# Bicycle chain tensile strength



## thinkcooper (Jan 5, 2005)

I'm fabricating a very heavy (1500 pound) four wheeled, pedal powered vehicle project. It will be powered by two riders, with very low gearing, and only needs to reach crawling speeds of 5mph - so gearing low will help the riders move this heavy load. A few folks on the team are nervous about using a bicycle chain drive train. To help allay their fears, I'm looking for tensile strength data for common bicycle chains. I've used 1/8 BMX chain in the past for some heavy duty pedaled projects, and it works fine, holds up to any amount of force a human can generate, and is readily available.

Any assistance with tensile strength data or any other load to failure chain data would be greatly appreciated.

A quadricycle reference to show what we are using as an inspiration:


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## Reynolds531 (Nov 8, 2002)

Googling bicycle chain tensile strength gave answers around 1000 kg. 

http://www.taipeicycle.com/online/j...Type=ProductList&cateoid=-26912&cateid=243004


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## thinkcooper (Jan 5, 2005)

Thanks for that link - I'd found similar general data as well from a few Asian manufacturers- I'm hoping to find some more specific information, in the best case, a chart comparing branded 3/32, 1/8, etc. in various materials (steel, stainless, ti). We need to be able to get the sturdiest chain made on this new heavy weight quad.


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## GScot (Feb 7, 2005)

check the fixed gear resources sticky. Seems like some of the track vendors had compiled data on the merits of various chain sources. There are some track chains that could pull a car.


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## MR_GRUMPY (Aug 21, 2002)

BMX bicycle chain (#43) has an average tensile strength of 2120 pounds. Your idea might work with a 5 speed chain, but I doubt if a narrow 7,8,9, or 10 speed chain could last any amount of time before you would see chain breakage.


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## benInMA (Jan 22, 2004)

You're not supporting the weight of the vehicle with the chain. Chain needs seem to be more about power output then weight. (e.x. Motorcycle chain sizes are recommended by engine size & torque output, not weight.) BMX chains are just bigger AFAIK to get more durability.. they've got the loads spread across a wider chain so they wear more slowly.

You're only going with the power of 2 cyclists, if they're not trying to do a time trial you might be fine.

The smallest motorcycle chain you could buy might be the next obvious step up if you want huge durability & strength but you will be adding a ton of weight for the huge sprockets & most MC chains have O-rings on the pins which add quite a bit of friction to get long life. You'd also probably have trouble getting the gearing set up.


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## Reynolds531 (Nov 8, 2002)

thinkcooper said:


> Thanks for that link - I'd found similar general data as well from a few Asian manufacturers- I'm hoping to find some more specific information, in the best case, a chart comparing branded 3/32, 1/8, etc. in various materials (steel, stainless, ti). We need to be able to get the sturdiest chain made on this new heavy weight quad.


How many different gear ratios do you need? You could go with industrial sprockets and chain for the final gear reduction and have an 8 speed chain and deraileur system for an initial gear reduction. The 8 speed chain wouldn't see the high tension. Your 8 speed gear range could be 30:11 down to 30:34, then your final reduction could go as low as you want.


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## nonsleepingjon (Oct 18, 2002)

thinkcooper said:


> I've used 1/8 BMX chain in the past for some heavy duty pedaled projects, and it works fine, holds up to any amount of force a human can generate, and is readily available.


I'm not any sort of mechanical engineer, but I think you have the concept right: the chain needs to hold up to the power of the engine (humans in this case) and not the vehicle weight. Looks like there's general agreement on this from the other posts. Since you're gearing it low, I would think a bike chain would hold up fine. Now, if it was geared high and both people were standing on the pedals at the same time then it would be a different story. 

Looks like a fun project - keep us updated.


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## thinkcooper (Jan 5, 2005)

You guys are comfortably confirming my sensibilities. A BMX chain, with a ~1000 kg tensile strength is more than strong enough to stand up to a cyclist's output. I'd speculate comfortable output to range between ~100-200 watts for an average quad rider, that doesn't really train and is just puttering around on perfectly flat terrain. Nowhere near the outer strength ranges of a 1/8" BMX chain.

As for gearing, the quad in the picture above current runs a 44 tooth front chainring, driving a six speed 14-28 freewheel on an intermediary jackshaft, with a second 14-28 six speed on the final drive shaft. The vehicle above has hauled weights around 1000 pounds, with two riders, with no issues. Having the dual freewheels for each rider allows for a lot of variability for gearing, and allows a weaker rider to pedal at their own comfortable level.

An advantage of sticking with cycling based chain, freewheels and deraillers is that the parts are cheap, easy to find and scaled well to our project.

The new quad we're working on will be a "home base" for a set of six-eight self powered, autonomous, spherical robots linked together with wifi communications. The base for the swarm of robots will allow them to be transported to a performance location, and then they can roll out of the base, and do their "swarm dance". Cleverly, the robots are controlled with a gyro sensored wifi wand, so anyone can hold this wand, swirl it around and all of the 24'' tall robots respond in real time. Really.


