Why aren't any rear hub motors equipped with freehubs?

[redorblack]

I asked the owner of the company I got my front hub motor from if he could get his supplier to make him a hub motor that took a standard Shimano freehub. I'm perplexed why no one is doing that already. It seems like rear hub motors are still 30 years out of touch with this... a freehub with cassette is a much stronger setup than a thread on freewheel hub. The bearings are further outboard on the freehub vs the freewheel and you could then use any modern cassette/indexed shifters you wanted.

Is it because you need to pull the axle to work on them? Maybe it's just easier for manufacturers to machine a thread onto their hub motor body therefore they don't want to bother with adapting to modern components?

Even if they were forced to make a slightly smaller form factor motor like a bafang only a bit skinnier, I think it would still be an advantage. I know I want to be able to run my shimano cassettes (9 speed) on the back of my trikes. I can't run a front hub motor since my front wheels are single side mounted axles and have integrated drum brakes.

Is everyone just copying everyone else and that's the problem?

 

[liveforphysics]

It enables the hubmotor to be single speed or geared.

The same motor fits a Mt Bike, a road bike, a BMX, a cruiser, a chopper, etc. This lets a user change bike styles and just lace the motor into different rims rather than needing to buy a new motor.

It's not the strongest way, but it's only transmitting human pedal power through it, so it's not like you see them being a big reliability problem if a quality freewheel is used. Also, if you demand the strongest possible freewheel (1spd), the white industries ENO trials 6paw, it's only going to mount onto threads.

 

[dogman dan]

I think the really highest quality of bike stuff is not needed so much on ebikes.

Half the riders don't pedal at all, or only faux pedal. So gearing don't matter a bit. The market has to see a need before it will fill it. Also the ebike market, unlike the bicycle market , is really full of cheap bastards like me who won't pay top dollar for anything. Anything nice I have was bought used.

 

[spinningmagnets]

Whether a particular design is good or poor, manufacturers are very sensitive to shifts in buying trends. There is still a huge percent of the population that has never even heard of an electric bike. And most newbies who start looking are very sensitive about the purchase price.

There was a post recently with an aticle saying that last year Chinese people bought millions of E-bikes. And thats just last year, at that point there were already millions of Chinese E-bikes on the road. Threaded freewheels are mass-produced very cheaply, and most buyers wouldn't pay $10 extra for a freehub model, so why would a manufacturer be willing to install the tooling to start producing them?

I'll point out another clear upgrade. Tidalforce doesn't route the motor wires out a hollow axle (limiting the size of wire). They use a solid axle, then a bushing with a slot thats shaped like a "C". Outside the bushing is a common bearing, but the bearing must be about 4 times the diameter of the common (millions made a year) bike axle bearing. The sideplate is cast to whatever bearing thats specified, so the extra cost is only the C-bushing and the larger bearing. When bought by the truckload, the cost per wheel might be an extra dollar?

How about splined freewheels? Any company that makes splines in bike wheel accessories ALREADY has a broach-press, yet liveforphysics has to make them in his shop because White-Industies (ENO) isn't interested unless you want to contract for hundreds of them. (That, plus they want YOU to pay thousands upfront for the freewheel-specific spline-cut tool)

http://sheldonbrown.com/freewheels.html

 

[BVH]

The E+ 750 and 1000 Watt motors use cassettes, not thread-on freewheels. The cassette slides over the Shimano splines bolted to the motor. I just made my own custom 7-speed setup from cannibalizing individual sprockets/cogs from three Shimano HG70 cassettes. I was able to end up with an 11-32 and just for fun, I installed a Shimano XTR, medium cage derailleur. The cassette was originally an 11-28. I need that 32T low gear to get the 80 lb bike up the numerous 12 to 15% hills in my City. But 90% of the time, I'm carrying the majority of the energy load to move the bike, not the motor. The single front chainring is a 44.

