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> Matt's Ev Bike Thread, Project log
AwesomeMatt
Posted: February 29, 2012 03:03 pm
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Figured I should create a new thread for this rather than spamming questions and comments all over the place. So, this'll serve as a project log. I'll need to keep track of this stuff anyway, someone else might as well read/use it.

Warning, first post is gonna be a data dump.

Structure:

I'm somewhat lazily looking to build an electric bike. I somewhat plan on building two different bikes. One, a fast (near highway speed) bike on an old motorbike frame, (would require license/reg/insurance) and a slower (30mph/50km/h) pedal assist bike (pathway legal..ish) on either a mountain bike frame or a recumbent frame that I build myself by cobbling together other bike parts (already have several donor bikes). I'll stick weld 'em with my MOT stick welder.

I'll probably be talking mostly about the bicycle first, occasionally dabbling in the bigger one since I have some parts that are already too big.

Battery:

I plan on using Lithium-Ion batteries from laptop battery packs that I'll (hope to) get from a computer recycler. Supposedly when the pack go, it's often only a cell or two out of 8 or 10. So I'll gut the packs test the individual cells, and make my own pack with my MOT spot welder.

Alternatively, I could use NiCads from old drills, also testing and using the cells that aren't expired (I have a fair bit of these around), or I could just buy some deep cycle lead-acids.

I'm not interested in paying for A123 cells, but I think I might be able to score some for free as these would be ideal, rather than cobbling together packs that have perpetually dying cells or cells that age regardless of wear. These also never need balancing, can tolerate full discharges and can quick charge in 10 minutes.

Batteries I'd like to stay hidden. Perhaps under the cargo rack that hold the panniers, or built into the frame.

Motor:

I'll salvage some DC motor, haven't decided where yet. I already have a couple.

One is a 12V ~1hp motor from a golf cart caddy. The other is a 90V 2.5 HP motor from a treadmill. I can get many more motors cheap/free.

Controller:

Controller will probably be some simple PWM I build myself.

Charger:

Charger will ideally use straight rectified/smoothed 120V (so, 170DC), with the battery pack chosen to match. Might get a motor that could run at that voltage, might get one that runs at half that and throw in a series/parallel switch to split the pack. I'd rather not have to carry a big transformer around to charge the packs on the road, since I somewhat plan to do touring trips with it. This might be an unrealistic goal and I'm okay aborting it if it doesn't work out.

A switchmode charger would be best, since it'll be a hell of a lot lighter.

Gearing:

I'm against building a bike that uses the standard hub motors. I want something that takes advantage of the existing bike gears so I don't lose power on hills and upwind. That means a crank-mounted motor with a high geardown.

I have several single and double-planetary drills to gut. I hope they'll be powerful enough. I may use a 90-degree drill adaptor ($10 but have no idea of quality) to get power out to a sprocket ahead of the crank, or some kind of ring gear mounted to the crank sprockets themselves.

Freewheeling is a bit of an issue. If my legs should be forced to cycle, or if I must be forced to turn over the motor, or use a clutch. I honestly know almost nothing about mechanics so this is black magic to me.

Misc:

Cargo rack, maybe make myself if I can't get one for free.

Paniers maybe make myself.

Break lights, riding lights, turning lights, why not.

Fenders.

I doubt I'll be taking it off-road much (gravel and dirt, but not rocks and logs), so perhaps narrow road tires would be best.
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Geek
Posted: February 29, 2012 03:06 pm
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<OT>
QUOTE
The other is a 90V 2.5 HP motor from a treadmill. I can get many more motors cheap/free.

How suitable are those for say a DIY floor burnisher?
</OT>


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AwesomeMatt
Posted: February 29, 2012 03:09 pm
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QUOTE
How suitable are those for say a DIY floor burnisher?


Damnit Geek, I had an immediate follow-up post and you already replied within 3 minutes! tongue.gif

Umm... what are you asking? If I could use those treadmill motors on a floor burnisher, or if motors from a floor burnisher would be suitable for a bike?

Either way, I don't know. Why, want some?
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AwesomeMatt
Posted: February 29, 2012 05:08 pm
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These are the two DC motors I have available right now:

Here's the 12V (14 really) one, something said it was 45A (almost 1hp), or maybe that was just the controller. It's the size of a wine bottle (the cylinder part before the neck):

user posted image

I didn't really want to use this, since it's from a functional unit (motorized golf caddy). So, to ease my conscience I made a fair attempt to sell it on craigslist for $500. In February. In Canada. The night before Valentine's day. Listing and picture. Oddly no one even made an offer so my guilt is vanquished.

