How do You Make a Power Assist Bike?

[Beagle123]

About 5 years ago, I rode an e-bike made my mercedes (?) that was really great because the pedals controlled the throttle. When you peddled harder, more power was sent to the wheels. When you rode it, it felt perfectly natural. In fact, you feel like superman because you can easily pedal to 20+mph with little effort.

Is there a way to get this feature on an ebike? The guy at solarbbq sells a "torque sensor." Is this the component that does this? Do you need a special controller? Are there other bikes on the market that are similar?

Please give me some links.

Thanks

 

[Toorbough ULL-Zeveigh]

This is central to how the Bionx kit worx, but there are lots of others.
Google 'pedalec' & as I understand it in Britain at least (& perhaps the rest of Europe as well) this type of ebike is the only kind legally permissable.
Maybe members from the other side of the sphere can confirm this.

Another thing I've noticed is that the first posting from people with pedalecs is wanting to know how to disable it.
You may be the first that wants to go the other way.
I guess it might be nice to have the choice to switch back & forth as needed (it's always good to have a choice) & not have it forced down your throat by law as the only way to go.

 

[monster]

yer pedelec's suc, but that maybe because they are usually on really weak bikes, and with a slow bike you want full speed all the time. it may be different on a c-lyte 5x.

also because of build quality issues some of the Chinese controllers have a lag of a few seconds between the torque sensor and the power output with the effect that the power is still on when you are trying to slow down!! with a 200w bike this is a waste of batteries but with a c-lyte X5 this could be deadly.

 

[safe]

There are a lot of reasons to do things like this.

The bottom line is that electric motors running at low rpm with high torque are simply terrible performers as far as efficiency.

However, I know that for my bikes that pedaling is not something you want to do all the time. (it's only for slow speeds... I don't want to risk pedaling at high speeds)

 

[Beagle123]

I found this link to pedalecs:

http://www.extraenergy.org/main.php?language=en&category=products&subcateg=66

They do look expensive and slow. The one I rode was really smooth and effortless. However, it did have a very small battery. In fact, most of these bikes have tiny batteries.

I'd like to use one of these to get a small amount of exercise when I travel. It seems perfect to me because as you ride, you naturally want to go faster, so you pedal a bit harder etc. So its tricking you into exercising.

I found this one on ebay:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=290189436059&ssPageName=STRK:MEWA:IT&ih=019

It looks stronger. Its 48v, it says it has P.A.S. technology. I wonder if its got the smooth feel? WHat do you guys think?

 

[TylerDurden]

There are probably a few fun ways to rig your bike for PAS, the one thing I'd suggest is putting the control (for % required human input) somewhere that forces you to stop and get off the bike to change it.

That will force you to keep pedalling, unless you're willing to take the time to stop.

 

[recumbent]

We have this feature built into the Bionx control panel.
You simply select 1-4 on the panel, from weak to strongest assist, I always pick #3. The surge when pedalling is just right, not too much yet plenty enough to make you feel like THOR, or Superman, feels inspiring. if you want you can just push the thumb control for regular throttle. The pedal assist is essentially always on and instictivly used because pedaling to start is always a good idea anyways.
It all works so wonderfully, now if I can just get another 12 volts and 10ah it would be perfect.

 

[Dee Jay]

Hi Beagle123

I have the same PAS on my Crystalyte Journey Kit. It consists of a small plastic wheel with 5 magnets embedded on one side, and a separate magnet sensor with mounting bracket and harness that connects to the controller. The sensor triggers the controller to give about 2 seconds of full-on burst with each pass of a magnet. For safety *in case the pedal was accidently bumped* my system does not trigger unless I'm pedaling at 5 kph,

The sensor is installed on your bottom bracket and the magnet wheel next to it rotating with the crank. With my system, I can install it on either side of the bottom bracket as my sensor can be repositioned to point the opposite direction or I can reverse it with a jumper inside the controller. The odd thing about my Giant Revive is that the left hand side of the bottom bracket does not have an edge or lip to mount the sensor so I'm forced to use the right side, but there isn't much space for the magnet wheel, even after doing away with the chain-guard and its mounting bracket...so I ended up cutting small tabs of aluminum from a can to use as shims so that the crank didn't press in too far against the magnet wheel when the crank is tightened down.

On the lowest gear, you pedal faster - triggering the sensor more frequently - getting power . Then of course the higher the gear - the less frequency - less power but whatever gear you're on things even out between your effort, gear, and given power, or at least in theory.

It's not a great system because unlike the throttle with gradual increase of power, 2 second bursts of full-on power is not very efficient. It would be nice to have the power adjustable with a knob or multilevel switch, especially for light-weights like me.

