Motor for a LWB recumbent

[fitek]

Hi all,

Four or Five years ago I built a LWB recumbent for a college project planning to put an electric motor on it. I ran out of time but have now picked the project back up and am very happy to have found these forums.

I have been studying EV stuff for a couple months now and have decided on using a ~1hp BLDC motor with lithium ion cells.

There are a lot of motors out there though and I'm having trouble finding info on the differences - I looked at whats on sale at evdeals and ebikes.ca and they talk about 405, 406, 407, 5304, 5305 motors-- what is the difference between these?

The bike is a LWB recumbent and I was planning originally on mounting a motor on the front wheel (its the 18" rear wheel from a kids bike) using a chain but now I'm not sure if that would be the best choice.

Thanks in advance!

 

[Ypedal]

Good Day ! and Welcome to the addiction that is Endless-sphere !

the 40 in 405 for example refers to the magnet width ( 40mm )and the 5 relates to the number of turns in the copper windings.

the lower nubers ie: 405 are faster RPM motors than for example 4011. the 4011 would be slower, but more efficient at slower speeds.

So what you do is figure out the wheel size you need.. figure out what voltage/battery pack you can afford to use.. :lol: then use the motor with the proper RPM to match the speed you want to travel.

SMaller wheels provide better torque than larger wheels.. and make life easier on your batteries.. IMO.

36v is the minimum a brushless gearless hub motor will work at, 48v is much better.. some of us like to push thing a bit at 72v + !

 

[safe]

There are two types of people on this forum. There are those that use hub motors and there are those that use chains along with some type of gearing. The "bottom line" is that for the same power output from a given motor the geared bike can span a range of roughly double it's fixed gear counterpart. So the "high low" of hill climb verses top speed means you get twice as much out of the same motor with gears. On the flip side, you can use a hub motor and then simply double the voltage (and power) and get more or less the same result. Both are illegal in most places (depending on your local laws for motor power and acceptable top speed) so it's up to you how you want to break the law if that's what you had in mind. (mine does 40 mph on the flat with a 1000 watt motor)

I like gears myself... it allows me to use a smaller motor and when it comes to a hill I simply slow down and gear down rather than go for the "Big Iron" hub motor and high voltage to force my way though. The police seem to like the idea of a small motor being used with gears. (at least they seemed to like it when I showed it to them)

 

[xyster]

There are two types of people on this forum. There are those that use hub motors and there are those that use chains along with some type of gearing. The "bottom line" is that for the same power output from a given motor the geared bike can span a range of roughly double it's fixed gear counterpart. So the "high low" of hill climb verses top speed means you get twice as much out of the same motor with gears. On the flip side, you can use a hub motor and then simply double the voltage (and power) and get more or less the same result. Both are illegal in most places (depending on your local laws for motor power and acceptable top speed) so it's up to you how you want to break the law if that's what you had in mind. (mine does 40 mph on the flat with a 1000 watt motor)

I like gears myself... it allows me to use a smaller motor and when it comes to a hill I simply slow down and gear down rather than go for the "Big Iron" hub motor and high voltage to force my way though. The police seem to like the idea of a small motor being used with gears. (at least they seemed to like it when I showed it to them)

That's the most balanced, insightful statement regarding hubmotors and geared motors I've ever read from you, Safe! I'm deeply impressed. Right before our eyes, you're growing up to be such a fine young man

 

[Rassy]

Hi fitek. Sounds like a fun project. Do you have pictures posted? My brother (the non ebike puriest) pulls a one wheel "Bob" trailer behind his SWB Burley recumbent on multi-day multi-hundred mile tours, so I know you could pull a heavy trailer with a recumbent. If I was younger and wanted a narrow ride, (instead of my trike), I would start with a LWB recumbent with 20" wheels, add a "Bob" trailer with a 20" wheel, put hub motors in all three wheels, and carry the batteries on the trailer. At 36V this would probably go up most SF hills with moderate pedaling, and at 48V with no pedaling. It could be very stealthy, and the trailer could still have room to pack stuff.

P.S. I was born in SF in 1940, but have been a "native" oregonian since 1941.

 

[fitek]

Thanks very much Ypedal for this info. I just noticed that ebikes.ca has a description on their price list page. Oops.

With an 18" or 20" front wheel and a 26" rear wheel I get:
C=2*pi*r

C(18)=56.52 in.=4.71 ft
C(20)=62.8in=5.233 ft
C(26)=81.64 in.=6.803 ft

For each revolution, the wheel travels a length equal to the circumference.