Here's the bigger one. I took the flywheel off and inspected the innards. It's probably way too big to mount on a bicycle, it wouldn't fit anywhere comfortably, too wide to be between the knees and I don't want a chain going all the way to the cargo rack. Might suffice for the motorbike. Don't know if it actually works, should test that:

user posted image
user posted image

Don't know if there's any wear on it:
user posted image

Why 4 wires? What do those blue ones that are going to that silver thing (only) do?:
user posted image

Hrm. Is it supposed to have that crack in it? Seems it was there pre-sale, since there's something shoved in the gap:
user posted image

I yanked the controller out of the treadmill too, but it's black magic to me. I might as well build my own. It did have a disk with holes and a transistor to measure the speed though.

...

Power Requirements:

For power requirements. An average guy can sustain about 100 watts of cardio. Presumably I am such a guy, and I travel about 25 km/hour when pedaling. These are rough numbers, and guessing on them could actually lead to significant swings in power and energy requirements, but, good enough for now.

3 types of power drain:

#1 - Transmission resistance (gears, chain etc). Apparently negligible on a bike.
#2 - Rolling resistance. Something about tires squishing on the road. This increases by weight, (more weight more squish), but is generally fixed and somehow smaller on smaller diameter tires. Also smaller by narrower and smoother tires.
#3 - Wind resistance. This increases as a cube function of speed for power (twice as fast takes 8x as much power). So it increases a square of speed for distance or energy. (twice as fast takes 8x as much power, but you get there twice as fast so it's only 4x more energy).

http://ecomodder.com/forum/tool-aero-rolling-resistance.php <-- Here's a calculator that might be useless.

http://www.lafn.org/~dave/trans/energy/bic...energy.html#s15 <-- Here's a related article that might help you with what numbers to use in the above formula. Wikipedia has more but it's mostly about cars. He understands it well, but I don't. In short, it's complicated to measure. Maybe easiest to just go out and measure rather than calculate.

Here's two rough formulas based on my numbers:

Wattage Required = (0.14736 * speed)^3 + 50 ... (speed in km/hour)
Speed = ([Wattage-50]^0.3333) / 0.14736 ... (wattage is max watts capable by the motor)

Anyway. Roughly speaking if I want a motor to duplicate me, it has to be able to put out 100 watts. If I want to go twice as fast (30miles/hour 50km/hour, about as fast as I feel safe going on a bike) I need 8x as much power (800 watts) if it's all rolling.

Except that at 25km/hour, only half my resistance is due to speed, the rest is due to weight (fixed, at 50 watts rolling resistance). So, it's really only 50 watts x 8, plus the 50 watts for weight. So, 450. That's better than 800. But somewhere in that ballpark.

By this math, the little motor is fine for a bicycle, if I don't care about speed loss on hills. Which I don't, particularly. Extra power is nice and I have it.

The big motor, just to see how fast it could go, it's rated for about 1800 watts (could probably overdrive that to nearly double, especially with airflow?, but not now). So that makes: 82km/hour (50mph). That's okay for city driving if I stay off the freeways and don't have too many hills to climb.

Energy (Battery) Requirements:

Presuming any of the batteries won't struggle to provide power momentarily, battery power only matters for how far you want to go at a given speed.

If traveling 50km/hour, without me helping the bike is using 450watts (plus efficiency losses, I'll ignore for now since I don't know what to guess). If I want to ride for 1 hour, and travel 50km.. I'll use 450watthours of energy.

Here are some laptop lithium ion packs, with their voltages and amp-hour ratings (Volts * Amphours = Watthours):

user posted image

Great, so, 450 watt hours would be about 5 of that big pack on the left. (It's about the size of a CD case and a bit more than 1/2" thick, 3/4" including all the plastic casing). These could easily fit 2-wide inside the triangle frame somewhere and there's lots of room for them.

I like the idea of putting them underneath the cargo rack (hidden by the paniers and no weight going on top of them).. so a 6-pack of 2 deep would fit easy, and 3 high would only take up about 2". That'd give me 550 watt hours, enough to account for motor losses perhaps.

They weigh around a pound each. So, that's only 6 pounds. If I wanted to double my range (to 60 miles/100km) at that speed and sit on my ass for 2 hours, I'd only need a dozen packs, 4" tall, 12 pounds. That would get me almost indefinite motoring when touring, as I'd want to get off at least every 2 hours anyway and towns often aren't 100+ km apart.