Even when you use the ebrakes to regulate or cut-out the power, you'd have to make sure the 2 seconds had passed, otherwise you'll still get that full-on burst as soon as you release the ebrake. God help you if you're on a 5x motor!

I wouldn't recommend using this system in crowded streets, but it's actually really cool at high speeds. I switch from PAS to throttle when stopping at intersections because I need that instant start of the throttle when starting from a full stop, especially when I forget to gear down and you got a dump truck blaring his horn up yer bum :x . Unfortunately, the switch was inconveniently built onto the controller, not the throttle. It was really dangerous trying to feel around for that switch under my saddle at 24 kph ! So I disconnected the wire from the original switch and extended it up to my throttle and to a new on-off button. Life is good... 8)

My Journey Kit controller w/PAS is only 36v 20a, I wonder if I can get 72v 40a with PAS...

Golden Motors hub kits use the same system except their sensor is a bit bulky while Crystalyte's is nice and slim and flexible with installation.

The torque sensor is a lot more complicated because I believe you have to replace your original crank, but don't quote me on this.

Something you all probably know by now, the Mercedes uses a Sanyo geared hub with sophisticated Japanese electronics for that smooth and effortless PAS experience. Something you'd probably never get on Chinese PAS. Am I wrong?

 

[Beagle123]

Thanks for the info Jay! It really helps.

The torque sensor is a lot more complicated because I believe you have to replace your original crank, but don't quote me on this.

Take a look at the ebay auction I posted above. It says:

Our unique P.A.S ( pedal assist system ) can be used on bikes that have a removable pedal shaft. This will give equal assist when pedaling your bike for greater range and more effortless riding.

Do you think this is the same system you use? It sounds like it must work with the crank in some way.

The magnet sensor you describe doesn't sound that good. It seems like it would be inexact, so it would lunge/jerk a little.

If you ever had the opportunity to ride the mercedes bike, you'd be really impressed. It is totally seamless. When you pedal, it goes. No noise. Perfectly smooth. And the power is exactly porportional to your peddling power.

I think these are an amazing invention. If one of us (you) were to make a 10ah lithium version where 20% of the power comes from the peddles, it would be a great vehicle. These pelalecs use tiny 4ah batteries and 250 watt motors. I want to get a 500 watt version.

Does anyone know how to get the sensor that detects your peddling pressure?

 

[Dee Jay]

Beagle123! You quoted me! Moderator! Moderator!

:wink: Glad to be able to contribute in some way, Beagle.

Yes, this is the same system, but now that you mention it, the controller response may vary between manufacturers so it's possible that other manufacturers' PAS controllers may not lunge, or may cut out the power completely when ebrakes are used, but the disadvantage of this is you would have to wind back up to 3 to 5 kph to get the burst again. This is probably why Crystalyte kept the full 2 seconds even after ebraking.

As for "bikes that have removable pedal shaft"... at first i thought you may have to replace your crank with a torque sensor, but it just means you need to pull out the crank in order to install the magnet wheel and sensor.

"greater range" is true when pedaling with or without PAS

"and more effortless riding" just means the throttle will be one less thing to worry about and you can relax your wrist and shoulder.

I've briefly test ridden a Japanese hub motor called Aero Assistant and Yamaha PAS. They are as smooth and seamless as you described, and you're right, they are low powered at 3.7ah, They're not made for speed, but they have great range, 30 to 60 km / 20" on economy mode.

http://www.yamaha-motor.jp/pas/lineup/pas_city-x/index.html

My "DCR" Dual Crystalyte Revive has economy mode also, except it's not like a sophisticated electronic transmission. It's an "SLT" system, Super Low Tech. My homemade switches act more like a manual transmission. But 4011 really does save energy, especially when used with the throttle's gradual increase of power. The dead weight of an extra motor is negligible once you get rolling on the flat, IMHE. Hopefully in the near future when motors get lighter and batteries gets stronger, this will be true for hills.

What I'd really like to invent, if it hadn't already been done, is an electronic switch to smoothly transfer power between my motors based on kph by the use of a magnet sensor detecting the same magnet used by my cyclometer. OR! Or somehow hack into the cyclometers speedometer for direct reference. I'd probably need a jolt of lightning on my forehead or divine intervention to achieve this... :?

As for pedal pressure, the torque sensor crank might be the answer. I'd like to read a user's review of this...

J

 

[TylerDurden]

One ghetto way to PAS:

Install a spring-tensioned jockey wheel on the chain's high side.

Connect a pot to the tension-arm that intercepts the throttle.

When the chain tenses, the pot could add more voltage to the throttle.

"These and other features, aspects and advantages of the above will become evident to those skilled in the art..."

 

[recumbent]

Thanks for the info Jay! It really helps.

