Geared VS Direct Drive: Pros & Cons?

[alpharalpha]

I am looking at replacing my original direct drive front brush hub motor--which did require a larger front tire on the Trek Hybrid I had it on 38mm compared to rear 32mm, on a 700c rim. I have come across an inexpensive geared motor which on top of being inexpensive seems to take a narrower front wheel size. I live in very flat FL, would there be any benefit to a geared motor besides it being lighter? I'd think it would wear out faster, but the price is decent at around $250 for the complete kit (36v 500w). I never considered a geared motor and am just wondering what the pros and cons of them are compared to a direct drive one?

 

[amberwolf]

There's a number of threads about this topic; not everything in these lists is relevant, but you can generally see by title which ones have the answers you are after
https://endless-sphere.com/forums/search.php?keywords=gear*+direct*&terms=all&author=&sc=1&sf=titleonly&sr=topics&sk=t&sd=d&st=0&ch=300&t=0&submit=Search

The PHPBB search won't allow "DD" as an option, and the google search sucks for subject searches like this, but here's the results from one possible version of that:
https://endless-sphere.com/forums/app.php/googlesearch?cx=012839003547054862050%3Arcui7bzn6g8&q=%2Bgear*+vs*+DD*&t=0&submit=Search

 

[dogman dan]

Very flat means just about any motor will do, unless of course, you are very large.

The very small, very light geared motors do have definite limitations. They drag up hills of course, but they also struggle with very high winds, if you ever get that situation. I found them weak for the kind of wind I get here in the west.


Having ridden so many miles on 500w size dd motors, and the 500w size geared, I like each for different things. The lightness of the geared motor is really nice, but if you ride them fast, they do make some very noticeable noise at the top speed. But if you tend to mosey along at 15-18 mph pedaling hard, geared is very very nice.

But if you tend to ride like, pedal till you hit 25 mph then stop, go for a DD.


REAR motor, of course. I still say go rear motor if you can. Fronts are for weird belt drive bikes, adult delta trikes, and bikes with an IGH.

 

[docw009]

I'm biking for the exercise and also because I like biking with my wife. Smaller geared motors are enough to get us where we are going, and don't use much power. My wattmeter says under 10 wh/mile and 5 mile/AH are typical.

I suppose I would get more exercise pedaling a DD motor on idle, but I don't want that much.

If I were riding to work, and my old office is 8.1 miles away, I wouldn't mind a DD motor for some of the street riding.

 

[wturber]

I'm biking for the exercise and also because I like biking with my wife. Smaller geared motors are enough to get us where we are going, and don't use much power. My wattmeter says under 10 wh/mile and 5 mile/AH are typical.

Right. And they are usually easier to pedal than DD since they typically have a clutch of some kind so that they freewheel easier.

The use case is what should drive the motor and motor type choice.

 

[donn]

I suppose I would get more exercise pedaling a DD motor on idle, but I don't want that much.

You probably have an exaggerated impression of how much that is. But it's there, and I wonder if there's a potential for controller functionality there. A neutral load input, so for whatever speed the hub is rotating, just enough juice goes in to eliminate cogging drag.

 

[docw009]

I suppose I would get more exercise pedaling a DD motor on idle, but I don't want that much.

You probably have an exaggerated impression of how much that is. But it's there, and I wonder if there's a potential for controller functionality there. A neutral load input, so for whatever speed the hub is rotating, just enough juice goes in to eliminate cogging drag.

I am sure Tesla and all the e-car companies do that. Probably Bionx did too.

 

[wturber]

I suppose I would get more exercise pedaling a DD motor on idle, but I don't want that much.

You probably have an exaggerated impression of how much that is. But it's there, and I wonder if there's a potential for controller functionality there. A neutral load input, so for whatever speed the hub is rotating, just enough juice goes in to eliminate cogging drag.

That's possible - especially at slower speeds. Even if there was no cogging drag, the bike would seems slower just because of the added weight. So it is difficult to subjectively estimate what is cogging and what is from weight - especially when going uphill.

