An Electric Bicycle

[vtsteam]

Great Steve! 

I've had some things from HK arrive in 3 weeks and some in 5 days even without extra postage.

One more point about load and power -- hills will obviously make a difference to amp draw. I'm guessing you'll have to keep an eye on your ammeter on a hill, and slow down until amperage is in the comfortable range again.

Not entirely sure how this is all going to work out -- as I'm really used to airplanes -- it will be really an interesting thread to see how it all works out in practice instead of theory. 

[S. Heslop]

I have a pair of motorcycle sprockets here if you want them, not new but good, 420 chain size.
Lyn. 
PS: may even have a new DID chain as well..

Thanks for the offer but I don't think I really need a chain and sprockets any more with the friction drive.

Not entirely sure how this is all going to work out -- as I'm really used to airplanes -- it will be really an interesting thread to see how it all works out in practice instead of theory. 

Yeah i'm excited to see how it works out too. It's kind of been a lifelong dream to stick a motor on a bike, but I never really knew enough to manage it. I still don't know enough, but having the internet helps!

[S. Heslop]

The gears just arrived in the post this morning, they're really not bad for £5 a pair, and that's everything now delivered.



As for the plan, I spent a while fussing and figured the best way to go about it would be to build a sturdy carrying rack on the rear of the bike for the motor/ idler to pivot on. It's a bit of a clumsy looking design but it's the best I could come up with! A spring on the lower of the 3 bars on the arms will hold the rollers against the rim, and the top most bar will hopefully act kind of like a caliper brake (controlled by cable) to release the rollers from contacting the rim if I want to pedal.



Here's a still from some video I took. I made the punch from a motor shaft, and it's the first piece of steel i've ever successfully hardened thanks to John Doubleboost's video. Heating it till it stopped being magnetic and then quenching in oil did the trick.

(I just noticed that they kinda look like the British Isles. It might be sub-conscious since it's all britain this britain that on the tv at the moment!)


I went to the boot sale today to buy a better jigsaw. I was surprised to see so many people at a Wednesday boot sale. I guess i'm not the only person unemployed in the north east! I also picked up a nice new bench grinder and wrecked arms carrying it home on the bus.


In other news, I've been trying to buy batteries off of ebay. I guess the word got around that laptop batteries were a good source of cheap lithium ion cells. At 8am yesterday morning I decided to try bid on an auction that was at £12 for 20 used batteries, but in the last 5 seconds it jumped up twice to £50! I suppose even at that price it'd still be cheaper than the £500+ they charge for dedicated eBike packs.

I've got a bunch of mismatching NiCd RC car packs I might try rewire to test the motor, but first I want to get some of the metalwork done.

[vtsteam]

Wow, great drawings Steve!

Would laptop batteries have a high enough C rating for the motor? They should be able to deliver close to 100 amps. Seems like R/C batt packs would be the cheapest and most suitable -- even  the low cost ones are 20-30 C. Probably cheaper to put together multiple smaller packs than buy a larger pack. 3S and 2S packs are often the lowest cost per watt hour.

At 20 C and the minimum possible capacity you'd need a 7S 5000 mah pack.

You could make up that from a series hookup of (for example):

http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=31952
http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=32119

You might want bigger capacity than that, which is fine if you can afford it. But it may be more cost efficient then to start paralleling packs -- you'd have to work it out.

A word of warning about HobbyKing which I just used as an example. Never order batteries from them overseas -- ONLY buy from the UK warehouse, and ONLY if the item is listed in stock. Their customer service and honesty are not beyond question in my experience, and you could wait months to receive an order -- or even never receive it. Generally orders from the local country HK warehouse are reliable, but sometimes they gouge you on postage. If you use another source for batts that you know well, that's a good option.

I use Zippy brand batteries in my planes and they are a good low cost reliable batt.

[vtsteam]

I should mention, of course, and probably you already know that Li-ion cells like laptop batts are safer than Li-poly batts like R/C batteries. But both need special chargers, or you run a real risk of fire and explosion. Nothing to fool around with.

