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Tobacco Press

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Tobacco Press

Postby Nomad » Tue Aug 08, 2017 10:40 am

I've been busy in the workshop, making a small tobacco press. The plan was to make something that would compress about 50g of baccy into a block the size of a typical plug.

Here are the parts...

Image

At the top-left is the base, and next to that is the box or sleeve that keeps the baccy in place, and then there's the top (shown upside down here), which incorporates the ram that does the actual compressing. The coach bolts are M8, 150mm long. The little rectangle of plywood in the middle of the base is mainly to help keep things aligned during compression - it stops the bottom of the sleeve from moving around.

It's mostly 18mm birch ply. The two smaller pieces in the sleeve, and the ram, are beech. The parts in the sleeve are a better way to fit screws - If they were ply, there would be a risk of it splitting or delaminating. It's all finished with food grade walnut oil to hopefully make it easier to keep clean should any gloop be forced out of the tobacco.

The XY size inside the sleeve is 45.5 x 31mm.

Here's a view with the base and top turned over...

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The base has an additional bit of plywood on the underside to ensure that the domed caps on the bolts don't press onto the bench - I intend to clamp it down while packing and compressing, and don't want to mar the bench top. The two screws that fix the ram onto the top are countersunk to provide a flat surface for more clamps to be used for the initial phase of compression.

Assembly is easy. The bolts are fitted from underneath...

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...the sleeve is placed onto the base...

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...and the top is fitted and bolted down...

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The fit of the sleeve around the little plywood platform and the ram has about 1mm or so clearance. This is to ensure that it all slides together easily without dragging or being awkward. It also allows some space to line everything with baking paper to isolate the tobacco from the wood.

The heights are such that, when the ram is at the top of the sleeve and about to start compressing, the ends of the bolts are already engaged with the holes in the top by about 6mm, meaning the top is already quite well aligned and that the ram should go straight into the sleeve, hopefully without catching the edges. The idea is to use a couple of clamps to pull the top down until the ends of the bolts are clear, at which point the washers and nuts can be fitted. Longer bolts would have negated the need to initially clamp like this, but those are what I had lying around. On the other hand, the initial clamping may well be enough to bring the top down quite a bit and will be much faster than turning the nuts. At a certain point, I expect the nuts to be the easier way to get the final compression done. Once it's fully compressed, the clamps can be taken away, and the press becomes a small object that can be put aside, and possibly placed into, say, a warm environment (and I get my bench space and clamps back).

Many home made presses (notably, the C-clamp type) seem to work on the basis that you just compress until it feels right, I wanted to have a known height for the plug, so the idea with this one is to compress until the top reaches the sleeve...

Image

In this position, the gap between the little plywood platform and the ram is 20mm. This means that the tobacco can be compressed to a known ratio - I start by measuring the volume of the loose tobacco, crunch some numbers to work how tall that would be in the XY size of the chamber in the press, and then divide that by the compressed height to get the ratio.

For example, if 50g of baccy is 250ml, that volume would be 177mm high if shaped into a column with the same XY size as the chamber. When compressed to 20mm high, the compression ratio would be 8.7 to 1. This can be adjusted by adding another bit of ply on top of the platform - I have 3.5mm and 5.5mm ply, and these would give ratios of 10.5 and 12. The extra bit doesn't need to be fixed - it just need to be a slightly loose fit because the sleeve will stop it from moving around.

It should be noted that the compression ratios are approximate because it's hard to determine the volume of loose tobacco. If the baccy is just tipped into a measuring jug, it will be relatively bulky and it would take very little pressure to push it down a bit. In this loose state, the volume could change quite dramatically. So, in practical terms, it's more about working out empirically what the preferred platform height is for a particular blend. In the first instance, I'll start with the 20mm plug height and see what I think.

I'll be trying it out with Gravedigger since that's my only finalised home blend so far. I'm also reasonably familiar with it, so it will be very interesting to see what effect the press has. More anon...
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Re: Tobacco Press

Postby KevLa » Tue Aug 08, 2017 12:30 pm

Nice work, Nomad! Can't wait to find out how it goes :)
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Re: Tobacco Press

Postby Nomad » Tue Aug 08, 2017 11:36 pm

Well, mixed results so far, but no disasters and the first pressing is still underway. Here's how it went...

The stuff set up after mixing the tobacco...

