9/20/13 I had mentioned some suspension changes based on the experience we've gained with Pete's car. The gist of it is that the bearings seem to be developing play rather quickly, some even have it brand new. We did quite a few bearing swaps and eventually tracked it down to the fact that a particular brand (supposedly premium OEM one) is susceptible to play. Very surprising, especially since their bearings in our other uprights designs have been just fine, but there it is. While simply switching brands would address the issue, in the process of swapping out bearings I was reminded that this is not exactly a user friendly task. Looking at it from the customer's perspective, having to be careful about bearing brand and the considerable hassle and need for specialized equipment in swapping, makes the design somewhat less than ideal. I therefore decided to bite the bullet and redesign the uprights - a bit more effort and expense now (all the lead customers get replacement parts free of charge) but a lot less potential for problems down the line.
The new design, code named GTX, uses a cartridge bearing/hub unit which is preloaded at the time of manufacture and doesn't depend on the axle nut torque to hold it together. Replacement involves just undoing three bolts and the axle nut, and can be accomplished without removing the upright from the car. This is compared to removing the upright (taking apart balljoints in the process), pressing the drive flange out of the bearing, pressing the bearing out, then heat-shrinking a new one in, pressing the drive flange back in and reinstalling the whole thing. Also axle nut torque is now 105 lb-ft instead of 250+. And the upright is stiffer to boot. All this of course doesn't come without a downside and in this case the penalty is 2 lbs per corner. But, all in all, it is the right way to go. Below are pictures of the original GTS (black) and the new GTX (silver). Looking at the pictures I realized that the camera lens makes the GTX seem smaller vertically - it isn't. The uprights are identical in the vertical dimension and the GTX is considerably wider horizontally (the last picture gives the best comparison).
The new uprights will go on Pete's car next week and he'll test them at Laguna the week after. Whenever we are comfortable with the new design the other three D2s out there will get updated.
Speaking of lead customer updates, Pete's car just got a new set of pedals, now that we've successfully tested them. We've learned that what works best is having friction material on brake and clutch pedal faces but not on the throttle so that's the standard setup now.
Another thing learned from Pete's D2 is that consumables are consumed at a very modest rate. It's looking like tires are good for 16+ events, brake pads for 8+ and rotors for 16+. And this is not just coasting around, the D2 is the fastest car at pretty much every event it shows up at. We did discover some cracking on one brake rotor after the 17th track outing. This compares favorably to just 6 trackays that I could get out of the Mini on a set of rotors, or 8 in the Elise. Also, the cracking may have to do with all the brake testing (bias and pads) that Pete has been doing. The actual wear is not too bad and with less abuse they'll most likely go longer. The other 3 are OK.
Currently it's looking like around $150 per track day in consumables (tires, brake rotors and pads). This is not as low as the featherweight D4 but much better than any production car I've run. For comparison the Mini was around $600 per event, once I got up to fully utilizing it, and it was MUCH slower at 1:34 around PIR vs D2's 1:22.
Progress is made every day. I'll have an update on the bodywork before too long. In the meantime, the CNC router is now set up and ready to try cutting some foam. Fenders and a few other bits are going to be the test pieces.
The last bit of news - we now have 4 new D2 orders and strong interest from at least three other potential customers. Seems the word is getting out :) Right now the next available delivery slot is mid March. If you want a D2 in time for next track season, think fast!
9/26/13 A few more things to announce. First, we've sold another D2 - chassis #9. The next available is #10 with target delivery at the end of March, 2014.
Another item is that the plug prep is fially done and it turned out very nice. It's been dropped off at M&W Fiberglass where the molds and the actual parts will be made.
There will be access panels on the nose and tail which will be created as part of making the molds. To this end we had to figure out what size/shape the panels should be. The goal is to be able to at least transport two helmets to the track with a passenger in the right seat, so we figured out two locations - one in the nose and one under the passenger side of the dash.
