Pinion Correction Shim

Basic 3D model (OpenSCAD) for making typical pinion or caster angle correction shims for a leaf spring vehicle. User can specify width, length, thickness, angle, center hole size and also type of mounting.

First photo is an example of a typical early model Jeep shim with 1-3/4" width, 4-1/8" length, 5/16" center hole and in this case 4 degree angle.

This model file would serve 2 main purposes:

First, would be to make a 3D printed shim, perhaps to try out varying angles with the vehicle stationary, in order to correct u-joint angle(s). Then, once a particular shim design is worked out, that 3D printed part could be used as a sample to machine a shim out of a more durable material like steel. You DO NOT want to run a 3D printed plastic shim while driving, that isn't safe.

Secondly, you could export a STEP or IGES file and upload that to an on-line machine shop for a quote on producing that part. Or, if you have a local machine shop or know someone that has access to a manual or CNC mill and metal cutting saw, that STEP or IGES file or sample part could be used to duplicate the shim. See: https://forum.lulzbot.com/t/tip-converting-openscad-files-easily-to-step-with-freecad/228

If you need to road test the vehicle, one option is to use some pieces of steel flat bar to simulate the shim. Let's say your shim tapers 3/8" from thick to thin end. You could cut a piece of 3/8" flat bar and a piece of 3/16" flat bar. Drill a center bolt hole in the thinner piece and place it in the center of the spring perch. Put the thicker piece on the end of the perch and tack weld both pieces to the perch, then clamp the spring down with the u-bolts. This way you could do a road test to see if that angle will work. If so, note the angle change and proceed to making your shims. If it didn't fix your vibration issue, adjust the angle with thicker of thinner pieces of steel.

Print Settings

Printer Brand:

Type A Machines

Printer: 

Type A Machines 2015 Series 1

**Rafts:**

No

Supports: 

No

**Resolution:**

0.6mm nozzle, 0.3mm layer height

Infill: 

100%

**Filament:** Zyltech ABS black 
 

Notes: 

With the 0.3mm layer height, the shallow angle creates visible steps on the top surface. This won't affect the actual angle, but printing with a thinner layer height = smoother finish. It could also be sanded on the sloped face to smooth off the layer steps if that's important.

How I Designed This ===================

Background

This is the basic shim design used by 4Crawler Offroad for 25 years in making 1000s of pairs of steel shims. We made all our shims 1 pair at a time on a horizontal bandsaw and milling machine.

The 3rd photo is an example of a finished, high precision, bolt-on steel shim where the cut surface is milled with the shim on an accurate angle jig. The bolt-on version features a smaller center hole for the shank of the bolt to fit through and a flat recess in the angled face for the head of the spring center pin to sit on. This version is meant to be bolted to the bottom (spring over axle) or top (spring under axle) of the leaf spring pack.

The 4th photo is a pair of 8 degree weld-on steel shims. The weld-on version has a large center bolt hole to fit the head of the center pin in the leaf spring pack. This type of shim is meant to be welded to the spring perch of the axle.

The model file can also output a shim with no center hole if desired.

It also outputs, in the OpenSCAD console window, the thickness of the middle and thick end of the shim. This can help determine is a longer center bolt will be needed to install a bolt-on shim or how much lift (or drop) you might expect with the shim.

A further use for this model file is to "reverse engineer" an existing shim you might have on your vehicle. Many times, we've had customers contact us with a mystery shim installed and have no idea what angle it is. If you can get a measurement of the thin and thick end heights as well as the length, plug in the length and the thin end height into the file and adjust the angle parameter until the thick end matches your shim.

More information on calculating drive line angles, etc. on the web page below:
https://www.4crawler.com/4x4/ForSale/Shims.shtml

Category: Automotive