dp1, custom built 4WD racer

[mikelzapi3]

I found this site 2 years ago and i found it very interesting, so if you want this is the link to the main page (the guy talks also about his other stuff, motorbikes, a mini...he had also some Elises, BMWs, a new M5 but he sold them..)

http://www.dpcars.net


He seems to be very serious (and had a lot of money for his projects ), he is building his own racing car with a hayabusa engine, all wheel drive, superlight contruction...he have been doing this project more than 4 years and now is near to completion of the first prototype. He also plans to build more and sell them.

the DP1 page link is in the main page, the 5th icon (the black small car) in the menu from the top.

I've tried to find in the forum but I din't find anything, so I think it isn't a repost, if so excuse me.

[Vindesh17]

seems interesting.

[ferrarifreak013]

thats impressive cant wait to see some good videos. that thing would do an autocross track like nothing. wow he looks like he has had a very very fun life, and i emphasize the word very.

[culver]

I’ve looked at that guy’s site quite a bit. It’s a very fascinating project. Unfortunately I think he is going to end up with a very expensive but not very good track car. Basically, if his intent were to make a great autocross toy/track car toy he would have been better off buying a used Sports2000 or Formula Continental then converting them over to motorcycle power. As is, his design has quite a few flaws. Basically he has shown great care and diligence in his design but little experience. I personally have not designed a car but I have helped other people design race cars (SCCA open wheel cars). I reviewed this design with some people who do design racecars for a living and got their take.

Here are a couple of issues:
Chassis flex: The chassis isn’t going to be very rigid. The central box section of that chassis is the only part that will provide any significant stiffness. Many of the stress skin panels that close it up have openings in them for access. Even if they were fully boxed the whole section is about 12” x 12”. That’s not much. Modern tube frame race cars, like a composite tub carry the loads around the entire diameter of the frame. In a sense they act like a 2.5 foot diameter tube rather than a 1 foot tube. Larger diameter will be stiffer.
The driver’s cell also looks poorly supported. The roll bar has very little support for its height. The outsides of the cell are not properly triangulated. It appears he is using the stress skin to absorb compression loads. Stress skin can only absorb tension loads.

Having looked at the PDF files there were some issues with the suspension geometry. This was an area where I get fuzzy because I’m not a suspension expert but it had something to do with jacking effects because the lower suspension arms were effectively parallel to the ground.

The single central brake caliper isn’t a good idea either. Many racing teams have tried inboard brakes and basically all have moved back to outboard. He will likely have cooling issues and problems with CV joints. Also, using the brake on a Torsen dif will likely be problematic. If one wheel gets in the air he will loose brakes on that axle. He also may have brake proportioning issues and if the brake loads are high enough he may break the dif. The difs are rated for a given torque load. If he sized the difs based on the motor power he will break them under braking loads which are effectively much higher torque loads (This also might brake the CV joints).

As a track car is also has issues. The car has a short wheel base and what appears to be a narrow track. That isn’t a good idea for just about any type of race car. Basically when you start cornering you want to distribute the cornering loads to all the wheels. With a narrow track and wheelbase more of the loads will be transferred to the outside tires. That will reduce ultimate grip. While the grip of a tire does increase as the load on that tire increases, it does not go up at a 1:1 ratio. Twice as much load results in somewhat less than twice as much grip. Thus you are better off sharing that load over all 4 tires rather than just the outside ones. This is why F1 reduced the track width of the cars to slow them down a few years back.

The same issue applies to braking. A short wheelbase doesn’t help braking. You will get more forward weight transfer than in an otherwise equivalent long wheelbase car. While being narrow might help the car carve straighter lines around a tight autocross course, being shorter only helps you parallel park (with in reason).

All this said, I give the guy a lot of credit for trying and the workmanship is first rate. However, it is clear that he doesn’t have a background in chassis or suspension design. Based on the opinion of experts I know, I don’t think the whole will be greater than the sum of the parts.

[mikelzapi3]

I agree with you, the car will be very expensive comparing with the performance.

I'm only an engineering student and I haven't got experience with racing cars (I envy so much people like you ), but that chassis seems very simple, although I think he is planning to do the next prototype of carbon fiber.