Same battery pack traveling at my speed (25km/hour) would give me a 9 hour, 225km (135 mile) range. Without me touching the pedals. More than 2x the range but takes me 4.5 times as long. Of course if I was pedaling and adding 100watts of power, I'd be going 36km/hour, and would cover 325 km (200 miles) in a day. If I could pedal for 9 hours. 5 is probably my max.

For the big bike though.. at 80km/hour I'm soaking up 1800 watts. That's 20 packs (2 long x ~6" high) in an hour to go 80km.

This is becoming numberspam so I'll stop. I could graph this to show the penalty of speed but I'm lazy. Might later.

Bottom line is, at bicycle speeds, a rather tiny and light battery pack can yield enormous ranges (for a bicycle).

Transmission:

I discovered a fun idea the other day:

user posted image

Two drills = E-Bike.

The battery powered drill gears down to a decent speed. A metal bar to couple them (they both have keyless chucks), and then the hand drill gears it down a bunch more and changes the direction of rotation 90 degrees.

The resulting cadence of the drill crank is almost exactly matched to the ~80 RPM biking speed.

Drill a hole through the big gear, screw/weld that to the crank sprockets, mount the extra dummy gear on the far side (or ignore it completely)... and then hose clamp the whole thing to the seat post on a bike. Instant E-Bike. (Though you'd have a hand down around your groin to hold the trigger). I think I paid $5 for the pair.

Get rid of most of the electric drill and replace with a bigger motor, add a trigger, that's pretty damned close to a complete (if rudimentary) E-bike.

I'll shut up now.

Those motors look okay to use btw?
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kellys_eye
Posted: February 29, 2012 08:24 pm
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The cracked(?) magnet looks well-dodgy to me..... that bit in the gap could have been pulled there by the magnetic field....

Have you taken into consideration the effect of a body on the rolling (wind) resistance? Consider a 'low-rider' version (aka Sinclair C5 but with looks and performance... laugh.gif )

Weight is always the killer. Find a frame/wheel combo that's as light as possible.

Use the bigger of the two motors - spare power is great when you need it.

Blue wire/silver thing is probably a speed sensor, possibly a temperature sensor.

A 'legal' electric bike will have speed restrictions - especially for sidewalks. Not sure what requirements you'd need to meet to go as a fully road-legal machine.

Batteries are plentiful via eBay - more so if you're prepared to dismantle packs.


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CWB
Posted: March 01, 2012 02:17 am
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"Break lights, riding lights, turning lights, why not."

hmmm ... an indicator that functions when there is a malfunction ?


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tekwiz
Posted: March 01, 2012 02:19 am
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Matt, you might want to keep it legal & at least make it look like it's built to Canadian standards for road legal e-bikes. These need no license or insurance.
You can find the regs online, but the basics are these: At least token pedals. They have to work, but they don't have to work well. No more than 3 wheels. Max 500W motor power. Max speed of 50kph on level ground. Brakes on all wheels. Standard light motorcycle lighting.


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Pootsky2
Posted: March 01, 2012 02:51 am
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If you plan to use the gears on the wheel of course you are going to be pedaling against the motor when/if you decide to pedal. Might I suggest a fairly cheap/simple solution?

user posted image

user posted image

When mounted like in the second picture it should allow the chain to ratchet not dragging on the motor. If you cut the spokes off the hub and use a belt driven by the motor on middle part it should drive the chain. Kinda like a reverse-brake in reverse! Not that that is any clearer.

should be easy enough to figure a mount.

This post has been edited by Pootsky2 on March 01, 2012 04:27 am
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Geek
Posted: March 01, 2012 07:12 am
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QUOTE (AwesomeMatt @ February 29, 2012 07:09 am)
QUOTE
How suitable are those for say a DIY floor burnisher?


Damnit Geek, I had an immediate follow-up post and you already replied within 3 minutes! tongue.gif

Umm... what are you asking? If I could use those treadmill motors on a floor burnisher, or if motors from a floor burnisher would be suitable for a bike?

Either way, I don't know. Why, want some?

Ooooops! Sorry blush.gif blush.gif blush.gif

It was something in my head I've wanted to do for years, as the electric burnishers are like $3000 for a REALLY crappily made 1.5HP motor.

