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.


Lotus E21 construction report part 19

Slowest progress ever…

Redesign of cooling ducts, finishing airbox, starting with electronics design and fitting process of the radiators.

There was a little progress over the summer since the last post. My intended finishing date for the car was something about in spring 2017, but with the current progress rate it could move into the summer. 🙂 But one after the other:

  1. I finished the redesign of the side pod cooling ducts. I did a design, when I built the monocoque back in autumn ’13, but in spring this year they proved to have a wrong size and position to fit the radiators (collisions with floor and exhaust end pipe). So, after the redesign they look fine, but it’s still a huge challenge to manage this tight packaging. I see more problems coming when designing the engine cover. 🙂
  2. Quick note on the airbox: All done, lacquered, fitted and sealed. No problems at all.
  3. A few weeks ago, I started with the electronics design. The electronics are fitted in the side pods each below the radiators, below the drivers seat and at the front of the monocoque. The rh side pod is already filled up with just missing out the cooling duct for one of the boxes. Btw – all electronics data are free available at mclarenelectronics.com – thanks MES for that!
  4. At the mo, I’m fighting to get the radiators properly fitted to the ducts.
side pod lh

Lh side pod duct – this duct houses the water radiator and the gearbox oil radiator. The gills in the side pod top face helps to get the hot air away from the radiator.

side pod duct rh

RH side pod duct – this duct houses the engine oil and the ERS radiator. At the very front of the duct you can see another duct which taps off a bit of air to cool the electronics that are housed below the duct. The big duct at the end of the main duct is for the ERS radiator. This will be better visible in a picture below.


Here you can see the finished radiators. At the front – engine water and gearbox oil, at the back – engine oil.

side pod

LH side pod with fitted radiators. You can see very good, how close the exhaust manifold is positioned to the cooler.

side pod rh

RH side pod with fitted radiator. Still a collision of the drain pipe and the exhaust manifold…


Top view of the car with fitted radiators. Against this view looks like, the radiators do not overhang the floor (which exploits the maximum width of 140mm). With fitted engine cover, the width should be 138mm.


Airbox is waiting for getting lacquered…


Airbox is waiting again – this time for getting fitted to the car.


Nothing to wait any more for the airbox. Fitted to the car and sealed off.


The electronics in the RH side pod. Also the ERS radiator sitting behind the electronic boxes is well visible. I could start to explain which box is what, but that would be too much I guess. Also notice all the live locks to fit the engine cover. Zoom in for details…

Lotus E21 construction report part 18

End of “creative break”

Finishing rear wing and start of of internal duct design. Furthermore – finishing my Bachelor degree.

As my Facebook followers might have noticed, I had something like a creative break on building my Lotus. Main reason for this is to find on uni. As I was finishing my BSc degree in Mechanical Engineering and starting my Master studies, there was a lot of stuff to execute. I guess, now in the summer month, there should be much more progress on the car than during the past few month.

Two days ago, I restarted working on my E21. The last few bits I did on the car was assembling, painting and fitting the rear wing to the car.

After removing the existing side pod cooling ducts due to non-compatible size of themselves (a design error), I started to design new one with all the given circumstances. The left cooling duct houses the water and gearbox-oil radiator, the left one engine-oil and ERS radiator. I’m still not completely sure, where the hydraulics cooler sits. Probably at the top of the monocoque below the airbox. As you will see in the pictures below, it’s a tough challenge to achieve the extremely tight packaging, especially in the area around the exhaust system and the radiators.

The airbox is a bit more complex than the previous airboxes I’ve built so far, but the design process didn’t showed any big problems.

Next things on the to-do list are finishing these ducts, than design and build all the electronics sitting in the side pods (ECU, PCU,…) and the PDRS ductings. Now let’s take a look onto the car.

Rear Wing

Assembled rear wing, DRS and central stay are missing. To keep in mind, the fully assembled rear wing consists of 120 parts – actually not a lot if you compare it with the 100+ parts of a steering wheel. 😀

Car rear view

Car rear view with fitted rear wing.  The wing is mounted via a stay on each endplate onto the top floor surface and a central support, connected to the rear crash structure. Notice the nice monkey wing, which will support the PDRS second pipe later on.

