11/11/10 Just a couple quick things. First, the official dp4 brochure is ready - click below to download it in pdf format.
While preparing the pictures I tried out a few colors for the car, just for fun. I like it in yellow.
Right now we're basically waiting for a bunch of parts to be made and taking care of a few client projects. We won't be doing anymore testing this year most likely, as the season is pretty much over, but everything is moving forward. A lot is getting done, much more still to do.
11/20/10 A few updates. First, we've taken the Mothership to get winterized and then put it into storage. Frees up a lot of shop space. But before we did that, the trailer with its observation deck turned out to be quite useful for changing light bulbs on our 19-foot tall ceiling.
Progress continues on customer dp4 build, the car is basically ready to sit on its wheels but I want to get more fitting done first.
One reason for the delays (along with several client projects and the fact that the customer doesn't really need the car till Spring) is all the new stuff we've been learning from running the prototype. As a result I'm redesigning the primary chain drive to incorporate a 'cush' feature and a number of other detail changes. The next car we will be building will most likely be an AWD turbo Hayabusa and I want to make sure the drive system is up to handling the higher loads. This kind of evolution will continue for a while, but to the extent that we can get the latest-greatest on the early cars it makes sense to do so.
Another porject that's movig forward is putting the dp4 into the rFactor sim. We're pretty close now, with significant improvements to graphics, physics, sound and setup. David stopped by to try it out and quickly got addicted. He's driven both PIR and Laguna in real life and really enjoys driving these tracks in the sim. The realism takes it well past being a game.
I've found that generally people who are not experienced gamers but who have driven the real-world tracks will get lap times similar to what they'd do in the actual car, on their 3rd or 4th lap in the sim. After that they get better at the sim and my next project is to see how the improvements in virtual driving can be translated back to the real thing. My theory is that it has a lot to do with 'programming' yourself for certain pace, a 'rhythm' of sorts.
For comparison, after driving the dp4 quite a few laps on both PIR and Laguna, I had David try the E46 M3. It was pretty funny to watch him falling off the track at half the pace and listen to him complain about how slow the BMW is. His laptimes were consistent with an intermediate-driven M3. The dp4 does recalibrate you even in the computer and going back to ordinary cars is disappointing and frustrating. I've mentioned this already regarding my own experience with the Exige. So it seems there is a very high degree of correlation between the sim and the real world, on several levels.
A final touch that is rather priceless - in the middle of driving the M3 David got a call from his wife and so there he was, driving and talking on the cellphone. Typical BMW driver! :)
How much more 'real' can you get?!
12/07/10 Among other things, we are putting the finishing touches on the first release of the dp4 in rFactor. To that end I've created a few 'standard' skins...
And of course we had to do some 'custom' ones as well. Tristan did his own and I made one for M and myself.
Besides being a really impressive dynamics simulator, rFactor turns out to be a great visualization tool as well. It's fun to see the cars running around various tracks. The official first release is still a couple days away but in the meantime here's a video of what it looks like.
We've already done some correlation of sim and real world and the plan is to do a lot more of that next year. As we learn, the model will get refined and updates will be posted on as-needed basis. Should be fun! With that in mind, if there's a FSAE student out there who'd like to do a lot of datalogging, simulation and correlation of the two as an intern next year - drop me an email and let's talk. There should be enough stuff to make a thesis out of.
Below are some notes on the mod, these can also be found in a pdf inside the zip file.
Our basic goal with this mod was to create a simulation model that we could use to help evaluate, test and tune our real-world cars. We have made an effort to have the model reflect the design, specifications and characteristics of the real car as closely as possible. We are quite pleased with how this initial release turned out. Comparing sim Motec output at Portland ('Vanport') with real-world data shows very good correlation. We've had drivers of various skill levels drive the car in the sim and their Vanport lap times correlated closely with the times they set in the prototype. Overall dynamic behavior is true to life as well. This is very encouraging and supports the use of the sim as a RL development tool. Going forward we intend to do a lot of testing and data comparisons, evolving the real dp4 and the sim model together. We'll be releasing updates to this mod whenever we feel significant enough changes have taken place.
In keeping with the realism goals, the options available reflect the actual options you can specify when buying a real dp4. The prices are set to reflect pricing as of December 2010 (subject to change without notice). This rFactor mod therefore gives a very good indication of the performance that is available for the money.
