Electric Monkey 29er - project idea

[Axlezotl]

Hi, first post. I could use some feedback for a possible e-bike conversion project. This would be my first, but I've been studying up on it (mostly by reading here). I have a Surly Karate Monkey that I've been using for a townie/trail bike. The build ended up being heavier than I was expecting. Those big tires are heavy, plus the other stuff like butterfly bars, rack, annd sprung seat add up. I might get another, lighter bike this summer for leg-powered exercise and trail riding. That idea started me thinking about motorizing the Monkey as a short haul bike for shopping in my small town.

My house is up on a hill and there's a grocery and hardware store down on the flats, just a mile away. I think it's about a half mile of 5% or 6% grade for the hill section. I can't use the bike for this now, because I'm an older guy with bad knees, and pedaling a bike with panniers loaded with groceries up that hill is just too daunting. There is also a nice state park 2 miles away, with a very short stretch of 15% grade climb on the way home. I have to walk the bike on that section now, and I could probably pedal it with enough assist. I don't want an e-bike that works like a throttle-and-go motorcycle, just some help on the hills, and (hopefully) low rolling resistance so I can pedal most of the rest of the way.

I'm thinking maybe a geared front hub motor for this project, although I'm open to other suggestions.

I would like to keep the big tires (2" Big Apples) for the shock absorbing and easy rollover on bumps and pot holes. Will a pre-built front hub motor kit have rims wide enough for these tires? Am I looking at a custom wheel laced around a motor? I would need a kit where I could keep the front disc brake.

There are some other ideas I'm mulling over, like getting a cargo bike for the donor so I could carry larger, odd-sized stuff home from the hardware store. The Monkey would be limited to what could fit on the rear rack; probably grocery panniers with the battery in a waterproof case on top of the rack. I thought I'd float the idea of using the Karate Monkey first, since I already have it. Also the name "Electric Monkey" would be cool.

Thanks in advance for any feedback!

 

[FeralDog]

Nice bike. IMHO, perfect for what you need.
Hard to find a better bike for your specifications!! Spend ALL your money e-biking that Surly rig. You will not need another bike, your knees will thank you.
Most of the things you list as negative for a pedaller , will benefit that bike with electric assist power. I haven't any experience with the butterfly bars (thus no comment on the brakes and throttle set-up) , but I prefer a more pulled-back Townie or Beach Cruiser feel on my bars.

If your front forks are the 80mm 4130 Surly Chro-moly, then you are really in luck , your dropouts look good, but still get 1 (or better 2) torque arms for extra strength..

Yep.
Geared front hub w/disc brakes , big (or even Fat Frank tires 29X2 HS375's (or if smaller rim 26X2.35), double walled rim w/12 g spokes {but are your KM Surly tires the 29 (Two Niners??)--- that may limit some choices in pre-assembled wheel kits}
Your pic looks like your tires might be 26", but your title says 29er: sometimes Surly's are custom-ed below their 29X2.6" specs so I cant tell for sure?
{EDIT: your disc brake set-up looks like it may allow for a 69er, 26" Front, 29er Rear, and thus may increase the choice in available e-kits}


Schwalbe has a guide to fat tires and rim widths >>> http://www.schwalbetires.com/tech_info/tire_dimensions.
Maybe you could also use the Wald folding rear basket over your existing rack, clip-on Wald front basket to help carry/balance your loads> >> http://www.waldsports.com/index.cfm.
Finally, perhaps buy the best battery your budget can afford. Maybe 48 volts if you can afford it too. I

Others will certainly have another perspective, but I sure wish I had a bike like that to start e-biking. I have been looking at that Karate Monkey and debating it over the Surly Pugsly

 

[dogman dan]

The less expensive kits come with a rim that will likely be lower quality than your current one. So get another identical rim and have a motor laced into it. Looks like a good bike to turn into a grocery getter. A 350 watt gearmotor will give you a nice assist up the 7% hill, but slowly. Higher wattage gearmotors, like a bmc 600 watt will get up it better, and have a chance on the 15% grade.

But don't entirely rule out direct drive. I have really enjoyed my 9 contininent motor. On 48v, it will simply fly up 6% at about 20 mph. The steepest grade I've climbed on it is 13% but it did get up it. Hopefully the steep hill is pretty short.

The bike just needs a nice strong designed for panniers rack. Wish I had a surly!

 

[Lock]

I don't want an e-bike that works like a throttle-and-go motorcycle...

Free your mind. There is no harm in this.
Tks
Lock

 

[Drunkskunk]

Welcome to the forum.

Nice bike. It should convert well.

