smart51
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| posted on 5/7/07 at 09:06 PM |
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brake, wheel, king pin alignment
In a 3 wheeler with a single front wheel does the king pin, wheel centre and brake disc centre have to be inline to stop brake steer or can one or
other be offset?
If the king pin is offset with respect to the wheel, will the steering pull to one side?
If the brake disc is offset with respect to the wheel, will it pull under braking?
If the brake disc is offset with respect to the king pin, will it pull under braking?
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DavidM
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| posted on 5/7/07 at 10:54 PM |
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I'd have thought it would be the same as a motorbike, Wheel must have central pivot else it will always be pulling to one side. Brake disc
doesn't matter as the reaction under braking will be dependant on wheel/pivot relationship.
David
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blakep82
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| posted on 5/7/07 at 11:35 PM |
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I think (don't know for sure) that king pin angle etc will always try to pull in one direction, it works on a car because both sides try to pull
in different directions with the same force, balancing out, and making the car go straight?
I think motorbike style would be the right way, or look at a reliant 3 wheeler, and copy
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nitram38
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| posted on 6/7/07 at 08:49 AM |
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KPI is not for driving the car straight. This is done via castor. (Remember a shopping trolley).
It is there to reduce scrub on your tyres.
If you draw a line through your kpi to the tyre tread patch, you would want it to intersect the ground as close to the centre of the tread. (This is a
simple explaination because kpi can be positive and negative aswell) This means that when you turn the tyre it is turning on a tight rolling radius.
If your kpi is too much over from centre of the tread, then as you turn, some of tyre will drag across the ground, hence scrub.
On a trike the head stock normally is angled so that as you turn the tyre rolls over on to an edge. This is effectively doing the same as kpi and
castor.
If the head stock was directly vertical, I think that you would then suffer from tyre scrub and have no self centering.
Don't ask what the angle is as I don't have a clue!
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Peteff
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| posted on 6/7/07 at 08:53 AM |
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If the brake disc is offset with respect to the wheel, will it pull under braking?
I don't understand this bit, The brake disk must be parallel to the wheel and on the same centre or it will be eccentric won't it ? I have
a single sided disk on my bike front wheel and when the tyre pressure was low it did skew the front under heavy braking and wore the tyre heavily on
one side
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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smart51
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| posted on 6/7/07 at 09:35 AM |
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quote:
Originally posted by Peteff
I don't understand this bit, The brake disk must be parallel to the wheel and on the same centre or it will be eccentric won't it ? I have a
single sided disk on my bike front wheel and when the tyre pressure was low it did skew the front under heavy braking and wore the tyre heavily on one
side
Of course the brake disc will be parallel to the wheel. What I am asking is, viewed from above, does the brake disc have to be in the centre of the
tyre, or can the disc be mounted to one side?
 
Rescued attachment wheel.JPG
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Spyderman
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| posted on 7/7/07 at 12:17 PM |
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It makes no difference where the brake disc is in relation to wheel or kingpin centres. The braking force is through the contact patch between wheel
and road.
Looking at it the other way around, if there was a torque reaction then most super bikes would fall over under acceleration as the chain sprocket is
on the side of the wheel.
The kingpin centre needs to point through the centre of the tyre, otherwise there would be a drag to the opposite of offset side. Also the tyre
contact would move forward or backward depending on which way you were turning.
If offset was to right, tyre contact would move forward when turning right and backward when turning left.
The constant pull of an offset kingpin centre could become very tiresome, but would certainly wear the tyre unevenly.
Spyderman
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smart51
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| posted on 7/7/07 at 03:05 PM |
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Thanks spyderman, that's what I wanted to know.
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