Also, the brakes layout seems problematic, personally I don't like it, the cooling, performance and axle overload..but he did that to save weight and $$$

The engine layout...I'm not an expert but I think it would be bettet to put the engine behind the driver and the fuel cell (although he has made a well balanced car, near to %25 weight in each corner with the driver in).

well I have some questions , what you think about:

* The chassis design, apart from being not good in terms of performance, in terms of security, could you say if that is secure. Because without doing a crash test or FEA simulation....I wouldn't drive a car done by me How could you make a %100 secure design (well, asuming we can't do simulations and crash test, so making a wise overmeasuring )

* Is there really a need for use 4WD, the weight isn't much, but with a hayabusa 1300cc motorcycle engine, would be a problem the lack of traction ?

* what is better for aerodynamics, a open wheel or close whell design ?
(I think it's better the close whell design, but the F1 cars are open wheel, perhaps because the regulation)

My dream is in some years to design a hill clim race car (only design it in CATIA and simulate using MSC adams, fluent...), and if i had enough money perhaps build it.

I have in mind a osella PA20 style, le mans style car, smaller with about 350 Kg, aluminium chassis, motorcycle engine (turbocharged dual intercooled hayabusa engine with about 300 - 330 HP), use the vaporisation or latent heat of water for cooling (banned on F1), rear wheel drive, padle shifter, high downforce with underbody all long ventury tunnels with side skirts touching the ground like early F1 ground effect racers, high downforce rear wing and some front wing like audi R10 (drag isn't a great problem in hillclimb here, very twisty roads with low speed, max 200 km/h, average 85-95 km/h)

this car wouldn't be legal for racing, I would make it as illegal as possible with all the technical stuff banned, and then try to race it in a local hill climb in a special category (not sure if this can be done).

obviously i haven't the knowledge and experience to do this project, but i'm trying to find information on forums and webs. Also the things i study at the university are very usefull to understand any text i find and to have a background on dynamics, vibrations, fluid mechanics, thermodynamics and of course in welding (I've finished this year technical mechanical engineering specialized in welding, next year I will start the last 2 years to obtain "superior" engineering title in industrial engineering, so perhaps I can help you in welding problems )

[culver]

If you are really interested in this sort of thing the best thing I can suggest is get to know someone who is really involved in racing and particularly race engineering. I grew up around amateur race cars. The picture below is an example of the sort of car's I've been around (well the ancestors to these anyway)
http://www.hemes.net/Images/PH%20VD%20from%20above.JPG
That's a Formula Continental. It's a class down from an F3 car. Tube frame construction with fiberglass/Kevlar body. It’s actually a derivative of the car in the link below. The primary difference is the one below is older and doesn’t have wings. However, the two classes are sister classes and the cars could be converted from one two the other. Fundamentally the only difference is adding wings and a bigger motor.

This guy has lots of good pictures of a 1984 Citation Formula Ford he restored and started racing. Despite a huge power deficit, the Ford would like run circles around the DP1. Basically the FF runs on real race tires so it will corner much harder. That despite weighing a lot more and having a weak 116hp motor (mandated by the rules of the class). The site also has a good, old Road and Track article about the Swift DB1 race car.
http://www.chrismore.com/index.cfm?catID=11
I know a guy who drives a similar but newer Formula Ford. When testing he has shared a track with street legal 911 turbos. The 911’s can accelerate faster but he turns so much faster that the 911 is just barely catching up before the next turn allows him to pull away again.

Anyway, those are the sorts of cars I’ve spent a lot of time around. So to your questions which I will answer to the best of my knowledge:

I wouldn’t feel too safe in that car. The roll bar seems too tall and not very well supported. Note in the pictures on Chris More’s site how the structure comes over the driver’s shoulders. In the DP1 the bar is basically free standing from about elbow height to over the driver’s head. That’s a very tall bar that could fold over.
Next, the driver’s cell hangs off the side of the chassis. It doesn’t have much to support it. Think of a bridge that’s only supported on one side. Well if you have some diagonal bars to help brace it that makes it much stronger. He doesn’t. The outside wall of the driver’s cell has very little to keep it from folding into the inside of the car in a wreck. Any time you have a basically flat wall it will not be strong when you push on its side. He has basically a flat wall on the outside of the driver’s cell. Nothing to absorb a side impact.
Now he does have a crush structure in the front of the car. It’s very good that he has it though I can’t say how well it will work.
FEA is a very good tool but in general it can’t be used for accident testing. Yes, if you are a big car company like Ford you have the very powerful software, computers and experts needed to run computer simulations. Most FEA software can not model something as complex as a crash. Some of this is simple intuition. Having a good sense for what is or isn’t going to crush in a wreck. Of course we want some parts to crush to reduce the G loads on the driver and other parts to not crush (basically the area around the driver). We also want to make sure the driver’s body doesn’t hit anything too hard or sharp inside the car. Even a low speed wreck is fatal if we have a big nail in the center of the steering wheel!

