E-bike project (RC mid drive system)

[panurge]

Hi Bruno

I look with interest at your build and mostly at your esc application in E-bike, with this kind of motor I guess you'll go with the 400amp one....please keep us informed on this...I think you have the chance to play with escs, that's the most critical part of an RC build.

Your frame looks good...seems you are going for a Pivot point concentric to the BB....notice that's not the best way to go for a single pivot if a good pedal feeling is still requested, well, obviously it solves most issues on the chain tension side....

As mentioned, Motomoto, with his top build, Is maybe the one that pushed the max power thru the gears around here.....there's a lot of difference In what you may push on a derailleur setup, I think, depends from the component's material and quality, mostly about cogs, chain, derailleur, freehub, bearings and Drive sprocket.....anyway it is not a bad Idea, in the gearing plan, to use a 13t or even 14t or 15t as the smaller cassette cog (driven by the motor, at least). This should increase critically the power limit.
Buon lavoro :wink:

 

[spinningmagnets]

Bruno, I will understand if you want to try something new, but please be cautious, as mistakes can be expensive. I do not understand induction/inductance in a motor yet (so far I have not had the need), but I remember it was the death of some interesting motors that seemed to have great potential.

 

[mauimart]

Hey crossbreak!

You can not put 8000Watts through a bicycle drive train.

Any idea on the max power and/or torque you can put through a bicycle drive train?
Posts, XLS's, links to read..?
Thanks.

I don't know what the max power is but I routinely run over 3000W (battery power) when shifting at WOT through my standard bicycle drive train. Chainring sprocket is 35T and rear cassette goes down to 12T. See video at 4:45 for example shift from 15T to 13T.

[youtube]8mH7KN_vb0I[/youtube]

 

[flyinmonkie]

Interesting, which cassette do you use and how many miles does it last?

It is just a shimano, nothing special cassette. I went down to a 13 tooth, but anything smaller skipped. The chain is just an HG shimano as well. So all just middle quality bike components.

I have over 1000 ks on the bike now, but the sprockets are probably closer to 500 or 600 ks. I started with used sprockets and got 400 or 500 ks on them before I had to change them. Not sure how much use they had before I used them.

Clay

 

[fizzit]

I've been using a 8 speed Shimano Megarange cassette for a few hundred miles and it's still looking pretty much like new. The Megarange is great for a mid-drive because the largest sprocket is 34T and 5th gear is 17T so you can have a full 2:1 ratio in four shifts. It's a lot easier on the chain too because it has to bend laterally a lot to reach the far ends of the cassette, if you're using the full gear range.

 

[crossbreak]

Received reply from the Conway E-Rider Team:
(translated from German):

The [stated] 1100watts are maximum continuous power. An increase up to up to 2 kW would be technically possible, but not under warranty.

how much power one can push through depends on how the motor is geared to the crank. If you gear it way to fast for pedaling, like mauimart shows us in his moped video, one can push a lot more through a derailleur system than on a bicycle.

The 1200Watts may be a limit for a 44T/12T overdrive, if the bike is geared for the normal 85rpm crank cadence.
1200Watts @ 85rpm mean 135Nm or 1500N chain pull
2000Watts @ 85rpm mean 225Nm or 2500N chain pull

Chain strength should not be used more than 1/6 at average power. A good derailleur chain can have 10000N tensile strength (a cheap one about 7000).
So the guys who build the E-Rider do just fine.

The stated 4000W+ are Bullshit, since this is no e-bike, it's a motorcycle. Can't compare apples and pears. 4000Watts @ 255rpm should work fine, no offense.

 

[flyinmonkie]

The stated 4000W+ are Bullshit, since this is no e-bike, it's a motorcycle. Can't compare apples and pears. 4000Watts @ 255rpm should work fine, no offense.

You said bike chain can not handle over 1200w. That had nothing to do with if it is a bike, moped, motorcycle, airplane, helicopter... You are wrong, admit it cleanly. Bike chain can withstand more than 1800w. I do it everyday. I even do more than 1800w when I pedal assist up large hills. I don't run my motor through the crank, but others do and see more than 1800w on bike chain all the time. I personally have seen 5000w peaks on my last set up and have not had a problem with the bike chain or dérailleur.

