Weird Hs33 Lever Copys, Called 'kooka'

[cai]

Hey just found these on Ebay, they're called Kooka and are going for £1-70!

They seem to look alright - especialy the lever blades, they look like RB's. Has anyone ever rode/broken/heard of one before?

The link is here.

[AdamR28]

I've got one a black of those somewhere, really nice quality, very light, but 16mm piston.

[cai]

I've got one a black of those somewhere, really nice quality, very light, but 16mm piston.

Is that bad? I no maggies are 14mm.

[Revolver]

cool, they look nice

i'd have them in orange though

[cai]

Does any one know if there still produced, or if anyone still sells them? Because a black one would be lush for me

Edited March 3, 2008 by cai

[AdamR28]

16mm means less leverage and ultimately less braking power...

[cai]

16mm means less leverage and ultimately less braking power...

[Revolver]

16mm means less leverage and ultimately less braking power...

how come?

(i don't know much about hydraulic brakes except, piston goes in, fluid moves, other piston goes out)

Edited March 3, 2008 by Disasterboy

[Muel]

We need a lever with a 12/13mm piston really I'd imagine.

[craigjames]

is there not anyway you could modify them to run the same size pistons as a maggy?

[AdamR28]

Yeh, I imagine a 16 to 14mm sleeve and then a normal HS33 piston would work

[James Quigley]

the 'reach' on them bad boys looks a bit nuts.

I had a kooka headset a couple of years ago which was awesome so these should be of similar quality.

[Revolver]

if the piston size is the diameter of the piston, then that means more fluid goes in the piston

even if its the piston length, more fluid

how come that means less leverage?

[cai]

Yeh, I imagine a 16 to 14mm sleeve and then a normal HS33 piston would work

But would it make a difference with the whole 'less leverage and ultimately less braking power' thing? What I mean is if the inside of the lever-body is meant to fit 16mm, would it not feel exactly the same if bodged with a 14mm?

[AdamR28]

how come that means less leverage?

Push a pen against your finger - larger area, less pressure.

Push a needle against your finger - smaller area, more pressure.

(Bit more to it than that, but that's the basics )

[Revolver]

Push a pen against your finger - larger area, less pressure.

Push a needle against your finger - smaller area, more pressure.

(Bit more to it than that, but that's the basics )

pressure, gotcha

and we want lots of that

[PaRtZ]

It works the same way that gears on a bike do:

Small to big = (low gear) = lots of power but lots of movement to do so

Big to small = (high gear) = little movement, but not alot of power (need lower gear ratios to build up to this)

Thats right isn't it? not messed that up

christ I got a thermofluid exam next week....

But they look really snazzy!

[cai]

Push a pen against your finger - larger area, less pressure.

Push a needle against your finger - smaller area, more pressure.

Just tried it, needle hurts more

[Muel]

I'd rather have an 04 body with an RB lever though, I tried one today, it was brilliant.

Still rather have a disc though.

[ogre]

It works the same way that gears on a bike do:

Small to big = (low gear) = lots of power but lots of movement to do so

Big to small = (high gear) = little more movement, but not alot of power (need lower gear ratios to build up to this)

Thats right isn't it? not messed that up

christ I got a thermofluid exam next week....

But they look really snazzy!

[psycholist]

For hydraulics you assume the fluid is contained at a constant pressure. If the master piston has a 16mm area it will apply 0.76 times the pressure a 14mm piston applies (For a round piston cross sectional area is proportional to the piston diameter squared), making the brake lever feel harder at the bite point at the expense of clamping pressure produced by the slave cylinders. Have a look here for more information on how hydraulics work: http://science.howstuffworks.com/hydraulic1.htm

A longer lever blade or shorter distance between the lever pivot and the pushrod to the lever piston could compensate for the difference in piston diameter between levers.

[Revolver]

For hydraulics you assume the fluid is contained at a constant pressure. If the master piston has a 16mm area it will apply 0.76 times the pressure a 14mm piston applies (For a round piston cross sectional area is proportional to the piston diameter squared), making the brake lever feel harder at the bite point at the expense of clamping pressure produced by the slave cylinders. Have a look here for more information on how hydraulics work: http://science.howstuffworks.com/hydraulic1.htm

A longer lever blade or shorter distance between the lever pivot and the pushrod to the lever piston could compensate for the difference in piston diameter between levers.

they're not for me then

my brakes slip quite often... not surprising since i have standard pads and smooth rims

[cai]

Big to small = (high gear) = little movement, but not alot of power

Big to small = (high gear) = little more movement, but not alot of power

Huh? Who's correct, Partz or Ogre?

[PaRtZ]

i thought me, as big master to small slave = greater quantity of fluid being pushed through? = lower powered brake. Also a bigger slave means that because the same pressure is being exerted throughout the system, a greater pressure is exerted through the slave, as this same pressure is pushed through the whole piston. For example

Right, bastards. You've made me get my lecture notes out now

Pascals principle

If pressure is applied to one part of a closed system it is transmitted without loss in all directions

Pressure = Force / Area

So if you apply a force of 100N (again I don't know how much 100N is like but bare with me) over a 14mm diameter piston:

*************************************************************

14mm Piston

Area = 7mm² (radius) X π (pi) = 153.938mm² = 0.1539metres²

100/0.153m² = 649.612 Pa

*************************************************************

Whereas...

*************************************************************

16mm piston

Area = 8mm² (radius) X π (pi) = 201.062mm² = 0.2010metres²

100/0.201m² = 497.359 Pa

*************************************************************

Therefore a smaller MASTER piston provides a greater pressure. Take note the same isn't the same for slaves because they are being driven by these values given. And combine these results with pascals principle; the slave cylinder(s) will be driven by the same pressure.

**Just to clarify**

Remember that Pressure = Force / Area

and this can be re-arranged to give: Force = Pressure X Area

For the example, I'll use slaves with err 20mm and 22mm diameter with the 14mm master slave being compressed at 100N

So my Pressure (using previous results) is: 649.612 Pascals

*************************************************************

20mm Piston

Area = 10² (radius) X π (pi) = 314.1592mm² = 0.314m²

Force = 649.612 X 0.314 = 204.081 Newtons

*************************************************************

*************************************************************

22mm Piston

Area = 11² (radius) X π (pi) = 380.132mm² = 0.380m²

Force = 649.612 X 0.380 = 246.938 Newtons

*************************************************************

These results in newtons represent the force that pushes the slave pistons outwards and make the pads come into contact with the rim I hope this helps, its helped me revise anyway, if someone can tell me how many newtons can can exert upon a brake lever, ill be more than happy to give a more trials accurate answer by inco-operating levers + moments into it too Yes I know its quarter to 2 but im bored

night all

EDIT: Yeah that's wrong, I've miscalculated the areas on all the pistons. But just assume the area is right and the ratio is right too, it still works.

Edited March 3, 2008 by PaRtZ

[Ben Cox]

um yeah, what he said lol