 

[redorblack]

The E+ 750 and 1000 Watt motors use cassettes, not thread-on freewheels. The cassette slides over the Shimano splines bolted to the motor. I just made my own custom 7-speed setup from cannibalizing individual sprockets/cogs from three Shimano HG70 cassettes. I was able to end up with an 11-32 and just for fun, I installed a Shimano XTR, medium cage derailleur. The cassette was originally an 11-28. I need that 32T low gear to get the 80 lb bike up the numerous 12 to 15% hills in my City. But 90% of the time, I'm carrying the majority of the energy load to move the bike, not the motor. The single front chainring is a 44.

Do you have a link? I'm interested in going this route with one of my trikes without losing my 9 speed shifting. I'll already be losing the Sram Dual drive doing it.

 

[SpeedEBikes]

Several years ago I bought a couple Crystalyte hubmotors from Kenny that mount freehubs. I think they were experimental and never made it into the retail channel.

I was very stoked on the concept, but unfortunately they didn't work out too well for me. The axle is much smaller to accomodate the freehub body bolt and is threaded all the way to the hub. This really complicates getting a positive attachment to the dropouts that can take the torque of the motor without twisting. Twisting is very bad. Not only can it chew up or deform dropouts, especially aluminum ones that are hard to replace, It is also pain to reattach the sheared off phase wires and especially the hall sensor wires. I had to do this repeatedly until I got the mounting just right.

I have a nice tig welder and some limited machining capability and eventually made a set of locking nuts with a fat key that sort of worked, but it was much more difficult than what I usually go through to mount a motor.

My original desire to mount freehubs was just to be able to use the stock cassettes and gear shifts that come on most new bikes of decent quality. Perhaps on a very minimally powered ebike there would be a need for the full gearing and axle twist would be less of an issue.

I've found in my own ebiking with setups ranging from 500 to 2000 watts that I use the gearing much less. I often leave ebikes in the top gear and not shift at all. So for now I've forgotten all about the freehub motors and just stick with freewheels. Also, It's now fairly easy to get 8 and even 9 speed freewheels so one could still accomodate their stock indexed shifter without a freehub if one felt it important.

In my most recent build though, I went the other way. Instead of using the Shimano Mega-7 freewheels I typically use, I went with a narrower 5 speed freewheel. You need a motor with an axle set up for this or need to be able to modify the axle for it. The big win is that this hugely reduces the amount of dishing needed which makes for a much stronger wheel. I did this for an extended length cargo bike that will take 400 lbs on the rear racks. It worked out so nice I'll likely be building more wheels like it in the future.

 

[BVH]

The E+ 750 and 1000 Watt motors use cassettes, not thread-on freewheels. The cassette slides over the Shimano splines bolted to the motor. I just made my own custom 7-speed setup from cannibalizing individual sprockets/cogs from three Shimano HG70 cassettes. I was able to end up with an 11-32 and just for fun, I installed a Shimano XTR, medium cage derailleur. The cassette was originally an 11-28. I need that 32T low gear to get the 80 lb bike up the numerous 12 to 15% hills in my City. But 90% of the time, I'm carrying the majority of the energy load to move the bike, not the motor. The single front chainring is a 44.

Do you have a link? I'm interested in going this route with one of my trikes without losing my 9 speed shifting. I'll already be losing the Sram Dual drive doing it.

They don't sell just the motor that I'm aware of. Although, if it was bought as a "replacement", maybe you could somehow get one. Although, I don't know how you'd interface the motor with available controllers. Their controller is located in the front hub battery enclosure. The torque arm will take up the normal disk caliper mounting holes. The phase wires are 10 awg all the way into the internal motor connections.

You can buy their complete kit which, I think is $2,200 or more, not sure. Look on their site: http://www.epluselectricbike.com

 

[amberwolf]

I'll already be losing the Sram Dual drive doing it.

Not necessarily, if you are willing to alter your drivetrain a bit and have the room. The SRAM DD can be hung from a set of dropouts in the path of the chainline, and you can bolt a sprocket to the left side of it via the disc brake holes, for output from the hub, and input would be via the sprocket you choose to install on the right side.

Then you will need to route the chain's power back to the right side again, which can be done via a jackshaft immediately behind the SRAM DD hub. The jackshaft can be made using a dual-disk-brake capable front hub, like Choppers US sells, I think. Just bolt the same size sprocket to each side of it where the disk brake holes are, and you're all set.

