Looking to build a portable friction drive for bikeshares

[newtim444]

Hello all,

I'm new to this forum, so I apologize in advance for my ignorance and thank any and all who may be able to assist.

I'm looking to build a portable front mounted friction drive for the "bixi" bikeshare system (see bixi.com). A commercial system does exist (http://www.shareroller.com)and I'd be interested in purchasing a shareroller actually, but the costs seem way too high (starting at $1250 US). Front mount is necessary due to the fender on the rear wheel.

I already have a Turnigy 6374 192 motor (http://www.hobbyking.com/hobbyking/...SK3_6374_192kv_Brushless_Outrunner_Motor.html )and I'm asking for some assistance to figure out the rest. I'm familiar with the types of components (ESC, Lipos, etc), but I'm not really sure what kind of specs I need. My commute is pretty short (5km one way), but it's got a decent hill on the way back and the bikes weigh 50 pounds so it's nice a nice ride up hill. I weigh 180lb so I need to push about 230 pounds. Ideally if I had 15 to 20 km of range, that would be great. Top speed is not a huge issue but somewhere around 25 - 30 km (or more) seems reasonable.

My questions are more component related. Can anyone recommend a good, cost effective battery and ESC combination for this? Also, I gather I need to do something with a servo controller to make a throttle. Can anyone expand here? Will my ESC keep the lipo's safe from over discharging?

I'm more confident with the mounting bracket and containment aspect of it all, it's the electronics that I'm fuzzy on. I'd be happy to share my journey here.

Thanks for taking the time to read this.

 

[amberwolf]

Have you looked at the rear ones by Kepler, Adrian SM, EVTodd, and others?

 

[newtim444]

I've looked through a lot of those I believe. Some of the posts are dated, so in terms of the current offerings I'm wondering if anyone is able to suggest a battery pack/esc combination to go with the motor I provided. This aspect is a little confusing to me. How many amps should the esc be? Do I need to be able to change the settings (some appear to be less configurable), and again, I'm interested in throttle work arounds, especially ideas on how to make the throttle portable.

Thanks for your suggestions, I'll check out those people again to make sure I haven't missed something.

 

[spinningmagnets]

If you are trying to save a few bucks and want to source something that is currently copyable (meaning it only uses new products available now) get the Hobbywing 100A-HV. http://www.hobbywing.com/product_show.asp?id=331

If you will only build one unit and you are willing to pay more to get something that is guaranteed to be the best possible, get the Castle Creations Edge HV-120A. It has data logging and excellent performance.

Will you be using the motor-shell as the roller (like Kepler and Adrian) or a separate roller (like me and EVTodd). This is an important decision. If you live on flat terrain, 22V and the can of the 63mm diameter outrunner will work fine (use the HV-120A ESC). 50mm diameter doesn't have enough copper mass.

If you have hilly terrain, I highly recommend a one-inch diameter roller using 37V, but the good news is that the smaller roller will lower the amp-draw, so the 100A-HV will be fine. Follow the friction drive link in my sig

 

[shareroller]

Hi everyone,

This is Jeff Guida, the founder of ShareRoller. This post was forwarded to me so I figured I'd drop a quick note.

Newtim444, glad to hear you're interested in a friction drive solution for your Bixi commute. These things are brutal for hill climbs, aren't they? The ShareRoller would be perfect for you, but I completely understand your reluctance to the price. (read on for good news on that front !)

When we set out designing this product, we hoped we could offer it for half the price we're at today. But unfortunately, our costs to manufacture ended up being significantly higher than we'd planned, not only due to the high-quality motors, batteries, and electronics we chose to use for maximum performance and minimum size/weight, but also due to the complexity of the retractable motor assembly and case system that we designed for optimum convenience and versatility. 

So while it took us a lot more engineering time than we planned, and ended up costing double what we expected, we now have a product that performs better than any friction drive system before, and has unmatched flexibility and versatility. It installs or removes from a PBSC bike share bicycle in seconds, the performance is rock-solid (even in the wet), and the lightweight compact package enabled by the retractable motor assembly makes it ideal to carry it anywhere or tuck it into a briefcase (5.5lbs and the size of a lunchbox). Not only that, but the mounting system also allows it to work beautifully on many personal bikes and kick scooters in exactly the same fashion (if you haven't contemplated a 20mph+, 15lb e-scooter for your short commute, you really should). We even have customers that use the ShareRoller on scooters and share bikes in the same commute! (scoot to/from distant share bike docks). So the multi-platform flexibility is really a game changer, and it's not even something we'd first planned when the project began!

Don't get me wrong, it wasn't that hard to cobble together something that 'worked' on a NYC CitiBike (share bike) for less money. We had early prototypes that 'functioned' with only a few hundred dollars of cost, but they certainly did not function well. The motors would slip on the tire even in the dry given the spring loaded mounting point. In the rain they were utterly useless. Long hills would cause overheating, the throttle response was tricky to control, and the whole thing was a jumble of wires, batteries, and motors that was a royal pain to install and remove every time you wanted to undock or dock a share bike. Oh, and consumer LiPo batteries can even burst into flames when things go wrong. Not exactly something we felt people would want to carry into offices or store/charge inside urban apartments!

We've solved all those problems and more over the last 2 years of engineering development. So it'd be a shame to not take advantage of all that hard work for your bike share commute. And as I mentioned up front, I've got some good news for you on the price front. We're going to be shortly launching a V3 version of the product via crowdfunding on the Indiegogo platform that will feature significantly lower pricing. As in, meaningfully below $1k. We're moving to legitimate volume production that will finally allow us to get our costs to where they need to be. We realize the product needs to be cheaper, and we're pulling out all the stops to make that happen. Not only that, but the V3 will have _much_ more mounting flexibility than the V2, and will include a 'Mini' version that is only 4.5lbs and 20% smaller than our current Base Range model.

My apologies for the long post - I didn't set out intending to write so much! And please forgive me if it sounds like I'm just trying to 'sell' my product. I only wanted to convey all the challenges of using a portable, detachable friction drive system on a share bike so that you wouldn't have to go through all the trials and tribulations that we have in order to get something that worked the way it should, something that will make your bike share commute truly pleasurable.

Happy to answer any and all questions! 

-Jeff

 

[EVTodd]

we now have a product that performs better than any friction drive system before

Please...