 |
||||
|
|
||||
|
||||
 |
||||
|
||||
 |
||||
|
||||
|
||||
|
||||
 |
||||
|
|
||||
 |
||||
|
|
Using the Bending Rolls
The rolls are used held in the bench vice. The top roller moves down under gravity but is restricted in its upward travel by the adjusters. The motive power is provided by simply pushing the material through. To use the rolls it is important that you set the top roller parallel with the bottom rollers each time you make a tyre etc. If you don’t you will not get a perfect ring. It will be a spiral. With the top roller resting on top of the bottom rollers screw the adjusters down until they touch the top roller spindle. Then with a felt pen mark the wooden handles with a radius line each in the same direction e.g. at the 12 o’clock position. You can then unwind the adjusters and provided you turn each one the same number of turns with reference to the felt pen lines the top roller will be kept parallel to the bottom ones. Start by setting the rollers using the adjusters so that there is a gap between the top and bottom rollers such that when the top roller is lifted by hand upwards to butt against the adjusters you can just see daylight between them. Push the material through then reset the rollers tighter by screwing the adjusters down a little making sure that you turn the same amount on each adjuster using the felt pen line for reference. Each time you adjust the rollers by screwing the adjusters downwards the material will bend further until you have a complete ring. The problem now is to get the tyre off without spoiling the shape. To do this un-screw one of the angle iron bracket screws on each side and rotate the angle iron and adjuster out of the way. This will enable you to remove the top roller and extract your tyre. Because you have to remove the screws each time you make a new tyre it is better to use crosshead screws as the heads wear less than slot heads. In fact it might be better to alter the design so that bolts and wing nuts are used. It can be a little tough on the hands but I find a pair of gardening
gloves a help. As expected thin material is easier to form than
thicker stuff is. However, I have bent bright mild steel 1/2 in
wide x 1/16 in thick but it made me sweat a bit!! You will find that you get a flat section at each end of your tyre. There are two ways to get rid of this. You can cut them off provided you use a length of metal oversized or you can hammer them into shape over a round bar. I know this all sound very confusing but it is easier to do than to describe and I am sure the photos will help. I am sure the ingenious among you could adapt this idea to incorporate gears and a winding handle to make it easier. Off the shelf gears are available from Muffet Engineering, Tunbridge Wells at a reasonable price. They have a Web site. There are sets of plans available in model engineering books to make more professional looking miniature bending rolls but for those who do not have access to a metal working lathe and milling facilities I hope the above method will help. top |