With a desired top speed of 25mph, the number of revolutions needed to travel 25 miles is:

25 miles = 132,000 ft

18": 28025.48 revolutions per hour
20": 25222.93 revolutions per hour
26": 19403.20 revolutions per hour

Which becomes (divide by 60 minutes in an hour):

18": 467.09 rpm
20": 420.38 rpm
26": 323.39 rpm


Now that I did that calculation I realize I can't find an 18" wheel anyway. I think the bike would take 20" though without much trouble.

The cost of the hub motors ($300-$400 on ebikes.ca) makes the Chinese made Goldenmotor hub motor attractive. It's hard to beat $150 it seems.

I have tried to find cheap BLDC motors on surpluscenter's site, but I'm not having much luck.

Anyone know of any good sources?

 

[fitek]

Hi fitek. Sounds like a fun project. Do you have pictures posted? My brother (the non ebike puriest) pulls a one wheel "Bob" trailer behind his SWB Burley recumbent on multi-day multi-hundred mile tours, so I know you could pull a heavy trailer with a recumbent. If I was younger and wanted a narrow ride, (instead of my trike), I would start with a LWB recumbent with 20" wheels, add a "Bob" trailer with a 20" wheel, put hub motors in all three wheels, and carry the batteries on the trailer. At 36V this would probably go up most SF hills with moderate pedaling, and at 48V with no pedaling. It could be very stealthy, and the trailer could still have room to pack stuff.

P.S. I was born in SF in 1940, but have been a "native" oregonian since 1941.

Hi Rassy, I do have pictures posted. My personal website has details of the bike build under the projects section.

http://www.petervieth.com

I am not a native San Franciscan, though I have lived in the area for most of my life. I've been living in the city itself for only a short while. So cold and foggy!

I will have to pull up my battery analysis a little later in the day and see how many batteries I need. I planned on stuffing them inside the rather large main tube running the length of the bike. This would hopefully protect them not only from the elements but also tampering while parked.

-Peter

 

[fitek]

I purchased the BMC 750 watt motor from PowerPack motors. It arrived a couple of weeks ago.

I have been working on the motor controller software in AVR Studio 4 using the simulator. I will be making a run to Jameco to purchase components for the h bridges hopefully tomorrow.

Last weekend I went to the Electric Automobile Association rally in Palo Alto, California. There were some electric bicycles on display and it was good to check these out. In general they were very clean and complicated builds. Those that were on sale were offered at 3500-4000 dollars and weighed 90+ lbs. This makes me feel good as my current build cost is roughly $300 without batteries. Then again, my bike is not nearly as pretty.

Riding these bikes I did not like the weight because it was hard to accelerate compared to a normal bike, and the handle throttle was hard to get used to while pedaling. I will have to look into 'multiplying' the force I put into pedaling using the motor. Maybe some sort of torque sensor?

 

[fechter]

We must have missed you somehow. A bunch of us were there.

There are some systems that use a chain tension sensor to activate the throttle. This would eliminate the need for a handlebar throttle.

If you ran the top side of the chain through some kind of spring loaded idler, the idler pivot could be connected to the guts of a hall throttle. The harder you pedal, the more throttle it would give.

 

[xyster]

How does the bion-x system work?

 

[recumbent]

How does the bion-x system work?

The rear hub motor is split in the middle between the spokes and I'm too afraid to split the body of the motor. I visualize springs and pins come flying out and my warranty goes by-by.
But the motor does in fact have a peddle sensor and this makes the system more bike-like than motorized, and of course you can pick your power setting, mine is always set to #3 of the 1-4 settings, after hip replacement from an accident this serves me well, even on hills. The throttle for when I just got to do a shopping errand fast.

 

[Deepkimchi]

Ever think of going with a recumbent tadpole trike? Hub motor on the rear wheel? :wink:

Crystalyte has a good range of motors and ebikes.ca has a simulator for different motors vs voltage.

 

[fitek]

Hi all,

I should probably look around these forums to see if there are other events where ebikes will be present in the SF bay area. I think I've only ever seen one ebike outside of the EAA rally, at the main library in Redwood City.

I went and spoke with the irascible bicycle storage shack attendant at the 4th and King Caltrain station about bringing my bike on the train. He thought I may have trouble during rush hour (in fact, I couldn't get my upright on the express train, as it was full). Certainly these local issues deserve some forum.

Also had a friend show me the 'wiggle' through SF, a bike path that avoids major hills. It was a 35 minute trip from the Caltrain station to the Richmond. This beats the bus, but the nearly two hour commute is hard to justify daily.

Jameco doesn't stock decent FETs or DIP packaged ATMEGA88, and these just arrived from Digikey today. Still working things out with the software, and debating how to attach this BMC motor. I suppose I'll post to the other thread I started about that.