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## Bocephus Jones II (Oct 7, 2004)

thinkcooper said:


> You guys are comfortably confirming my sensibilities. A BMX chain, with a ~1000 kg tensile strength is more than strong enough to stand up to a cyclist's output. I'd speculate comfortable output to range between ~100-200 watts for an average quad rider, that doesn't really train and is just puttering around on perfectly flat terrain. Nowhere near the outer strength ranges of a 1/8" BMX chain.
> 
> As for gearing, the quad in the picture above current runs a 44 tooth front chainring, driving a six speed 14-28 freewheel on an intermediary jackshaft, with a second 14-28 six speed on the final drive shaft. The vehicle above has hauled weights around 1000 pounds, with two riders, with no issues. Having the dual freewheels for each rider allows for a lot of variability for gearing, and allows a weaker rider to pedal at their own comfortable level.
> 
> ...


Jeesus...and here I am having problems with realtively simple bike projects.


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## thinkcooper (Jan 5, 2005)

Bocephus Jones II said:


> Jeesus...and here I am having problems with realtively simple bike projects.



All I'm delivering is the "bike" part of this project. :thumbsup:


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## thinkcooper (Jan 5, 2005)

Here's a link to the robotic portion of project's website for the curious, tech details are in the PDF proposal:
http://orbswarm.com/


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## wim (Feb 28, 2005)

The German Industrial Standard sets minimum breaking loads for standard bicycle chains at 8,200 Newton and at 10,000 Newton for derailleur bicycle chains. The industry follows these standards pretty well.

A strong rider can put about 1,500 Newton propulsive force on a pedal which, depending on the gearing, can translate into a propulsive torque of 1,000 Newton-meter. That's a huge number, even compared to a lot of cars. Because internal combustion engines are not limited to a "cadence" of 120 rpm or so, propulsion can flow from a very small to a very large gear—the reverse of the bicycle.


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## Reynolds531 (Nov 8, 2002)

thinkcooper said:


> You guys are comfortably confirming my sensibilities. A BMX chain, with a ~1000 kg tensile strength is more than strong enough to stand up to a cyclist's output. I'd speculate comfortable output to range between ~100-200 watts for an average quad rider, that doesn't really train and is just puttering around on perfectly flat terrain. Nowhere near the outer strength ranges of a 1/8" BMX chain.
> 
> As for gearing, the quad in the picture above current runs a 44 tooth front chainring, driving a six speed 14-28 freewheel on an intermediary jackshaft, with a second 14-28 six speed on the final drive shaft. The vehicle above has hauled weights around 1000 pounds, with two riders, with no issues. Having the dual freewheels for each rider allows for a lot of variability for gearing, and allows a weaker rider to pedal at their own comfortable level.
> 
> ...


I think that it is force, not power, that you need to calculate. The maximum force on the drive chain will be when the vehicle is in the lowest gear and both riders are applying maximum force. this is what would happen from a stop when pulling a maximum load. Since rpm is zero, power is zero, but force is maximized.


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## JP (Feb 8, 2005)

When I was a kid they had matched sprints on Friday nights at Trexlertown on tandems. I'm talking two world class sprinters on a tandem track bike. If those guys couldn't break a chain, there is no way you will break it putting around, but I wonder what a "real" engineer would say.


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## StillRiding (Sep 16, 2006)

I'd be *FAR* more concerned about the brakes on that thing than I would the chain.


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## thinkcooper (Jan 5, 2005)

StillRiding said:


> I'd be *FAR* more concerned about the brakes on that thing than I would the chain.


The fully laden vehicle will be operated in an open desert playa, getting up to a max of 5-8 MPH. But it will be needing to navigate in and out of more densely populated camp areas, and it will likely be hauled to events such as next year's Maker's Fair and a few other public urban festivals.

The brakes on the quad above are band/drum brakes. A very simple, centuries old design lifted from horse drawn carriages. We'll probably integrate a similar system for the swarm's mothership quad. MTB Discs are too finicky, hydraulic auto drums are too heavy. Bands/drums are dirt cheap and work well.


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## Bocephus Jones II (Oct 7, 2004)

thinkcooper said:


> The fully laden vehicle will be operated in an open desert playa, getting up to a max of 5-8 MPH. But it will be needing to navigate in and out of more densely populated camp areas, and it will likely be hauled to events such as next year's Maker's Fair and a few other public urban festivals.
> 
> The brakes on the quad above are band/drum brakes. A very simple, centuries old design lifted from horse drawn carriages. We'll probably integrate a similar system for the swarm's mothership quad. MTB Discs are too finicky, hydraulic auto drums are too heavy. Bands/drums are dirt cheap and work well.


agree...you aren't gonna be taking it down mountain passes. Just Flintstoning it would probably work even.


