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Looking for conversion advice/input for steep hills.

Old 10-20-18, 11:52 PM
  #1  
Kapusta
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Looking for conversion advice/input for steep hills.

My wife and I are considering electric bikes to go to and from the downtown area from our house. It is only ~ 1-1/2 miles (depending on how we go) but it is a big hill. The return trip is about 600 ft climbing and there are a few 10% (even brief 12%) grades. Once in downtown, everywhere else we want to go is within a few miles and dead flat.

We cycle a lot, and I can make it up the hill on regular bikes, but it is a very hard workout and not something we want to do after dinner in town. We have been driving it, but would love to be able to take bikes. thus, eBikes.

So I am looking at doing an electric conversion on our town bikes. Both are 26" mtb-frame based commuters that I built up from frames myself. Rigid forks. One fork is steel, the other Al, but I can replace it with steel easily if I need to. Both are 135mm rear spacing, QR all around, V-brakes. Both 1x8 drivetrains. Regular threaded BBs. I am around 175 lbs and my wife is around 135 lbs. We really love these bikes as they have all the fenders and racks/baskets we like, plus they are both pretty styley. We just don't use them anymore since we moved up on this big hill.

What we ultimately want is a throttle motor that can do as much of the work as possible up these hills. We have no interest in pedal assist (we would pedal enough to make up what the motor lacks). I don't see us ever going very far with them, no more than 10 miles in a trip.

I need to keep the total cost to under $1K for each bike.

So my first question is whether a hub motor is out of the question for this. My understanding is that we would need really powerful hub motors since they cannot take advantage of the bike's gearing? FWIW, we are not too concerned with top speed on flats, just the climbing. A friend of mine did a front hub conversion and I liked how simple and easy it was. And it looks relatively easy to revert if we were to go on a trip where we wanted to take these without the motors (am I wrong about that?).

If a hub motor is not in the works, what is my best bet for a mid-drive? Again, we are not interested in pedal assist, and do not want to spend the money on it if it adds cost. The two options I've looked at online are the Bafang BBS02 and BBSHG. The BBSHG looks really awesome, though it is probably more than I wan to be spending if the BBS02 will do. I liked the idea of the gear changing sensor, particularly for my wife who can be a little ham-fisted with gear changes. Any others to look at?

I have little experience with ebikes (other than riding a few) but am a very solid bike mechanic.

Thanks for any help/recommendations)
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Old 10-21-18, 08:08 AM
  #2  
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The rule of thumb for hub motors when ascending is you must keep the speed st 50% of the max or else too much energy is being transferred into heat. If the hill is short, no problem. Almost everyone agrees for steep climbs a mid-drive excels. The BBS02 (should cost < $450) is excellent, and combined with a good battery (you shouldn't need more than 5 ah for your trip), will be < $1,000. You'll still need to pedal IMO, but not excessively hard. My wife and I ride off road on our similarly-equipped bikes and use only about 100 - 125 wh for a 14 mile (7 up, 7 down) ride with 1500' of climbing (BBS02, 52V, 6ah battery). There are easy on, easy off systems, but at this time all are hub AFAIK (look at Clean Republic and Superpedestrian)..

Last edited by 2old; 10-21-18 at 02:33 PM.
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Old 10-21-18, 08:50 AM
  #3  
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A person that built his own bikes can install a hub motor or mid drive work. Let me ask if Kapusta's friend with the front hub can climb that hill? In general, I've always felt that if a rider can make it up the hill, then most any ebike can do it with help from the pedals, but you would need a powerful one to do it on motor alone. That could be a BBS02.

