42 replies to this topic

[brightonben]

Don't bother using grass seed it is far too expensive and far too small and in turn will pack too tight in your shell, hence needing too much. I've always used BP coated vermiculite (medium grade) works for me, have a go.

[jellywerker]

expensive? it's really cheap...

Another option that might be more availiable in western countries would be wheat chaff/hulls similar but more local.

Edit: Try a mill or something and ask if you can bag some.

Edited by jellywerker, 11 December 2005 - 05:35 PM.

[EnigmaticBiker]

You could build a press by using flowing water. Connect a 2-way tap to a source of blasting water, and make one smaller and attach a tube to it securely with PVC tape and resin. Put what you want to press inbetween two sheets of wood or metal inside a big plastic bag without any holes. Connect the bag to the tube and make sure its air tight. In theory you can get 10 tonnes by drawing air from the bag due to the action of water carrying it away, no expensive devices required.

Interesting, sounds like a venturi-effect vacuum pump.

Have you tried it, I imagine the bag would have to be pretty robust.

Do you have a figure for the size ratio between the two pipes coming off the tap?

[fishy1]

The same principle applies to quick match. Ordinary black match burns at a rather slow rate but if you take 3-4 strands of the stuff and wrap it up with a paper casing it burns very quickly indeed. Again suface area. Directional to boot. Shimizu explains many of these principles in Art,Science and Technique.

[Edited on 27-5-2003 by bernie briden]

does wrapping black match in paper increase the surface area?
i wasn't aware of that.

doesn't black match burn faster when made into quickmatch because the hot gases are forced down the paper tube, and not because of the surface area?

[completebeginner]

Im pretty excited I built a frame for my press today and tomorow im gonna bolt it together and the 2 ton jack cost $7!

[fishy1]

Im pretty excited I built a frame for my press today and tomorow im gonna bolt it together and the 2 ton jack cost $7!

you got a blast shield with it?

just something to think about.

[completebeginner]

oh ya almost forgot where might one go about getting one of those?

[RegimentalPyro]

I would recommend half inch plexiglass. I'm afraid I don't know where to recommend in BritishColumbia but you might start with your local plastics supplier in the business pages.

I got mine when our local bus shelter was demolished by a careless driver. They were throwing away the old plexiglass and I rescued it from the skip....

[sizzle]

Tut, tut, Regi, that's still owned by the bus shelter company.. (joking )

There are a few plexiglass suppliers online actually if you search around, also B&Q stock it if I remember rightly, I'm not sure if they do 1/2" but it's worth looking to see.

[Pretty green flames]

Tut, tut, Regi, that's still owned by the bus shelter company.. (joking )

There are a few plexiglass suppliers online actually if you search around, also B&Q stock it if I remember rightly, I'm not sure if they do 1/2" but it's worth looking to see.

You can always glue thinner plates together.

[Frozentech]

I would recommend half inch plexiglass. I'm afraid I don't know where to recommend in BritishColumbia but you might start with your local plastics supplier in the business pages.

I got mine when our local bus shelter was demolished by a careless driver. They were throwing away the old plexiglass and I rescued it from the skip....

I would recommend Lexan over plexiglass, as plexiglass shares with PVC the possibility of becoming sharp fragments of shrapnel. Lexan is unfortunately much more expensive, but is to acrylic/plexiglass as HDPE is to PVC. I found a 48 x 48 inch piece for sale on eBay, and just use 2 sections of 1/4" Lexan as the shield on my press.

Here is a link to an interesting experiment done to compare effectiveness of Lexan and plexiglass blast shields :
Blast Shield Experiment

[completebeginner]

I just pressed my first bp cake! one inch it was pressed with a dowel under 2 tonnes inside a pvc pipe!

[littlejohny]

inside a pvc pipe!

I don't understand that part, how are you going to get the cake out of the PVC to crush it.

[completebeginner]

easy take the pipe tape on end up put it on the wood base press with a dowel take the pipe out take off the tape and push it out with the dowel

[damocov]

I've just pressed my first BP cakes in a similar way, I havent got a huge press though I've used a 10 inch "G-Clamp" in a bench vice with a long steel tube for a lever.

It doesn't get up to the same sort of pressures as a hydraulic jack, but seems to compress the BP quite well into a homogenous block that can be pushed out of the tube once the pressure has been released.

I used a piece of 15mm marine ply as a blast shield which had the disadvantage of not allowing me to see the pressing as I pressed.

Having read the article above about blast shields I have a coupel of questions:


Anyone know an easy source of lexan in the uk?

Anyone actually had or heard of a BP cake ignitting becasue of the pressure?

Edit:

here's a link to a pic of my first pressings http://www.damian-fe...yro/bpcakes.jpg

Edited by damocov, 07 February 2006 - 11:57 PM.