I knew a guy who made his backup burnisher with some pullies, plywood and a 12HP Yamaha gas motor thumbsup.gif

Electrics are quiet and don't kill birds in pet stores blink.gif

But I have not time to act on that project, ATM....

Cheers!


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AwesomeMatt
Posted: March 01, 2012 10:02 am
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QUOTE
that bit in the gap could have been pulled there by the magnetic field...


It's not magnetic, it's like, a folded over cardboard shim or something. I'm almost certain it got sandwiched in there when it was built. Meaning the assembler knew damned well it was cracked.

QUOTE
Have you taken into consideration the effect of a body on the rolling (wind) resistance? Consider a 'low-rider' version (aka Sinclair C5 but with looks and performance...


I had no idea what that was until I looked it up. Dear lord that is hideous. Looks like a Power Rangers car for kids vehicle.

Umm, yeah, I was planning on a recumbent bike. I find my limiting factor for rides isn't leg strength, it's ass-soreness and neck strain (natural angle when biking with an upright is to look down at the front tire, not up at the road where you need to be).

QUOTE
Weight is always the killer. Find a frame/wheel combo that's as light as possible.


Only on hills and when accelerating. Otherwise, weight almost doesn't matter. Rolling resistance is low. At 50km/hour, it's only 11%. Howevermuch I could strip off the bike, there's no getting around my 180 pounds, so, trimming a few pounds here and there and spending 10x as much on the lighter frame doesn't make much sense. I saw the math last year sometime. The difference between a cheap heavy frame and an elite frame is to arrive 12 minutes earlier at your destination after a day's ride.

QUOTE
Use the bigger of the two motors - spare power is great when you need it.


The big motor is just too big to fit anywhere on a bicycle. But it's a bit small in capacity for a motorbike. One twice that size would be more comfortable.

Unless.. well, I'm planning on building a recumbent. I could probably mount it under the seat sideways, or, forward even since my legs are up above the front wheel. Hrm.

2.5 HP is a crazy amount of power. I'm a bit scared of what that would do if something went wrong. It's also rather heavy.

QUOTE
A 'legal' electric bike will have speed restrictions - especially for sidewalks.


Bikes aren't allowed on the sidewalks here. You're supposed to ride on the road. Friends of mine have been ticketed for biking on sidewalk downtown. Ridiculous. Biking on a most of the roads would be suicide for a casual biker.

QUOTE
Matt, you might want to keep it legal & at least make it look like it's built to Canadian standards for road legal e-bikes.


That's the idea. First, make it non-obvious that it's even an e-bike (hence putting the motor where the water bottle goes and the battery pack under the cargo rack).

Then, keep it, umm, near legal. Legal-ish. Appearing to be legal. There aren't many regulations that don't make sense.

QUOTE
Max 500W motor power. Max speed of 50kph on level ground.


32km/hour, not 50. Supposed to have a motor assist cutoff above that. Umm, hrm. I'll put something in. It might, umm, not work all the time.

Alberta used to have the loosest regs in the world, used to be 750watts.

Also found this: "and are required to wear a motorcycle helmet". Ugg. Not a bike helmet. And, must weigh under 35 kilos. It'll be close. That's 77 pounds. 30 pounds for the bike. The big motor is 20, small one's probably more like 7. 12 pounds of batteries. Transmission, extra frame.. that's getting up there.

QUOTE
f you plan to use the gears on the wheel of course you are going to be pedaling against the motor when/if you decide to pedal. Might I suggest a fairly cheap/simple solution?


I actually picked up a few bikes for their freewheels, but I don't quite understand how they work. I don't really want to keep the whole damned hub.

Here's a good freewheel salvaging tutorial: http://www.atomiczombie.com/ct-freewheel.html <-- Scroll down a page for the start of the article.

Even then I don't quite get how to re-use it. On its own without the whole cassette or without the hub.

Tekwiz suggested a "travelling pin over running clutch". Looks like this:

user posted image

I'd have to buy one somewhere.

He also suggested a "pin clutch" to disconnect the motor, which apparently could be built with the tools I have (not many and less skill).

If it's cheap, or if I can make either of these with my own tools, I'll certainly do so. If not, I'm sort of okay with being forced to cadence.

Wouldn't know where to buy a worm gear either. And I've heard worm gears are 20% efficient (doesn't seem possible to be that low, but, is what I read). I'm definitely not making a worm gear myself.
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Colt45
Posted: March 01, 2012 11:02 am
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it works like a zip-tie, pretty much, just circular and non-ending and metallic wink.gif

But yeah, I suppose you'd need to keep most of the hub.