 

[amberwolf]

People have done it with teh Cycle analyst--ensuring throtle output during PAS is always *just* enough to overcome motor resistance. Then depending on desired operation, can get higher power the faster you pedal, ro the harder you pedal wit a torque sensor.

Could also be done with a switch on the throttle (using the ones that have a switch built in is handy, but might need rewiring from it's original purpose), to cut in a voltage divider in place of throttle signal that always outputs enough to overcome motor resistance, or to cut in a set of resistors on the throttle itself that offsets it's output signal voltage upward just a bit to do the same thing. For the latter you could isntead use the switch to enable/disable power to the throttle entirely, and leave the resistros in palce all the tiem.

I'm sure there's otehr ways, but those are off teh top of my head.

 

[RunForTheHills]

I thought you could estimate the cogging drag with the Grin motor simulator. Input a low percentage for the throttle, like 2-5% and the estimated motor power will be a negative number.

https://www.ebikes.ca/tools/simulat...14_14.8&cont=C35&axis=mph&throt=5&motor=M2705

 

[donn]

That's possible - especially at slower speeds. Even if there was no cogging drag, the bike would seems slower just because of the added weight. So it is difficult to subjectively estimate what is cogging and what is from weight - especially when going uphill.

That's sure how it feels to me. When I think I'm on really level ground, which doesn't happen so much around here, I don't feel it, but the slightest uphill grade really drags. But lots of people are 40 lbs heavier than me, and can still bicycle without great difficulty; you get a little of it back on the downhill. What people really don't like is the cogging drag that they've heard about.

 

[Sunder]

Like everyone said, the application drives which one is "better".

The only thing I think that hasn't been mentioned that is worth mentioning is that I felt my 1kw direct drive motor affected handling of the bike, especially at high speeds. One of the first times I used it at high speed, I tried to lean in to turn, and it didn't turn as mich as I expected, and I clipped a pole at 40-45km_h. Ouchies time.

The tiny cute motors never seemed to have thay effect, or maybe I was just used to it by the time I swapped over. This was like 10 years ago.

 

[Tommm]

If technically possible, mid is far superior. Better handling, lighter, much more torque with gearing, able to be liquid cooled. There is a reason Zero bikes, Harley, Lighting bikes all have mid drives.

 

[dogman dan]

Yep, a big heavy gyroscope on your wheel is hard to get leaned over. Gotta make good use of countersteering to initiate turns once you get to motorcycle speeds, and have a 20 pound motor on the wheel.

Most likely alpharaba will be quite happy with a tiny 350w rated geared motor. Only if he tends to ride into stiff headwinds at times will he feel its not enough.

But it does really all depend on the application. My long cruiser, which is designed as a trailer towing tractor, needs that huge 25 pound DD motor wheel on it. ( crystalyte 5304). I live in the rocky mountains, and get crazy hard winds, and then there is the towing sometimes.

Re the cogging, its a lot with this motor. The other day I blew it doing a battery capacity test, and ran out 4 miles from home. I reset the bms, and proceeded using the lowest wattage I could tickle out of the throttle. The really fun part, was the 20 mph headwind, with 40 mph gusts. I ran completely out, and had to ride that heavy motors stiff cogging into the wind for 3 miles, on a bike weighing at least 100 pounds. That was fun.

About the second mile, I reallllllllllllly wished I had been on my geared motor bike.

 

[MadRhino]

...There is a reason Zero bikes, Harley, Lighting bikes all have mid drives.

Weight is the reason.

Driving the chain has a neat advantage at both extremes of the power requirement.

Very low power, very light weight bikes.

Very high power, very heavy bikes.

In the middle, in the power range of big DD hubs, small mid dives are too weak and the big ones are too heavy. We have a zone, call it fast ebikes or ultra lightweight motorcycles, where a hub is advantageous in speed, power, efficiency and reliability.

Then, a company won’t make any profits in that class right now. So, either they go in ebike, or motorcycle. The in-between, fast ebike does remain in the hands of the DIY community.

 

[donn]

It's interesting enough for discussion, but I don't see motorcycles as an example of the same thing, because the whole drive train is designed from the start for the electric motor, only.

 

[wturber]

Then, a company won’t make any profits in that class right now. So, either they go in ebike, or motorcycle. The in-between, fast ebike does remain in the hands of the DIY community.

