How much would a typical grain bill for a 5g batch weigh after it is drained? I am just looking for a ball park figure. Looking at throwing together a biab system and I would like to use a simple rope hoist to lift the grains out of the kettle to let them drain. Once the grains are out of kettle I will fire up the element and continue on up to boiling temp. Before boiling I would like to be able to remove the grains and toss them in the trash. Approximately how much should I expect them to weigh at that point?
BIAB spent grain weight?
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Grain absorbs about .12 gal of water per lb. That's close enough to call it a pound. So, about a pound of water per pound of grain.
deadwolfbones
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fwiw, I squeeze the hell out of my bag and my best estimate of my absorption is .03 gal/lb. So it can be quite a lot lighter than a pound of water per pound of grain.
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What you need to know is the initial weight of bag, grain and wort when you first lift the bag from the kettle. This is when it weighs the most and is the most strain on your clasp, pulley, and rope.
Start with your maximum grain bill, which will be partially based upon your mash/lauter efficiency. Figure that the water weight will be approximately the same as the grain weight when you first start to lift it. Add some for stress, temperature, and safety factor.
Start with your maximum grain bill, which will be partially based upon your mash/lauter efficiency. Figure that the water weight will be approximately the same as the grain weight when you first start to lift it. Add some for stress, temperature, and safety factor.
And subtract weight of sugar extracted 
Most any simple pulley is adequate for 5 gal batches ... 10-20 gal batches get a little more tricky.
A ratchet pulley works very well, a double ratchet pulley works even better w/ 2-1 mechanical advantage.
Most any simple pulley is adequate for 5 gal batches ... 10-20 gal batches get a little more tricky.
A ratchet pulley works very well, a double ratchet pulley works even better w/ 2-1 mechanical advantage.
Unless you are really trying to skimp on equipment you should have more trouble undersizing your hoist than making it too capable.
I would go for a hoist with a larger line in it. It will be easier on you hands and easier to grip than a thin rope.
And yes, you are not concerned with the weight of the spent grain, you want to be looking at the weight of the wet grain.... As an estimate I would look toward the maximum amount of grain you would use then add about 24 pounds that would account for 3 gallons of water which should give a safety factor.
If the largest batch your pot could handle is 24 pounds, then add 24 pounds for water, so your hoist should be capable of lifting 48 pounds.
The one linked would handle 150 pounds.
I would go for a hoist with a larger line in it. It will be easier on you hands and easier to grip than a thin rope.
And yes, you are not concerned with the weight of the spent grain, you want to be looking at the weight of the wet grain.... As an estimate I would look toward the maximum amount of grain you would use then add about 24 pounds that would account for 3 gallons of water which should give a safety factor.
If the largest batch your pot could handle is 24 pounds, then add 24 pounds for water, so your hoist should be capable of lifting 48 pounds.
The one linked would handle 150 pounds.
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LittleRiver
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That's one of the best upgrades you can make to a BIAB rig. Add a second pulley to the rope ratchet rig that @camonick linked to above, and you'll be good to go. The second pulley will give you some mechanical advantage, and let you pull down rather than pull up when you lift the bag.
You want the ratcheting pulley down low, where you attach to the bag, so you can easily reach the ratchet release. Put the second pulley up at your anchor point. Tie off one end of the rope to the overhead anchor, run it down through the ratcheting pulley, then back up and through the pulley at the anchor.
Use a loop of cord to make a prusik hitch around the bag, and hook the ratcheting pulley to it. That will keep the ratchet pulley much lower than if you attach to the drawstring or straps of your bag.
If you let the bag hang over the kettle to gravity drain during the boil it will get cooler and lighter, which makes it easier to handle for disposal. It will also eliminate the need to squeeze the bag.
2 more things to think about. You don't have to raise the bag and all the water. Lift the bag a little, leaving the bulk of is suspended in the wort and let it drain some liquid. Lift it a little more and let it drain. Repeat until the bottom of the bag clears the liquid and you have lightened that bag a lot. This doesn't need to take a long time, you aren't getting rid of all the water possible, just some to lighten it. Now that you have the bag fully suspended it will continue to drain some more but not a great amount. Look at the amount of wort collected. If you are a bit short of desired, pour some water over that suspended bag as a sparge and get to your intended pre-boil amount and gain some more sugars at the same time.
I usually over-engineer things, so I really wasn't really too concerned about the weight of the wet grains. I know the rope hoist will be more the adequate to lift the weight. What I was more concerned with was the spent weight, I just didn't want it to be overly heavy when I unhook the grains to take them for disposal
How do you attach the hook to the bag?
