Why does Freewheel disassemble into parts?

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azad   10 mW

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Why does Freewheel disassemble into parts?

Post by azad » Feb 21 2020 10:03am

Hi,

I have a single speed freewheel sprocket in the mid-drive setup (i.e. with a freewheel crank). The freewheel has an adapter attached to it for motor mount. Freewheel gets disassembled on the way while driving resulting in all the ball bearings scattered on the road. In the picture you see the disassembled version of such a freewheel. It probably is a malicious attempt that somebody does whenever I park it outside the shopping mall. I am not sure why this is so easy to dismantle while being mounted on the motor. Note that while mounted, the lid of the freewheel is facing the motor and is very difficult to reach with tools quickly in public.

Could it be that when somebody stops the wheel forcefully and provide the acceleration at the same time, causes the internals of the freewheel rotate while outer remains stationary resulting in lid to burst open?

If it is that easy to break, how can I solve this problem? (I am stuck with the adapter because it fits the motor shaft - 11mm) However I am open to new solutions.
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Last edited by azad on Feb 22 2020 10:10pm, edited 2 times in total.

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Dauntless   100 GW

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Re: Why does Freewheel disassemble into parts?

Post by Dauntless » Feb 21 2020 2:47pm

If I understand what you're saying, I suspect you need to reverse the thread direction. Literally, a nut or bolt can.come loose crom the direct shaft spins. And example i have to deal with is a universal arm on a c stand, which i might hand smething heavy on. If it pulls down in the direction thatlossens the t handle, then itcan come loose and fall so we want it pulling in the diection it tightens. Same for your motor shaft, it would seem to turn in the direction that loosens the nut.

Just an assumption from what little you described.
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azad   10 mW

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Re: Why does Freewheel disassemble into parts?

Post by azad » Feb 21 2020 9:43pm

It is a standard single speed bicycle freewheel.

It is not the thread direction issue. Somebody intentionally breaks it when I leave it unattended. I have replaced 3 until now and the same thing happened with each of them. the lid has counter clockwise opening and freewheel rotates clockwise all the time. Also, the lid and the spokes on the wheel rotate together so it is not designed to open up while in the driving situation.

I'm not sure why it is so easy to break and how to improve this so that it isn't as easy to do.

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E-HP   100 kW

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Re: Why does Freewheel disassemble into parts?

Post by E-HP » Feb 22 2020 12:39pm

azad wrote:It is a standard single speed bicycle freewheel.

It is not the thread direction issue. Somebody intentionally breaks it when I leave it unattended. I have replaced 3 until now and the same thing happened with each of them. the lid has counter clockwise opening and freewheel rotates clockwise all the time. Also, the lid and the spokes on the wheel rotate together so it is not designed to open up while in the driving situation.

I'm not sure why it is so easy to break and how to improve this so that it isn't as easy to do.
Post a picture of it on the bike. Maybe just adding a shroud so that it can’t be seen would help.


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HK12K   10 kW

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Re: Why does Freewheel disassemble into parts?

Post by HK12K » Feb 22 2020 1:51pm

Seems an obscure thing to be repeatedly sabotaged.

goatman   10 kW

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Re: Why does Freewheel disassemble into parts?

Post by goatman » Feb 22 2020 4:45pm

id try some Loctite, maybe even high temp Loctite if your freewheel gets hot

azad   10 mW

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Re: Why does Freewheel disassemble into parts?

Post by azad » Feb 22 2020 10:10pm

E-HP wrote:
Feb 22 2020 12:39pm
azad wrote:It is a standard single speed bicycle freewheel.

It is not the thread direction issue. Somebody intentionally breaks it when I leave it unattended. I have replaced 3 until now and the same thing happened with each of them. the lid has counter clockwise opening and freewheel rotates clockwise all the time. Also, the lid and the spokes on the wheel rotate together so it is not designed to open up while in the driving situation.

I'm not sure why it is so easy to break and how to improve this so that it isn't as easy to do.
Post a picture of it on the bike. Maybe just adding a shroud so that it can’t be seen would help.


Sent from my iPhone using Tapatalk
Added more picture.

HK12K   10 kW

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Re: Why does Freewheel disassemble into parts?

Post by HK12K » Feb 23 2020 1:28am

I can't tell from the pictures, but is is possible that the freewheel is experiencing some lateral forces due to improper chainline, acceleration induced flex, etc, that put force on it in a way it wouldn't normally experience? Perhaps exasperated by chain tension?

Just spitballing.

HK12K   10 kW

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Re: Why does Freewheel disassemble into parts?

Post by HK12K » Feb 23 2020 1:30am

I can't tell from the pictures, but is is possible that the freewheel is experiencing some lateral forces due to improper chainline, acceleration induced flex, etc, that put force on it in a way it wouldn't normally experience? Perhaps exasperated by chain tension?

Just spitballing.

I had a go cart that used to grenade centrifugal clutches like it was it's job if I cornered hard enough to flex the chassis, which I did often.

goatman   10 kW

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Re: Why does Freewheel disassemble into parts?

Post by goatman » Feb 23 2020 2:09am

its notched for a shaft key way, are you using a key? is your shaft notched for a key? like a woodruff key?

https://duckduckgo.com/?q=shaft+key+way ... yTypes.gif

Balmorhea   1 kW

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Re: Why does Freewheel disassemble into parts?

