Why no V brakes with roller instead of noodle?

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SA_SA_SA
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Why no V brakes with roller instead of noodle?

Postby SA_SA_SA » 26 Sep 2014, 12:09pm

Why no V brakes with roller instead of noodle?

A travel agent used as a plain roller is better than a noodle so how come no brakes with a roller built in?
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[XAP]Bob
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Re: Why no V brakes with roller instead of noodle?

Postby [XAP]Bob » 26 Sep 2014, 1:49pm

Cheaper to make?
good enough?
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
There are two kinds of people in this world: those can extrapolate from incomplete data.

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andrew_s
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Re: Why no V brakes with roller instead of noodle?

Postby andrew_s » 26 Sep 2014, 1:57pm

My understanding is that a cable will eventually fatigue and break if used with a pulley less than about 20x* the size of the cable, and a travel agent is smaller than 20mm for a 1mm brake cable. A noodle has a much larger curve radius.
* (varies according to the stranding of the cable)

http://blog.loosco.com/bid/87060/Cable- ... -D-d-Ratio
http://books.google.co.uk/books?id=Pk9m ... ey&f=false

If you use a travel agent, it's not the brake manufacturer's problem if you crash because the cable breaks, whilst it is if the brake comes with one.

[edit]
There's a topic here where a mate of Brucey's was getting through an STI cable in 9 months because of flexing over the shifter drum. STI cables are thinner and the drum larger than brake & travel agent, so you'd expect the fatigue life to be longer than for a brake. A good thing people with travel agents for Vs and drop bar levers don't brake as frequently as some people change gear.
Last edited by andrew_s on 27 Sep 2014, 2:06am, edited 3 times in total.

LWaB
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Re: Why no V brakes with roller instead of noodle?

Postby LWaB » 26 Sep 2014, 2:01pm

The rule of thumb is that the roller should be 20 x the cable diameter to prevent cable failure. A noodle easily exceeds that minimum curvature, the aftermarket rollers don't.

SA_SA_SA
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Re: Why no V brakes with roller instead of noodle?

Postby SA_SA_SA » 26 Sep 2014, 2:45pm

A bigger built in roller?

The travel agent roller definitely feels more direct than a noodle.
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Redvee
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Re: Why no V brakes with roller instead of noodle?

Postby Redvee » 27 Sep 2014, 12:32am

I used cog hogs on my v-brakes in the past.

Image

I can remember having to trim the nose down to fit into the cable stop on the v-brakes.

SA_SA_SA
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Re: Why no V brakes with roller instead of noodle?

Postby SA_SA_SA » 27 Sep 2014, 11:39am

andrew_s wrote:My understanding is that a cable will eventually fatigue and break if used with a pulley less than about 20x* the size of the cable, and a travel agent is smaller than 20mm for a 1mm brake cable........


I should clarify that I was/will be using the agents in 1-1 mode: i.e. only the larger outer roller is used. It looked abouit 20mm diameter to me?
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Brucey
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Re: Why no V brakes with roller instead of noodle?

Postby Brucey » 28 Sep 2014, 6:32pm

as others have pointed out fatigue is an issue. So is cost.

At one time I had an MTB with cantis. It had no front hanger per se, just a roller hidden the stem (just as well; there was no room for a normal hanger; bike came from the factory with a steerer that was too short for all but the least stack height headset and even then you had to leave the washer out... :roll: ) . I thought this 'roller in the stem' arrangement was the dog's danglers until I noticed that the brake cable had a very short life and would fatigue inside without me being able to see it happening.

The roller in my stem was a little smaller than some you see but there is no doubt that rollers fatigue cables; they will fatigue thicker brake cables worse than thinner gear cables, too. I think it is pretty clear that to have the same bend radius in the cable as in a noodle, a pulley or roller would have to be well over 2" in diameter.

So I'll be sticking with noodles for now, ta....

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

SA_SA_SA
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Re: Why no V brakes with roller instead of noodle?

Postby SA_SA_SA » 28 Sep 2014, 10:12pm

Brucey wrote:.... a pulley or roller would have to be well over 2" in diameter.
.....cheers

Oh well, I suppose a bit uglys: alternatively, what about my idea for a direct-curve like noodleless brake but minus the unequal pad wear......
http://forum.ctc.org.uk/viewtopic.php?f=5&t=90745
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