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#Post#: 14144--------------------------------------------------
Ackerman - with Gemini front axle
By: SteveP Date: December 8, 2025, 7:54 am
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I�m planning to have an 1800mm wheelbase on my CK.
I�m told that the Gemini complete front axle, with kingpins and
steering arms is set for a 1675mm wheelbase (with 1/8� toe-in)
Will going to 1800mm mess up the steering/handling - or is it
not that critical?
#Post#: 14146--------------------------------------------------
Re: Ackerman - with Gemini front axle
By: Ian F Date: December 8, 2025, 11:27 am
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True Ackermann has the intersection of the steering arms at the
centre of the rear axle. This was to stop the solid rubber
tyres of Ackermann juniors pedal car squeeling on the polished
wood floor of Ackermann seniors music room.
We use pneumatic tyres that distort significantly in cornering,
so whilst a degree of Ackermann is beneficial, you dont need to
achieve the theoretical perfection. I reckon you will be fine
;D
#Post#: 14147--------------------------------------------------
Re: Ackerman - with Gemini front axle
By: Jimr1999 Date: December 9, 2025, 3:14 am
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Depends upon what steering mechanism you use as well Steve. If
you are using Pitman arm, then there are 2 basic set ups -
1 the take off point from the bottom of the pitman arm is the
same for each connecting rod in which case the Ackerman will be
as the Gemini designed
2 The take off points on the bottom of the Pitman arm are
seperate (side by side) In which case the Pitman arm will have
the effect of adding Ackerman
See page 20 here in the PDF on the first post here...
https://cyclekartsgb.createaforum.com/tech-forum/a-'potential'-builders-guide/
JimR
#Post#: 14148--------------------------------------------------
Re: Ackerman - with Gemini front axle
By: SteveP Date: December 9, 2025, 3:59 am
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Thanks Gents.
I�m using a rack. not pitman arms.
#Post#: 14150--------------------------------------------------
Re: Ackerman - with Gemini front axle
By: Jimr1999 Date: December 9, 2025, 4:11 am
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Moving the rack forward or rearward of a straight line on plan
wheels straight ahead, take off point to rack to take off point
alters Ackerman positively or negatively - see drawing below. So
you have a little to play with if you want to get it bob on. I
doubt it will amount to much difference in feel but if you are a
purist, this avenue is open to you.
JimR
#Post#: 14151--------------------------------------------------
Re: Ackerman - with Gemini front axle
By: RhysN Date: December 9, 2025, 4:15 am
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Ah, that old Ackerman topic, it comes up quite often. None of
the racing cars I have been involved with for over 50 years use
it. It doesn't even get mentioned in most racing suspension
references. All sorts are used. The dirt oval cars that slide a
lot use reverse ackerman, the Formula Fords I was involved with
had zero. Always your decision, IMHO nothing is totally correct,
nothing is totally wrong.
Rack position can affect bump steer, that's much more important
to get as near zero as you can. Build in a means of adjusting,
and play, the best way to learn what works is by experimenting.
#Post#: 14156--------------------------------------------------
Re: Ackerman - with Gemini front axle
By: SteveP Date: December 9, 2025, 5:27 pm
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Some suck it and see then!
I�ll set it up straight to begin with, with an eye to making
adjustable rack positioning possible.
Thinking of my mental health, hoping I don�t get it wrong and
suffer Ackermanic Depression!
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