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#Post#: 12239--------------------------------------------------
Where to put the camber in front axle
By: carl.kirk Date: January 8, 2025, 3:06 am
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I fully understand the workings of camber and intend to put a
small amount of positive camber into my axle design. What I
don’t understand is why so much negative camber is designed into
the yolk pivot point on the axle beam, only to then reduce it
with positive camber in the mounting of the axle stub in the
yolk? Why not start with a neutral pivot point and introduce
positive or negative camber when mounting the angle of the axle
stub? I am not playing devils advocate, I just simply don’t
understand and having built my axle, I now need to cut it to
length and weld on the pivots but don’t want to have to cut and
re-weld if I get it wrong
#Post#: 12240--------------------------------------------------
Re: Where to put the camber in front axle
By: carl.kirk Date: January 8, 2025, 4:53 am
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I notice on the baby2 Bugatti, they have a degree of negative
camber in the pivot but the positive camber is created with the
yolk design, not the angle the axle stub is welded in. If, as
they say, this is an accurate representation of the full size
car, then it would make more sense to follow this method, rather
than make the yolk a generic uniform cart design shape and then
try to weld the stub axle into the yolk at an angle to create
the camber needed?
#Post#: 12242--------------------------------------------------
Re: Where to put the camber in front axle
By: Graham Hill Date: January 8, 2025, 6:20 am
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Gemini Karts will make a bespoke version of their front axle if
asked.
Last year I was using a spare early prototype with 12 degrees
KPI and 3 degrees positive camber on the welded stub. I've
experienced a lot of wheel hopping around fast corners (I do run
a fixed rear axle).
Their standard axle is now 16 degrees KPI with zero camber. I am
having another made using the 16 degrees KPI and 2 degrees
positive camber (for period look, not performance). I'll see how
it performs this year.
#Post#: 12244--------------------------------------------------
Re: Where to put the camber in front axle
By: carl.kirk Date: January 8, 2025, 7:07 am
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Hi Graham, what is KPI please? I took the 16 degrees to be the
camber if a straight stub axle yoke were mounted to it ( which,
I’m assuming, without a positive camber compensation on the stub
axle when it is mounted to the yoke, would bring the contact
patch to the edge of the tread?)
I am making my own because I am trying to create a T 35 axle as
close in looks to the original, so the final height of the
wheels relative to the body and the mounting point of the
springs all need to be created from scratch, this would be
expensive to commission someone else to make and I am more than
comfortable with the fabrication plus I enjoy doing it myself
#Post#: 12246--------------------------------------------------
Re: Where to put the camber in front axle
By: Jimr1999 Date: January 8, 2025, 7:11 am
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Think I am about following you Carl, the KPI needed for most
axle set ups to achieve a contact patch intersection for pit
bike wheels (17") and tyres is about 15[sup]0[/sup]
So the angle of the king pin in relation to the wheel should be
that if you want an intersecting scrub point at the center of
the tyre.
The Camber is independent of that KPI inclination but does add
to or detract from where you weld it. If that's what you mean?
JimR
#Post#: 12247--------------------------------------------------
Re: Where to put the camber in front axle
By: carl.kirk Date: January 8, 2025, 7:21 am
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Thanks Jimr1999, so KPI means contact patch intersection! I am
using pit bike wheels and looking for a bit of positive camber.
Looks like I will have to do a scale drawing then!
#Post#: 12248--------------------------------------------------
Re: Where to put the camber in front axle
By: Jimr1999 Date: January 8, 2025, 7:25 am
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KPI, King Pin Inclination... Determines where the line
extrapolated through the king pin will meet the ground in
relation to the contact patch of the tyre.
Hope this helps.
JimR
#Post#: 12249--------------------------------------------------
Re: Where to put the camber in front axle
By: carl.kirk Date: January 8, 2025, 7:36 am
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Thanks Jimr1999
#Post#: 12251--------------------------------------------------
Re: Where to put the camber in front axle
By: Jimr1999 Date: January 8, 2025, 9:39 am
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If you add camber, the KPI stays the same.
#Post#: 12252--------------------------------------------------
Re: Where to put the camber in front axle
By: jon.pearce Date: January 8, 2025, 9:54 am
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You would have to put a ridiculous amount of CAMBER on to make a
15 or 16 degree King Pin Inclination not work with 17 inch
wheels
(I have used 15 degrees KPI with 17 inch wheels and 2.75 tyres
on my Small CoGNac build, with ZERO CAMBER).
Interestingly, anyone building a GN or Fraser Nash type front
axle should be aware that the CASTER decreases with suspension
compression.
I have used 9 degrees of CASTER static.
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