I think this is a really neat group of old cars from a time when design was moving very quickly. Hope you all enjoy them! Here are a few notes from the development. If you have any questions about them, ask below and I'll do my best to answer.
Lotus 51
Neat car here. It was a case of Lotus updating an older design to create what was the birth of Formula Ford racing as we know it. The engine is a 1.6L Ford Kent crossflow from a Cortina good for about 115hp @ 6500rpm. Very smooth and plenty of power for a car that weighs less than 900lb empty. Gearbox has a full range of Hewland Mk8 ratios to choose from; it was standard gear for the car after moving away from the (unreliable) Renault Gordini unit. Our reference car was laser scanned so the suspension geometry is new using the points that gave us. Surprising amount of pro-dive at the front, but it is otherwise quite similar to the Type 25 and works very nicely. Set it to use the same tire options as the Lotus 25. This was a beginner Formula Ford car from '67 and I think it is fair to assume that the tire tech available would have been equivalent to what went on F1 cars a few years earlier. It is not super sensitive to having great rubber anyway. 115hp doesn't tax the rubber, plus the chassis is so light and balanced that they barely have to work at all to put in fast times. Lovely (easy) car to drive and should make for some fun MP racing.
Motion Ratio:
Front= 0.67
Rear= 0.76
Damper Transitions: 500mm/s all around
Lotus 25
It's like a baby Lotus 49 - less weight, tire, and engine - and much better for it. There is good data available on the 1.5L Climax V8 and it is a peach. 200hp with a very smooth torque curve all the way from 6500rpm up to the limit at 10500. Not at all like the later DFV that hits you like a second engine turns on when over 7500rpm. It even made good mileage! averaging around 23L/100km at Monza. Very cool little engine for the time. Aerodynamics are typical early-60s stuff, with aero lift at speed but a low drag number thanks to tidy engine packaging. Expect top speeds up over 150mph when the track lets it run long enough. Gear ratio selection is from the original ZF 5DS10, which is to say somewhat limited. It wasn't the greatest unit and it's no surprise that restorations typically switch to a Hewland box. Doesn't work against you too much, though, as the Climax engine is happy at relatively low rpm and excessive shifting is unecessary. Suspension design is another fun look into very aged car design. It does most everything in a nice way, but uses high camber gain as a key design element - note the large angles on front top wishbone and rear top link. Means the car is plenty happy running right near 0° camber as it leans them into the turns under chassis roll. It does work quite well for cornering balance in testing here, but isn't lovely under braking and over bumpy sections. The large changes in roll center with suspension movement aren't highly desirable as roll balance can become out of sync front to rear. Both our Vintage Open Wheel 1962 and 1965 tires are available to use, with 1965 being the default. Redesigned the tire carcass and tread to a more convincing feel. They give a great view of how tires were developing over the life of the car, as the brands progressively experimented with softer and softer rubber. Tons of fun, whichever tire you choose.
Motion Ratio:
Front= 0.63
Rear=0.81
Damper Transitions: 500mm/s all around
Lotus 38
The 4.195L Ford Quad Cam is good for just under 500hp @ 8800rpm and is buttery smooth. Ford’s Cosworth DFV gets all the attention, but for the time this engine was every bit as impressive. It won just about everything from 1963-71, including 6 Indy 500s over 7 years plus one more in turbo form in 1977. Power goes through a ZF 2DS-20. Yes! that's a 2-speed version of the 5DS-20 that was common in other forms of racing. It's a very different feeling, but you won't really miss the gears because the engine provides good torque even down low. Means a little more work getting the right gears for each track, but you've only got two to worry about. A new rule in 1965 meant that 2 pit stops were required over the 500 miles, so fuel capacity was reduced to just 60 gallons. Tires could last the whole race.
The monocoque chassis has a lot in common with the Lotus 25, except it is shifted about 3.5cm left of center. This puts the lateral weight balance at about 52% left and means the suspension geometry is asymmetric. All points for that were taken from our scanned model. It doesn't ruin the car for turning right, but it does lead to some unusual behavior in how it puts down power and it does handle slightly differently in left vs. right turns. In general, it handles beautifully so long as you treat it with respect. There is a lot of power on tap.
Made a new tire for it from the Vintage Open Wheel base plus the new heat model ideas I've been working on for other cars. It's different enough from the F1 cars that this is needed, and Firestone did make something new specifically for this car.
Surprisingly, I’m turning low/mid 7-minute laps around the Nurburgring with it. It's really not that far off the Lotus 49 despite being a bit heavier and down 3 gears. Very good fun at historic Silverstone.
Motion Ratio:
Front= 0.6 (left), 0.7 (right)
Rear= 0.9 (left), 0.8 (right)
Damper Transitions: 500mm/s all around
Lotus 49C
There weren't huge changes from the 49 to 49C. Subtle changes to the suspension, monocoque, and wheelbase made the base package more refined. Cosworth worked on the DFV so it would run a higher rpm good for 430hp; the 1967 version could get that output at 10000rpm, but only for a couple of seconds before detonating. The big change, of course, was the addition of wings as aero was starting to be figured out. One of my books mentioned this particular aero package being good for around 450lbf downforce while cutting top speed to ~175mph, so that is what we've matched. Gearbox changed from a ZF to Hewland and the much wider range of ratios that comes with it.
Motion Ratio:
Front= 0.9
Rear= 0.9
Damper Transitions: 500mm/s all around
Lotus 40
This turned out to be a surprisingly cool car. Famous driver quote about it was ‘...Lotus 30 with 10 more mistakes’ but it’s actually a lot of fun to drive! Not exactly a perfect balance of chassis, engine, and tire, but it makes for an engaging drive. This was a classic case of taking a light car and finding some way to shove a big engine in it. Proper hot rod stuff, but in a sports prototype kind of thing. Suspension geometry could mostly be pulled from the scanned model. Tires are shared with the Ford Mk.IV. Set it to use a Hewland FG500 4-speed gearbox. Engine is a Ford 289c.i. V8 good for about 380hp at 7000rpm. Kinda like a race-spec version of what's in our '66 Mustang. These Type 30/40s ran any number of combinations for engine and gearbox, but this seems to give a good representation of how most of them ran early in life. Overall it's a good match for the Ford Mk.IV. Sharper handling, but down on top speed.
Motion Ratio:
Front= 0.6
Rear= 0.77
Damper Transitions: 150mm/s all around
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