A cheaper high pivot idler pulley

_Lan
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_Lan
Edited Date/Time 4/3/2022 1:50am


The idler on my bike needs replacing and they are pricey for what they are. I tried finding a cheaper solution and came across fixie sprockets. It seems possible to design a carrier for it. This is my interpretation that requires a bb tool and a chain wrench to install. Will still need to produce one to try but I feel it's feasible. Only maybe 30-60 grams heavier than an aluminum pulley. You also get a choice of 12T to 22T or whatever number of teeth can fit on your frame to change your anti-squat numbers.

Cheaper, lasts way longer, and more variable to boot. I don't see any drawbacks besides the weight. Is there anything I'm not seeing?
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anotherbikerguy 11/4/2021 10:53pm
11/4/2021 10:53pm
From the rendering it looks like it would be significantly wider than a standard pulley. Could there be frame compatibility issues (or potentially chainguide compatibility issues) because of the increased width?

Cool idea, though. I think you should prototype and try it if you can!
_Lan
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_Lan 11/5/2021 3:08am
11/5/2021 3:08am
anotherbikerguy wrote:
From the rendering it looks like it would be significantly wider than a standard pulley. Could there be frame compatibility issues (or potentially chainguide compatibility issues)...
From the rendering it looks like it would be significantly wider than a standard pulley. Could there be frame compatibility issues (or potentially chainguide compatibility issues) because of the increased width?

Cool idea, though. I think you should prototype and try it if you can!
Yeah, need to make sure it clears the crank arm and frame. Will be 3d printing one for testing as soon as the sprockets I ordered arrive. It should be an easy fix though, just make the lock ring thinner etc.

it's for my own bike design so I'm able to make changes to make it fit. Just thought I'd throw the idea out there so other people can try it out on their own. I based this on the forbidden 16T pulley that I'm using that is nearing the end of its life.
Diag
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Diag 11/5/2021 3:32am
11/5/2021 3:32am
Since there's no torque transferred trough the idler you could get rid of the jam nut to reduce the width, the sprocket just needs to be tight on the axle so it doesn't back of with vibration... Cool project, keep it up!
jeff.brines
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jeff.brines 11/5/2021 6:56am
11/5/2021 6:56am
Diag wrote:
Since there's no torque transferred trough the idler you could get rid of the jam nut to reduce the width, the sprocket just needs to be...
Since there's no torque transferred trough the idler you could get rid of the jam nut to reduce the width, the sprocket just needs to be tight on the axle so it doesn't back of with vibration... Cool project, keep it up!
I'm kind of an idiot but what do you mean there is no torque transferred through the idler? This seems wrong.
jonkranked
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jonkranked 11/5/2021 8:10am
11/5/2021 8:10am Edited Date/Time 11/5/2021 8:19am
unless things have changed in recent years, cogs for track bikes are designed for single speed chains, and are too large to work with chains for geared drivetrains. geared chains (9/10/11/12spd) are too narrow and likely will not properly mesh with the teeth on a track cog.

edit: it seems like 3/32 track cogs are widely available, and might work with certain geared chains. a 1/8" track cog will not work.

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jonkranked 11/5/2021 8:11am
11/5/2021 8:11am Edited Date/Time 11/5/2021 8:21am
i have a track cog at home (although it might be a 1/8" size) and some 9 & 11spd chains, I can check when i get home from work if you'd like.
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millsr4 11/5/2021 11:59am
11/5/2021 11:59am Edited Date/Time 11/5/2021 12:00pm
Diag wrote:
Since there's no torque transferred trough the idler you could get rid of the jam nut to reduce the width, the sprocket just needs to be...
Since there's no torque transferred trough the idler you could get rid of the jam nut to reduce the width, the sprocket just needs to be tight on the axle so it doesn't back of with vibration... Cool project, keep it up!
jeff.brines wrote:
I'm kind of an idiot but what do you mean there is no torque transferred through the idler? This seems wrong.
I think Diag means that no torque goes through the idler in the opposite direction of the ID threads so just the carrier without the nut would suffice. Just like how there is no nut on a single speed hub with a freewheel.
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Diag
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Diag 11/5/2021 2:00pm
11/5/2021 2:00pm
jeff.brines wrote:
I'm kind of an idiot but what do you mean there is no torque transferred through the idler? This seems wrong.
I know it is somewhat counter intuitive i'll try to explain : the idler is freely spinning on a shaft, it cant transmit twisting force to the frame, and the torque created by the part of the chain going the crankset is cancel by the torque created by the part of the chain going the the wheel (same magnitude, opposing direction)
Idlers are called idlers because they dont create or consume power, they just redirect force.

