Hollow crank bodies
4 replies to this topic
Posted 27 November 2008 - 10:37 PM
I did a search on this and didn't find anything. If you already covered this, sorry.
Has anybody ever tried rotating a silicon mold that is half-or-so filled with an epoxy resin to get a hollow body?
I guess its the inverted version of putting finish on rod wraps.
I suppose you wold have to make a gadget that would rotate it in several directions.
Posted 28 November 2008 - 12:00 AM
Here is a post in which I proposed the idea. Post No4 http://www.tackleund...tic-resins.html
Like I say in the post, it really needs to be a machine to rotate the mold. I suggested a speed of 60rpm might give a result, however I suspect that this is still too slow, just a gut feeling. Experimentation will have to be done.
It is on my list of projects, but a long time off, so much to do!!!
I think the idea has merit and I hope you take it on and report back. PM me if you want any assistance.
Posted 28 November 2008 - 06:46 AM
For symmetrical weight distribution a hollow lure body has to have consistent body thickness. Controlling rotocast to achieve that is not worth the trouble IMHO.
If you know how to make a mold, it's well worth it to just go for a multipart mold to get the hollow body with locking pins, transfer chambers and all the works as a further possibility. ArtBrush posted a multipart mold tutorial some years ago, not sure if it's still around. Try searching for it.
Posted 28 November 2008 - 09:56 AM
I have a 2 part clear epoxy that cures in 24 hrs. Isn't slower better? I would think it would settle more even.
Posted 28 November 2008 - 10:14 AM
Yes, slow is better. When I experimented, it was with polyester resin. Once that starts to go off, it goes to a firm jelly in a few seconds, so the material clumped, but I was turning by hand.
True, the wall thickness will not be even, but it should be symmetrical. However a 2pc casting of each half would allow you to control the material distribution, for positioning ballast and screw eyes.
The problem is that no one has tried the rotation method, so no one can really answer your question with any confidence.
The speed will be the critical factor. Too fast and the resin gets thrown out to the deepest parts, leaving the sides too thin walled. Too slow and the resin will just clump around. You will need a variable speed setup and do lots of tests, making notes as you go.