If you are using a company that manufactures and sells bikes, they are only going to tell you figures that with be well within the actual limit so they don't have to warranty product all the time. They may not even actually know the limit as they have never found it. People on this forum are great at finding the limit of stuff, so I believe what certain people on the forum say from their experience over any manufacture.

Sorry to git off topic, but false statements should be corrected. If you want to build what crossbreak would consider a motorcycle out of a bike than it can be done. And bike chain and a dérailleur can handle the power. Most people on this forum will consider it an ebike as long as it has working pedals and resembles a bicycle or was built on a bicycle, no mater what power or speed you go. Not trying to start a fight crossbreak, you often have lots of good info, but plenty of people here have been putting lots of power through bicycle chain for a long time. Have bit of a look around at the power levels some of us mid drive people are using, even if you do not consider it an ebike, it is still using bicycle chain.

To the original poster, check out repumpence and aussiejester's threads for ideas and limits of what can be done with RC motors. recumpence is a bit of an authority here on how to make them work. aussiejester has been down that road as well and made a bike that works fantastic with an RC motor. Another place to look is thud's stuff. It has been well tried and documented on what works and what doesn't. If you do not set the gearing up well, and if you do not know the limits of the RC motors and controllers (if you use one), it can be an expensive way to go. Many have tried and been very frustrated. Basically, if you want an off road bike, at this point stay away from RC motors and controllers. If you want a street machine that is fast and powerful, then speed the time to get it right and they are awesome. Just don't lug slowly up any hills with an RC controller.

Clay

 

[gwhy!1]

To the original poster, check out repumpence and aussiejester's threads for ideas and limits of what can be done with RC motors. recumpence is a bit of an authority here on how to make them work. aussiejester has been down that road as well and made a bike that works fantastic with an RC motor. Another place to look is thud's stuff. It has been well tried and documented on what works and what doesn't. If you do not set the gearing up well, and if you do not know the limits of the RC motors and controllers (if you use one), it can be an expensive way to go. Many have tried and been very frustrated. Basically, if you want an off road bike, at this point stay away from RC motors and controllers. If you want a street machine that is fast and powerful, then speed the time to get it right and they are awesome. Just don't lug slowly up any hills with an RC controller.

Clay

Just to chip in I have used bicycle chain upto and slightly over 4kw without issue and lots of people have on this forum.

AJ and recumbrance have both setup very good bikes based around the rc esc CC but they both know very little about sensored setups ( which makes a rc setup more reliable, better control and with slightly better performance ( my option ) ) one of the people to look up is thud. Off road bikes are ok just need a little more attention to detail, then a very good off road rc setup can be achieved.

 

[boostjuice]

FFS! Watts units means nothing in this debate/context. It's gearing specific which leads to > torque > Newton (N) or pounds (lbs) of chain pull force (tensile loading).

Crossbreak is on the right track.

Bicycle chains typically range from peak working load ratings of ~1200N (bushingless derailleur chain) > ~1500N (bushed BMX chain). Tensile Breaking strength is higher, but is not worth factoring for as the pitch will 'stretch' too quickly for acceptable service life (quickly chews sprockets to match) long before approaching this limit .

As Crossbreak said, ANSI standards suggest 1/9 > 1/6 of peak working load is a good service factor for decent chain working hours.

 

[Miles]

Watts are all that count here, I'm afraid... Input watts as "pumped" through the Cycle Analyst, to be specific

 

[brunotollot]

Bruno, I will understand if you want to try something new, but please be cautious, as mistakes can be expensive. I do not understand induction in a motor yet (so far I have not had the need), but I remember it was the death of some interesting motors that seemed to have great potential.