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AwesomeMatt
Posted: March 01, 2012 11:10 am
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QUOTE
t works like a zip-tie, pretty much, just circular and non-ending and metallic


Well I get how a ratchet works, easy. And I get how the traveling pin works. But I've never actually seen a diagram of what a freewheel is, and when I took two of them apart (one cassette style one normal) they didn't resemble anything like a ratchet.

I'm looking more for two plates stuck together with the mechanism inside, or, like the one Tekwiz suggested, it basically resembles a ball bearing.
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Pootsky2
Posted: March 01, 2012 05:26 pm
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Well if being forced to cadence isn't a huge problem might as well start the feature creep! (I know its early for that biggrin.gif )
When you design your motor controller you might want to think about incorporating the motor as a self charger.

If the motor can be moved by your feet or by the wheel while the bike is moving you get a nice handy little generator which can help extend traveling distance. Granted, probably not much, but some none the less. Probably going to be more important if you ever build the motorbike.

For example if you went with a manual disconnect for the motor drive and used a gear-set that is fixed to the rear wheel opposite the normal freewheel. (Perhaps a multi-speed freewheel welded to the hub). You would get to keep the gears and be able to take advantage of "regenerative braking" when the wheels are driving the motor while coasting. Then when it is time to pedal disengage the motor clutch. (maybe by a solenoid or something?)

Downside is more parts = more weight. Also depends if you are handy with a microcontroller or some other method to do the circuitry for routing the power back to the battery. Plus more complex parts can mean easier failure.
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Jawno
Posted: March 01, 2012 06:25 pm
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I'll be amazed if that little hand drill gear train holds up to the torque requirements of a bicycle. Nevertheless I am following this thread with interest.
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AwesomeMatt
Posted: March 01, 2012 06:35 pm
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QUOTE
might as well start the feature creep!


*glares*

The death of all my projects. If I could ever keep it as simple as first imagined, I'd finish everything. Instead, the only things I ever finish are things I make for other people.

QUOTE
If the motor can be moved by your feet or by the wheel while the bike is moving you get a nice handy little generator which can help extend traveling distance.


This is an un-feature. Why not, instead of spending my energy to charge a battery (% loss), to then power a motor (% loss) to move the bike, wouldn't I just save my energy and pedal the bike directly when the batteries are dead? wink.gif

Worse, it's better to take breaks than to continue solid cardio indefinitely. "Rest before you're tired, drink before you're thirsty, eat before you're hungry" <-- Bike Touring Motto.

QUOTE
You would get to keep the gears and be able to take advantage of "regenerative braking" when the wheels are driving the motor while coasting.


Regenerative breaking is a non-feature really. It's only useful in traffic, and anywhere I'm in traffic I'm not making long trips so I won't run out of battery power. I've heard they're annoying/inconsistent to use and most people that have one (even on motorbikes) disable them.

It could be charged going downhill, but it's rare that there's a downhill significant enough and long enough to warrant charging. Simply going down a hill recovers energy better than slowing to generate when descending. Most foothills around here I'm still pedaling downhill because they'd otherwise slow me. Though I do have a few trips to the Rockies planned.

I'd do it if it was trivial, but I wouldn't put much effort into it.

Brings up an interesting point though... if I'm going 50km/h on a bike, normal cheap rim brakes aren't going to cut it. Disk breaks would be great, except those cost money and I'm cheap. If I have to engineer my own disk brakes, would probably be easier to include regenerative braking (ha, typo'd it as "regenerative breaking", probably the most likely outcome of my efforts tongue.gif) instead. Also, I never never owned a bike that had straight enough rims after a week that the brakes didn't either rub, or need to be set sloppy loose. Disk breaks it is I think.

Here's a picture of disk breaks to break up a block of text and make this seem more interesting than it is:

user posted image

While you've got me feature-storming though, if I don't add a higher gear or two, I'm going to be pedaling all silly-legged with existing gearing setups. Can't make the rear sprocket any smaller, so it'll require a bigger chain ring at the crank (or a freewheel, looking like I'll go freewheel). I might run into the same issues the powered-walking frames the US military was testing. Sure the suit can run miles for the soldier, but if the soldier still has to actuate his legs he fatigues in nearly the same amount of time, particularly at the joints.

