Inefficiency and Unreliability of Chain Drive system

[dequinox]

It boils down to gates quoting 99% in a test with enormous pulleys, and all practical application tests around ~95-97%, with the largest variable being the relative size of the smallest pulley compared to the pitch of the belt, as this is what has the big influence on the amount of sheer friction as the tooth on the belt settles into the groove in the pulley, and then gets pulled up out of it again.

Belts have some advantages and disadvantages, chains have some advantages and disadvantages. As used for a bicycle with a large reduction between motor and wheel, the limitations of pulley diameter on a belt drive system could mean requiring 2-3 stages of drive reduction, where a chain could be done in a single stage. Each stage's losses multiply together, so a 3 stage belt setup at 97% for each stage makes a 91% reduction system efficiency. Using a chain getting it done in a single stage (like my bike for example), means 1 x 98%, or 98% system efficiency.

WOW. That is pretty impressive efficiency for a chain-drive system... I have been operating under the assumption that I've been getting huge losses from running both a chain drive AND a brushed motor. For you to get 98% is pretty darn good w.r.t. the direct drive setups. What do they run do you know?

I finally quit whining about not having a watts-up meter, and did some calculations based on my general observations. I have usually noted an amperage draw of 15-20 amps on my bike going from 18-20mph, and thats a 24v system. I assumed an actual voltage of 25.4 as that is the typical resting voltage. I held the speed fixed for my calculation at 18mph since that seems to be my usual cruising speed on the flats. For 15-20A I end up getting about 21-28 wh/mi. I compared it with some values in the ES Garage spreadsheet and lo-and-behold I'm not in the top running but I'm actually not doing too bad!

That's been one of the hold-ups for me going to the LiFePO4 chemistry: assuming that I'd be wasting the extra capacity since my system was so inefficient. I won't be thinking that anymore.

AND Naeem!! Nice work my friend, your bike is always impressive to look upon, it is a work of salvage art!

 

[amberwolf]

For 15-20A I end up getting about 21-28 wh/mi. I compared it with some values in the ES Garage spreadsheet and lo-and-behold I'm not in the top running but I'm actually not doing too bad!

That's pretty good. My SUV-sized CrazyBike2 gets about 30-35Wh/Mile depending on speed and load; it's all chain drive using the bike's regular gear system (as is Naeem's).

 

[numberonebikeslover]

Naeem,

I thought the drivetrain was giving you issues, not the reduction. :

Oh Yes please, you got my point very right. the drivetrain that runs the wheel having the facility of derailing the chain over the mesh of chain gears always snap, most often when i'm derailing. Mr. amberwolf pointed out in this discussion further that it happens when i use the power of motor while derailing and he is very right about it. I'm suppose to use paddle power only while shifting from one gear to another. This is where the mistake lies.

If this is the case, are you going to use those cogs and belt instead of the chainring, derailers, etc? Those cogs look HEAVY. Mine are plastic for comparison.

the larger cog with 57 teeth will be used. the rest are just something that may come to of some use in later projects. It is heavy and i want it heavy duty. for gearing reduction, 57 teeth in-connection with 5 teeth on motor will be used, instead of chains and gears. The belt i've shown is just to share the idea thats all.

I hope not to overstep any boundaries and am totally entranced by your ingenuity, but it would seem to me that a person of such talent as yourself could take on at LEAST two e-bike projects. That being said it would seem to me that by placing parts in your hands, it would definatley add enormous value to both you and the community as a whole. I am only suggesting that you contemplate a second project that would allow us to collaborate with you. Of course, you know what is right for you. And you definately do not need help. On the contrary, I think you would be helping us!

My motive of doing this project is to do good to the humanity and produce a environment friendly transportation system. For this i intend to promot it further in my community by starting a small business of producing my own electric bikes with the resources already present in my country. It is my passion so why not it become my source of making my living, although i'm working in Education department but i don't feel my self fit there. To serve humanity in a better way i must do it till the end.

I thank all of you for your kind feelings for me. I will definately share my expenriences with all of you, and help promote this technology further into the future.