Thanks for your suggestion, and thanks to everybody also. I plan to use a lot of heavy duty parts, no commercial, and some will be custom made. Chain, crank etc need to be very strong. I know that them are not designed for application like this. Is nice have lots of info and suggestion. Many thanks. I will post everything step by step. Just need to swap my time between wife, business, project, new born baby... :lol:

Hi Bruno

I look with interest at your build and mostly at your esc application in E-bike, with this kind of motor I guess you'll go with the 400amp one....please keep us informed on this...I think you have the chance to play with escs, that's the most critical part of an RC build.

Your frame looks good...seems you are going for a Pivot point concentric to the BB....notice that's not the best way to go for a single pivot if a good pedal feeling is still requested, well, obviously it solves most issues on the chain tension side....

As mentioned, Motomoto, with his top build, Is maybe the one that pushed the max power thru the gears around here.....there's a lot of difference In what you may push on a derailleur setup, I think, depends from the component's material and quality, mostly about cogs, chain, derailleur, freehub, bearings and Drive sprocket.....anyway it is not a bad Idea, in the gearing plan, to use a 13t or even 14t or 15t as the smaller cassette cog (driven by the motor, at least). This should increase critically the power limit.
Buon lavoro :wink:

Grazie per il buon lavoro..

 

[flyinmonkie]

Thanks gwhy, I though I mentioned thud, but may have just thought about it and forgot to. Your stuff is also a place to look for sensored RC ideas, as you have done a lot of work in that area as well.

I agree that when it comes to testing the strength of chain, then tensile strength is the measurement. But when using an electric motor to apply that force, we need to know what sort of power in electric motor terms applies that sort of force. Hence what wattage can be run and not break a chain.

brunotollot... have a look at threads from the people suggested by others and myself. A lot of work has been done already on what you want to achieve. It might make your process easier and cheaper. Keep at it, we all like to see ideas built upon and improved or tweaked to be better or different.

Clay

 

[recumpence]

I agree that RC equipment can be a bit temperamental. However, if setup properly, they can work well. If you are careful not to run at low throttle settings and high load, you will generally be fine. Also, make sure the controller is setup properly for your application. I am familiar with HV160 controllers. I can help you with settings for them. I am not familiar with others, though.

Just work your way up through the settings of your controller to get a feel for it before you run it hard. If y ou decide on a 160, let me know. I can help you with the settings.

Matt

 

[Thud]

Hello bruno,
I think you need to look at your gearing set up & decide one of 2 options:
#1 treat it as a ellectric powered bike that has pedals to get you home when the batteries are dead....or
#2 have a motor assited pedal bike (that the motor asists the rider by matching his pedal cadance)

I have built severeral of each design....& either is fine if you know what your results are going to be.

none of my track bikes have any usefull input from the pedals...they are geared tall & optomised for maximum speed on a road corse. (none of those are a bottom bracket driven set up either)

but for a bicycle that makes you feel like superman, I recomend to everyone to try to gear to match your fastest pedaling ability. especialy if you have any intention of going off road. (I have built BB drives for this application)

I re-wind my 80mm motors to make them more controllable with sensored controllers (i know you have your line of controllers so forget that )
I do know your controllers will thank you for the lower gearing & your bike will still be way faster than is reasonable on any shared trails.
so think about getting your motor to drive the pedals at 100ish rpms...(thats 80-1 total reduction on a drive i am currently building for a member here)
take this free advice for what its worth. :lol:
looking foward to seeing the controller luks is testing.....& seeing this build progress.
have fun
T

 

[flyinmonkie]

Hey Matt and thud, thanks for chiming in. Great advice, as always you two are on top of it.

Clay

 

[brunotollot]

HI MATT. HI THUD. Nice to meet you and thanks very much for your advice. I will ..

 

[boostjuice]

I agree that when it comes to testing the strength of chain, then tensile strength is the measurement. But when using an electric motor to apply that force, we need to know what sort of power in electric motor terms applies that sort of force. Hence what wattage can be run and not break a chain.

'Wattage' rating is only useful if combined with knowledge of;

- The motor's characteristic power curve (Power over what nominal RPM range? and therefore what nominal and peak torque > chain force?) [Will depend on motor type. Small/Fast/Low torque - or Large/Slow/High torque design?]

