E-Kit for My Needs - Questions

[alienbogey]

First, let me apologize for making my first post full of questions, some of which are probably stupid, but I've been reading FAQ's, threads, and posts here and elsewhere until my eyes are bleeding. I'll describe my situation, wants, and bike, then I'll try to make my questions as intelligent as I can.

I'm in my early 50's, weigh 210, I'm fairly fit, and I ride my bike for pleasure, errands, and exercise. I have a "10 mile knee" which is more accurate than my bike app's GPS. At 10 miles the knee starts complaining, and 40 miles nearly puts me on crutches. The knee is most annoyed by high torque (hills), and our area is pretty hilly, so my primary e-bike kit desire is hill assist. I'm hoping that with a motor pushing on my back up hills I could do longer rides again.

I still want it to feel like an unfettered bike ride, though—freewheeling pedals when coasting, zero or minimal motor resistance when not engaged, etc. I want to be pedaling most of the time, I'm not worried about top speed gains, and I'm not interested in turning the bike into a motorcycle (been there, done that, can show the scars).

My bike is a 2011 Specialized Crosstrail Sport with aluminum frame and front fork, front suspension, hydraulic disc brakes, 700cc wheels, and 8 cog rear/3 cog front:



I like the bike a lot, as you can see I've accessorized it to my tastes (it has panniers now, too), and I don't wish to go to another bike. I run errands with it, occasionally filling the bags with a fair amount of weight, and I have a trailer I occasionally pull to the grocery store.

Based on my research, here are my thoughts/questions regarding rear hub motor vs. front hub vs. crank:

Rear Hub Motor

This is my third choice, mainly for reasons of weight and balance.

When I load my trunk bag and panniers the bike's c.g. is shifted way aft and it definitely affects handling, especially at higher speeds. I'm probably unduly sensitive to that because of a motorcycle lay-down long ago caused largely by too much crap on the back of the bike. Basically, the thought of even more weight at the back and decreased front end stability/traction gives me the whillies.

Front Hub Motor

This was my first choice until I read many threads cautioning against front hub motors and aluminum forks, which my bike has. Questions regarding this:

• Some say that lower-powered front hubs, say 250W, should be safe with aluminum forks. Agree/disagree?

• Would anyone recommend a lower power limit, or higher limit, or simply say no hub motor should be installed on aluminum forks regardless?

• Some say that front suspension forks are built stronger than non-suspension forks. (This makes me feel better about my bike.) Agree/disagree?

• Some say torque bars are necessary, some don't. Regardless, I would put torque bars on both sides of the front. (Once can never have too much overkill, and I'm not worried about weight.) Agree/disagree?

Crank Motor

After reading lots of threads about various crank drives, I came across the Bafang BBS01 on http://endless-sphere.com/forums/viewtopic.php?f=28&t=50104, and it looks like it might fit the bill.

For this specific crank drive, can you only have one front cog?

If so, it's likely a deal breaker for me. My area is hilly, and I shift through all 24 speeds of the bike multiple times in every ride. I would hate to give up my three-speed front derailleur.

• Can this particular crank drive be used with three front cogs?

• If not, is there a crank drive that can?

Final Thoughts

• I'd like to keep the total cost to $1000 US, but could go more if necessary for quality & satisfaction. My actual cost will double, though, because once I get it figured out and installed on my bike, I'm going to have to duplicate it on my wife's.

• Any experience with the Hilltopper ( http://www.electric-bike-kit.com/hill-topper.aspx ) kit? It appears to me to be a good fit: Front hub 250W motor, 20 mile lithium battery, 700cc wheel, and extremely simple install for $799.

• I realize that batteries are a whole 'nother huge subject, suffice to say that I'll pay for quality lithium, I want enough for hill climbing assist for, say, 20 mile or so range with me pedaling most/all of the time, and I'd like to mount it within the frame triangle, the lower the better.

• I've never even ridden an e-bike, but I have an appointment next week with a guy who sells and installs Hilltoppers, as well as his own systems that he assembles from components.

• I have modest mechanical skills, and likely could put my own system together if the performance and safety gains were worth it, but would really rather just buy a plug & play setup. Thoughts?