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The bowl to the left is what I got for mixing larger quantities after I found that the square sandwich box I had been using for the blending samples wasn't big enough for 50g. The stick was used to very lightly tamp the tobacco in the measuring jug to find out the volume. The press is clamped to the bench to stop it moving around while I fill.

Note the baking paper. It's done in two strips - one with the width matching the long side of the chamber, and one matching the short side. The strips are pushed down using a bit of wood that reaches all the way down, then folded over the sides of the box and some tape applied to keep it in place. No tape on the other bit on the ram.

The chamber filled with 50g of Gravedigger...

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This was pressed down with the fingers using moderate pressure. It was quite easy - I wasn't trying hard or anything. The fill method was like a big version of the three pinch method of packing a pipe, just with bigger pinches and rather more than three.

I then put the top on...

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I just held the baking paper in place with a couple of fingers. Tape would have affected the size of the ram, and this works fine because it stays in place as soon as the ram presses onto the tobacco. At this point, I started adding a couple more clamps to bring te top down far enough to expose the ends of the bolts, but I realised that it was all still quite springy, so I pressed down by hand and managed to get it this far...

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('Scuse the poor focus.) So, the nuts and washers were fitted and I started tightening. The nuts were tightened in diagonal pairs, two turns at a time, to keep the ram level as it moved down). The tightening was surprisingly easy. I used a small socket and ratchet that has a hole in the middle to allow long bolts to pass through, which has a handle about 6" long, so somewhere between a 1/4" and 3/8" drive ratchet.

At this point, I didn't pay attention to the cracking sounds and kept going - until I noticed that the bits of beech in the sleeve were sticking out about 2mm at the bottom.

On went a G clamp to rescue things...

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...at which point, I saw that the two bits of ply were also splayed a bit at the bottom, so on went another two clamps...

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The top still had 2-3mm to go, so I went out for the afternoon to let it settle for a while and did the final tighten when I got back.

Things I've learned so far...

The tobacco is easy to pack into the chamber. The volume I got was 224ml, which translates to a column height of 159mm. The height of the column after packing by hand is probably not far off 69mm, so a reduction of 90mm, or compressed down to 43% of the height of an uncompressed column. And that was an easy pack - If I had a bit of stick of suitable size, long enough to get a grip of with both hands, it could have been packed down quite a bit more. In other words, it would be possible to start with a bigger volume of tobacco in this size of chamber. (At a guess, maybe 70g at the most.) Once down to the 20mm plug height, the compression ratio is 8 to 1.

The resistance of the tobacco to compression does not increase linearly with the amount of compression. As it's compressed, it becomes increasingly harder to compress it more. In this case, the sleeve gave out - the tobacco was resisting the compression and spreading out as more was applied, to the extent that it sounds like the beech blocks at the ends of the sleeve have cracked at the screws, and it can be seen that the ply has moved outwards, indicating that the screw threads were pulled out of the beech a little. I'll need to rework the sleeve after this first pressing is done, or maybe just make a new one.

The forces as the tobacco is compressed become very high. It's not clear in the photos, but the ply top and bottom plates are noticeably bent as well. I would say the cracking noises that I heard probably started with about 10mm to go, which would equate to a compression ratio of about 5.3 to 1.

The four M8 bolts were easily up to the task of applying the force, and the ratchet handle remained easy to turn all the way down.

The measuring jug wasn't very accurate. When I filled it with baccy and gave it a light tamp, it showed 200ml. when I checked this with a laboratory measuring cylinder by pouring in 200ml of water, it was low. On filling to jug to 200 on the scale and emptying that into the cylinder, I got 224, which is a surprisingly large error.


The next step is to trawl the internet to find out how long to leave it in for. Rather, to find out how soon I can take it out and see what happened. If I don't find out any more than I already have, the plan is to leave it for three days.
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Re: Tobacco Press

Postby KevLa » Wed Aug 09, 2017 5:56 am

The wise man knows he must make mistakes, and learns from them :) I must admit that I know little about tobacco presses. I've watched a few videos on YouTube, and I'm sure at least one of the presses was metal..?
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Re: Tobacco Press

Postby Nomad » Wed Aug 09, 2017 9:17 am

Yes, I've seen some made with square or rectangular box section stainless steel, but still the C-clamp type. Provided it has adequate wall thickness The steel will be much more resilient to the plug pushing the sides out as the compression increases.

