RECUMBENT WITH MID DRIVE ??

[Kunk222]

E-Bent -- Project

I'm a retired Mechanical Engineer living near Portland, OR. My current favorite ride is a beautiful Rans Stratus LE recumbent which I would like to convert to electric assist. Here are my design goals:


Basic information

- Location: Beaverton, Oregon, with an excellent bike culture and network of bike paths, trails and lanes.
- The area is somewhat hilly with 5 to 20% grades.
- Rider: 5' 11", 220#, with two blown knees (old football and skiing injuries). So,the beautiful hills around here are a definite problem, especially on a recumbent.
- Experienced motorcycle, bike and recumbent rider.
- Eexcellent mechanical and electrical skills and a shop full of equipment. Building up just about any kit or even doing a custom design and build for my Rans would not be a problem.
- My basic desire is to determine the best (for my needs) combination of drive type, battery and controller for my needs and bike.


Design goals - Needs

- Need to easily handle the local hills (up to 20% grades) with moderate pedaling.
- Range of 30-40 mi with light pedaling.
- Speed of 20 to 30 mph with light to moderate pedaling.
- Safe Lithium battery technology i.e. LMO, LFP, NMC
- High quality BLDC motor and FET ESC (controller)
- Must be cost effective (under $2K, system total)
- Must be reliable.


Design goals - Wants

- Relatively light combined drive and battery weight. The bike and rider are already too heavy.
- Forward, frame mounted battery (and drive ?) for better weight distribution.
- Estimate 750 to 1KW needed (OR max is 1KW and 20 MPH)
- BLDC, hub motor or mid drive ( Bafang or ?)
- High efficiency drive with low parasitic losses (heat, cogging, drive train drag)
- Rugged, 30-40 A ESC with 9-12 FET topography (why don't mfgs use IGBTs ?)
- Cycle Analyst V2.5 or/= would be nice
- Very clean and water resistant installation...It's Oregon. It rains...a lot.


Summary:

My intended use is a daily, local area ride on bike paths, roads and hard packed bike trails. Typical grades in this area are 10% up to 25% with a distance of 1/8 to 1/2 mile. As I said, my knees are shot so that I really need help on the hills rather than speed. Quality is also important. I have absolutely no use for low quality and unreliable equipment.

Would a Bafang 750W, 48V BBS02/= make sense for a bike like my Rans Stratus LWB Recumbent? It seems like it would be efficient with great hill climbing ability. With both the drive system and battery mounted forward the weight bias would be closer to balanced.

Another choice might be a different mid-drive or rear wheel geared hub drive. I do worry about the reliability of most geared hub motors. At the same time, the higher torque and light weight of a geared hub or mid-drive is desirable.

I'm looking for ideas and suggestions for the best combination of components for my needs. I can build just about anything. What I need is good information from the experts (Kepler et. al.) to get off to a good start on this project. I also plan to video my adventures in building and riding the bike.

Thank you all, in advance, for your help...kunk

 

[Kunk222]

absolutely no replies...what's up?...thanks to all

 

[spinningmagnets]

Some guys only check in once a week. I think the BBS02 is probably your best bet. It's light, and the ability to change the gears that the motor is using is the defining feature of a mid drive, so hilly commutes are its main target customer. em3ev.com is now carrying them, and he is a trusted vendor.

The GNG or LightningRods kit would be overkill...it is a hot rod instead of an economy car. On flat land, I personally believe that a hub can be close to a mid-drive in efficiency, but for hills?..it's no competition.

As far as the battery, the BBS02 doesn't draw big amps because your gear-shifting will keep the motor in the higher RPM's instead of bogging it down. This is also good news because you are not required to use high-current batteries, so you have a lot of options. if you want a lot of miles in a small and light package, cell_man (Paul) at em3ev.com sells several different sizes of pack (triangle or common rectangle) that have the option of using the Panasonic 18650PD cell, with 2900-mAh per cell. It costs extra for that, but for max miles in a small and light package, it's the current "go to" cell and chemistry.

 

[Kunk222]

Thank you Spinning mags,

Great info, and pretty much what i was thinking too. I was a bit worried about motor mounting position and ground clearance. But, when I looked closer, it looked like there would be plenty of room for the motor and battery pack just behind the front wheel (approx 10" for the 20" wheel.)

I still have a few questions about the Bafang BBS02. How should it be set up for my application? I would like to have access to the full 750 watts either with pas or std throttle. What is the topography of the Bafang BBS02 ESC and how can it be accessed with SW and interfaced with a CA and/or separate controller.

I also have a few concerns about the drive system, overall, with regard to reliability. I'm not looking for max power or speed just good hill climbing ability with maximum reliability.

Thanks again for your reply...kunk

 

[JEB]

Hi Kunk; I have been playing around building electric bikes/trikes for years, I powered a Marten Tour Easy long bike similar to your Rands, I found that I needed about 750watts using a split chain system like the Eccospeed, but buying parts and assembling it myself. (A lot cheaper) (That whole assembly is now on one of my trikes) I had the batteries forward of front of the seat but lower, the feel of the bike changed too much for me, so I located them near the rear wheel axle as low as I could get them one on ether side.

I had rear tire wear problems, (27" wheel tire assembly) ( I was approaching 220lbs at the time) so a overkill design change to a 5hp brush less motor with a 16" trailer tire dot rated at 750lbs, still using the 40ah li cells (30lbs~24volts 8 single cells), but braking using the front wheel would not do, added a 1995 rear Ninga rear disk motorcycle hydraulic unit. It floats down the road now, stopping using the hand brake lever cable to hydraulic cylinder assembly, stopping with one finger on the lever is all that is necessary .

