Help with making a fast ebike from scratch

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Andrew Storlie   1 mW

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Help with making a fast ebike from scratch

Post by Andrew Storlie » Apr 14 2016 12:57am

Ok this is my first post, bare with me as im new to ebikes but i do have a decent amount of electrical knowledge.

By next summer i want to have built a full ebike

I plan to use a trek marlin 7 with a 21" frame and 29er tires

I need help/advice on what parts to get.

I want to use a single rear hub motor that will get me up to about 50mph maybe little more. I plan to build my own battery packs using 3.7v 25,200mah cells (i want long long run times)

I know i want a sine wave controller that can put out about 30-35amps

I live in a desently flat area so i know a hub motor will do.

These are the parts ive KINDA put together for a build

Any advice on motors, controllers all that stuff is helpful

Bike: trek marlin 7
Hub motor: http://m.ebay.com/itm/36-80V-Ebike-Scoo ... nav=SEARCH
Controller: NEED TO FIND
Batteries: http://www.batteryspace.com/polymer-li- ... d-dgr.aspx

No need for lcd screen or anything. Just half twist trottle

My math... the motor listed says 410rpm at 36v so roughtly 11.38rpm per volt. At 66.6v (18s) i should get 758.5rpm at full throttle. A 29er tire is 7.3ft circumstance so full trottle would be ~63mph no resistance so i would assume about 50mph in real life flat ground... am i right or way off.

Idk about all the motor specs and what not so if someone can help with that too... very helpful thx in advance.

My budget is 2500ish, can be more... for everything including the $700 bike.

All advice will be noted as im a real noob and i want to make something that will last and i can ride everyday

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Chalo   100 GW

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Re: Help with making a fast ebike from scratch

Post by Chalo » Apr 14 2016 1:31am

50mph is too fast for ordinary bicycle components. Coasting down a smooth mountain highway, sure-- but most riding isn't like that. Energy levels scale as the square of velocity, which counts for bumps and vibrations too. You'll need over 4000W to hold 50mph. Remember that the percentage of that energy that goes into tearing up your bike is at least as high as when you're pedaling along at 100 to 200W. When you stop from 50mph, you're asking eleven times as much from your brakes as when you stop from 15mph. Every time.

I'll be among the first to tell you that unsuspended bicycles are best for street use. But not at 50mph. That's motorcycle territory; use a motorcycle. Or if not, at least go out of your way to construct a bicycle that will be safe and reliable at that speed. Your budget won't cover both a safe and reliable bike, and the electric parts you'll need.
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Re: Help with making a fast ebike from scratch

Post by Andrew Storlie » Apr 14 2016 1:40am

Chalo wrote:50mph is too fast for ordinary bicycle components. Coasting down a smooth mountain highway, sure-- but most riding isn't like that. Energy levels scale as the square of velocity, which counts for bumps and vibrations too. You'll need over 4000W to hold 50mph. Remember that the percentage of that energy that goes into tearing up your bike is at least as high as when you're pedaling along at 100 to 200W. When you stop from 50mph, you're asking eleven times as much from your brakes as when you stop from 15mph. Every time.

I'll be among the first to tell you that unsuspended bicycles are best for street use. But not at 50mph. That's motorcycle territory; use a motorcycle. Or if not, at least go out of your way to construct a bicycle that will be safe and reliable at that speed. Your budget won't cover both a safe and reliable bike, and the electric parts you'll need.
Well i dont have a license so thats why i ride a bike, and would like to make an ebike. I have a trek ds8.4 right now that i bike minimum 25 miles a day, and have been for the last 4 years. I was thinking mid drive so i could use my gears but then all the wear and tear of the gears from the motor is bad.

Ok so in your mind, what is something i should shoot for. Is 30mph a good speed? I want a pretty fast bike. But id rather have distance than speed. But i dont want a 20mph bike top speed. I can avg 18mph over a 200 miles ride with my legs. Looking for more sustained speed so i dont have to ride so long to work everyday

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Chalo   100 GW

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Re: Help with making a fast ebike from scratch

Post by Chalo » Apr 14 2016 4:50am

I guess the thing to keep in mind is that you gain a lot of range by trading off a little speed. If you use 52V worth of those 25Ah cells you mentioned, you have about 1.3kWh to spend. Let's disregard electrical inefficiency, even though you don't get to do that in the real world. At a steady 50mph, that's about 20 minutes or 16-1/2 miles, from full to empty. Àt 30mph, you get over an hour and a quarter and approximately 40 miles from the same amount of energy. At 20mph, you get over 3 hours and 40 minutes and 75 miles. (Using my guesses at weights and dimensions with the speed/power calculator at Kreuzotter.de).