Rear Wing fixing point floor

That’s the rh rear wing end plate fixing point. These points are mainly to balance the wing. Most of the load goes thru the central stay which you can see on the next pic.

Rear Wing central fixing point

The rear wing central fixing point is mounted on the rear crash (which is naturally very stiff). With the ban of the beam wings in 2014 (which is a bit of a weird regulation change in my opinion), the central support is replaced by a big stay, connecting the top of the gearbox with the main rw flap (you can see this an all current cars).

Rear Wing DRS

The rear wing flaps with DRS. Also notice the slats in the RWEP. That was a tough challenge to get them reasonably good looking. The wing is a bit dusty – I should clean the car.

Rear Wing strakes

RWEP with its remarkable mini strakes.

Cooling duct left

Lh side cooling duct for the water and gearbox-oil radiator. You can see how challenging it is to achieve such a tight packaging. The exhaust system lies just above the radiators.

Cooling duct right

Lh side cooling duct for the engine-oil and ERS radiators. The ERS radiator will be mounted on the lower end of the duct where you can see the small slot.


The airbox with its jig.


Airbox fitted to the car.

Car top view

Car top view

Lotus E21 construction report part 17

Interim Report:
Something about Rear Crash Structure, ERS Battery, Exhaust System and Rear Wing

Pretty long time went on since my last post. Some work on uni, some work in Formula Student and a move into a new flat prohibited me working a lot on the Lotus. Nevertheless there are some news since the last report.

Where should I start? Probably it’s worth mentioning at the beginning that the gearbox is now finally fitted to the engine. This comes along with the finishing of the hydraulics pump/hydraulics system which sits on the right hand side of the engine beside/behind the oil pump.

After fitting the gearbox to the engine, I started working on the rear crash structure. Nothing very impressive or interessting to tell about it. With the fit of the rear crash to the gearbox, the car reached its full lenght of 507mm. It should actually be 508mm long, but one mm is within the acceptable tolerance (indeed it’s less than 0.2% deviation). Of course the rear crash structure is hollow to allow the fit of a working rear light. 🙂

Another work which was done within the last two month is the production and fit of the ERS-battery. Although the battery isn’t visible on the finished car, I produced a simple battery model, just as a “nice to have item”.

Next point on my (still endless long) to-do-list was the manufacturing of the exhaust manifold. Always a very demanding and not really liked work. For the first time in my modelling career, I produced an exhaust system, lacquered with a chrome spray. And it looks convincing. The system is already fitted on the car. And the packaging is stunning. I had quite a few problems to make the underbody fit to the car with the mounted exhaust manifolds.

Subsequently I started working on the rear wing. End plates and flaps are finished, DRS and beam wing are still under construction.

There are also some bad news. I had to grind off the whole cooling ducts in the side pods as they were too wide at the bottom. Coming along with this, my radiators are also worthless and need to be redesigned. Luckily radiators are not very demanding to design and build.

The car currently has about 3100 parts. About expected 2500 more to come.

Rear Crash Structure

Finished rear crash structure.

Gear Box with Rear Crash

Rear crash structure fitted to the gear box.

ERS Battery

ERS battery installed to the car. The battery will disappear after fitting the underbody.

Exhaust Manifolds unpainted

The raw and unpainted exhaust manifolds. Each pipe consists out of a steel wire as the core element wrapped with some layers of paper.

Exhaust Manifolds painted

Painting process of the rh exhaust manifolds.

Exhaust Manifold

The finished rh side exhaust manifold.

Car from felow

The engine area from below with fitted exhaust manifolds.

RH Exhaust Manifold

Rh side exhaust manifold.

LH Exhaust Manifold

Lh side exhaust manifold. There is a heat shield clearly visible to protect the power steering hydraulic line.


The underbody is waiting for getting fitted to the car.

Exhaust Manifold fitted

The lh side exhaust manifold with the fitted underbody. The packaging is extremely neat.

