DD and gear hub Ah compared on the same ride

[MikeSSS]

Geared hub is a front Bafang G311 on a 24" Townie. G311 is small and light, it has 11:1 gear reduction, helical cut gears, it's very quiet but provides surprising thrust, especially for its size and weight. Speed is limited to about 15 mph for the G311, by the possibility of throwing magnets, because of the 11:1 reduction. Controller is a Grinfineon 20A sinewave. Battery is 10s, 4p, 36v, 10ah, 360wh. Rider weight is 120 lb, water bottle is steel and weighs a couple pounds.

The direct drive is a Aotema brushless front hub, sensorless, capable of about 25 mph. It's not a really big DD hub but the front wheel weighs about 25 lb, with tire. Controller is whatever came with the used ebike I bought. It has an off and on switch on the controller. Battery is 13s, 4p, 48v, 13.5ah, 648wh. Bike is a Jamis Hudson, it's sort of like a Townie. Rider weighs about 190 lb, chain, cable and steel water bottle add a few pounds.

The ride was slow, 8.4 miles at an average of 9.4 mph. At this slow speed, the geared motor should be more efficient than the direct drive. Total weight was almost 100 lb less for the geared hub bike/rider and that bike had lower drag tires than the direct drive bike. There were several mild climbs and descents on the ride. Watt hours use were determined by timing the charge for both batteries, the 36v charged at 2 amps, the 48v at 3 amps. Both batteries were charged to less than full charge, so balancing time did not happen for either battery. The 48v battery was charged to 4.0 volts per cell, the 36v to 4.08 volts per cell.

Result: based on charge data, the geared hub bike used 80 Watt hours of charge, the direct drive bike used 96 Watt hours.

Yes, it's sort of apples to oranges comparison, because of the difference in weights, riding styles and tire rolling resistance. But, it seems to me that the geared hub is more efficient but probably not by a lot. Sadly I thought the iphone was left home, it wasn't, anyway I didn't use Strava so I don't know the elevation gained, but think it was about 200 ft. Using that elevation gain and estimated total weights of bike + rider + stuff, gives 12.4 Wh and 19.6 Wh of elevation gain for geared hub and direct drive. So, the direct drive bike used about 7.2 Wh more in climbing. That narrows the 16 Wh difference to 8.8 Watt hours. Consider the lower rolling resistance tires on the geared hub bike and the difference in Wh use is even smaller. Hmmm, perhaps these hubs are pretty close in efficiency. Close in efficiency even at low speed and low power use. More hmmm.

BTW, 2655 ftlb of elevation gain, gravitational potential energy, is about 1 Watt hour of energy.

 

[docw009]

My wife is 140-145. I'm 190-195, When we ride together, we have similar bikes with identical motors, BMSBattery Q100H, and similar 20A 6FET controllers except mine is sine wave, and hers is square wave. Average speed is between 11-12 mph, a one hour ride with only two stop lights.

She consistently uses less power than me, usually 6-7 WH/mile. I'm at 9-10 WH/mile. That's in inline with your geared vs DD results. I think it's weigh not efficiency.
.

 

[AHicks]

Switched from a Leaf 1500w (DD) to a GMAC 12t (geared hub) with no other changes. Ridden on the same routes in the same area (rolling coastal area, mostly 8 to 13mph in PAS 1), went from an easy 25 mile range to an easy 35 mile range. MUCH sportier performance at the lower speeds I ride most frequently, and MUCH better getting to the top of some of the bigger hills in the area. RAD City w/35a KT controller (set to 20a max) w/LCD3 display. I'm 6'2" 300 lbs.

 

[dogman dan]

Yeah, your test is junk science, with at least two variables. ( weight) But it still shows how little the difference should be, provided neither system was overloaded.

Where geared vs DD shows up different, is when the ride includes a stop every block, like riding parallel to a major street in many cities. A dang stop sign every block, because the traffic is supposed to flow easy to the big street.

I have seen up to 20% difference, particularly with that aotema, which hates to start up every block. The geared motor will start more efficient, and start to shine.

This is why I consistently advice a geared hub motor for any inner city riding, vs DD best for a 10 mile non stop ride to town.

 

[AHicks]

Yeah, your test is junk science, with at least two variables. ( weight) But it still shows how little the difference should be, provided neither system was overloaded.

Where geared vs DD shows up different, is when the ride includes a stop every block, like riding parallel to a major street in many cities. A dang stop sign every block, because the traffic is supposed to flow easy to the big street.

I have seen up to 20% difference, particularly with that aotema, which hates to start up every block. The geared motor will start more efficient, and start to shine.

This is why I consistently advice a geared hub motor for any inner city riding, vs DD best for a 10 mile non stop ride to town.

