wishbone plans

Wishbone Manufacturing Plan

By Andrew Chang 1/26/2024

***If you have never done a step ask someone to watch/help!!!***

Initial considerations

Front lower & upper wishbones need to be rejetted
Rear upper wishbone needs to be rejetted or height reduced accurately
All upper holes 1/-4-28, all lower 5/-8-18. All threads are fine unless otherwise listed.
Use front wishbones with messed up dims as practice beforehand

Manufacturing plan

FACING

ONLY FOR FRONT UPPER WISHBONES: Measure thickness of faces shown below. If any of these are not within tolerance, record how much material must be removed.

Figure 1: wishbone top view

Figure 2: wishbone front view

Setup 1: clamp wishbone like U-shape into vise.
Edgefind z and face the 3 top-facing sides until tolerance is met. Also face the 2 ends on rear wishbones. Edgefind every time you switch setups.

Setup 2: clamp wishbone like v-shape into vise. Repeat step 3.
Setup 3: clamp wishbone onto table utilizing t-nuts and other workholding tools. Face top side, adjust nuts and bolts, and face remaining areas that were covered.
Setup 4: flip the wishbone over. Repeat step 5.

DRILLING & TAPPING

Clamp the wishbone bottom-up (like a U shape) into the vice and edgefind x, y & z. Note that when edgefinding x you are touching off a single edge, not a face, due to the sloped surface. If the edge is not orthogonal, mill it until it is.
Double check the drill & tap chart that tool sizes below are correct. Drill center pilot hole first; use its location as reference point for drilling/tapping other holes.

Only for rear lower wishbone: drill rear tie rod tab hole (same setup)
Only for lower wishbones: Using v-bit or dull drill bit, score light marks above and below center pilot hole as shown below; this will be used to position tab when welding later.

Figure 3: center hole scoring location

Once side holes are drilled & center hole is piloted, use drill press to drill through center hole.
Tap all holes, using tap size listed above

TAB CONSTRUCTION

Find a piece of aluminum stock from scrap pile that is at least 1.25x1.1x0.8”, and square it. Leave at least 0.05” from nominal dimensions for precise facing.
Use edgefinder and face precisely to nominal dimensions.
New setup - Drill the ¼” hole.
Use a bandsaw to make a rough cut of the inner channel. This is technically optional but highly recommended as it will save lots of milling time.
Mill the inner channel to nominal dimensions. Use the same tool and feeds/speeds as the wishbone facing operation.
Use belt sander to create fillet. The contour does not need to be exact. However, DO NOT TAKE OFF MORE THAN NEEDED. Better to leave a bunch of extra material than take off even a bit too much.

TAB WELDING

When welding the tab onto the wishbone, line up the x & y position. X (lengthwise on wishbone) is the more important dimension.
After welding is done, ream all holes to account for thermal expansion from the welds.

Tolerance considerations

Notes

USE CENTER HOLE AS DATUM: the most important dimension here is the distance between holes. Therefore, after edgefinding you must drill the center hole first and then use that hole location to set the location of the two side holes. This will 1) minimize stackup error and 2) ensure accurate center hole location
For lower wishbones, the distance from hole to flat end (where rear tie rod mount attaches) is also an important dimension to get during facing.
Have coolant handy in case part starts to get hot.

Rear tie rod feedback

To do: