Power: Motor>Chainwheel>Hub Gears>Wheel

[Dartmoor]

First, many thanks to whoever runs this excellent site. Second, apologies in advance if my ignorance of forum procedures and/or engineering and/or your language (!) causes any problems.
I need an electric bike that will go places that would normally require a 4x4: small rocks, mud, low undergrowth, 25% incline, moving at 3 mph or less. No pedalling (legs feeble, for support only). Actually, a lightweight scrambler motorbike.
Max 20 miles per trip, of which max 3 miles in rough country, the rest on tracks large to tiny. No roads. Folds enough to fit in boot (trunk?) of car. Total weight 65lb. Total load 170lb. Cost: say $3000? I'm thinking of using a Tern Link d7i: http://www.evanscycles.com/products/tern/link-d7i-2012-folding-bike-ec032583
Whilst I'd be very grateful for any advice, my question today is this. (I've searched the site, perhaps using the wrong terms.) Why do so few electric bikes take the power from the motor and apply it to the rear wheel sprocket, and so into a hub gearbox (eg Shimano) selectable from the handlebar?
If the answer is, "Something would break", I am puzzled, because a strong cyclist could produce the performance I require, without breaking anything. If the answer is, "Gearchange won't work", please tell this ignoramus why.
Thanks again.

 

[d8veh]

Lightweight folding bikes are not really suitable for off-road use because of the small narrow wheels. I have a Dahon Jetsream, which is just about OK on country tracks, but the wheels would soon get damaged if it were at all rocky and they sink in to mud. Have a read of this article, which might give some insight.
http://www.foldsoc.co.uk/offroad.html
You can get 26" folding bikes like this one and fit a GNG kit with the battery on a rack. You'll still need a fairly large boot to put it in.
http://www.ebay.co.uk/itm/Land-Rover-City-Elite-Folding-Mountain-Bike-MTB-Green-ATB-New-/190737828526?pt=UK_Bikes_GL&hash=item2c68dc4aae
http://www.gngebike.com/mid-drive-kits
As you want slow, you might be OK with the 36v brushed motor version. The bigger brushless motor kit is more powerful, but I find it a bit fierce at low speed in a low gear.
Do you want a DIY kit or a ready-made solution? Please update your profile with where you live so that people gan give appropriate advice. I'm guessing you're in UK

 

[amberwolf]

Why do so few electric bikes take the power from the motor and apply it to the rear wheel sprocket, and so into a hub gearbox (eg Shimano) selectable from the handlebar?

Have you read thru this part of the forum?
E-Bike Non-hub Motor Drives

As to why, because its' easier for most poeple to do, and cheaper, and more reliable in many situations.

 

[Dartmoor]

Thanks, d8veh. Very useful links, especially the gngbike. A 20" wheel and a low saddle lets me support the bike on awkward ground, e.g. traversing slopes. The Tern will take 2 1/4" knobbly tyres. Must avoid jockey wheels - too easily damaged. Yes, I'm from SW England - Devon.
Thanks, amberwolf. Yes, I tried to search that forum - eg, "gear" - thousands of posts. As you say, easier, cheaper, more reliable. But can I get the performance I want without gears?

 

[pdf]

I have two bikes, one has a hub motor and the other a mid-drive to a left side crank with no freewheel. Both bikes have their advantages and disadvantages.
The "bike" you refer to would, if I understand, not be a bike, as far as I can tell. If the motor were driving the rear sprocket through a geared system, then there would be nowhere for the chain from the pedals to go, unless there were a jackshaft. There are plenty of people who do this, but as to why more don't, most people don't need to go 3 mph up 25% grade. And a hub motor system is much simpler. My mid-drive wears the chain and freewheel much faster than a hub motor since it adds the power directly to the entire drive system. Bike parts, in general, were not designed to sustain even 500W for any period of time and the sprockets and chain are going to wear On a hub motor, the strain is applied only to the spokes and not the drive system.

So there are people interested in what you want to accomplish (3 mph up a 25% grade) that have built bikes to accomplish it. They are more involved to build and the parts will either need to be stronger or replaced more frequently. There are some kits and also some ready built bikes. The Ecospeed is one of the kits, but it is on the high side $$-wise. It seems to be well made though. Will cost you every bit of your est. $$ by the time you get it on the road, and that doesn't include the bike itself. You can spend less money for certain but some of the less expensive through-the-crank systems have reliability issues. Most systems that drive through the cranks will do this easily since very little power is required, less than 400W. Not sure you can stay upright at 3 mph though! My mid-mount longbike will climb darn near anything in low gear and with very little power. That is the advantage.

