4 Mar 2008

After thinking it over and hearing from readers I’ve decided to stick with Miata rear uprights. As several people pointed out, I’m supposed to be designing an easy-to-build, simple car, not something where all sorts of different donor parts are needed and custom parts fabricated. Okay, lesson learned.

Speaking of features on the car, I have a reader question: Do you want push-rod suspension or traditional outboard suspension? Push-rod suspension: looks sexy, good stock travel. Cons: heavier, more complicated, takes up space inside the chassis, takes longer to build, more expensive. Outboard suspension: simple to build, easy, cheap. Cons: not great shock travel. Your choice, pick your poison!

My brother just started driving his Super Stalker, even though it’s not complete (hood’s not painted, no fenders or mirrors, etc). He said, “First gear is useless… second gear is useless, third gear is, oh crap!” I guess he’s impressed.

3 Mar 2008

Forgot to mention that I took Kimini up to the “Cars and Coffee” event. This has turned into a huge deal, with hundreds of cars and spectators. Nearly everyone’s there by 7am and gone by 9am(!) which is cool because it leaves you with practically the entire day for other things. As cars start leaving, a crowd gathers at the exit, cameras in hand, to watch and listen as some exotic machinery leaves. In fact, there was a Ferrari 250GT there, or something that was so close to an original it had people all excited. Anyhow, I don’t post pictures any more because there are 100s of people who do so now. All you have to do is Google “Car and Coffee 3/1/08”.

In other news, I’m closing in on the front wheel geometry. Because I’m making the front track wider than the usual Locost, it presents the opportunity to use an unmodified Miata steering rack. People have a lot of trepidation about modifying steering racks, so this both simplifies and speeds up construction. Moving links around and juggling the wheelbase made it all work out, so unless something nasty shows up, this iteration looks promising.

The second set of rear uprights arrived, setting a new record in poor packing. Styrofoam peanuts don’t protect 40lbs suspension parts, so they punched a hole in the box, which arrived half empty of peanuts, I’m sure UPS appreciated that. I’d be upset if they were broken, but thankfully suspension uprights are darn tough. So, portions of these may be used instead of the Miata rear uprights. As much as I look at the Miata parts I just can’t figure out how to make a clean, easily adjustable rear suspension with them. While the alternative design requires fabricating custom uprights, the bolt-on spindles don’t require making precision bearing cups. (This adheres to my goal of making the car producible without requiring a lathe.) I’m curious what people think though, about making suspension uprights if it is an improvement over using the stock Mazda parts. Of course the question becomes, “How much better would it be? Is it worth the extra work?” I hope to answer that soon. It’s the eternal compromise, do I use parts which are just “okay”, or require extra work to make it much better? It’s a thin line between doing it right and getting it done.

2 Mar 2008

Been working hard on the front suspension design which is testing my nerves – just like 12 years ago. Since I’m using Mazda Miata front uprights, I wondered what kind of numbers Mazda used. The internet revealed the stock suspension points, and even if they aren’t exact, the Miata’s setup is very interesting! What I find fascinating is how Mazda doesn’t follow the commonly held notion about keeping the roll-center stationary, not even close. But if it’s examined using force application points, figuring that the outboard tire carries most of the load, then it works. Of course, the reality is that it (the car) works just fine, as Miata owners will attest. So it’s very interesting how Mazda’s setup violates the so-called stationary roll-center rule… very interesting indeed. So, good, this means I press on with my suspension design and hopefully have some good numbers this week. Once the front suspension is done I can start working my way aft.