10/21/16 Yep, we're still juggling more than a half-dozen projects (Stiletto, D2, D4, D47, Drakan, D1, custom parts, etc.). So progress on any one of them is slow but overall there's a lot that's getting done. On the D2 side, we're pushing forward on the bodywork. Since everything is connected to everything else, this involves the chassis, molds, aero, cooling, HVAC, interior, suspension and electrical.
First, on the aero. I've been evaluating the worth of side 'tunnels' on this chassis layout (relatively low impact on time since I can just set up the CFD run last thing at night and have results in the morning). We need some means of connecting the bodywork to the chassis, and if the connecting part had the shape of a tunnel then it might have some other benefits. Turns out that it does - about 60 lbs more downforce at 100 mph, a forward aero balance shift (which is good), and about 40 lbs reduction in drag at the same speed. Percentage-wise it's significant since we're looking at ~250 lbs downforce and ~300 lbs drag. Why are the numbers so low when you see people on the interwebs claiming 1,500 lbs downforce from just a small wing? I've talked about it before but let me illustrate just one aspect of it (there are many).
As I've mentioned in the past, careful setup and correlation with real life are essential for meaningful CFD. But even if you have that, accuracy is not guaranteed. Below are pictures of one test run after two iterations. It looks neat, all clean and tidy, and claims about 1,200 lbs downforce with 350 lbs of drag.
Sounds pretty cool, right? We got pretty pictures, we got sexy numbers, might as well call it a day. But from running correlation before and other factors, about 300 iterations are really necessary to get accurate results. When they are completed, things look like this:
The final numbers are 280 lbs downforce and 260 lbs drag. Same setup, only difference is that I allowed the computer the time (10 hours or so) to fully consider the problem. Like in anything, if it looks too good to be true it probably is and one is well advised to dig deeper.
Now on to the physical parts - the canopy mold is complete, the upper door skin plug has been dropped off for molds, we're updating panel interfaces and contemplating how many more molds it's going to take, the three frames in process are getting the latest updates, front suspension arms got shortened by 1" to better fit the bodywork, and there are a couple dozen things too small to mention here yet each is a project that requires time, effort and resources. That's just what it takes.
Don't know if anyone spotted the extra 'Pikes Peak' bars in the last two pictures, but there's a reason they're there.... And yes two short tubes are all the chassis mods required to our standard D2 to meet the stringent PPIHC safety regulations.
11/28/16 Found and fixed a grounding problem on the gear position sensor, and made some tweaks to the control software, so it's time for another test. Weather has turned decidedly winter-like, with solid rain in Portland and cold + wind out at ORP. Rain and snow were forecast too but that changed so we decided to go for it. 35-40F and 10-20mph wind is what we got, which is OK.
Loading the car in the trailer is always a bit of a challenge - in the design phase I measured a few trailers, open and enclosed, and found that 82" between fenders is typical. So the car is 80" wide. Takes a bit of precision getting it in. Helps to have a spotter, but can be done solo too.
Yep, 1" clearance on each side, +/- 1/2". Clearance is clearance.
Neil came out as well with his D1, to test all the recent changes we've made to it. More on that separately. A couple others joined as well to see what Palatov trackdays are all about.
I recruited Neil to be the test/demo driver in the D2, with Pete's blessing (since Pete owns the car). On test days I prefer not to do the driving myself. This way I can focus on being the engineer/event manager and someone else can focus on the driving and giving me unbiased feedback. Works well.
First outing showed the shifter to be much improved from before the grounding fix but still a bit jerky. Here's a video of that. Yes the camera placement is not ideal, but this is testing not beauty shots - those will come later :) Based on Neil's feedback I changed some parameters and sent him out again, with a different passenger. A little too much in the other direction, resulting in some missed shifts. Video here. This is much needed data, so the final tweak for the day (combined with a third demo ride) resulted in a big improvement, as can be seen here. Upshifts are now pretty seamless. Downshifts can be also, when charging hard, but get jerkier as you ease off the pace. This is a limitation of the current system and something we aim to fix sooner rather than later.