Maybe I should me more precise too, there is no torque transferred around the axis of the bearing when the speed is constant (granted the acceleration in this case are probably small and can be ignored)
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jeff.brines
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jeff.brines 11/5/2021 2:16pm
11/5/2021 2:16pm
Diag wrote:
I know it is somewhat counter intuitive i'll try to explain : the idler is freely spinning on a shaft, it cant transmit twisting force to...
I know it is somewhat counter intuitive i'll try to explain : the idler is freely spinning on a shaft, it cant transmit twisting force to the frame, and the torque created by the part of the chain going the crankset is cancel by the torque created by the part of the chain going the the wheel (same magnitude, opposing direction)
Idlers are called idlers because they dont create or consume power, they just redirect force.

Maybe I should me more precise too, there is no torque transferred around the axis of the bearing when the speed is constant (granted the acceleration in this case are probably small and can be ignored)
Ah ha! This makes sense. Thx!
_Lan
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_Lan 11/6/2021 12:17am
11/6/2021 12:17am
Diag wrote:
Since there's no torque transferred trough the idler you could get rid of the jam nut to reduce the width, the sprocket just needs to be...
Since there's no torque transferred trough the idler you could get rid of the jam nut to reduce the width, the sprocket just needs to be tight on the axle so it doesn't back of with vibration... Cool project, keep it up!
I thought about that. Should save a bit of weight as well hah.
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Primoz 11/9/2021 9:46am
11/9/2021 9:46am
Why the double BB interfaces? Just make the sprocket carrier a flanged single piece part and deal with disassembly from the NDS ('internal') side if crank clearance is a problem. Just rotate the sprocket assembly with the bearing around the vertical axis on the bolt and you're done. And make the outer flange thinner if needed.

As for sprockets, you have HG splined single speed sprockets as well. A few strategically placed keys should do the trick without needing any threads. And the whole assembly will be thinner still Wink
If you need HG freehub/sprocket dimension, PVD posted some drawings here: https://www.mtbr.com/threads/question-on-shimano-9-speed-rear-casette-s…
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slimjim22206 1/18/2022 7:31am
1/18/2022 7:31am
_Lan wrote:
[img]https://p.vitalmtb.com/photos/forums/2021/11/04/11595/s1200_idler.jpg[/img] The idler on my bike needs replacing and they are pricey for what they are. I tried finding a cheaper solution and came across fixie...


The idler on my bike needs replacing and they are pricey for what they are. I tried finding a cheaper solution and came across fixie sprockets. It seems possible to design a carrier for it. This is my interpretation that requires a bb tool and a chain wrench to install. Will still need to produce one to try but I feel it's feasible. Only maybe 30-60 grams heavier than an aluminum pulley. You also get a choice of 12T to 22T or whatever number of teeth can fit on your frame to change your anti-squat numbers.

Cheaper, lasts way longer, and more variable to boot. I don't see any drawbacks besides the weight. Is there anything I'm not seeing?
Hey! I was just wondering what CAD program you used? You nailed the CAD not gonna lie
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Primoz 1/18/2022 7:50am
1/18/2022 7:50am
Looks like Solidworks.
I did just now notice the shape of the teeth. It's... interesting. Is it just a placeholder as a standard sprocket will be used?

If anyone will be drawing some sprockets, here's a guide: http://www.gizmology.net/sprockets.htm
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slimjim22206
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slimjim22206 1/18/2022 7:54am
1/18/2022 7:54am
Primoz wrote:
Looks like Solidworks. I did just now notice the shape of the teeth. It's... interesting. Is it just a placeholder as a standard sprocket will be...
Looks like Solidworks.
I did just now notice the shape of the teeth. It's... interesting. Is it just a placeholder as a standard sprocket will be used?

If anyone will be drawing some sprockets, here's a guide: http://www.gizmology.net/sprockets.htm
It does look like solid works. And thanks for the link. Always wondered how to do that.
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Big Bird 1/18/2022 8:19am
1/18/2022 8:19am
As long as we're nit picking, I just noticed that the lock ring has no threads. Not that I have any clue how to use Solid Works.
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JankyEric 3/6/2022 11:57am
3/6/2022 11:57am
_Lan wrote:
[img]https://p.vitalmtb.com/photos/forums/2021/11/04/11595/s1200_idler.jpg[/img] The idler on my bike needs replacing and they are pricey for what they are. I tried finding a cheaper solution and came across fixie...


