Sunday 28 June 2020

help me choose a scooter

One of the most common questions is:
Help my choose a scooter

Really there's so much personal in that but if you strip away your own desires for how it looks and focus on what you need of it (performance) then you can set yourself up pretty well for dismissing lots, leaving more time to enjoying life on your scooter (rather than fussing about what to buy with no actual criteria to help you).

I wanted something which could fold and fit in my car, not break my back putting it there and climb the hills around where I lived. I ended up with this


So what you want it to look like aside, to me the best you can hope for is to use your own understandings of physics and make some educated guesses based on specs.  Weight of the scoot is pretty straighforward, but what's often difficult is "range and speed" (and often forgotten is hill climbing).

For instance its well understood what energy is needed to get a human body up a hill on a 2 wheeled machine, cyclists have been into this for decades and there are good online calculators: I've used this one. Those are actually my parameters and have proven very consistent in estimating my scooters (all of them). About a year back I put this blog post together to understand my scooter (then the 500W Mercane single motor) and then estimate if the 1000W dual motor (otherwise the same as the single) would give me better hill climbing (speeds on the flat were essentially firmware limited to comply with the law) and be worth my while buying.

For instance in my parameters above I picked 8% because that's not steep:
... Maximum slope for hand-propelled wheelchair ramps should 4.8 degree angle or 8.3% grade. Maximum slope for power chairs should be 7.1 degree angle; 12.5% grade.

my driveway is more than twice that and so is the top of my street. So I needed more and so plugged in higher numbers into that calculator above and it was pretty clear what I needed.

Plug in your own weight and see what you should need in terms of battery capacity even for just "regular riding" (meaning not climbing steep hills if you don't have them). You'll also see that as you go faster (even on a flat) more power is needed, its not a linear relationship (meaning that to go twice as fast you need a LOT more than twice the power). Power is best measured in Watts (unless you ride horses ... then I suppose Horse Power makes some sense).

Next you'll put that requirement (of power) into a simple calculation of how many Watt hours (its simple because if you use 400Watts to maintain a speed for an hour you'll need 400 Watt hours (Wh). The faster you want to go the more Wh you'll use (even per distance) because physics is a harsh mistress, you can dream any wanking you like, but she won't let you live it out.

My Mercane Widewheel cost AU$1400 weighs 24kg and has a 633Wh battery. However the reality is you can't get more than 70% out of a battery (without probably walking) and you probably shouldn't run it that flat often anway. So that means a usable Wh from my battery 450Wh ... which I don't usually push it that deeply (but go close).

That'll allow me to do this, and learn from that to make this estimate of 1.96kWh / 100km  As well as informing me about how to make further decisions. 

So from this you should now be able to make some informed decisions about what power you need and how much battery capacity you need for that task (and your range).

In contrast my Mercane MX60 has a 1200Wh battery (which for a reality check is not far from the size used in a Hybrid Car), the scooter cost me AU$3000 and gives a usable range of 30km (probably more if I was willing to risk having to push it and go slower). But at 34kg its bloody heavy to lift and I seldom take it anywhere in the car (and thank Gawd that my house is low set or it wouldn't even be an option), which I indeed do with the Widewheel. I mainly use it on the weekends now as I actually don't like the fact that its so much higher than the widewheel, even if it cruises bumpy roads better.

So everything is a trade off, if you want more power you'll have a bigger thing (kids today probably don't work on engines of cars anymore and so this is perhaps not obvious):


If you want to go faster you'll need:
  • more power
  • bigger battery (to deliver more power and longer if you want any range)
  • better suspension
  • better wheels
  • stronger chassis
  • good steering dynamics (better read this, scooter folks seem ignorant of this point)
and that will cost you more money and a penalty of greater weight (because physics is a harsh mistress).

Next we come to the old chestnut of tyres; I was 100% clear (after many years of bicycles and motorcycles) that I did not want pneumatic tyres on my scooter for work commuting. Flats are inevitable and and more pronounced with smaller wheels and much harder to fix with smaller wheels.


I subsequently bought a scooter as a "fun thing" which did have pneumatic tyres (the MX60 above) and in less time I've changed more tyres and had more struggle with that than the entire amount of time spent on the Widewheel.




think about that...

Thus we come back to the beginning where I suggested "focus on what you need of it" not the wanking of how it looks in pictures. Ask yourself:
  • will I need to carry it (or push it)
  • do I need the range (if yes perhaps look carefully at an eBike or (gosh) a motorbike)
  • how much am I willing to spend (as much as a motorcycle)?
Lastly (hopefully you read the other ones), I recommend you read these two about scoots and reality, and then read this post for thoughts. It will perhaps help you to understand your needs and see the experiences of somone who has probably used a bigger variety of 2 wheeled transport for quite some time.

Teach a Man to Fish ... Time for a beer I say, and I know which scoot it'll be that I take ;-)


Happy Scooting

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