Locost: Desperate Trackday Preperation

Life has got the better of me over the last few months and progress on the Locost has been slow. I had hoped to be doing a Trackday this December, but the car simply wasn’t ready, and there weren’t enough hours in the day to make it so. Subsequently, when my mate Dan messaged me about a Trackday he was organizing at Snetterton in February I was all ears. This is just far enough away to give me enough time to get the car prepared, but at a push. Fortunately, I work well under pressure.

So for my benefit, here is my Locost-work-list that needs to be completed before February the 13th:

  • Fibreglass Rear Arches – By now you have read my article about the Locosts rear light pods. These are still being fettled into the arches so the lights can be fitted. I’m hoping to get these into primer over the Christmas break and bolted to the car.
  • Finish Lighting Loom – With the arches in place I can finish the loom for the rear indicators and brake lights. I ordered connectors for this job, and have built an unfinished rear-end loom, so this should be fairly straightforward.
  • Mount Front Arches – This is one of the more complicated tasks. I have some M8 threaded standoffs that I can weld to the front uprights to make mounting easier, but really I need to bend some 3/4inch tube to make the frames for these. If I can measure these up before I head back home for Christmas I should be able to get this done.
  • Finish Mounting Drivers Seat – This is a straightforward task as it is already bolted in place, the 8mm holes simply needed to be taken out to 9mm. I would also like to re-paint the floor pans while the seat is out; just in case it rains.
  • Fix Leaky Sump – Remember that awesome wet sump I made? Yeah it leaks. I’ve been struggling to get it to seal to the block. I always used to use the standard Suzuki cork gasket but this time have been trying to go purely Silicone; this is clearly a terrible idea. The sump needs to come off one more time and get sealed properly. I have a spare gasket so all I need is time.
  • Mount Rear Panel – I have a sneaking feeling that I need have a rear panel to cover the fuel tank for Trackdays. It would make sense that the driver would not be allowed straight line of sight to a flammable tank of gasoline. So for my safety I need to sort this out. I have a carbon rear panel molding, so I just need to get measuring and cutting before Snetterton.
  • Shakedown – I need time to drive the car and check it has no issues. It has been dried stored for over twelve months now, so with a little luck it should be fine.
  • New Tyres – My old Yokohama A539s are almost as old as the car and have seen far better days. While they have heaps of tread on and I’m tempted to give them a final send off, they need to go. Given I’m not going to be racing anyone I may just get a fresh set of A539s or the Toyo equivalent. Cheapish tyres, but at-least new tyres.

Optional:

  • Paint Front/Rear Arches – It would be nice for the car to look good while on track, but my priority is actually being there. However, if I get the time it would be nice make things pretty.
  • Wire In Datalogger – This is a project I am yet to write up, however over the last couple of months of dark evening I have created a datalogger for the Locost. I would quite like to run this at Snetterton as the data will tell me a lot about the car and help me progress my driving. This is almost not optional in my eyes, but I guess its low priority.
  • Cover Gearbox Opening – I ran a pneumatic paddleshift system for a while, which is now on the back burner until I can track the car. This required opening  up the tunnel around the gear-stick to fit. With the normal gear-stick mounted now the driver has line of sight to the engine bay. For safety reasons this is bad, and although I don’t think it will cause any issues, when I get the time I hope to cover this up.

What do you think? I don’t have anywhere near as much free time as I used to and could do with some spending some time with friends over the Christmas break. So realistically, other than the rear arches, everything has to get done in six Sundays. Fingers crossed.

(Featured imagine taken from here)

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

3D Printer: Upgrades 2/3

It’s taken me almost two months to get around to writing part 2 of this series, opps! However this is because I have actually been using the printer, and working on a project for a friends rally car (watch this space).

Now where were we… ah yes, the heated bed. In the previous article I explained why a heated bed is a good upgrade for a 3D Printer, especially one that uses high temperature plastics such as ABS. Installing one is easy straightforward, however my little machine required a few modifications along the way.

To convert your printer to use a heated bed first you’re going to need, you guessed it, a heater to heat the bed.

1. Sourcing a Bed Heater

A simple flat Silicone Heated Bed. Easy to install... and ORANGE.

A simple flat Silicone Heated Bed. Easy to install… and ORANGE.

I chose to use a 12V Silicone Bed Heater. These are easy to get from China and come in an array of different sizes to suit your needs. As I write this, doing an ebay search brings up 47 of them from a range of manufacturers.

Truth be told I took this route because its what everyone else does, however there are some major benefits to this style of heater. Firstly they are simple to wire (4 wires, with feedback), they are relatively thin and they can be driven straight from most standard firmware.

 

Most common printer PCB’s have the ability to drive a 12 or 24 volt heated bed directly, however I opted to use an external power supply. My heater is rated at 350 watts, so at 12 volts it can draw up to 350/12 = 29.1 amps! I was not willing to push that through a thin PCB, no matter how much the manufacturer says its marginally spec’d to that ampage.

An all purpose 12v DC Power Supply. 240v to 12v made easy.

An all purpose 12v DC Power Supply. 240v AC to 12v DC made easy.

In hindsight I probably should have gone for a higher voltage heater and then wouldn’t have had to flow as many amps to achieve my desired bed temperature; especially given the fact my power supply has to drop down from 240 volts! A smaller step would have been more efficient. In fact 110V heated beds are available, their just less common.

 

 

2. Wiring the Heater

The heater has four wires, one pair is power/ground for the heater itself and the other pair are attached to a thermister embedded in the heater. The thermister wires were attached directly to the control PCB and this allowed the software to measure the temperature of the bed while printing. The power wires went to the external power supply via an automotive relay (12v 40amp). The relay was switched using the heated bed control off the PCB, which is usually used for driving the bed directly. This giving a lovely 12v output to charge the relay coil and switch on the bed.

Power Supply

IMG_20160525_190955

 

 

 

 

I ran the power switch and thermister lines through the case via some two pin connected. Initially I wired theconnectors straight to the aluminium printer chassis but soon realized one of the pins ground through the outer thread! This mean’t I had to print some little top hats to make sure the signals didn’t ground. Printing parts for the printer; it’s 2016.

Case ConnectorsExternal Connections

Working Temperature Feedback

 

 

 

 

Once this was all wired together surprisingly it worked straight away (well once the above earthing issues were fixed). This gave me closed loop temperature control of the bed, ensure a nice consistent temperature.

3. Fitting the bed

It wasn’t all straightforward. The Chinese manufacturer neglected to give any dimensions when listing the heater, so I had no idea how thick it was going to be. I had a feeling it was likely going to cause issues with the self leveling system, as this requires the bed to bottom out when being installed to get under the sensing probes.

Low and behold once I installed the heater the aluminium bed no longer fit. Fortunately I had my non-heated bed on hand and I used it to print taller probe mounts. Magic.

Raised Probe Towers

 

 

 

 

So that’s it for this installment. In part 3 i’ll go through building an enclosure and the tricks I’ve learn’t when printing ABS.

 

A closing thought and something to consider before getting one of these machines. The more I have used the printer, the more I have come to realize that it is as much a piece of workshop machinery as a lathe, mill or welder. It requires maintenance, care and cleaning to remain consistent and usable. In my experience, few people have the patients for this.