29er Super Commuter_ Pre-Build general advice

J

JstSqzd

100 µW
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Apr 30, 2013
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Hello Everyone

So a friend and I are getting ready to pull the trigger on ordering components for a super-commuter build (we are planning to build 2 of them.) I've got some experience building a 4000w electric skateboard from scratch, and I'm ready to take it to the next level with something more practical. Plus we are both Mechanical engineers so we are always designing and improving things. Our commute is 16 miles, very little gradient change (a few short slight hills), and we want to be able to do about 40mph continuous. I'll give everyone a breakdown of what we are thinking and we would appreciate any feedback you guys can offer!

Bike: Felt Nine80 . We have a hookup who is able to get us bikes at a good discount, we want a 29er because it looks better than 26. And is bigger and more unique, Let me know if this is a dumb move. Hard tail so there is room in the triangle for batteries. Probably add a Thudbuster soon though. Mechanical discs should be easier to interface with the controller.

Motor: Here we are pretty set on going with the MXUS 3000w motor. We are looking at the 3T winding at 66v (18s lipo) To push around 55 to 65 amps. We looked at the Leafmotor because it seems to be high efficiency and a little bit lighter, but not sure how far it can be pushed.

Controller: Probably want to go with an 18fet Infineon controller to handle all that juice, but the Grinfineon looks attractive from a user friendliness standpoint (not as much power though.) And don't know much about the lyen controller.

Battery: It would be nice if we could stay at 48 or 52 volts but I don't think we can get the power/speed in this range. I think a nice compromise between building your own 18650 cell pack & buying off the shelf is to go with a lipo + BMS setup. Since the Lipo nominal battery voltage is a bit lower we are looking more like a 66.6v system rather than 72. We will likely go with 6x (10ah) 6s packs for a total capacity of 1332 wh. Looking at designing a custom hard-case since there don't seem to be many off the shelf solutions. (probably use a bag for short term)

After plugging most of this into the ebike motor calculator it looks like we will have a top speed of 41mph and a range of 15 miles. This seems perfect, as I'm sure the commute will involve a lot of slower sections to help the range. What do you guys think?
 
I suggest you try riding a bike at 40mph in traffic before you commit to that goal. Going 40MPH is a blast on a track or a bike trail, but in traffic, whoa. Going fast is easy, stopping fast is not. And you will need to stop fast or swerve. Drivers don't see bikes. They pull out from a parking space or turn right in front of you. Or they just open a door into the bike path. You just don't have time to react before you are in trouble.

I've had to lay it down several times and thank goodness I only had bent wheels and scraped skin. The faster you go, the more likely you are to mix it up with blind drivers. I say this from recent experience. Just a couple of days ago in heavy traffic a bike rider zoomed past me in the bike lane. He got about three cars ahead, then crashed into an SUV that turned into a parking lot right in front of him. The biker was in the right, but it did not matter, he flew over the hood. And somehow was only lightly injured. The biker was moving very fast, compared to the slow traffic, and the SUV driver just did not look carefully. You are invisible on a bike. Just assume that and you'll be better off. Open up to 40mph if there is no traffic, otherwise be prepared to swerve or stop and go more moderate speeds.

That said, I think your choice of controller, motor and batteries are excellent. I would opt for a mid drive (because they are about twice as efficient if you encounter inclines or headwinds -- you can shift down), but hub motors are simple and the MXUS 3000 is a good one. You've got a good design going.

Now, the rest of the story....

About the bike, appearance does not matter to me so would not affect my choice of wheel size. But on a long ride, comfort matters a lot. Really a lot. A 29er gives a much smoother ride and is a good choice. You need a steel frame with that much power, but the Felt Nine80 is aluminum. You may rip the dropouts on an aluminum frame, even with torque arms. Simple disc brakes like Avid BB7s would be very wise. Hydraulic brakes work better but need too much maintenance for a commuter.

Forget rear suspension, it takes room from mounting batteries and you don't need it on streets. I would opt for a good seat post suspension though, like a thudbuster as you said. Get a comfortable gel saddle. If you use front wheel drive, you don't want suspension forks, they squirm about under power. I would suggest you match your tires to the road surface, meaning wide if you expect traction issues. Wide tires give you a softer ride too, and after a long ride that will matter.

