100W Mid Drive? - Am I an idiot and other questions

[abecrizer]

Hi everyone I am interested in what everyone here has to say about my project:

I currently commuting 7 miles down hill to work and the same route uphill to home.
With me pedaling only this takes me 20 minutes to work and 40-45 or so to get home.

I don't want to spend 40 minutes in the evening to get home after a shift, so I want some power assist.
I originally thought if I plugged away at it I would get faster, but alas this has not been the case.
I want to be exercising the whole time, but I want some motorized help onthe hills section.

My goal would be to get home in 20-30 minutes. I would want it to be a mid drive because it seems I can get away with a lighter motor
if the power is applied most efficiently. (In the summer the tempurature here is usually over 100 degrees)

My goals are:
1. Get home in 20-30 minutes, while exerting myself strenuously
2. Modify my bicycle as little as possible (keep my 3 chain rings)
3. Quiet
4. Add as little weight as possible
5. Cheap (If I was convinced a product was superior and would help me meet my other goals I could spend more money, but would prefer not to)

The first thing is: I want the motor to tie into the L crank. By adding a freewheel chain ring to the Left crank, either by welding on an aluminum
freewheel adapter after machined the crank for it to fit, or by getting a square Bottom bracket and putting a R hand freewheel crank over there
with modified pedal threads with some type of insert. When I pedal the motor will not turn, though if I back pedal it will have to be able to back drive)

I need help picking a motor, here are some thoughts so far:
1. Buy a E100 razor scooter, cut it up for the motor other pieces, add a jack shaft for a 2 stage reduction to the pedals
2. Right angle dewalt cordless drill with a sprocket instead of the chuck, tied into extra batteries (spins @ 500 RPM in low gear; also I know I need to remove
the anti-back drive device to back pedal, I found instructions how to do this on a robotic's club website)
3. 250 hub motor mounted similarly to what "Nader" has used.

My specific questions are:
1. Is 100w stupid? To me it seems I am probably 150-200ws by myself and adding 100w would be a HUGE help, but when you read articles
ppl make 250w seem punny. Is this b/c ppl are out for electric motor cycles or because 100 w will not help me much at all?

2. Is back pedalling necessary? It seems like it is so that you can put your foot down in a sudden stop quickly, but I can imagine learning to push back on the
motor and put the foot down

3. The dewalt uses a planetary gear box, and it seems that folks have said back driving a planetary gear box is not so good.
Also my dewalt drill is pretty loud.

4. Other motor recommendations that would fit my application?

Some things I considered and ruled out:
* AME 218 series right angle drive motor, I was dead set on this (I even made a cardboard model of the thing to figure out how
to mount it) until I realized it was worm driven and I would not be able to back pedal.
* R hand freewheel cranks, 4 chain rings, would have to move the motor chain while pedalling, and I don't thing the spacing would
work for the driving chain rings.
* factory mid drive kits: all seem heavy and over powered for what I am looking for (bafang is 250W and 3.8 kg and requires you to give up multi chain rings)

Thanks for any insight and help,

If it is at all relevant, my mechanical skills are moderately good IMO, though this project will stretch them for sure,
but I really don't know much about electronics and electromechanic stuff beyond simple circuits.
Which is one reason I picked the razor scooter and dewalt drill as they come with build in controllers I can just rewire into my application.

 

[SlowCo]

Sounds to me you should consider a small low power geared front hub motor. That way you keep all your bike gears, can freewheel downhill without drag and have a much easier install. Something like a Q75, Q85 or Q100(H):
https://bmsbattery.com/31-36v

What bike do you want to convert (make and model, photo?) and how steep and long are the uphill climbs?

 

[Rassy]

About a dozen years ago, before ES, I had purchased a couple of scooters for grandkids. One was a Scoot-And-Go that had a seat, with two 12V SLA batteries under the deck. The kids literally ruined the scooter so I took it back to repair it, but gave up because the front end was beyond repair.

