Fabrication: From CAD, to 3D Print, to Fibreglass

To trackday a car it needs a reasonable level of illumination, to communicate your intensions and make yourself more visible in low light conditions. Indicating left, pass me on the right. Hazards flashing, I’ve had a bad day. This is something the Locost has not needed until now, as it has only ever been driven on closed courses with only one car competing at a time.

I already own a set of rear light clusters that I bought almost six years ago when I was initially stockpiling parts. I decided to go with these “hamburger” style rear lights as they mirror the round headlights at the front of the car, that I am also yet to install, and also I could get them with clear LED’s which would keep the car aesthetically pleasing. It also helps that they weren’t cut-off-your-left-leg-and-right-arm expensive.

The easiest and quickest place to mount rear lights on a seven is directly to the rear bodywork. While this could have been done on a Saturday afternoon, with time for a few cups of tea in-between, it would have been almost irreversible and completely illegal for road use if I ever felt like going that way (lights must be a maximum of 100mm from the outer most bodywork). So this left me with only one option which was to mount them on the rear wings. Never one to turn away the opportunity to do something the hardway I decided this would be a great opportunity to make my own light pods, in my own asthetic style- fire up the 3d printer!

CAD

First of all, my printers build volume is a measly 150*150*150mm, and would have never been able to print an entire light pod in one go. Also, PLA plastic would have never been a good choice for components like this, given that they will sit in the sun for extended periods of time (damn you 60degC glass transition temperature). These would have had to have been printed in ABS. Printing thin walled ABS shapes is pretty much a no-go without some major warping, so this left me with only one option… a 3d printed mould.

I grew up around fibreglass in all its forms. Quick shabby make-a-mould-out-of-Tupperware fibreglass, and top quality a-thousand-layers-of-wax-and-lots-of-polish fibreglass; this was going to be something in the middle. Because of my limited build volume I opted to design the mould to split into four separate parts. This also meant that releasing the strangely shaped light pod would be relatively straightforward as long as everything was unbolted and persuaded a little; so it was win/win.

After measuring the curvature of the rear arches and the geometry of the lights I frew the mould itself and split it in the X and Y axis. This is a female representation of the lightpod, with the reverse being the actual “male” final piece. Getting a clean striation-free mould surfce was going to be unlikely, and comes with the territory when 3d printing, so I knew I was going to have to sand and polish the final mouldings after they were produced.

Light Pod Mould

3D Print

I believe these components took between 16 and 19 hours each to print in PLA, which goes to show how awesome my Printrbot Simple Metal is. I’m very happy with my printer setup at the moment, as it’s hugely reliable over a long period of time. Hold on, where’s your RepRap gone Josh? That’s a story for enough time…

Light Pod Complete Mould

The mould was sanded with 200 grit sand paper and given 5 layers of wax. The wax helped to fill in the crevasses between the separate mould pieces and massively helped the release after moulding. In short, this stuff rocks.

simonizwax

Fibreglass Mouldings

Once the mould itself was ready to use the mouldings were made in a fairly simple way. Firstly a layer of White Gel Coat was applied to the mould with a brush. Gel Coat is essentially resin with pigment in, which gives the moulding an outer layer which can be sanded and painted to achieve a nice finish. If the mould is of a high quality the Gel Coat can simply be left as is. I would eventually be painting these moulds so I wasn’t too bothered about the initial surface finish.

Light Pod Gel Coat

Once this had adequately hardened polyester resin was brushed into the back of the Gel Coat and 450gram fibreglass rolled into that (I gave it approximately 4 hours at 10degC, with a 3% mass fraction of catalyst to kick things into gear). The rolling process is important as it helps to remove air bubbles from the structural fibreglass and improves the strength of the composite. It also helps reduce the amount of resin you have to use, as the fibres are pushed tight against the Gel Coat and the resin soaked through. If the whole lot was just brushed on then it would have likely had a higher resin content and been heavier.

Light Pod Laid Up

This was left for two days to harden and then extracted from the mould. I’m very happy with the final product and its far lighter than I expected it to be. The ‘pods will be glued into the back of the arches and then faired in with filler. The whole lot will then be smoothed and painted; probably glossy battleship grey.

