Please recommend Front Hub motor for Off-road Fat bike build

[rdhfreethought]

Long time lurker here. I have 2-3 projects on the mind and am a novice on ebike side of things (I race XC/Enduro/DH on my HPV bikes). The first project will be a 2WD FS Fat bike that can be used in the snow. There are only a few Fat bike FS forks on the market and only one will work with a front hub motor (to my knowledge). What I am looking for is a drop in Front Hub motor that is 250W-500W (maybe more), lightweight, water-resistant, disc brake compatible (prefer 180mm+). Initially, it will be used to make un-ridable conditions ridable. If it is just rainy or muddy, I will ride one of my other HPV bikes (I currently have 4 other MTB, and 3 spare frames to choose from). This will be for snow mostly, and will be on backcountry trails. I expect I will be using 'burst power' for most riding, but there is the chance of a long powerline climb in the snow as well. Although, I would love for speeds to be fast, in all likelihood, I would be climbing at 3-10mph.

Although I am not afraid of technical challenges, since this my first eBIKE, it makes sense to start simple and go up from there. (project 2 will be a high speed 35mph commuter)

Cost is not that much of an issue, I just don't want to waste money.

All fabricated parts will be made by a local machine shop, or homemade using composites.

Fork: Maverick DUC32
RIM: Kris Holm Freeride 47mm (likely converted to tubeless)
Tire: Surly Nate 3.8
Hub motor: ??
LiFePO4: ??
Controller: ??
Throttle: ??
Charger: ??

Specific questions:
-I would like the ability to increase volts as needed. So a controller that can handle the upshift from 24v-->36v> 48> 60v would be nice. This would allow me to change things if I find I need more range (increased WH and volts) or more power if hill climbing in the snow is too difficult.
-Since I am new to eBike, recommendation of favorite distributers would be nice (or local to Seattle, WA).

Thanks in advance!

 

[wheelbender6]

The idea of 2WD has always been attractive to me too. Front hub motors over 250w are not recommended for your typical mountain bike suspension fork. With a rigid steel fork, you can use a much more powerful motor. 500w motors from Ampedbikes.com and e-bikekit.com usually get good reviews. Samsung and Hill Topper sell 250w front hub motors.

 

[Drunkskunk]

Sounds like a fun project.

The most imediate problem is the fork. A fat tire isn't going to fit. you need 110-125mm clearance between the stantions minimum. That tire will be 90-110mm wide depending on the rim, and that fork is only about 90mm wide at the top.

Unfortunatly, there are no production forks for fat bikes at this time. Risse Racing makes a special hub and fork tree to modify their fork to hold a fat tire, but they wanted serious $$$ to make one for me. Old Marzocchi Monsters and Super Monsters will hold one, but they have been out of production for a decade, so you'll need a used one. I tried both, and I'm running a Supermonster right now.

And then you run into the problem of mounting a motor to a through-axle fork. Basicly, you can't. Not without machining your own design motor axle and custom mounts.

But making this work for a non suspension fork is easy. Find any 135mm fork, which most fat tire forks are, and mount a rear motor in it. I'd recomend the 12t MAC. Its a 500watt that should be able to power the weight of that front wheel well.

 

[rdhfreethought]

Thanks for the reply!

Not impressed with ampedbikes. $1021USD for a 350W kit with what appears to be poor quality. (sketchy brakes and cheesy waterbottle battery)

ebikekit has a much better website. Not much real data, and huge markups @1300USD

I am thinking grabbing a Bafang from BMSbattery for ~$100

hoping for a few more comments.

Basically, I am thinking a geared motor is the way to go (motor used mostly for climbing), and since it will be on the front, best limited to 500W, but I would like total weight to be 5-6 pounds, which if run at 48v should be feasible

 

[rdhfreethought]

Sounds like a fun project.

The most imediate problem is the fork. A fat tire isn't going to fit. you need 110-125mm clearance between the stantions minimum. That tire will be 90-110mm wide depending on the rim, and that fork is only about 90mm wide at the top.

Unfortunatly, there are no production forks for fat bikes at this time. Risse Racing makes a special hub and fork tree to modify their fork to hold a fat tire, but they wanted serious $$$ to make one for me. Old Marzocchi Monsters and Super Monsters will hold one, but they have been out of production for a decade, so you'll need a used one. I tried both, and I'm running a Supermonster right now.