I have a couple of hub motors, (never used them) I like the idea of being able to select the rpm to speed ratio that a chain/gearbox/motor can provide, going to the rear cluster gives you a large selection of speeds, and the best hill climbing options with a 750~ watt motor.

But for you a Eccospeed if you can afford it, would be the easy way to go. Or with your skills a home brew, using a Matt S. drive assembly (mid drive), lots of power lite weight. You can use a 2000 watt motor, (Astro) or more driving on the left side of the rear wheel. (my 2 cents worth)

 

[MitchJi]

Hi,

Not exactly what you want to do, but the quality is excellent (Matt sells components):
http://www.wisil.recumbents.com/wisil/shumaker/default.htm

This project began as a simple exercise in efficient transportation and has evolved into a "Hot-Rod" E-Bike

I have always wondered why so few recumbents are converted to E-bikes. There are many trikes that have been converted, but precious few recumbent bicycles. This seems strange to me considering the efficient layout of recumbents versus upright bikes. So, to that end, I decided to convert a recumbent...

Discussed here:
http://endless-sphere.com/forums/viewtopic.php?f=6&t=3904#p57685

 

[chvidgov.bc.ca]

I don't think there is anything wrong with either a rear hub motor or a front hub motor on the 20" wheel if it is a fast wind. I run a Crystalyte 405 front on one of my Sun EZSports, with fairing, and it is nice balance with dual packs right under the seat on a mid rack. A rear hubbie like a 9Continent 2806 or 2807 would also be very easy to install, although you would sacrifice your nice cluster, for a cheap freewheel. Hubbies are pretty trouble free, and if anything are even better on recumbents than on regular bikes due to the ease of carrying batteries in the middle which gives you nice balance with either a front or rear. With a fairing and a decent hubbie, you won't have any trouble getting into the thirty mph plus zone, with a quiet reliable solution. Low risk compared to the mid drive, in my thinking and very satisfactory. I carry two Headway packs 48V 15Ahr low under my saddle, so I've got a lot of comfort and range, on a long wheelbase recumbent like yours. And nice and quiet, with battery redundancy.

 

[Warren]

kunk22,

I think the Bafang 750 would be fine at your weight.

http://em3ev.com/store/index.php?route= ... uct_id=166

With the extra weight, and little pedaling, in big hills, I would suggest a one kWh pack for a reliable 40 mile range, and not hammering the pack with a high C rate.

http://em3ev.com/store/index.php?route= ... uct_id=166

You may also want a tandem type rear wheel...Aerospoke carbon, or 48 spoke typically.

Warren

http://www.evalbum.com/4525

 

[Warren]

Interesting. Since I posted yesterday, the A123 packs are gone off cell_man's site. Only Samsung packs now.

 

[Kunk222]

Thanks to all who answered my post. Your comments are appreciated.

Lets put this one to bed for now...kunk

 

[Ninosmits]

Hello Kunk,

This is my project.
A Flevobike (type Basic) from year 1996

Now my maximum is 50 km/hour, very stable.
The added motorunit is a Bafang BBS01B with brake-sensor.
Look at the picturs.

Kindly regards,
Nino Smits

 

[--freeride--]

The 750W Bafang is the way to go.
You can programm the controller, as you like. You are free to choose the amount of power the motor delivers on each assist level. The throttle is normally set up as overdrive. So you can always go full throttle if u like on top of the assist.

I use low assist levels and ride arround with a little back wind. For grades i use the Throttle on top.
Choose your gearing that u reach your aimed topspeed in highes gear. than u will be fine on grades in the low gears.

The Bafang gives good power up to 110rpm at the crank. So 30mph at 110rpm should be your highest gearing.
On a recumbent like yours i would put 2 sprockets in the front.
The motor makes 120NM torque at the crank. So you better make a torque arm that it can not swing up.


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[gman1971]

Very nice. Here is mine. (its a trike tho, but recumbent...)

50mph top speed (right now) 70 mile range.

75-25 weight distribution so its a go-kart on a trike frame.

VIDEO RUNNING:
https://www.youtube.com/watch?v=lArVKGgkwTo

VIDEO OVERVIEW:
https://www.youtube.com/watch?v=oFC8MRwvgUM&nohtml5=False

G.

 

[johninsd]

I've built two LWB recumbents with front hub motors, one for me and one for my GF. One has an Ezee motor from Grin and the other an 8Fun bought from bmsbattery in China. Both have been quite reliable after several thousand miles (7000 on mine according to the Cycle Analyst, fewer on hers but as it has no CA I don't know how many). The only failure to date is that a 36V bottle battery from bmsbattery will no longer take a charge - it's about 4 years old. The 5 year old Ezee battery is still going strong.

While I've been happy with the Ezee motor I've been looking into putting a Bafang BBS02 on my recumbent (an Easyracers Fold Rush) to make climbing more efficient. I'm tentatively planning to ride coast to coast next summer (2017) and getting over the Rockies I think would be iffy with the hub motor. The Ozarks are worse than the Rockies too, not as high but typically much steeper.

We use our motors as assist motors to help us get up the hills around here (San Diego), not as go fast motors (we have actual motorcycles for that) so I'm looking at the 36V version of the BBS02. It looks like Tyro EV in Las Vegas might be the place to buy it (they sell on Amazon, which I like to use because of their return policies etc., also I get a 5% kickback on the Amazon store card). Lunacyle no longer shows the 36V BBS02s, just the 48V ones.

BTW I'm also a retired ME, have a lathe and mill in the garage and know how to use them as I was an apprentice tool and die maker a long time ago so making whatever little parts I need to get this together won't be a problem.