Not sure why you call my results "junk science". CLEARLY there's quite a bit of difference between the 2 types under the conditions I ride.

You say stop and go can cause the DD to loose efficiency, and I would heartily agree. To that, I'm adding the fact they don't do so hot in rolling hill country either. At my weight, the word gutless comes to mind.

I do agree the DD will shine at higher speeds, with a minimum amount of stop and go.

Can't help with regards to a lighter load. 8)

 

[MikeSSS]

I'm surprised that the two very different hubs came close in energy use, but the ride did not play to the strengths or weaknesses of either type of hub, so maybe it should not be a surprise.

The close results were for very low power riding. From recharge data, the geared hub used 90 Watts average power, the direct drive used 107 Watts average. For comparison, most of my riding uses 125 to 200 average Watts of electric power, again based on recharge data. Actual Watts at the motor are less because recharge includes battery energy lost to inefficiency between the battery and tire to road contact and also inefficiency in charging.

Leaving stops with the DD I use very little throttle and lots of pedal effort, always downshifting before the stop if possible. Yeah, the DD is slower off the line than even the tiny G311 geared hub if I want to accelerate faster, but leisure acceleration is how I ride, so I ride them the same. Similar thing for a friends geared hub, bought from Luna in 2016, his hub has more thrust off the line, if that is wanted. His geared hub and my direct drive have the same full throttle acceleration from about 10 mph up and the same top speed of 25 mph, this includes vigorous pedaling but sometimes no pedaling at all. We both use the same batteries, both purchased from Luna at the same time. Don't know about his battery energy use compared to mine though. His geared front hub wheel is lighter than my DD wheel. Hub diameters are similar.

Should have mentioned that the ride in the above post had very few stops, though it also had some slow downs for various reasons. If we stop or slow down before a climb, my wife on the G311 easily pulls away from me on my DD. I could keep up, but don't use enough throttle to do it. Her riding style is much different than mine, she uses less electric power in the first half of her ride and more in the second half. My riding is more constant pedal effort, shifting a lot to maintain a comfortable cadence as terrain changes. My throttle setting remains very constant.

When I ride her bike and my bike on the 8 % grade in front of our house, the two bikes feel very evenly matched at about 10 mph. This is using the same battery, sometimes 36v on both and other times 48v on both. This ride was tested a few times at about 8 to 10 mph, trying to maintain the same speed on both bikes on each run. Her 24" geared front wheel weighs about half the weight of my 26" DD front wheel. That's really impressive performance for the little G311 front hub. This is pretty low power climbing though. I've also done the same test on a short 14% grade, but at lower speed, with vigorous high cadence pedaling, both hubs perform much the same if the cadence and pedal effort are similar. Road speed is less on this steeper grade. Feeling both motors at the top tells me they are only a few degrees above ambient temperature. Again, this is a short climb.

So that's what is happening when using low electric assist power, for these two very different types of hub motors.

None our riding comes anywhere near melting a hub motor or even raising its temperature much.

Reasons for looking into this comparison are: A. It's more fun than waiting to get coronavirus. B. I'm wanting to change from a rigid bike to a full suspension bike and am trying to decide between a small, light rear hub motor or BBS02 or BBSHD mid drive. Unsprung weight is a factor in the choice and points toward a mid drive. High unsprung weight rules out a rear direct drive hub.

 

[MikeSSS]

Dogman Dan has nailed it: direct drive is good for rides with few stops and geared hubs are better for inner city riding that has lots of stops. That should have been obvious to me but, yet again, I didn't see it until he pointed it out.

 

[dogman dan]

Didn't mean that as an insult, and I was referring to Mikes test anyway. But anytime there are more than one variable in an experiment, its junk science. You DID get a result, and it did approximate others results. Not so bad as some junk science, but you may have had some other variables too.

When I did similar tests, I was moving the motor kits though the same bike, then the weights did not change. Other variables I kept same, temperature, wind speed and direction, tire pressure and the tire, the clothing I wore, and the exact route I rode. The route went 2.5 miles north, then east, then south, then back west. The route was slightly uphill on the east leg, then back down on the west leg, for a 10 mile ride. I was riding a set 20 mph on my tests, so speed was the same. I did NO pedaling on any of the test rides.

Went quite a bit out of my way to have one variable, the motor and controller kit. And I found that the efficiency of both types of motor were almost identical, within about 20 watt hours for the 10 mile ride. Actually I was quite amazed at the lack of difference.

The same comparison to aotema brushed motor was nowhere near the same, brushed wasted about 20%.