RWEP internal Structure

The RWEP internal structure. It’s a bit more complex as it looks from the outside. Each endplate consists from almost 40 parts.


RWEP vanes.


The rear wing in its current state.

Cooling Ducts

The destroyed cooling ducts…

At the end a nice video of the first try to fit the underbody to the chassis.


Lotus E21 construction report part 16

Finishing Underbody and Coanda Exhaust

Finally, the underbody is finished. What happened since the last post? Beside manufacturing the Coanda exhausts, where I used a colour spray lacquer (chrome) for the first time, I added loads and loads of small features to the floor. That means stuff like skid blocks, heat shields, IR cam housings, tyre vanes, diffuser strakes, diffuser gurney, live locks, some sponsor/partner labels, reinforcement stuff, bolts, skid planks or CFRP textures.

As I mentioned, I introduced some new techniques, namely the chrome spray lacquer for the Coanda exhaust groove for example. After it initially worked flawless, it happened that I run a bit into trouble when applying the final layer of clear lacquer. On the chrome can it says, it’s not compatible with clear lacquer, but I thought, clear lacquer will just run off the chrome surface. Instead, it dissolved most of the chrome…

Another new technique was, to use a special glue for applying big-surfaced CFRP areas. Previously, if I bonded on the CFRP texture (90g/m² paper) with my usual glue, it happened that the paper started to dent. The new glue is much less aggressive and does not show this properties.

Enough blathered, here are some pics of 448 glued paper snippets:

Floor Structure

That’s the floor structure shortly before getting “carbon fibred”. The white stuff you can see is mainly some reinforcement structure. I tried to rebuild the structures as true to the original as possible. Some of the white stuff at the front is also just a 3d radius.

Coanda Exhaust Painting

That’s my first try with coloured lacquer. To paint the Coanda exhaust grooves with chrome seemed to be a good idea. It looked great as you can see in the next picture. But unfortunately the chrome lacquer and the final clear lacquer aren’t good friends…

Coanda Exhaust Panel

The Coanda exhaust panel after painting. The chrome is pretty soft, so you can see my finger print at the end of the Coanda groove. I did a little bit of a hardness/dryness test.

Floor Stay

The famous Lotus floor stay. Wonderful shape! Teams racked their brains to find out, why the Lotus stay was shaped like this. It stayed just for the 2013 season in this configuration.

Floor Front Corner

The floor front corner with its weird shape. The strange bulge coming from the inside of the car houses the lower crash elements.

Blown Starter Hole Intake

The blown starter hole air intake below the Coanda exhaust. Red Bull introduced this idea already in 2012. Lotus and Caterham followed in 2013.

Coanda Exhaust Panel Inside

The Coanda exhaust panel from the inside. Not very spectacular, but you  can see the port for the exhaust manifold, the whole heat shielding and some live locks (i.e. kind of bolts) to fix the surrounding bodywork.

Tyre Vanes

The tyre vanes which help to lead the exhaust plume towards the gap between the tyres and the floor. You can also see the IR sensor housing (outside of the main tyre vane) which looks at the rear tyre to log their temperature development.

Floor Rear

The rear of the floor with the diffuser. Very good visible is the diffuser gurney which helps to prevent a stall on the diffuser underside. With the new restriction of the diffuser height mid of 2011, teams switched from the classic diffuser gurney to a slotted gurney which is more like a little wing at the top of the diffuser. Another tweak to handle the new diffuser height restriction of 125mm (it’s actually not new any more in 2013/14), was to expand more in width. So, the diffuser rise starts with a width of just about 700mm and expands to the rear to the full 1000mm (or slightly below).


The diffuser viewed from the rear. That’s a very good view to see why it’s called “slotted gurney”. It’s not actually a gurney, but a little wing with a gap to the top surface of the diffuser. Often this wing is also provided with a little gurney itself.

Floor Underside

The Underbody from below. You can see all the fixing bolts where the floor is fixed to the chassis and the engine. Notice the different wear of the three skid block pieces.

Skid Block Front

As already visible at the top picture, the Skid Block is splitted in three pieces (permitted by the regulations). This shows the front piece which is fitted to the T-Tray and is therefore the element which mostly slides on the track.


