Hub To Halfshaft Friction Welding
Posted: Tue Jun 14, 2016 7:29 pm
Hello All, this is in response to my other post "WANTED - YOUR WORN OUT REAR HUBS AND OLD HALFSHAFTS!"
Here's the scoop:
I know that there is a fair bit of a wee little problem when TC halfshafts and hubs as originally designed come into play. I myself am fighting this issue now. Strangely, though, I've come into a rather interesting job, that being engineer at a company that makes Friction Welders!
If you are not familiar with the process of friction welding, the simplest case is rotary inertia friction welding- where two pieces are placed in a lathe-looking-like contraption. One is spun up to speed on a spindle that has many large flywheels attached. The spindle is then pushed forward until part contact and then a measured dose of pressure is applied. The rubbing of the two parts against each other causes a great deal of heat to be generated at the welding interface, and suddenly! The two parts in question become one. Unlike normal kinds of welding, this joint has a very distinct advantage, weld "penetration" is very deep, and the weld surface exists not just at the edge plus penetration, but over the entire contact area between two pieces.
Anywhoozle.
I have seen first-hand what these mean machines can do. They can produce forged quality joints into things with unusual geometries. They hold concentricity very well by nature. Given that our hubs are naturally cyndrillical, and the halfshafts are as well, there is limited doubt in my mind at least about the possibility of this. Also, there are a number of advantages if this works which I can think of off the top of my head.
1- Halfshaft will NEVER disconnect from hub. - No weeble wobbling, no looseness. Friction welding is the same process used to join up auto driveshafts, piston rods on heavy equipment, and jet engines.
2- Hubs less expensive to machine - No more need of central splined hole through hub, or tapered hole through hub eliminates valuable machine time. Similarly, halfshaft piece would only need one splined component to it
3- Length of halfshaft extending from hub can be very tightly controlled as a tolerance and, ref #1 - will not change, ever!
4- Assuredly, during hub removal, halfshaft will come out with hub
5- Hub design already favorable to friction welding process - The TC hub is "almost" perfect for this to happen. It has a recess built in which gives generous clearance around the wheel bearing nut. In order to make this more practical, said hole might need to be made a bit deeper, however narrower, though I'm not entirely sure, there might be enough clearance anyhow. This will be checked. The hub is also small in diameter, and could be fitted right into a spindle of one of these machines at least by size. Whether or not better tooling will need to be made to ensure the threads and splines on the outside of the hub need be protected has to be evaluated.
Long story short, I desire some used, unwanted, damaged TC hubs to do some experiments on, especially to see if making or adapting tooling for this is plausible and feasible. If it falls on its face, then the resulting prospects are some time, and a few unusable hubs and halfshafts will be toasted up in the experimentation. If it does work, then there might be a considerable future cost savings and reliability improvement I have to offer the lot of TC owners, and perhaps perhaps other cars as well.
So, if you are changing out your rear hubs, or making some new ones and screw up on the machining somehow please think on this and get in contact with me. The more inexpensive TC hubs I have to burn through without shame, the more chance I have of getting the process right.
-kam-
Here's the scoop:
I know that there is a fair bit of a wee little problem when TC halfshafts and hubs as originally designed come into play. I myself am fighting this issue now. Strangely, though, I've come into a rather interesting job, that being engineer at a company that makes Friction Welders!
If you are not familiar with the process of friction welding, the simplest case is rotary inertia friction welding- where two pieces are placed in a lathe-looking-like contraption. One is spun up to speed on a spindle that has many large flywheels attached. The spindle is then pushed forward until part contact and then a measured dose of pressure is applied. The rubbing of the two parts against each other causes a great deal of heat to be generated at the welding interface, and suddenly! The two parts in question become one. Unlike normal kinds of welding, this joint has a very distinct advantage, weld "penetration" is very deep, and the weld surface exists not just at the edge plus penetration, but over the entire contact area between two pieces.
Anywhoozle.
I have seen first-hand what these mean machines can do. They can produce forged quality joints into things with unusual geometries. They hold concentricity very well by nature. Given that our hubs are naturally cyndrillical, and the halfshafts are as well, there is limited doubt in my mind at least about the possibility of this. Also, there are a number of advantages if this works which I can think of off the top of my head.
1- Halfshaft will NEVER disconnect from hub. - No weeble wobbling, no looseness. Friction welding is the same process used to join up auto driveshafts, piston rods on heavy equipment, and jet engines.
2- Hubs less expensive to machine - No more need of central splined hole through hub, or tapered hole through hub eliminates valuable machine time. Similarly, halfshaft piece would only need one splined component to it
3- Length of halfshaft extending from hub can be very tightly controlled as a tolerance and, ref #1 - will not change, ever!
4- Assuredly, during hub removal, halfshaft will come out with hub
5- Hub design already favorable to friction welding process - The TC hub is "almost" perfect for this to happen. It has a recess built in which gives generous clearance around the wheel bearing nut. In order to make this more practical, said hole might need to be made a bit deeper, however narrower, though I'm not entirely sure, there might be enough clearance anyhow. This will be checked. The hub is also small in diameter, and could be fitted right into a spindle of one of these machines at least by size. Whether or not better tooling will need to be made to ensure the threads and splines on the outside of the hub need be protected has to be evaluated.
Long story short, I desire some used, unwanted, damaged TC hubs to do some experiments on, especially to see if making or adapting tooling for this is plausible and feasible. If it falls on its face, then the resulting prospects are some time, and a few unusable hubs and halfshafts will be toasted up in the experimentation. If it does work, then there might be a considerable future cost savings and reliability improvement I have to offer the lot of TC owners, and perhaps perhaps other cars as well.
So, if you are changing out your rear hubs, or making some new ones and screw up on the machining somehow please think on this and get in contact with me. The more inexpensive TC hubs I have to burn through without shame, the more chance I have of getting the process right.
-kam-