In my opinion the best Li-poly chargers are the ones that charge each individual cell through the balance plug, rather than the type that charge across the whole pack and require that you periodically discharge and balance individual cells. The former is simpler, faster, cheaper (for the charger) and foolproof.

There are other cells which are safer -- A123's or LiFe I believe, but they are a different voltage per cell and more expensive so the number of cells etc. would all be different.

[S. Heslop]

I found this real jumble of a thread on endless sphere. Any decent information on how to do anything is hard to find. I'm not a fan of the ES forums in general.
http://endless-sphere.com/forums/viewtopic.php?f=14&t=26383&sid=a0ae404381381478ccb07127d6820426

I'd assume laptop batteries are adequate because a fair few people seem to be using them for electric bikes.

But everyone seems to be using them now so the price of second hand batteries has really gone high. Looking at those hobbyking batteries linked, at 5Ah and £15 each, £60 worth (not far off what people are paying for the old laptop batteries) would make a 20Ah cell, which is pretty adequate. Plus it probably won't require all the fiddling to sort and test the cells.

[vtsteam]

Sorry Steve, but that's 10AH for that money.

You need one each of the  4S and a 3S (S stands for cells in series) to make up the 7S you need for the voltage your system was spec'd at (if I remember correctly). That's why I gave two listings -- one for 3S and one for 4S packs.

In other words you connect a 4S and a 3S in series to make the equivalent of a 7S. It is still 5 AH total.

You could hook two of those sets together in parallel to get 10ah -- so that's 4 batts together and your 60 quid.

Used laptop cells might not have a full life or capacity left -- usually they don't, in my experience.


1 Lipo cell = 3.7 V nominal
so
3S = 11.1 V nominal
4S = 14.8 V nominal
7S = 26 V nominal


10Ah still seems like a usable amount if your target consumption is 500 watts:

10 Ah * 26V = .26 kWh

.26 kWh / 500 W = ~ half hour duration at full design power

[vtsteam]

One caution, remember you now have a 2.6kW capable motor system, not just 500 watts. If you (well, I mean not you but uhh, somebody else...) starts hot-rodding around you could conceivably get a 6 minute duration at max throttle before you wrecked your batts.

Absolutely essential to have a voltmeter on board as well as an ammeter. You would want to switch off and start pedaling at a red line minimum battery voltage. And always keep throttle below your 100 amp max ESC rating. 500 watts is going to be more like 20 amps.

And a 100 amp fuse, and box of spare fuses as well.

[S. Heslop]

One of each of those batteries costs £35 (although maybe they'll rob me with delivery charges). I suppose it's not too much to take a risk on, and if it works out I can buy maybe a couple more packs to get more range.

I also need a balance charger. I see this one in alot of videos and the price doesn't seem so bad.

I guess I should buy a better multimeter too since my current very cheap one isn't that reliable.

The costs add up! Usually I try not to think too much about the price of things and get surprised when I suddenly run out of money, but for this project i'm keeping a log of everything I spend. I'm curious to see how much I spend in total (tools n all) so I can compare it to just buying an electric bike. I also suspect if I make a video it'll be the first thing people will want to know.

eBike videos on youtube tend to have real bitter comments. People getting upset that it was based upon a cheap bike, people getting upset that it's cheating and an affront to the purity of cycling, people getting upset that it's too complicated for them to bother building, etc. So i'll be interested to see how a video I'd make would fare.

[S. Heslop]

Well the secret delivery cost and paypal's own currency conversion being off by a few pounds bumped the price up to £43.54 for the batteries.

And just like that i've almost spent almost £100. It's frightening how quickly you can buy stuff online. I had a friend who spent something like 150 USD on useless mobile phone software when he was drunk one night. He had that one click purchase so there was really nothing stopping him from going hog wild.

So far i've spent about £150 on materials for the bike, including the bike itself. I'll probably spend another £50 on metal and bearings this weekend and that should be everything excluding extra batteries (or extra speed controllers if i bugger this one up). With the cheapest eBikes costing £500 new it's still cheaper, but not amazingly so.

[dsquire]

One of each of those batteries costs £35 (although maybe they'll rob me with delivery charges). I suppose it's not too much to take a risk on, and if it works out I can buy maybe a couple more packs to get more range.