I had recently retired and gave up biking when I moved to a house up a 15% grade, with 20% in my driveway. Anyway, I purchased a $50 mountain bike at Wal-Mart, used two u-bolts on the down tube to mount the scooter motor so that the cog lined up with the large chain wheel, and used the original chain from the scooter which meshed with the bikes chain wheel, and even used the trunk from the scooter to hang the batteries off the seat post. Along with the full twist throttle and controller from the scooter I had my first e-bike.

It only ended up with the 7-speed rear derailleur because the bike chain had to stay on the small front chain wheel since there wasn't enough clearance between the chains to use the middle chain wheel.

It actually worked pretty good, but I had to stop half way up the hill to rest and let the motor cool down. After a few dozen trips up the hill I got careless one day and pushed it too hard and burned out the little motor. When looking for a replacement motor I came across the Wilderness Energy hub motor kits and never looked back.

Word of warning, since then I've put together about a dozen e-bikes and e-trikes for myself and others, probably spent over $10,000, and still enjoy the hobby.

While I typed this you've had another response, and I agree that you should probably skip the DIY scooter step and go right to a hub motor or crank drive. Good luck with your project whatever you decide to do.

 

[spinningmagnets]

36V BBS01...worth considering for this user profile?

 

[nutnspecial]

Hi and welcome, these guys have valid points imo. I like the idea of perhaps picking up a cheap or used lite kit.

On the otherhand, to answer more directly, I love the idea of what you want to do. I'm not exactly clear on what you're describing, but there was a vid I found about a year ago of a guy overseas with a parallel setup powered by a grinder direct to rear wheel I wanted to reference. During a quick youtube search, I was amazed at the search result paths for 'diy ebike' + 'grinder' or 'drill'. Maybe check it out?

There's also amberwolf and I'm sure many others mostly in old threads that have done diy right here. The ideas are endless, almost . . . spherical?? Maybe doing a custom or goog site search will turn up a few more than will see your thread and comment right away. Please let us know what you find regardless of the route!

 

[abecrizer]

Thanks for all the ideas and info.

The bike is a Raleigh Grand Prix, an entry level road bike with 23x700 wheels.
(I will include a photo when I can take a picture in the day light.)

The route basically consists of a few miles of flat land, and then a long steady climb with that ends with a really grueling (at least to me)
1 mile climb up a ridge before I drop down to where I live. The climbing sections I probably am going 7-9 mph as most, at times 6.5.

Attached is a screen shot of the milleage and elevation profile of the route according to google.

A hub motor would be a very simple solution. Perhaps I am making things too complicated, however I have read that the tend to overheat on
climbs, and I have a long one, plus it is over 100 degrees most days in the summer time.

The Q motors recommended turn at 201 RPM, my math says I am currently turning the wheels at ~95rpm.
Any experience of this type of motor on a long climb in the heat?
Is there a hub motor that has a lower RPM? Which as I understand would mean a cooler running motor...

One advantage of the hub motor route would be if it didn't work out, over heated or something like that,
I could use the motor for a mid drive, with a lot more complex installation

 

[renaissanceMan]

My goals are:

3. Quiet
4. Add as little weight as possible
5. Cheap

I need help picking a motor, here are some thoughts so far:
2. Right angle dewalt cordless drill with a sprocket instead of the chuck, tied into extra batteries (spins @ 500 RPM in low gear; also I know I need to remove
the anti-back drive device to back pedal, I found instructions how to do this on a robotic's club website)

My specific questions are:
3. The dewalt uses a planetary gear box, and it seems that folks have said back driving a planetary gear box is not so good.
Also my dewalt drill is pretty loud.

Some things I considered and ruled out:
* AME 218 series right angle drive motor, I was dead set on this (I even made a cardboard model of the thing to figure out how
to mount it) until I realized it was worm driven and I would not be able to back pedal.

a.) Can someone chime in about Smilies' right angle drill idea?
b.) (If $$ weren't an issue, :lol How would you recommend mimicking the right angle drill approach, but instead utilizing RC components w/ a gearbox? http://www.hobbyking.com/hobbyking/...SK3_6374_149kv_Brushless_Outrunner_Motor.html. Think AFT dates Bafang who meets LR & gng.. but still decides to go d.i.y.. #vdayHumor.

