Since I first saw(and fell in love with)Patandjali's excellent rdt crossbow,and decided to build one,I realised that the difficult parts to build would be the cams,so I'd tackle them first.After much trouble and not a little expense,I managed to locate and buy 3/8ths ins. aluminium plate.Since deciding to build the cams,I have given much thought to how to do it.I considered going with laminated cams,and reluctantly put aside the idea,because I was already into the cams for 60 bucks worth of aluminium plate.The more I think about the idea,the more I like it.
Cutting out the cams with a jigsaw just didn't work for me,it wasn't accurate enough,was hard on the jigsaw,and to ensure I didn't go to the wrong side of the line I had to leave to much material behind.This meant a hell of a lot of filing.Anyone who has done much filing knows that to file accurately over large surfaces is finicky and requires much time and patience to maintain accuracy and squareness.These aluminium plate cams are thick enough to qualify.
If I make these cams again,I will laminate them using 1/8th aluminium flat stock.Epoxy glue is good for joining aluminium,and if there are any worries about delamination(around the outside edge of the big cam for example)rivets can be used,brass rivets would contrast nicely with the aluminium.Laminating also means that material that is more readily available as scrap,or to buy can be used.
Gnome raised a good point about the strength of the laminated cams,I think that a 1/8th inch centre lamination will be more than strong enough on a 3/8th ins. thick cam.I also think that making laminated cams will take no longer than solid plate cams,possibly less time, and use less material.
Hermit.
Cutting out the cams with a jigsaw just didn't work for me,it wasn't accurate enough,was hard on the jigsaw,and to ensure I didn't go to the wrong side of the line I had to leave to much material behind.This meant a hell of a lot of filing.Anyone who has done much filing knows that to file accurately over large surfaces is finicky and requires much time and patience to maintain accuracy and squareness.These aluminium plate cams are thick enough to qualify.
If I make these cams again,I will laminate them using 1/8th aluminium flat stock.Epoxy glue is good for joining aluminium,and if there are any worries about delamination(around the outside edge of the big cam for example)rivets can be used,brass rivets would contrast nicely with the aluminium.Laminating also means that material that is more readily available as scrap,or to buy can be used.
Gnome raised a good point about the strength of the laminated cams,I think that a 1/8th inch centre lamination will be more than strong enough on a 3/8th ins. thick cam.I also think that making laminated cams will take no longer than solid plate cams,possibly less time, and use less material.
Hermit.