I also need a balance charger. I see this one in alot of videos and the price doesn't seem so bad.

I guess I should buy a better multimeter too since my current very cheap one isn't that reliable.

The costs add up! Usually I try not to think too much about the price of things and get surprised when I suddenly run out of money, but for this project i'm keeping a log of everything I spend. I'm curious to see how much I spend in total (tools n all) so I can compare it to just buying an electric bike. I also suspect if I make a video it'll be the first thing people will want to know.

Stan

I guarantee it will cost you more to build than to buy. It will be more fun to build and you will learn more so that is a big plus.

eBike videos on youtube tend to have real bitter comments. People getting upset that it was based upon a cheap bike, people getting upset that it's cheating and an affront to the purity of cycling, people getting upset that it's too complicated for them to bother building, etc. So i'll be interested to see how a video I'd make would fare.

I wouldn't worry about most of the comments on youtube. When you read them they appear to be coming from kids that aren't even potty trained yet so how can you expect anything better.

Carry on with your build here, I'm going to be sitting by watching. Thanks for showing what you have done to date. 

Cheers 

Don
 

[vtsteam]

Steve that charger you linked to will only charge 6 cells at a time, and charges a whole pack across the output leads (all in series). Your proposed system has 7 cells so it wouldn't work unless you charged the 3 and 4 cell packs individually. That's possible as long as your packs are removable -- in other words each pack attaches individually to your bike with connectors.

The charge rate is 5 amps max, which means with 5000 mah packs they would each take an hour to charge from full discharge. That would mean for your proposed 10 Ah pack, 4 hours to charge (theoretically) by shifting and monitoring the 4 packs around during that time.

The further disadvantage is that this charger doesn't charge each cell in the pack individually. That means you have to balance individual cells periodically, by discharging and recharging them on a special balance connector board -- a pain in the neck. And waste of electricity and time.

Also sometimes these "smart" chargers have a cutoff minimum voltage and will refuse to charge a whole pack if an individual cell gets too low. The pack may not be bad if that one low cell could be charged individually, but the charger is not capable of recognizing this, and can't charge cells individually. People throw away perfectly good battery packs with these types of chargers as a result.

The type of charger I use charges each cell individually. That keeps them balanced automatically without the need to discharge and recharge them periodically. It also can't fail a pack for overall low voltage -- it treats each cell individually.

This type tends to be a "dumb" charger  -- without a microprocessor and little or no readout (other than an LED showing when each cell is charged).  In other words -- fewer "features" but they do the job better.

I don't know how electronics oriented you are but I can contrast the two types of chargers as:

 Type 1 has a single voltage regulator attached to a single microprocessor. It charges across the whole pack. It needs a complex internal program for guessing the state of cells in a battery pack. It needs multiple adapter connectors and leads for attaching to different brands and sizes of manufacturer's connectors used on the main battery pack power lead.  It also needs a balancing connector board. All these advertised leads and boards look like added features -- but they're really just unfortunate needed complexity due to the way it charges.

Type 2 has multiple voltage regulator circuits -- one for each battery cell -- each one is treated individually. It's dumb It doesn't guess anything. It also charges across a different battery connector, called the "balance connector" which is standardized across almost all battery manufacturers. It therefore doesn't come with a bunch of adapter battery leads or a balance board. It doesn't need them.

I'll look into chargers tonight and see if I can find something reasonable that would work better -- bottom line is, yes you can use that charger you linked to, but you will need to spend a lot of time and attention shifting and monitoring battery packs, and it may refuse to charge a good pack at some point.


re. meters: For a bike I would personally be tempted to just use cheap universal automotive type analog meters.

However there are now some nice Chinese LED digital readouts for V and A -- I got one recently. And with a 100A shunt resistor (usually purchased separately) they would work in the range you will be using. These are really components, not cased meters.

Personally I find digital readouts less good as a warning device than an analog pointer, and the automotive type are cased and ready to go.

[S. Heslop]

I guarantee it will cost you more to build than to buy. It will be more fun to build and you will learn more so that is a big plus.

Oh yeah i'm definitely enjoying myself and learning stuff - but I also enjoy totally over-thinking videos!