I did go out for a few laps, tweaking downshift blipper settings at various pace levels. Doesn't make for fast lap times (I was circulating the track some 25 seconds slower than Neil), but it does gather more data. And that's what this is all about.
And I did get a few pictures of the car. Will be even cooler when we get the canopy done (it's getting there).
Graham, who put together an earlier video on our trackdays, came out as well and did a bit of both filming and driving. This is a start of a project that should be pretty cool - more on that as it comes together.
12/8/16 Figuring out details of how the new bodywork is going to come together is proving harder than anticipated. I've gone through countless iterations, tried and discarded numerous alternatives. We've discussed possible mold changes with our vendors but didn't settle on anything that was clearly the way to go.
I'm now really appreciating how great it is to have just a one-piece body shell on the D1 and D4. One mold, no interfaces, no seams, no tolerance issues. Of course their diminutive size is what makes it practical - doing a one-piece body on a car the size of the D2 would make it very cumbersome, and of course doors and other access panels have to be dealt with regardless.
There are numerous challenges, some having to do with serviceability/access, others with panel interfaces, aero and ingress/egress. One example: the nose piece. It was originally intended to be removable or tiltable as one piece, but once we made it and installed it, the reality quickly became apparent - some kind of 'hatch' acces into the nose is necessary while majority of the front bodywork stays fixed. Several solutions were considered and we ultimately settled on making a separate 'hood' that overlays the existing part, and cutting access openings in the latter.
Valerie as our current intern got the job of gluing 1/4" foam to the original nose pattern, and then shaping and prepping it for molding, so that we can make an additional mold for the new plug from basically the same tool.
This will ensure that the new piece fits precisely with the existing one, and is exactly why we keep old patterns around instead of scrapping them.
Another challenge is doors. There are many sub-tasks there, but first and most important is the hinges. Figuring out exactly how the doors are going to pivot and latch, while making sure they align precisely and clear all other bodywork throughout the range of motion, is a daunting task. I'm struggling with a similar challenge on the Stiletto, in fact, although that setup is more conventional.
Below are illustrations of the previous approach (Countach-style scissor pivot) and the one I'm now leaning towards, LMP style two-point 'flip' pivot with external hinges (would need to make cool billet parts to have it be presentable).
Both mechanisms fit my requirement of being able to open the doors inside an enclosed trailer.
The scissor approach has a couple advantages - the hinge is hidden and the same setup can work for roadster and coupe. The disadvantages are weight, difficulty in alignment, and the fact that high-speed lift is likely to pull up the tops of the doors unless I figure out some kind of multi-latch setup. All surmountable, but lots of work. I haven't entirely discarded this yet.
The 'flip' arrangement is lighter, offers better alignment, and provides a designed-in hold down for the top portion of the door. However it only works for the coupe, which is not necesarily a problem - most cars will be coupes, and roadsters, already having no windshield and therefore being pretty extreme to begin with, can just have fixed doors. The issue of external hinges is a trickier one but I think I can figure out billet pieces that will look and work nicely. Both McLaren P1 and La Ferrari have the 'flip' style doors. Fortunately I know someone who has one of each, so I dug up a couple pix I took of his cars. A good reference point.
Either way I need to figure this out soon, as there are many other pressing things to deal with.
12/18/16 Progress continues on D2. The primary focus is still the new bodywork, but there are countless things that this implies. New interior, HVAC, doors, crush structures/wing mounts, accessibility/serviceability, and so on.
On the serviceability front, the work on the revised front hood mold is coming along. The foam and first few layers of bondo are done, and the first coat of primer is applied. Valerie, our customer/intern, has been doing a great job. It is 95% her effort.
Still a fair bit of work remains but it's going well.
Another item is the new crush structures. They have a challenging multitude of roles - be strong enough in tension and vertically to provide tie down, jacking and towing points, yet still be collapsible in compression to absorb impact energy.
Oh, and they provide wing mounts at both ends, too. So far so good.
