Targa Miata
April 12, 2013 - I found the cause of the axle failure.
The spring clip on the end of the shaft broke, allowing the shaft to pull most of the way out of the CV. The small number of splines remaining just weren't up to the task and ripped apart.
On the other side, one of the CV boots ripped and was slinging grease, but I haven't taken it apart to find out just what's going one. It wasn't ripped last time I was under the car and since it was slinging grease on to the exhaust, I would have been able to smell it if it had been happening for a while. I'm curious as to what I'll find in there.
No matter, I've got a new set of halfshafts in the car now. Not a cheap fix, but an easy one. I did check to make sure I wasn't exceeding the amount of allowable change in length of the shafts due to excessive travel, but it looks as if I'm dead on the correct amount.
entry 1079 - tags: failure, axles
April 29, 2013 - Time for the big Laguna Seca event.
It was not easy getting here. It turns out that my new axles did not have proper heat treatment, so they failed almost immediately. I decided to upgrade to the stronger G2 setup partly because that's what was on the shelf at Flyin' Miata, and I ran into a series of problems with the new parts. Finally, after working most of the day before I left, I ended up with the used parts from Elvis on the car - rear uprights (including hubs), rear upper control arm and axles. Finally, after all that work, the car was ready for the trailer. Then the long tow began.
Finally, we got to Laguna Seca. My first lap was uneventful, then an alignment cam slipped. Argh. Still, the car felt strong. I went out again and on my second lap, the clutch hydraulics failed. Argh.
Much prodding and poking at the clutch ensued. I got it back again briefly, then it went away. I thought it was a bad clutch master or slave. After working on it all day Saturday, I called Bill Cardell that night and he suggested there might be some debris in the hole between the clutch reservoir and the master. I worked on this the Sunday morning and had a clutch within half an hour! I took it out for some exploratory laps and it was coming and going. I seemed to have about three shifts in rapid succession, then it would go away - which made the front straight and the braking into turn 2 fairly interesting. A bit more bleeding and it came back 100%. Time to go drive.
This car is a beast. I'm certainly not the fastest driver on the track at an event like this, but the car is a great equalizer. With the big engine, I could pass just about anyone as we climbed the big hill up to the Corkscrew. The aero seemed to be working nicely, as the car remained well balanced in the high speed turns as well as the slow ones. I was having a fantastic time working my way through the pack.
Janel finally got a few laps in it after the disappointment of last year and the non-functional Saturday. Her biggest adjustment was to the braking points - the car builds up speed so quickly that you have to brake a lot earlier for the turns. She was starting to get more comfortable, though, and looking forward to her last couple of sessions.
entry 1082 - tags: testing, axles, failure
April 29, 2013 - This is not something you want to see out the windshield.
That's my rear brake rotor. I came down the Corkscrew, hit 4th gear and turned into the fast turn 9. Just before I reached the apex, I heard a bang and the car snapped into a spin at somewhere around 80 mph. My first clue as to what had happened was seeing my right rear wheel rolling along the pavement as we rotated the first time, then we went into the dirt after the second spin. On the dirt, the car lifted a little bit like it was trying to roll, but stayed happy side up as we scrubbed off speed.
A big thumbs up to the track designers - we finished our ride safe and sound without hitting anything but a small drainage ditch. Then it was just a matter of sitting in the car with our helmets on and watching the other cars come around the corner, seemingly aimed directly at us. Finally, all the traffic was cleared and the flatbed showed up.
entry 1083 - tags: crash, failure, laguna seca
April 29, 2013 - So, what caused the accident?
Looks as if the rear hub failed, leaving only the brake rotor to hold the wheel in place. Obviously, that's not what it's designed to do so it simply ripped apart. This was an upgraded but used rear hub - taken from Elvis, remember - but I'm going to be taking a very close look at the bearing and specifications to see if it's possible to build something stronger.
This also reinforces my belief that I need to step up my maintenance. Talking to Emilio at 949Racing about his enduro experience, I'm learning more about the difference between a track day car and a racer. Yes, I only use this car for track days but it's highly stressed and those track days stack up. I'll start flushing and cleaning all the hydraulics on a regular schedule instead of just the brakes. Wheel bearings are going to start getting treated like consumables. Although I'm not sure I would have identified this one as a problem, as I had it off the car on Wednesday and it felt fine. The hub's previous history was as a street car that has seen a few track days, but at a much lower stress level than the Targa Miata runs.
entry 1084 - tags: failure, hub
April 29, 2013 - This is the least amount of damage you can do if you lose a wheel in Turn 9 at Laguna Seca.
The bumper is just out of place. The exhaust got pulled out of shape and took some of the brackets on the body with it so the trunk floor is probably messed up. The skid plate under the diff is deformed and I want to check the subframe carefully. The front wheel is dented and the rear is all scarred up. But it's almost all bolt-on parts. There's one small dent in front of the missing wheel but otherwise is looks like the tub is untouched. Amazing. I got very, very lucky.
The car's back in the trailer (thanks to the help of Emilio and a number of other onlookers) and heading home to Colorado. I'll drag it out there and take a close look at everything underneath.
entry 1085 - tags: failure, crash, laguna seca
May 1, 2013 - So, what caused the accident?
The hub came apart, leaving only the brake rotor to hold the wheel on. Of course, that ripped apart almost instantly and the car snapped into a spin.
It turns out that this was a known problem with the V8Roadsters hubs, which led to a redesign several years ago. The new one is 1/2" thick instead of the 3/8" found in the older design. In the fallout from my broken axle last month and some problems found with new parts, I ended up borrowing the hubs from FM's shop car, Elvis. For some reason, Elvis never got the upgraded parts. I'm going to try to figure out how that fell through the cracks. We're also going to contact all of Flyin' Miata's V8 customers and ask them to check their rear hub thickness to make sure there aren't any more out there.
The good news is that we now have proof that the rear caliper brackets on the new FM brake setup are stronger than the rotors!
entry 1087 - tags: failure, hubs