I'm mostly copying Matthias Wandel's style of videos, but I find the types of comments I get pretty interesting. Especially the ones that get upset about the price or effort it takes to build a thing compared to buying it. So I thought I might try pre-emptively address that kind of response in an electric bike video and see how (or if) people react.

[S. Heslop]

Steve that charger you linked to will only charge 6 cells at a time, and charges a whole pack across the output leads (all in series). Your proposed system has 7 cells so it wouldn't work unless you charged the 3 and 4 cell packs individually. That's possible as long as your packs are removable -- in other words each pack attaches individually to your bike with connectors.

That's a shame. It'll hopefully get me started for testing the motor though.

[vtsteam]

Hmm after looking at specs of about 5 different chargers, it looks like the one you linked is a sheep in wolf's clothing.

The digital display and bunch of cords makes it look like the "smart" type 1, but I think it may actually combine type 1 and 2.

I think it can charge individual cells through the balance connectors on the side of the main unit, but includes cords to charge across the pack, and cords to use an auto battery for charging Lipos as a power source.

If so that's a good deal. The only drawback is that it doesn't charge 7 cells. So you will have to charge your 4 battery packs individually.

If this is a combo type 1 and 2 charger -- I don't see anything better for the price range.

There might a way to charge the two 3S packs together (using a made up wiring harness) reducing charge time by an hour.

[picclock]

Hi

Just reading this thread and noticed the picture of the motor working on the side of the wheel. When I was in holland I noticed some bikes with a small IC engine which was driving the top of the wheel (front wheel). These appear to be sprung loaded to bear vertically down on the tyre which gives a high friction drive. This all but eliminates any problem of rim misalignment. Just a thought if you haven't considered it.

Best Regards

picclock

[S. Heslop]

Hi

Just reading this thread and noticed the picture of the motor working on the side of the wheel. When I was in holland I noticed some bikes with a small IC engine which was driving the top of the wheel (front wheel). These appear to be sprung loaded to bear vertically down on the tyre which gives a high friction drive. This all but eliminates any problem of rim misalignment. Just a thought if you haven't considered it.

Best Regards

picclock

Thanks for the suggestion. I've seen a few of that type around but I don't really like the look of them. Some people have used sandpaper to try and get a grip and it just seems like it'd cause alot of wear to the tyre, and wreck them if the wheel ever stalled and the motor kept spinning.

Plus, secretly, I also want to try doing something that I haven't seen done before (even if there's a good reason why nobody's tried it this way before!).


As an update, the batteries and other stuff all arrived. I'm now ordering some new connectors (EC3) for the battery since the ones that come with them from hobbyking are some weird genderless ones, and i'm having visions of accidentally plugging them together when fumbling with 12 or more identical connectors. So i'm holding off testing the motor and controller for now. I also need to buy an ammeter and volt meter, or at least read up on how shunts actually work so I can use the multimeter I bought outside of its 10 amps max.

So i've been doing some more metal work and I'm caught in one of those... chains. Where I want to turn down some forstner bits to drill press fit holes for the bearings in aluminium (forstner bits drill aluminium surprisingly well, although i'm making sure to hold it down securely since there's probably a big risk of them grabbing the work piece). But my lathe cant produce a finish worth a damn any more, and I don't want to risk trying to turn the relatively tough forstner bit steel with it as is. So i've decided to give it a long overdue tune up. But that's requiring the delivery of some shim stock. It's a chain of jobs I can't get started on until that one delivery arrives.

[vtsteam]

Steve, I know just how you feel!

[S. Heslop]

Well, forstner bits can drill aluminium it's tough going.

I'd also made the 19mm drill and  hole about a quarter millimeter too small. And while the 24mm bearing did press in (using a bench vise) it ended up seizing up despite machining a pressing die to only push the outer race. It's gonna be tough getting that back out.

I think i'm gonna have to approach this different. I might try using my duff 4 jaw chuck as a face plate, the chuck jaw channels would probably work as T slots.

Alternately I could order some reamers of the right size. How do reamers fare with loose setups, like a drill press with a millimeters play?

[vtsteam]

I don't really know what you're trying to do, Steve. Any pictures to make it clearer? How thick material, how large the piece, how big the hole?

To speak just generally, for close and/or odd sizes, boring is my favored method for large enough holes in thick enough material to be held in the lathe.

I have made odd size special purpose drills upon occasion, and have also made simple reamers using drill rod (silver steel) with a flat ground at an angle diagonally at one end. But again, hard to tell what you're doing.

Usually boring works best.

[S. Heslop]

Here's the plate with the stuck bearing. I did think a little ahead and drilled two small holes into the step so I'd hopefully have an easier time trying to get the bearing back out. It's just very tight! I'm thinking about removing the inner race and trying to crack the outer one, but i'm a little worried about messing up the soft metal surrounding.


Here's the chuck. It's far out of square unfortunately, and I don't know if I could be bothered to spend time carefully shimming the plate if I held it in the jaws, so I figured it'd be easier to just turn it into a real fat faceplate. M8 nuts would fit alright down the channel if not for the scrolls.


The scrolls are held in by pressed in yokes, which is apparently a common design for 4 jaw chucks and they're supposed to press back out. But I figured it'd be easier to drill and tape a hole in the backs of them, and use a screw to pull them out. Unless they're made from some super hard steel, in which case I'll have to make some sort of forked punch to get them out.



I was really thinking about boring the plates on the lathe to begin with, but I was curious to see if the forstner bit idea would work (which it almost did! I guess I just overdid it shaving the forstner bits down on the lathe).

[vtsteam]

For removing the bearing, you might try putting the plate in the freezer overnight, then using a propane torch to heat the aluminum plate around the bearing while pressing it out.

Steve I don't know how much material you have available, and I know money is tight, but if you could hold something else in the chuck, with holes tapped into it to match holes in the part you want to bore, you could first mount that piece and face it square, then bolt your part to it -- it is now square, and then bore your holes. Think of it as a temporarry faceplate.

My first faceplate in my homemade lathe was just a piece of 1/2" pipe screwed into a pipe flange. I mounted that, turned the face of the pipe flange square. Then I screwed to that a 7" dia 3/4" plywood disk, faced that.

Then I mounted my actual rough cast 7" aluminum faceplate blank to that, and faced it, both sides, after turning it around.

Then I bored it and had myself a true aluminum faceplate which replaced the temporary rig with drill rod for an arbor.

Then I trued the edge of the new faceplate did a minor cleanup of the face, and all was well.

[S. Heslop]

We're babysitting a baby tonight so I couldn't really try whacking the yokes out, so I just used the 4 jaw chuck as is.

And it worked pretty well! Took a bit more setting up but gentle bumps from a hammer got it perpendicular to the lathe. I figure it's going to be more accurate than the forstner bits on a drill press would've been anyways.

It was maybe still a little on the tight side but I pressed the bearing in no problem. Being an idiot I forgot to first machine a bore gauge to check how close I was to getting a good fit, so I just took light passes till it felt close.

I guess I should've done this in the first place.

[S. Heslop]

For removing the bearing, you might try putting the plate in the freezer overnight, then using a propane torch to heat the aluminum plate around the bearing while pressing it out.

This got the bearing out no problem, thanks for the suggestion!

In other news, turns out my lathe tailstock was pretty much perfectly aligned by default, which was a nice surprise after it seemed nothing else was. I'm now turning a new motor shaft (to fit the gear) between centers.

Had a stupid accident though. To get half-decent footage of the lathe i've been standing the tripod on top of the table and using a step ladder to reach it like in the photo below.



No prizes for guessing what happened. Thankfully the camera is still intact and doesn't seem to have sustained any damage. I was recording when it fell too, and had the lense extended far out to focus right in on the workpiece. I guess all the bulk from the telescope mounting (it's really a telescope tripod!) hit the ground before the lense did and saved it.

I've been thinking of constructing a 'sky hook' similar to doubleboost's for a while, so I guess after this I should really stop putting it off.

[vtsteam]

Maybe a pipe clamp between joists would work as a temporary support bar for your sky hook.

If you had an extra pipe clamp slide, you could slide and lock that in between the other two ends, and attach a drop rod for the camera to that.