Your ultimate downhill (uphill) design for me please :)

[MachineShopDave]

Hi All!

This is my first post, Dave from CT-USA, and I have to say THANK YOU so much for all the helpful threads I have been reading, I am so excited to communicate with the friendliest, brightest folks I have ever seen on any forum I frequent!

I think I know what I am going to build, but choosing products is the hard part. So I am going to post my desires, and I would like to get your take on what battery, motor, controller, and DH bike you would use.

I am going to pull the trigger on ordering everything this month (unless it is worth waiting for a new product) and have this bike on the road for Christmas! I own a job shop so I can fabricate anything required, that is no problem, but off the shelf parts are preferred.

That being said, if anyone needs some parts made up or modified, I would not mind helping you out with a good price, but I will not be competing with your other manufacturers on the board.

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Desires:

Electric dirtbike for hill terrain and to commute 25 miles or more. Would like 1hr of charge capacity under heavy riding, unconcerned with recharge time. Would like very, very torquey, top speed 35-50mph. Operate in 30 degF or above. Prefer closest to standard DH bike look as possible, narrow, weight less than 120 lbs. Keep total cost (materials only) $3-5000.


Bike:

Downhill with 6" plus travel full suspension. Must fit batts in triangle. Used model, 18-20" frame.
I am thinking the Giant DH Comp is highly regarded for this.

Hub Motor:

Would like A LOT of torque for rear 26" wheel. 72-96V system voltage.
Crystalyte X5*** or Crown? This is where I need the most help. I want robustness.

Batteries:

I would like to assemble cells to fit custom box in triangle, can extend above and below if required. The best batteries are preferred, I am thinking Sony V3 18650's. Zippy's are OK too, but I think with the cells I can fit more in the triangle. Batteries will be my biggest expense, I want A LOT of capacity.

Controller:

High amp capacity WITH regen, cheaper quality is OK. Would like the fancy display screen. Would like to monitor core battery and motor temp.

Charger:

The best I can get to increase battery longevity.

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I promise to keep this thread going with photos and updates and videos, this has been my dream toy and I finally obtained the spare capital to begin and complete this project!

What am I missing???

MachineShopDave

 

[Willow]

Stealth Bomber for you.

http://stealthelectricbikes.com.au/bomber.html

 

[MachineShopDave]

Thanks for the link, yes they do make good stuff, but I make better. :wink:

 

[AussieJester]

If you have the ability to fabricate and want a decent performing off-road bike, forget hub motor in wheel
Go for mid drive...jm2cw

KiM

 

[dogman dan]

Good thing you don't want much. You do pretty much want to duplicate a stealth bomber. By that I mean, a small motor like a clyte HT won't cut it. Not for a full hour duration of that hard of riding. I agree, if you really want up the hill performance, without the heavy rear hubmotor, It's mid drive for the win. Nothing beats being able to gear down.

I still wonder how people manage to carry enough battery for a full hour of riding that hard. But the best approach for that has got to be one or another of the new frames coming available now. Such as the one from the cromotor folks, or the new one coming soon from High Power Cycles looks pretty nice too.

Personally, I still like my stealth fighter like approach. Smaller cheaper, very slow rpm motor, 10 pounds less wheel weight is the main benefit. Run them on 72v 40 amps, and you still climb 15% grades with no problems. Riding for an hour in the dirt is possible, but you might still melt a motor if it's summer. Hell, if I am riding dirt that tough, I want to stop to rest before the motor does. So I just carry 700wh of battery, and take a second 30-40 min ride later if I need more. Riding duration is not a problem on street, drawing only 20 amps or less at 30 mph. Commute faster and the cops will look at you.

But this setup won't climb that wall to the mine. Or that horse pack trail. Lots of mine roads in the rocky mountains gas dirt bikes can do, but my bike will melt trying to climb 20 degrees for a mile or two.

But it eats trails built for mountain bikes for breakfast. Those mine roads and horse trails suck anyway. Too rough and rocky to ride. A few miles and all kinds of parts shake off the bike.

 

[MadRhino]

Ultimate can only be specific for the terrain that you ride. It will be the best on your terrain if you build and tune it right, but could be far behind on another terrain. 1h of hard riding in the mountain can require a lot of battery capacity, making your bike heavy and bulky. Downhill is another story, you need to be light weight to perform, so long range doesn't live well with DH ability.

Theory says a mid drive is best for the mountain, but reality speaks otherwise at many places. The ability to accelerate to a fast top speed without any shifting is an important advantage, so a mountain trail that is within hub motor capacity can be ridden much faster with a hub build. All my trails are less than 10 miles, they have a great variety of obstacles and a wide range of attainable speed . Playing constantly between slow and very fast sections, a mid drive is not able to keep up with a powerful hub build. By the time you can shift up the hill, I'm gone.

 

[Drunkskunk]

Welcome to the forum. Your budget will cover about half of what you need. What you described is something the Stealth Bomber can almost do, but would be better achieved by a Zero Motorcycle.

As for battery, you're going to need huge. I can tear through nearly 1000 watts in 10 miles riding texas style singletrack at near bicycle speeds. If you want to go faster and farther, you're going to need a lot more battery.

 

[spinningmagnets]

From reading others posts, I am of the impression that a rear hubs main benefit is ease of installation, and quiet operation. If you had flattish terrain and a low top speed, you really can't beat the dogman formula. Low-kV hub at higher volts. Modest speeds, runs quietly, no need for frequent shifting (like a mid-drive), very simple and reliable.

You mention hills, high speeds, and long range. All three are addressed by a mid-drive, at the cost of more audible noise, and the need to shift the gears to get the benefits.

Mid-drive will help your battery range, because a high-speed hub will draw high amps during acceleration. Hubs also draw higher amps on hills, compared to mid-drive because shifting keeps the motor RPMs up. High speed with a hub means a "speed" winding (bad on hills) or very high volts...or both.

One option for a mid-drive is a GNG-based LightningRods kit @72V (see Chisterljungs no-pedal build), on a full-suspension frame with a custom battery box like Rodgahs Big-Hit:

http://www.electricbike.com/big-hit-fsr/

 

[dogman dan]

Bear in mind though, mid drive may or may not run through the bikes normal gear.

So you might want to go one gear mid drive, but tune it by using the right gear for your terrain. Much like you tune a hubmotor bike with the choice of motor, and wheel size.

You'd then at least lose the weight of the hubmotor on the wheel, and have, er, a Zero Motorcycle. And to perform like a Zero, very likely spend more than your current budget.

It's the ol dilemma, want three but only two of the three is easy. I think it's a no brainer to lose the ride for a full hour first, for the reasons stated by Mad Rhino above. The rest can be done relatively easy, once you slash the battery weight back to an easier to carry size.

 

[speedmd]

MadRhino brings in some good points. Slow shifting and not equal motor availability. Mid drives, have some catching up to do. Wonder how electronic shifting tied into the controller for a brief softening (slightly backing off power for a quick smooth shift) would be. F1 style. Lots of real nice motors coming to market also, and I see the dominance of the big hubbies most certainly will be significantly challenged in the near future. There is not much to choose from in motors at the moment for a mid- high powered mid drive.