 

[Dartmoor]

Thanks, pdf. Ecospeed looks like nice engineering - but surely overpowered for my purposes? I thought even champion cyclists only generate about 150 W? But they have gears ...
Wouldn't a motor dangling well below the bottom bracket get bashed several times every trip?
Maybe I don't understand your "nowhere for the chain from the pedals to go"; even "jackshaft" is new to me; but I thought these problems were solved by a freewheel-chainwheel, so the same chain takes power from the motor or from the cyclist? (I'll probably have footrests instead of pedals, at bottom bracket height.)
Your warning about wear, important, thanks.
No, can't stay upright, which is why feet must be ready to give support.
I'm keen to see anything that actually fulfills my spec. Can anyone direct me to a video that shows an electric bike doing what I need it to do (see original post)?

 

[amberwolf]

Thanks, amberwolf. Yes, I tried to search that forum - eg, "gear" - thousands of posts. As you say, easier, cheaper, more reliable. But can I get the performance I want without gears?

That is correct--there are thousands of posts, meaning there are many builds there that if you read thru them you would find the information you're after. It isn't quite as easy as just saying: "here is the exact answer to your question" and giving you a link, because there is no one single answer. There are a lot of ways to do what you are asking, and in that forum are most of them, probably all of them, in one build or another.

But you'd have to read thru some different types of builds and see which ones are more suited to your budget, abilities, knowledge, and goals. It might take a lot of time, but you'll understand a lot better about why each version does things the way it does, and which would be more applicable to your goals and why, and so you can make a better choice.

If we just point you at a single thing and say "go for this one" and it ends up not doing what you want after you've built it, you'll probably be unhappy about that. But if you learn why things work tehy way they do, and choose based on that, you'll be a lot happier with the results, and you'll also understand how ot modify what you've seen to better suit your particular needs. If all you want is a quick answer, just go find the GNG drive thread and get one of those, install it, and maybe use smaller chainrings in front or bigger ones in back for slower speeds and higher torque. But I have no idea if it will actually satisfy you.


I am not certain, but based on your questions and answers so far, I'd say that you don't yet have a lot of understanding of how or why these variations do what they do, and I think if you read up on them you'll learn enough to then ask the specific questions applicable to your goals.

As I said, simplicity is one big reason poeple go with hubmotors...but to do what you want to do, a middrive of some type (non-hub) is a much better idea. However, it is much more complex to design a middrive for any particular bike vs jjust slapping on a hubmotor, and if it has to handle extreme situations then it can take more careful consideration, and need more understanding of why and what they do, as well as of exactly what situations it must handle, to do it right.

 

[pdf]

Thanks, pdf. Ecospeed looks like nice engineering - but surely overpowered for my purposes? I thought even champion cyclists only generate about 150 W? But they have gears ...
Wouldn't a motor dangling well below the bottom bracket get bashed several times every trip?
Maybe I don't understand your "nowhere for the chain from the pedals to go"; even "jackshaft" is new to me; but I thought these problems were solved by a freewheel-chainwheel, so the same chain takes power from the motor or from the cyclist? (I'll probably have footrests instead of pedals, at bottom bracket height.)
Your warning about wear, important, thanks.
No, can't stay upright, which is why feet must be ready to give support.
I'm keen to see anything that actually fulfills my spec. Can anyone direct me to a video that shows an electric bike doing what I need it to do (see original post)?

I misunderstood your original post: "Why do so few electric bikes take the power from the motor and apply it to the rear wheel sprocket, and so into a hub gearbox (eg Shimano) selectable from the handlebar? " I thought you meant going directly from the motor to the rear wheel sprocket, avoiding the chain ring. If you send it through the chainring, then of course you still have the pedals. Or if you use a left side sprocket at the wheel, which some people do.

I was kind of where you are now about 2 years ago, but with a different purpose in mind. Just on road, but I do have 20% grades occasionally. I don't know of any videos off the top of my head but I can tell you that there are several solutions for this. It is weird to me that most companies and people show their e-bikes going DOWNHILL or level. Also note however, that a lot of the video is shot from a headcam and you can't tell the grade since it is tilted at the same angle as the bike. Anyway, I can assure you that what you want exists in commercial form and in homebuilts. Cyclone has a video of one of their Cyclone equipped bikes going up stairs:
http://www.cyclone-tw.com/
But as I alluded to earlier, reliability of cheaper kits is not their strong suit. Anyway, I reached the conclusion at that time that most ebikes were not good hill climbers and that is not true. As you know, a relatively low power motor can pull a bike up a hill when fed through the cranks. Take a look over on the non-hub forums. There are probably dozens of people with mid-drives they've built. I want to add also that even a hub motor can climb a very steep hill if the hill is relatively short. I have a 9C 2810, which is a so called "slow wind" (more aptly, high turn count) motor that I run on 72v. Bike and all, I have less than $1000 in this. But it will climb a freakin' steep hill like it is not even there for a minute or more. Above that, it is going to get hot because of the power required to climb at the right speed. As you know, a mid-drive doesn't have this problem.

