Looking to build an eBike

General Discussion about electric bicycles.
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Blindsay   1 µW

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Looking to build an eBike

Post by Blindsay » Apr 18 2021 9:50am

Hey all,

Looking to build an ebike, I thought about converting mine but it did not seem to be a good candidate for a high power setup and I like the idea of taking my time building something new while still having my current bike available to ride. It is a 2013 Trek Fuel ex7 for reference.

I was watching this video - https://www.youtube.com/watch?v=MefhrTBQxY0 (I am also really into building PCs) and got me thinking building something like that would be cool.

Definitely need something I can still pedal with, I am trying to lose weight and want to pedal as much as I can but still have the power when I need it. Would use it around town to commute to work (only 5mi each way) and I have a few friends in town I would use the bike instead of my car). Would like the bike to be able to comfortably do 40mph (So probably be able to do much higher than that but I don't want to run it at 100% all the time). Less worried about range but if 50mi+ was achievable (I know it depends on how hard I push it) that would be great. Right now I weigh about 350lbs so I need to build the bike for that but my target weight will be 200 over the next couple years.

While I am loosing weight I wont be doing any crazy downhill riding, maybe some light trails and mostly on road stuff while I get back in shape. So I was thinking for now spend more of my money on the electronics and buy an ok (but safe) front/rear shocks (I know how expensive they can get, was thinking like a DNM setup instead of say a Fox setup) and then when i start doing more serious riding upgrade them as needed.

I have a general idea of what parts I need but not sure what are good for brands and a good value without crossing that line of being unsafe. Like I see this frame on amazon but is it going to kill me? - https://www.amazon.com/gp/product/B01GSLQ7Y2

Do you really save that much money DIY the battery pack vs buying it? I was looking at 320 Samsung 18650 cells (20s16p for 72v/40ah) and just the cells alone were like 800 bucks. Not sure on a good BMS yet and how much wattage I need on the motor (keeping in mind I'm 350lbs + 100lb+ bike)

Don't have a set budget but If I can keep it under $4000 great, if not I am in no rush to build and don't mind slowly building it up (I enjoy building things so that is a big part of the fun to me).


Sorry for the long post. Thanks!

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Chalo   100 GW

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Re: Looking to build an eBike

Post by Chalo » Apr 18 2021 10:30am

If you put a big heavy battery pack like that on your bike, you won't pedal it enough to get meaningful exercise. A fat heavy powerful e-bike discourages vigorous pedaling. You may think you'll do it, but you'll quickly fall out of the habit because pedaling doesn't really make any difference. Pedaling can be uncomfortable or even impracticable if there's a bulky pack in the frame.

If your bike is satisfactory to pedal, battery range becomes a much less important limitation. You can use electric power when it gives the most benefit, rather than all the time.

I recommend using a geared hub motor of 750W or less, both to reduce bike weight and bulk, and to make pedaling an important contribution to the bike's power. There's an advantage for heavy riders like you and me in using a front hub motor, because a rear hub motor inevitably makes a weaker, less reliable wheel than one built on a normal hub.

You and I are in the weight range where square taper bottom bracket spindles like those in Bafang BBS02 or Tongsheng TSDZ2 are susceptible to breakage. If you must have a crank drive, let it be a Stokemonkey setup with a RH/LH drive BMX crank that won't break and hurt you.

If you use your existing mountain bike, the Grin All Axle front motor would work with the fork you have. I don't know of any other hub motors that will do it.
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Blindsay   1 µW

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Re: Looking to build an eBike

Post by Blindsay » Apr 18 2021 11:13am

Thanks, If it comes down to it I would rather keep my existing bike for exercise and build an eBike. The youtube video I linked is a pretty good idea of what I was thinking of building and I was definitely thinking of much more than 750watt. The only * I would put on my weight is that it is going to decrease here pretty soon fairly rapidly and my target is like 200-220 range

Another example of something that looked interesting was this - https://www.youtube.com/watch?v=F_yHTRN6DMs

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Chalo   100 GW

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Re: Looking to build an eBike

Post by Chalo » Apr 18 2021 2:51pm

Yeah, suitcase bikes like that aren't for pedaling. It's awkward and non-intuitive to do so when you're riding one. They're even heavier than they must be to support so much motor and battery, and not nearly as strong as their weight would suggest. Riding one with pedal power only is something you'd only do in an emergency.

So you can get a bike like that and use it instead of a car, and that's good. But you most likely won't lose weight or improve your fitness that way.
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Grantmac   10 kW

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Re: Looking to build an eBike

Post by Grantmac » Apr 18 2021 3:38pm

5mi commute and looking to improve fitness, what you want is a bicycle (not an ebike). And definitely not a lightweight electric motorcycle with pedals.