The idler on my bike needs replacing and they are pricey for what they are. I tried finding a cheaper solution and came across fixie sprockets. It seems possible to design a carrier for it. This is my interpretation that requires a bb tool and a chain wrench to install. Will still need to produce one to try but I feel it's feasible. Only maybe 30-60 grams heavier than an aluminum pulley. You also get a choice of 12T to 22T or whatever number of teeth can fit on your frame to change your anti-squat numbers.

Cheaper, lasts way longer, and more variable to boot. I don't see any drawbacks besides the weight. Is there anything I'm not seeing?
Solid design! I made and sold a bunch of these idler pulleys for Forbidden bikes using a SRAM 16t chainring. I've just sold out of them and was thinking about a similar design for my next batch.

https://jankcomponents.com/products/steel-idler-pulley-kit-forbidden-dr…
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_Lan
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_Lan 4/1/2022 8:47am
4/1/2022 8:47am
Finally had one made. Using a 3/32 surley 15T sprocket. Works as intended.
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Primoz 4/1/2022 9:21am
4/1/2022 9:21am
Is that an updated Mk1 frame or an Mk3? Tongue
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idkmtb 4/1/2022 10:25am
4/1/2022 10:25am
_Lan wrote:
Finally had one made. Using a 3/32 surley 15T sprocket. Works as intended. [img]https://p.vitalmtb.com/photos/forums/2022/04/01/12331/s1200_IMG_20220401_122505.jpg[/img]
Finally had one made. Using a 3/32 surley 15T sprocket. Works as intended.
wanted to make sure you were aware, looks like your link pivot is cracked





Primoz
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Primoz 4/1/2022 12:29pm
4/1/2022 12:29pm
Talk about being an eagle eye...
_Lan
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_Lan 4/2/2022 11:42pm
4/2/2022 11:42pm
Primoz wrote:
Talk about being an eagle eye...
Lol, made me check the bike. Fortunately that's just a strand of teflon tape.
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_Lan
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_Lan 4/3/2022 12:03am
4/3/2022 12:03am
Also, sprocket loosens over time. Guess I'll need to put loctite on it
Primoz
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Primoz 4/3/2022 12:41am
4/3/2022 12:41am
Or make everything aluminium so it seizes up like the bolts on a DUB crank :D
hitar_potar 4/3/2022 12:47am
4/3/2022 12:47am
Primoz wrote:
Is that an updated Mk1 frame or an Mk3? Tongue
Apparently a third frame, a MK3. The op didn’t reply, but he just posted a bike check of a MK3. Smile
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_Lan
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_Lan 4/3/2022 1:39am
4/3/2022 1:39am
Primoz wrote:
Is that an updated Mk1 frame or an Mk3? Tongue
mk3 is the updated mk1 haha.

Still some problems despite changing suppliers. Really have to be there in person to guide the work to get what you want. Language barrier is a problem too. Bike is very usable though despite the flaws. Hopefully it's strong enough and I'll be able to enjoy it for a long time.
_Lan
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_Lan 4/3/2022 1:40am
4/3/2022 1:40am
Primoz wrote:
Or make everything aluminium so it seizes up like the bolts on a DUB crank :D
built in thread locker Grinning
_Lan
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_Lan 4/3/2022 1:50am
4/3/2022 1:50am
Primoz wrote:
Is that an updated Mk1 frame or an Mk3? Tongue
hitar_potar wrote:
Apparently a third frame, a MK3. The op didn’t reply, but he just posted a bike check of a MK3. Smile
Just had the first ride today. Checking for bolts unthreading and signs of failure while hitting bigger and bigger huck to flats. Not to the point of bottoming out mind, still don't fully trust the bike. Really love how the bike feels so far.
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illoaminati 12/10/2022 6:47pm
12/10/2022 6:47pm
_Lan wrote:
Finally had one made. Using a 3/32 surley 15T sprocket. Works as intended. [img]https://p.vitalmtb.com/photos/forums/2022/04/01/12331/s1200_IMG_20220401_122505.jpg[/img]
Finally had one made. Using a 3/32 surley 15T sprocket. Works as intended.

Is there any way to get a hold of one of these carriers?

I’m fed up with the labyrinth seal on my Druid. The NSB SS idlers have been sold out forever, and the Jank carriers are nowhere to be seen(good luck on PB Academy Eric!)

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