You really don't want a flat on a long commute. To avoid flats, use thorn resistant tubes and tube liners. I've seen quite a few flats from spoke nuts, so make sure you have very good rim tape or double wall rims. I don't like Slime, it gucks the valve, but some swear by it. Carry a little pump and tool kit just in case though. I used to be too macho for fenders, but the road oils leave a near permanent stain on the back of shirts and jackets, never mind eating it. If it rains, you will want fenders too, else you will look like a skunk when you arrive.

Lastly, make sure you have good medical insurance.
 
If you are committed to 40mph continuous I do believe rear suspension is a must. At 30mph a hard tail starts to be pretty dangerous if you hit for example a pothole in addition you will have a mxus3000 that isn't light but that's only my opinion. You could think about ebike frames like vector, Flux or the one em3ev sells since you will have quite a big battery at those speeds
 
My 2 cents, the 29er diameter is going to be harder on the motor. It will spend more time in the low rpm/high amp draw zone. I built the same type of motor into a 24", then a 26", then a 700 (same diameter as a 29er ), and it got less fun each step up. It had a nice roll, but you could feel it struggling on hills it had powered right up before, heating up more and draining the battery quicker as it did it.
Re. brakes and suspension, there are still a lot of comments about maintaining hydraulic brakes. If you get a nice modern set, it's not an issue. There's no beating the fade free, light hand pressure, and self adjusting for pad wear action of modern brakes, with the one caveat of not letting the pads wear down to nothing before replacing, but that's a user issue not a flaw.. All the mechanical ones you have to adjust constantly as the pads thin out, and almost all of them push the one moving pad at slight angle, the rotor bends over until it hits the fixed pad, and that one wears at an angle too, leading to rapid pad wear with the weight and speed of most electric bikes behind it.
Hardtail is ok on your normal bike path, but like others have said...the impacts at 40mph hemmed in by traffic and hitting potholes...yikes! As a 40mph bike owner, it just seemed like you can be more carefree with suspension and smaller wheels.
 
as someone who rode motorcycles for years, I am not scared or even worried about the 40mph on the street. Just wear your gear and you'll be ok.

however I do have other worries.
First is the motor type... 29ers are just too large of a wheel for most hub motors. You're an engineer, you understand how the ratio changes with wheel size. 29 is just too much for most motors. If you're comfortable with the electric skateboard design, I would go for a mid drive... or if you want to follow the KISS idea and go hub motor, you will want 26" or smaller wheels. That said, a massive hub motor could work of course... but it will hate hills.

Second the controller, while capable of the power, sucks from a throttle control standpoint. you let off, and theres a delay before it stops pulling. Go with one of the modern controllers. The other stuff is adaquate for the kids toys that dont go 40. Prices are coming down and options going up.. but the big daddy of course is the Adaptto. The smaller, but still 40mph capable one would be the PhaseRunner. My scooter has a PhaseRunner and it goes a tad over 40. Throttle is excellent.

Last, I know the bag sounds fun, but plan out your battery mounting first. dont halfass any of the battery....
I also run the scooter at 66v (16s LiPo, not LiFePO4)... but being an uncommon voltage, I had to build my bulk chargers and I have to charge half/half on my blance charges (8s charge one side, then 8s charge the next) IF I was to do it again, I would jump to 72v. There are more common devices at this voltage, and it simplifies things.
 
Good advice from different perspectives. One thing that struck me is how the type of roads you will travel is a big factor in suspension choice. You had said mild inclines, but paved roads. If expect a lot of potholes, that affects your choice of suspension. With severe potholes, you could bend a rim or worse, so that argues for rear suspension. But if you expect smooth roads, a rear suspension is dead weight and constrains battery placement.

If you go to a rear suspension, that affects where you put your battery. On a hardtail, it's in the triangle, so it's low and does not affect handling. With batteries on a rack in back, you'll feel more top heavy. I don't like that feeling, but sometimes there is no choice.