When I get the plug out and have a look at the bits of wood, I'll have a better idea of what damage was incurred. With a bit of luck, I'll be able to change from wood screws to bolts passing through the whole lot. The bolts would need to be placed near the bottom, since that's where the force is concentrated - something I didn't consider when I placed the screw holes. The plywood parts seem to have survived okay, but I might need to remake the beech parts.

From what I've been reading so far, it seems that the main work with the press is done quite quickly, which is simply to get the tobacco compressed. After that, there is the option to store it for longer in a setup that maintains some pressure on it, but not the massive compression of the press. In other words, once compressed, it tends to hold its shape - it doesn't try to spring back up to the original height, but might tend to expand a little once out of the press.
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Re: Tobacco Press

Postby Geo3rge » Wed Aug 09, 2017 12:37 pm

An impressive project, Nomad and beautifully written and illustrated. This ought to be shown on other sites, if you feel able to do so.
Your craftsmanship is superb. All the wood is so well finished.
Very interested in this new development and please keep us informed of your progress.
Wonder if you could fashion, instead of using clamps, metal bands, as a kind of collar, around the main box? Just thinking of this when I read of the bending and warping.
I hope that the suspected damage is minimal.

Fantastic post. A great read and I know a couple of pipe smokers who would be very interested indeed, one of whom has a similar design but not as sophisticated as your own.
Thank you.
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Re: Tobacco Press

Postby Nomad » Wed Aug 09, 2017 3:58 pm

I'm not really interested in posting on other sites. If it helps draw people to this one, then that's fine.

The band idea is a consideration, but is really a solution to a design aspect that wasn't up to the job in the first place. The better way to approach it is to make the original design robust enough. As you'll see presently, it would also get in the way somewhat.

I opened the press earlier today, 21 hours after the pressing was done. The bolts slackened off easily enough, but the parts of the press didn't separate right away. A couple of light taps with a hammer loosened off the base, and the rest lifted away...

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Not a lot of gloop, it would seem. This was with the tobacco's moisture as it came from the jar. I've read some posts where people have warmed the baccy for a while to dry it a bit, but it looks like the Scotch Cake and Revor didn't need that. The dark stuff on the end of the sleeve is actually squeezed tobacco rather than a very dark stain on the wood (the latter is better represented by what can be seen on the base).

At this point, I tried pulling the ram out, but it wasn't moving. Rather than try and lever it up with a screwdriver or something, I unscrewed one side of the sleeve...

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The bottom of the sleeve is uppermost here, and the dark mass hanging down is more squeezed tobacco. The ram came away from the sleeve easily once the side was removed. Here it is with the paper raised up a bit...

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The whole pressing procedure seems to have worked - the paper surface that the ram pressed on can be seen under the raised flap of paper. With the side removed from the sleeve, the block was also easy to remove, and the paper peeled away cleanly...

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Here's a close-up of the resulting block...

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Apart from being a solid lump rather than squashy tobacco, the most notable thing is that it's much darker than the blend before compression (compare with the photo in an earlier post, when it was being packed into the chamber - far more light coloured bits from the Va). The whole lot has become almost as dark as the Revor. (At least, it has on the outside - I haven't cut it open yet.)

I trimmed off the edges, collected the bits that were stuck to the paper, and rubbed them out...

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It rubbed out fairly easily, although there were some small bits that were quite hard and didn't rub so readily. I weighed the trimmings and got 2.9g, and found that this fitted into the straight Apple that I've been using for blend testing. This is a pipe that normally takes closer to 2g, so the trimmings at least were much more dense even after rubbing.

Having smoked that bowl, I would say that my experience is consistent with comments that I've read around the net. It seemed to be a bit mellower than the fresh blend before pressing, and the flavour was more consistent through the bowl. Smokiness was quite good - nice plumes, easy sipping. Snork was mild for the most part and became a bit more lively towards the end. Burn was just on the cooler side of normal for me. One relight, no dottle, no gurgle. I did get a blockage at one point where a bit of baccy hard gotten into the airway. I thought it was the onset of some gurgle at first, but the pipe cleaner came out dry with almost no stain.

I've wrapped it up in some baking paper for now, and stuck it in a jar...