If you ever had the opportunity to ride the mercedes bike, you'd be really impressed. It is totally seamless. When you pedal, it goes. No noise. Perfectly smooth. And the power is exactly porportional to your peddling power. [/size]

The Bionx goes through a 2 second cycle to make the first power delivery smooth after one complete crank revolution to prevent accidental run-away. The first cycle has a smooth delivery from less to most power in one second and not lurch forward either, similar as you describe.
The plastic cylinder with magnets and a pick-up sound like a good concept.

 

[Drunkskunk]

TylerDurden's idea would work pretty well I think. probably far better than the POS PAS that comes with most kits like the journey.

Instead of a pot, I would use a modified C-Lyte throttle, with it's hall sensors, and a small averaging curcuit to filter out the vibrations on the chain.

Actualy, I think you could build something like this pretty easy to fit any motor, and turn any bike into a PAS.

As for me, I'm keeping my throttle.

 

[Dee Jay]

POS...

tee hee hee, nice one Drunkskunk

As for me, I'm keeping my throttle

PAS is underrated, I think.

Pedaling is very intuitive to cyclists... bi-cyclist. But not motor-cyclists. Motorcyclists love their throttle. I used to ride a motorcycle so there are times I tend to treat my DCR like a skinny motorcycle. I have to make a conscious effort to remind myself it's an Ebike, not a motorcycle. But to a bicyclist, adding a ~zoom~ to the bicycling experience is an amazing sensation. I can only describe it similar to walking on those airport people-movers *whateveryacallit*. You don't have a throttle in mind... you're just walking at a normal effortless pace (in our case pedaling), yet double or triple the normal speed. In silence. It's a dreamy experience, in my bicyclist mind-set.

I'd like to use one of these to get a small amount of exercise when I travel. It seems perfect to me because as you ride, you naturally want to go faster, so you pedal a bit harder etc. So its tricking you into exercising.

Very true, Beagle. There is a snowball effect to the Crystalyte PAS experience: the motor helps - you help the motor - motor helps you more - you help the motor even more - on and on and on.... equivalent to calisthenics, the only difference is you're actually getting somewhere, and fast! Stationary cycling exercise is boring because it goes nowhere, then you're tired! With PAS, at the end of the day, you've gotten some exercise without even thinking about it. And I actually started developing riding leg muscles which wasn't really part of the plan because I built my bike with only cheap transportation in mind, not exercise.

Crystalyte POS... I mean ~PAS~ has potential to be refined. Maybe less magnets or potentiometer to tone the power down, and/or ramping the power. Beagle, you might be able to rig up the Torque Sensor with it.

J

 

[Beagle123]

But to a bicyclist, adding a ~zoom~ to the bicycling experience is an amazing sensation. I can only describe it similar to walking on those airport people-movers *whateveryacallit*. You don't have a throttle in mind... you're just walking at a normal effortless pace (in our case pedaling), yet double or triple the normal speed. In silence. It's a dreamy experience, in my bicyclist mind-set.

I couldn't have said it better myself. That's exactly what it feels like.

But I think the biggest benefit to PAS is the added efficiency. When you ride a bicycle, you naturally manage your enery output. You don't thrust at full power from a dead stop, and you downshift of hills because YOU have to provide all the power for the bike. Compare that to how we all waste energy on our ebikes.

We're always posting about methods to manage our batteries' power and limit current to increase efficiency, but we already have a "Built-in" power managenet system in our brains. It's called "riding a bike." So using a PAS system could make you dramatically increase your batteries power AND add power to the wheels.

In ebikes, the PAS technology can really improve speed/range and efficiency even MORE than the energy you add by pedaling. Imagine if you made a PAS bike where it exactly multiplied your pedaling 4 times. That means that if your power output to the pedals is 100 watts, the motor would add 300 watts. Compared to a bike that was entirely electric powered, you should get more than 25% more energy from the PAS bike because the batteries like being drained slower.

Also, if the PAS system were to assist less at slower speeds where the motor is less efficient, and more at faster speeds where the motor is 80% efficient. So you could have the controller multiply by 1.5 times at the slowest speed--up to 3 times at faster speeds. So by using more human power that's more efficient at slowers speeds, you could increase your electric efficiency by perhaps 10-20%. So the added efficiency numbers could look like this:

Power added from slower battery discharge = 7%
Power added from using more human power at slower speeds = 10%
Power added from managing throttle like you ride a bike = 15%
Power added from your effort = 25%

Total = +57% !!!

I think those are very realistic numbers.

 

[iberkt]

I found this P.A.S. system. It is used with the Cyclone kits. I don't know if it would work for your set-up but you might want to take a look.

http://www.cyclone-tw.com/pas.htm