Wednesday, April 4, 2007

All Bearings Fail

Recently, I was presenting to a venture capital firm and got asked about the maintenance features of our turbine platform. It was a fair question, and one that I didn't answer very well. We do have some significant features in maintenance/durability/simplicity, and I did cover some of the blade resiliency characteristics. Where I got into trouble was around the determination in which one of the VCs believed that "all bearings fail." On the notion of bearings and mean time between failures (MTBF) the conversation went something like this:

VC: What will you do when the bearings fail?

Jeremy: Talks about loads being center-balanced, talk about 180 RPMs as our max, talks about the six-bladed design giving continious, smoothed and non-sinusoidal power pulses to the system...

VC: All bearings fail. When your bearings fail, this is going to rip out of the rooftop when it comes falling over...

Jeremy: Dumbfounded and deer in headlights reaction...

In hindsight, I could have also talked about the expected 15-18 years of mean time to failure ratings on our bearing sets (our bearing sets are rated for 200-300 million RPMs under designed loads)... But of course, I had to go look that up later with the technical team. I also found out that we can promote that there are no flexing or moving parts in the Wind-Sail alternator, and the magnets move past fixed coils. So other than age effects on materials, or thermal problems from overload, the alternator should never wear out. I could have also talked about wind loading on the system, and that frozen bearings present nearly the same load as the system is under braking scenarios (e.g. we don't model our loads so that we are dependent on spinning as a way to prevent being torn away from the roof.)

A couple of closing comments:

1. One of the challenges that I actually enjoy about presenting to VCs is that there are countless holes/traps that you can fall in, and you can never predict which ones are coming. It's mental surfing and it's invigorating learning how to stand on that board. In time, maybe I can ride some of the bigger waves.

2. I can also add "all bearings fail" to my growing list of dispassionate VC beliefs that I need to learn how to avoid falling into, other traps have included: 'distributed grid power won't work', and 'farmers don't care about bird kills- they kill birds for a living', and lastly 'unless you get under $1 a watt, this won't ever be viable.'