[Stoves] {briquetting} Fwd: new briquette press from Hungary

[Richard Stanley]

Good insights as ever, Crispin, 

Myown experience is that us eof simple hydraulic bottle jacks at least the 1 - 2 ton types supplied with cars or sold separately for same, are also fraught with problems because they are not designed for continuous duty. After all, how often really does one use a car bottle jack and is it often used in a gritty dirty environment--rarely. 

I have seen lever bottle jack  combination units that take advantage of over center end pressures that can easily get to the cinva ram outputs but frankly I would steer away form the smaller bottle jacks for the reasons mentioned. At the larger production scale that Nora, Attila an Kevin Adair are undertaking, the 20 - 25 ton industrial strength designs stand up a lot better.
As to pressure, rarely are you going to need more than 12 to 15 kg/cm^2 (bars) if they get the mix correct for the typical ag residue blend used in the wet  briquette-making process. PAper based blends commonly only require well less than half this amount) 
If the operator miss understands the essentials of testing the blend of for taking  set and holding together with the inherent adhesion of its own intermingled -softened-natural fibers,  then ( at least without added binders) they will have to go on up to 6000 psi or more to start melting lignin– if there is any,  and hope to heck it stays cool enough to avoid turning it into a steam cannon. 

The compression curve – as non linear, is agreed ideal for over the center linkages. 
Some youth in Haiti at least as of 2005, set up steering wheels with a connecting rod /crank shaft-like  linkage to actuate the hydraulic jack, spinning the wheel wildly, until it loads up. Its not same as a weighted flywheel screw design but it tends toward same effect bait. Another way to accelerate a industrial hydraulic jack press is to set up a mechanical foot-operated eject lever using a simple fulcrum, to lift the whole platen up the final few inches to eject the briquettes in the case of compress-up designs like this) as the eject phase requires far less pressure (1 - 3 kg/cm^2). 

Sanu KAji has been using screw presses for quite some time up in Nepal as has the almost internet invisible Bonaventure Chidzaru of the PAMET organisation and Willi Malabu of Nkhomano Centre for Development in Blantyre and Indirande Malawi, respectively, but how they manage to keep the screw thread clean, and how long it is lasting, working with briquettes is not known. That is the thing about this kind of process its a gritty/dirty and wet working environment.  Sanu what are your thoughts on maintenance of a screw thread of your presses ? 
The compound lever  mini Bryant wood press that is most popular with our colleagues, is no angel in this situation either:  One  hasto wash it and coat the wood with some form of preservative at least 4 x a month to avoid termites / wood rot etc. 

Hasta 
Richard Stanley
Antigua Guatmala

On Jan 13, 2013, at 11:43 AM, Crispin Pemberton-Pigott wrote:

Dear Nora
 
In English that screw press with weights is called a ‘fly press’. They are very useful in that you can use them for pressing oil during the summer and with a change of tooling, make briquettes when available.
 
It is possible to use a spreadsheet to optimise the production by changing the thread pitch and handle length. This was done with a screw press used for marula oil pressing used at Swazi Secrets which makes (of course) marula oil. Seehttp://www.newdawnengineering.com/website/oilpress/marulapress/
 
The force generated is much greater than the ‘apparent’ pressure from the thread and the arm length because the weights have momentum. This allows for more rapid throwing of the handle downwards before starting to do the ‘real work’. Using the two-arm approach a single person can do most of the work and a second person join them for a minute or so when the last crunch is needed. These presses have a working life time of decades, not months and of course have no hydraulics. The pressure (over the whole long range, can be 1-2 tons.
 
If someone wants to calculate such press parts contact me directly for assistance.
 
When the distance travelled is known clearly, it is more efficient to use an over-centre clamp like a CINVA Ram or Terrabric mechanism which can run to 7 or 14 tons respectively. Again, no hydraulics and makeable in an ordinary machine shop.
 
Regards
Crispin
 
+++++++
Hi!
(little correction: i am a Hungarian born Hungarian citizen, and now living in Hungary again :).. i was just studying in Holland)
 
When seeing the design from Haiti we were a bit afraid of using springs for ejection, so we really wanted to push from the bottom.. And that was a challenge with the spikes that make the holes.. And then my colleague had the great idea with the two-way lid. (He is called Attila, I include him in the list) And I dont think it should make much difference that the holes are rectangular. 
 
The other great idea of his, which i am not sure if u can clearly see from the pictures, is that one of the lids is actually a tray that should slide under the briquettes after compressed (and pressed above the mould), and when you lower the jack, the briquettes just stay on the tray and can be moved (we will probably make another one of these, to save time like with the two mould sets with the legacy press). When we were testing the press, we had a little accident with the jack, so I am not 100% sure yet whether the tray will leave the briquettes intact(ish) but the first try when the jack was working was promising. 
 
The fabricators are of a small coop from another very poor region of the country. (They are actually also Roma/Gypsy). A friend NGO set us up with them, and they were really great to work with.
 
Sure we would be very happy to make a manual out of this, but I first want to wait until we can properly test it and hopefully make a second prototype soon. The material costs were quite high which would be quite good to reduce. 
 
I attach a collection of images and some info on presses that can be used as inspiration. (I think it would be really interesting to experiment with the screw press with the weights).
 
Thanks for your support!
All the best,
Nora 

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