Finally, what you are paying the most for in the Ecospeed is the bracket system, not the motor. Well, not exactly; you are paying for both, but even if the motor were smaller, the cost would not drop dramatically. The volume is not high enough to bring the cost down. There are higher volume, lower cost kits out there but reliability is all over the place. There is a thread on ES now about a $400 bottom bracket drive system that seems to be decent:
http://endless-sphere.com/forums/viewtopic.php?f=28&t=42785
Anyway, hang in there. Realize that ebikes are still fairly undeveloped and you might be surprised at what is not generally known still. One last link:
http://www.electricbike.com/
has some commercial and homebuilt versions of mid-drives.

(sorry to keep editing but in the link to the $400 bottom bracket system, they also climb stairs http://www.gngebike.com/450wbrushless.htm Note that I am not recommending or endorsing any of these. In fact, some are probably maintenance nightmares. Just showing you there are examples less expensive than Ecospeed. I have a Stokemonkey but it is not really designed as an offroader and they have temporarily stopped making Stokemonkey setups.)

 

[pdf]

Also, while it is probably frustrating, what you are asking is kind of like someone in 1990 asking why aren't there more tablet computers. The technology exists, more or less, but the volume is not high enough to bring the cost down so there is no market. I'm sure you could build a tablet computer in '95 and it probably looked like a good idea but it would have cost $10,000 and looked like crap when you were finished. I had a friend who had an Apple Newton back around 1990 or whenever. He thought it was hot $hit, but compared to smartphone today, it was a cold turd.

 

[amberwolf]

It is weird to me that most companies and people show their e-bikes going DOWNHILL or level.

Because a fair number of them couldn't do an uphill that's signficant enough to be impressive, for long enough without melting, to get on video. And others have such poor performance going uphill (meaning they have to go really slow) that they don't look impressive enough, so instead they just show them going places where they can go fast and look impressive.

It's all marketing BS.

Marketing departments everywhere tend to screw up products or companies, either by forcing the company to change the product to suit some nonexistent "need" to make it "more marketable" or else by marketing it to the wrong audience, and in both cases usually making the product less suitable for those that it was originally intended for or thsoe that actually need something like it. (yet another reason I quit beta testing for music software companies, because the programmers and originators were making a product for musicians and composers, and the marketing departments changed them into crap for dilettantes and kids, making them unusable for those of us that actually needed their products--every single company always went in that direction to try to get a bigger marketshare, eventually screwing over those of us that essentially built their company to what it was at that point).

 

[Samd]

full throttle has a just fitted a middrive kit to a bike after pushing a MAC hub to it's limits. Lots of comparisons. He likes to ride the sort of places you describe, albeit on a bigger bike than you propose.
Might be of interest.
http://www.endless-sphere.com/forums/viewtopic.php?f=6&t=15066&start=135

 

[Punx0r]

Thanks, pdf. Ecospeed looks like nice engineering - but surely overpowered for my purposes? I thought even champion cyclists only generate about 150 W? But they have gears ...

Even a fairly unfit cyclist can sustain 150W constant. A Pro rider would probably do 500W.

Burst power that can be delivered for a short distance is much higher, and yes, the gears help a lot

Consider how much torque your bodyweight on the crank produces...

 

[Dartmoor]

pdf, amberwolf, samD, PunxOr - wise advice, helpful links, thank you very much indeed.
The vids show that some bikes can climb a bit, given a run up. Could they be stopped and started repeatedly when working their way up a rocky moorland slope?
Electricbike site shows (literally) beautiful creations, works of art. Many of your links show complete motor kits, which tempt me to think "Buy a bike, attach the kit, drive away." No way, right? Hyena's superb build video shows a master at work - but on completion, the demo is a bit sad.
Obviously, most of your sources of materials aren't UK-based. eg, Cyclone looks interesting, has a UK site, but it took 10 minutes to find a "secret", mobile, phone number. Maybe just agents, pretty ignorant of the product.
1990's tablet: point taken, but apparently China's streets are filling with geared motor-bicycles. Yes, they would "melt" or otherwise fail, stranding me fatally mid-moor: but by 2015?
150W too small, 750W overkill - should I pencil in 250 W driven through 7 hub gears?
Searching the site using middrive/mid-drive/mid drive: much better than "gear/s". Any other (kind!) suggestions?
pdf may well have this chain/sprocket information already: http://www.renold.com/Products/TransmissionChainSprockets/Sprockets.asp?utm_source=BMON%20AdWords%20Campaign&utm_medium=CPC%20Display%20Network&utm_campaign=Roller%20Chain
24 hours contact with you gentlemen has been hugely educative. Bottom line: I'm probably not capable of a reliable DIY job, and must either pay someone, buy off-the-shelf and modify, or get a pony!
Thank you all very much.