You're going to find that your spesifacation for a front motor with disk brakes and able to climb 15% grade hills limits your choices. Those choices that are left are a bit expensive, but something like this: http://www.cycle9.com/c9store/clear...t-p-80?zenid=29d4c6eeaaeb0d8581da96b3d3fcab50 would work.
Thats the 400 watt version. A 600 watt version might be required if you're heavy set and/or plan to carry a good deal of weight

As you're probaly aware, a 29 inch wheel is really a 700c rim. while the race bikes do use a narrow 700c rim, you won't find those used on eBike motors from a reputable dealer. A eBike motor sold as a 700c should be fine.
My first Ebike, and my third are 29". the 700c rims supplied whith the 2 motors I got were fine for use with 29" tires

 

[Axlezotl]

Thanks everyone for the great feedback!

Your pic looks like your tires might be 26", but your title says 29er: sometimes Surly's are custom-ed below their 29X2.6" specs so I cant tell for sure?

Yup, it's the big 29" (700c fat tire) setup.

{EDIT: your disc brake set-up looks like it may allow for a 69er, 26" Front, 29er Rear, and thus may increase the choice in available e-kits.

I thought about downsizing to 26" front and rear for a stronger wheel, and that would slightly lower the center of gravity, which would probably be a good thing for a heavier bike with motor and battery. But that would give up the big wheel/tire advantage, which is basically a substitute for front/rear suspension. Well, front suspension anyway; the more heavily loaded rear tire still feels the bumps.

Finally, perhaps buy the best battery your budget can afford. Maybe 48 volts if you can afford it too. I find 36V A-OK, but seems everyone wants more, more, more! Forum folks will debate your Volts/Chemistry/Amp-hours with expert logic far beyond my limited newbie range ... :lol:

Hah! Yeah, it seems there's a never-ending upward spiral in what's desired here, as you learn more about this stuff. I'll spring for a good battery type, but I'm aiming to keep the volts down to just what I "need" for the first build. I'm still working the numbers for power/range/battery weight and I'm sure I'll have more questions about this.

The less expensive kits come with a rim that will likely be lower quality than your current one. So get another identical rim and have a motor laced into it. Looks like a good bike to turn into a grocery getter. A 350 watt gearmotor will give you a nice assist up the 7% hill, but slowly. Higher wattage gearmotors, like a bmc 600 watt will get up it better, and have a chance on the 15% grade.

But don't entirely rule out direct drive. I have really enjoyed my 9 contininent motor. On 48v, it will simply fly up 6% at about 20 mph. The steepest grade I've climbed on it is 13% but it did get up it. Hopefully the steep hill is pretty short.

Thanks for the info on the rim. Yeah, I guess a custom wheel would be good. For the motor, and based on reading threads here, I was thinking maybe the BMC V2 high torque? Also, I don't want to over-emphasize that 15% grade, that's just a very short stretch and I can find other routes. Most of the hills around here are more like 1/2 mile of 5%. Steep climbs like that 15% are rare, or very short distance.

I'll take another look at direct drive too (I bookmarked a few forum threads about that here). I was thinking geared for the smaller stealth look and for the freewheel... low resistance for pedaling? But maybe that's not so important with this build.

I don't want an e-bike that works like a throttle-and-go motorcycle...

Free your mind. There is no harm in this.

Sure, no disrespect intended to the full electric transport folks. Every time I take a bike of any kind out of the house though, I'm looking for some exercise as well as transportation. I'm aiming to strike a balance between pedaling and assist just where I really need it.

 

[Lock]

I don't want an e-bike that works like a throttle-and-go motorcycle...

Free your mind. There is no harm in this.

Sure, no disrespect intended to the full electric transport folks. Every time I take a bike of any kind out of the house though, I'm looking for some exercise as well as transportation. I'm aiming to strike a balance between pedaling and assist just where I really need it.

Didn't think respect was anything to do with this... I only wish to have a "proper" human-electric hybrid myself... I am only familiar with power-assist on foot bikes aka adult kick scooters. I *like* to kick, for the exercise, to extend distances on a charge, and it just turns out to be part of a natural(?) mix between motoring and coasting and walking that the stand-up scooter design promotes.
When Transport Canada studied power-assisted pedal bikes, from the feedback they got from participants in their study they concluded that there was no safety advantage to pedal-assist only... that an accelerator under separate control was just as safe, and the participants had noted that many of them actually preferred this option. So TC had been thinking pedal-assist only in their draft legislation, but backed off at the last minute and left this question of control as a choice.
So I don't know if you have tried both approaches. I only suggest that you consider a power-assist package that lets you switch between these two modes so you can try the difference! EVen with the motor under accelerator-only control, ya can still pedal all you want to, assuming your pedal gearing can keep up w/the motor speeds...
Cheers
Lock