It also remains in the DIY community, I suspect, due to possible liability concerns as people will tend to tweak past the legal limits. And given the fuzziness of many of the existing definitions, then why go there. Sell a 500 watt (by some measure) bike and be done with it.

As more states adopt the three class system, we may start to see more Class 3 - semi fast ebikes.

 

[markz]

You may see that 3 class system in more states, but lets just hope it stays in the category of enforcement where snow removal of sidewalks is located, or the picking up of your dogs fecal matter, or license plate blockage (racks, hitch balls, radar reflectors screens), or come to a complete stop when at a stop sign, red light, or you must wait until the pedestrian is across the road before proceeding, or giving the bicyclist a meter of space.

Just ride with courtesy and be respectful!

As more states adopt the three class system, we may start to see more Class 3 - semi fast ebikes.

 

[dogman dan]

I like my states law a lot. Ebikes don't exist, all are mopeds. But nobody cares if you ride it on the trails that allow bikes, with reasonable courtesy. But it also means I can run up to 30 mph legal, and have as much power as I like. My bikes exceed class 3, and are completely street legal.

 

[alpharalpha]

I will be going with a front motor, is this then not a good option for the geared?

Very flat means just about any motor will do, unless of course, you are very large.

The very small, very light geared motors do have definite limitations. They drag up hills of course, but they also struggle with very high winds, if you ever get that situation. I found them weak for the kind of wind I get here in the west.


Having ridden so many miles on 500w size dd motors, and the 500w size geared, I like each for different things. The lightness of the geared motor is really nice, but if you ride them fast, they do make some very noticeable noise at the top speed. But if you tend to mosey along at 15-18 mph pedaling hard, geared is very very nice.

But if you tend to ride like, pedal till you hit 25 mph then stop, go for a DD.


REAR motor, of course. I still say go rear motor if you can. Fronts are for weird belt drive bikes, adult delta trikes, and bikes with an IGH.

 

[docw009]

I will be going with a front motor, is this then not a good option for the geared?

Your profile says Florida, and the biggest hill I ever encountered there were the causeway bridges. We have taken our 20" bikes down with small geared motors there the past two winters. About 500W max is the most I've seen on the display on those "hills", although a 20" wheel climbs well. Man, some of them bridges put the path on the edge and are are scary when the wind is blowing hard and you have an 80 foot dive if you fall over the barrier.

Unless there is some technical reason like an expensive gear or belt drive worth keeping, it's worth eliminating the fear of fork failure by going rear motor. Nonetheless, I did install a small geared motor on a front a year ago, with torque plates (over kill). I marked the nuts with a red sharpie pen and all I have to do is look at them before a ride, or during one to be reassured all is tight.

 

[alpharalpha]

I will be going with a front motor, is this then not a good option for the geared?

Your profile says Florida, and the biggest hill I ever encountered there were the causeway bridges. We have taken our 20" bikes down with small geared motors there the past two winters. About 500W max is the most I've seen on the display on those "hills", although a 20" wheel climbs well. Man, some of them bridges put the path on the edge and are are scary when the wind is blowing hard and you have an 80 foot dive if you fall over the barrier.

Unless there is some technical reason like an expensive gear or belt drive worth keeping, it's worth eliminating the fear of fork failure by going rear motor. Nonetheless, I did install a small geared motor on a front a year ago, with torque plates (over kill). I marked the nuts with a red sharpie pen and all I have to do is look at them before a ride, or during one to be reassured all is tight.

Which causeway bridge?

 

[docw009]

Sanibel was the first one we ever crossed. Caught some roadies at the top, but chose not to pass because I knew we would hold them up going downhill. Up here, the barriers are at least 5 feet high on bike bridges. Not used to my seat being almost at the same level as the railing on FL bridges.

The big Ringling bridge going west from Sarasota puts a wide bike lane far from the edge, but not protected from traffic. Still, there were lots of cyclists when we were there. Felt fine. We chickened out on the small bridge going west from Sarasota to Anna Marie Island. It was really windy that day and I felt like I was leaning into it.