whats a shrinker?, on american chopper and the likes, thay all use an english wheel to do the big curves and for the small tight ones they use the power hammer, or a nylon mallet and a bag of sand (i think)
the shrinkers i have used are only for the edge of the metal if that makes sense like for making wheel archs ,im guessingyou want to give a large flat piece? english wheel? or mallet and leather bag and dolly it out to get dents out ???
Petrol tanks are generally made in two halves and beaten roughly to shape with bossing mallets and a sandbag, then a wheeling machine is used to sooth out the 'walnuts'. i assume you are looking at aluminium. That will need to be annealed. You may need a shrinking machine right at the end to make the two halves fit before welding. This is a very skilled area of sheet metal work. Hope this helps.
Perhaps i'd be better off with a sandbag and and making an english wheel, im sure i saved some plan's off the net somewhere. I'm looking at the moment to make the top of the tank in two half's then the sides in another two to three pieces, so the panel's will almost be flat apart from the edges.
One option might be to chop up a stock tank or two, I considered that when I did mine, but did it differently in the end. Looks like wheeling is quite a skill as well as hammerforming. Would love a wheel though...
Theres some great vids on utube of shrinking. A small press tool puts tucks into the edges to take up excess metal, then they lock the end of the tuck by creasing its periphery with hammer before flattening it.It looks easy but im sure its not. The press tool is easily made. Ive orderd my hammer.
The little mechanical shrinkers while very useful only have a throat depth of an inch or so. As throat depth goes up size/weight and cost increase exponentionally! An old tree stump is incredibly useful, with a shallow bowl cut into it you can shrink further into a panel (tuck shrinking) than with a small mechanical shrinker and with less marring- yes, unfortunatly it is harder than it looks. Can be used for stretching too although a shotbag is nicer to use. An English wheel doesn't really do anything that can't be done with mallets, hammers, dollies and stakes, it just lets the user produce panels (or a mess) much more quickly- one exception would be planishing where the wheel is both quicker and easier than with hammers/slappers and dollies. Quiter too. Stilll need to planish welds by hand though for reasons of access or size...
While a wheeling machine made light work of making the actual scoops it's of no use for planishing the welds
Basically im after near flat panels with a bend on the edges no deeper than 10mm. Looking to make a tank that looks something like a ktm rc8 tank or a bimota db7. Sorry not sure on how to upload images.
Basically im after near flat panels with a bend on the edges no deeper than 10mm. Looking to make a tank that looks something like a ktm rc8 tank or a bimota db7. Sorry not sure on how to upload images.
There's very minimal shrinking involved in that. Most of the skill is in laying out the patterns. Basically if you're trying to make a shape that could be made with corners from single plane bend pieces of steel, you can make it sith rounded edges. snag is that as you round the edges over, you need to start with a smaller template. How much smaller depends on the angle the planes meet at and the radius of the edges.
One way is to make the pieces over sized and then cut through the overlap with an airsaw or a jigsaw. What you lose in the cut is made up for by the pieces being out of line.
Making things to a certain shape is relatively easy, making them an exact size on the other hand...
Which is where you need to think the job through before you start.
Try getting hold of some stiff card (art shops?) and making an angular vbersion holding it together with duct tape or something. If you can do that, you ought to be able to make on in metal.
Ahh, if you're planning something similar to the simple, elegant example Blackjack posted then a hammerform would make it easy to knock up. Quite a bit more work than hand shaping the pieces but once the hammerforms made then it's almost a no-brainer. I normally only bother with a hammerform if i've got several identical or mirror image pieces to make- the extra time in making the hammerform is negated by the fact it's quicker and easier to produce the parts...
This is/will be stainless trim pieces hammerformed over a piece of 6mm plate. MDF works well for a few aluminium parts, hardwood lasts longer if more panels are needed and a router is perfect for putting the radii on the edges. With gentle changes in shape i imagine wood will work for a couple of 18/20swg steel panels
I put the radius on the edge with a ball pein hammer on a flat surface.
By radiusing both panels, the weld is in the shaped bit of the metal and there's practically no distortion, which can be a problem if you're welding big flat panels.