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It feels slightly compressible between the fingers, so I'm not sure if it has expanded a little since being removed from the press. If it does expand, it should be evident in the wrapping (which will tighten, tape get strained, etc).

I need to think of a way to prepare it for smoking. Technically, it's not a plug because it's made from ribbon cut (even though I'm tempted to call it a plug anyway), so taking thin slices is likely to result in small fragments rather than short strands. I'm thinking maybe thicker slices, and then either breaking some off, or cutting it into little square pillars and rubbing them out. I can work out a size for these once I have an idea of what it takes to fill a bowl (bearing in mind that the trimmings might have been more dense than the bulk of it). In other words, weigh the block and divide that by the weight that goes into a bowl to find out how many bowls it will fill, then work out what slice/pillar thickness is needed to cut the block into that that many pieces. Thick slices or squareish pillars will minimise the fragmentation of the ribbon cut strands that went into it, which should mean that the structure once rubbed out and packed into a bowl should be more smokable.

I had a look at the sleeve, and one bit of the beech has what looks like a thin vertical crack at the line between the screws. I haven't taken the other side off yet, so don't know what the rest is like. So far, it looks like I'll need to make another beech end piece. I plan to replace the lower screws with 80mm long M6 bolts near the bottom (at least two at each end). Based on the apparent damage and the block of tobacco that I got from the amount of compression that was applied (it looks and feels like a good block, and I don't think more compression is needed), I'm pretty confident that drilling through all of the wood and fitting bolts will be strong enough. The failure occurred because there was insufficient strength in the structure from the screws, and that strength was placed too high. Through bolts will be much stronger, as will increasing their diameter to M6, doubling them up, and placing them closer to where the forces are applied at the critical part of the compression cycle. In short, I'm pretty sure that it will be at least an order of magnitude stronger, and that should be more than enough to counteract the effects of the compression (which didn't result in massive damage).
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Re: Tobacco Press

Postby Nomad » Wed Aug 09, 2017 9:35 pm

I had a closer look at the sleeve, and found that what I thought was a crack was actually a pencil line I had made when marking out the hole positions. I also took the rest of it apart, and didn't find anything amiss. I reckon the cracking sounds were actually caused by the beech parts sliding a little against the ply - the pressure increases until the friction is overcome, the part moves and, as soon as it does, room is made and the pressure acting on it is reduced. So, a series of little moves resulting from adding more pressure as the bolts were tightened.

So I screwed it all back together and drilled six 6mm holes all the way through, and fitted six M6 coach bolts (because that's what I had lying around)...

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And the other side...

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If you look at the screws and the coach bolt in front, it should be clear that the bolts will be far stronger. Not only do they have far more cross sectional area, they span across the whole sandwich of three pieces of wood, and clamp them all together. With the screws, it was like having two thin pins per side that were made to bend in the middle, and the clamping force was only what the screw threads could get by biting into the beech. The beech parts might move out a little to take up space between the insides of the holes and the bolts, but shouldn't move any further after that. It's very unlikely that the ply sides will splay at all, although a small amount of bowing in the lower middle might happen.

I'll have to wait until the next pressing to see if it works, and I don't know yet when that will be. The main plan for this is to make something akin to a navy plug (or cake, strictly speaking), and that will take some development to get a blend suitable for adding rum to. Aside from that, I need to check out the block of Gravedigger that I've made in case anything needs to change (or even if it's worth pursuing further).
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Re: Tobacco Press

Postby Geo3rge » Thu Aug 10, 2017 6:22 am

Super post again, Nomad. Your illustrations are xcellent. Love reading how the block or plug turns out and its consistency and texture.
What a project this has become. All credit to you for doing it, working through the technical issues and making adjustments as you go along. A real eye-opener for anyone who hasn't done anything like this themselves.
Good luck with the developments, tweaks, adjustments etc, and, of course, the smoking!
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Re: Tobacco Press

Postby Listener666 » Thu Aug 10, 2017 5:49 pm

Good work............
Interesting to see that the Nuts and Bolts that apply the pressure didn't sink into the plywood to far, I would have thought that a much larger washer was needed to distribute the force across the surface....but obviously not, as enough pressure was applied and the result looks pretty damned good to me.

I use a ....erm....."disposable" press :oops: ...( slightly different sized baccy tins and 3 G clamps) looks odd but works well enough to form a sort of roundish cake.
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