This is not to say you should limit yourself to 20mph. But limiting yourself to only as much speed as you require gives you substantially more range and costs much less in equipment than going even a little bit faster.
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Re: Help with making a fast ebike from scratch

Post by dogman dan » Apr 14 2016 5:33am

The others covered it pretty good,(its going to take 5000w or more)

50 mph with no rear shock on the street is pretty much suicide IMO. But I do get it, that you won't always be going 50. Someday you will hit a bump you didn't see, so practice riding a bike on just the front wheel at 50 mph. :shock: It's real fun, I can tell you that from experience.

As always, my advice, build for closer to 35 mph. If you need 50 mph to keep up with traffic, buy a 150cc or larger motorcycle or scooter. If you have no license you're less likely to get pulled over riding that than riding a bike that goes 50 mph. You can get a decent used motorcycle well within that $2500 budget.

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Re: Help with making a fast ebike from scratch

Post by Simonvtr » Apr 14 2016 7:00am

To get an idea of the power you would need to hit 50mph you should look up a few videos from member icecube578. He runs the endless sphere podcast on youtube.

Here is one that might give you an idea of what is needed.
https://www.youtube.com/watch?v=83I2DknGDuA

Also get over to ebike.ca and run the motor simulator to see what kind of power you need to get that motor you have listed to go 50mph.
http://www.ebikes.ca/tools/simulator.html

Those lipo you have linked is comparable to hobbyking multistar lipo battery 30$ for a single 2c lipo battery is a bit over price.
http://www.hobbyking.com/hobbyking/stor ... _Pack.html

Going lipo you will need to find a way to balance those cells with either a BMS and Bulk charger or noBMS and a hobby charger with a balancer.

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Re: Help with making a fast ebike from scratch

Post by FluxZoom » Apr 14 2016 12:37pm

RTFW N00B https://endless-sphere.com/w/index.php/ ... a_Go_50MPH

The best part here is, he wants to do it with an aluminum frame.

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Re: Help with making a fast ebike from scratch

Post by spinningmagnets » Apr 14 2016 2:21pm

For a reliable 40-MPH, on the street, use a MXUS AT 60V. For a reliable 50-MPH, use the QS at 20S (74V nominal, 84V HOC)

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Re: Help with making a fast ebike from scratch

Post by brumbrum » Apr 14 2016 3:30pm

Also, for the bigger motors such as qs205,cromotor etc you will need 150mm rear dropout. I think the mxus maybe more like 140mm.
My NYX and cromotor build
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Re: Help with making a fast ebike from scratch

Post by wesnewell » Apr 14 2016 4:01pm

That motor description is all over the place. 30CM-45CM magnets. What are they really? And I'm pretty sure that's 2500W peak for the noitor rating. Probably a 1000W motor. Wouldn't touch it. Batteries are 65 cents per wh for 2C cells. I pay 20 cents for my 10C and 20C cells. I'd advise a mxus 3000 3t motor with a 24 fet 72V controller and a 20-24s rc lipo pack from HK. Select mxus 4503
http://www.ebikes.ca/tools/simulator.html
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Mongoose 26" Ledge 2.1 mtb bike $99, yescomusa.com 48V 1000W rear hub kit $200, Hua Tong 72V 40A controller $35, 10ah 24s lipo $217=~43mph, range=45 miles @ 20mph. 25K miles and still going strong.
Huffy Fortress 3.0 with MXUS 3000 4T motor, 24s lipo, 96V 60A controller. Total cost with extras <$700. Top speed ~50mph
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Re: Help with making a fast ebike from scratch

Post by mudale222 » Apr 14 2016 4:12pm

I think that 4 a noob it's better to start with kits, it's much easier and it's let the man feel the speeds and understand what we are all talking about.
Basically, what i recommend is the leaf motor kit 1500W (i have him for 5500 km and keep going mo problem). It's very fast kit (too fast 4 hard tail, i'm admitting that), it's can get 60-80 kmph / 35-50 mph (i even take it to short driving in highway sometimes). And the best part that if he want's to upgrade it later - the hub can take much much more.