 

[AHicks]

Dogman,

Similarly, my test was done on the same bike. The ONLY difference in the before and after was the motor itself. Noteworthy, is that my test was much longer term. Nearly a year of riding. Same rider, same weight, same riding area (Florida Gulf Coast, so no extremes, other than maybe humidity), with conditions whatever they were, week in and week out.

Results above pretty much speak for themselves. -Al

 

[docw009]

The close results were for very low power riding. From recharge data, the geared hub used 90 Watts average power, the direct drive used 107 Watts average. For comparison, most of my riding uses 125 to 200 average Watts of electric power, again based on recharge data. Actual Watts at the motor are less because recharge includes battery energy lost to inefficiency between the battery and tire to road contact and also inefficiency in charging.

I've done my "economy" tests using a wattmeters both between battery and controller, and charger and battery. I grant there are efficiencies, but my measurements show the the power out and power in numbers match easily within 10%, maybe even 5%. Charge and discharge were within .2 AH for usage around 4-5AH, I start with a fully charged pack. Measure the AH used on a ride. Then I turn the meter around and see how much AH goes back in when charging. I am confident enough of the repeatability that I only check for charging now.

I have three of the Tenergy meters. They're all over the place when used to check voltage, but when placed in series they give consistent readings on the AH,

 

[MadRhino]

The real advantages of geared hubs are their freewheeling, smaller size and weight.

Efficiency should not really be a concern. Those who are riding geared hubs are generally economical in power usage, and adding crank work is within their usual riding speed. Very few are using geared hubs with performance in mind, and they usually don’t last for this purpose anyway.

DD hubs on the other hand, can be very inefficient because we can abuse them power and speed considerably. When you build with a DD hub, you need to decide wether the priority will be efficiency or performance.

 

[MikeSSS]

Docw009, that "economy" test is really interesting and informative. Can you post a link to the meter? The two Luna meters I had both had very short lives, but they were useful while they lasted.

The post was about some calculations done on a leisure ride my wife and I did. It was not an attempt at science, not at all. It was just some calculations from the ride, I like to calculate things, it's fun.

 

[MadRhino]

I like to calculate things, it's fun.

Sometimes I do, just for fun. My last ‘efficiency’ calculation was 149 w/h per km on a 10 km city ride.

 

[MikeSSS]

MadRhino, tell me about your bike or bikes, your riding, etc.

Thanks,

Mike

 

[MadRhino]

MadRhino, tell me about your bike or bikes, your riding, etc.

Thanks,

Mike

Well, the 2 that I ride the most.
Built on DH frames. The street bike is on a Trek Session 10, has a QS205H50v3, powered by 24s RC lipo, on 24’’X3.0 Street Hog slicks, mod suspension to 4’’ travel (front WC air, rear 11.5’’ Ti spring). The dirt bike is on a Santa Cruz V10, has a Clyte X5404, 24s RC lipo, on 26’’X2.8 DH tires, mod long travel suspension (front MonsterT, rear TI spring). Both have Magura Mt7 brakes. Top speed dirt 55mph, street 70mph.

 

[MikeSSS]

Used Google to search for info on those bikes, they are far beyond anything we see here in San Antonio. Tell me more about riding them, details please.

Best regards,

Mike S

 

[MadRhino]

Used Google to search for info on those bikes, they are far beyond anything we see here in San Antonio. Tell me more about riding them, details please.

Best regards,

Mike S

Well, I purchased my V10 in Texas.
Via Pinkbike. It was new old stock from a bike shop that was closing. It’s been there many years and never found a buyer. I’ve had it new with full ´crash guarantee ´ from Santa Cruz. It is a V10 MK1, an early DH racing frame almost indestructible, stiffer than many motorcycle frames.

Still my favorite dirt ebike, even after building many other. I crashed it a few dozen times in the mountain, most of them I picked up the bike and resumed the ride like nothing happened. I ride it hard and fast for the last 8 years, and also used as a winter commuter. The suspension mod was a long series of try and error, but I finally got it to behave despite the 33lbs motor. It is the second motor on this bike, replaced an identical that was not worth rebuilding anymore.

´nuff said
Hope you have a chance to ride a Santa Cruz V10 some day.

 

[dogman dan]

149 wh/ km sounds fun!

Bottom line on efficiency, riding slow and pedaling more results in amazing distances. The idea is to use 300w of motor, and 100w from legs.

I was able to ride a bike loaded to 450 pounds including me, at 25 wh/mile. Over rocky mountain passes, across huge desert gaps between towns, by riding 15 mph at all times. Up the mountain, 15 mph, took a lot of wh. But then down the other side a pure coast, no regen. On the flat, same 15 mph. It was crucial to have a cycleanalyst, and keep an eye on the wh/mi average for the ride. After about 60 miles, I could see that I could ride faster the last 20, and make it to plugs and water.