 

[abecrizer]

I would drop the money on one of those motors,
except that I have a hard time figuring out how to gear it down enough.

Does some one sell a planetary gear box to go on one of those things?
If they did could it be back driven?

 

[Lurkin]

Depends. whats the budget and how much do you want to tinker? By tinker, I mean fix without it working periodically.

Given its nature, I would think you are thinking low budget, high reliability and low tinker. This lends better to a pre made available kit, Bafang being the easiest to install, but having done the 36v BBS01 250w commuter, I would skip it and go straight to 48v BBS02. Each to their own, but BBS02 is of a stronger, slightly larger in most areas construction and you are more likely to get more distance out of it without issues. Further, BBS01 is gutless when it comes to hills, really only of use on the flat. Similarly,. butchering scooters and using their motors... well, kinda asking for something that will require farting around when you need to get to work - not my cup of tea. For a second back up bike? Sure, why not.

That's coming from someone commuting 80km a day on a BBS01.

The BBS02 is a very, very simple installation compared to other mid drive options and is about as good as it gets in terms of reliability. Plenty of information on issues/fixes, start by reading the Bafang section of the Middrive section of the ES wiki. The same page will give you other options for mid drives. Most of the other mid drives around this money will be less reliable, noisier and without the integrated controller design/somewhat elegance.

having said all of that, there is advantages for commuting with a hub rather than a mid drive - much less wear and tear on the drivetrain, less complexity for problems with the internals of the mid drive - this is exactly why I am switching to a high power direct drive hub for the second bike I am about to put together.

 

[Miles]

Have a look at some of the small hub/mid motor set ups used in these threads:
https://endless-sphere.com/forums/viewtopic.php?p=290115#p290115
https://endless-sphere.com/forums/viewtopic.php?f=6&t=38553

 

[gman1971]

With the Bafang mid-drive you'll lose your 3 chainrings; so forget about pedaling uphill without motor assist. I would consider the front geared hub route... you don't have to mess with the back end of the bike (you get to keep all gears) you might need a torque arm for the front... other that that, seems like a no-brainer.

G.

 

[abecrizer]

Thanks again for the useful info.

After hearing every one's input it seems that the hub motor needs to be explored first.

I think my next steps are to go after the hub motor:
1) There is a local shop that sells e-bike stuff, I will see if they have any to play with.
2) Figure out if I need to buy a steel fork or if my carbon fiber one with TAs will survive.

One question about overheating: How do you know? Do you get a warning from the controller or do you just get black smoke of death?

The bafang definately seems to be the best mid drive bolt on kit I have seen but I would need
to get a NuVinci or similar for the rear to maintain the current gear range (~360%), which I could be convinced of,
however the weight of the Bafangs seemed high for what I was looking for.

Thanks for mentioning Torque arms, I had not considered hub motors before, and I just read there have been fatalities due to broke forks.
My fork is an Easton EC70, it is carbon fiber. Is this a BAD idea with torque arms? Safety is #1
I could convert to steel though I like the look of my fiber fork, even if it is dirty and banged up

Nelson 37: I am satisified with my cruising speed on flat ground: I can probably go 15-17mph for an extended period, and I am happy with that.

Lurkin, you asked about budget in terms of money and time tinkering:

I really do not have a firm number in mind, I probably could spend up to $1k on it. For me it really comes down to: if I spend more do I get something that fits my criteria better? I don't mind putting more time up front working on a project, to get it dialed, in, once done I want it to be low drama, low maintenance.
There are some things that probably exceed my skill level. I love the idea of a micro RC motor, but I really don't think I have the skills to fabricate a gear box for it,
if I found an article about someone's experience doing using other premanufacture parts to do it, I might want to go that route.

 

[Rassy]

After looking this over, etc., along with your front fork issue, I wouldn't consider anything but a Bafang, or similar, crank drive. Because of the hills I would go with a 48V BBS02, but less might work for you, and there are many options for your battery, but you won't need more than 500WH (48V 10AH).

