Artemis BJJ (MYGYM Bristol), Can Sönmez, Bristol, UK - 09/12/2015
The tripod sweep I always teach in a previous lesson combines well with the similar sickle sweep: as usual in BJJ, that almost certainly has other names (the most common alternative is 'hook sweep'), but I'm using the term from Theory & Technique (page 226). A good time to try this is if when you attempt the tripod sweep, they kick their leg free from your hooking hand. You could attempt to readjust to recover your position, but it is probably easier to pull yourself towards their other leg with your hooking foot, grabbing the heel on that side. Turn your body toward that newly grabbed leg, swinging your pushing foot over to that hip. With what used to be your hooking foot, chop back low on their other leg to knock them over.
Of course, the sickle works on its own too. Indeed, Rener teaches this before the tripod on Gracie University. The entry he shows is to hook their leg, pulling yourself in to grab their ankle, then switching into the sickle position: opposite foot on the ankle-grabbed side hip, then chopping low on their other leg with your remaining leg, using your calf or possibly your heel.
In order to get the angle, you'll have to turn towards them, or hook their leg to pull yourself in. If you're going from the tripod, you'll already have their leg hooked. Note that when you follow them up after knocking them to their back, compared to the tripod sweep, your other knee will be raised. That means you'll need to make sure to shove their leg down and step over, enabling you to complete your knee slide.
While grabbing the heel is a perfectly viable grip, it is probably better suited to the tripod, as then you can use Kev's trick of jamming the heel against your hip. With the sickle your body is turned, so that's not easy to do. I'd therefore recommend grabbing the trouser leg for the sickle. That's because it means that once you've knocked them over, you can pin their leg to the mat while also pushing it away. That stops them from closing their guard. This is important, because the sickle sweep will generally put you in a position with one leg in between theirs. Wait as long as possible to let go of the trouser grip: ideally, you want to wait until you've slid your leg out.
For finishing the sweep, I think with the sickle sweep, technical stand up works especially well. Base on the hand that's grabbing their trouser leg, also basing with your opposite foot. Use that to then bring your same side leg back and stand up. As you stand, thrust their leg into the air with your hand (you can bolster that by grabbing with your other hand too) and move around. It's really hard for them to do much if their leg is way up in the air like that, so passing should be fairly easy.
Teaching Notes: As with the tripod sweep last time, I focused on one method of getting up. I included a technical stand up drill in the warm up too. However, I'm not totally sure that it is a technical stand-up motion on this one (though perhaps it is when you're doing the tripod sweep). When I do, I find that I removed my foot from the hip as I knock them over, already beginning to move back and stand up as they fall down.
But either way, keeping hold of their foot is important, to hinder their own attempts to get up. That's why I emphasise grabbing the trouser leg on the sickle, rather than the heel on the tripod. Heel and trouser leg work fine for both sweeps, but in my experience, heel is better suited to the tripod. Your mileage may vary. :)