04/09/17 This is another one of those situations where I'm too busy to make regular updates. So this one has a lot of stuff in it. First, directly D2 related things:
The D2TT is coming along, and it better - Pikes Peak is only 2.5 months away and there is much to do. So we're doing it. After many revisions and trying to make stock exhaust manifolds work, we've decided to go with custom headers. There is a fair bit of room for the turbos, but it's in very specific locations - ones which stock manifolds can't reach. Also I was hoping to get away with air/air intercoolers, but that just doesn't work. So it's air-water, with dual circuits for heat exchangers. At 14,000 feet we'll be pushing around 20 psi boost to maintain 29psi absolute intake pressure, which is roughtly 3:1 pressure ratio. So while the goal of 700 hp may seem modest by LS3 turbo standards, achieving it at altitude is anything but.
The pictures are not renderings, they're real-time screenshots from our workstation using AMD Radeon Pro WX7100 card. It may seem like frivolous extra but in actual use I find it extremely helpful to be able to spin the assembly every which way with no delays, and full visualization. When you need to connect complex 3D dots, it really helps to have the computer waiting for you rather than the other way around.
Now that the basics are figured out, it's on to actually making it in metal. Still waiting for some pieces to show up, but we've started on it.
The gearbox mount or the Mendeola S5R sequential transmission is now designed and made. Suspension and other assemblies are coming along too.
But this isn't the only D2 we're building. So one of the others is coming along as well. This one is using a Hewland LWS sequential box, which just arrived.
While the Pikes Peak car will stay a raw 'roadster', this one will be the first to get the coupe bodywork, HVAC and upgraded interior. We're working on some concepts - these are just initial sketches, courtesy of Joshua Gore:
We've already gotten some customer feedback so the concept will continue to evolve. Some of the key goals are replacing the digital dash behind the wheel with analog tach/speedo, moving the digital dash to center console, providing HVAC vents and controls, and more flexibiltiy on digital/analog gage mix. Defrost is a necessity, and accommodating knees for drivers over 6'5" is desired. That, and making the whole thing look more refined, weatherproof, and functional as both coupe and (non-weatherproof) roadster. Easy, right?
The trailer design and construction is progressing as well. We've made a solid mount for the Trailer Valet and have finalized 4-wheel tie down spots. Waiting for the surge brake assembly and will start on enclosed canopy shortly.
On the less-D2 but still related front, the GTC upright project is also under Pikes Peak related time pressure and we're getting it done.
Of course this is only a fraction of what we're currently doing but enough for this blog entry.
04/25/17 The main (but not the only) scramble right now is to finish the D2TT build, since Pikes Peak is only two months away. We've been waiting for various parts such as exhaust collectors, but today they finally showed up. The first header is now tacked together.
Intercoolers were mounted a couple days ago and the intake collector is in the process of being built (some will notice it's not fully welded yet). The intercoolers are supported off the engine by fairly simple fabricated angle brackets that bolt to the heads. Seems pretty solid.
The collectors are double-slip. A lot more progress will come on this in the next couple days. This is what it should look like when all done.
The CAD model doesn't show wastegates or blowoff valves, those will be added shortly. Parts themselves arrived a couple days ago. This is a mass airflow setup so BOVs will recirculate upstream of the turbos instead of venting to atmosphere. This car will get last year's prototype bodywork so at least that part is already done.
We do need to fabricate new wings for it, and that's still a process. We've tried numerous resins, gelcoats, layups and processes. It's getting better but the test parts are still not coming out the way we want. This is exactly why we don't do structural composites - process is everything, and a lot of the time you don't know if the part is good or not without destructive testing. We're just not set up for it. However cosmetic and semi-structural parts like wings are within reach and it's our goal to get good at doing them. Here's an example of a recent part - you can see it has some dry voids along the weave. It starts saturated with resin, so it's not from lack of that. Something in the process draws it out.
But we've nailed down a lot of variables already, this will get resolved too.
I've been posting GTC upright progress here, since they can (and likely will) be D2 upgrades. We're now done with all machining. Aluminum parts are back from anodize, steel parts are at heat treat and will go to plating next. Corvette bearings have been modified for the drive pins.
I may have mentioned that these have been some of the most challenging parts we've done machining-wise. The toughest of them are the stub shafts, which both transmit the torque from CV joints to the hubs and hold the wheels on. Our equipment is pretty compact so we're stretching the limits of its capabilites, and have to be both clever and very careful in the setup.
Each shaft starts as a 47lb billet of alloy steel that is machined down to about 4 lbs in the lathe.
