pourable Rubber for simple working die

[archibaldtuttle]

Engineering, other than in the simple emperical sense, might be slightly overstating the work on this project but couldn't find another forum discussing rubber properties.

I am simply trying to fill a short piece of aluminum gutter with a moderately soft rubber that would cure into maybe a one foot long block that I could remove and then insert into other pieces of gutter to retain their shape while cutting on a miter saw.

There are returns at the very edges of the gutter that I would tape off. I don't need the tinest details, just the basic shape for the larger profile.

Obviously cost is of some concern given that this will not be painted on in thin layers as with some rubber for creating molds but would be perhaps 240 cu in. or more. and it would need to cure to the center of a pour that was about 5 inches across in both height and depth and some 12" long. I don't really care if it is a one or two part approach.

Find gallons of Holdens HX 200 "Casting Latex" on ebay for $60 that say when used with #64 Filler it will set in a plaster mold with various hardness. I presume that is an indication that some thickness can be acheived and it doesn't need exposure to air to cure or at least that the cure would ultimately reach into the material.

I'm not precisely sure where I want to be on a shore scale. I could just about use a block of wood if it could easily be sculpted to the shape. Could probably also make due with "great stuff foam even, but I like the idea of something between wood and great stuff in terms of resilience, density, etc.and have been wanting to gain more facility with rubber as I would like to manufacture some thinner shaped elastomeric boots as preformed flashings for EPDM roof systems, so figured it was time to enter the world of Rubber engineering.

I hope I'm not wearing out my welcome with too mundane a question but most of what is on the net about how to use or select rubber assumes it is for mold making and not creating a thick part of the sort I'm thinking of.

Thanks for any knowledge you can impart or pointers to websellers or wholesalers who might be able to further guide my selection.

Brian

 

[cloa]

What is shape desired? What is the operating environment of the rubber?

 

[archibaldtuttle]

This is a piece of standard aluminum gutter so the cross section is a "U" with 2 flat sides at a right angle and the front is an ogee running upwards from the bottom of the "U" at about 65 degrees. During casting I'd run some tape around the gutter to keep the U from spreading open. As I mentioned, the U is a bit more than 4" deep and about 3" across the bottom and 5" across the open top. The aluminum is .032".

As far as environment goes, the purpose of this cast is to give something solid to allow the gutter to be clamped to a miter saw for cutting. So it will not be subject to constant UV or temperatures stresses although it will be used outdoors briefly while cutting it would otherwise sit on the shelf in the workshop waiting for the next job.

thanks

brian

 

[btrueblood]

My first thought was wax.

2nd thought, if you really want a pourable rubber, would be a urethane casting resin, somewhere in the 80 shore A durometer range or higher.

3rd thought, is a softer urethane (or even an epdm coating) poured over a roughly shaped filler block of wood, or several blocks and several pours.

The pourable epdm coatings don't like to be cast in thick sections, as they rely on evaporation of solvents to "cure".