Yours Respectfully
Naeem

 

[numberonebikeslover]

Here is the diagrame of the final setup. I hope some of you will understand and any confusion will clarified by now. There is another thing of modification you will notice. All the bearings will be at the both ends of all shafts. This will again provide further strength and durability against any kind of load. Right now the bearings are enclosed in a cylindrical pipe. This all is held by welds in the middle, which is unstable against loads. While in the new setup it will be held at both ends and all the gearing stuff will be in the middle.

thank you all

yours truly,
Naeem

 

[dequinox]

For 15-20A I end up getting about 21-28 wh/mi. I compared it with some values in the ES Garage spreadsheet and lo-and-behold I'm not in the top running but I'm actually not doing too bad!

That's pretty good. My SUV-sized CrazyBike2 gets about 30-35Wh/Mile depending on speed and load; it's all chain drive using the bike's regular gear system (as is Naeem's).

Wow that isn't bad at all for that big beast! Perhaps the watt-hour usage for something like an electric bike only swings so wide? We see values the go from down to near 12wh/mi all the way up past 30, but maybe we aren't likely to see values outside that range for something the size of our bicycles.

 

[amberwolf]

Naeem, something you might consider (I am, now) for helping you shift without breaking things. What is described below is for his super-Civic car, but it is equally applicable to our bikes (perhaps not in timing or amount of force, but the idea itself is).

The shifter has a micro strain-gauge bonded to it. The moment it feels 5lbs of force tugging on the shifter, fuel and spark are cut for a 0.05second interrupt window. This is just enough to cause a brief moment of no torque loading to let it shift effortlessly and consistently, then hits it with full power again so quickly you hardly new it ever had an interruption.

So what you could do is put a switch on the shifter that is pressed as you shift. The switch would turn off the motor controller, like the "e-brake" lines do on commercially-available controllers, until it is released at the end of shifting.

If you have lever shifters this switch is VERY easy to make. Just put a leaf switch made of two strips of copper or springy metal, with an insulating strip about half of their length between them at the mounting end, on each side of your shift lever. This way when you start to press on the lever to shift, either up or down, it will short the switch leaves and disengage the controller.

If you have twist shifters then you could put a ring around the grip of the shifter made to hold a couple of leaf switches, and they would run parallel to the axis of the handlebars. Then when you grip the shifter to twist it, the motor would cut off.

To keep dirt out of the switches, just put little plastic envelopes over them. Even little plastic baggies would work, though they might require periodic replacement.

Since you might not have a brake-input cutoff, you might need to modify your controller for this. If you have already included "open-throttle" protection (so that the controller turns off if the throttle control becomes disconnected) then you can simply wire this switch in series with the throttle, but you would need to use a normally-closed switch instead of a normally-open one. That makes creating the switch harder since you can't just build it so the leaf springs close during shifting.

 

[numberonebikeslover]

Naeem, something you might consider (I am, now) for helping you shift without breaking things. What is described below is for his super-Civic car, but it is equally applicable to our bikes (perhaps not in timing or amount of force, but the idea itself is).

Thank you very much!
I had this in my mind from the start as I always thought that Motor’s power is a lot greater than human no doubt. My setup for throttle and break is in such a way that when I twist the shifter I’ve to remove my thumb from the throttle. Throttle has a springing reverse action and gets back to 10% of full throttle and motor’s power is entirely cut off but becomes even lesser than human paddling force.
I’ve learnt while being educated here that I usually commit a mistake of hitting the throttle sooner while shifting has not yet been done and this has been breaking things.
Break has a homemade switch which is so sensitive that as I touch the break-bar it shuts off the motor instantly while break is applied only when further pressure is put on break-bar. In-combination with break and throttle I save a lot of power while going through crowded situation.
What I’ve learned from my life time going through projects like this one I’ve learned following:
1) There is always another way around of a problem confronted.
2) There is nothing as impossible in science.
3) It is only the strength of desire one has in his/her heart that help one not to give up hope no matter how tough the situation is. (when the going gets tough, the tough gets going)

It gives me great pleasure to know the fact that my topic is becoming the source of transfer and sharing of priceless information and knowledge across the world. My dear friend alongwith all other respected fellows like you have indeed great contribution in this good work. I thank you all from the bottom of my heart.

Respectfully Yours
Naeem