Post by Balmorhea » Feb 23 2020 2:39am

Freewheels are designed to overrun (rotate the outside relative to the inside) only when not under load-- when there's not significant tension on the chain. On a normal bike, that's the way it works. You pedal, the freewheel locks up, and the chain applies tension. When you stop pedaling, the freewheel overruns, but there's no tension on the chain. The bearings can be rather loose and crude, because they are not under load when they turn.

When used as a front freewheel on an e-bike, there is a lot of tension on the chain when you use these motor without pedaling along. This wrecks ordinary freewheels; there's no avoiding it. One common remedy is to apply a small tack weld at the edge where the bearing cone threads onto the inner freewheel body, to prevent it loosening and coming apart. However, this doesn't prevent rapid degradation of the overloaded bearing, which manifests itself as lateral free play and wobble in the chainring.

It's not self-evident from your picture, but if your system transmits motor power through a freewheel while it overruns, then the problem is the same as if it were in the chainring. If it doesn't do that, then your problem is related to having too much tension on the chain the way it's adjusted. There should always be a small amount of slack when it isn't running.

Heavy duty freewheels like White Industries and others intended for trials use might last longer in these abusive conditions. But they aren't supposed to spin when there's tension on the chain, either. They'll deteriorate and fail earlier than expected when used that way, even if they do last longer then cheap freewheels.

azad   10 mW

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Re: Why does Freewheel disassemble into parts?

Post by azad » Feb 23 2020 6:49am

HK12K wrote:
Feb 23 2020 1:30am
I can't tell from the pictures, but is is possible that the freewheel is experiencing some lateral forces due to improper chainline, acceleration induced flex, etc, that put force on it in a way it wouldn't normally experience? Perhaps exasperated by chain tension?

Just spitballing.

I had a go cart that used to grenade centrifugal clutches like it was it's job if I cornered hard enough to flex the chassis, which I did often.
I am fairly certain that it is an act of malice because I drive it many miles, nothing happens and then suddenly I leave unattended for few minutes outside mall and come back and ride and there it is the cracking sound and it is broken. I've placed it again now just to take pictures, the chain was well aligned.

azad   10 mW

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Re: Why does Freewheel disassemble into parts?

Post by azad » Feb 23 2020 6:50am

goatman wrote:
Feb 23 2020 2:09am
its notched for a shaft key way, are you using a key? is your shaft notched for a key? like a woodruff key?

https://duckduckgo.com/?q=shaft+key+way ... yTypes.gif
Yes there is a key and placement was perfect until it happened. I just hanged it temporarily now. This is just quick way to take a picture to show you guys how it looked like.

azad   10 mW

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Re: Why does Freewheel disassemble into parts?

Post by azad » Feb 23 2020 6:58am

Balmorhea wrote:
Feb 23 2020 2:39am
Freewheels are designed to overrun (rotate the outside relative to the inside) only when not under load-- when there's not significant tension on the chain. On a normal bike, that's the way it works. You pedal, the freewheel locks up, and the chain applies tension. When you stop pedaling, the freewheel overruns, but there's no tension on the chain. The bearings can be rather loose and crude, because they are not under load when they turn.

When used as a front freewheel on an e-bike, there is a lot of tension on the chain when you use these motor without pedaling along. This wrecks ordinary freewheels; there's no avoiding it. One common remedy is to apply a small tack weld at the edge where the bearing cone threads onto the inner freewheel body, to prevent it loosening and coming apart. However, this doesn't prevent rapid degradation of the overloaded bearing, which manifests itself as lateral free play and wobble in the chainring.

It's not self-evident from your picture, but if your system transmits motor power through a freewheel while it overruns, then the problem is the same as if it were in the chainring. If it doesn't do that, then your problem is related to having too much tension on the chain the way it's adjusted. There should always be a small amount of slack when it isn't running.

Heavy duty freewheels like White Industries and others intended for trials use might last longer in these abusive conditions. But they aren't supposed to spin when there's tension on the chain, either. They'll deteriorate and fail earlier than expected when used that way, even if they do last longer then cheap freewheels.
It is true that there is a lot of tension on freewheel due to tight chain but I had no other choice as loose motor chain interferes with the other normal bicycle chain. Already when I switch the gears, both chain start to slide and make crackling noise. I was thinking of using some sealant on the threads but then I worry it might not ruin the freewheel as threads are already quite thin and close to ball bearings. It is important to have a freewheel for mid-drive setup so, that there isn't any motor drag while peddling.

If freewheel is such a disaster for mid-drive setup then what should be used instead of it?

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amberwolf   100 GW

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Re: Why does Freewheel disassemble into parts?

Post by amberwolf » Feb 24 2020 1:31am

some systems use a sprag (roller) clutch, but it may require a redesign of axle and mounting hardware, and sprocket adapter.

azad   10 mW

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Re: Why does Freewheel disassemble into parts?

Post by azad » Feb 26 2020 10:56am

amberwolf wrote:
Feb 24 2020 1:31am
some systems use a sprag (roller) clutch, but it may require a redesign of axle and mounting hardware, and sprocket adapter.
Like the scooter clutch? I was thinking of remodeling on that lines but then it would be very difficult to adjust big scooter sprocket alongside crank-set and motor.

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