Two Bafang BBS02's at $425 each. Skip all the accessories that Luna likes to sell if you buy from them but do get the $19 wrench, unless you have the proper bike tool. Two Luna Minis 52V6AH at $299 each. Problem solved, if the Mini's are in stock. The Bafang doesn't have a really good pedal assist, but on throttle only, they are fine. A 10 mile range should be within the capability of the Mini. I have a Mini and BBS02, but I've never used them together.

https://lunacycle.com/batteries/pack...-6ah-3-pounds/
https://lunacycle.com/bafang-bbs02-750w-middrive-kit/

Tradeoff is you lose the left side front derailleur. Bike will pedal freely. If you romp along at 25 mph, you might not get 10 miles.You cann always add a frame battery down the road. And downshift to a climbing gear when you go up a steep hill. If you couldn't spin the gears with your legs, it's just as as hard for the motor. Get thumb throttles. Twist throttles lead to unintended acceleration when walking a bike.

Easy on, easy off with a hub motor?. Not going to happen if you're thinking your current QR system. A Front hub motors kits should have double torque arms and are carefully wrenched down. You'll have to readjust your disk brakes every time you switch wheels. And I think it's best to only tighten those axle nuts sas few times as possible.

Last edited by Doc_Wui; 10-21-18 at 09:02 AM.
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Old 10-24-18, 01:33 PM
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We have a 500W 48V 12AH hub motor bike purchased from the Chinese manufacturer and I have a mtb frame based Trek commuter conversion with a BBSHD 48V14AH (1500W). The hub motor bike is perfectly capable of carrying people of your sizes anywhere you want to go. My bike is more "advanced" with more power, a need to be careful when switching gears under high load (even with the gear sensor), and more potential speed.

Both bikes will go about 40 miles on a charge if the person is making an honest effort to pedal along. Both will still motor along with the throttle at 10-15 mph and perhaps last 15 miles - the BBSHD even with me - a big bear of a guy on it.

My bike was $1500 to build. The Chinese bike was about $1200 to buy prior to the tariffs. Both have their charms, both have their rough details. I prefer mine though. The hub motor bike is really nice at very low speeds/low loads b/c there is no slop in the drivetrain (no chain or freewheel to protect from sudden jerk throttle movements).
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Old 10-28-18, 02:04 PM
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Have you considered a Copenhagen wheel or something similar? My guess is that it would work fine, if bit pricey.
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Old 10-28-18, 03:09 PM
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Originally Posted by msbiker View Post
Have you considered a Copenhagen wheel or something similar? My guess is that it would work fine, if bit pricey.
I have seen it, but being a hub motor I had concerns that it was not the best thing for very steep hills. Thus my question about hub motors in my first post. My research since my original post seems to be confirming that a hub motor is not the best choice fro what we want. I am really not that concerned with how fast something will go on the flats, we do not have very far to go on flat ground.

My understanding is that a hub motor under heavy load for long needs to be going about half max speed (or close to it) or risk overheating. Going half max speed up a 12% grade without a lot of pedal input sounds like a tall order unless it is a very powerful motor. Am I wrong on this?
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Old 10-30-18, 12:27 AM
  #7  
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I don't understand why you don't want pedal assist, because it's easier. Plus you can still have a throttle. And you can set up your pedal assist to varying strengths. Mine has 5 speeds, so pedal assist goes from weak to powerful at the touch of a thumb button. The pedals only need to turn, which is second nature.

For tarmac riding you only need a 250w front hub, pedal assist. If you're intent on using throttle only without pedalling, you'll need more power for that, and more battery, as it's doing all the work.
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Old 11-02-18, 08:56 PM
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Originally Posted by Kapusta View Post
......My understanding is that a hub motor under heavy load for long needs to be going about half max speed (or close to it) or risk overheating. Going half max speed up a 12% grade without a lot of pedal input sounds like a tall order unless it is a very powerful motor. Am I wrong on this?
You are correct. I strongly recommend against a hub motor for your situation.

The common recommendation of a mid-drive is a good one, but probably more than you need.

Based on your description of what you have done with your bikes, you should have no trouble with an ebike conversion.

As an alternative to a mid-drive, you may want to consider one of these: https://www.amazon.com/dp/B01N6KA4KL/?coliid=I37O5ETMIXDPA8&colid=3D7G6CPMWK8AE&ref_=lv_ov_lig_dp_it&th=1&psc=1

For your particular application, you may want a larger cog on the rear wheel (and longer chain) to provide more torque, but lower top speed. The freewheel on the motor means that there is almost no drag when you are not using the electric side.