4WD: Maybe. Keep in mind that basically all cars have 4 wheel slow down… ie brakes at all 4 corners. In most cars all 4 tires help the car get around the turn. It does make sense to use all 4 wheels to accelerate IF the engine has so much power that it spins the tires the rest of the time. Now if you don’t have much power you don’t need 4WD on dry tracks (Rally is different). I can’t easily say how much power his car could or couldn’t handle. With race slicks he could probably handle upwards of 250hp without needing AWD without larger tires. The older Ralt Made Toyota Formula Atlantic cars put down ~240hp via tires about the same size as his. At lower speeds perhaps he would need AWD to handle 300hp without race tires. I suspect with Formula Continental sized race tires he would not need 4WD with the Hayabusa motor. Certainly not on an open track but maybe in an autocross. He certainly added more complexity that he needed by adding AWD. I seriously doubt his car would be faster than a DSR with the same motor.
4WD has been proven in racing. Indy and F1 have rules against 4WD because those cars would benefit from the extra drive wheels.

Closed wheel cars are more aerodynamic. Given roughly equal rules I would expect closed wheel cars to lap a track faster than open wheel cars. Basically if rules allowed almost every type of open wheel car would do something to cover the wheels to reduce drag. In racing rules are a funny thing. F1 is certainly the most technologically advanced form of racing today. However, today’s F1 cars can’t generate nearly as much downforce as Indy cars from the early 90s or GTP cars from the late 80s and early 90s. That’s because the F1 rule makers have made it harder than it used to be. F1 cars can barely top 230mph in most races. Indy cars used to qualify for the Indy 500 at nearly 240. They have seen peak speeds during qualification of 260mph. It’s not that F1 engineers couldn’t make cars that went that fast (Lotus, McLaren and others built cars for both series). The F1 rules simple are different and the needs of the cars are different.
Anyway, closed wheel cars typically can be faster and generate more downforce but typically are heavier.

If your dream is to build a hill car I would suggest learning all you can about fabricating parts (forming and welding metal and the like). Again, I would also encourage you to hang around racing because you will pick up so much knowledge that way.

Best of luck!

[mikelzapi3]

Thank you very much!

The chrismore web is great, i usuallly visit http://www.mulsannescorner.com (You probably knew this web, is very famous), and http://www.gurneyflap.com

About racing in my country, we haven't got a racing track in 300Km distance, and amateur racing...is very amateur, people only modifies stock cars for hillclimb or buys motorcycle powered small toys, this one is the favourite of most racers http://www.bangoracingcars.com/. The most famous hillclimb is the jaizkibel hillclimb, here you can see the lola BMW doing it http://www.youtube.com/watch?v=GHrHLSjPnvQ and that's all.

In the other corner, few years ago Joan Villadeprat ( a former benetton chief engineer, I think he won 3 or 4 F1 world championships, one with Schumacher) build a High performance automotive competition center here, they won world series (F3000) last year with Kubica (now racing for BMW sauber) last year, and they are very competitive, I visited thei headquarters with the university and it is amazing, now they are designing a closed cockpit LMP1 racer for 2007 with John Travis as chief engineer ! http://www.epsiloneuskadi.com/english/index.htm
Also they are fighting to build a racetrack here, but there are a lot of mountais here, so there is no enough space....let see what happens.

To get there they have a automotive racing master for only 22 students, with real life practics, and after the year if you are good, they choose you, even you can work in F1. But to apply for the master I have to finish engineering and then fight with other 450 applicants (last year there were about 460 ) from all over the world for only those 22 places, so it's very hard. Also I only like motorsport like a hobby, not as a work, it is very hard to travel all around the world and they don't get paid very well.

well thak you, and if you know some interesting web please post here, i will be very grateful

[mikelzapi3]

I've forgotten, also I like the DSR more than the DP1, the body and the layout