The nose panel will be big enough to fit a helmet through. The exact method of securing a helmet on the passenger side will be worked out later but I'm thinking something along the lines of a bungee net. You can also see how much the seats enclose the occupants - that's 1/8" thick aluminum. There is 4" of space between the side tubing (1.5" x 0.095" chromoly) and the seat, so there's some room for it to deform in case of a side impact.
The seats themselves are being redesigned based on what we've learned in testing with Pete's car, for better comfort, better support and more room (yes it's possible to improve all 3). Naturally the early cars will get upgraded to the new spec. As with the uprights, it's emotionally dfficult to discard seemingly good parts which cost good money and effort to make, but it's all part of the development process. I have to make sure that the cars we put out are the best that we know how to build and my future designs will be all the more efficient thanks to everything that's being learned now.
On a different subject, I've been asked what class the D2 would race in. After some research it looks like it would be eligible for ASR in SCCA (with some additional bodywork that will be optional) and in NASA Super Unlimited. It should also qualify for Pikes Peak Open class, I'm going to start that conversation shortly.
10/01/13 Well, the new uprights are back from anodize and on Pete's car (we discovered that even for this design not all bearings are the same - sigh). He's now off to Laguna to continue testing.
I rather like the look of clear anodize so I'm thinking that's what we'll do for a while on the parts we make and see how that works out.
Speaking of making parts, I've had to redo the seatbelt attachment solution a couple times and I think the newest design will work pretty well. The challenge has been to provide the right height (and some height adjustability), sufficient strength and package it all in the compact dimensions available. The new solution consists of a 1/4" steel backing plate that goes behind the chromoly frame tubes and a 1/2" billet aluminum bracket to which the belts actually attach.
While it may look like the bracket mounts to the sheetmetal firewall, it actually mounts to the steel backing plate via welded-in standoffs. The bolts just pass through the firewall but it's not a load-bearing connection. Rough FEA analysis shows the design is good for at least 2,000 lbs per belt attachment point which for a 200 lb driver is the equivalent of stopping from 80mph in less than 10 feet (roughly 40g; the FIA spec is 32g). I will run a more detailed simulation later.
10/04/2013 Pete is continuing to fulfill his role as test pilot for track days number 18 and 19 for his car, at Laguna this time. There are worse jobs. We did learn that when wiring instructions say 'high impedance device only' they probably mean it. I had all kinds of hollywood images in my head when I was telling Pete to clip the orange wire that connects to the purple wire, via cellphone, to make his car run again. Geeks like ourselves will appreciate this, normal folk just take our word for it - it's cool in a frustrating kind of way. I now own an extra throttle pedal sensor.
In other news, we've had another visit and now chassis #10 is spoken for. Part of it was checking out the progress on the bodywork molds and indeed there is a bit of that.
There is a fair bit of art to the science of mold making. I'm looking forward to seeing the result, as I know are a number of others. This is really starting to get interesting :)
10/16/13 There is progress on many fronts. The bodywork molds are coming along:
There are other things which I don't have pictures of at the moment - the production version of the dash hardware is here, the first one is installed on Pete's car (still needs some tweaking and configuration but working well overall). There will be a separate post on that later. The updated interior panel design is done and the first set is due in a couple of days. Same for fender mounts and a number of other parts. The work never ends it seems :)
The next couple days are another test outing at ORP. Hoping to take some pictures and better video this time out.
10/17-10/18/13 The track season is winding down rapidly so we decided to take advantage of the unusually pleasant weather and go out for more testing at ORP. On the agenda - see how the new seatbelt mounts feel at speed on track, put more track miles on the new uprights, and even try to have some fun with all the work we've been doing lately :)
We have now outgrown our trailering setup - the 20' trailer can take two of our smaller cars (D1/D4) but only one D2. So for next season I'm starting to look at various options. We now know that a big rig like the Mothership is too much hassle (storage, maintenance and generally getting in and out of places). The van we have now is great and we'll probably keep that. I'm thinking a 28' trailer will take a pair of D2s or 3 D4s and still be within its 7,500 lb towing capacity, if we add a weight distributing hitch. So that's the tentative plan. In the meantime to bring a D2 and a D4 out we had to borrow my old open trailer from Satya and have Tristan tow it with his Raider (Pete has his own trailer for his D2). Another advantage of light cars - this setup actually worked reasonably well.
