You need bones with knuckles and cartilage to get the gel.

The best beef stock, imho, will be made with a mix of bones, meat and cartilage. The best flavor I've gotten has been from a big joint like the top of the femur plus a few cuts of shank with some good trimmings on them; you can also add some short ribs if you're short on meat. Brown bones at about 350°F. 400°F sounds a bit high to me, they caramelize a little more nicely a bit lower. Scrape the roasting pan too and add all the bits into the broth pot.

I never, ever add raw onions to a broth pot or slow-cooker recipe. You could quarter the onions and put them in with the roasting bones or sometimes I just toss them in one of my cast irons for a few minutes on medium-low and cook them until they're at least a bit translucent. Raw onion will make for bitter bitter results. Add a sprig of thyme for about every 2 to 3 lbs of bones and meat.

I have had good stock after 12 hours but I think the recommends for 24 hours are good. I usually use my slow-cooker so I can leave it sitting without worrying about it boiling dry. Skim any foamy, "scummy" looking stuff that comes to the top that you can; you don't need to be OCD but get some of that stuff out. I also let it cool in my slowcooker. I just let it set for hours, I want it room temp before I put it in my fridge.

On top of all this, I don't usually have broth plain. I almost always use it as a base for something else - either gravy or a pureed veggie soup. I don't particularly like it by itself. hth

It may have needed more time, since you mention lack of gelatin in your finished broth. 12 hours does not seem long enough to me. I usually simmer at least 24 hours, often much longer, in a crock pot. Some people don't like to add vegetables early in the process because the long cooking time can make them bitter. You didn't mention salt which makes a big difference in flavor. Just some thoughts, hope they're helpful.

I make stock - 1 leg bone from a cooked lamb roast + some chicken bones (like a carcass, or 6 boned chicken somethings). Both with a little meat on. Slow rolling gentle boil for maybe 3-4 hours or so (prolly did mine for about 4). Came out plenty gelatiny for me, doing this. Like a jelly almost, but kinda like wobbly gelatiny puree sorta.

Then I just use that stock for making stews and soups (or just flavouring other dishes). Worked beautifully for the stew I made last week. Still have a cup of stock I want to use for soup, and going to make some more stock this week for more stew :)

I am not sure what the difference is between a broth and a stock, but I just followed an online recipe for cheap stock using bones that still have some meat on (which may even be half stock, half broth) and it turned out great.

Not sure why anyone would want to just use broth or stock as a drink tho, when whatever the heck its called is great in an actual meal. Is it nice as a drink normally BTW??

I cant say what went wrong with yours, when I tried initially to make one of these bone broths I used uncooked beef bones, simmered for like 8 hours and i didnt even drink/eat it. It came out totally gross, foul smelling, and not even gelatiny. I think using cooked bones with a little meat on them is the trick myself, going on my very limited experience. (I didnt use vinegar in mine, and didnt boil for that long either, and it worked out very gelatiny and great tasting)

Beef broth usually needs 24 hours, so try cooking it longer.

Also, beef broth has a totally different taste than chicken broth, and can be a bit harsh. Beef broth tastes a little bit better if there is some meat left on the bones. I use my beef broth mostly for cooking and soups, fish broth for strongly flavored soups, and only drink chicken broth straight.

It's also possible that you let the water temperature get too hot and you "burned" your gelatin. When making bone broth, it's a good idea to get a mix of bones from the neck, feet, joints and other parts.

I usually add in some gelatin like pork feet they work great, you can try ox tail or some meaty soup bones as well. There is some good info at the healthy home economist.

http://www.thehealthyhomeeconomist.com/5-reasons-why-your-stock-wont-gel/

I get much better broth in my pressure cooker than from a stock pot or crockpot.

I throw as many bones as will fit. I like oxtails if I have them, or bones from ribs, plus marrow bones, left over chicken carcass etc. Super duper bonus gel points if you can find chicken feet - you can even order them from grassland beef if you're so inclined.

Add a splash of apple cider vinegar. I like to put in a couple of bay leaves in my broth and a little salt. more extra bonus points if, instead of salt, you add a splash of fish sauce. Red boat is yummy and paleo friendly.

Cover bones, carcass, feet, etc. with water to the fill line.

Cook on high pressure for an hour to an hour and a half.

Remove from heat. I use natural release, but haven't tested it against other methods.

Strain broth through sieve to remove bay leaves, etc.

pick out random pieces of meat which were left on bones.

eat them.

curse that you burnt your tongue.

Eat another piece, cause the last one was yummy.

curse again.

Refrigerate over night.

The next morning, remove the satisfyingly icky layer of fat which has formed.

Enjoy your delicious bone broth goodness.

If you're just using marrow bones, you don't need to cook it very long. I just throw away the marrow bones after pushing out the marrows after about 2 hours. It's not the same as boiling ribs or other smaller bones which do dissolve. The marrow bones are pretty clear after the marrows come out. You can use a knife and detach some tendons and ligaments, however, and throw them in the broth. But it's my opinion that the marrow bones are useless once the core is pushed out. Anyone who disagrees please distinguish between marrow and other bones.

You can boil the broth for a few hours. I always use about 2 lbs. of marrow bones and boil for 2-4 hours. That has always been sufficient to produce the gel-llike product.

12 hours is definitely not long enough for large bones like that, at least in my experience... I tried 12 hours once and ended up with cloudy water. Try simmering for 24 hours at least, and towards the end I always stir things around and pull the marrow out of the bones so that it can mix into the broth!