I looked at the specs for your motor. According to one distributor, the recommended winding of the motor you chose, MXUS 3000, for a 28.5" OD tire is the 6T. This will run slower at a given battery voltage than the 3t winding you chose, which is recommended for wheels smaller than 22".

http://kinaye-motorsports.myshopify.com/products/mxus-xf40-45h-45mm-3000w-motor
http://kinaye-motorsports.myshopify.com/products/mxus-xf40-45h-45mm-3000w-motor-6t-6kv

I really don't think the limitations of the motor should limit your choice of wheel size. A 29er is so much smoother for commuting than a 20 inch bike, easier on your butt, frankly. A smaller wheel will washboard more, and you will feel it on your long commute.

I'd go back to my suggestion of a mid drive, because it is more efficient if you have hills or headwinds. You gear down, the motor stays in its sweet spot and draws less power to cover the distance. You'll have more range from a given battery, or you can reduce battery capacity and have the same range. And the center of gravity is much lower than with a hub motor, which helps handling.

A mid drive saves life cycle cost too. Say the basic bike is $550, the motor $350, and battery $750 for the size you are talking. Batteries are a major part of the build cost of the ebike. If you can reduce cost of the battery but keep the range, that makes things easier. Batteries have limited life of 2-3 years, unlike bikes and motors. Over the life of the bike, they dominate the life cycle cost. Because a mid drive can reduce battery build and replacement cost it saves quite a lot in the life of the bike.
 
I'll go against the grain and say a 29er is awesome fun for a commuter and 35mph is easily controllable if you have good fat tires. The issue is stopping. Even on 2.2" wide road tires as your weight on a bike is so high, stopping distances got a bit hairy. With 2kw+ of power, in a slower wind for more torque, the wheel size doesnt make much of a difference. At 2.2kw I still had to watch my take offs in case I'd flip the bike going up an incline. My old ebike was pretty much a scooter for commuting.
 
Wow, thanks for the really good feedback everyone! Is good to hear the feedback about a 29er hardtail being a decent choice, since I just found out the bikes will be arriving in the next few days. (I'll post pictures!)

So to clear a few things up, we won't be riding on the open road, a majority of the ride will be on a bike path that is almost completely flat with very little elevation change (68ft over 16miles) with a few very gradual ups and downs. It is completely paved and pretty smooth, there may be a few rough patches where you might see washboarding, but no potholes. We will be slowing for rough patches or if we see the rare fellow cyclist.

Good advice on what to watch out for for running a 29er, will definitlely need some good rim tape and tube liners. I think a full triage kit is a good idea to have. And in the worst case, a phone to call an UberXL :)

As far as 3t vs. 4t. Now I am thinking that 4t would be better, especially if we make the jump up to a 72v battery. The 4T with a 72volt seems to have the power band right around 20-40mph, which is where i imagine spending most time, slowing down for cyclists & rough roads/turns, then speeding back up. My buddy and I are now debating whether or not to drop our target speed and maybe even move to a 5t, as the lower target speed will yield better range and cheaper batteries.

As for the battery, Slowhands, you said that a 66v system would be difficult to do a bulk charge, so now I am thinking that a 72 volt system might be the way to go, as we could stay with a little more reliable battery type and bulk charging is important, (I hate balance charging the lipos on my e-skate, although i do have a bunch of them sitting in my garage already.) We need to do some more research here.

Thanks for the help again everyone, I'm really excited to turn this into a build thread soon! Appreciate the feedback!
 
40 mph capability may not mean you ride 40 mph every inch of it. I certainly hope you ride much slower when sharing the bike trail with walkers or bikes.

Suspension or not. ( His bike is a hardtail) This really depends on your road surface, how the curb cutouts are made, etc. In my area, the bike trails have really crappy dips that let water cross. even at 20 mph, you get both wheels off the ground. At 15, you just bend the rim or break spokes a lot. I needed suspension just to ride that bike/walk trail at 20 mph, slower of course when the ladies and baby buggies were out.

