Hydraulic brakes with one functioning hand

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[XAP]Bob
Posts: 16752
Joined: 26 Sep 2008, 4:12pm

Re: Hydraulic brakes with one functioning hand

Postby [XAP]Bob » 28 Jan 2019, 1:29pm

pjclinch wrote:Magura BIG Twin, see here...

As for "must be two independent systems", well, Up To A Point, Lord Copper... Dame Sarah Storey rides around on a bike with one lever controlling both brakes, this is public knowledge and yet nobody has seen fit to have her arrested and fined.

If you mow someone down on a bike without decent brakes the Book Will Be Thrown At You if it's clearly your fault, but a bit like SPuD pedals without reflectors being illegal, or the pedal reflectors on a 'bent not being visible from the rear being illegal, I'd be very surprised if you got nicked just for having a bike with Maggie BIG Twins on the road.

Pete.



My pedal reflectors are visible from the rear - you just have to be quite close and high, and my feet can't be on the pedals...
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.
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Harry Sp
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Joined: 25 Jan 2019, 9:35am

Re: Hydraulic brakes with one functioning hand

Postby Harry Sp » 29 Jan 2019, 1:03pm

Ugly wrote:I used to ride with a chap, Peter who had a badly deformed hand he had a foot lever to operate the rear brake. This was custom made by a competent engineer and attached to the frame by a brazed on boss, it comprised a lever mounted to the left chain stay that the riders foot cleared in his normal pedalling action but by putting his foot in a horizontal position it enabled his heel to engaged with the lever and pull on the back brake. Peter is no longer with us but one of his bikes is owned by a friend of mine, the foot brake equipment is now removed but is kept by my friend if anyone is seriosly interested I will see if I can get some photos.


That sounds cool but I wouldn't want it on my road bike as cycle clipped in and don't want to change that. And I've gone dutch with my everyday bike so have a back pedal brake anywho.

9494arnold
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Joined: 21 Jan 2007, 3:13pm

Re: Hydraulic brakes with one functioning hand

Postby 9494arnold » 29 Jan 2019, 1:42pm

What thirdcrank said earlier .
Probably already been gone over here:
You need 2 independent braking systems .
That dual caliper set up is only one system irrespective of fact it has 2 calipers, it only has one lever if the lever fails the whole setup fails.
Having said that I am sure that if it's working properly it would stop you in an instant on a solo
(I've ridden a recumbent trike with Cable Drums on the front and that was a damn good stopper, I assume Hydraulics would be even better)
Like I already said there's actually lots of places you can put an additional brake lever, on the bars or at the end of the bars being favorite as you don't have to let the bars go . :shock:
I've ridden a Vintage Goods Trike with a handbrake under the front of the saddle . :wink:
A lot of the safety regs talk about "Complete Cycles", I am fairly confident in saying that this is why Bikes are usually sold without the pedals, hence they aren't complete so a bit of a dodge around the regs there. :shock:

Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: Hydraulic brakes with one functioning hand

Postby Brucey » 29 Jan 2019, 2:12pm

one issue with 'linked brakes' is that (depending on the weight distribution) you need the front brake to come on harder than the rear brake, otherwise the rear wheel just locks up in any kind of hard stop. With a hydraulic disc system an obvious way of managing this is to fit different sized discs front and rear but this alone may not provide enough of a difference; you might need to fit different calipers (with different sized pistons in them) front and rear as well.

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

iandusud
Posts: 180
Joined: 26 Mar 2018, 1:35pm

Re: Hydraulic brakes with one functioning hand

Postby iandusud » 30 Jan 2019, 10:33am

Brucey wrote:one issue with 'linked brakes' is that (depending on the weight distribution) you need the front brake to come on harder than the rear brake, otherwise the rear wheel just locks up in any kind of hard stop. With a hydraulic disc system an obvious way of managing this is to fit different sized discs front and rear but this alone may not provide enough of a difference; you might need to fit different calipers (with different sized pistons in them) front and rear as well.

cheers


The ideal would be to have an adjustable distribution valve but I've no idea if any such thing exists that could be adapted for bicycle brakes.

Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: Hydraulic brakes with one functioning hand

Postby Brucey » 30 Jan 2019, 12:51pm

adjustable bias valves exist for racing cars but the ones on road cars are mostly very simple (non adjustable) and have a crude action; there is front-rear bias built into the brakes because of disc/piston sizes and the 'proportioning valve' simply subtracts a fixed increment from the line pressure to the rear brakes; the adjustable ones simply allow you to vary the size of the fixed increment. The effect of this is that the rear brakes don't even come on most of the time..... they come on pretty hard under heavy braking though and I think they rely on the ABS o a road car to sort everything out.

Some of these valves are small enough to fit onto a bike or trike, but the fittings would need adapting to take bicycle brake hose and they are designed to work with DOT4 type fluid; this would restrict your choice of brake systems somewhat.

Better (for racing) brakes use a twin MC/balance bar type setup; this keeps the rear line pressure in true proportion to the front; however I have never seen this setup used on anything smaller than a car, and if you are looking to adapt a 'road hydro STI' I can't see how this would ever work. I suspect that you could perhaps adapt a cable STI working a hope V-twin MC with a balance bar fitted perhaps....?

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

offroader
Posts: 10
Joined: 18 Dec 2018, 4:47pm

Re: Hydraulic brakes with one functioning hand

Postby offroader » 30 Jan 2019, 4:11pm

Apologies for the personal/invasive questions
a) Do you have use of your left arm?
b) Do you mechanically attach your left hand to the bar?

I'm wondering if you could for example use you left arm to
a) Push a flat bar lever on the reverse side of the handlebar
b) Operate a twist grip type brake

Failing that I'd be considering
use DI2 sprint shifters for gears
Use a modified mechanical STI to do two brakes - one brake as normal and one on the side to side shift mechanism (with the ratchet mechanism removed) to operate a cable brake or a cable->hydraulic convertor. Possibly with electric servo assistance
But I'm an engineer so over complicated technical solutions appeal, especially when other people have to use them :lol:

Or maybe
Two flat bar hydraulics mounted on conventionally but one above the other on the right bar top. Quite possibly with custom lever blades to bring them close together (I remember seeing a system somewhere where a guy has built a brake with twin levers but of course I forget where!). One hand could then operate two brakes. The drop bar STI could be teed into either front or rear system to give you day to day single wheel braking from the drops

Also I'd recommend trying to get in touch with Martyn Ashton (Facebook page according to google or google for GMBN contact info) as I imagine he knows people who have solved this kind of thing before

PS
While googling for the twin lever brake above I came across this
https://www.velonews.com/2017/12/bikes- ... and_453215

Muito Obrigado

AndyA
Posts: 348
Joined: 21 Mar 2009, 9:16pm
Location: Edinburgh

Re: Hydraulic brakes with one functioning hand

Postby AndyA » 5 Feb 2019, 12:22am

https://www.outbraker.eu/product/outbra ... -2-brakes/
Potentially useful but I'm not sure if this product is right - it seems to just be a y-splitter with some dubious psuedo abs. What I think you'd want is a larger hydraulic cylinder actuated by your existing system possibly with a proportioning valve to set front/rear bias


thirdcrank
Posts: 27820
Joined: 9 Jan 2007, 2:44pm

Re: Hydraulic brakes with one functioning hand

Postby thirdcrank » 5 Feb 2019, 3:23pm

What thirdcrank said earlier . ...


Although I wish now I hadn't bothered.

zenitb
Posts: 119
Joined: 7 Aug 2018, 9:59pm
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Re: Hydraulic brakes with one functioning hand

Postby zenitb » 5 Feb 2019, 4:14pm

Historic solution..

http://www.oldbike.eu/museum/1905-2/190 ... oot-brake/

..although would you want to take a foot off the pedal in an emergency??
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