It then goes out for splining which we can't do inhouse. Next come the mill ops. One of the many challenges is holding the parts securely and precisely in several orientations (within 0.001" in XYZ). Below is a screenshot of the tooling jaws I designed for the job. They do a lot, including other parts that go into the upright package.
We are especially constrained in Z travel with the mill. Below is an illustration of the part in the fixture, and the tight clearance that occurs during tool change. It is not coincidental but a result of much optimization. As we say, clearance is clearance.
There are quite a few tricks necessary to keep things from crashing into each other. It's complicated by the fact that we're tapping threads into steel, which is prone to breaking taps and getting them stuck. This actually happened here so I reverted to the strategy of starting the treads in the machine to make sure they're perfectly straight, then finishing them by hand later. Fortunately we were able to save the part.
The horizontal ops are less scary but equally challenging, since the drilled hole needs to be perpendicular to the milled slot.
Machining more mundane parts afterwards is a relief of sorts. Almost vacation-like :) And then it's done.
Some might notice that there are actually three kinds of shafts in the picture - large CV, medium CV and no CV. Subsequent parts we produce will have material sized appropriately and will significantly reduce the machining time, but since the mix actually changed mid-stream on this batch, we started them all as full billets. Yes, we recycle the chips. No, we don't get anything worth mentioning for them, it's more for the environment than any financial incentive.
Like all our upright designs, the GTC has a large degree of modularity and we can accommodate a wide mix of geometries, CV joints and brake packages. The two current GTC customers are very different - one is an LMP style endurance racer powered by new generation Hartley V8, the other is the Envate Hypercar. The endurance guys are using AP Racing brakes:
The Enviate uses an even bigger Stoptech setup with carbon rotors. I'll post some pictures when I have them.
Keep in mind that the same upright will work on the D2 as well, with some suspension arm changes. If you have a build that could use them, let us know (we can do standard Corvette or 5x114.3 bolt pattern if centerlock is not necessary, at significantly reduced cost). And, the parts we've devleoped can be used to make a Corvette centerlock kit - HRE and Jongbloed can make the wheels to work with it.
5/9/17 Work continues at a crazy pace. The Twin-turbo D2 is currently the most time-critical but there are several other items that are just as urgent. One of the biggest challenges with the D2TT is the packaging - getting everything to fit in a way that is efficient and will work.
As a bit of background, our goals for the system are quite different from most twin-turbo LS builds. While it's possible to get well over 1,000hp we're looking for 'only' 700 or so at the crank The catch is that we want to see that at 14,000 foot altitude and have instant spool-up for clean corner exits at Pikes Peak. So we've chosen smaller turbos than you'd normally see - GTX2867R. Each is good for up to 480hp so between the two of them, 700hp is still pretty mild. It's actually the same turbo we use on the Hayabusa-powered D4s and total gas flow is very similar - 1.4L 10K RPM vs 3.1L at 6.5K RPM for each half of the LS motor. And at altitude the operating point is right in the peak efficiency island on the compressor map.
As an added twist, another goal was to make the system retrofittable to existing cars. We wanted to maintain MAF operation and original cold air intake location behind the driver's seat. The intake and exhaust plumbing compete for space with cooling system, oil systems for engine and gearbox, wiring and a few other bits.
The various manifolds are a challenge but I'm fortunate to be able to call on Mark's and Tristan's fabricating skills. If I can CAD it, most likely they can build it. Here's a test fit with the water plumbing in place.
Everything has to be fitted, marked up, then taken out and modified. A few times. But now the intercoolers are mounted, all the manifolds are welded, and it's down to finishing the various systems and integratng them with electricals. Then comes heat shielding - that will be its own challenge.
The car is looking more complete by the hour.
There is still a lot we are having to figure out on the fly. For example, the Mendeola S5R transmission is unique in having two shift actuators - one for forward gears, and a separate one for reverse. The forward stuff will be actuated by electronic paddle shift, the reverse will be manual. So all the mounts and even the reverse selector lever had to be designed and made.
This is where having CNC equipment really pays off. I can go from idea to part in 3-4 hours, even on a weekend, with the only direct cost being the material. It would take twice as long to 3D print a prototype.
But, 3D printing has its place in what we do. We recently had our industrial design intern Maika start his summer term with us, and his first project was finalizing the design for D2 turn signal housings. After that was done, Jay 3D printed the parts. Maika is now incorporating the pieces into the original bodywork patterns. Once that is completed we'll make dedicated molds just for the housings, which we can then make in carbon or fiberglass.
Exactly how the actual lights will be implemented is still subject to some experimentation.
Maika's other current project is the new D2 interior. It's a very complex 3D puzzle with many simultaneous (and occasionally conflicting) requirements. He's already making good progress.