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## ChuckUni (Jan 2, 2003)

thinkcooper said:


> Thanks for that link - I'd found similar general data as well from a few Asian manufacturers- I'm hoping to find some more specific information, in the best case, a chart comparing branded 3/32, 1/8, etc. in various materials (steel, stainless, ti). We need to be able to get the sturdiest chain made on this new heavy weight quad.


You might have seen this: http://home.earthlink.net/~kmcchain/english/index.html It lists the tensile strength for all the chains if you go through them.

A while ago, I looked through the web and found that 1/8th doesnt always mean stronger in tensile than 3/32nd....etc. One example was that some of those kmc derailer chains has a higher tensile listed than my 1/8th HKK track chain.

Chains should be stronger if the chainline is straight...so if you don't have to shift that "final drive" chain I wouldn't. Also use the largest size cogs you can for it as it will reduce the stress on the chain....less leverage to the chain.

Either way I would think bike chain would work for cruising around flat desert.


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## PdxMark (Feb 3, 2004)

*Where's all the weight?*

Are the tubes filled with concrete? How does that cart get up to 1500 lbs?


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## thinkcooper (Jan 5, 2005)

PdxMark said:


> Are the tubes filled with concrete? How does that cart get up to 1500 lbs?


Within the PDF linked above, there's a drawing of the final Mothership. The best way I can describe it? Cinderella's pumpkin turned coach. There's an enclosed area that will house and transport the robots, with a raised seating area for an operator to view the swarm of robots in field. That raised area will be at least six feet off the ground and will support a computer, with the operator, design-wise looking stylishly like the rest of the project. Aesthetics matter in this case.

The enclosed area will need to house and transport 6 to 8 2' diameter steel sphere robots, each with their own power supply, processor and drive system (also detailed in the PDF above). Overall weight with two peddlers and the gear could approach 2000 pounds or more.

In the past, the quad shown above has hauled at least 600 pounds of gear, in addition to two riders, and it's base weight of ~150 pounds. That's nearly 1100 pounds, hence my use of the big meaty 24"x3" rubber on the rear wheels, with heavy duty, puncture resistant tubes for extra strength.

This project's weight will quite quickly start adding up. Another advantage to keeping the drivetrain bicycle component based.


ChuckUni - thanks for that link - great reference.


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## Sledgehammer03 (Mar 7, 2006)

The stress on the chain(s) will be no more than can be exerted by the person pushing the pedal. The 1000 kg or 2200 lb you have been quoted are working load limits, tensile strength would be the same for a given material, no matter the size, expressed in pounds per square inch, heavier chain, more square inches, higher load limit. since each person will have a free wheel (in aprallel) attached to the drive axle, you will be fine with just regular bicycle chains. If you had a drive system similar to a tandem (in series), you could have an issue with the final drive chain.

Cool looking Machine


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## Oatbran (Apr 27, 2005)

I'm surprised no other engineer-types have answered your post yet, Coop.

Top speed will not be an issue, how quickly you get there is. Your acceleration is the main determining factor on how much tension your chain sees. I've done some calculations, and I don't think chain tensile strength will be an issue unless you get some big guys starting to see how fast they can go on it. But, as with anything, the answer to your question depends on a lot of assumptions. 
I have a spreadsheet I'd be happy to share if you want to pm me.

You may have to worry about bearing strength, though, depending on how your cart is set up.


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## thinkcooper (Jan 5, 2005)

Oatbran,

I'd love a copy of your spreadsheet. My inbox is hopelessly full, but there's a link to send me email in my profile. I prefer that methos anyway. I'd appreciate your input.

RE: wheel and shaft bearings... I'll be using a standard sealed industrial bearing .75" I.D., 1.375" O.D. I'd speculate that the vehicle will amass a maximum of 200 miles over it's lifetime.


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## Dave_Stohler (Jan 22, 2004)

Um......have you considered using a *motorcycle* chain?


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## rogger (Aug 19, 2005)

Dave_Stohler said:


> Um......have you considered using a *motorcycle* chain?


Have you considered the fact that this rig is *geared*?


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## eddie m (Jul 6, 2002)

nonsleepingjon said:


> I'm not any sort of mechanical engineer, but I think you have the concept right: the chain needs to hold up to the power of the engine (humans in this case) and not the vehicle weight. Looks like there's general agreement on this from the other posts. Since you're gearing it low, I would think a bike chain would hold up fine. Now, if it was geared high and both people were standing on the pedals at the same time then it would be a different story.


I am an engineer, so I can tell you that your answer here is only half correct. The chain only needs to carry the power of the engine, but the torque of that engine is multiplied by the gear ratio. With real low gears, the stress on the chain is increased proportionally. 
You can minimize the stress on the chain by using larger cogs. I would avoid anything smaller than a 14, or maybe even 15. You should avoid ultra narrow chains, like 9s or 10s chains, because of the difficulty of joining them reliably. Use 5 or 6s cogs that are wider than current cogs, and lay it all out so that the chains never need to operate at an extreme angle.
Form the pictures, it looks like that thing more or less meets all those requirenents. 

em


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