- Base Configuration is what one would typically use at a trackday or casual competition
- DSR Configuration complies with SCCA DSR class regulations
- Hillclimb Configuration features AWD and Hayabusa engine options from normally aspirated to stage I and II turbos
- Fully Configurable car lets the user pick and choose any available combination
The dp4 is a very small and light car (under 900 lbs) with a very short wheelbase and significant downforce from full-length tunnels. AWD option is unique in this class and allows very high power levels to be usable at low weight. The suspension features long control arms and carefully chosen camber gain curve. As a result, some settings (and the car's behaviour) may differ from what one would typically see. We therefore encourage drivers to first become familiar with the car in its stock form before jumping into tuning and setups. We've also found that AI does a good job of driving the car so sometimes hitting 'i' and letting the computer do a couple laps is a quick and easy way to see what's ultimately possible with a particular setup.
- When using a wheel like the G25, it should be set to 540 degrees and steering lock in the sim set to 30 degrees for realistic response. Yes, the car is 'pointy' but it's fairly easy to get used to. Slowing down the steering makes the car easier to drive in the sim but we feel a 'real' response is more fun :)
- Real car's steering is fairly heavy with a lot of feel. Logitech setting of 120% and sim setting of medium effects at -100% FFB approximates it somewhat. RealFeel setting of 0 force (maximum) seems to work ok but of course users may choose whatever suits their preference.
- The car is very sensitive to rear wing settings. This is true in real life, where it's a real handful without a wing and perfectly planted with a proper wing setup. Even a small thing like addition of endplates makes a difference that ordinary drivers readily notice.
- Brake bias is set fairly aggressively forward by default, accounting for the short wheelbase. Moving it back may require more wing which will in turn result in some high speed push. Users can adjust this according to preference.
- Car is designed to use minimal camber, in the -0.2 to -0.7 range, and low tire pressures. In real life we run 12 psi hot on slicks and about 15-16 psi hot on R compounds. That said, further development on the mod's tire model is needed so other settings may work better in the sim.
The mod was developed during the cold/rainy season so we recorded the sound indoors, at no load, with an iPhone. It definitely needs updating and we'll do so once we can record some proper sounds out on the track next season.
Many thanks to Maher Solutions for their work in putting this mod together.
12/29/10 While experimenting with rFactor, took a few seasonal screenshots from the winter version of Nurburgring (yeah, grip levels in the snow are unrealistically high but it's fun to look at :).
We released a V1.01 update of the mod, it can be downloaded from the same location, or just download a patch here. A couple more updates are on their way mostly aimed at optimizing the model for better graphics performance. Real-world related tweaks will come next year.
Speaking of the real world, progress continues. Just got back some parts from the heat treaters, including center torque splitter shafts that will be used with the AWD kit.
Also moving forward with the dp1 again, the goal is to have the first V8 car running by April. And of course there will be an rFactor version. More on all that separately.
01/06/11 The new year brings much activity. Lots happening on the dp1 but not ready to do a post on that page yet. On the dp4 front we've just received another set of bodywork from Contactscale. All pieces still need to be trimmed but generally they'll require a lot less work than the prototype parts did, which is a good thing. We'll be busy for a while just the same.
As we get more cars going, the logistics of what parts get stored where and generally resource management become more important. At some point we'll need to get a multilevel storage rack and a forklift... The real trick will be to set it up so we can still occasionally pull the Mothership in. Of course better still would be to sell the Mothership and get a more compact solution. We'll see.
02/16/11 While most of the effort is currently going into the dp1 and customer projects, some things are happening on the dp4 front as well. The fitting of body and floor is almost done on a customer car. There are detail tweaks that are happening which will be incorporated in subsequent builds. I expect this trend to continue for a while. Will probably retrofit some of these to the proto as well.
In discussions with prospective customers there have been some requests for pre-preg advanced composite bodywork. The current molds are only suitable for wet layup so we'll eventually be making new molds that are suited for oven cure (on the dp1 all bodywork will be pre-preg as standard). It will probably save 15-20 pounds which will make it much easier for one person to handle the body. Since the plug was essentially one-time use we're having to put a fair bit of work into reconditioning it. About one-third done with that. Since Tristan has been working on the customer car, Roy has been kind enough to lend a hand with the bondo and sanding. Glass cover is next followed by primer and a lot more sanding.
02/19/11 Lots has been accomplished in the past week, lots more to do. It's crazy. With all the projects in my head at once occasionally one pops to the surface with an idea. The trailer is one of those - I suddenly realized a better way to do it than what I had designed before. So today being a Saturday and no vendor interactions I took the day to put the idea into CAD. Below are a couple pictures.
