Saturday, March 23, 2013

Swaybar replacement options

Ever more, research and planning is a large portion of this build. While it's often great to come up with ideas and solutions to problems completely on your own, there's no point re-inventing the wheel. Whenever I hit a snag I do my research on forums, google, and other sources in the hope of finding one or more ways in which others have solved the problem or challenges that I am facing.

In this instance, the issue at hand is the front swaybar; some may recall in the post about the engine finally being installed, I had to cut the front sway-bar to clear the sump on the AU motor (http://www.e21build.com/2013/01/some-adjustments.html)



A lot of drift cars remove the front swaybar to smooth transitions when changing direction, however this usually relies on very stiff springs to control the body roll (at this point since I can't drive the car I don't know how stiff cutting the current springs has made them), and more seriously, it requires some form of control arm to hold the rest of the suspension in place.

The E21 front suspension setup is relatively simple - the swaybar performs a dual action as both anti-roll, AND as a front control arm. 

To help understand a little better, I've borrowed the following image from http://carsiparts.com:

Basically the problem this creates for this project is that currently were I to drive the car as it stands, the swaybar sections remaining and the factory sway bar mounts would be taking all the lateral forces of the front suspension as well as trying to seperate the chassis rails at around 30 degrees (thanks to pandemonium001 from http://bmwe21.net for that).

For this reason, I've been trying to think of alternatives, and doing my research on what others are using. It's extremely difficult to find anything from the Group 2 or Group 5 race cars, and buying pre-done custom setups is exorbitantly expensive for my goal of low/no budget on this build. For those of you interested in this but not keen to do the work yourself, and with some cash to splash - check out the tubular front suspension offered by VAC motorsports (http://store.vacmotorsports.com/vac---e21-tubular-race-front-suspension-p2170.aspx) as seen on DavidMcIntyre.org:

Following this discovery I also found a few photos on bimmerforums.com by E21Jason (who may also be Jason_323i on bmwe21.net) of a custom front setup (quite beefy):

 

I also found these images but appear to have neglected to record my sources for them (sorry! if these are your images contact me and I will attibute you accordingly!):


The first one (above) is a full custom arm in-progress, this would require new mounts and I'm under the impression this will limit my already-very-limited category compliance in Australia as some CAMS requirements need the original suspension mounting points to be used,




This setup looks more like what I'll be trying to make, it uses rose joints and stronger mountings but in the factory locations in addition to being able to later add an adjustable swaybar (I think I'll try it without a front sway first, once I've got the control arms sorted)

Initially, I had thought of putting a thread on the remaining sections of swaybar and fitting a large washer and nut and using the original mounts, however it was pointed out to me that these mounts are not built to take a sidewards load, only the load created by the twist of the swaybar, and that they therefore are likely to fail in the use I had intended for them.


This is a poorly proportioned attempt at drawing the front suspension. A-B are normally linked as part of one single swaybar but obviously that is what I have cut. The idea is to beef up brace C which is already an added brace, as it will need to hold the chassis rails together when forces are imparted on the wheels (i.e. in any forwards motion). Mounting points at both A and B will need to be beefed up and hopefully joined to the beefed up member C (which is actually closer to these mounts in real life than in the drawing so not a huge ask).

Pandemonium001 came through with some samples:


And Jason_323i offered up a picture of a previous setup he had used:

And his current setup (which he notes is a work in progress):

This gives me a lot more to work with and a lot of food for thought. Now I just need to get some materials (rose joints and bar stock)!

2 comments:

  1. hi,

    nice research, how did you go with your custom set up? very interested to see how you went.

    cheers

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  2. I still haven't got around to it, although it's slowly creeping into my "do this soon" list!

    ReplyDelete