First Build Noobie Questions

[BuckGup]

Hello, I am looking to build my first proper eBike. Last year I built a 1500w eBike with a specialized hard rock as the frame with some random 72v controller I found on eBay. I was able to hit speeds in the 45-50mph which is bit sketch with a mountain bike frame. I have a general idea of what I want but some questions on what's the go to right now on the market.

Speed controller: I'm looking for something that has a manual written in english, I can adjust the throttle curve, and supports regen braking. Looking for a 72v controller and 200A if the motor below will draw in that range.

Motor: I've been looking at the QS 273 50H V3 8Kw motor. I'm trying to aim for speeds around 60mph.

Frame: The bomber clones are nice as they are easy to find now but I hate the look and they are so common. I know someone local who can weld me a frame to my liking so I might go for a more tradition cafe racer type look and diy it.

Front Fork: I'm not sure on the travel for this and if I should go with a dirt bike fork, moped, or downhill mountain bike.

Brakes: Looking for large disk brakes that are hydraulic. On my previous build I had small disk brakes but they would start smoking like crazy on a full stop from max speed. The stopping distance was also terrible and sketchy. Also brakes that support regen. Not sure if this is just controller dependent with micro switches in the handle bars or if I need different calipers on the brakes themselves.

Battery: Ideally I want a range of around 40 miles so I was looking at a 72v 30Ah pack but I'm not sure how realistic that is with a 8kw motor. I'm willing to drop to a 6kw or 5kw motor if I can get speeds around 50mph but the range would lengthen significantly.

Wheels/Tires: I don't know if the QS motor comes prethreaded into rims, I don't think it does, so I'm not sure on the size. A larger tire will give me more speed but be weaker and I'm not sure on the cost difference. I know most are in the 19", 21", and 17" sizes as this is what mopeds and motorcycles use. Which on that note I'd like to use motorcycle or moped rims/tires as bike components are way too sketch at high speeds and now with more weight no way.

Misc. I'd like a windshield and headlight like the ONYX bike has. Not sure what you would search to find this. As well as some brake lights. Also looking for a decent twist throttle with a kill switch and maybe a 3 position rocker switch to select different modes if that's possible with the controller.

Other than that let me know of anything I forgot. The main goal of this build is a safer yet still fast version of my first build. Thanks

 

[amberwolf]

Speed controller: I'm looking for something that has a manual written in english, I can adjust the throttle curve, and supports regen braking. Looking for a 72v controller and 200A if the motor below will draw in that range.

Requiring an English manual greatly restricts your choices.

The Lebowski brain board can do what you want, and has English documentation and even setup videos, but it is a DIY controller you would have to build yourself. The brain board can be bought premade, but it then must be connected to a powerstage. ATM I don't think anyone is selling a complete powerstage you can just plug it into, though there are a number of threads with ones you can build, and at least one thread in progress on using the powerstage out of an EV (whcih I'm doing for my trike), wchih when complete will let anyone just wire one up per the directions and go (but isnt' there yet).

Otherwise the closest thing I know of to that is the Phaserunner by Grin Tech. It's based on the ASI BAC series, but AFAIK has more complete documentation, and better support..but it wont' do the power level you're after, and I don't think you can get the speed you want.

Sevcon would be the next closest, in that you can definitely get the power, but you'll probably spend as much on the programming stuff as on the controller, and from my reading here and elsewhere will need quite a lot of time and learning and possibly paying someone to help, to program it for your specific motor/system (without which it is useless).

I don't know of anything else for sure that has good documentation in English, though stuff like the Nucular and Powervelocity stuff in the for sale section might--you'd have to check in those sale threads. The various higher-power VESC units may, but I don't know--you'd have to look them up and check.

Brakes: Looking for large disk brakes that are hydraulic. On my previous build I had small disk brakes but they would start smoking like crazy on a full stop from max speed. The stopping distance was also terrible and sketchy.

If you're looking for 50MPH, then any motorcycle brakes that fit your motorcycle frame and fork should be capable of this. If you're using a bicycle frame...I don't know how to make that a "safe" ride, as they're not designed for that kind of thing, with the extra weight of the motor, battery, etc.

You could build using motorcycle wheels, which will help with the wheels surviving unavoidable hits at that speed, with motrocycle tires that are designed for that speed. Some of the DH suspensions may be able to help, too, but I don't know how effective they would be--you'd have to check out other build threads similar to your own intent to see how well they lasted under the conditions you have.

Battery: Ideally I want a range of around 40 miles so I was looking at a 72v 30Ah pack but I'm not sure how realistic that is with a 8kw motor. I'm willing to drop to a 6kw or 5kw motor if I can get speeds around 50mph but the range would lengthen significantly.

It doesn't matter how big your motor is. Its about how much power it takes to go a certain speed.

50mph is likely to take over 100wh/mile, even 150wh/mile, depending on conditions, aero, etc. So 40 miles could require 4000-6000wh battery, minimum (not allowing for detours, headwinds, pack aging, etc., whcih I'd recommend adding at least 20-25% of that capacity to cover).

For a 72v pack, that's 6000 / 72 = 83.4Ah. That is a huge battery. I have a 52v 40Ah battery that is at least 35lbs, bare, no casing, and the size of a stack of books. That's about 2kwh. Yours would be at least three times that size, so about 100lbs and the size of a small human torso.

