Is this still an eBike?

[briansrapier]

Greetings. I am considering undertaking my first eBike project and am interested in some input as to the feasibility of my ideas.

Here's the short version: I live in a moderately hilly area and am interested in building an eBike for commuting back and forth to work. I have a 17 mile commute (each way) along roads with speed limits ranging from 35 to 55 mph. To avoid getting clobbered or causing someone from rupturing a blood vessel if they happen to come up behind me, my thought is that I'll need to be able to do 45 mph (on the flats).

I've been looking at different designs of eBikes and ev motorcycles. From what I've read and seen, I probably want to go with a 48 volt system (of higher). My plan is to take apart my Specialized FS bike and reutilize the rear triangle, rear shock, front forks, and disc brakes. I have been considering using a Sachs/Sram 5 or 7 speed internal hub. I am thinking of not having pedal assist (please don't beat me up).

The big question is the motor. I want the speed and range, so I thought an Etek motor might be what I'm looking for, but my fear is that it is too powerful for the bike components and would likely trash the chain and hub in short order. I have also considered the Cyclone and Crystalyte hub type motors, but I am not sure if they are capable of the higher speeds. Plus it would negate the ability to use multiple speeds.

So, I'm not sure if I should be posting these ideas here or if I should seek out a different forum more attuned to ev motorcycles and the like.

Thanks for your input.

 

[fechter]

45 mph is a pretty tall order. A Crystalyte 5303 or 5304 with lots of juice might get you there. I don't think it would really be safe at those speeds on a bicycle though. I'd recommend a more motorcycle like ride. If something came apart on you at those speeds, you'd be in for some major road rash. A large frame can carry more batteries too, and to get the desired range at anywhere near 45, you'd need lots of them.

If you could stay under 30mph, you could probably do it on a bicycle.

 

[Knuckles]

I think a chopper frame would do 45 MPH safely. My chopper bike does 30+ MPH and feels very safe compared to my diamond frame at same speed. The problem is wind resistance skyrockets over 30+ so a fairing or windscreen may be essential. Also getting pedals to add watts to the drive train (at a comfortable cadence) is a gearing challenge at your desired 45 mph speed. A minimum of 1-kWHr of bats and a 72V controller system would be the min needed I imagine. A 2 X 2 (front and rear motors) may do it. I’ve had the same thoughts for a while now and my dream chopper would have a PMGR rear and a non-geared brushless in the front. Two 72V 50-amp controllers off of one throttle. Regen from the front wheel would be an awesome breaking mechanism too (still need mechanical brakes of course).

 

[briansrapier]

That's quite a system you're eluding to: two motors, two controllers, plus bats. Off the top of my head - $3,000?

 

[wanders]

I have a 1998 Specialized FSR Ground Control with which I have been considering something similar. My thought was to redesign the rear triangle (chain stay and seat stay parts of the 4 link rear suspension), fabricate a new set of stays out of CrMo and make a custom mount for a motor, and also make the rear dropout spacing 150mm and use a wide downhill hub with a disc mount. Instead of using a disc brake, I would use the 6-hole mount to attach a sprocket and drive it with a motor. The Mars brushless is a nice motor, but it is large for a bike and fitting it low (where you would want to for balance reasons) would interfere with the pedals. For you, that may be no problem, but I want it to be a bike as well. So I've been considering other motors.

I would also add that IMO multi-gearing an Mars brushless on an e-bike is probably not needed. A smaller motor might benefit, perhaps, but the efficiency curve of the Mars brushless is pretty flat if you are moving at all.

Anyway, so far, as you all can tell, my idea is pretty half-baked. When I get the time, I plan to model it in Solidworks and see if it makes sense.

Willie

 

[Knuckles]

That's quite a system you're eluding to: two motors, two controllers, plus bats. Off the top of my head - $3,000?

NOT $3,000 at all!. Nirve chopper less than $300. Motors $150 each. Controllers $150 each. Throttle $25. Bats (well then you can spend money - but I use $0.60/WHr) so a 1-kWHr is about $600 for NiMH. Labor is your own and that is not calculated. Also a windscreen made from plexiglass would be nice.

 

[briansrapier]

Wow. That sounds very reasonable. I'd like to get more info on where you are getting these prices from. Being a newbie at this, I google everything and haven't been able to locate anything in that range.

And, to answer fechter's questions about stability: my plan is to build a custom frame creating mounts for the heavier components lower for a more stable center of gravity. Since I'm planning on eliminating the pedals, I can also lower the seat height to further stabilize the ride. I plan on using as many downhill components as I can to make it more reliable.

 

[CGameProgrammer]

I have gone 47 mph on the flat -- fastest ever e-bike speed for me was 50 mph on a downhill. It was with a Trek 820 frame which is a steel hardtail, with a rear Crystalyte 5303 hub motor and something like 96V 40A of power. 72V 40A got me 42 mph on flat ground with the same system though. I made no frame modifications at all, just replacing the front wheel/fork/brake with a disc brake setup.

It definitely isn't safe though. The worst part of that setup was all the weight was on the rear, so the front end wobbled quite a bit at high speeds. Putting more weight in front (like by placing the batteries in or around the frame triangle) alleviates that fairly well.