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Re: Help with making a fast ebike from scratch

Post by heavymetalthunder » Apr 14 2016 6:54pm

I agree with Chalo and Dogman Dan. You really don't want to go much beyond 35 MPH on a non rear suspension bike. Even going 30 on a full suspension bike can give a rider problems. Take the advice other have given you, bicycles are not really designed to go fast. Plan for a max speed of 30 to 35 MPH. As you go faster the costs will rise faster as you need a better bike, motor, speed controllers, lights, and most of all more battery power.

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Re: Help with making a fast ebike from scratch

Post by Andrew Storlie » Apr 15 2016 12:22am

For all those who replied thx you very much.

So lets start new then... say i keep my trek ds8.4 21" frame 700c tires.

35mph top speed set up.

Not including batteries, i have that handled. What is a good reliable hub motor that i can still use my sprocket set on (if i can)

And what is a good sinewave controller to use. Ive heard sinewave is better for the motor and much more quiet

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Re: Help with making a fast ebike from scratch

Post by Chalo » Apr 15 2016 12:49am

Have you considered a crank drive like BBSHD? It's amazing to use, and you get to keep all the parts you like about your bike. Get it with a 52 tooth ring and you'll be able to scoot along at a surprising pace. You might want an aero bar to go with that, though it would also help with a fast hub motor.
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Re: Help with making a fast ebike from scratch

Post by Dauntless » Apr 15 2016 1:28am

Another possibility is to look around for a moped or small moped like scooter like the Honda Supercub. One they've burned up the motor or took it apart and lost some of it. This world is full of bikes where they lost things that sit in the garage for awhile, it's a great hobby picking those up cheap and putting them back together. I've bought them as low as $50 and never paid more than $200. Picture wheels capable of 50mph, suspension, maybe you reconfigure the handle bars to make it more comfortable at 50mph. But if you get one with pedals you still get to register as a moped.

I'm not usually telling people to enter their location, but at times like this I've been known to search the posters' local Craiglists for suitable opportunities. But here's an example maybe I should run into LA and pick up. $75. No pics, I don't know if it's a GY6 engine or what, so I don't know how convertible it is, but it's representative. http://losangeles.craigslist.org/lac/mc ... 29748.html

I once got one just like this for $100 not running. You don't even need running.

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Re: Help with making a fast ebike from scratch

Post by dogman dan » Apr 15 2016 6:02am

You can run just about any of the direct drive hub motors that are 135mm wide axle on that bike. But to use a 9 speed gear, you'll have to use a 9 speed screw on freewheel. Your existing cassette won't fit it. It might be worth it, to convert your rear shifter and chain to 7 speed. Fact is, your bike is a somewhat poor choice for converting, since it's 9 speed.

As you get into motors with real beef, you lose space because the motor is wider. Most of those running a 3000w muxus are not using multiple gears, or certainly not very many gears, unless they have a much wider rear axle space.

In any case, once you power up, you will NOT be pedaling, and will NOT need anything but one high gear for pedaling for the first 20 feet, or any pedaling at slower speeds you may do. So basically, you could just take the damn chain right off the bike.

You need to get over one thing. You want to build a motorcycle, but you want it to also be a bike. Sorry, but you can't do that really.

But you can build a bike, with a motor, that goes 30-35 mph pretty easy. Get a fairly ordinary (fits in 135mm) direct drive hub motor, and a controller that can run 48-72v. You can start with a kit if you like, and have 30 mph on 48v, with it's original controller. It will be possible to pedal and motor up to about 25 mph. Above that speed, you could pedal still, but you'll be just clown pedaling, flapping the legs.

As you gain some experience, you can then decide if you are going to take the plunge, buy a full suspension frame that can take a 150mm motor, buy that hot controller, build that bike that does 40 to 50 mph. You won't be wasting a ton of money along the way. A serious bike commuter almost always needs a spare bike anyway.

So start with a fairly cheap, fairly normal e bike on your trek. Then build your motorcycle with pedals next winter, for next summers riding.

