Solid and Acetal bushings

Sat Dec 31, 2011 1:24 am

Hi guys, rebuilding my drift spec literally from the ground up and turning my own bushings. Problem I face is the rear sub frame bushings. Neither were taken out in tact so I need measurements in order to make some new. The main measurement I am after is the ali insert length. Both of mine have snapped and no idea where the pieces are. Anyone got some tech drawings of them or the length? Lol

Sat Dec 31, 2011 5:50 pm

I think that what you're looking for is info on these:

I have a drawing somewhere in my files at the office from the person who originally made those shown. I'll see what I can dig up for you when I am back at work next week.

Tue Jan 03, 2012 12:25 pm

PDF drawing of rear sub-frame bush for download here

Take Note: These are two piece solid steel bushes for track use only. The top and bottom halves need to be pressed into the top and bottom of the sub-frame with an hydraulic press. If you would prefer to make these from a softer material (acetal, nylon, HDPE etc) then I recommend that you manufacture an inner and an outer steel sleeve (with shoulder on the outer piece) and then bush it with your chosen material, rather than manufacturing the whole piece from the softer material. There is a good chance that if you make the whole piece from a polymer/plastic that the shoulder will tear away and the entire bush could come loose in the frame. Make your softer bush and inner and outer sleeves separate with the bush slightly oversized, then press the three parts together with a press, and then install in the sub-frame.

There are many variations on this design. Removing the shoulder from the top half facilitates a one piece design, but increases the likelihood of movement. Total bush length should be 104mm if you opt for a one piece design.

Wed Jan 04, 2012 2:38 pm

GeoffBob you are a legned my friend!! this is so perfect... I was thinking Aluminium singlepiece but it is more than likely going to be Acetal with a stainless centre insert with a large shoulder both sides. would people be interested in drawings and FEA analysis on strut mounts and bushings on here? im remaking most everything on the car myself lol,

Wed Jan 04, 2012 4:12 pm

You're welcome Rory.

If you plan not to sleeve the outside then be sure to put a fair size shoulder on. A stainless centre tube sounds about right. I also have in mind that you may be better off with Nylon as it has greater elasticity (I think) than Acetal (someone correct me on this if I am wrong please) although Nylon doesn't machine up as nicely as Acetal does. Also, be sure to make the bush oversize (on its diameter) so that it compresses when pressed in. That way, if it takes a knock it will tend to spring back, as opposed to permanently deforming till the point where is works loose. Keep in mind that most of your plastics can suffer permanent deformation a lot easier than say polyurethane rubber. Imagine hitting a thick sheet of Acetal hard with a large heavy ball-peen hammer. You will leave a dent. Enough hammering round a track and a plastic bush can come loose, so I urge caution when bushing anything yourself.

Best of luck
Geoff

Wed Jan 04, 2012 5:01 pm

this is good info Geoff. i wil defo take this in to consideration. i might now set off and do abit more research on the topic! find ouit exactly why poly is used instead of the others. In uni now for another semester so i think some lectureers may be contacted

i will keep the Zone informed...