Wednesday, August 15, 2012

Mono Build Entry #4

Today we received a couple of presents from Cosworth!  Two engines came in today from Cosworth that are ready to be bolted together with the Hewland sequential and put to life. Some prep work needs to be done on the gearbox and bell housing before we will be able to squeeze the assembly in the chassis, but that's the fun part!

Oil Pump Gear Development

We began working on an uprated oil pump gear last year but put the project on hold as other developments took priority.  We have begun working on it again this past Spring.  This entry is an update on an effort that is not yet complete.  As one of my old Ph.D colleagues from 3M Automotive used to say, "R&D ain't easy"!

The factory oil pump gear is a known weak link in the 2ZZGE engine in cars that see track use.  We believe that a combination of high rpm (7k+) coupled with oil starvation (we know how to fix this) creates a hostile environment for these stock gears.  Sintered metal parts start out as powder.  This powdered metal is compressed in a shape, heated in a controlled environment and then machined to create the final part shape.  This is a cost effective method to produce parts that require tight tolerance.  The oil pump gear is considered a gerotor (see Wikipedia) type.  As the inner and outer gears interact with each other, oil keeps them from grinding on each other.  If the oil is starved from this system the gears will destroy each other causing all loss of oil pressure and bigger problems for your engine.  If the gears are made from a brittle material they will be even more vulnerable.

We started working on a solution last year that we believed would be an effective replacement.  We had it made from  billet 4340 steel, REM finished and precision ground.  We tested them on track and data logged our results.  We blogged about it: HERE.  We thought we had a good product until we removed it from our engine to inspect it.  The gear teeth had deformed.  Clearly it was not ready for prime time so we went back to the drawing board.  

Our supplier is a well recognized and experienced gear manufacturer.  They scratched their heads for some time as well and delivered a couple of new gears.  These had some changes that they believed would improve performance.

We installed the first configuration and took our test Elise to our race shop at Spring Mountain for testing.  We put about 290 track miles on the gear and recorded the conditions.  Oil pressure looked great and the car ran fine.  We removed the gear and found that we had made some improvement but still showed scoring on the teeth that was not acceptable.  See picture below.

So the third configuration was installed and we headed back to the track.  250 track miles later we yanked out the gear and inspected it.  This time we found the gears were in the best condition so far.  In fact they exhibited some wear that you could see but could not feel.  It was similar to the wear that we found on a Circuitworx gear that we had.  We then looked at the oil pump housing and realized it was scored - but did that happen with the initial gear?  Aarghh!!! (A Charlie Brown moment for sure).  We bought a new housing and will be testing the gear again soon.

R&D is always a challenge in a small company but we feel this is the difference between simply fabricating a part and engineering a true solution.  So back to the proverbial grindstone...we'll keep you posted as we continue our development on this product.

Friday, August 10, 2012

Mono Build Entry #3

With the gas tank cavity assembled and awaiting the tanks arrival, we have focused on the fire and brake bias systems (both options, selected for chassis 0007) plus the front shear plate area of the chassis.
The optional fire system has six blue nozzles, two in the drivers compartment, 4 in the engine bay. The following picture shows the two drivers compartment nozzles, peeking out from behind the front roll hoop. The black boots on either side of the brake pedal cover the bias bar's clevises. When we have more of the interior installed, we will install the cable from the bias bar to the cockpit, allowing on-the-fly adjustment.

All of the fire system lines are hand formed, then test fit, then sheathed with a fire resistant material. The bottle is attached to the sub floor, with one line running fore (then immediately T'ing for the two drivers nozzles) and one line running aft. The blue masking tape on the right is to temporarily hold the aft line in place until we install the fuel cell.

 Here you can see the back side of the gas tank cavity, and all four nozzles in the engine bay.  It is best to order this option initially, as adding it later is a challenge, especially once the cabin is fully built and trimmed.

Here we are up close and personal with 0007’s front shear plate. This shows the careful attention to detail and integration that went into the design of the Mono, with almost every bracket having multiple functions (are those BAC guys channeling Chapman?). The billet front shear plate, for example, is a structural member of the chassis that also holds the steering rack, wishbone mounts, and the front storage box bracket. The storage box bracket, in turn, also holds the reservoirs for the clutch and brake systems.  Clever and beautiful!

Monday, August 6, 2012

Mono Build Entry #2

Now that most of the parts are out of the boxes and in order, we start to assemble. We are going to start with the gas tank cavity, and since the gas tank is right in front of the engine we need to put some sexy gold heat wrap around the bulkhead panel that the tank sits in.

Like everything with this car, it all has to be fitted and measured, it does not come prefitted and cut. So we have to cut it to size and make sure it's perfect.

After the panels are all dressed up, we can start to assemble the rest of the cavity using about 100 rivets and install the tank.