The brake parts I had collected were a pair of rear calipers from a 95-98 Porsche 993 (911) with their corresponding discs, and 944 NA aluminium hubs. I wanted to get the hubs to fit stock beetle spindles, as this was much easier than trying to modify the 944 ones which are a different size, and different strut angle to the beetle ones. Making the Porsche hubs fit the beetle spindles could be done it two ways: Use beetle bearings and machine the hub to take spacers, or use Porsche bearings and machine spacers to fit over the beetle spindle. As the beetle spindle is shorter than the Porsche one, it was easier to machine the hubs and fit inserts. Then I can keep the beetle bearings and seals and still use beetle struts etc.
I approached a friend of mine who also happens to be an excellent machinist and engineer. He stepped up to the challenge, and the first job was to make some accurate technical drawings of the parts. I created these with help another friend at my place of work.
 Beetle hub |
 Beetle spindle |
 Hub and spindle superimposed |
CAD image files:
fastbughub.dwb - 0.57MB
fastbughub.dxf - 0.88MB
fastbughub.igs - 2.23MB
Using the CAD images the hub was superimposed on the spindle showing the size of the required spacers. Notice the 2mm (approximate) gap either end of the bearings; this was increased to 4mm by machining out the hub to give the spacer more material.
The base of the hub was machined to clear the spindle, and provide space for the seal. An aluminium spacer was pressed in to hold the seal in the correct position.
In order to machine the hub accurately in relation to the disc mounting face, tools where made up to hold the hub on this surface, rather than just mounting the hub in a chuck:
Tool to hold hub on disc face
Tool to hold hub on reverse disc face
The finished hubs showing inserts and also bearing shells pressed in:
Machined hub outer with bearing shell inserted
Machined hub inner showing insert to hold seal
The total run-out of the assembled system is less than 0.01mm.
Assembled hub
Assembled hub with wheel
The next task is to create a metal plate to bolt to the drum brake spindle and hold the caliper.
