Sizing things up

Team 321 manufactures a general purpose Independent Rear Suspension unit for many front engine / rear wheel drive cars and trucks.

Until application-specific units are available for all makes and models of vehicles, we offer a lightweight model for test-fitting and mockup. This lightweight model is 1/4" thick and dimensionally identical to the steel unit made by Team 321.

Here is an image of an assembled Lightweight model. This one is shown with upper control arms installed.





While many customers have expressed what a great idea it is to offer a lightweight model for prototyping and test fitting, many others have asked how to best utilize if for fitting into their vehicle. Below I show the steps involved in using the lightweight model for mounting an IRS between a pair of bent frame rails.

The specifications for this application is to mount the Team 321 IRS between  2" x 3" frame rails spaced 25 inches apart. The 25 inch measurement is taken from the outside of one frame rail to the outside of the other frame rail. Similar frame rails are available from many sources in all dimensions, bends, etc... These frame rails pictured below were purchased from Jegs and are 2" wide x 3" tall.




The assembly above is the end result of measuring, cutting, measuring, modifying, etc...  There were a few simple steps to get from basic lightweight model to the finished prototype shown above... I'll do my best to cover them below.


After a few measurements to determine relative location of the frame rail to the base IRS center section, I created a 2D drawing of the additional material needed to mount the frame rails. Here is a 3D rendering of that drawing.



It must be noted that this is a prototype, the final IRS assembly will be more streamlined and "finished". This bulky plate is simply for initial fitting to verify clearance of all components. It's far better to make things too big rather than too small initially. It is easier to remove material vs. having to add material.


The 2D CAD drawing is transferred to 1/4" thick masonite board and the appropriate holes, cutouts, etc... are made.



Then a second piece is made - using the first one as a template.




One half of the assembly is bolted together for initial fitting.



Similarly, the second half is bolted together the two are joined by threaded rod through locating holes at the base of the assembly. It is not free-standing and the frame rails can be fit.




Since the center pieces are symmetric, there is no need for concern with which side if front / rear... The next photo show the frame rails passing through the rectangular holes made in an earlier step. An upper control arm is also installed to confirm clearance.




As you will see, the good thing about using such easily modified material is to address changes quickly and easily.

After the initial assembly, it was clear that there was not enough room between the frame rail and the upper control arm. The upper control arm swings through an arc of roughly 30 degrees up and 20 degrees down.

Here is a shot of the piece of the rectangular slot that needed to be enlarged to move the frame rail up, and thereby clear the upper control arm through it's pivot range. The green arrows and circle point to the part that needs to be removed...



Here is a zoom'd in view of the same area... it is about 1/2"



Once this cut is made and the frame repositioned... The control arm is free to rotate up to 39 degrees.





... and able to rotate down 35 Degrees





The single bend Frame rail fitting is complete... now it's time to test fit the assembly with a double bend frame rail.

Now that the prototyping is complete, it's time to make the steel pieces. The center section needs to be changed to properly locate the two frame rails. With a few measurements, I made the changes to the CAD drawing and had new pieces cut with a CNC plasma. Here is a shot of the resulting assembly.



... and here are two images of the finished prototype with upper / lower control arms, spindles and brakes.







If you have an application for an IRS - let me know some general dimensions / clearances / etc... and I can provide a lightweight model for test fitting.

Email dave@team321.com with any comments / questions.