These are still concepts but we're narrowing it down rapidly. One key design parameter is modularity so that we can precisely tailor a configuration to customer preference.
Simultaneously, work is progressing on getting the D2 into rFactor2. One would think that if the car exists in Solidworks, importing it into a sim-compatible format should be just a matter of a few clicks. Puzzlingly, it's very far from it. Solidworks operates on solids and maintains the necessary precision for manufacturing. Sims operate on polygons and require models optimized for real-time visuals. As an example, a model of the D2 can be converted (with some effort) into a polygon mesh of about 5 million triangles. What a sim needs is about 200K quadrangles and there is no available automated path from A to B. The short of it is that the best way to create a sim model from a Solidworks one is to make it from scratch, using the original only as a guide and template. Baffling, but I've talked to many people in the industry and everyone who knows what they're talking about has told me the same. Fortunately there are people willing to invest the effort so things are moving along. It's still very much an art.
The D2 trailer is moving forward as well with finalizing over-the-tire tiedowns, Trailer Valet mounts, car centering mechainsm and a few other bits.
And this is just the D2 stuff. There's a lot more happening.
05/25/17 Some major steps forward. Yesterday we finally fired up the twin turbo car. The complexity of all the systems adds up. From gearshift to turbos to cooling to oiling to suspension to wiring, and many more...
Even relatively simple things like wrapping the exhaust require some planning and care.
The car has to go up the Mountain in 10 days in testing so this is crunch time. The first start didn't happen easily - engine would crank but not fire. Lots of head scratching, lots of testing. Finally at some late hour Jay found the issue - the wiring 'pigtail' we bought for the cam sensor had two wires swapped. Simple fix and now it runs. Time to tune it.
Portland Speed Industries is our go-to tuner and they do a great job. Despite being booked solid they made time for us at 7:30 in the morning to see where this beast is at. As mentioned before, we're not looking for crazy power - about 600 at the wheels (700 at the crank). The challenge is that we have to make that at 14,000 feet and have it be very tractable.
A few mild pulls and the engine is working better. Then at about 575 rwhp we ran into an issue - what appears to be dropping fuel pressure. Last year's LSA motor put out 550 at the wheels and was fine. We are using a Walbro 255 fuel pump. We kind of expected that it would be close, and it doesn't come as a big surprise that its capacity is exceeded. So we have to swithch to the 400 model. Also the shifter needs work and a few other issues need addressing as well. But the good thing is that nothing leaked (thanks to Tristan taking care of all of it beforehand) and nothing broke.
So the rest of the day was spent procuring and installing the new fuel pump, tweaking the shifter, and making a few other changes. One of them is adding ducts in the floor for better airflow. A while back I ran some CFD in SolidWorks Simulation and after several iterations found a configuration that should really help.
The future versions will be CNC cut and bent like all of our production sheetmetal, but in this case it's up to Mark to fabricate the parts the old-fashioned way.
Tomorrow is another early morning dyno day. David, the car's owner and long-time Pikes Peak competitor, will arrive with his trailer to take the car to Colorado. It's crunch time. But then again it has been for the last several months.
In the meantime many other things are happening at the same time. On the D2 front, Maika is maiking progress on the interior and part of that is more organically-shaped seats. Once we agreed on a promising design, a prototype is in order to see whether it's actually comfortable.
The new seats will start out as composite inserts into our existing aluminum seats, and so it makes sense to use one as a base for the prototype. Looks promising.
Needless to say, there will be lots to update about shortly.
05/27/17 Crazy day and a half. Lots of parts. Lots of systems. Lots of tasks. It continues to amaze me just how much goes into a car. Especially one like this. It is actually the most powerful car we've made yet and the first D2 to roughly match the D1 in power/weight.
The fuel pump definitely made all the difference, which makes sense. It's actually fun to see correlation of theory and practice, and it's another bit of practical knowledge gained. After a few expert changes by Jason at Portland Speed Industries, the results are 674 horsepower at the wheels. On pump gas. This translates to about 800 hp at the crank. We were only shooting for 700 so all is well. Ultimate test will be on the Mountain.
Then some work on the transient behavior, cleanup of a few lean spots and it's ready for track testing. Here's a quick video of some of the pulls. David arrived just in time to witness them.
While setting corner weights without bodywork we saw total of around 1,900 lbs, it will be around 2,100 lbs with body on.
The chassis and the drivetrain are brand new, but this car gets to wear 'old' clothes - our prototype bodywork that was on last year's supercharged D2RS. That chassis will get many updates and all-new coupe body, interior, HVAC, etc. With the body on and last year's vinyl still on it, the car looks the same. But it's only in appearance.