Obviously the skin isn't shown, nor are the front and rear flip-up doors, the winch or the ramps. But generally it's pretty close, even the tiedown method is worked out. The tow bar folds for storage and the whole frame weighs a bit over 200 lbs meaning the entire trailer should be on the order of 600 lbs. Not bad for an enclosed trailer that lets you bring along 2 sets of wheels/tires, tools and a couple cans of gas. It will have hydraulic surge brakes and a Torflex axle. The whole trailer is about 55" tall, same as a typical small sedan so it should tow really well. I want one :)
04/12/11 The lack of updates on the dp4 page lately does not mean a lack of activity. It's just that all of it is fairly routine now and this particular blog is getting kind of long (will probably close it out soon and start another one, wrapping up the design/development chapter of the dp4 story). In the meantime we keep improving the design and refining the details. For example the Pilot Pod is now standard in high-temp prepreg carbon. The large weave makes it look like a scale model - it isn't :)
Floor design has evolved and a completely new mold is being made. Little details like exhaust mount, bodywork mounts, wing supports and other items have been updated. Rollbar bracing has been relocated to ease cockpit entry/exit. Cush drive has been added to the drivetrain. Wing has been finalized, molds made and first production parts are being fabricated as this is written.
And so on.
This week Karl is visiting us and since the dp1 is not yet ready, the dp4 proto/demo car will get some exercise at ORP. Hopefully the weather will cooperate. More on that in a couple of days.
04/15/11 For the first outing of the season we did a private test at Oregon Raceway Park, to make sure Karl gets plenty of seat time during his short visit. The facility has come a long way since bare pavement two years ago. There is now electricity, free wi-fi, an office, and of course the track itself is fully marked, curbing is in as are proper corner stations. Can't wait until they put in garages!
This time of year the weather is still very unpredictable and it was all touch-and-go. Wednesday we drove through pouring rain to arrive at a rapidly drying track, with walls of rain all around.
This is our first trip with the new van and trailer (still nameless). Far less luxurious than the Mothership was but very functional. Carried four peolpe, a dp4, a motorcycle, plus all the gear, equipment and food in reasonable comfort. A much more stable towing setup than the F150 was. This will serve us well for a while, until it's time for change again :)
We unloaded about 2pm as the track was drying and Karl was able to go out for a few laps to get warmed up and familiar with the car and the track again. Then the rain came back, complete with hail. We were barely able to roll the dp4 back in the trailer as the first rounds of hail hit.
While the weather outburst was short lived by now it was late in the afternoon and it didn't look like the track was going to dry anytime soon. So we called it a day and headed over to Wild Winds Ranch which is our usual base when we're out here. Having wide open spaces means it's a perfect venue for some target shooting so we brought a small arsenal to take advantage of that.
Turns out M is an excellent shot with the AK although she prefers handguns (and she can still be fashionable doing it :). For me the Kalashnikov just fits and works right. It's an impressive engineering achievement - the design criteria were well defined (reliable, rugged, cheap and easy to manufacture) and were very successfully met. I'm not a 'gun guy' as such but I do appreciate the machinery. Plus, shooting a gun is the closest I've come to telekinesis - just a little pull of the trigger finger and a can 50 yards away disintegrates. If I do it right. No, I don't hunt though I'm not opposed to it philosophically, as long as you eat what you kill.
Thursday morning the sky is cloudy but there is no rain. It's cold (about 40F) and windy, as is usual here, but not a problem. We show up at the track early and Karl starts driving. He quickly gets into 1:47s which is the fastest the car has gone here so far and 4 seconds faster than his best in the V8 Atom. It's still 10 sec off the overall lap record held by a Formula Atlantic but there's plenty more that the dp4 can give and we hope to get down to 1:40 level later in the season.
Going at this pace is a lot of work and Karl takes occasional breaks but still manages nearly 2 hours of tracktime. He has been driving the dp4 in rFactor for some time but this is his first experience at the wheel of a fully sorted real dp4 (he drove the prototype last year when there was still a lot of work left to do on suspension and aero). It was gratifying to have him confirm that yes, in rFactor the car drives just like in real life and even the various techinques we'd been discussing over email work the same in virtual and real worlds. Cool.
I go out for a bit while Karl takes his camera to the entrance of the Half-Pipe for some pictures. I manage a few laps but by now the weather is getting iffy again so we decide to pack it up and head home. Another bit of good news I get from the outing is that the car is essentially unaffected by 30mph gusting cross-winds. You do feel it a little but much less than in a street-based car and it is not an issue in practical terms.
Overall a great start to the season and valuable answers to some of the questions we had raised during the winter. Looking forward to the progress over the next few months as some customer cars hit the track. And of course the dp1.