Lotus E21 construction report part 20

Summary report of December, January, February

Design start of front and rear suspension, manufacturing rear suspension and barge boards.

In December I started designing the front and rear suspension. Designing the suspension is one process, to get the suspension properly onto the car is a different step… The design of the suspension is based on the chassis/gearbox mounting points and the wheel position. The manufacturing of the rear suspension is almost done, just the pullrod is missing. The positioning of the upright relative to the chassis is one of the most essential points in the building process as it defines the position of the car above the ground in finished stage. For this reason I did a jig to position the upright correctly and connect it via the suspension arms with the chassis.

Also the barge boards are already manufactured and are awaiting the lacquering process (as well as all the suspension elements).


Front suspension layout: castor 3.5°, negative anti dive, king-pin inclination 8.5°, camber ~4°, track 146mm, minimal toe in, car inclination >1°. Some of the values are just guessed or given by wheel and upright geometry.


Rear suspension layout: king-pin inclination 19°, camber <0.5°, track 142mm, minimal toe out, static drive shaft inclination ~7°.


Rear upright structures beside the drawing. This structure is built from 0.5mm cornflakes card and later covered by 0.3mm silver card. Stiffness of the uprights is the essential property.


The finished lh rear upright (25.3mm x 19.5mm x 5.7mm).


Rear top wishbone – note the different fibre directions and weave styles.


Rear bottom wishbone – also note the different weave styles. The safety rope to stop the tyre from firing away from the car in case of an accident is placed in the backward arm and covered by a carbon cover (that’s the area with the different weave style).


All rear suspension parts (pullrod is missing) are waiting for getting lacquered.


The rear suspension in an early stage. At the top WB the structure can be seen, at the lower one, the metal wire can be seen which stiffens up the whole thing.


Rear suspension in a late state.


Jig to position the rear upright.


Barge boards.



About paulsf1

My name is Paul Bischof. I’m a student in mechanical engineering at the Technical University of Graz in Austria, expected finishing in February 2016. Since I was eight years old, I am building model planes out of paperboard. Since 2004 I scratch (that means building without an assembling set) Formula 1 and sportscars in 1:10th scale. The average time I need for such a car is around 400 to 700 hours within 4 to 8 months. One car has around 3500 up to 5000 single components. On this blog, you can take a look on my work and later, after my studies, hopefully you can see me in Formula 1.

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