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DIY casting (rubber, silicone, cement, polyurethane etc casting)


Roman
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19 hours ago, Roman said:

If anyone here has more smarts about this than my zero, I've ordered some of this 
https://www.barnesnz.co.nz/polyurethane/easycast-1306


 


Since I cant do any resin infusion stuff I thought I'd just dump this into my mould for gearbox crossmember and see what happens.

20200610_215431.jpg.1a5b8d081f9667162ca7adab8ddf7e6b.jpg

 

20200610_223728.jpg.497586cc8282a71f4d9d26aae4e241cd.jpg

Okay so this was a fuck up. 
It's 65 shore D hardness not shore A 
Shore D is for rigid poly and shore A is for flexible 
So shore D 65 is around Shore A 100, AKA stupidly rigid as you'd expect! 
This would actually just hold my engine up as a crossmember, rather than the rubber for it haha.
However I'm happy with how well the layer lines have been minimized on the 3d printed mould with some filler primer. Even if some of it stuck to the part on the way out.

It was crazy seeing how this stuff sets. It's a yellowy transparent liquid, like water. Then after a few minutes it almost instantly turns solid and white.

Will try some 65A polyurethane rubber next.

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I need to repair a tail light, remake fender mirror bases and indicator lenses would be a bonus at some point. Keen to see what people make in here. 

Cheapest taillight i've found was $250 + shipping from Japan, probably worse now due to exchange rate and shipping. Yeah I think i'll learn how to mold things... Will be sure to post up any progress with products used. Would be good to see other people doing so too. Saves buying crappy products if someone has used it with bad results etc.

 

What sort of resin would you go with for fender mirror bases? I was looking to make a two piece mold, somehow, and make a few spares as I need two of each side. Might be able to sell a couple to recoup some of the manufacture costs.

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Imagine this sort of top design, with a thin angled tube on the underside. I broke my spoiler somehow, contents within.

 

30-NS274_1_420x.JPG?v=1568862576

 

I don't actually have a picture of mine as it's been put away in a box for a rainy day. Getting pretty rainy so I should probably hunt it out. Flat base for the most part though. With raised sections under the mirror. Very similar if not the same as below. Bottom tubes locate the mirror on the guard and provide the space for the threaded rod to pass from under the guard to the mirror guts itself.

 

fendermirrors.jpg

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So I finally got around to mixing up some of the 65 Shore A polyurethane to see if it seems about right for engine mounts etc. 
I tipped some into the corner of the cut off bottom of a coke bottle.
the results - aahhhh... 

104381718_569883447048589_5742695563465349818_n.jpg.fba1539fabe0b9513d7353e154956cd9.jpg


It feels weird to give a review saying these mini boobs were about the right firmness but here we are.
Definitely needs degassing, end up stirring a whole heap of bubbles into it that don't escape at all.
This stuff is very gluggy compared to resin etc.
It also took bloody ages to set. Like, more than a day.
Very different to the solid stuff I used earlier which set in about 15 mins.
I've been watching some stuff about bonding it to steel, sounds like you need to rough the surface with sandblasting, use a polyurethane friendly etch primer, then you'll get a really strong contact with the urethane poured against it.
I guess only other thing is to make sure it's somewhat petrol/oil/temperature tolerant. I guess it would be seeing how many people use poly bushes for nearly everything.
Will try find what sort of additive you can use to colour it.

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Might be able to use a different catalyst to kick it off quicker

Also make sure there is no moisture in your molds as that reacts with the urethane during curing and makes bubbles - that's how they make polyurethane foam for seats and stuff. 

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10 hours ago, Roman said:

So I finally got around to mixing up some of the 65 Shore A polyurethane to see if it seems about right for engine mounts etc. 
I tipped some into the corner of the cut off bottom of a coke bottle.
the results - aahhhh... 

104381718_569883447048589_5742695563465349818_n.jpg.fba1539fabe0b9513d7353e154956cd9.jpg


It feels weird to give a review saying these mini boobs were about the right firmness but here we are.
Definitely needs degassing, end up stirring a whole heap of bubbles into it that don't escape at all.
This stuff is very gluggy compared to resin etc.
It also took bloody ages to set. Like, more than a day.
Very different to the solid stuff I used earlier which set in about 15 mins.
I've been watching some stuff about bonding it to steel, sounds like you need to rough the surface with sandblasting, use a polyurethane friendly etch primer, then you'll get a really strong contact with the urethane poured against it.
I guess only other thing is to make sure it's somewhat petrol/oil/temperature tolerant. I guess it would be seeing how many people use poly bushes for nearly everything.
Will try find what sort of additive you can use to colour it.

Not sure if relevant but I watch a guy on YouTube that makes softbaits, he puts his mixture in a vacuum after mixing to get the stirred in air bubbles out. 

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