 

[dogman dan]

Sounds like you still like to pedal a lot, even with the 10 mile knee. You may find that easy pedaling while your problem heals is just the thing, and an ebike just the tool for it. Depends on your specific problem. I had a minor knee issue from pedaling too hard going up steep hills on single track trails. Enough spinning, or faux pedaling on the ebike really seemed to help it heal better than avoiding pedaling. I just avoided pedaling hard.

On to the bike. 250w sounds like a lot of power, but on the really steep hills it won't be enough. It's like this, once you slow below a certain speed, usually about 12-15 mph, the motor is turning too slow to give it full power. It gets inefficient, and you end up with only 100w of hill help, while the motor suffers from 150w of heating.

So much depends on exactly how steep the hills you need help with are. The lighter kits, 250-350w do fine on mild hills, like 5% grade or less. If as steep as 7-10%, then you would be better off with a more expensive motor of 500-1000w. This would allow riding up 7% grades with no pedaling, and 10% with moderate effort.

Front or rear is a dilemma. I rode more than 8,000 miles with front hubs, because of the balance issue you mention. All of those miles were with suspension forks, and about 7,000 of it with alloy suspension forks. It definitely can be done safe.

But the catch 22 here, is that planetary gearmotors are slightly wider than direct drive hubs. Even dd hubs won't fit between the tubes of all forks. So if you go with front hub, you will first need to determine if your forks are wide enough at all. You might have to give up the freewheeling to find a hub that will fit the space.

The bright side of this though, is your bike has lots of room for carrying the battery up front, in the triangle space. This will help a lot, and make using a rear hub quite tolerable. Put 10-15 pounds of battery up front, and the bike will handle better, even when you do have stuff in the panniers. As long as you don't have two cases of beer in the bags, your bike should handle ok.

 

[docnjoj]

Strictly for knees, since I ride trikes and don't do 2 wheelers any more, but the principles are the same. Short cranks. 150mm or so cranks reduce the amount of opening/closing of the knee joint and will help it heal. Needless to say you gotta gear down and have electic assist too. Spin more and hurt less with this method.
Welcome to E-S
otherDoc

 

[RoadWrinkle]

I am still in the process of trying to buy my first ebike (or build one), but I have had an opportunity to ride several different configurations from the shop here that rents ebikes. Liability/saftey issues are of utmost concern to a rental business, so the person I go to has a few rules:

1.) On Front Hub Motors: Dual torque bars. He will also not use an all aluminum fork, but an alloy that has steel drop outs; or better yet an all cromo steel fork. Either way he uses custom made dual torque bars on the front wheel (Several e-venders like ebikes.sf will sell some version of a torque bar, but you can go to your local welder for the exact fit for your forks; its a small investment that could prevent catastrophic failures and epic wrecks. This quiets the safety issues despite running 1000w MP3 on the front hub version he rents.

2.) Rear rack mounts the battery on all front hub bikes, but he triangle mounts all batteries on the rear hub versions he rents because too much rear weight makes tourists very unhappy when they are tending to scrapes and bruises (or worse) from the unbalanced ride that typically spills inexperienced riders when they make turns.

3.) Never runs anything heavier than a 48v 10Ah battery, pushes the 36v 15Ah as the better all around choice for power/range balance.

I must say the Front Hub rear mount battery configuration was very balanced when I rode it, but the rear-hub versions had better hill climbing torque. I rented his 48v bikes only.

I guess it all depends on if you want the rear rack for cargo other than a battery. If so, triangle mount (or buying a purpose-built frame) is the best option in terms of a balanced ride. (I rented a rear battery mount and tried to load rear Pan bags but it was a wheelie machine).

 

[alienbogey]

Thanks for the replies, folks.

<<You may find that easy pedaling while your problem heals is just the thing,>>

According to the docs the knee is not going to heal, it's slowly degrading. :| Running is out, biking is to reduce stress on the knee, now I need the electric assist to reduce the biking stress.

<<I just avoided pedaling hard.>>

That's what I need to avoid.

