Live axle location & setup

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Will01
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Live axle location & setup

Post by Will01 » Mon Sep 30, 2013 12:08 pm

Hi Guys
This is to help with my Capri Track build, but then it maybe will come in handy for others running a live axle.
I am currently building a Mk3 Capri to be used mainly as a track car, not really bothered about road driving at this point.
I have already decided that the front end will feature compression struts at some point to add in extra adjustability, but now its time for the rear. It would be great to make the rear end as adjustable as possible, but still keeping the original character of the car e.g. leaf springs and no 4 link arms etc. I don't mind adding more items to the shell, but i really don't want to cut much off the shell e.g. 4 link boxes.
There seems to be quite a few many people out there producing leaf springs for competition, for now i will be using second hand 2.8i single leaf springs.
I know that by adding to the rear axle assembly i will be increasing un-sprung weight, maybe a few little tweaks will help keep this as minimal as possible. But again advice in this subject is much appreciated.

I have taken an extract from the thread in 'Readers cars' (see below)
For the Capri like may live axle cars there are plenty of options for controlling rear axle location with plenty of people offering different kits e.g.
- Axle Triangulation Kit
- Panhard Rod
- Watts Linkage
- 4 linked kit
Personally i think for what i am building the car for i would really like to adopt a Watts linkage. I do have my reasons and in time i will try to explain.
To start with though i don't want to change the original character of the car too much from OE specification as then it isn't really a Capri. Therefore i will not be fitting 4 link boxes and ditching the leaf springs. Maybe this will change later but i really want to try and keep the leaf springs for originality.
I don't really like the idea of the panhard rod as it really doesn't keep the axle centered under both right and left handed corners, whereas the Watts linkage allows you to keep the axle centered. I will eventually go into more detail but that should be fine for now.
From what i can see there are not too many people out there with a Watts linkage and rear leaf setup on a Capri, therefore it looks like i will have to adapt my own kit maybe from an Escort Mk2 or start from scratch?

The next thing i can see is i have a couple of options with Watts linkage setup.
- Watts linkage with pivot built into differential housing plate (possibly make this slightly adjustable with a slight re-design of the crank?)
- Adjustable roll centre Watts linkage which attaches to axle tubes? There seems to be many different types on the US market. Experience anyone?

Does anyone have any advice on Watts linkage setups and try to give some pros and cons of each?? All advice would be much appreciated as i need to work out how i will attach to the vehicle whilst i have the shell stripped down.
I have noticed there is a range of books e.g. Engineered to Win etc which may come in handy, but it would be great to get other peoples input also.
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Will01
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Re: Live axle location & setup

Post by Will01 » Tue Oct 01, 2013 11:55 am

Since the Capri is going to be built as a track car and also something to test me in what i have learnt over a good few many years, the car will need to be adjustable.
This is why i have chosen to go the route of compression struts on the front end and use a Watts link for the rear.
With a Watts linkage there is obviously an optimum point to control axle movement and allow behaviour adjustment of the rear end control. (sorry if that very basic).
Since the rear end of the car will be adjustable for ride height i think the best way forward is to use an adjustable Watts linkage. This means i will be able to fine tune the roll centre for the rear of the car depending on how the rest of the suspension is setup.
I can't understand why the rally boys in the Escort Mk1's & Mk2's have fixed Watts linkages as these guys i would have thought would be constantly changing ride height for different surfaces and terrain.
I have the plan in my head, but without going out and buying lots of different kits does anyone have advise on what would be best?
Otherwise it looks like i will have to design from scratch and this means i also need to get a proper idea where to start.
Any advice would be greatly appreciated.
Will
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Will01
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Re: Live axle location & setup

Post by Will01 » Sun Oct 20, 2013 8:22 pm

I have spending a little free time in my lunch periods drawing up in CAD a couple of different ways to design a simple watts linkage. One of the drawings includes a fixed roll centre design, the other designs show different ways of attaching a watts linkage to the axle and vehicle body. Both look similar in design until the body starts to roll or go through bump.
I will eventually measure up the axle and body to try and get the designs to scale.
Looking through the internet its hard to see if anyone has done this before on a Capri, however I can see clearly that there are many kits available in the US, Australia and NZ.
The main cons against using one of these kits is cost and they have not been developed to be used with an Atlas axle. With this information I think it would be foolish at this.time to.design from scratch, however it may actually be quite easy to build in some adjustment to the standard watts linkage kits that are available for the mk2 escorts. I may post a few different ideas on here in time. This is definetely something that I want to sort out whilst the shell is stripped as it will be alot easier to work on in this bare state.
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zdrafko51
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Re: Live axle location & setup

Post by zdrafko51 » Mon Aug 10, 2015 11:46 am

I'm building Lada 2105 VFTS and we(my team) also where doing some CAD (Solidworks, Inventor) designe and testing, and read some books on that subject. In my opinion and what I read in books, watts linkage is the best solution for live axle. We will drive rally and we choose to have adjustable RC, why Escort MK1, MK2 don't I really do not understand. In rally you have jumps and your suspension is working in great movements so for me it is inportant to have not only adjusteable RC but you have to move you pivot point to the chassis. Something like that http://www.raceproducts.net/adjustable- ... s-linkage/, study a bit australian v8 supercars... Pivot point determine roll center and in my opinion specially in rally, you want your roll center to be fixed to your GC (gracity center) and not to the ground like they have..., if your GC and RC are not fixed than you have oscilating suspension, other words you never know what is gonna happend...
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Will01
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Re: Live axle location & setup

Post by Will01 » Mon Aug 10, 2015 12:01 pm

I know of a few properly setup Escorts that have adjustable roll centre watts linkages, but the ones most people fit are fixed. After doing the reading myself like you i find that for my uses i need to adjust, but maybe the fixed ones are ok for most uses and drivers. I just want to play with as much adjustability as possible so i can find what works best. At the moment i only have choice of two tracks Knockhill & Croft.
I am building my own car as a development fun tool, it is important for me to test what theory i know of and put into practise.

I am looking at building my own version of the peg type you linked to, but i am also investigating being able to adjust in situ by having lead screw and mount inside the car. So the Watts bell is mounted on some sort of elevator type arrangement.
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zdrafko51
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Re: Live axle location & setup

Post by zdrafko51 » Mon Aug 10, 2015 2:17 pm

Yes, probably on Escorts that is good for most drivers and uses. We to are building a car from scatch (as you said for fun and learn), combination of Fiat/Lada and custom build parts (especially suspension, because Lada is't som sports car :-( ). Because of so many changes on suspension we want it to be adjustable as possible.

For adjusting watts from the cabin look for v8 supercars on youtube and goole, they have it, you will need just to bring it to your hand...
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