after like 3 redesigns of the item collection system, i finally have something which has a large enough throughput. so here's a walk through of the entire process from slime spawn to storage
1. slime spawns, and targets the 40 iron golems which are placed around the farm. this causes it to fall onto the magma blocks ~5s
2. magma block kills slimes ~5s
3. hopper carts (8 of them) picks up slime balls. the track is 80m long, all powered rail, so the cart reaches its max speed of 8m/s, giving an average of 10s before pickup. cart pickup has pretty close to unlimited throughput. i think around 120 items per second.
4. moving hopper carts deposit into stationary hopper carts at the end of the track. this has a max throughput of around 160 items per second. the reason that stationary hopper carts are used rather than just hoppers is that stationary carts have a very high item throughput, useful for very bursty loads (which is the use case here). an average of 10s after item pickup.
5. stationary hopper carts deposit into hoppers at a slow but steady rate of 10 items/sec. there are 8 stationary hopper carts which deposit into 4 distinct hopper streams. on average, probably ~5 seconds are spend here
6. hopper streams transport item to 4 different droppers, which shoot the item into the item elevator. the droppers are hooked up to a fast pulsar and should have a throughput of 20 items/sec, so this does not bottleneck anything. probably 5s spend here
7. item travels up elevator to the water stream randomizer from a previous post. this takes another 10-15s. the item elevator and the water stream have unlimited bandwidth
8. item travels through one of 4 hopper streams to the storage. of course, since there are 4 distinct hopper streams, throughput is 10 items/sec again. latency of about 10s
so there is about a 1 minute latency between slime spawn -> slime ball enters storage, which is pretty cool to know.
to measure rates, which i discovered was pretty close to the max throughput of my collection system, i filled up one of the 4 hoppers where the stationary hopper carts dump into with 5 stacks of items. after 15 minutes, the hopper had 2 stacks less items. so 8 stacks per hour. since the throughput of a hopper is ~141 stacks per hour, i know that i'm using about 94.3% of the max hopper throughput, which would mean the farm produces 9.43 items/sec, for an hourly rate of ~34K slime balls or 10 double chests.
this calculation is sanity checked by the fact that i can see a full stack of 64 items exit the item elevator every 6 or 7 seconds, which corresponds to about 9-10 items/sec.
screenshot: view of farm when in operation
