20 replies to this topic

[Ritual33]

Just a note, I've just bought everything I need to make the resin cast described on dan williams' site. Just need the pvc now. Will post pics when I'm done, plus make a how to.

Regards,
Drew

[Anders Greenman]

Drew: I bought my resin in 1kg buckets about 7£ each at a hardware store.
How much force needed to be applied depends on the diameter of your sylinder.
A small sylinder would require less force to get the same density as commercial grains.
To measure the density is simple mathematics. Check out the wheight of something like 10cm^3
of meal uncompressed, and find out how long the piston will have to go before it reaches the desired density.
Let's say 10cm^3 of meal weighs 10g, and you wants a density of 0,5g cm^3. Then you'l have to press the piston down until volume is 5cm^3. Just put some marks at your piston just to let you know where to stop.
And polyester mixed with good sand (fine blasting sand) will make a piston rock hard!

[Ritual33]

Thanks for that Anders, much appreciated. I'll keep you updated on my progress.

Drew

[BigG]

Excellent, I have a halfords just down the road, I'll go take a look sometime (press hasnt arrived yet, no rush). Question: How in the world do you measure the density of the powder? Do you use somekind of physical method or is it simply mathematics?

BigG: When you mean "start" at 10 tonne, do you mean that some would even go beyond this amount of pressure? Do I need to get a bigger press eventually? (sealey 10 tonne).

Frozentech: How well machined are these rods? Would you recommend them over the resin cylinders I could make?

Regards,
Drew

Well, it does depend on the amount of material you are going to press. Small quantities will require less pressure to reach certain density. If you live in the UK, you should check the legal requirement to such manufacture. For experimental purposes you will be allowed very small quantities anyway. As I said before, the key is repeated performance, so once you experimented and made efficient BP to your application, stick with the procedure and the materials.

Phildunford: I like the 1.7/cc note. I’ve seen this in a lot of places – but non-said that this is what is reached in industry or that BP does not burn faster under greater pressure. If you know of such a source please let me know, as I am looking for that information myself.

To note, there are a few experiment on BP packs where they have been compressed under a 9ton per square inch compare to 3ton per square inch – and the rate of burn improved by about 18%. The article does not mention what density they were compressed too.

I myself have been audience where BP compressed into the same density using higher tonnage rammer resulted in the burn rate being different. The assumption was that the greater rammers were more efficient in driving out the moisture – so although density was similar – one pack contained more water then the other.

[fishy1]

http://www.gaelforce...roduct_id=20277

This the kind of resin that would be alright mixed with sand?

[Mortartube]

http://www.gaelforce...roduct_id=20277

This the kind of resin that would be alright mixed with sand?

That would be okay, but it is epoxy resin and not polyester resin, it is therefore twice as expensive and you must cast it outside as large lumps create a lot of heat when curing and they can catch fire if they are in a big enough lump.

Also cast epoxy on a clear bright day as dampness can affect the machanical strength of it as it cures according to the instructions on the pack I use in boatbuilding.