Blindsay   1 µW

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Re: Looking to build an eBike

Post by Blindsay » Apr 18 2021 3:47pm

Chalo wrote:
Apr 18 2021 2:51pm
Yeah, suitcase bikes like that aren't for pedaling. It's awkward and non-intuitive to do so when you're riding one. They're even heavier than they must be to support so much motor and battery, and not nearly as strong as their weight would suggest. Riding one with pedal power only is something you'd only do in an emergency.

So you can get a bike like that and use it instead of a car, and that's good. But you most likely won't lose weight or improve your fitness that way.
Alright, So I will just keep my current trek bike for fitness. I am still interested in building an ebike for fun. I would like to build something along the lines of the example ones I posted.

Would the frame I linked in my first post be ok to start with? Once I have the frame I can start planning how I am going to fit the battery and BMS (and everything else)

Thanks!

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Chalo   100 GW

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Re: Looking to build an eBike

Post by Chalo » Apr 18 2021 4:17pm

Blindsay wrote:
Apr 18 2021 3:47pm
Would the frame I linked in my first post be ok to start with? Once I have the frame I can start planning how I am going to fit the battery and BMS (and everything else)
I don't see why not. Suitcase bikes don't seem to vary as much in quality as traditional bikes, so as long as you get one with a decent reputation, it should be about the same as the others. I think the main distinction would be between an aluminum frame and a steel frame, with aluminum being preferable.
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markz   100 GW

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Re: Looking to build an eBike

Post by markz » Apr 18 2021 4:23pm

RV'ers and aeroplane fliers maybe into small folding 20" bicycle. You wouldnt know when their riding around and I dont see many around when I am riding but I do see them more closer to downtown so add condo's to the list. Oh and dont forget sailboat owners.

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Chalo   100 GW

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Re: Looking to build an eBike

Post by Chalo » Apr 18 2021 6:59pm

markz wrote:
Apr 18 2021 4:23pm
RV'ers and aeroplane fliers maybe into small folding 20" bicycle. You wouldnt know when their riding around and I dont see many around when I am riding but I do see them more closer to downtown so add condo's to the list. Oh and dont forget sailboat owners.
By "suitcase bike", I don't mean a folding bike that can go into a suitcase. I mean a bike that has a suitcase full of batteries in place of a normal tubular frame.

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markz   100 GW

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Re: Looking to build an eBike

Post by markz » Apr 18 2021 7:47pm

Ah my bad, I should have clued in. I just call those kind Enduro frames.
The average person thinks they are a motorbike riding on a sidewalk, pathway or sports field.

Fun Fact - Have you ever heard of a suitcase computer?


Chalo wrote:
Apr 18 2021 6:59pm
By "suitcase bike", I don't mean a folding bike that can go into a suitcase. I mean a bike that has a suitcase full of batteries in place of a normal tubular frame.

Image

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dogman dan   100 GW

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Re: Looking to build an eBike

Post by dogman dan » Apr 19 2021 6:58am

This is why I read ES still after 12 years. For amusement.

He's going to lose weight, riding 5 miles, at 40 mph. Okey dokey. It will work if he rides 100 miles on the weekend. I'm assuming no 1000 foot vertical climb either way.

Honestly, he needs to keep riding the pedal bike to work, or with a low power e bike, take the 15 mile route to work 5 miles away. That's actually going to result in a ride long enough to feel it.

NOT SAYING DON'T BUILD THE FUN 40 MPH BIKE. But if you keep speed down to 20 mph on the ride to work, and do at least 20 miles round trip, and keep the throttle down to where you feel the pedals and work up 100w effort from your body, you can most definitely get good workout with an e bike. Put your bike in 20 mph gear. Throttle to 20 mph and start pedaling. Then back off the throttle to where you feel good weight on your feet on the pedals. Constantly adjust throttle to keep your effort steady, but not hard effort. Ride one hour per day, minimum.

On the weekend, have huge fun on that homemade motorcycle with pedals.

999zip999   100 GW

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Re: Looking to build an eBike

Post by 999zip999 » Apr 25 2021 10:22am

How much money do you want to spend speed cost money range cost money

LewTwo   100 kW

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Re: Looking to build an eBike

Post by LewTwo » Apr 25 2021 4:18pm

The original Compaq Computer (Intel 8086) was suitcase computer.
It was inspired by the Osborn CPM (Zilog Z80) computer ... used one of those in a college programing course (5 amber CRT inch screen).
Also had a "portable" Commodore 64 (MOS Technology 6502) that was suitcase computer.
The more I learn the more obvious the immensity of my ignorance becomes.
Weight Wennie E-Bike https://endless-sphere.com/forums/viewt ... 3#p1173723
Shaft Drive Grocery Getter https://endless-sphere.com/forums/viewt ... =6&t=90718
...and thanks to Justin!

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