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#Post#: 6757--------------------------------------------------
brake calipers - does it matter where the disc is grabbed?
By: Tinworm Date: May 9, 2022, 6:16 pm
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I have a very tight space inside the back of my kart, so I
wondered if the caliper has to be in a particular position,
relative to the disc? I mean, for instance, could I mount it
behind the disc instead of in front of it or on top of it?
Are they directional, or is it irrelevant where the disc is
grabbed and whether the wheel is going up-hill or down?
#Post#: 6758--------------------------------------------------
Re: brake calipers - does it matter where the disc is grabbed?
By: Jimr1999 Date: May 10, 2022, 12:21 am
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As I understand it...
Provided the mounting points can take the strain, your
constraints will be that the pads are fully within the area of
the disc and not overhanging (this can lead to the pads touching
each other when worn in and not braking the disc), the caliper
body or retaining pins are not rubbing the rim of the disc and
that you can bleed the caliper somehow with the bleed nipple at
the highest point.
I got around the bleeding bit by bleeding the caliper off the CK
on a spare disc (it is mounted on flexible hose) and then
underslinging mine. Not the easiest thing to bleed but do able
with a bit of patience and time.
Hope this helps
#Post#: 6764--------------------------------------------------
Re: brake calipers - does it matter where the disc is grabbed?
By: Tinworm Date: May 10, 2022, 4:42 am
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Thanks Jim, I think that answers it.
I thought that I might have my caliper at the back of the car,
behind the axle.
How large will your disc be?
#Post#: 6765--------------------------------------------------
Re: brake calipers - does it matter where the disc is grabbed?
By: Jimr1999 Date: May 10, 2022, 4:52 am
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Mine is 220mm but my wheel is a smaller radius than yours I
would think,
#Post#: 6769--------------------------------------------------
Re: brake calipers - does it matter where the disc is grabbed?
By: Tinworm Date: May 10, 2022, 1:46 pm
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when you are braking, is the size of wheels relevant? We all
have the same horsepower
#Post#: 6770--------------------------------------------------
Re: brake calipers - does it matter where the disc is grabbed?
By: Jimr1999 Date: May 10, 2022, 2:08 pm
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Probably more relevant is the contact patch and the CoF of the
tyre as when that slips your brake has done its job, but the
force transferred down the bigger lever of a large radius wheel
to the fulcrum/axle has to be counteracted by a larger radius of
the disc or greater pressure on the pads to make that happen.
Stefan helped me with the maths on mine <hat tip, yet again
Stefan>, he has some great graphics he shared and I think he has
written much about braking on this site. Well worth tapping his
brains on this subject.
#Post#: 6772--------------------------------------------------
Re: brake calipers - does it matter where the disc is grabbed?
By: synthpunk Date: May 10, 2022, 3:35 pm
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Ive been working on this very conundrum. It’s a saga worthy of a
thread on its own, but since you’ve already started one, I’ll
join in..
The long and short of it is that I’ve made a very curvy, strong
and attractive unibody cyclekart from wood. I did the wood bits
first because that’s my happy place, and I sort of assumed by
the time brakes became relevant I’d be far enough along the
metalwork and mechanics learning curves to work it out, and
simply weld a suitable bracket on somewhere, somewhen, somehow.
That time it appears is now. The problem I have is that
everything’s made of wood, so it’s really hard to weld things on
to. And there are no parallels or right angles to take a datum
off, so it’s difficult to think of a way to get the calliper
parallel to the disc anyways…
This led me to the thought that I needed to weld up some sort of
subchassis that holds the engine, transmission, axle and brakes
together in a hopefully square, not too heavy, easily removable
unit…
Which in turn has led me to several conclusions, via cutting up
lots of metal, various major backtracking moments and a few
moments of clarity to several more refined conclusions-
1- build a sort of subchassis that bolts in the back and holds
everything in place
2- get slightly sidetracked, and think of a way to equip said
subchassis that so it has the ability to add rear suspension, in
some way.. preferably that doesn’t weigh much. Probably using
rubber…. Because I like it.
3- get completely sidetracked, end up coming up with a way of
making a ‘floating calliper mount’ sort of affair that holds the
calliper in perfect alignment at all times, is totally
adjustable, and in effect even would allow me to use it in my
original, ‘no weld’ scheme of lightweight bolted aluminium
engine mounting, thus negating the need to even bother with the
inevitable extra weight penalty of either options 1 or 2…..
although suspension to make up for the total lack of twist and
flex in my chassis does sound good…
So the caddy for options 1 and 2 was already halfway built as it
goes, before I came up with option 3 whilst thinking in the
shower on Sunday morning, so I think I’m going to end up trying
all 3.
Tomorrow or Thursday after the postie has been I’ll post some
pics of the brake calliper arrangement. It’s mostly made of
Righettit parts, so not the cheapest option but still a fraction
of the price of a Kelgate floating brake system for Pro karts.
Pics to come… cheers!
Rich
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