 

[pdf]

In my opinion, here is your bike:
http://www.electricbike.com/specialized-super-charged/
Here is a commercial example (a mere $30k, US)
http://www.electricbike.com/m55/
or perhaps an Optibike:
http://www.electricbike.com/optibike-850r-ride-and-review/
For $2000, there is an R Martin, or whatever the dealer is calling it:
http://www.hightekbikes.com/htb_midmnt.html
I think the R Martin design looks promising. I don't know too many people with one though.

From my experience, the Chinese ebike market is not for offroad bikes. What is most commonly called an ebike in China looks more like a scooter. There are thousands in the cities. Of course, all but the highest end ebikes are made in China, but the domestic Chinese market is mostly for electric city bikes.

Not sure what the UK options are. There are probably a bunch that I've never seen in the States. The UK ebikes I've seen are all low power city bikes. But as you point out, you don't need much power to drive through the gears.

If I were setting up some rough minimum parameters, I think I'd want a motor that would handle 500w dependably. On my mid-drive, I can comfortably keep the power under 500W with judicious use of gearing but keeping it under 250w would require a lot more downshifting. And yes, I think all the examples in the videos would have no trouble restarting up a hill if geared low. The current will spike if you aren't careful, but in a low gear, the bike is going to start moving right away anyway and it won't be a problem.

Anyway, don't give up the search. What you want is available, I'm just not sure you can go into a store and buy it for a reasonable price. You can certainly build it for a reasonable price but as they say, time is money...

 

[Dartmoor]

Thanks to your advice, pdf. And your links. Superb workmanship, wheelies, yet the vids are still coy about climbing, and/or show riders pedalling hard. Probably because what I need is not part of their spec.
Right, 500W it is. 24V? 2012 hub gears (e.g. Shimano) claim that you can change irrespective of pedal power input - no pausing any more. So ...
If buy the Tern Link D7i, and 1) learn about gear ratios and choose suitable output revs, 2) remove the left hand pedal and crank, 3) buy a complete power kit (motor, throttle, controller, batteries), and 4) connect the motor to the newly exposed left side of axle, should I expect to be on youtube soon - an old man making the first non-pedalling 1 mile e-bike ascent over rough moorland? If so, I'll give this website and people like you the credit. Or maybe I'll be on "You've Been Framed", a TV programme showing people making fools of themselves. In which case, I cocked it up, in spite of expert advice.
Would you risk suggesting a kit as in 3) above? Perhaps I have exhausted your generosity.

 

[pdf]

Another video of a mid-drive, a homebuilt with a hub motor driving the cranks.

On watts vs. volts, I think I would use a higher voltage than 24v since this would lower the current and would give you cheaper battery options; a 24v battery supplying 500w continuous at say 15 a-hr would need to have a C rating over 1, which is no problem at all for some batteries but would be a problem for others. I think for you I would suggest 36v if the build parts are equally available in that voltage.

If it were ME, I would try the GNG kit
http://www.gngebike.com/450wbrushless.htm
but probably look at an upgraded mount. However, I would also expect a lot of improvisation on the installation and probably a considerable amount of tuning after the install. If you are up for that, I think you could do worse. It really depends on your position on the $$ vs time and frustration equation. I am part tinker-er, part busy professional. I am sort of in the middle. I would not try to put it on the frame you mention though, unless I looked into it well and was sure it would work.

If I wanted to go all out in terms of building my own, I would start with one of the RC motor mount kits:
http://www.recumpence.net/default.htm
There is no hill it would not climb. Would be a bit pricey and a lot of work, but you would have one of the most kick-ass ebikes in the world. There is a video of who I think is the guy, Shumaker, in a burnout pit in a biker bar at what must be Bikeweek somewhere. It is a trike. He fills the place with tire smoke. That kind of power is something to aspire to.

I know the Ecospeed looks (and is) hideously expensive, but it has a couple of very serious professionals behind its design and service. I've talked to them on the phone, they are very knowledgeable and serious about what they are doing. The position of the motor looks terrible from a dependability standpoint, being low and right behind the front wheel, but I would wager the guys at Ecospeed have put it everywhere they can and this is what they settled on. Downside, shipping to the UK would be killer and out of the box, it is over $4k.