One source for sprockets with more teeth: https://www.bicycle-engines.com/6-bo...mall-diameter/ there are many, most targeting gas engine conversion.

I recommend a down tube battery to keep the bike better balanced, rear rack battery makes the handling of some bikes very squirrelly.
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Old 11-03-18, 02:03 PM
  #9  
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This is my experience as a 70 yo rider. I have a gravel bike with a 1000w BBSHD and a Tandem bike with a 500 watt, 48 volt , MAC front hub motor with high torque windings. We have a similar terrain situation as you do. A VERY steep 1/2 mile long hill that we have to manage when riding. On the tandem we dreaded that hill because we were moving at 3 mph and were wiped out by the time we got to the top. I got the front hub motor because it did not interfere with the very low geared rear chain rings and cassette. I added a front handlebar bag that would hold and hide the wires and the controller. It has a front throttle, cruise control and three speed settings.

The Tandem along with our weight adds up to around 300 lb. We approach the hill in our third lowest rear cassette and lowest hub speed setting. We try to contribute as much as we comfortable can to the effort and let the motor do the rest of the work. We climb up the hill easily and comfortably, usually averaging 8 MPH. We try to keep the RPMs up so that the motor does not labor. Since we did not mess with the bikes chain rings and cassette, we have lots of low end gearing to contribute to the effort. We love it and would never go back. The 500 watt motor has more than enough power and when we get to the top, the motor never feels hot.

The beauty of the front hub motor is that it feels like a regular bike except it's 15 lbs heavier. So when were just riding along we only use the motor as needed to get us over the lop de loos. It's also nice when we have to stop at a stop light. We can goose the throttle and get us going and thru the intersection quickly and safely. A Tandem is not the quickest when getting going.

Now to the BBSHD gravel bike. I've got a 42 tooth chain ring on the front and a 10 speed cassette on the back. It feels "more" like I'm riding a electric scooter and not so much a road bike. Even at the lowest assist level the motor somewhat spoils the bike riding experience. Since power is being driven thru the chain, shifting needs to be done with thought or else you can get a clunk from the drive train. The setup is definitely more powerful and can handle anything I can throw at it. If I'm not careful it can be a handful! Still it's a blast to ride, just different!

I purchased both kits from EM3ev.com. Quality products and good service

Hope that helps
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Old 11-07-18, 02:12 AM
  #10  
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Thanks for all the replies!

After reading this, doing some more research, and (most importantly) talking to a local friend who has a side business selling and renting ebikes and doing conversions (he was out of town for a few weeks on an ebike tour when I first posted this) I am leaning towards the BBSHD.

With the hills here he strongly recommends the mid-drives, unless we want to do a bit of pedaling ourselves, which for these bikes we don’t. I should acknowledge that we are not getting these for exercise, we are looking at them as electric motor scooters that we can still park in a bike rack. We have regular bikes, and we ride them plenty. The ebikes are for when we DON’T want to be exercising.

As far as the BBS02 vs BBSHD, he thinks that either have plenty of power for what we want but has found the BBSHD to be more robust and reliable. He has installed many of each, and has seen a few (as in "few", not "a lot") BBS02 units burn up on the hills, though it was likely user error (pushing too high a gear up these hills?)

Long of the short was that either would be a good bet, but If we could swing the extra money for the BBSHD, he thought it was worth it. He also recommended we get the kits from Luna (but I will take a look at EM3ev as well). And the smaller batteries should have the range we need if we want to keep the cost down.

Another thing pushing me to the more powerful mid-drive options is that I realized I was hardly ever riding my commuter bike for errands anymore, and the hill was the reason. When we lived in town where it is flat, I did almost all errands, including grocery shopping, on my bike. Having a bike that lets me haul a big load of groceries up the hill is going to let me go back to doing more things on the bike again.

