Mid-Drive vs DD

I was messing around with the motor simulator. I thought for sure the Stoke Monkey was a Mid Drive system, would produce a ton more N-m then my DD.



I posted a link up earlier about a custom freewheel crank setup. For a measley, $25 from SickBikeParts you can buy the freewheel unit, buy a sprocket used for gassers on the rear wheel, and fab up your own crank and bam, you got a 4 geared crank, in which you can use all your gears in the back. I mean that is crazy, you could go from uber fast, to super torquey in the matter of a few gear changes.

Far better is uber fast and super torquey with NO GEAR CHANGES, which also can mean absolute reliability instead of suspect durability.

markz said:

I was messing around with the motor simulator. I thought for sure the Stoke Monkey was a Mid Drive system, would produce a ton more N-m then my DD.

Click to expand...

Your simulation does not take into account the gear ratio of the mid-drive - you have used a straight 1:1 motor-to-wheel ratio. This is similar to operating the SM in high gear - speed, not torque. Also, the motor torque does not change but the forward force does - you need to adjust the simulator Blue Curve for 'Lbs Thrust'.

Since the simulator does not directly allow gearing specification, you obtain the same result by making an appropriate alteration to wheel size. Here's some effective wheel sizes using a Shimano 14-28 drive and a SM 16/50 cog setup - your particular cogs/chainrings may differ.


As you can see, the lowest gear setup is the same as having a tiny 8.9" wheel.
Use the gray cells and plug in the the appropriate 'Effective Wheel Diameter' for any chainring/cog combination into the simulator and see what pops out...

If you go with a mega range cluster you get more thrust (as expected)...

So on the lowest "wheel size" of lets just round to 8" for the Stoke Monkey 8x8......
View attachment 1
The Torque or Thrust is outrageous, about double.
The Speed is about the same at the 29" range. 52 compared to 59km/h.


Can climb some steep grades without no overheating.

Yup. Try plugging in a 20% grade, like I see around here. Unless you are going to run 72-100 volts, or 60-100 amp controller, you won't keep a DD hub motor rpm up high enough to keep it from becoming a toaster oven. And at those power levels you will be eating Wh's like candy.

I put in 20% grade and 772lbs of weight. Overheats in 1 minute.
330lbs is 9 minutes until it overheats.

Very interesting results. If I want a hill climber a mid drive would work out just fine. Now if I did the same with the MXUS 4506 v2 motor. 330lbs at 20% never overheats.
772lbs and 20%, 9 minutes until it over heats.

Amazing!

Are you suggesting using the mxus as a middrive? That would be interesting......

Not anything to do with our OP but I thought this is a good place to post something I have noticed lately.

I don't know if anyone else has noticed but I have noticed theres a lot of new folks with very newly joined dates on their es account name that come on here and ask questions for their mid-drives.

I recon why so many newbs are starting off with mid-drives is based on a similar information path I found when I built my first ebike (which was a hub motor) and that is when I first started searching the web for ebikes I was getting bombarded with ads from mid-drive sellers and their torque graphs showing their mid-drive crushing a DD hub which I am guessing is a non-existent DD hub from 10 years ago. Whether it is complete bikes like Aseako or kits like BaFang,Cyclone mid-drives I think they are turning the tide for ebike firsties.

Anyway when you see those torque crushing graphs everywhere of mid-drives vs hubs its easy to get convinced you must get a mid-drive period and thats why I think we see so many newly registered accounts asking Qs on their mid-drives.

I was thinking it's because middrives offer more bike-like handling and performance, although they tend to be more limited in strength for high power setups (+3k).

The simplest way I can think of to understand torque is:
Whether we are comparing 1 or 10k setups, if power setups are equal the one with the lower gearing will always have more torque. There are nuances such as hubs having more rotating mass, motor effeciency etc, but in general gearing is the best rule of thumb.

5k geared for 40mph will have more torque than 5k geared for 60mph.

This is my 5k parallel middrive geared for 40- If I were to gear it up to compare with a 5k hub of 60mph or similar speed, the torque winner would mainly be decided by minor details/nuances.
https://www.youtube.com/watch?v=In52NPeGUOc
When taking into account a serial middrive can gear down much lower than mine by using bike gears for 1/1, I would assume there would be even more torque, although application in velocity range is limited by running through the gears.

nutspecial said:

The simplest way I can think of to understand torque is:
Whether we are comparing 1 or 10k setups, if power setups are equal the one with the lower gearing will always have more torque. There are nuances such as hubs having more rotating mass, motor effeciency etc, but in general gearing is the best rule of thumb.

Click to expand...

It is an "ok" rule of thumb, but it misses a lot of things that could make a much more powerful system far less torquey than a much less powerful system, even comparing hubs to hubs and MDs to MDs.

There's a few long technical threads (some of which are not titled for it, so hard to find, so I don't have any links ATM) around discussing why, but the basics are things like how the motor is wound, stator/magnet width, lamination type/thickness (affects efficiency, thus how much of the power input actually goes to the ground), etc. Some of those "act" like gearing, in how they affect performance, but they aren't actually gearing.

Correct, thanks. I was just tryin to simplify as much as possible for the layman (like me). So I'm close anyway.

What about this scenario (since there are no 5kw serial middrives I'm aware of, so my earlier point is kinda more me understanding my own performance, and trying to guess @ tru middrives vs hubs),

2kw hub and serial middrive.
Both motors using same voltage and amperage. Similar enough performing motors in terms of their engineering (this is possible right?)

Hub has optimal wind for power and desired speed, which is acheived finally by a wheel size. Say 40mph

Middrive with a medium(assume stock)wind can achieve very similar results in torque and speed by it's chosen reduction ratio and wheelsize.
Also, it can change the final reduction @deraileur, so It has the potential to multiply torque when that final ratio changes from 4/1 to 1/1.

Is that an acceptable expectation of dd hub vs middrive torque?