Light Pod A

Light Pod B

Light Pod C

Have you ever tried any Fibreglass work? If not, give it a go! Its actually ver y rewarding and if you take your time with each step you can achieve great results.

Locost: Baffled and Gated Sump

This is the first part in a series I like to call “What’s wrong with the Locost?” or WWWTL for short. I promised myself I would do a Trackday this year and as things are starting to slow down for the summer I now have time to prepare the car.

Firstly, the Locost is not perfect; I can easily stand and point my finger at a million things “wrong” with it and there are a few things I can’t really live with that I feel I need to amend before it starts turning laps.

You see, as you fix the fundamental setup issues on your home built race car, and attach a set of half decent sticky tyres, you’ll start to go around corners much faster. This has a big effect on the longevity of the car, increasing the loads through the suspension and engine, and you will definitely find some design flaws if you are lucky enough to have any. If you applied good engineering when designing/building said race car you will hopefully have no issues. You would have considered all loading conditions, and you will suffer no tears/breakdowns/failures.

Something I feel I did not consider enough many moons ago, and potentially completely overlooked, was oil starvation.

 

The Oiling System

I’ll do a short run through of the oil system in a combustion engine to give you a basic idea of what we are dealing with.

Firstly, oil lives in the sump pan. This is essentially a bucket of oil at the bottom of the engine which stores a supply of oil for the engine; this is directly under the rotating crank. Oil is sucked out of the sump by a crack driven pump and forced through an oil filter, which removes all the small particulates which might potentially cause damage upstream.

From the oil filter it feeds the main oil gallery which gives oil to the main bearings and crank, ensuring there is adequate lubrication and load support for the connecting rods. The main gallery also has a vertical feed going vertically towards the head. This lubricates the cam bearing surfaces and pressurizes the hydraulic lifters.

Oil slowly leaks out of the bearing surfaces, and flows back to the sump thanks to gravity. The restriction between the pump and atmosphere (the effective hole size in which the oil leaks out of) leads to a pressure build up in the oiling system. Once a given oil pressure is reached a blow-off valve allows oil to flow straight back into the sump, restricting how much oil pressure will be achieved. Therefore the less wear on an engine, the greater the restriction and the greater the running oil pressure (until the blow-off valve pressure, which is usually 60-70psi).

As an aside, when an engine is cold the oil is thick and viscous, and therefore the oil pressure is higher.

G13B Oil System

So, if for some reason the engine is starved of oil it will pump air and the oil density will drop, flowing easily through the gap in the bearings and reducing the oil pressure. Air does not lubricate or bear load very well, leading to excess wear and potential engine failure.

In short, oil pressure is an effective measure of engine health.

 

The Sump

So how does oil starvation occur? Well usually its one of three things, a lack of oil in the sump (check your dip-stick!), aerated oil or oil slosh away from the pickup. Keeping the sump full is easy, and really there is no excuse for having a low oil level, however the other two are not so obvious.

Oil aeration occurs when the crank stirs up the oil in the pan and fully/partially turns it into foam. This can be designed out with use of a Windage Tray; more on that later.

Oil slosh occurs due to the accelerations that are applied to the oil volume. If you achieve a lateral acceleration of 1g (at the apex of a corner for example), there will be a force pushing the oil against the side of the sump equal to gravity and it will set in triangular shape; as illustrated below:

Oil Slosh

In this case the pick-up is partially open to the air and pumps that as opposed to oil. This leads to bearing on bearing interaction, friction, wear and potential engine failure. The secret to good sump design is to reduce the chance of the pick-up being exposed to free air.

You can do this by using a tall deep sump, or by baffling and gating the sump. As the Locost is a small tightly packaged race car its nearly impossible to package a tall sump without running an impractically high ride height, so the sump needed to be baffled and gated, with an inbuilt windage tray.

 

Old/Poor Sump Design

My old sump was built from the flange of a standard front wheel drive sump, with custom sheet metal work underneath. The pickup was at the front and approximately central. It had longitudinal and lateral baffles with liberal drainage holes between each (making them almost useless) and a bolt in windage tray. It looked a whole lot like this:

Old Sump with Windage Tray

With the windage tray removed the baffles were accessible:

Old Sump Baffles

In hard right hand corners I think it was possible for the oil to slosh to the left hand side of the sump and expose the pick-up; as you can see there is no baffle in the central section where the pickup was located. The only saving grace of this design was its large capacity, giving minimal oil depth change when oil is trapped in the top end of the engine. Fortunately when I put slicks on the car it had terminal understeer and I don’t think I did any serious damage.

