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Rear subframe inclination and caster angle
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Author:  Sonora [ Sun Dec 28, 2014 9:43 pm ]
Post subject:  Rear subframe inclination and caster angle
Hello

Nice to meet Cox owners on this Forum !

I am restoring a Méan Sonora built with a Mini engine. It could be the only one, out of 200 Sonora's, using a Mini engine.

For history of this car, please read

http://maximummini.blogspot.be/2011/12/ ... ora-1.html
http://maximummini.blogspot.be/2011/12/ ... ora-2.html
http://www.maximummini.blogspot.be/2014 ... ora-3.html

The original chassis is completely rotten, so I decided to build a new one. While doing so, I see there are many defects that I try to correct. The car was indeed built in a hurry, based on a chassis built for another engine, and using parts from a damaged Mini. The original Mini subframe was bent and repaired , and the Méan chassis was built around it ! I now use a new unbent subframe !

My question is about the vertical position or tilt of the subframe and the caster angle.

Because the subframe is at the rear, do I need to keep the Mini 3° caster angle ? Some people tell me it should stay like that. Others tell me the caster angle should be 0° at the rear. However, the car builder, Jacques Dheur, has modified the inclination of the subframe to make the coil springs of his suspension vertical. See picture 5958. This modifies the caster angle completely. And I do not know by how much because I have no information about the original position of the subframe in a Mini. What to do ? Original 3°caster, zero caster, or vertical columns ? What is the original position ?

I assume this problem must be solved by the Cox GTM users who also have the engine at the rear.

Can anyone help me ?

Your help and comments will be appreciated !

Louis Lempereur

Attachments:
File comment: The Mini subframe has been tilted to make the columns vertical. This modifies the caster angle probably to a negative value. Does this bother ?
DSCN5958.jpg
DSCN5958.jpg [ 125.56 KiB | Viewed 5068 times ]
Author:  West [ Tue Dec 30, 2014 9:09 pm ]
Post subject:  Re: Rear subframe inclination and caster angle
Welcome to the forum

I will hopefully have some time at the weekend to try and answer your questions/share some thoughts. That will either help or confuse :lol:

Neil
Author:  guru_1071 [ Mon Jan 05, 2015 12:11 pm ]
Post subject:  Re: Rear subframe inclination and caster angle
Louis

nice project!


you don't need to worry about the castor at the rear as it has no affect on the car - it can only be checked by turning the wheels 20deg left, then 20deg right, which obviously you cannot do as the steering will be fixed.


all you need to be able to set is the height and the toe/tracking - I would set the subframe as per in a mini / gtm - i.e with the towers vertical

its worth buying the road going version of the rossabits (he posts on here) rear kit to be able to control/set the tracking as its a nice, safe and easy to adjust kit - if your car has a method of locking the rear steering that was used on the early cox/gtm its very hard to get the tracking right - mine was a nightmare!

keep us updated with your project!
Author:  West [ Tue Jan 06, 2015 10:24 pm ]
Post subject:  Re: Rear subframe inclination and caster angle
Apologies a bit busy at the minute myself so a quick note.

Castor, as above, does not exist on the rear as there is no degree of freedom as things should be locked with the toe link.

The position of the top ball joint and bottom joint do need to be the same side to side in a side view.

Angle of the subframe will depend more on where you want the imaginary swing arm for ride quality and considering things such as anti squat.

I am currently modelling the rear end of my car in CAD and the angle of the subframe is one of the things I am slowly looking into on the side as I am replacing my subframe with a tubular one. I believe it is not set with the towers vertical but tilted back very slightly, I also want to try and compare the angle of the subframe compared to my brothers Mini.

Not a 100% answer but I am looking into things. With my CAD model I could work out some dimensions to position the subframe the same as a GTM if you want to do a straight copy.

Neil
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