Attempting to build the world's quickest UK road legal Elan

Gosh, two days in a row on the car :-)

Sorted out pneumatic system for parachute.









Made a call on which nitrous bottle to fit. 4kg difference in weight (2.5 v 6.5kg). AN added bonus of the smaller bottle is that I can just squeeze it on to the nearside tub, improving the rear weight distribution slightly. As gas will only be needed off the line and at the top end and using it for the whole track will overstress the engine. Engine is good for the 600bhp I have with race fuel. 25bhp shot off the line and 50 or so for a second or two at the top end should be fine. I have the stuff so it would be rude to leave it on the shelf :-)

Update - Son is going to 3D print me a couple of clamps for the nitrous bottle. Kids can be handy sometimes and actually SAVE you money :-)

Secured the fuel tank as it was just sitting in the boot held in place by the fuel pipes.

Anal about weight warning! Whilst sorting out the rubber mounts I changed them for lighter ones :-) Removed approx 70gms. Original on left, replacement on right.







I then decided to start the installation of the diffuser. There will have to be some mods made to it as I forgot that the new wheels will be a couple of inches wider on the inside, but no big deal as it only affects the first 150mm. I will cut and shut once I have the wheels and tyres.

It extends around 100mm past the bumper but less than the boot extension. The parachute frame will have to be lengthened so it clears the extension.







This may come as a bit of a shock to many YouTube 'aero tuners' but a fair amount of research went into the design of this diffuser to ensure that it works with the rest of the underfloor aero so actually has a positive effect on the downforce. Most are fitted because they 'look cool' but claim they are also aerodynamic. Well, I guess they are in that they affect the air flow, but not in the way claimed :-) They only look cool to 13-20 year old boys who know SFA about aerodynamics. They remind me of when I was 13 and fitting playing cards to the front wheel of my bike so they flapped against the spokes :-)

Rant over. Feel much better now nurse, no need for the sedatives tonight.

I needed a couple of clamps to hold the nitrous bottle on to the wheel tub. My initial thought was to use a pair of 102mm exhaust clamps, which I duly ordered. As soon as I had done that I thought, "damn, my son can 3d print me a pair!" So, if anyone needs 102mm clamps I have a pair :-) Son came up trumps, as usual, with a pair of 3d printed carbon clamps. They look way smarter than exhaust clamps and weigh in at 92gms the pair as opposed to 500gms. A win-win.

In order to get a better idea on parachute/tray alignment I decided to pack the chute for the first time. I have had the chute for a number of years but it has been out of the bag for most of that so as not to risk making the folds permanent or getting mold.

Watched lots of videos and they were all slightly different so there appears to be no right way, with each chute style having different folding methods.

Untangling the chute from where it was hanging was the first PITA. It had slipped many times with me simply hooping it back over the bar so it got into a right mess.


Once on the floor it was relatively straight forward to sort out the cords but how to fold was a different matter. The main part of the chute wasn't too bad but the top/middle bit just didn't want to lie flat.







Anyway, I managed to fold it up using the most popular YT method as far the main chute, cords and drag line were concerned. Now to put it in the bag and that is where is all fell apart, both my packing skill and patience. This is realistically a two person job, at least for numpties like me. If you do this every run you will no doubt get good at it, but I hope to never use it as even at 150-160mph I have proper brakes as opposed to silly drag racing units so stopping isn't a problem. It's primary purposes are to satisfy race regs and get me out of the brown stuff if I get out of shape or have a total brake failure (with a duel system this is unlikely). A simpler way to pack the chute with the bag still attached to the car will be a great help.





A LOT of force is required to push the pilot chute spring into the bag. The back of my car, being thin carbon fibre, isn't rigid enough to do this so I had to remove the bag and put it on the floor. This allowed me to lean on the spring with my knee but I still couldn't get it all into the bag. A slight movement of my knee and the spring would shift position and I would have to start again! It looks easy on the videos and I am sure that other people manage it easily but I gave up and had a rethought. I wondered if there was another way and, lo and behold, there is. Air launching the chute! Basically a pneumatic cylinder pushes the bag out instead of a spring pulling it out. Using this method also means that, as the chute is pushed out with more force and quicker than a spring can manage, the chute being under the tray shouldn't cause a problem. A win win.

All the videos show the actuator being powered by a CO2 canister, but I already have an air supply so that is good. I have a suitable solenoid in my stash along with nylon tube and push fit connectors. I have a selection of actuators but none long enough so that will mean a trip to Ali Express for a 25m ID 250mm long actuator at around £10-15. The biggest expense will be the deployment bag which replaces the spring powered pilot chute. No luck in finding a supplier in the UK so far. I will keep looking but we are in the States in a month or so, so I will get one there if necessary for around £75. I will make the push plate.

I have a spare switch on the dash for arming the actuator and I added extra wires to the loom spec just in case I needed extra stuff in the boot and that has paid off.



To buy an off the shelf kit would cost £4-500. I just need to buy the actuator and deployment bag for less than £100, that I can justify to myself.

Still watching with fascination!

Don't, for one minute, think that it wasn't considered :-)

Carbon doesn't like repeated shock loadings or extreme stress (See Titan), which will occur with 150+psi being instantly released against it. The disc would have to be a lot thicker than the car's body panels as it mustn't deform under pressure, which would increase the risk of structural failure The area around the shaft would have to be even thicker as this will take the brunt of the force.

On the other hand, an aluminium plate can be thinner as some deformation will be acceptable and the area around the actuator shaft can be easily strengthened (as can be seen in the photos above).

Therefore, the weight difference would be marginal. Also, making it out of aluminium is easier, less messy and quicker.

Horses for courses :-)

I believe that my principles are intact :-)

I know little bit about parachutes (did a few static line jumps many years ago) but nothing about them when used as a brake. Is there any way of testing it and the air launcher? is there a minimum speed for it to be effective on deployment ?

Further research has revealed that a deployment bag isn't essential, so I will not buy one until I have tested the chute on the track. Saves a little weight and £75.