<<once you slow below a certain speed, usually about 12-15 mph, the motor is turning too slow to give it full power. It gets inefficient, and you end up with only 100w of hill help, while the motor suffers from 150w of heating.>>

Are there not motors optimized for slow speed/high torque? The hills I need help going up are 1-5mph hills, not 12-15. On some I'm in granny low gear (24 speed hybrid) and going just fast enough to not tip over. My wife is off and walking on those. (I have no idea of the % grade)

<<I guess it all depends on if you want the rear rack for cargo other than a battery.>>

Yep, I want to save the rear rack for cargo, I use it all the time, along with the panniers.

<<Either way he uses custom made dual torque bars on the front wheel (Several e-venders like ebikes.sf will sell some version of a torque bar, but you can go to your local welder for the exact fit for your forks;>>

I've looked at some of the off-the-shelf torque bars ( http://em3ev.com/store/index.php?route=product/product&path=41&product_id=117 ), and could probably fab something myself if I must. Regardless, if I go front hub, I'll have two torque bars up there.

 

[d8veh]

I've built loads of bikes with front, rear and middle motors, some with both front and rear, and one with all three.
If you're mechanically competent, anything is possible.

For a front motor, my advice would be not to go over 350w. Many mass-produced 250w bikes have front motors in weak aluminium forks without torque arms, and they don't break. A 350w Bafang front BPM at 22 amps would be a good option if you want a front motor. You can get the whole kit from BMSBattery for not a lot of money. If you go with this option, ask again, and we can give advice on how to make a safe installation. I'd advise a single torque arm attached to the brake mount.

A rear motor is another option. Any 500w geared motor with about 30 amps at 36v or 25 amps at 48v would give you effortless riding. The only thing to look out for is that most rear motors have the thread for free-wheel gears that seriously limit your gearing options. You need an 11 tooth top gear, but free-wheel gears don't normally go that low. You can get a DNP gearset with one, but they're not the best quality, and you need to factor in the cost. There's one or two motors now with the spline for cassette gears, which means that you have a much wider choice of gears, and you'll be able to use your present cassette. The 36v 500w Bafang CST motor would be my choice. Again you can get a nice kit from BMSBattery.

Mid drives are another possibility. The Bafang BBS01 is not particularly powerful when compared with a 500w rear hub, but in bottom gear it can keep you going slowly without much effort. Neither does it have the mid-range grunt of a 500w hub-motor, and torque reduces a lot as you go through the higher gears. The GNG Gen 2 is more powerful than the Bafang, but nowhere near as sophisticated. The same applies to most DIY mid-drive kits, but I'd say the GNG gen 2 is the most suited to general commuting and normal riding.

Even with a 500w rear motor, you can accommodate a light-weight 20aH battery on the rear rack provided that you tuck it in tight behind the seat-post and get it as low as possible. I make my own racks, but you could even use yours if rotate it towards the seat by shortening the struts. You have plenty of room in the triangle for a frame battery bag. The lightweight LiNiCoMn batteries would fit OK, or you could get a triangular battery from EM3ev.

There's no answer to your requirements - just a lot of choices.

 

[dogman dan]

If you want to grind up the hills very slow, then get a mid drive, such as the GNG kit. This puts the motor driving through your chain, and able to select a very low gear and grind up the hill.

Hubmotors, on the other hand, are permanently stuck in one gear. Which gear is determined by your wheel size. In 700c, you will be stuck in one gear.

The motors are typically optimized for cruising speeds of about 20-25 mph when used with 36v batteries in 26" wheels. They will bog down and make heat if ridden under heavy load up a hill slower than 15 mph. This does not mean you cannot ride slow on the flat, since that does not need full power. It's max throttle up hills at 10 mph or less that can overheat and melt motors. Even big motors can melt, but they do take longer to heat soak, due to more metal.

But all is not lost. EM3ev sells medium size motors that have slow windings. This means that you can buy a motor that only goes 15 mph maximum at 36v. This motor will be able to climb a hill at 10-15 mph without overheating. These medium size motors, when given about 1000w, easily climb hills with NO pedaling.

