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Lotus E21 construction report part 25

Brake ducts, wheel hubs, cockpit padding, start designing engine cover and internal aero devices.

The brake ducts/drums are pretty complex shapes, but were fun to build. They are, even if they are 2013s, actually not less complicated than 2017 brake ducts. The packaging of the whole brake ventilation stuff is impressively thight (as almost everything is on this car – but not that extreme as the 2014 upwards car generation). The rear drums feature a row of little wings to generate downforce directly at the wheel. The front ducts only feature a few vanes.

The wheel hubs are relatively simple shapes, but each consisting of 16 parts. Front and rears are almost identical.

One of the most complicated things to design and manufacture is the cockpit padding. In real-life, it is filled with a foam. My one includes a structure inside and is covered by black paper. The difficulty here is, that the cockpit opening is not to 100 per cent exact (means also not 100 per cent symmetric). So I had to design the padding not to the exact original measurements but to the model’s shape – finally it is slightly asymmetric, but it fits pretty well.

Probably the most complex part on the entire car is the engine cover. Same as the cockpit padding, its shape has to be designed to the already existing bodywork on the model. Surprisingly the first design was already pretty good. Just two prototypes had to be designed till the right shape was found.

Remaining to-do’s:

  • Finishing rain light
  • Wheel nuts
  • Wheels
  • PDRS
  • Engine cover
  • Internal aero

I don’t like to place another completely wrong estimated date of completion – like I’ve done in the previous post. 😂


Lotus E21 construction report part 24

Brakes, safety belts, cockpit electronics, starting cockpit padding,  brake ducts and rain light.

And again two and a half moth flew by since the last post. This time again some bits are fitted to the car and the to-do list gets shorter and shorter. The completion of the car comes closer and closer. An expected finish could be at earliest by the end of April.

Remaining to-do’s:

  • Finishing cockpit padding
  • Finshing brake ducts
  • Finishing rain light
  • Finishing wheel hubs
  • Wheel nuts
  • Wheels
  • PDRS
  • Engine cover
  • Internal aero

The first five bits on the list are a work of maybe two weeks. The car is looking more and more attractive from day to day. But to increase the suspens till the “roll” out (maybe better move out), there won’t be any picture of the ful car any more. Just on details. 🙂


Brakes with first parts of the brake ducts. There were some thougts to make the brake ducts/covers demountable (and therefore detail out the whole brake duct stuff). But that may cause the wheels groggy when mounted…


Finally all cockpit electronics done. I am not sure at all, if this looks like the real car. But I incorporated all electronic stuff a F1 car has into the car. So there wasn’t actually much left for the cockpit. So it looks maybe a bit empty. Anyhow, it does look not too bad.


Cockpit padding in its current stage.


Original drawing of the rain light. Thanks a lot to McLaren Electronic Systems to provide this data for free! Original link is below.

Lotus E21 construction report part 22

Brake fluid reservoirs, exhaust pipes, fire extinguisher, radiator pipes, beer and more…

Nice progress over the last days. There’s not a lot missing any more. Main sites are front suspension, brakes, brake ducts, wheels and engine cover.

When I come to the end of a car build, I usually create a to do list with all the stuff on which is left. On this list I rate all elements with

+ which means, it’s an easy, quick and nice, simple to build element

~ which means, it’s a pretty simple element, but takes it’s time and is not that nice to manufacture

– which means, it takes a lot of time to build the element

Front suspension, cockpit padding and engine cover are the last three minus elements (maybe also the rims).

The components and assemblies, I produced during the last few days are stuff like exhaust end pipes (with their helmholtz resonater – more on that in picture caption below), fire extinguisher, brake bias lever, dashboard, roll sensor, brake fluid reservoirs, pitot tube and some electronic stuff at the front end of the chassis.

Beside all this, I created a rim instruction. So the rim design is already done.

Unfortunately I lost the drive shafts during the summer… 😦 So light delay at the rear suspension build.

At the moment, the car is at about 4000 parts.


Front view of the steering wheel – it consists of 107 single parts and has a diameter of 27mm. For comparison, the RB7’s wheel has 73 parts and the R18TDI’s wheel (much bigger) has 109 parts.


Back view of the steering wheel with clutch and gear shift paddles. At the best sake, I can’t remember any more, what the top lever is. It seems, I got a little rusty… With the ruler beside, you can actually imagine the size of all these tiny elements.


A view into the chassis with removed seat and steering wheel. At the bottom, you can see the fire extinguisher, right handed the fire extinguisher switch as well as the ignition switch are mounted. At the left hand side, the brake bias lever is mounted.


Just the seat straps are missing – but it’s actually hard to find suitable straps with the right colours and fabric.