Someone asked about my friend with the front hub motor: It does get him up the hill, but the steepest parts (what are like what our whole hill is like) require real pedaling on his part. It is fine for what he uses it for and what he wants - to get some exercise coming home from work without the full kick-in-the-stomach that pedaling up these hill scan be - but that is not what I am looking for.

Anyway, thanks again for the input.

Last edited by Kapusta; 11-07-18 at 09:52 AM.
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Old 11-23-18, 10:37 PM
  #11  
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Not saying it's not the right choice, just saying maybe you want to look again... I was leaning strongly to a mid-drive until I started thinking about all the power going through the rear cassette. Was not really meant for that and may break eventually (mid ride) ...

So I'm now leaning toward a rear drive geared hub motor (Bafang). Same motor and internal gears as used in the BBS series, but driving the wheel directly. It'll freewheel coasting or just pedaling, so if the electrics go out, just ride home.

I'm looking at advanced pedal assist (PAS) kits from Grin Technologies based on a G3xx series. This way the pedal input adds the motor and the cassette still only sees your leg power. The wheel sees it all, just not the cassette.

I want a crank torque sensor in the BB so that as I pedal more firmly, the motor adds more proportionally. It's stated to feel more natural and makes sense to me.

Maybe look a little further ...

This way you have no over-torque into the cassette, but all the gear reduction advantages of the BBS series. Shifting will be more natural as you are still doing it just as you would with a pedal only bike
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Old 11-25-18, 09:26 AM
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Originally Posted by BrocLuno View Post
Not saying it's not the right choice, just saying maybe you want to look again... I was leaning strongly to a mid-drive until I started thinking about all the power going through the rear cassette. Was not really meant for that and may break eventually (mid ride) ...

So I'm now leaning toward a rear drive geared hub motor (Bafang). Same motor and internal gears as used in the BBS series, but driving the wheel directly. It'll freewheel coasting or just pedaling, so if the electrics go out, just ride home.

I'm looking at advanced pedal assist (PAS) kits from Grin Technologies based on a G3xx series. This way the pedal input adds the motor and the cassette still only sees your leg power. The wheel sees it all, just not the cassette.

I want a crank torque sensor in the BB so that as I pedal more firmly, the motor adds more proportionally. It's stated to feel more natural and makes sense to me.

Maybe look a little further ...

This way you have no over-torque into the cassette, but all the gear reduction advantages of the BBS series. Shifting will be more natural as you are still doing it just as you would with a pedal only bike
Got a link or model name for that hub motor you are talking about? Is the gearing fixed, or can it be shifted?
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Old 11-25-18, 11:57 PM
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I can't post links yet - to new. PM me and I can send you the links. I can't PM you yet either ...

But if your can find ebikes.ca (Grin Technologies) on the web, you can navigate to this area:
  • Home -> Product Info -> G31X Mini Geared Hubs
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Old 11-26-18, 03:04 AM
  #14  
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Originally Posted by BrocLuno View Post
I can't post links yet - to new. PM me and I can send you the links. I can't PM you yet either ...

But if your can find ebikes.ca (Grin Technologies) on the web, you can navigate to this area:
  • Home -> Product Info -> G31X Mini Geared Hubs
I found it, thanks.
https://www.ebikes.ca/product-info/geared.html


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Old 11-30-18, 09:37 PM
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I have been pursuing a similar build stratgey. Hills are not so much the problem day in and day out, but when we go away to go trail riding, they always crop up. So I have been going around with steven at Grin and am alomost done with build spec. All I have to do is pull my cranks and measure the BB spindle end to end to get the right torque sensor into the order ...

What I really want is teh complete Bafang H400 Solution as seen here: https://www.bafang-e.com/en/drive-sy...-system-1.html And I want to use their OEM FOC Sine Wave Controller as shown in this image:


What I like about this one is that there are four cables total. Two out one end, two out the other. Seems like it could lead to the sleekest seatpost install. Problem is I can't find a vendor who'll sell either the H400 as a kit, or the Bafang controller ...

I'll settle for a Grin square black box with extra leads theis time, but I'll keep pursuing the Bafang all factory system for a future build
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