Given your knee condition, and the lack of expectation that it will EVER heal, I have to firmly recommend that you totally forget the idea of getting a very low powered motor, if you will climb hills steeper than 4-5% grade. From your description of the gear you use, I suspect you are climbing 5-10%

If you will use a front hub, I suggest the DD motor, in the 19T winding. Run it on a 20-25 amps controller, and 48v. You will have just about 20 mph max speed, and you will be able to ride up 7% grades with no pedaling at all easily. 10% no problem with light pedaling, and 13% with significant effort. I recommend the dd for front, because they are not as wide as the gearmotors, and have a better chance of fitting between your fork tubes.

I will help you with installing it properly, using C washers and two torque arms, so you don't break your forks. I know what I am doing with front hubs and alloy forks.

If you choose the rear motor, then I would recommend the MAC, so you get the freewheeling type. Get the slowest one, the 12t, and again, 48v.

The front motor kit will be cheaper, so just another reason to choose that. The freewheeling option sounds good, but it is not as necessary as you think.

 

[KMB]

Just a thought, I have a complete rear 700c geared ebikekit w/tire sitting here. if you wish to try it you certainly can. I live in easten wa. and I'm not really crazy about packing and shipping(I farm, it's harvest time,hence 20 hr. days). You will need a batterry though.It might give you an idea what it's liike on your bike. Anyway...it's here if you want to try it.If you like it...It wouldn't break the bank, i paid 175 for it. Maybe Dogman or others could chime in and tell you if this may work.
Kent
PS. If you like wine tasting, i live in the middle of it, you could make a trip out of it!

 

[greenspark]

Crank Motor

After reading lots of threads about various crank drives, I came across the Bafang BBS01 on http://endless-sphere.com/forums/viewtopic.php?f=28&t=50104, and it looks like it might fit the bill.

For this specific crank drive, can you only have one front cog?

If so, it's likely a deal breaker for me. My area is hilly, and I shift through all 24 speeds of the bike multiple times in every ride. I would hate to give up my three-speed front derailleur.

• Can this particular crank drive be used with three front cogs?

• If not, is there a crank drive that can?

Hi, Just got your PM asking me to comment. Hope its not too late.

The Bafang BBS01 will require you go to a single front cog (chainring) that comes with the motor, but the power completely redefines biking. I'm 62, 185lbs 6'0" and do fine with a 3-speed Shimano Nexus and we have some steep hills (15 degree). It's very different than going through 24 gears under pedal power. Essentially, it's like a car, where in 1st gear, the 250, 350, 500 or 750W does the hard work. You go slower (I find about 12-15km/hr up our test hill). Lance Armstrong pedals at 400W, the normal rider 100W, so the motor gives you Armstrong muscles without the drugs. You probably will not miss your front cogs at all.

I find I use the 3-2-1-off display settings a lot. 3 going up hills in first gear. For some reason our prototypes seem to have more boost when hitting the thumb throttle although Bafang says 3rd is supposed to be full power. I've asked Bafang to separate the thumb throttle from the pedalec settings. We'll see when the next order arrives. On the level, I turn it to zero since I'm trying to get exercise, but if I keep it on, it comfortably drives me about 25 km/hr as long as I keep pedaling. It's not a moped; I've got to work, but no pain, just good exercise.

Installation is not complicated, provided you have the tools to remove your crank and bottom bracket. I find the bigger challenge is the rusty stuff on the old bike. We've now installed the prototype motors on a new Bella Ciao (Italo-German), a 1980's Gazelle (Dutch) and a 1951 Raleigh DL-1 (the classic British Army/Policeman's bike). The Raleigh came with a 75mm wide bottom bracket and we used a reciprocating saw to chop off both sides to bring it down to 68mm. Because the BBS01 is a compression fit, rather than threaded, it fit fine.

As other posts comment on this motor, it is a game changer. Quiet, efficient, subtle and low centre of gravity.

We're also buying the new 29E battery pack from Cellman, where a 403 Wh/hr battery weighs 2.2kg and is smaller than a brick. Fits in a saddlebag, and its hard to tell it is an ebike. Real stealth. We're now talking with the Bafang factory about supplying motors without a display, instead just an on-off switch and a 1-2-3 switch for power. Yes, we give up the speedometer and some other programmable features, but for simplicity, stealth and one less thing to break, it appeals.

We're also trying to encourage one of this forum's favourite vendors to start carrying the BBS01 motors. Watch this space.