I use a short piece of para-chord tied in a loop and use a prusik knot tied around the bag.
The “red” rope in the image would be your bag.
Maybe @wilserbrewer can elaborate on the technique.
The “red” rope in the image would be your bag.
Maybe @wilserbrewer can elaborate on the technique.
Great, thanks!
I thought about a connection like this but without the additional times the rope being twisted around the bag before going through the loop. This looks more stable than what I thought!
My loop of para-chord isn’t very long. I only run the loop back through itself once and have never had any problems.
If you have all of the specifics, this can be calculated. Let's look at a specific case:
BIAB, no-sparge
20 lb grains @ 4% moisture content
37 pts/lb potential
7.25 gal pre-boil volume
100% conversion efficiency
0.09 gal/lb apparent grain absorption
9.05 gal strike water
I'll skip the details of the math, but the basic results are:20 lb grains @ 4% moisture content
37 pts/lb potential
7.25 gal pre-boil volume
100% conversion efficiency
0.09 gal/lb apparent grain absorption
9.05 gal strike water
Dry weight of grain = 19.2 lb
Weight of grain converted = 14.82 lb
Weight of grain unconverted = 4.38 lb
Weight of wort retained in grain = 26.42 lb
Total weight of spent grain mass = 4.38 + 26.42 = 30.80 lb
If we look at a 10 lb grain bill with same pre-boil vol, conversion eff, and grain absorption, the total weight of the spent grain mass = 15.04 lbWeight of grain converted = 14.82 lb
Weight of grain unconverted = 4.38 lb
Weight of wort retained in grain = 26.42 lb
Total weight of spent grain mass = 4.38 + 26.42 = 30.80 lb
So, a rough approximation formula for spent grain weight would be:
Spent grain weight = 1.5 * Grain bill weight
Brew on
Nice work and maths Doug...I was tempted to reply that weight out will be a “bit” more than grain weight in but you drilled it down nicely....now if you could also calculate it as a time function of the bag draining I would be impressed lol but that would be like a fifth dimension function....
The end-points are relatively easy. Time to get between them, not so easy. Complete characteristic function, damn near impossible.
Brew on
As for the first end point, I know that trying to hoist very large grain bills quickly is an instant defeat....when full of grain and wort the bag seems like it is bolted to the bottom of the kettle....but hoisted slowly it becomes manageable a little bit at a time.
Couple clicks at a time w a ratchet pulley is key!
Couple clicks at a time w a ratchet pulley is key!
With my previous method I would squeeze until the weight was the same as the initial dry weight. (Yes the math does work to allow this)
This took a bit too long and was a bit too messy so I have changed my process to one seems to work even better.
(I do not have room so have add water after mash. I run this through the bag to rinse and don’t really worry about squeezing)
Tom
This took a bit too long and was a bit too messy so I have changed my process to one seems to work even better.
(I do not have room so have add water after mash. I run this through the bag to rinse and don’t really worry about squeezing)
Tom
HB2 HughBHomeBrew
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Here's what I just set up a few weeks ago and 3 5g batches ago. Simple pulley worked fine and should be no more than 20 lbs as posted above. I just use a cleat screwed to wall to hold it in place - that's about a $1.99 investment there - no need for a hitch at this weight.
I'm using gravity to go from BK to chiller to fermenter, and it just works out like this with the cooker and Kettle about 60 inches off the ground (this is a 10 foot ceiling in my garage).
Once the wet grain has been squeezed out, not too hard to just lower it and swing it over to a bucket on the ground.
I'm using gravity to go from BK to chiller to fermenter, and it just works out like this with the cooker and Kettle about 60 inches off the ground (this is a 10 foot ceiling in my garage).
Once the wet grain has been squeezed out, not too hard to just lower it and swing it over to a bucket on the ground.
Figure the average base malt is about 80% extract, let's call it 79% average with specialty grains, and a typical homebrew efficiency of 75% (or 25% left), spent grain is gonna weigh approximately 0.405 lb per original pound of grain bill. This is before water absorption. As said above, 0.12 gal/lb is typical water absorption, and at approximately 8.35 lb per gal, you're adding almost exactly 1 lb water per pound of original grain. That's if the water isn't squeezed out, mind you. So for an unsqueezed bag (or a traditional mash tun), multiply the weight of your grain bill by 1.4 and you've got your spent grain weight. If you squeeze the bag, and cut that absorption down, it could be significantly less than that.
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