propper' way of using it.

I have it positioned so the single unpowered bending roll is at the front so I have access to the big knobs to change the angles. The 2 moving rollers are at the back. This means the sheet will be pulled over the redundant roller to be bent rather than pushed over it. Is this the best way?

I am fine rolling tubes, everything is perpendicular etc. The problem is cones. I cant picture how they should be rolled. I keep ending up with a spiral, or a near-cone, with a bit of a spiral, or bit of it not quire right. This is ok for smaller stuff where I can alter it manually, but I would like to get it just right for when I come to roll a 1mm sheet of SS for a lockwood intake for example.

Any hints/tips?
Thanks.
JS.

[Johansson]

When I made the tail expansion cone for the Bent Chineese I used slip rolls, and found that the only way to get the ends of the cone to meet where they should was to yell and shout until someone got tired of hearing me screaming and come to my assistance. Then I told him to do the cranking while I adjusted the sheet so the upper roll allways was in line with the radius of the cone. It turned out just fine, except for the fact that I cut some corners in the calculations and had to "modify" it with a hammer to fit on the tubes...

//Anders

[JetSet]

Ah thanks, I think I can picture it now. Basically the wide bit of the cone will need to go through the rolls faster than the thin bit.

Cheers.

[Fricke]

Yes You are right.

And don´t forget to pre bend the ends of the sheet.

I think it´s better to have the sliproll setup so that the sheet is driven against the backroll.

[kid jansen]

Aren't there rollersets on the market with conicalshaped rollers?
With rollers almost everything should be possible with shaping sheet metal. Just check out what they do in custom car manufacturing.
They make wings, fenders and sidepanels just out of one piece of sheet metal.

The thing is that the roller for the outside of the tube should either be larger or make more revolutions than the roller for the inside part of the tube. And for cones the roller must have a larger diameter where the cone has a larger diameter. The problem is that you would almost need a different set of rollers for each cone.

That wouldn't be a big problem is you plan to make only one type of engine, and make a lot of them. But with different (sized) engines you would need a lot of rollers.

So I guess it is nearly impossible to make every cone perfect with just the slip roller.

By the way, the rollers they use in custom car manufacturing useally has a very large 'wheel' (say 10-15" diameter, and 4" wide) and a very small 'wheel' (about 2-3" diameter and probably less than 1"wide).
And somehow they can make almost every shape out of sheetmetal with that machine.

[Eric]

I think your thinking of an English Wheel. Not quite the same as a slip roll, more for smoothing the metal and complex curves.

Eric

[kid jansen]

Could be, but I don't know the names of such tools, certainly not the english names.

[Fricke]

Aren't there rollersets on the market with conicalshaped rollers?
With rollers almost everything should be possible with shaping sheet metal. Just check out what they do in custom car manufacturing.
They make wings, fenders and sidepanels just out of one piece of sheet metal.

The thing is that the roller for the outside of the tube should either be larger or make more revolutions than the roller for the inside part of the tube. And for cones the roller must have a larger diameter where the cone has a larger diameter. The problem is that you would almost need a different set of rollers for each cone.

That wouldn't be a big problem is you plan to make only one type of engine, and make a lot of them. But with different (sized) engines you would need a lot of rollers.

So I guess it is nearly impossible to make every cone perfect with just the slip roller.

By the way, the rollers they use in custom car manufacturing useally has a very large 'wheel' (say 10-15" diameter, and 4" wide) and a very small 'wheel' (about 2-3" diameter and probably less than 1"wide).
And somehow they can make almost every shape out of sheetmetal with that machine.

Yes some rollers have a conical upper roll... But usually there is a way to adjust the top roller by some screws to mace cones...

The trick to make cones on a "plain" roller is to advance the bigger diameter of the cone faster than the smaller diam...

I´m using a metal brake, to bend my cones... with the "right" amount of bends on the cone its almost round in shape... then if i feel that i need a round crosssection I´m using the sheet metal rolls to make the cone smoother...

Well I´ve seen sheet metal workers (their age is about 80 years) make wonders with just a roll and an anvil... =) All that needs is practise and a "feel" for the material...