But this was with a very large DD motor. I did not need a geared motor, with 60 miles to the next stop sign.

 

[MikeSSS]

The Session 10 and V10 are both downhill bikes?
Both are equipped with very powerful direct drive rear hub motors, yes? These hub motors are more powerful than mid drives, are they not? Far less load on the driveline too, I'm guessing.
Both are using 24s Lipo batteries?

It looks like to get a lot of performance and reliability that a direct drive hub motor is the way to go.

These must be very fast and impressive bikes. Riding them would be a great experience.

I'm thinking of a rear hub motor on a full suspension bike, it won't be for fast riding, mostly to get a more comfortable ride, compared to a rigid bike. It might be used on the Moab Practice Loop and probably on the Slick Rock Loop, that would be a once in a lifetime ride. The alternative to a rear hub motor would be a BBSHD on a FS bike, but it might not fit on the FS bike I already have, because of the chainstay front pivot point. I'm too old to ride fast, and I pedal pretty hard when needed. Moab can be steep but I don't mind walking up next to the bike if needed, as long as throttle is available to move the bike upward a bit at a time. The bike becomes a "walker" of sorts on the climbs and on the descents if they are beyond my riding ability. A small, light rear geared hub motor might work well for this purpose. I would never be used in a long, steep continuous climb. I like to stop and look around a lot, the scenery at Moab is very interesting as is watching other riders and their bikes.

What do you think of this plan? What do you recommend?

Thanks

 

[donn]

I don't remember ever thinking of taking a bicycle off road for any distance, but since I don't see anyone rushing to comment ...

The impression I get is that while practically everyone here is dedicated to being the exception to the rule in one way or another, if you were looking at what usually works the best for different situations, the off-road setup is going to be a crank ("mid") drive. I guess because the grades are far more extreme than usual road riding, you're usually fine with a slow ascent, and you aren't going to enjoy an extra 40 to 60 lbs of motor and battery.

 

[MadRhino]

The Session 10 and V10 are both downhill bikes?
Both are equipped with very powerful direct drive rear hub motors, yes? These hub motors are more powerful than mid drives, are they not? Far less load on the driveline too, I'm guessing.
Both are using 24s Lipo batteries?

It looks like to get a lot of performance and reliability that a direct drive hub motor is the way to go.

These must be very fast and impressive bikes. Riding them would be a great experience.

Yes to all previous. :wink:
I like to call them fast ebikes ULM (Ultra Lightweight Motorcycles).

I'm thinking of a rear hub motor on a full suspension bike, it won't be for fast riding, mostly to get a more comfortable ride, compared to a rigid bike. It might be used on the Moab Practice Loop and probably on the Slick Rock Loop, that would be a once in a lifetime ride...

Well, I always tell slow trail riders to go for mid drive. BB drive would do good of course. You could even use a hub and mount it as a mid motor, gearing it down for slow riding. Hub wheels are not the best choice for slow climbing. They are efficient climbing fast. Of course, big hubs can stand a fair amount of inefficient riding because of their weight that makes them good at shedding the heat. Yet, it is not the ideal build for such purpose.

What is so good in building your own, is that you can build it ideal for the purpose, and your riding style.

 

[MadRhino]

I don't remember ever thinking of taking a bicycle off road for any distance, but since I don't see anyone rushing to comment ...

The impression I get is that while practically everyone here is dedicated to being the exception to the rule in one way or another, if you were looking at what usually works the best for different situations, the off-road setup is going to be a crank ("mid") drive. I guess because the grades are far more extreme than usual road riding, you're usually fine with a slow ascent, and you aren't going to enjoy an extra 40 to 60 lbs of motor and battery.

Agreed. Hub build dirt ebikes are meant to ride fast, an Mike doesn’t seem to be up to do so. MOAB is a place I would probably build a powerful mid drive myself, and do Trial instead of cross riding. No a BB drive for me though, not enough power for my riding style.

 

[dogman dan]

I got perky yesterday, and went out with my 52v 22 amps geared hub bike, and rode the upper loop of the local national park trails for the first time in ten years. I used to ride this pedaling before I got west nile, because it would kill my lower power DD hubs to ride it.

Granted,, it was not a hot summer day,, but the hub had no problem with it. Still had to get off and walk up the really steep smooth rock sections, and the worst uphill rock staircases. But it did it, at my old fart pace, without any problems with overheating.

But still,, you keep talking moab Mikesss and what you need to do is buy a mid drive, or rent one once there. You can still take what you have on the trip, just budget for one day of rental to go do the harder loop.

And stop by Las Cruces on the way, and ride a day on my national monument, as a warm up. Its right on the 10. Free place to stay in my RV.