We are always pushing to improve what we do and learn. This car represents a multitude of significant steps forward, which wll be incorporated in all our future builds. The front wing is one of those things. It was designed some time ago, and skins were made a while back as well, but we hadn't put one together until now. Maika got to practice his composites skills.
After working out a few installation details, the fit is good and the tire clearance with wheels turned is adequate. Rear wing mount was updated as well. And Mark finished the floor updates.
That's a number of parts designed, material procured, machining, bonding, cutting, bending, trimming and installation done, all in the space of less than a day. Nothing like a deadline to push things forward. Tristan and Jay stayed late putting everything together.
David was already on the road to Portland when I texted him that we finally started the car. By the time he arrived we were finishing up the second dyno session having replaced fuel pump and a few other things, and the following day we were at ORP track testing.
The day went well all in all although there are still some things to sort out before it's ready to go up the Mountain in testing. We have 5 days to do that. After the day was done David continued on to Colorado with the car, while we headed back with a task list. It's encouraging so far.
Thursday we also picked up Rodney's engine in Seattle and will be installing it in his D1PPS shortly. That car has to get sorted for the race as well, although we have a few more days since Rodney isn't doing the early testing this year.
One example of random challenges - M drove the van to Seattle to pick up the motor (and drop off the turbo Hayabusa engine that's going into the D4 we're finishing up). While there she visited family for a couple hours, parking the van on a residential side street. When she came back to it, there was what appears to be a bullet hole in the side window. Why or how is unknown. Fortunately she wasn't in the van at the time and nothing was taken. Could have been much worse. But it's just another thing to deal with now.
It'll get replaced shortly, for now it's held together by tint film and packaging tape.
Anyway, one major thing done, but so much more to do still. Next few weeks will be very eventful. Stay tuned.
08/15/17 With Pikes Peak now 6 weeks behind us (see its own blog for the story if you missed it) we're hard at work catching up on all the projects that got pushed back for the race. I've posted some D4 and D1 stuff already, now it's D2's turn.
One thing we're doing as a result of the Pikes Peak effort is looking for more downforce. I've been running a lot of CFD and have come up with a number of tweaks that collectively should take downforce from around 150-170 lbs at 100mph to more like 300 lbs. Of course there's a drag penalty but with surplus of power it's the right tradeoff for the application. Among the numerous changes the front 'dive planes' are among the most effective, contributing nearly 70 lbs cumulative just by themselves (though part of that is in how they interact with other things).
A number of combinations and configurations have been run, and I have a few more to try. Then we'll make a set and see what the correlation is with real life.
On the subject of aero, we have now made a wing for one of the Drakan Spyders, which is a D2 derivative. This forced us to figure out the whole wing making process and after a few trial-and-error iterations it seems we have it figured out.
The mounts took a couple iterations as well. This first set of clamps didn't work well, so everyone at the shop got a paper-weight souvenir.
The next iteration did work well.
We have several D2s in the process of being upgraded to the new bodywork and the first set of 'production' roadster panels is being made now. Coupe will follow, and the rollcage modifications to the chassis have started.
Another long-time project is the D2 trailer. We've now got it to a towable state, though a few things still need to be figured out.
And as a final bit, development continues in conjunction with JFC Racing on the GTC uprights. These are a derivative of GTX used on the D2, and will eventually be an option for D2 customers who want centerlock wheels and a more race-oriented upright. The current iteration is floating brake hats of a different design than what we've done before. Previous version wore too quickly and we discontinued it. We'll see how this one works.
10/10/17 Couple months since last post here but we've been super busy. There have been progress posts on the other blogs, here's some of the D2 related stuff:
We're updating several of the original cars to the new style bodywork. Part of the transformation involves frame modification to swap out the rollcage, and for coupes cutting down the side rails and adding new side reinforcements.
One of the cars is getting AirJax as well. Packaging is tight as always, so we've decided that a 3-jack solution is best. It provides even weight distribution, once I found the right spots for all the jacks. A quick test simulation with scales and three regular jack stands confirms it.Then it's only a matter of designing and fabricating the mounts.
Now this particular frame can go to powdercoat. There are others in progress as well.
The new bodywork is coming along, albeit slower than we'd like due to a number of factors. The first set of roadster panels is made and getting trimmed. It's a labor-intensive task, especially the first time through when we're still trying to figure out the exact details and processes.
Wings are another thing we're figuring out. It's definitely a learning curve and the first few take an inordinate amount of time and effort, before we find out what works and what doesn't.
We are also starting another D2 based project - this one is a special, in cooperation with Willamette Pattern Works. The body design, molds and body parts will be supplied by them while we supply the custom D2-based chassis and suspension. This project will likely get a blog of its own soon. More details to follow.
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