A motorcycle or motorscooter platform is significantly safer at those speeds, particularly because they have lights, blinkers, mirrors, and people recognize them as vehicles that can go fast. But a bicycle can go fast and there are a number of us that go 40+ mph on them.

 

[Knuckles]

Since I'm planning on eliminating the pedals, ...

If you eliminate the pedals it's no longer a bicycle! Even at (the sick speed of) 45 mph you may still argue with a cop (or Judge) that it's a bicycle. Without pedals you are clearly riding an unregistered motor vehicle and you may get seriously busted by the man! KEEP THE PEDALS! Make a funky shaft drive or somethin'. Plus that would be totally cool to see!

btw there is Florida case law that sent a guy to jail because he had no pedals (no pedals = misdemeanor charge ... pedals = case dismissed)

 

[huskydave]

I have a crystalte 5304 72v 48a controller and lithium batteries 80v and it does over 70km/h and after riding that fast it is scary and dangerous on a bike. If you want to maintain those speeds you should look at stronger frames and good suspensions. I think if you cruise at 20-30mph and have/use the extra power to get out of trouble or keep up with traffic briefly it is a good way to go. If you plan on riding roads a lot or in congested areas I would want brakelight and turn signals and a better vehicle than an ebike but if you can take sideroads bikepaths or have a bike friendly location you should look at an ebike. I don't plan on pedaling either unless I have a breakdown which has happened and I was sure glad I had pedals to get me home.

 

[lazarus2405]

First off, welcome!

What you want is very doable. I would recommend a Crystalyte 5303 in the 70v-90v range. My 5303 in a 26" wheel at 84v and 55 amps topped out at 47mph. My same 5303 at 84v 50a (different controller) and in a 20" wheel has done 44mph twice since I set it up (been quite busy with exams and such). I'm going to be running it at 112v soon, aiming for the 50-55mph range. Several others have done what I have on Crystalyte x5 motors. One person has pushed it all the way to 60mph. So, what you're asking is definitely doable.

The Etek and similar motors don't work out well on a bike frame. They're a pain in the rear to mount, the drivetrains are not trivial to set up, and they provide far more power than an ebike needs to go 45mph. 8)

I have also considered the Cyclone and Crystalyte hub type motors, but I am not sure if they are capable of the higher speeds. Plus it would negate the ability to use multiple speeds.

I can't speak for the Cyclone motors. The x5 Crystalyte motors' power output is only limited by how much you can feed into it (no one has burned one out, overheated one, or otherwise destroyed one from using too much power). You won't have multiple gearings with the motor, but that won't be an issue. You can still have multiple gears to pedal.

You need the pedals. They are your redundant propulsion and your biggest legal defense. If you choose to eschew them, I suggest you get your bike registered and licensed as a motorcycle. It'll make things a lot easier at the DMV if you say it's a "custom chopper" and don't mention the word "electric".

Your next obstacle will be batteries. You'll need in the range of 1300Wh-1700Wh to do the range you want at the speed you want. Good lithium cells like E-Moli cells are about $1/Wh. Crazy good ones are more like $1.7/Wh, and cheap Chinese ones are more like $0.70/Wh. If you're building the frame custom, you might have the option of using a truckload of SLAs. The batteries would be cheaper, but they have their own set of numerous drawbacks, the most important of which is the weight (that capacity weigh something like 100lbs Doable if you don't mind driving a tank!) If you like, we can discuss battery options more in depth.

Safety is a question with many different answers. Everyone's opinion is different. If you use a good suspension, good weight distribution, and a strong freeride or downhill-equivalent frame,from my experiences, it will feel stable. If you're building the frame custom, a longer wheelbase and shallower headtube angle will also improve stability. You need to practice good vehicular cycling and wear proper gear (at least a full-face helmet and clothes to prevent road rash!).

Please, feel free to ask any and all questions you're bound to have. And since you're wondering, yes, going that fast on a bike feel just amazing!

 

[briansrapier]

Thanks for all the great input, folks. I really appreciate the input and ideas.

As far as the laws and regulations go, I'm not terribly concerned. WV is pretty loose with the recreational vehicle laws. ATVs and Off-road motorcycles are allowed to ride on the road here providing that they have a tail/brake light and headlights at night. I was planning on going all the way and adding turn signals, mirrors, etc. Having formerly been in the bike business, I have lots of spare parts lying around and I was planning on figuring out a way to use the 10 or so LED Vistalights and incorporating them into a brake light/tail light/turn signal system. As far as a head light, I have a Nightrider cyclops, but will probably look into a dual headlight system and figure out how to tie that in as well.

I know technically that this is more of a motorcycle than a bicycle. But, the motorcycle ev technology appears to be much heavier and too overpowered for my application. I'm hoping for a bike that is under the 150 lb. mark, but I know that really depends on the batteries. I want to keep the cost down in the beginning so I'm pretty sure that I'll likely wind up using lead acid.

I still need to dig in and read up on the basics, but I'm certain I'll be in touch to ask questions.

As I get into this, I'd be happy to try to post some pics of my project.