how to make mega's wth a kink in them

as i lost one of my mega's last month (and a lorry very kindly flattened it for me) i am going to make a new pair
Trouble is that the pevious set i made were modified so they were bend (kinked) in the conical part .I did this by making slots witch i then welded back up.This was because i already had made the mega's
as i have to start all over i would like to form those bends in steel from the begin
anyone knows how to do this?

this is what i mean

Contact a sheet metal fabricator. In the old days we'd lay it out with compass, ruler, etc. Now, a few mouse clicks will squirt out a program for the CNC plasma or laser cutting table. Weld up to suit. If you insist on doing it in your workshop the way you did before, just use a vertical band saw to cut out pie wedges, close up and weld, as before.

i like to do things myself , but then if i ring contact somebody perhaps that counts as doing something yourself
to be serious , making things is more the point than having them , for me

those pie-wedges is what i did the first time ,

lynxnsu said:

i like to do things myself , but then if i ring contact somebody perhaps that counts as doing something yourself
to be serious , making things is more the point than having them , for me

those pie-wedges is what i did the first time ,

Click to expand...

Laying out cat-eye shaped peices is a choice that greatly increases the weld joint length/count. If you are an accomplished TIG weldor, it can be made to look sexy, but if not, would look nasty/lumpy. Band sawing wedge shaped rings completely and rotating them is an option, but again, more joint length.

To lay out the peices, simply calculate the circumference where the joint is to happen (both small and big end) and make two lines paralell. The calculate how much difference you want in the section, push the middle of those lines apart by the difference plus (for example) 1/4", which will be your narrow side. Move your ends of the lines aprt that 1/4". Unless you have a shear, plasma table, etc. it'll be cobby looking. The sawing completely and rotating will probably fulfill your dreams, I assume you'll be brazing based on the brass showing in the image?

Some manufacturers supply components for DIY.

http://www.coneeng.com/motorcycle_components.html

There is no simple way to make megas with smooth bends in them. Notice I said smooth. Cutting slots, or making individual sections and welding together, works fine, but isn't smooth looking. The only way I know of that you can do this at home is by hydroforming. Basically, You cut two curved sides out of sheet metal, bend the edges slightly so you can butt weld them, close off one end with a valve, and weld an adapter on the other end to which you connect a hydraulic pump. You then pump the mega up with hydraulic fluid or water, while judiciously tapping with a hammer to try to smooth out the lumpy parts. Lots of info on the technique here

http://www.eurospares.com/frame8.htm

Ken

concours said:

To lay out the peices, simply calculate the circumference where the joint is to happen (both small and big end) and make two lines paralell. The calculate how much difference you want in the section, push the middle of those lines apart by the difference plus (for example) 1/4", which will be your narrow side. Move your ends of the lines aprt that 1/4". Unless you have a shear, plasma table, etc. it'll be cobby looking. The sawing completely and rotating will probably fulfill your dreams, I assume you'll be brazing based on the brass showing in the image?

Click to expand...

thanks for the info,i can rather get along with a tig

no it will be tig welded , those welds were a repair when they sheered on the IOM

i was looking for a way to make 2 flat pieces , weld them together and then use watzer to form them
i have repaired bended mega's this way but never actually made them

lcrken said:

There is no simple way to make megas with smooth bends in them. Notice I said smooth. Cutting slots, or making individual sections and welding together, works fine, but isn't smooth looking. The only way I know of that you can do this at home is by hydroforming. Basically, You cut two curved sides out of sheet metal, bend the edges slightly so you can butt weld them, close off one end with a valve, and weld an adapter on the other end to which you connect a hydraulic pump. You then pump the mega up with hydraulic fluid or water, while judiciously tapping with a hammer to try to smooth out the lumpy parts. Lots of info on the technique here

http://www.eurospares.com/frame8.htm

Ken

Click to expand...

OOPS, i was too quick to answer one sugestion that i did not see the following one....

yes hydroforming is what i was looking for, but how does one form those curved sides on paper?
try to imagine them lying on the floor and you trampling on them , they will not go flat as one side is stretched by forming them
but i have not looked at the link ,lcrken , so before i go on , i look into that and look at the term hydroforming ,thank you



one of these bashed megas have been restored to (about ...)their original shape ,just to show how to do it But here again i started with existing items

What about some DIY wooden patterns and having them cast in iron ? At least that would keep the lorry driver's heads down when they came bouncing down the road at 'em - it should put their aim off !

If Ya seal with water inside can freeze to expand contours if it don't split the seams. There are 3D printers than use a SS powder that heated to melt to pretty good strength. Every transition in tubing that's not smoothly transitioning adds drag and back pressure sound waves. The megaphone shape was to broaden its power band help of low pressure sound waves back to valve seat. Swooshed photo does on show a sing;e tapered bend. Might find a 2 smoker expansion chamber that's got a formed expanding bend to chip out and Tig in.

https://www.google.com/search?q=2+strok ... 33&bih=415

From practical experience, the way I would do this (lacking CAD etc") is with stiff card sheet of the same thickness that you will make the final item in steel. You mark up an approximate 1st pattern, cut it out and bend it to the best approximate shape / fit. The first result indicates what the next version will be. Trim it here and there, fit and try again until you get the right shape & size. Then simply copy the final card template onto steel sheet and with a great deal more force and care, bend it to shape.
Use a soft face mallet not a hammer and put something under the work piece to cushion blows and that helps it achieve a smoother shape.

Mick

You can only get a bend in one plane using simple tooling, lay out the centre line shape you want,1/2 the circumference layed flat with the taper you want spread down the center line,copy to two sheets of steel, weld along edges, weld in fittings, connect porta power to garden hose and start pumping welding up the leaks as you go, only use water, no mess easy to weld leaks

Whacking up a few forms for ' the curves ' from old bits off 4 x 2 or fence posts gets something to ' dolly ' agaist , or VcV .
GENTLE dressing with anamer for curves , pre slit in the odd place , then trimming the mateing edge to fit .

Paitiance beats violence , We at Aston Martin have 14 years practice before makeing a bonnet . :lol: :lol: 8)

Indeed , a template from scap / cardboad aint a bad idea , A stiff paper one off the opposite pipe , with a alowance for it being outside ( minus a 1/16 in. )
should get you a close match . Tack it all up before seam welding , then go round sequentially so as not to heat / warp . Dress in ' irreqularities ' as you go
to keep it straight .

A look at ' roof chops ' on 30s to 50s rods ( How To ) would show similar techniques / methods .

A BUCKET OF WATER , and a Damp rag ( soaked then wrung dry ) is used to SHRINK , as the weld gets dull red . Brighter & it will embrittle .

A pair of vices in line can support a rod / stick / plank / form , for ' working ' the meatal on , and aligning .( see ' old bits of wood carved to suit )

i will have a go at it,will post