Other items of progress are on the drivetrain side. We now have the paddle shifter working on the D2RS, but it's only really effective in full-on race mode. This is a limitation of the existing system and so, as it has been with many things, we are now resolved to do our own. Some exciting progress already :)
There are many gearbox options and we are in discussions with vendors to provide a solution that is better than what we've had so far. The challenges are torque, refinement, shift speed, size/packaging, cost, etc. I used to sneer at electronic paddle shift as an artificial aid like ABS or traction control (neither of which I use yet, but the day may come). The reality of massive power and super light weight is that acceleration happens quickly. Very quickly. And you have lots of things to worry about, in a very short period of time, besides shifting. Now that the paddle shift is working I've really come to appreciate the ability to click off shifts 1-2-3 in as much time as it takes to read it, traveling over 100mph when it's done.
One thing enables another, so on the engine side the quest for more power and refinement continues as well. We are now building a twin-turbo LS motor with upwards of 700 hp, and more to come. Should be fun in a 2,000 lb car.
12/31/16 There is so much going on it was hard to choose which blog to update as the last entry of the year. D2 gets the honors, but others will follow soon.
As a point of perspective, the first-ever D2 is back in the shop for some updates. Had to take some pictures of it with the most recent completed car for a comparison of old and new bodywork. They look like completely different cars, including size (with the older car appearing much smaller).
At some point down the line it might be fun to do an updated version of the original body. For the moment though, we have plenty of work to do just getting the new one fully done and sorted, so that's where the focus is.
The mold pattern for the removable front hood is now done and ready for the mold itself to be made. This has been essentially a solo effort by our intern (and D4 customer) Valerie, with only minimal support and guidance from us. To say I'm pleased would be an understatement :)
The new front and rear crush structures provide much needed new functionality that is necessary for the new body - jacking points, tow hooks, tiedown points and wing mounts. And as a bonus, the ability to pull a small trailer. The structures and the wing kit will work on both the old and the new body styles. We're fitting both to another D2 that's getting updates.
One other item that's been requested is jacking points that can be used with jackstands and a 2-post lift, so these are getting fitted as well. The curved lower tubes and the aluminum floor that bolts to them don't normally allow for convenient and secure supporting of the car to access the floor from below. These bits fix that.
This being the holiday season, Tristan couldn't resist using the vinyl cutter to 'dress up' the D2 for the occasion - look closely at the dragon logo :)
Looking forward to everything we will accomplish in the new year. Cheers!
1/17/17 As always we're working on many fronts at once. For the D2, main thing remains the bodywork - we should have first-article test pieces of the canopy and upper door skins shortly. I can then finalize the door hinge design. It does remain a challenge and it's really going to take having the physical parts in hand and moving them through the range of motion, and maybe 3D printing a couple test pieces. The challenge is made greater by the fact that we have two configurations, a coupe and a roadster, which require different but compatible door hinge setups.
Many of the parts being machined currently are for D2s as well, so that's getting done.
One neat item is that we recently got a new workstation with a pair of AMD Radeon Pro WX7100 graphics cards. My previous computer is a few years old and this one is a welcome and much faster upgrade. A good productivity boost - I'll need it with everything on the plate right now. The cool thing is that now I can spin the full D2 model onscreen with RealView enabled, in real time. It's not just bling and does really help with quick visualization.
Works in transparent mode too.
Another challenging D2-related project which gets worked on every now and then is the trailer. What makes it particularly difficult is that the customer who ordered the first one has a very narrow garage opening and has requested a specific width dimension. It is really hard to meet, as you can see in the screen shots below.
Pictured here is the beginning of rev 3 of the design - obviously needs a lot more fleshing out. I do have a plan that I think shoud work, including a mechanism for precisely loading the car on the trailer. Each axle is rated for 2,200 lbs and I expect the complete trailer with D2 on it to weigh around 2,700 lbs - so we have good margin.
As with everything I do, this effort will be leveraged for the updated D1/D4 trailer design as well, for which we have a couple orders too. And naturally everything I've learned from building and operating the existing D4 and D1 trailers has been incorporated into this new architecture. Since there are many high priority projects that are active right now, this one only pops up in the 'rotation' every now and then. Today's working from home on account of crazy weather was a good opportunity to make progress on it.
Site Sponsors and Links:
- CMS Lap Timer - Advanced Track Timer App With Video Integration
Tire Rack - Tires, Wheels (use link when buying wheels/tires to support this site)