Given that the sump was off the engine, it was a great opportunity to inspect the oil/sump for particulates. The oil was clear of shiny aluminium bearing material, but there were some small bits of the cork gasket in the bottom; nothing scary but also suboptimal.

Blergh

I was happy to move on from this design…

 

New Sump Design

The new design was going to be wider and shorter than the original, positioning the pickup in the middle of four separate oil chambers, each giving the pickup instantaneous oil in the case of hard cornering. Also, the windage tray would bias towards the pickups central volume, to flood it and reduce the chance of oil starvation.

New Sump Flange

Fabrication started by cutting out the main flange to mount to the block. This was bolted to an old junk fitment engine I had lying around (I use this for making engine mounts, brackets etc).

New Sump

New Sump

New Sump Windage Tray

New Sump Pickup

Then the windage tray was cut to match the sump and measurements taken from the chassis.

New Sump Central Chamber

The sides of the sump were then cut and tacked to the windage tray. The central chamber around the pickup was mocked in place.

New Sump Gates

Sump Baffles

Welded Baffles

Then the baffles were put in place to create the four separate chambers. Four gates were added to the central chamber to avoid oil moving away from the central chamber in hard cornering; these were made from steel door hinges! Note that they have limiting tabs to stop the gates going over-centre and killing the engine. The baffles were welded into the bottom plate to stiffen the sump and ensure oil does not escape the central chamber.

Sump Drain

I almost forgot to add a sump drain plug (uh oh!), so I welded in an M12 nut. It turns out M12 course thread is not a standard sump plug size (arg!) so I had to use an M12 bolt with a magnet epoxied too it; could be worse.

Oil Leak Down Test

Once the whole thing was welded together it was tested for leaks using some old oil and left to sit for a few evenings.

Painted Sump

After this it got a snazzy coat of Racing Red!

Closing Comments

The sump is now bolted onto the car and we will see if it causes me any issues. On paper it should be a great improvement over my previous sump and I’m hoping it will give the confidence and peace of mind its designed too.

Before Christmas I will have gathered some track data, covering a large span of lateral/longitudinal accelerations and engine oil pressures. In a perfect world there would be no drop off in pressure over the full span of achieved accelerations; but realistically I’ll  be happy with just very low drop off and a healthy engine.

There is still plenty to do before hitting the track- front wheel arches, rear lights, blah, blah blah… I will get there eventually!

 

Fabrication: That time I made an Exhaust Manifold

I’m going to try to document a few of my older projects that fell through the cracks and didn’t make it on to here. Hopefully you’ll find these little articles both interesting and informative… and there are pictures!

A couple of years ago I made an exhaust manifold for a friends Seven. Having seen the stainless manifold on my Locost he wanted one in the same “over the chassis” style. The manifold on my Seven was/is OK, it does the job, but its not my best piece of work; I was learning along the way. The Locost itself is a testament to my abilities at each stage of its build; some parts are better than others due to improving my fabrication skills as I went along.

Locost Exhaust Manifold

Locost Exhaust Manifold 2

Locost Exhaust Manifold 3

Locost Exhaust Manifold 4

 

 

 

 

 

 

 

 

This second exhaust manifold project benefited from everything I had learn’t and was properly jigged and built close enough to equal length. I built it from separate bends of 316 Stainless Steel with 3/4inch headers and a 2 a inch collector. The primary lengths were specified based on the expanded volume of a single cylinder cylinder, going from atmospheric temperature to an exhaust combustion temperature I found on the internet (I have never measured exhaust gas temperatures before, so I think I can be forgiven for consulting the web).

From what I heard it did well on the dyno, and in truth I was sad to see it go; it took a lot of time and effort to make. Eventually the Locost will get one of the same quality, if not better.

Exhaust Manifold 1

Exhaust Manifold 2

Exhaust Manifold 3

Exhaust Manifold 4

Aluminium Printer Chassis 2

3D Printer: Upgrades 1/3

The current trend towards cheap and accessible home CNC machines is fantastic. I wouldn’t have a 3D printer if it wasn’t for the slow and steady reduction in component prices due to the high demand of an expanding hobbyist market. Also, China has made manufacturing a tenth the price it used to be.

