Thanks for the interesting discussion. This brings out some of the challenges with designing and fabricating aluminium components. My comments relate to hubs designed to fit R31 / HR31 struts: each hub has one large tapered roller bearing inboard and one smaller tapered roller bearing onboard on the spindle. Later models typically use large, very wide double row bearings. Regarding the installation and subsequent removal/replacement of bearings into aluminium alloy hubs, the following suggests how. Calculate the desired interference fit between the bearing race and hub at an operating temperature of 150 degrees C, which is the practical upper temperature limit for continuous operation of the hub. For standard size bearings, say, NTN 4T-LM67010 (inboard) and NTN 4T-LM11910 (outboard) or their equivalents, the interference fits are significant. Pressing the races into an alloy hubs with very tight fits comes with a high risk of damage to the hub. Here's what you will need: a quantity of liquid Nitrogen, an oven, appropriately sized tapered drifts for installing the bearings, a hammer, a couple of short lengths of timber dowel to which some wire or thin sheet metal can be attached and safety gear including insulated mits used for furnace work, and full face shield. CAUTION: BOTH EXTREME HEAT AND EXTREME COLD CAUSE SERIOUS BURNS!! Take one hub and heat in the oven to 200 degrees C. Install the outer race of, say, the inboard bearing onto the piece of dowel ... held in place lightly with the wire or piece sheet metal (use a screw to attach the wire or sheet metal to the dowel to keep it in place). The bearing race should be installed on the piece dowel - this needed to get the bearing race into the right position so it can be installed into the hub. Imagine the dowel standing upright with the wire or thin sheet metal at the lowest point ... place the bearing race with the widest part of the taper pointing downward. The piece of dowel will be your tool for firstly placing the bearing race into the liquid Nitrogen to get it cold (nearly minus 200 degrees C). When it is cold, withdraw it from the liquid Nitrogen and feed the free end of the dowel up through the hub (which you have just removed from the oven). This will pre- position the race for what follows. Carefully invert the hub ensuring that the race is held roughly in position. In preparation for using the drift and hammer to tap the bearing into place, carefully turn the hub over so the bearing is now uppermost pull the dowel down and through so it just releases the bearing race ... hold the bearing in position with the right sized tapered drift before QUICKLY and carefully tap the race into its home position. Initially, when the temperature difference is around 400 degrees C, the race will be a loose fit in the hub, BUT the heat transfer occurs quickly and if you waste any time the bearing race will get stuck part way in. Best idea is to have a few mental rehearsals before attempting to do this for real. It's easy to do, but you must be prepared and move quickly and confidently but not hastily. Repeat until each of the outer bearing races are installed. Once the bearing races are installed this way they are NEVER going to come loose during operation. Whilst compressive "hoop" stresses are very high, this will cause no damage to either the bearing race or the hub. IF you ever need to remove a bearing race to replace a bearing (unlikely, because if the bearing has worn out your hub has probably reached the end of its fatigue life anyway), you will need an arc welder. Simply run a good thick bead of weld along the inner face (the surface where the rollers run). This should be 25mm long or so, repeat two more times, leaving a gap between runs. Leave to cool down to room temperature and carefully tap the bearing race out from the inside. If you have not provided recesses so the back face of the bearing can be accessed, you will need to weld a piece of steel rod or similar to the bearing to use as an extraction tool. If you have been careful when welding, there will be no damage to the hub and the old bearing race will come out with just a little pursuading. For the standard bearing sizes mentioned, the recesses in alloy hubs made of 6061-T6 or, say, 5083 will be 59.05+0.00,-0.05 and 45.20+0.0, -0.05 millimetres respectively. If you choose to make hubs out of steel CrMo 4140 or similar, just use the same sizes for the bearing recesses as OEM cast iron hubs.
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