I'll have to see, perhaps 50km/hour feels stupid-fast. I've heard racers that get going up that fast don't feel safe at that speed (and they can only sustain it for 5 seconds or so anyway). I do have a bike computer that someone gave me as a gift 20 years ago, I guess I should hook it up and find out just how fast I get going.

QUOTE
I'll be amazed if that little hand drill gear train holds up to the torque requirements of a bicycle.


Heh. I don't really expect it to, mostly because it's somewhat loose and rattles and grabs now and then. But, it is steel. Sewing machines use 100W+ motors and they have a pair of 45' nylon gears that last decades at low-ish speeds. Was more of a "It's neat how for a couple bucks I could turn this junk into something that would technically propel a bike." I'll have to go with a worm or a 45' pair and a sprocket.

More concerting to me is if the power drill planetaries hold up, since that's currently my only method of speed reduction (and my motors are 10-30x the size of what's in a power drill).
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AwesomeMatt
Posted: March 01, 2012 07:20 pm
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Speaking of geardowns being insufficient... double-posting to take/add more pictures, 'cause, project threads are useless without pictures:

18V cordless drill with high/low speed gearing (lifts the extra ring gear):
user posted image

Pretty puny despite being a fairly big cordless drill. Note the size of the shaft on that little motor. Not even as thick as the ballpoint on the pen.

Hrm. Maybe a corded drill will have beefier gears? Let's see what I have laying around... how about this one (1/2 hp)?:
user posted image

Yeah, that looks better. Let's have a peek inside:
user posted image

Well, the 3/8" motor shaft to start off with is certainly more encouraging.

Side by side:
user posted image

Yep, it's definitely larger.

But neither are anywhere close to the size of either of the drive motors I planned on using. Problem?
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Pootsky2
Posted: March 01, 2012 07:21 pm
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QUOTE
It could be charged going downhill, but it's rare that there's a downhill significant enough and long enough to warrant charging. Simply going down a hill recovers energy better than slowing to generate when descending. Most foothills around here I'm still pedaling downhill because they'd otherwise slow me.


Looks like I was thinking too much in terms of my own project and commute. doh.gif Lots of steep hills for me and a longer distance.


Figure its good to throw out any ideas though since it gets the brain stirring.


QUOTE
The death of all my projects. If I could ever keep it as simple as first imagined, I'd finish everything. Instead, the only things I ever finish are things I make for other people.


I sympathize. Features almost killed my MOT arc welder.


As far as the disk brake fabricating one might not be that hard. (I'm no expert by any means though.) I would think the hardest part would be rigging a caliper. Unless you could salvage an existing setup off something like a go-kart or small ATV.
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AwesomeMatt
Posted: March 01, 2012 07:48 pm
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QUOTE
Lots of steep hills for me and a longer distance.


Well, like I said, even on EV motorbikes with only 30 mile ranges, guys purposefully shut off their regen braking because of how little it gains.

QUOTE
I sympathize. Features almost killed my MOT arc welder.


What's that? Feature creep on an MOT welder? HRM.

http://www.dutchforce.com/~eforum/index.ph...124&hl=Mini-Tig <-- Started Dec '08. 18 pages of posts? HRM.

It's simple, right, I'll just make a 4-pole 4-throw 100 amp switch and a bunch of other unnecessarily adjustable stuff.

user posted image

Damn, comin' up on a year since I last worked on it. Time for a revival.

QUOTE
Unless you could salvage an existing setup off something like a go-kart or small ATV.


Hrm. Or off of a crashed bike. Police recover something like 30 bikes a day, many of them stolen then then tossed down a hill or in a river when they're done. Should see if the recovery guy can set aside one for me instead of throwing in the garbage (I suspect they only auction working ones). Good idea.
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Geek
Posted: March 02, 2012 03:42 am
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QUOTE (AwesomeMatt @ March 01, 2012 02:02 am)
He also suggested a "pin clutch" to disconnect the motor, which apparently could be built with the tools I have (not many and less skill).

Ummm..... what about energy recovery, though? unsure.gif

Cheers!


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AwesomeMatt
Posted: March 02, 2012 06:46 am
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QUOTE
Ummm..... what about energy recovery, though?


From where? If I don't care about regen breaking, no problem.

If the batteries are dead and I've mechanically disconnected the motor, I'm just pedaling, it's just a normal bicycle.
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AwesomeMatt
Posted: March 02, 2012 02:13 pm
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Ever wonder what's deeper inside a cordless drill's planetary gears? Well I did. Took pics 'cause, why not:

user posted image

Arranged in columns per layer.