- Which reduction stage? > Multiplied input torque at that stage? Is this chain type appropriate for this level of tensile force in this particualar reduction stage with a particular RPM range and particular smaller sprocket diameter [accounting for chordal action]? (chain pitch, driving sprocket diameter as well as tensile rating all matter here)

So what I'm getting at is that Power is a variable that is too far removed from something we can compare chain performance over a wide range of eBike builds.

If someone says "My derailleur chain can handle 2000W in my mid-drive build" people need to know alot more info to use that as a data point in the comparison of longevity of that chain type that may be under different loading/speed in a differently geared build that they are brewing plans for.

To calculate chain force for a given reduction stage and get a feel for the relationship between Power, RPM & Torque use this or similar.
http://www.magtrol.com/support/motorpower_calc.html

To calculate chain force for a particular reduction stage (motor/jack-shaft), divide the torque length unit (ie '1 metre' for Nm/ '1 foot' in ft/lb) by the driving sprocket's pitch radius.

Here's a personal example for one of my now dismantled BB drives.

Motor - Big Cyclone 2400W,
Peak torque near stall = 9.8Nm (@ factory standard controller current limit/voltage)
Torque at max output power at ~2200RPM = 7.85Nm (~2400W electrical pwr in/ ~1830W mechanical pwr out, ~76% efficient)

Reduction between motor and freewheel crankset = 31.27:1. Nominal torque at freewheel crankset was therefore ~250Nm ignoring speculatable drivetrain losses.

Rear 9psd cluster was driven by a standard 60T bicycle chainring (0.5" pitch) = 121.4mm pitch radius. Therefore the chain tensile force was (250N * [1m/0.121m]) = 2059N nominal on chains rated for peak working loads of 1200N. It makes sense why 1830W of mechanical pwr stretched many 9spd derailleur chains to the 1% replacement mark in <300km of mileage, all because I wanted to be able to add pedal assistance at 75rpm crankset cadence.

Point is: Wattage is context specific, so lets just all compare chain force figures which isn't that difficult to calculate.

 

[flyinmonkie]

boostjuice... true true, fair enough. Same goes for saying it can't handle a certain wattage. There are lots of variables that can effect what forces the chain sees compared to the watts seen coming through the meter. Be nice to say in simple terms an idea of wattage that can be handled by bike chain when first putting ideas on paper and planning a new build though.

Thanks for laying out the variables and the effect of them boostjuice.

Clay

 

[AussieJester]

With regards to the bicycle chain ...I use half link BMX chain..
I have regularly recorded over 10 000 watt peaks on the Castle hv160
Software... Jm2cw :wink:

KiM

 

[brunotollot]

I guys.
Have a look on my friend Richard project. I think it is awesome. 

http://endless-sphere.com/forums/viewtopic.php?f=35&t=47176&p=691532#p691532 Many thanks...

 

[boostjuice]

With regards to the bicycle chain ...I use half link BMX chain..
I have regularly recorded over 10 000 watt peaks on the Castle hv160
Software... Jm2cw :wink:

KiM

Totally understandable Kim. Your running direct drive to the wheel. Chain force is therefore much lower than a Mid-drive build.

No rise for ya captain pot-stirrer :wink:

 

[AussieJester]

haha nagh, was just chipping in wasn't meant as a stir...

KiM

 

[brunotollot]

Hi, some pictures of the project. Me and Richard will start machined the parts when the bike will be assembled.

 

[motomoto]

You can only put so much torque on a chain, however you can spin the chain faster and transmit more power that way. When I did my 66 mph
run I put a huge pulley on the motor to spin the crank sprockets at 600 rpm. Torque times rpm equals horsepower. And lets face it, when you
are pushing a lot of power you do not need any pedal cadence, so spin it up.

 

[motomoto]

And by the way, your Solidworks design looks bitchin' !!!

It is the 'thing' to put powerful setups on bicycles, but I think you will find out that you are going to need
more wheelbase to make it ridable. You will get tired of having to lean over the handlebars.