Or, take the plunge right now, but NOT on that Trek frame. It sucks for making a motorcycle out of it. Sell it off.

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Re: Help with making a fast ebike from scratch

Post by Andrew Storlie » Apr 15 2016 10:51pm

Ive looked in to the bbshd mid drive but i dont like that my pedals turn even if im using throttle only. If i want ti coast under power ill still have to turn my pedals. But i guess with a 52t ring even at high speed i wouldnt have to pedal fast

Would the bbshd be a better fit on the trek ds8.4 i have now or a trek marlin 7?

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Re: Help with making a fast ebike from scratch

Post by FluxZoom » Apr 15 2016 10:57pm

Andrew Storlie wrote:Ive looked in to the bbshd mid drive but i dont like that my pedals turn even if im using throttle only. If i want ti coast under power ill still have to turn my pedals.
What makes you think this is the case?

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Re: Help with making a fast ebike from scratch

Post by Andrew Storlie » Apr 15 2016 11:03pm

I just watched a video on the BBSHD... the guy had the motor running but wasing pedaling? Is that something custom or does it involve part of the bbshd kit?

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Re: Help with making a fast ebike from scratch

Post by Andrew Storlie » Apr 15 2016 11:07pm

Im sorry if i sound like an idiot... just new to this all,

Can someone tell me the rpm of a BBSHD at 52v (14s)

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Re: Help with making a fast ebike from scratch

Post by Chalo » Apr 15 2016 11:19pm

Andrew Storlie wrote:I just watched a video on the BBSHD... the guy had the motor running but wasing pedaling? Is that something custom or does it involve part of the bbshd kit?
The BBS02 and BBSHD use a one-way clutch in the crank so the motor can propel the ring when you're not pedaling. It's [text removed by moderator], but it works. Plus, if you use it in PAS mode, you'll never even notice it does that.
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BBSHD help

Post by Andrew Storlie » Apr 16 2016 12:34pm

So ive decided to go with a BBSHD with a 52t ring. I live on flat grounds. So not too worried about heat

For reference ill be putting it on a trek marlin 7 21" frame 29er tires

Where should i buy a good kit that will allow me to unlock the speed limit. On the controller. Ill be building my own 51.8v (14s) battery pack for huge distances. 51.8v @ 25.6ah is what im planning if not bigger.

Questions... the marlin 7 has a 9 speed cassette, should i get the marlin 5 so i only have 7 speeds? Then upgrade to hydraulic breaks for the better stopping?

I want a kit that has options to include the shift sensor, hydraulic brake sensor and if possible a sinewave controller so the motor isnt as loud.

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Re: BBSHD help

Post by ido » Apr 16 2016 11:43pm

The BBSDH comes with 46t chainring. I haven't seen a 52t ring for the BBSHD on the market.

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Re: Help with making a fast ebike from scratch

Post by dogman dan » Apr 17 2016 8:08am

Love it that you are at least now considering a bike that could even be legal to ride. But even my conservative opinion doesn't blanch at making a bike that is 15 mph faster than legal. My main concern is just that you can ride it safely, at it's top speed, on crappy city streets. So for most hard tail bikes, things get a bit tricky above 35 mph.

As you learn more, you will see that many ebike conversion kits allow use of either a throttle, or PAS to control the speed of the bike. So for example, with the bb you can set it up so it goes when you pedal, or you can just twist the throttle and go, your choice.

Some mid drive do make the pedals go when you throttle, but mostly those are home mad stuff, or the older stokemonkey type mid drives. None of the more modern mid drives do that, they use the clutch in the crank so you can ride the throttle without the pedals having to spin.

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Re: Help with making a fast ebike from scratch

Post by LewTwo » Apr 17 2016 1:41pm

Andrew Storlie wrote:Im sorry if i sound like an idiot... just new to this all,

Can someone tell me the rpm of a BBSHD at 52v (14s)

750 watt http://www.szbaf.com/en/components/comp ... 32750.html
1000 watt http://www.szbaf.com/en/components/comp ... 21000.html
130-150 RPM at 48 Volts (per spec) but the variance is probably due in part to variance of the battery charge level.
Otherwise in theory (52/48) * (130 to 150) = 140 to 162 RPM
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