Holy crap I had no idea there were so many gears. 3 sets of 5.

There's a layer of ball bearings to hold the last ring gear and then there must be a lower set of bearings too 'cause it still glides below that. Couldn't take it apart any further, which was a bit of a pain in the ass since I don't really need the chuck. It's extra convenient for a quick setup, but it's an extra pound or so and several more inches that I don't need if I could just couple to the shaft directly.

Contrast this to the 3 big gears (one dual-ratio gear) on the older 120V drill gearbox, which, I counted, does about a 1:38 geardown.

I don't know what the starting RPMs are for either of the motors and I couldn't count the little one's ratio either. It's possible that they're drastically different starting speeds to end up at a similar result.
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Posted: March 02, 2012 09:13 pm
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Those are planetary gears, which always have greater gear counts.
None of those gears with the exception of the big drill are heavy enough. The smaller sets would overheat & fry within not too many minutes under that kind of load.
You might be better off locating a worm gearbox...they are quite common, & using the bare gears with axially mounted motor...the motor shaft parallel to the bike's direction of travel. Any gearbox with the input & output shafts at 90 to one another, & a ration higher than ~4:1 will likely be worm geared. This can be confirmed by trying to turn the output shaft. This should be difficult to impossible, even with a large wrench. The input shaft should turn freely & without perceptible side or end motion.
The gear would be mounted directly to the wheel, & the worm mounted to an extension shaft from the motor. You would have to arrange to tilt the motor so the worm loses contact with the gear for freewheeling...worm gearing is self locking othewise. This doesn't mean it'll instantly lock upon removal of power, but it will mean rapid decelleration, much like compression braking(NOT breaking) in a car with a standard tranny.
The advantage to this is only two moving parts. The disadvantage would be keeping it lubricated & consequent short lifespan.
There are very few options open for power transmission. About the only other simple system is to use a friction roller on the back tire, with the shafts of both motor & wheel parallel. I've done this several times with gas engines & it works well, except that it's awfully hard on tires. I've seen people using hocky pucks with holes drilled in them as friction rollers.
Having spent many years modding & riding powered bicycles, you can bet that your pedals won't see much use, because the extra weight will make pedaling cumbersome, to say the least.


BTW: Did you notice just how little of the grease in the gearbox of that big drill is still in contact with the gears? This shows why grease isn't the best lubricant for gearboxes...petroleum jelly is much better, because it's thinner & tends to cling to gears instead of being pushed away from them.


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AwesomeMatt
Posted: March 03, 2012 05:55 am
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QUOTE
Those are planetary gears, which always have greater gear counts.


Yeah I'm familiar with planetaries. The mech I was working on in Cali had a set of 2 of them, 3' (yes feet) tall on each hip for the walking mechanism.

QUOTE
The smaller sets would overheat & fry within not too many minutes under that kind of load.


You'd think that the drill being, at least a few hundred watts, could withstand a few hundred watts, but, I guess it is a portable drill. I would have figured the weakest link would be the motor melting and that the gears would hold up okay. Oh well, different project.

I can get drills fairly cheap or free. Planetaries give great geardowns in a tiny package but I haven't seen any on anything other than cordless drills so they'll all be about the same size. I guess I'll just go with the bigger drill.

QUOTE
You might be better off locating a worm gearbox...they are quite common


Common in what?

Sewing machines have a pair (metal worms but nylon gears, useless for me), but I've never seen one elsewhere.

QUOTE
This can be confirmed by trying to turn the output shaft.


I'm somewhat concerned with the lack of back-rotation on worm gears, sounds like a recipe for things to snap if anything goes wrong and the gear wants to rotate. Probably not a well founded concern, should be mediated by the freewheeling design itself.

QUOTE
About the only other simple system is to use a friction roller on the back tire, with the shafts of both motor & wheel parallel. I've done this several times with gas engines & it works well, except that it's awfully hard on tires. I've seen people using hocky pucks with holes drilled in them as friction rollers.


I remember you saying how quickly it erodes rubber. While it's by far the easiest power transmission method, I ruled it out almost from the start. Looks ugly, high maintenance and no taking advantage of gearing. I'd rather get a hub motor if I wasn't going to use the gearing.

QUOTE
Having spent many years modding & riding powered bicycles, you can bet that your pedals won't see much use, because the extra weight will make pedaling cumbersome, to say the least.