If you only ended up needing 4kwh, that's still around 70lbs, and still huge.

Not sure how you're going to fit this without using a motorcycle frame, or making compartments around the bike that each hold part of the battery and wiring between them, to help with weight distribution and try not to mess up handling.

 

[BuckGup]

*snip

Alright so I guess I should have more reasonable expectations for the battery. I saw someone on here made the ONYX bike hit 122 miles but I think they kept it under 30mph. As for the the speed controller it isn't a die hard requirement to be in english. I'm fine using a translation if that doesn't limit my options as much. What kind of speeds would a 6kw motor get you? Also if you know what are some average ranges from higher performance bikes on here? Thanks

 

[amberwolf]

For ranges, you should look at the various "watts at speed" type threads, whcih will help you see what kind of wh/mile usage needed to maintian various speeds. Or use the http://ebikes.ca/simulator to "build" various bikes and see what their estimated usage is at different speeds and terrain/wind conditions.

As noted before, power usage isn't really about the bike, it's about the speed. Aero comes into play more the faster you go, so low-air-resistance designs like velomobiles, fully-faired bikes, "vetter" motorcycles, etc., will use a lot less power for the same speed.

But for a typical upright bike or motorcycle, speed eats power, and you're stuck with that.

Weight and acceleration also eat power, but at speeds above 20MPH the aero can make more of a difference, depending on riding style/conditions.

For instance, my CrazyBike2 could get by with as little as 22wh/mile for 20MPH, on long rides with few stops. But it went up to 30wh/mile for short trips with many stops, yet because it's heavy, accelration from the stops each time would eat so much power it brougth up the usage despite the average speed being much lower.

My SB Cruiser trike is close to 60wh/mile under the same conditions, becuase it is so very unaerodynamic (big box cargo trike with canopy that acts like a parachute, but keeps me from melting in the sun). The aero is so bad that you can't really tell the difference between the short/many-stops trips and the long/few-stops ones, for power usage.

 

[Drunkskunk]

Your goals are a great description of a motorcycle. And to make it work, stop thinking Bicycle and start thinking electric motorcycle. it's the only way you would achieve them reasonable. anything less would end in the ER. Just to support the weight of the battery, and the frame to hold it's weight, and the suspension to hold up the frame and battery and yourself, and he heavy arsed motor needed to push that thing, you would need motorcycle rims, tires, and brakes.

the ONYX designs are a rough copy of popular mopeds from the 70s designed to go 30mph, but sketchy as all hell at even that speed. I was into mopeds before building ebikes, and physics are not on their side at high speeds, even at 30. the wheel base is too short, the center of gravity too low, the steering angle is all wrong, tires too small for effective grip while braking, etc, etc, etc. You don't want to copy that for a 60mph bike.

For an ebike, 20mph takes about 350-400watts of power to maintain speed on flat ground with no headwind. 30mph takes around 1000w. 40mph takes around 2300 watts. 50mph takes 4500 watts. 55mph takes 6000 watts. 60 takes around 8000 watts. So you can see, the faster you go, the more power you need. You said 40 miles range at 50mph. that would draw 4500 watts for 48 minutes, so use around 4000 watt hours of battery, about fully draining a 72v 60Ah battery. And if you had some stop signs, hills, or a headwind, it wouldn't make it.

So you need to consider which of 2 kinds of ebikes you really want here: The kind you build just to see how fast you can go, or the kind you build to see how far you can go? A 40mile range bike is going to be massively different from a 50mph bike.
Unless you are going to build a motorcycle.

 

[Balmorhea]

Aero comes into play more the faster you go, so low-air-resistance designs like velomobiles, fully-faired bikes, "vetter" motorcycles, etc., will use a lot less power for the same speed.

Many motorcycle touring fairings-- and I think the Vetter Windjammer is one of them-- manage to have more aero drag than an unfaired bike (Cd higher than 1). They accomplish this by making a disrupted "hole" in the air that's substantially bigger than the frontal area of the bike.

 

[ScooterMan101]

What will he charge to weld / fabricate a Frame for you , and what material will you use ? ( PM me if you / he does not want to get inundated with many others wanting to make a frame as well. )

I want a custom frame my self as the bomber clone , sheet metal frames need allot of improvements .

I can help you with design ideas on a private message ( PM )

For Brakes , the newer model 4 piston brakes that Down Hill Riders use will be good enough , as long as you use 203 mm rotors and for higher speeds get the Shimano IceTec Rotors .

For your fork : Fox 40 , Rockshox Boxxer , and others Like the RST Killah and others that use a 20 mm x 110 mm through axle .

For aerodynamic's , look into what the 2 wheel recumbent riders use for their fairings .

Frame: The bomber clones are nice as they are easy to find now but I hate the look and they are so common. I know someone local who can weld me a frame to my liking so I might go for a more tradition cafe racer type look and diy it.

Front Fork: I'm not sure on the travel for this and if I should go with a dirt bike fork, moped, or downhill mountain bike.

Brakes: Looking for large disk brakes that are hydraulic. On my previous build I had small disk brakes but they would start smoking like crazy on a full stop from max speed. The stopping distance was also terrible and sketchy. Also brakes that support regen. Not sure if this is just controller dependent with micro switches in the handle bars or if I need different calipers on the brakes themselves.


Other than that let me know of anything I forgot.