While this has lead to the component parts, and ultimately the overall machine costs, becoming more affordable to the home-maker there are some short comings to this: 99% of hobbyists do not demand or need industrial level quality. If you want to print a bobble head of yourself to show your friends then usually you can live with middling quality, poor tolerancing and materials that only stay in shape at room temperature, and so 99% of the machines you can buy are built to that standard.

Now my 3D Printer was cheap and a somewhat early-days experimental product; the company that made it has already gone under (link). I wanted a “quick-way-in” to 3D Printing, hoping to make the odd part here and there for my numerous car projects, however I have quickly come to realize that it’s now a fundamental tool in my workshop, it just needs more capability. I need it to print accurately and repeatedly in higher temperature plastics. To ensure my machine could do this it needed two key upgrades.

1. Heated Bed

A Rare ABS Print Success

ABS can be printed in a warm room in your house, however you will soon become a lonely single man due to the smelly fumes.

My little fisher delta was very much limited to printing PLA (Polylactic Acid) due to not having a heated bed. PLA has a melting point of 150-160 degC and a glass transition point of 60-65 degC, so it’s easily extruded at 100 degC when it’s malleable and workable. If you’re printing at 25 degC room temperature then there is approximately 35 degC delta between its set temperature and the glass transition temperature, and that’s fine.

However I’m printing in a cold garage which is usually at 10 degC or less giving a Temperature Delta (TD from now onwards) of ~50 degC, this is still fine but you start to get into shrinkage issues on big prints due to the thermal stresses across the part.

I really wanted to print in ABS (Acrylonitrile Butadiene Styrene), or as I like to call it, “The Good Stuff”. ABS has a glass transition temperature of ~105 degC (much more like it!) and has no true melting point as it becomes amorphous (Wikipedia is awesome). It’s very tough, impact resistant, acid resistant and heat resistant, which makes it far more suitable for automotive applications.

However the glass transition temperature of ABS causes print problems as you have to extrude it at higher temperatures (I use 130 degC). This mean’s the TD across the part is far higher than if your printing with PLA and warping and cracking becomes a real problem. What you need to do is ensure the print is kept warm while printing to reduce the TD and it’s common to achieve this by using a heated bed.

2. Aluminium Chassis

Broken Printer Chassis

Acrylic really is a terrible structural material

Now simply heating the standard acrylic print bed was not an option as it was liable to flex all over the place and therefore I wanted to at-least use an Aluminium or Glass print bed. Aluminium has a thermal conductivity of 205 W/m.K which means it will heat up slowly and maintain a fairly uniform temperature distribution (Acrylic has a thermal conductivity of 0.2 W/m.K).

On the Fisher Delta the geometry of the print bed is important, as it has a three point self leveling system and these three points need to be accurately positioned. Because of this I opted to get the bed laser cut at a local company, along with the rest of the machine. The acrylic parts were all starting to bend and warp and it made me question how accurate it was anymore; I had only been using it for three months.

Aluminium Printer Chassis

Much improved frame with increased accuracy

So once I got my parts from the laser cutters I pulled my machine apart and rebuilt it to be far more durable and long lasting beast. She also looks pretty nifty in Matt Aluminium.

 

In Part 2 I’ll cover the wiring of the printed bed and the modifications I had to make to fit it into the Fisher Delta frame.

Fabrication: 3D Scanning

I didn’t mean for this little project to get so out of hand, but when there is a will… there is a really long winded way of solving a problem.

Firstly, my fuel injection conversion needed a swirl pot. A swirl pot is an intermediate fuel tank in between your original low pressure fuel tank and the high pressure fuel system. It is not always needed, depending on whether you swapped out your old low pressure fuel pump for an in tank high pressure pump or not. Seeing as I already own a perfectly good Facet lift pump, which is feeding my carburettor, I decided to install a swirl pot. The advantage of using a swirl pot is there is a far lower chance of fuel starvation in corners but at the cost of added complexity and weight.

