Making something workable out of it isn't hard. I have created a flawed worksheet to quickly calculate min and max weights for all the interesting cycle delays, impulses and possible frictions (really just 4/5 of track stops and a floor tile), but...

Lets take a really simple cycle:

buildings over tracks and ramps:

╔^

▲S˘▼

track

╔ ╗

||+==

Carts on Track stop and hatch, walls as necessary. Cart paths should be obvious.

When hatch is opened, the cart takes 26 steps to deliver the first push and then delivers one every 18 steps thereafter.

With this design, the input for equal weight is 29310 - just have to do floor(29310×weight of light cart/weight of heavy cart) for the speed of heavy cart. Then heavy cart moves as it's speed dictates, first losing friction and then taking the move if there's anything left over for each turn.

Technically an arithmetic sum, but for low cycle lengths(<33) you can use high friction track stop and higher cycles generally work best with medium track stops as far as minimizing weight required goes, which conveniently makes the arithmetic sum 1 deep, meaning just heavy cart speed - friction.

Ok, so, lets say I want to use it for waving a bridge. 200/18=11,11....So 12 pushes per cycle. 50000 length, so the cart must traverse between ceil(50000/12) and floor(50000/11) tiles each time - that is, between 4167 and 4545 tiles. All friction options below highest can work (if it was elastic, highest would work too for heavy cart pushing on light one), but a high friction track stop will work for just a single push with the lightest cart - required speed being 10000 greater, so for standard 24 urist wooden minecart the respective max and min weights are 49,6364...(floored to 49. You

**cannot** use minecart collisions to measure the weight of single ultra-light thing) and 48,3465...(ceil'd to 49).

Tested this with loading the heavy cart with a bucket and second minecart. Cart moves 4355 sub-tiles per push, the heavy cart moves onto ramp 211 steps after hatch opens, and takes 11 steps to hit the plate....Excellent for a timer originally conceived for locking dwarves in rooms for long periods, but if you realized that it will vary due north-south sub-tile positions and fail to accumulate enough acceleration to complete cycle in less than 18 steps on 3rd bridge wave, give yourself a cookie

Of course, you can also take given convenient heavy cart you have and alter how often or how big you deliver an impulse, or alternatively use the heavy cart to propagate another signal. If I had used platinum cart for the above, I'd have gotten 321 sub-tiles per move with medium friction stop, for 156 cycle length - ok so that'd need a roller to deliver signals at reasonable bridge-wave pace, which would alter push impulse due the tiers not fitting, and...

It might be easier to mess with weight, though - more compact, and can just look up wiki's

weight and

density for most things, instead of fiddling to get a push with correct impulse and delay.

**EDIT**:29310, not 29300. Forgot to account for floor friction with younger cart pushing on older ^^;