As for losing your triple crank wheels, you probably won't miss it at all, but if you do you could always have options to fall back on. I've seen where some have put double or triple wheels on their crank drives. My choice would be to replace the rear derailleur system with a Nexus 8. Perhaps the new NuVinci would be okay, my only experience is with the older one which is quite heavy and can be hard to shift under load.

I put a bike together for one of my sisters over two years ago. It has a BBS02, a 48V 10AH LiFePO4 battery, and a Nexus 8 transmission. She has fairly extensive grades that are over 15% both to and from her house. She loves the bike.

 

[gman1971]

Yup, buy this, add that, etc... Its called throwing more money at the problem; a problem that could be addressed beforehand by going to something as simple and inexpensive as a front hub. I love mid-drives and I will push them onto anyone, but they are not meant for everyone. And he clearly stated he wanted to keep his chainrings so that rules the Bafang out. I sin of making the same mistake all the time, whats good for me isn't necessarily what other people are looking for.

Also, if the bike is full carbon I would probably refrain from installing a mid drive as my first kit on it... low power hub with a torque arm should work even on carbon forks... And since you seem to be a bit of a Bafang fanboy, well I will admit I am a total Cyclone fanboy so if it was me I would take a Cyclone 3000W any day over any Bafang; its a lot cheaper and you get to keep your chainrings, plus it will eat Bafangs for breakfast any day of the week while barely getting above ambient temperature.

G.

After looking this over, etc., along with your front fork issue, I wouldn't consider anything but a Bafang, or similar, crank drive. Because of the hills I would go with a 48V BBS02, but less might work for you, and there are many options for your battery, but you won't need more than 500WH (48V 10AH).

As for losing your triple crank wheels, you probably won't miss it at all, but if you do you could always have options to fall back on. I've seen where some have put double or triple wheels on their crank drives. My choice would be to replace the rear derailleur system with a Nexus 8. Perhaps the new NuVinci would be okay, my only experience is with the older one which is quite heavy and can be hard to shift under load.

I put a bike together for one of my sisters over two years ago. It has a BBS02, a 48V 10AH LiFePO4 battery, and a Nexus 8 transmission. She has fairly extensive grades that are over 15% both to and from her house. She loves the bike.

 

[2old]

I'm not as expert as most of the others who have responded, but wouldn't ever consider a front hub on a carbon fork even with two torque arms. Also, try a front hub system before you buy to ensure that you receive the power that you want. Perfect (IMO) for your application, BBS02, although the Cyclone will suffice with a little more tinkering.

 

[abecrizer]

Thanks for everyones comments and input,

At this point my default plan is to build a front wheel with a Q75 or Q85.
So I am doing research to better understand what is involved before I buy anything.

I like 2old's idea of trying before I buy, but any idea of how to go about doing that?

I am still looking, but haven't found any shop selling Cute hubs where I could go try it out...

 

[cwah]

100w mid drive doesn't exist. You can get bbs but you are directly propelled to 4kg+

 

[Joe T.]

I don’t see the advantage of spending good money on a limited drive system. You can still get a workout on a powerful electric bike. Just pedal hard and you will get a workout. Most of the riding I do now are the same trails and roads I have conquered with my regular bike. Now I do them all faster. I am still tired at the end of the day.

In 2013 I bought a GNG and I was E-biking with in hours. I later built a custom bike around the GNG but that was basically for the fun of it.

I would buy a popular kit with decent power like 48V500W range and bolt it on. Done in an afternoon, E-biking the next day!

 

[abecrizer]

Yeah, there is lots to think about.
Today in my quest to find a similar hub motor to ride I talked to a guy today who told me he put 2 chain rings on a Bafang.

20 lbs added to the bike just seems astronomical to me, it would nearly double the bikes weight.
I do get it that the motor easily makes up for that.

 

[abecrizer]

I ultimately went with a Q75. Description of results here, if anyone is interested:

https://endless-sphere.com/forums/viewtopic.php?f=3&t=81087