Arriving in the morning we're greeted with surprisingly perfect weather - I think these turned out to be the most comfortable two days weather-wise all year. Perfect visibility too, with several volcanos poking up sharply above the horizon.
So, on the testing results - the belt setup fits and feels great, much better than the previous arrangement. The height at which the shoulder belt anchor points are mounted really does make a difference it turns out. Belt arrangement affects how well connected the driver feels to the car and, consequently, his confidence in driving it.
I was hoping to be able to test new seats as well but the vendor delivered panels without bending them so we had to send them back to be finished. Hopefully the weather will hold out long enough for us to do that later in the month. It's taking a few iterations but now the ergos and interior (as well as other parts) are really starting to come together.
The new uprights are working very well - while the old design on Adam's car has already started developing play in one of the bearings, the new ones on Pete's are still perfectly solid. Good confirmation that the effort to redesign the parts was well spent. We'll be making a big batch soon, to replace all existing parts and for the new cars as well.
We did discover a few things that still need to be upgraded and revised, that's what testing is all about. Again all the early cars will get the tweaks. Pete's car, now with 22 hard trackdays on it and over a dozen different people having driven it, has been a great development platform. There is no way we could have gotten this much testing done on our own while still continuing to design and build parts and cars, so again a big THANK YOU to Pete for being a key part of the development process.
Being out here for two days gives us a chance to relax a bit and have some fun too. We did a few sessions in the D4. I've literally lost track of how many events the car has on it now (well over 30) and it's held up very well. The engine does feel like it could use a valve adjustment and we know compression is down a bit on one cylinder. Winter project.
Jay just started riding motorcycles this spring and already has over 10K street miles on his bike. He's getting pretty decent on track too...
We didn't bring M's bike this time but hopefully will do so before the year is totally done. I was able to ride it on track for a session a month or so ago and it felt great. Need to do more of that. Going between four wheels and two on the same track, same day, is very educational and provides new perspectives on both.
Adam and Pete had a lot of fun with their cars, as always, and we had one of the new owners who just ordered a car come out and drive, as well as a prospective customer.
I'm really eager to see the D2s with bodywork on (I know I'm not alone in that! ;). Hoping to still get a fully dressed D2 out to the track this year.
In the evening there's not much happening in Grass Valley but M managed to find a great restaurant not too far away in Goldendale - the Glass Onion. Excellent food and exceeding all expectations we had of a place this far from anywhere. Nice selection of local wines, too.
On the second day we also had a very cool car join us - the Mach 40 created by Eckert's Rod and Custom. The craftsmanship is very impressive and even more so given the fact the car actually works, and quite well. Dave says he doesn't build trailer queens, he builds drivers and this car clearly backs that up. Check out the design details and build pictures on their site. It's a very different type of car than what we build with different priorities in design and construction. Always cool to see a well thought-out, well executed machine.
All in all, a great couple of days. Much was learned as always, much fun was had and now much work awaits back at the shop. As a fitting conclusion to the trip we were treated to a spectacular moonrize on the way home. As far as experiences go, this trip has been a good one.
10/29/13 The weather is now getting marginal but the forecast for today looked promising, so we scheduled the day for Alex to come out and drive his car on track for the first time. His original plan was to wait until the bodywork is done but this was probably the last chance this year weather-wise. The air and track were cold, about 40 degrees F, as we unloaded but the sky was clear with no wind.