I find that odd. Plenty of times I've biked carrying an extra 40 or 50 pounds and I've hardly ever noticed a difference unless going uphill, and even then it's not that bad. Going from 220 pounds of bike+rider to 250-260 doesn't seem to be that big of a deal.

I'll have to see, 'cause, I enjoy the actual exercise too. If the pedals become cosmetic I might as well skip the bicycle and just build the motorbike.

QUOTE
BTW: Did you notice just how little of the grease in the gearbox of that big drill is still in contact with the gears?


That drill is so old that grease might have the consistency of silly putty. It's certainly solid enough that I could hang it upside down without it dripping. It's effectively useless except where it was originally applied.
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AwesomeMatt
Posted: March 03, 2012 04:50 pm
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Started thinking about where to mount the big motor, if I was going to try it on the little bike. Then I came to my senses. It's gigantic. The steel case itself is 1/4" thick.

So then I took apart the smaller motor.

The outer casing actually fit completely inside the bigger motor's (with quite a tug, duh, several pounds of magnets, not sure how easy it's going to be out of there). Here they are side-by-side:

user posted image

Big motor is 20 pounds. Little motor is 4-5 pounds.
Big motor is 1800 watts. Little motor, if it scales, should be 360-450 watts. Maybe it's only a 1/2 hp. sad.gif

That's seeming a bit puny right now. Kind of wish I had something in between the two, but maybe it can be overdriven a touch. Especially since it'll have air blowing over it constantly.

Can't tell how worn the brushes are, but they seem to have plenty left on them.

Spent a good part of the day researching recumbent designs and trying to pick what would suit me best. Short Wheel Base, Long Wheel Base, Compact Long Wheel Base, Low Racer, Quasi-Low Racer, Mid Racer, High Racer. Single Straight Pipe frame, Diamond frame, S-Pipe frame. Normal Steering or Under Seat Steering. Front Suspension, and all the different Rear Suspensions. FWD or RWD. 26" x2 wheels, 20" x2 wheels, or 26" rear 20" front.

Here's a link to about 200 pictures of different recumbent's being made: http://www.recumbents.com/recumbents.asp

Actually nevermind, I'll compress that into a summary of options:
user posted image

I'm hitting depressing paralysis by analysis right now. Overwhelmed by options. So much to choose from I feel like if I choose anything wrong I'll have wasted the project, which feels like I shouldn't bother starting. Hopefully it's temporary.

Perhaps it will help to list all the things I have decided:

- Short Wheelbase. The long ones look like you're pedaling a church bench.
- Mid/High Racer. Not entirely sure where a "sport" and "racer" and such begins, but, I don't want to be too low for 2 reasons: Visibility over cars (hoods at least), and awkward chin tucking (neutral neck posture). I'm aware that there's a huge aerodynamic penalty for such, don't care.
- Straight or S-Pipe frame, probably. I see high end designs with all 3, so I don't think it matters much. It will depend on the most comfortable posture and ride height, if I need an S, I'll bend it to be one.
- Above Seat Steering, probably. I'll have enough crap going on underneath with the motor and gearing. Maybe I'll borrow one of each and see if one is significantly more comfortable than the other.
- RWD, gotta get the motor to the gears.
- 26" rear, 20" front. Easier to have a lower posture with and upright seat and cargo room. Have wheels and forks/frames of each already so that's no problem.
- Maybe front suspension, probably not rear. I'm not paying for it. Seat might have shock absorbers, but frame won't, too complicated and it creates chain tension issues, not what I want with a motor.

Whew. Okay, that helped.

I also just realized in a lightbulb/foreheadsmack moment... since it's a recumbent... the crank is too far forward for the motor to be turned by it, unless I use a long chain. However, on RWD the chain often needs a tensioning sprocket anyway. So, I think I'll put the motor sprocket and freewheel under the seat to do double-duty. That means I can only use my rear cassette gears for motor speed control. I'm not sure if that's okay or not. (If not, I'll have to put a chain and freewheel up to the pedals).

Next up, I should start sketching where the motor could go and figure out my seat position. Pain in the ass, I have a feeling it's one of those things I won't know until I build it and don't like it.
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Posted: March 03, 2012 09:55 pm
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Not a bike expert, but the last two (20"x2 and 26" rear & 20" front) look the all-around practical.

Long distance efficiency might be the underseat steering, if you're going X-country.

Cheers!


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