LocostUSA.com

I see I have not updated how I am doing the rear subframe, so below is a shot of the entire "powerpack" = subframe, rear suspension, engine, transmission, exhaust and rear panel (only one exhaust shown, it has 4).



Its heavy but is attached to the main spaceframe using the bolted flanges at the 2 top pick up points and at multiple positions underneath using the double bolted joint I designed. The bosses and recesses (shown separated below) on the connectors mean the bolts are only ever in tension.

Finished roughing out the shell - weight is around 255 lbs - comprising 4mm thick polyester resin and regulation thickness glazing. Still a load more detailing but the point of this exercise was to get a good assessment of the shell weight for the design approval calcs.

Cool (and very ambitious) looking project you have going. To save a ton of time on making the shell, have you considered buying a shell from DDR Motorsport?

https://ddrmotorsport.com/

It has a very similar McLaren F1 look that you are going for. While not cheap, the time needed to make something similar yourself from scratch would be very daunting.

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Photo gallery of my completed Locost:
https://plus.google.com/photos/10397358 ... banner=pwa

Thanks! The DDR option is a very sensible suggestion. There is another guy here in NZ making a car called the FZ12, and that is what he has done. https://www.drivelife.co.nz/category/au ... -supercar/ . I am not as well funded as he is, so I currently have financial constraints rather than time constraints.

The bodywork is a huge task, and in NZ we are lucky to have a lot of companies who can CNC boat hulls on large routers, hence I wanted to have the surface models to make accurate plug moulds. Alternatively I have Slicer for Autodesk Fusion 360, which means it is very easy to produce accurate cnc cut sections for building the body master. I am intending to build the exoframe test mule first and then get some assistance to make a carbon fibre body once the chassis is proven to be mechanically reliable.

XP6 is born!



Keeping on plugging away at details...90% there only 90% to go!

The frunk volume is 4 cubic feet (approx 112l) - enough for soft luggage. The brake and clutch reservoirs are accessible behind a panel on the firewall.

Also working through the final checklist on legal requirements for road certification - hence things like the front indicators have now been modelled using Hella 2168 units. All the signal lighting will be modern LED type

Working through the finer points of the local seatbelt anchorage regulations. The seatbelt lug points will penetrate the interior panelling, shown as cutouts in the carbon fibre tub below, therefore attaching the seatbelts directly to the 4130 steel spaceframe. The rule is each lug has to be at the intersection point of a minimum of 2 tubes. Lots of iterations involved in getting those in place efficiently.

To make certification for the road as easy as possible I have followed the well troden path of a steel spaceframe with lightweight (i.e thin and non structural) carbon fibre diapraghm panels, such as the tub component. However these panels will boost the chassis stiffness, but they are mainly there as bling and to stop my legs poking out of the gaps in the frame.

Final fuel tank sizing will be 60L, good enough for a crusing range of 500km and maybe 100km of "enthusiastic" driving. There is space for an optional pair of auxilary long range tanks which could comfortably take capacity up to 90L. The certifier demanded a flanged design with lots of internal baffling and that the tank be retained by strapping, so best option is from 1.6mm thick aluminium sheet.

The Center of Mass only shifts a few mm with fuel load and passengers, going into the detail analysis has made me appreciate how clever the original design is.


From this angle you can see the passenger shoulder retractor slots clearly.

The brake and clutch pedals are going to be custom made with a pedal ratio of between 6-7 and using Tilton remote reservoir & 75 series master cylinders in a dual circuit layout with a tilton balance bar assembly allowing f/r balance once track testing starts. The reservior is positioned higher than all the caliper bleed nipples.

Time was right to kick the project along with a major milestone - have bought a 2016 C7 Z06 MEK trans and diff. The torque limit is 860nm which will see me through for a majority of the future engine combos. Unit apparently has 10k miles on it so should be reliable for the length of the project, even with the beatings it will get subjected too.

Weight distribution of the car is at 45F/55R - by nature of their transverse position both engine bellshousings nestle in nicely to the transmission front mounting plate. I needed a real sample to reverse engineer from so that the CAD models could be completed and I can get onto casting all the critical parts this year. Photos and internet info are not good enough for this task.

These units have an electronically controlled differential that can change from open condition to locked (0 to 100%) in 150 ms (.15 sec) . The diff when locked up to 100% corresponds to 2000 Newton-meters (1475 ft-lbs) of break-away torque (every 1% is 20 Nm (14.75 ft-lbs)). So at full lock it would take 2000 Nm of torque between the wheels to make the clutches slip. For reference a C6 Corvette mechanical differential clutch pack has around 120 Nm (88 ft-lbs).

Being able to tune the open setting on corner entry allows easy influence of the rate of yaw – what GM term Yaw Damping. Given how centralised the masses are the low polar moment of inertia could take a bit of getting used too – during the initial testing the diff can be set higher to give less snappy and responsive turn in – it will have tunable understeer. The advantage is a few laps later you can tweak the setting from the drivers seat to what feels best.

When heavily on the throttle, the diff can lock up more and shift torque from the inside wheel to the outside wheel. This has the combined effect of minimizing or eliminating inside wheel spin, but it also controls how much it feels like the car turns with the throttle.

Here is a cutaway showing the diff internals, the hydraulic pump on the left pressurizes a piston that clamps the clutch plates - no springs required.

Thank you for posting and explaining things like this C7 diff... bits like this are miles beyond what I'm doing with my builds and quite frankly way beyond my knowledge base; it's cool to see the higher-tech stuff being integrated in someone else's build

--ccrunner

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Dean

1972 Honda N600 Restomod "ccrunner's N600 VFR800 repower"

1963 Volvo P1800 Restomod
http://locostusa.com/forums/viewtopic.php?f=36&t=16309

1959 Berkeley SE492 Restomod...
viewtopic.php?f=36&t=19397

"ccrunner's 1960 MGA coupe Restomod" found on MGExp.com

That double bolted joint design is nice. My complements to you!
How will you fabricate it?

Thanks for the feedback guys.

That joint will be CNC cut from either bar stock or a 3D printed blank (which will have a machining allowance included so the final accurate dimensions are achieved). I am fortunate that we have a 40 ton tensile testing machine here at the foundry where I work so later this year will make some samples to compare with my CAD FEA predictions and hand calcs. I do not want the powerpack separating from the car due to fatigue failure at 200 mph years from now, so everything is quite robust where the loads are concentrated to keep stresses below the infinite fatigue life values. The tubing welded to these parts has multiple gussets to spread the load over the converging tubes - one side of each joint has at least 4 tubes connected to it.

Cheers,
Marcus.

This is my first experience with Docol as well. It’s a Swedish product so I suppose it may be hard to get over there? AED Motorsports sells it here. It’s weldable but they recommend using ER 70 or 80 electrodes which limits the strength of the weld to 70 or 80 ksi (about 500 mpa). Most Docol steels are stronger than that (100,000 psi or 700 mpa) so your welds may dictate the strength of the part. Consider fatigue as well. It’s expensive!

how will u connect 2 engine to gear box input?

Picture is worth a thousand words, hopefully this gives you the idea.
The leftside clutch is not shown for clarity.

Just for historical context twin engines can work VERY well. In 1937-1939 George Eyston set land speed records with "Thunderbolt" on the Bonneville Salt flats. He used 2 x 36.5L supercharged Rolls Royce R V12's - putting out 2,350 HP each! Mine is only a roadcar so don't need that much power - 540 - 600 is plenty. Its the 688NM of torque that will be fun to use.

The gearbox alone weighed 1 ton, the whole car ended up at 6 tons after some refinement.

you make your own transfer box or any product on market can use?