OLYMPUS DIGITAL CAMERAI bought a shiny aluminium ‘pot a while back for this very task and needed to mount it somewhere in the engine bay. Because I’m putting throttle bodies on the engine I needed to get rid of the battery tray to make space for the trumpets. Having moved the battery and removed the tray I had gained a little space at the back of the bay for the ‘pot. However this area wasn’t exactly flat and true, which made the potential mounting of a flat aluminium tank a bit complicated.

My initial plan was to weld in a little steel support platform, simple right? It would have been a pain and would have required a lot of welding in the bay… and it way too simple a solution.

My girlfriend had been pretty positive about my whole 3d printer fixation and she suggested that there might be a printable solution to my problem. Of course I shrugged this off straightaway.

“It’s not an even surface; it would be an utter pain to measure and get right… I couldn’t guarantee it would fit, blah blah blah, nonsense nonsense, i’m an idiot” –  Josh Ogilvie, 2015

As always she was completely right, there was a printable solution, I just needed a copy of the surface I was working on… time for 3D Scanning!

 

OLYMPUS DIGITAL CAMERAWorking in an F1 team means you’re surrounded by a large number of greatly experienced and talented colleagues who are, more than likely, into the same weird stuff you are. Fortunately Highly-Experience-Engineer-Come-Pro-CAD-Modeller Mark was at hand and he pointed me at an Xbox Kinect style 3D scanner which would allow me to get the point cloud data I was looking for (If you really need to know it was a ASUS XtionPRO Live).

So on one isolated sunny October afternoon I set to work scanning the car. After trying every laptop in the house it was apparent that 3D Scanning is an extremely CPU intensive task (duh!) and that the only machine powerful enough was my PC; so that got dragged out onto the drive. The process was still very slow and I had to be patient not to move the camera too fast or it would lose sync with itself.

FARO_Scenect_3D_ScanI used the free FARO Scenect software to record the point cloud data and I found it very straightforward. It showed me what I had scanned in real time but did not try to do any extra meshing or reduction on top of that, so it was fairly rapid. The data is even in colour so you can tell what you’re looking at. I tried my best to get the panel from as many angles as possible, increasing both the mesh density and its accuracy.

The point cloud data was then exported as an .xyz file for import into MeshLab. I had never used any of this software before so it took me a few evenings of trial and error with different solutions until I found the one I liked. Take it from me, MeshLab rocks. It’s an extremely flexible mesh manipulation tool and has everything you need to turn a point cloud into an STL or equivalent file. In the end I settled on the following straightforward workflow:

  • Save off a copy of your Point Cloud data and hide it so you don’t over right it; you know it makes sense.
  • Import the Point Cloud
    File->Import Mesh->Pick the XYZ File, MeshLab does the rest
  • Delete any unneeded points
  • Orient the Point Cloud
    Do this now or it’ll never be aligned again; trust me. Filters->Normals, Curvatures and Orientation->Transform: Move, Translate, Center
  • Poisson Reduction
    Filters->Sampling->Poisson-disk Sampling
    You will have too many points to sensibly create a mesh out of so you are going to want average them out. This method uses statistical probability to ensure you lose the least amount of LIKELY real points. The hope is you scanned enough data, from enough different angles, that once it is reduced the data will be correct-ish. Remember to enable “Base Mesh Subsampling”.
    MeshLab_SubSampling
  • Calculate the Surface Normals
    Filters->Normals, Curvatures and Orientation->Compute normals for point setsMeshLab_Normals
  • Poisson Mesh Construction
    Filters->Remeshing, Simplification and Reconstruction->Surface Reconstruction: Poisson
    This will build a closed mesh out of your Point Cloud data. It’s important to note that it is CLOSED. If you’re trying to build a surface you’ll need to delete the excess vertices.
    MeshLab_PoissonMesh

Then you can export the results for use in your CAD package of choice. For instance, I couldn’t use the resultant STL data straight away as it had to be further post processed to become a surface object. I put my new surface patch into an assembling along with a model of my Swirl Pot and the rest was fairly straightforward. I drafted two extruded bases from the ‘pot down to the surface to fill the gap.

To my surprise it all actually fit together once printed and after a quick splash of Matt Black I was ready to bolt it all in. I’ll take some more photo’s once everything is finally mounted in the car and painted.

I want to use this same method build a CFD model of my little red car later next year; wish me luck.

 

OLYMPUS DIGITAL CAMERA

OLYMPUS DIGITAL CAMERA