And then you run into the problem of mounting a motor to a through-axle fork. Basicly, you can't. Not without machining your own design motor axle and custom mounts.

But making this work for a non suspension fork is easy. Find any 135mm fork, which most fat tire forks are, and mount a rear motor in it. I'd recomend the 12t MAC. Its a 500watt that should be able to power the weight of that front wheel well.

Thanks for the recommendation. They make a standard front hub version as well...

Regarding your points:

According to this thread, if you shave the side knobs you get little, if any rubbing: http://forums.mtbr.com/fat-bikes/duc32-my-pugs-good-bad-news-756114.html

Several forks are available that fit fat tires:
1. Marzocchi Shiver
2. Manitou Dorado
3. DVO Emerald http://www.pinkbike.com/news/dvo-emerald-first-look-2012.html
4. Maverick DUC32
5. Maverick SC32
6. Muru Cyles http://fat-bike.com/2013/07/muru-cycles-swale-o-suspension-fork/

-There is also a prototype FOX fork http://www.pinkbike.com/news/fox-dh-fork-inverted-prototype-2012.html


Lets assume, for the sake of argument, that I solved the problems with using the DUC32 for a front hub motor and a fat tire.
Which (standard) front hub would you use? Light weight, flexibility, and <500W being criteria.

 

[rdhfreethought]

Regarding the thru axle. Aye, I am aware of that. Which is why I chose the DUC32. It is NOT and thru axle, and uses 24mm, instead of 9mm, 15mm, or even 20mm diameter axle. Therefore torque is less of an issue. And that is what titanium, Kevlar and carbon fiber are for (i.e. breaking through perceived barriers).

I know bike components fairly well, I just don't know motors and stuff! (though I was engineering and physics in college, that was 20 years ago and I haven't touched it since)

 

[t3sla]

The Bafang BPM sounds like an ideal fit for your requirements.

250W-500W (maybe more), lightweight, water-resistant, disc brake compatible (prefer 180mm+).

A Programmable controller would allow you to change voltages easily, PM Lyen (he has good customer support)
http://endless-sphere.com/forums/memberlist.php?mode=viewprofile&u=1370

What are you thinking for battery mounting options?
Considering the terrain the bike is built for something tough and water resistant would be ideal

 

[rdhfreethought]

Thanks T3sla.

Battery box will be a carbon/kevlar/hex core sandwich. It's really the best material possible. Strongest, lightest, fireproof and chemical proof. Easy, if messy, to manufacture. Location to be determined, based on the size of the controller. But, almost definitely somewhere on the frame, hopefully low slung and sandwiched on the sides. Controller would fit on top.

 

[dogman dan]

First of all, you are dead wrong about wanting a front hub. Only if you will run double motors do you want a front hub for off road riding, whether wet or dry. It will just spin mostly, when you do steep inclines and all your weight shifts to the rear wheel.

On the flat, front drive in the snow can be fun, but I'd still prefer sliding a rear tire to the front. What front drive is lovely for is dry pavement. I built a front drive bike that did 47 mph, so I'm not spouting what I read here, but what I did. I have about 8000 front hub miles.

What you want is the slowest motor you can get. I recommend a rear hub direct drive motor, because they can tolerate higher wattages. Particularly in winter, the cheap dd motors can take 72v 40 amps controllers. Bigger more expensive ones tolerate even more. But the cheap motor on 3000w will do LOT, if you pick the slow winding version.

Go to EM3ev, and select their rear direct drive motor in the slowest RPM they have. It will do 30 mph when you run it on 72v. It will climb up to about 15 degrees. Degrees, not percent!!! It will tolerate 5mph climbing for a few min, and 10 mph climbing for long periods. Most hills up to 15% will go at about 15 mph with no or only very little pedaling.

Been riding this kind of setup off road for years now, and if you can keep speed 10-15 mph, you don't melt the motor. REALLY fun on the snow rides.

http://www.youtube.com/watch?v=O76al_1ZMTg

See some of my other vids to get an idea what you can expect to climb.