There are simply not that many mid-drive ready to go kits. Some that looked promising have even gone out of business. There was an Aussie legal kit called eLation that I think was pretty good, pretty much what you were looking for, but they are not in business anymore. I'd have recommended you look into that one. I think there are really only two choices for ready to mount kits, Cyclone and GNG (somebody correct me if I am wrong). Both options are going to require some non-trivial tinkering and may not be suitable for your bike. I also believe there will be reliability issues; not insurmountable but significant.

I guess my last word of advice would be to look at a very seriously gear reduced geared hub motor, overvolt the heck out of it, and try to use some restraint on the throttle. Heinzmann used to be legendary with motors of this sort (very high torque, low speed, good reliability) but I don't know about now. Also, they are rare to find in the US so there isn't much known about then here. There is a brand called "MAC" that some people here use and find to be pretty good. Email this guy:
http://www.emissions-free.com/catalog/c6_p1.html
He is on here a lot and knows what he is talking about. There is a guy in the US who deals in BMC geared motors named Illia:
http://www.ebikessf.com/technical/bmc-motors-faq
Kind of the same thing. BMC used to be the best geared hub motor that was readily available in the US.
On the plus side, you would probably spend around $1500 or so to get outfitted and I think you might be surprised how well it works. The downside of geared motors is that they run on one gear ratio and so will be a compromise at best.

That's all I've got. Unless you buy a bike already put together, you are going to be at the "bleeding edge" of ebike tech going up 25% slopes continuously at low power. You might look into an electric trials bike
http://www.youtube.com/watch?v=fRfqyAwXScQ
They are built to do what you want to do all day long (well, until the battery runs dead). It is a production bike and I'm sure if it is built for trials riding, it will do what you want to do, no problem, for ever. Might get a few looks; a grey hair like us on a trials bike. But it would be kick ass.

Sorry I can't be more help. If I didn't have a day job, I'd work on building the kind of bike you are looking for, commercially. Problem is, the market is so small right now, it is going to be very difficult to stay alive in that market. Good luck and keep us posted on what you decide to do. I think at $3k, you are looking at a significant amount of DIY. For more, you can get a commercial solution, but the market is still too small to drive down price.

 

[Dartmoor]

"If you need some help, ask a busy man." Thanks, pdf, for yet more of your excellent advice. The ebikessf site's information will be especially useful. 36v better, ok.
Yesterday I went 10 miles to see mountain bikers riding the kinds of tracks I'll use, to relate pedal turns, speed, incline. Then today, on Google Earth, I was following my route to see if a Google image would help people understand what I need, when I saw my car parked on the verge. Turning the image, there I was, on the other side of the road - recording a new marker stone. So if you would like to see your pupil, his vehicle, and (a flat part of) his terrain, go to 50°34'20.42" N 3°49'35.11" W. Google copyright 2009, but it was 18 November 2008.
Gears. (Just to show I'm trying to learn! Smile and skip.) The Shimano SG-7R46 has a "Gear Ratio Total Difference 244%". I calculate that a 20 inch wheel does 48 rpm at 3 mph, and 250 rpm at 15 mph, a "Gear Ratio Total Difference" about twice as big, so I need either an overdrive, or a motor with useful torque over a range of revs X : Xx2.
http://www.cyclone-uk.com/ have some encouraging ideas, especially for folders, with the motor attached to the down tube. I will contact them.
I'm very grateful to you. If I can work out how to send a Private Message, I'll give you my e-mail, in case some day I can do something for you.

 

[pdf]

Dartmoor:

One last page:
http://www.electricbike.com/ego-kit/
Some good videos there of a kit called an Ego. This kit is about the same cost as the Ecospeed I think. I am under the impression it is an Aussie product and if I am not mistaken, somewhere along the line, it is what the eLation morphed into. I think the GNG is basically the same idea as the GNG but with more flex in the mount. One thing you will notice in the videos is the whine of the planetary gears. On a large "outrunner" like a hub motor used as a mid-drive, it turns so slowly there is no noise. The smaller diameter motors like that on the Cyclone, GNG, and Ego run at high RPM for efficiency and gear down for torque. My mid-drive is based on a hub motor (search "Stokemonkey") and makes so little noise, that it is, for all practical purposes, silent.

I am probably going to put in a geared hub like you mention. Right now I am using an 8 speed freewheel in the back. It works OK but I would like the shifting of a non-derailleur type hub.

Anyway, good luck. People here have helped me a lot so I try to help when I can.