A good view on the important heat shields which prevent floor damage due to hot exhaust gases. The shedding edge you can see is the area, where the exhaust plume enters the floors underside. Also notice the different CFRP structures at the diffuser.


The car in current state. Still no end in sight, but slowly you can imagine whereabouts this project will lead…

2014 in review

The WordPress.com stats helper monkeys prepared a 2014 annual report for my blog.

A special year ends for me. The obvious highlight was working at Red Bull Technology, a lifetime dream got true! This experience ended up in our special vid which was produced by Siemens in cooperation with RBT. Click here to watch. In meantime I am back on uni finishing my studies in MechEng before returning to Formula 1.

In terms of building my paper cars, it was a bit more quiet than the years before. There was some progress on my Lotus, however I’m working now over 16 month on this car. The famous RB7 took me just 12 month. But there’s some light at the end of the tunnel: I expect to finish the E21 in summer.

Last but not least, my FB page has now more followers than my native village has inhabitants (that’s actually not that difficult, as we have just a bit less than 1300 inhabitants 😀 ).

Anyway, I want to greet all of my fans with this and wish you a happy new year and you’ll read from me in 2015.

Cheers, Paul!


Here’s an excerpt:

The Louvre Museum has 8.5 million visitors per year. This blog was viewed about 180,000 times in 2014. If it were an exhibit at the Louvre Museum, it would take about 8 days for that many people to see it.

Click here to see the complete report.

Lotus E21 construction report part 15

Underbody Manufacturing

With the underbody, I’m working now on (one of) the most important aerodynamic feature(s) of my Lotus. The underbody produces about 30% of the cars (negative) lift, but just a little fraction of its drag. The side of the floor is sealed by vortices, created by the barge boards at the leading edge of the floor.

Special features on the Lotus floor are the Coanda-exhaust sealed diffuser and the blown starter hole.

The Coanda exhaust, was the difference making aero feature in the seasons 2012 and 2013. The Coanda-effect describes the phenomenon of a fluid-flow, following a convex surface instead of separation of it and move along its original flow direction. In Formula 1, this effect was used, to lead the high-energy exhaust plume between the rear tyres and the floor to seal the diffuser. Some teams were able to control this tweak better than others. At the end of the 2013 season, Williams was faster by removing its Coanda system. The most effective systems were built probably by Red Bull and Lotus.

The blown starter hole is an aero tweak, to prevent flow separation at the middle area of the diffuser. There you take “good” air from the side of the car and lead it to the diffuser and exit it via the starter hole to re-energize the boundary layer. With the ban of the classic starter holes in 2014, some teams use vortex-generators to convert the air to a turbulent flow for preventing a stall.


The underbody in current state viewed from the top. You can see very good, how narrow the rear of the car is. The two ducts left and right are the ducts to blow the starter hole. Above this ducts, the exhaust will exit the bodywork in its Coanda-groove. More on this later.


Trailing edge of the diffuser. Because of the special shape, the rear of the underbody is a bit deformed due to internal stresses. But with adding another layer of paper (the top one), this should be solved…


The leading edge of the underbody. Weird stuff…


A better view on the blown starter hole ducts. You can clearly see how it works. There’s an awful lot of air coming from the side of the car. I expect just a very small percentage of this air effectively find its way thru the starter hole. The two cutouts/dents which you can see at the inside halfaway thru the duct are there for the pullrods.


Nice rear view where you can see very good the deformed sides. You also can see the exits of this two ducts, which are beside the gearbox later on the car. This ducts end about at the rear axle center line.

Barge Boards

The barge boards which produce the vortex at the leading edge of the floor. This are far the most comlex boards I’ve ever seen in F1. They consist from four airfoils with the last two ones splitted. Lotus used them just in the 2013 season. In 2014 they returned to a more conservative design.


Underbody pre-fitted to the car. You see the amazing packaging around the gearbox. Here you can see again the cutout for the pullrod. At the moment you can see the rocker there.


This will be a tough challenge to make the underbody fit perfectly to the car…

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