On a racing hardtail bike, test riding in my neighborhood, I failed to notice a man hole cover. It was real exciting when the bike was standing a wheelie on the front wheel at 40 mph. Get to know your route real well at 30 mph, then let er rip. Don't let a manhole cover or pothole catch you by surprise at 40 mph with a hardtail.
 
this is mine... I'm in Perth

its a 29ER with 8T MAC and 16.5AH 29E cells from cellman / EM3EV.

totally does 60km/h , MAC weighs half what the equivalent direct drive motor weighs and
is nice and small hence easy to claim to the police that it is a 250W bike not a 2000W+ bike!

https://www.youtube.com/watch?v=3QCKEWgsP9c

BTW - MAC pretty efficient too, can do 98kms on speed 1 (30-35km/hr) with as much pedaling as i can manage
over 3hrs in the seat.

Honestly, unless you want a step change in performance up from this (STealth etc) - its VERY hard to beat this combo which is why EM3EV has sold squillions of them
 
Alright, So after digesting all of the fantastic advice. I think we are about ready to order components, we have changed directions a bit due to some better planning, budget constraints, research, and of course good advice.

Motor: We are switching to the Leaf Motor (4T with all the bells and whistles, thicker wires + temp sensor), because of its higher efficiencies, light weight, reduced costs, and it should still be able to put down power to get us to 40mph (at least momentarily) but then be really nice at slightly slower cruising speed (for battery range). Custom rim b/c our 29er rim has 32 spokes.

Controller: Mr_dude recommended the Adaptto, and after some research it seems like a big improvement over the Infineon type controllers without much additional cost. I Like the ability to add on an integrated BMS. The mini-e shows a max battery current of 65A, will this limit us to around 3kw? (at 48volts?) Is that something we should be worried about, maybe switch to the 5t so that we can add more speed through voltage and get a better torque profile?

Battery: We are going to do initial testing with 12s Lipo balanced charged (I already have these) and then either go to pre-built triangle pack, or custom LiPo build with Adaptto bMS. Lipos typically can handle the current, so that is attractive right now. Want to do testing before commiting to anything.

Our bikes were delivered Monday, so we are about ready to go. Will post pics soon.
 
As long as your voltage is not locked in the wheel size and winding turn count have no relationship based on scientific reasoning. Winding turn count is not a means of changing the gearing of a motor. It only changes the voltage you needed for identical results, and doesn't affect the power, torque, or efficiency. This is a fact based on the physics.

Proper gearing is essential to optimal performance of any electric motor, and the only way to change the gearing of any direct drive hubmotor is to change the diameter of the wheel. It turns out that typical bicycle sized wheels (26", 29", 700c, etc) result in gearing that is too steep for all DD hubbies. While you can get away with large wheels, the same hubmotor can always provide better performance in a smaller wheel. Looked at another way, a smaller diameter wheel means you can use a smaller lighter hubmotor for the same performance and efficiency. This is precisely why 0 electric motorcycles are manufactured using hubmotors in large diameter wheels, while smaller scooter size wheels are used on tens of millions of 2 wheel EVs every year.

The only exception is steady-state cruising as low and modest speeds where the reduced core losses of lower rpms with a large wheel can help you come out ahead, but acceleration and hill climbing, or even riding into a strong headwind will suffer in a large wheel. ie it means a lower fun quotient.
 
cwah said:
yes infineon belong to the past. it's adapto or this:
https://endless-sphere.com/forums/viewtopic.php?f=31&t=73448
Click to expand...
Well, the 4110 infineon does so good with the cromotor, that I am not willing to go for the Addapto until it proves better performance.
 
MadRhino said:
cwah said:
yes infineon belong to the past. it's adapto or this:
https://endless-sphere.com/forums/viewtopic.php?f=31&t=73448
Click to expand...
Well, the 4110 infineon does so good with the cromotor, that I am not willing to go for the Addapto until it proves better performance.
Click to expand...

Yeah... I'm pretty happy with my infineon... It's a cost / performance ratio. A Infineon is under $150... Everything else is $500+. My only gripe is infineon boxes are a bit fat so mounting them is tricky sometimes.
 
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