The day before the first set of the new interior panels came in. Tristan welded them together and installed just in time for this outing. We didn't have a chance to cover the dash so the reflections off the aluminum were a bit bright at times, but not an issue in general. The standard interior will be all black to minimize glare, with some removable padding that could be done in an accent color.
This car previously only moved about 20 feet under power when we loaded it into the trailer, so this would be a true shakedown working up to speed slowly. As part of our final prep we removed the stickers from the tires and Alex headed out on track. A quick check afte two laps and he's back out for a full 35 minutes. From the tower I could see he's having fun! :)
There is a very fine layer of dust on the track surface and the car picks up a bit of a cloud as it goes by - you can see it in the picture above, next to right rear tire. It's a cool effect. With no wind it's very quiet and you can actually hear the D2 around almost all of the track. Normally its subdued exhaust sound disappears except on the front straight.
After a break Alex heads out for another session, this time staying out for a full 40 minutes and starting to work up to speed. He's feeling more confident with the car and the track and ends up with a best of 154.9 which is really good for an initial shakedown. After the session the car checks out fine - no leaks, no issues. The driver is pretty tired though after nearly 1.5 hours on track and has a long drive south ahead so we decide to call it a day.
Before we got the D2 back in the trailer I did get a couple quick laps just to test the seats for myself and they work much better than the first version. I'm pleased.
Back at the shop much work awaits. The bodywork molds are almost done and I'm eagerly awaiting the completed parts. In the meantime the next batch of seat panels will be ordered so that we can update all the existing cars.
11/06/13 One of the things I"ve been working on is dual-rate bellcranks. The idea is to have a 'track' setting and a 'street' setting, the latter being about 30% softer and slightly higher rideheight, which an owner could change between in minutes. An additional advantage of changing this with bellcranks is that damping stays matched to the springs - both the effective spring rate and damping rate change together. The picture below illustrates the concept. Left side is 'track', right side is 'street'.
We're in the process of building a set, hopefully Pete will get to test them out in a little over a week, along with his new Penske shocks.
Other things: The molds are almost done. It's taking a bit longer because it was determined that a lot of separate sections are needed for molds to properly release. I think there's 19 molds total.
The new belt mounts got revised belt wrapping method to eliminate 'buckles' protruding.
The revised seats are working well and we're making additional sets for all the existing cars. You can see in the comparison to the first rev that the seats are roomier - but they also happen to offer much better support!
On the subject of the interior, I've added panels to finish out the area around driver's and passenger's legs. This both makes it look tidier and provides significant additional protection.
All of these panels will get powdercoated flat black which will be the base finish. Upholstery will be optional.
The new uprights are being machined for the existing cars and a batch for the new cars is also in the queue.
And finally, the tubing kits for the next 6 chassis are here. Welding will start next week, when the main tubes show up from another vendor.
11/13/13 New this week - Pete's car got the new generation interior, Penskes and dual-rate bellcranks. Now he's off to Thunderhill to test all that Friday and Saturday.
The molds are done, now they get steel outer frames and a post-cure. Then the first body finally gets made.
The bent chasiss tubes are here, the fixture is on the table and welding has started on chassis #5.
While all that is going on we are also moving forward on the Stiletto (more on it soon), and have completed a few sets of uprights for Altra (they'll also be available for sale separately for those building their own cars, $1,750 per pair front or rear, or $3,000 for a full set of 4).
These use Porsche 911 bearings and high strength hubs. A number of brake packages are available as well. E-mail me for more info.
11/22/13 Pete had a great two days at Thunderhill (track days 23 and 24 for his car) and the verdict is that the new seats are a success. Combined with Adam's earlier feedback and my own experience, I'm pleased.
This weekend we have some visitors and very good discussions which will lead to some pretty cool announcements soon :) The momentum is gathering...
In the meantime, there's steady progress at the shop. The CNC machines are running churning out parts - brake brackets recently, brake hats at the moment.
The #5 chassis is taking shape in the jig as well.