If you make the dropouts that hold the two hubs so that the slots for them are oriented diagonally, you could then adjust chain tension on each by moving them in the dropouts, just like a fixie.

This is essentially how I would prefer to drive my rear wheel, but I don't have an internally geared hub (and I'm not sure there are any that would stand up to the power this motor I have can put out, with the weight of the bike as it is now).

 

[justin_le]

I asked the owner of the company I got my front hub motor from if he could get his supplier to make him a hub motor that took a standard Shimano freehub. I'm perplexed why no one is doing that already. It seems like rear hub motors are still 30 years out of touch with this... a freehub with cassette is a much stronger setup than a thread on freewheel hub. The bearings are further outboard on the freehub vs the freewheel

This is true with respect to regular bicycle hubs that have 10mm threaded axles. But it's a bogus argument with hub motors, which have anywhere from 17mm to 25mm diameter axle shafts. So the main case that is made for going to the freehub design over a screw-on freewheel totally doesn't apply with hub motors. In fact, the design of the cassette freehub forces the axle on the right hand side to be quite a bit skinnier, if anything making a weaker axle arrangement than it was with the freewheel.

and you could then use any modern cassette/indexed shifters you wanted.

This is on the other hand really is a valid point. All the higher-end gear is for cassette freehubs, so if you are fitting a hub motor design for North America then it should be compatible with that standard even if there isn't any compelling engineering case to be made.

As others have pointed out, it can be done and some hub motors have been fitted with freehubs, the Tidalforce/E+ quite well, while with Crystalyte a little less successfully. Crystalyte's approach was a total failure because they didn't include the outer set of cup/cone bearings to support the end of the freehub. So the entire freehub body was cantilvered out and supported only from the side cover attachment. They'd usually break after a couple hours of pedaling.

The downside about adopting the freehub is that the right half of the axle has to be made round and 10mm dia, which means it can't be used as either a channel for cables or as a means of transmitting stator torque. So now all the torque retention as well as the wire exit has to happen on the left side of the axle.

Is it because you need to pull the axle to work on them? Maybe it's just easier for manufacturers to machine a thread onto their hub motor body therefore they don't want to bother with adapting to modern components?

There is that too. The volume of hub motors sold to customers who would appreciate the value of a freehub over a threaded freewheel is almost infinitesimal compared to the volume of motors sold in asia where freehubs don't exist. Nine Continent makes 40,000 hub motors a month. How many go to North America or Europe? It doesn't even register on their charts, so asking for favors and customizations is a bit of a tall order.

As more manufacturers start to recognize the potential for ebikes in the western world, then I think we'll finally see more engineering and tooling effort for conforming to these requirements.

In the meantime, you can get 8 and 9 speed screw on freewheels that are more or less compatible with the indexed shifters, they're not great quality but they work.

Justin

 

[WonderProfessor]

Half the riders don't pedal at all ...

But the other half of us do! I typically pedal all the time while I am riding. I almost never just exclusively use the motor without pedaling.

I still get some ribbing from some of the folks at the local electric vehicle association for dishing out the big bucks to buy the eZee hub motor with the freewheel. One guy just loves to brag about how his electric motor costs $35. But I am very glad I did get the eZee because I am able to still get quite a bit of exercise while commuting. If you are never going to pedal, why bother with an e-bike? Honda and Yamaha and Suzuki make incredibly reliable motorcycles.

 

[gogo]

If you are never going to pedal, why bother with an e-bike? Honda and Yamaha and Suzuki make incredibly reliable motorcycles.

You can't ride a motorcycle on the sidewalk or a bikepath, and you have to have a license, register, and insure motorcycles. I prefer to show up at my destination without pit stains. Oh, and most of all, I'm preserving the hair on my knees.

 

[WonderProfessor]

... Oh, and most of all, I'm preserving the hair on my knees.

???

 

[redorblack]

LOL Gogo...

Thanks everyone for the input, think I'll save up for the trike to go with my original intent of a mid or crank drive so I can keep my 81 speeds (triple crank, and a Sram dual drive 3x9). I have a feeling the Dualdrive won't last long though driving through the chain.