That are the raw exhaust pipes. They consist of a steel wire inside and a thick paper cover (many cylindrical layers). Before painting, the whole structure is covered with a thin layer of glue and sanded down to get a clean surface. The pipe which is sticked on the actual pipe is the helmholtz resonator. It simply provides a steady exhaust gas flow to get a nice blown floor. For an exact description of the effect, just google. It’s basically pretty simple.


The right hand exhaust pipe during the painting process. The left and the right pipes are a little different due to the different space conditions in the side pods (oil radiator right handed, water radiator left handed). The paint jig (beer crate and a steel wire) is a bit unorthodox, but it’s simple and it works. 🙂


The right hand exhaust pipe in the side pod. It’s not fixed yet, as the lacquer is still curing. But somehow in this position it will be later on. The packaging of these cars was already quite tight, but not really comparable to the current generation of hybridcars.


The left hand side pod without its exhaust pipe. But the feeding lines for the water radiator are fitted.


Something is going on at the front of the chassis. It’s fully packed with brake fluid reservoirs, some gauge instruments and some electronics. Clearly visible, the pitot tube (air speed) at the top and the roll sensor at the bottom.


That’s the roll sensor, nicely shaped.


To get an imagination on the size of all these  elements… Note also, there’s a 1 € Cent coin (diameter 16.25mm) lying on the chassis.


To do list


Rim instruction – all these parts are needed to produce a rim.

Lotus E21 construction report part 21

More to come in the next weeks…

Design start of cockpit internals, fitting radiators and finishing rear suspension components.

As uni stuff (exams) is coming to an end slowly, I’ve a bit more time left now and car progress will speed a bit up during the next time.

Over the last few weeks, I’ve done quite a lot of (more or less) small detail work on the car. First of all, I’ve found a suitable grid for protecting my radiators (metal grid with about 1mm mesh size). After fitting this to the rad ducts, I was finally able to fix the radiators to the car. A bit of detail work is still missing there, i.e. proper sealing, pipes, etc..

The next building site was the finishing of all the rear suspension components with clear lacquer. As I don’t have a proper paint shop (room), I had to wait for acceptable outside temperatures for lacquering on our balcony.

Next point are the cockpit internals. As I have to wait a lot during finishing and mounting the rear suspension, I need a site where I can build at and not touching the car a lot. So seat is more ore less done (picture series below), steering wheel (picture series below) is well on the way and some small bits such as “dashboard” (that’s the tiny bit at the drivers right hand side with fire extinguisher and ignition button on it) or belts are missing.

There’s not too much stuff missing at the car now. Front suspension, brakes, wheels and engine cover. Nevertheless, I expect finishing the car not before middle of autumn – maybe October.


Rh rad duct with fitted grid. Same proceedure at the lh side pod.


Rh side pod viewed from the front. The cooling duct for the electronics is outside of the grid. You can see it a bit at the lower face of the duct directly in front of the grid.


Rh side pod with fitted radiator. It will be a challenge to get the cooling pipes packed beside the exhaust system. There I made a little mistake. If you can call it a mistake… The exhaust manifold should be tilted a bit more outside the car. In my case, it almost touches the chassis. So there is very less space for the backflow pipe of the oil (rh) as well as of the water (lh) radiator. But I’ll find a proper solution to manage this little fail.


Rear suspesion stuff and barge boards finished (8 shiny lacquer coats for the barge boards, 5 mat for the suspension arms).


Here you can see my “seat shell tool” which I’ve designed entirely from 2d shapes. Beside, you can see the basic structural element of the seat shell in raw condition.


First, I layed up the basic structural element (which could be seen at the picture above), followed by two side and one central element.


Top view of the structural part of the seat in my seat tool.


Seat demoulded from its tool. At the sides it needs to be trimmed.


First fit of the raw seat shell.


Final fit of the raw seat shell with stiffening boudaries (red stripes).


Finished seat shell.


Back view of the finished seat shell.


Raw structural (base) element of the steering wheel – front view.


Raw structural (base) element of the steering wheel – back view.


Steering wheel base in the paint shop – or, as we have learned earlier, on the paint balcony. 😉


Placing buttons on the steering wheel.


Comparison between the Lotus E21 and the Red Bull RB7 steering wheel. The Lotus one looks a bit more bulky as it has the display on the wheel and not on the chassis. The team appraoches differs in this regard. RB7 steering wheel has 73 part (as far as I remember), the Lotus one has 60 parts in its current stage (shift paddles and some details are missing).


Rh cockpit side: emercency sticker, E21 chassis badge and some lines – I don’t like to describe all the lines (all electronics).


Lh cockpit side: FIA sticker, track sticker (guess, which one is it?) and again some lines (two hydraulics for brake and FRIC-S and some electronics).


Cockpit view

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 – 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

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