Monster 84volt top speed

[Bri]

I’m curious what others have for a top speed on their Monster V3 84volt?  I’ve hit 32.7 mph (DarknessBot) as my top speed and wondering if I can push it some more. 

[Aneta]

Within small vicinity of max speed (where max motor thrust is equal to load = air drag + rolling resistance) both thrust vs. speed (falling approx. linearly with speed) and load vs. speed (rising approx. as a square of speed) can be approximated by linear functions, so if theoretical max speed is Vmax, and your trust margin at 32.7mph is Tmargin(32.7), then at speed 32.7<V<Vmax the thrust margin will shrink proportionally to how close V is to Vmax: Tmargin(V) = Tmargin(32.7)*(Vmax - V)/(Vmax - 32.7). Suppose Vmax is 38mph, you're trying to ride at 35mph, your margin Tmargin(35) = Tmargin(32.7)*(38 - 35)/(38 - 32.7) = 0.57*Tmargin(32.7). You decreased your thrust margin by almost half! If it was 5lbs, you now have only less than 3lbs of thrust margin, which means that even slight bumps can faceplant you. You get to your destination only 35/32.7 = 7% faster, but you're sacrificing 43% of your safety margin! The closer you get to The Edge, the more diminishing are the returns and the risk grows exponentially hyperbolically.

Be safe. It's not worth it...

[Chriull]

Here you have a current (burden) over speed diagram of an MSX 84V

Afair the right line were all the other lines end is the limit for 84.2V battery voltage.

So, yes you can push the MSX far over 32.7mph (53.2 kph) if you keep the burden low. But evety incline, wind burst, instability, acceleration will bring you down...

52.3 kph seem to have still some nice reserves (at full batteties!)

[meepmeepmayer]

Going by the Gotway-designed speed beeps, the Monster 84V has speed beeps at 55kph (34.1mph) at 100% battery, going down to 43kph (27.72mph) at 10% battery (source).

[Bri]

Meepmeepmayer thanks that’s what I was looking for. I currently have my warning set at 30 mph but have gone over a few times and definitely not trying to have a cut out. I always respect the beeps! 

[meepmeepmayer]

Standard disclaimer because why not:

As always with EUCs, there are no guarantees. The Gotway beeps seem to be at something like 80% (or some number, but they call it "80% alarm") of the current maximum speed. This max speed is a clean, predictable quantity (for a given motor it only depends on voltage = battery percentage), so this is a great method to restrict speeds (KS does the same with an extra fixed max speed added).

A sudden acceleration/bump/spike at ~80% (or whatever the number is) can easily add the 20% to produce an overlean, though.

So I'm saying it can never hurt (literally) to give yourself some margin. The faster you are, the less margin you have, simple as that. So how fast you want to go is your decision (also depends on rider weight - lighter riders can ride the beeps, while heavier riders should be a bit more conservative).

Edited January 7, 2020 by meepmeepmayer

[Aneta]

Approaching max theoretical speed (overlean speed) can be likened to climbing El Capitan with a set of 50m-long fixed ropes. Ropes are already attached to anchors every 50m, all you have to do is to pull yourself up. But there's a caveat: each rope is progressively thinner. You weigh 100kg, the bottom very thick rope can hold 1000kg - no problem. The rope in the middle of El Cap can hold 550kg. Still plenty. The last rope just before the summit can hold exactly 100kg. How close you will dare to approach the coveted summit? Will you stop on the rope that can hold 200kg? 150kg? 120kg? 110kg? ... What if that 150kg rope has a defect that makes it weaker? What if you're on that 110kg rope, and the gust of wind starts swinging you, increasing the load?

Athletes of many extreme sports have this saying, "Better be safe than sorry."

Edited January 7, 2020 by Aneta

[Bri]

Aneta nice analogy, thanks.

[Aneta]

Oops, I totally missed in my climbing analogy that not only ropes get thinner as you climb higher, but your weight increases as you go up. (perhaps, you're collecting waste from unethical climbers left on the mountain) Moreover, while the rope load rating decreases linearly with height (y ~ 1 - x), your weight increases quadratically (y ~ x^2)! (there's more waste the higher you go) - this is analogous to air drag increasing proportionally with the square of speed. Wowza! It's like a candle burning on both ends, but one end is accelerating! Talk about adding an insult to the injury! So, it's more like your weight is already 400kg, and the rope you're hanging on to is rated at 550kg, and you continue climbing to the point where your weight will be 500, and the rope is also 500... "Oh, snap!"

[Ben Kim]

it’s really not rocket science when it comes to Gotway wheels. 80% alarm = 20% more speed before your face meets pavement. Proceed at your own risk. 

To mitigate the risk of a high speed faceplant pushing the 80% alarm, you should briskly accelerate to prevent sag before punching it. Superman leaning from a dead stop gives you less room to play with up top. 

There are a good number of folks who have pushed upwards of 45 MPH on a Monster 100V, and also saw one guy in Asia attain 49 MPH on his 100V MSX before he cut out.

With that said, the fastest I’ve taken my 100V Monster was 40.4 MPH. 

If you can get 34MPH out of an 84V Monster before the 80% alarm, you have another 6-7 MPH to play with (NOT RECOMMENDED!)

Edited January 14, 2020 by Ben Kim

[mrelwood]

8 hours ago, Ben Kim said:

it’s really not rocket science when it comes to Gotway wheels. 80% alarm = 20% more speed before your face meets pavement. Proceed at your own risk.

Own risk indeed. But the 20% is only true if you weigh 0 and have the wind on your back. And there are no bumps. Since all of us weigh a bit more than 0 though, the math does get a lot more complicated right there.

[Ben Kim]

2 hours ago, mrelwood said:

Own risk indeed. But the 20% is only true if you weigh 0 and have the wind on your back. And there are no bumps. Since all of us weigh a bit more than 0 though, the math does get a lot more complicated right there.

lot of factors at play honestly, but most relate to state of charge, someone who superman leans into their wheel all the time will have a lower cutout point than someone who briskly accelerates.