Freewheeling motor and coaster brake?

Discussions related to motors other than hub motors.
This includes R/C motors, botttom bracket, roller and geared drives.
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BullyB   1 µW

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Freewheeling motor and coaster brake?

Post by BullyB » Feb 20 2019 8:49pm

Ok so I have a Phantom and it is great but hub motor does have a few drawbacks.
I like the mid drive + internal gear hub setup for the fact that the motor can use the gearing also.
Here's the kicker- I like a good coaster brake hub.
Now I have read that the TSzd2 has an option for this, but I am cheap and a part of me thinks the motor hanging down below the crank is only OK.

So the frame I am looking at has space between the post and rear wheel.
My question is can i use a standard brushless motor bolted up on the frame in line with the chain with a forward freewheel on the motor shaft?
Does that make sense?
I want to do PAS so I figure I would need some sorta sensor for the controller?
Any experienced opinions much appreciated.
Brax

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Chalo   100 GW

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Re: Freewheeling motor and coaster brake?

Post by Chalo » Feb 20 2019 11:22pm

The Prodeco Phantom bike has vertical dropouts, which makes it incompatible with a coaster brake. Since your question is interesting, I'm going to address it with the assumption that you'd be willing to switch to a suitable frame with horizontal dropouts.

It would be tricky to get enough wrap around both the motor sprocket and the crank sprocket. If you check out the 500W Cyclone mid drive, you can see their approach to dealing with the problem. Their way doesn't meet industrial standards for such things, which dictate a minimum 120 degrees of engagement between a drive sprocket or driven sprocket and its chain.

Image

If you can resolve that issue, it doesn't have any other show stoppers in principle.

Note that when the coaster brake is applied, the slack side of the chain becomes the taut side, so all idlers, drive sprockets, and mounting brackets must be able to withstand the tension that results from full pedal torque.
This is to express my gratitude to Justin of Grin Technologies for his extraordinary measures to save this forum for the benefit of all.

Grantmac   1 kW

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Re: Freewheeling motor and coaster brake?

Post by Grantmac » Feb 21 2019 12:06am

Can't activate a coaster with a freewheeling chain wheel.

BullyB   1 µW

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Re: Freewheeling motor and coaster brake?

Post by BullyB » Feb 21 2019 8:44am

Ah so not enough chain wrap.

Yea I have been trying to convert my phantom to a regular bike. Nightmare. I have a 16t ss sproket and it is just a half link too long. Going to try changing the crank sproket to a 40t or something maybe.

But yea I was thinking an extended tail bike with a long rear fork, motor behind the seat post above the kickstand mount. But yea there would only be a slight amount of wrap. Guessing it would slip under torque then huh.

I am back to eyeing the TSZD2.
Anyone with the TongSheng motor- one of the things I want to avoid is that with my Phantom (after 5 years and arseloads of miles)- my batt is done and so after a few miles it goes out and I am on a veritable exercize bike- pushing the pedals is a severe workout, esspecially since I ditched the derailer* for a 13t ss years ago.
Does the TSZD3 experience the same parasitic motor drag without current or does it "freewheel" somehow?

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Chalo   100 GW

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Re: Freewheeling motor and coaster brake?

Post by Chalo » Feb 21 2019 10:12am

BullyB wrote:
Feb 21 2019 8:44am
Yea I have been trying to convert my phantom to a regular bike. Nightmare. I have a 16t ss sproket and it is just a half link too long. Going to try changing the crank sproket to a 40t or something maybe.
Have a look at this tool: http://eehouse.org/fixin/fixmeup.php

It will allow you to figure out what combination of sprocket sizes will work for your bike. Keep in mind that chains elongate by about 1/4" as they wear, even if you replace them before they exceed specifications. So if your setup depends on a just-right-sized chain, your going to have to replace it often, while it's still plenty good.
Does the TSZD3 experience the same parasitic motor drag without current or does it "freewheel" somehow?
The TSDZ2 and other crank drives have one-way clutches so that the pedals don't drag the motor or vice versa. But that means no coaster brake, like Grantmac said.
This is to express my gratitude to Justin of Grin Technologies for his extraordinary measures to save this forum for the benefit of all.

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Rassy   10 MW

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Re: Freewheeling motor and coaster brake?

Post by Rassy » Feb 21 2019 11:48am

I have a 16t ss sproket and it is just a half link too long.
You can get a half link for most chains, that would solve this little problem.
-Rassy-
One Tadpole Trike equipped with a Bafang BBS02
https://endless-sphere.com/forums/viewt ... 28&t=69419
One Delta Trike equipped with a Bafang BBS02
https://endless-sphere.com/forums/viewt ... 0#p1291260

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Chalo   100 GW

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Re: Freewheeling motor and coaster brake?

Post by Chalo » Feb 21 2019 12:10pm

Rassy wrote:
Feb 21 2019 11:48am
I have a 16t ss sproket and it is just a half link too long.
You can get a half link for most chains, that would solve this little problem.
Maybe. Chain length is sensitive to differences much smaller than half a chain link.
This is to express my gratitude to Justin of Grin Technologies for his extraordinary measures to save this forum for the benefit of all.

BullyB   1 µW

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Re: Freewheeling motor and coaster brake?

Post by BullyB » Feb 21 2019 5:36pm

Would you believe i hacked my chain to male a diy "half link", still slips off on corners. (Initially I thought I had invented some spectacular new thing {I'm gonna be RICH!} :lol: , then I read about them on Sheldon Brown :( )

The chainline isnt ideal either. I know Prodeco sells this bike unpowerd but it must necessitate a gearset. I refuse to have one of those goofy tensioners. :evil:

Gonna check out that link rite now Chalo, big ups!
Oh btw, apparently the TongSheng is available in a special order coaster break version.
Did a little more digging through the forum and one user says there is a bit of drag without power but that it "wears in" eventually. Who knows?

Cheers,
Brax

BullyB   1 µW

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Re: Freewheeling motor and coaster brake?

Post by BullyB » Feb 21 2019 6:31pm

:es: holy cows eggs this website is the tits :es:
http://eehouse.org/fixin/fixmeup.php

I just love old HTML websites.
Does anyone remember old webpages with code embedded to make your windows pointer into a wand or excessive flashing text or stars and snow glitering all over the page?!
What happened to that?
Damn CSS and smartphone compatabilty.

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