Bike rack

I have spent a lot of time thinking how I can get my road bike on the back of the Sylva. Here is the fruits of my deliberations. I doubt there is a queue out there for the design. The parts were fabricated in 35mm sq  section ERW 1.5mm wall thickness to keep the weight down. The rear plate is 12mm thick alloy. Just a bit of fun for the holidays.


Parts fabricated in 1.5mm ERW

J15 Bike rack

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Helmet loop

One of the many issues concerning fitting GRP seats in a J15 is the roll-over bar helmet clearance. I took advice about hill climb/sprinting the J15 and the verdict from a track-side scrutiniser was that the helmet clearance to the roll-over bar was insufficient. Apparently for MSA road going class this is a grey area but the advice was "don't do it".

The other issue is the supports for the roll bar have not been installed by me as the rear tub has to be cut. I think the one bar to the rear chassis leg would have less impact on the rear tub.

I recently obtained a special seamless tube from Jeremy bent in a loop to create a helmet loop. I made templates out of plastic ducting left over from the Virgin Broadband install.

I have now welded the loop in place  I got a piece of 37mm high tensile seamless tubing 2mm wall thickness from Blakes Metal Merchants which made up the rear stay.

The rear chassis leg support bracket strength has been enhanced by an extra support to link it to the lower chassis leg.

Creating templates

Welded loop

Chassis leg attachment point

Some chassis paint

Rear stay fitted

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Re-visit Dynamometer

There was a problem with the last power plot I did last year as the throttle body butterfly was not opening fully. This visit back to Sitech Racing was to validate the update to the throttle body linkage. Here is the plot from my visit in August 2013: http://sylvabuild.blogspot.co.uk/2013/08/ecu-re-mapping.html

The standard engine produces 125bhp at the flywheel so no increase in power was observed in August. Since then I have fixed the butterfly versus pedal position.

You can clearly see the maximum power has increased by 43bhp to 155bhp @ 6700rpm a most agreeable result for the cost of a sift in pivot point in the throttle linkage.

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Headlight covers

One of the key aspects of the J15 is the retro classic look which would not be complete without the headlight covers. I have pondered for at least the last year on how to mount them or weather I would be better off not fitting them at all. The build guide is not a lot of help. One of the forum members suggested fitting with 3 off fixings each side using alloy right angle brackets and rivnuts.

While I agreed with the three fixing approach. I did not want unsightly alloy brackets. I opted for straight brackets made of 5mm thick GRP board (which I had lying about). The board was fashioned into 15mm x 30mm plates with a 5mm rivnut in one end. A slot was then cut into the GRP bonnet (hood) around the extremity where the Plexiglas cover was to attach. To finish them off I mixed up a small quantity of Gel Coat to make them blend in. To make the ss bolts captive I used M4 nylon washers over the M5 thread. If they work loose at least I won't loose the bolt.

GRP board with rivnut fixing

Gel coat added

Finished headlight covers

Contents
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Custom steering boss

For the IVA test in June I did not fit the aero screen as the general advice was not to provoke the testing sharp edges rules. I therefore fitted a cheap steering wheel with lots of padding that would give me a good view of the instruments and satisfy the IVA man.

After the IVA test I immediately fitted the aero screen, wanting to take it touring in Scotland and not having to wear a helmet all the time. That is when the trouble started. The 300mm steering wheel now fouled the aero screen. To save having the car off the road in prime blatting season I elected to fit a small 250mm D shaped sports wheel. The clearance and driving position was now fine but the very positive steering and view of the instruments was poor. At that time I decided to put the problem off for another day.

Aero screen with sports wheel

Over the Christmas 2013 break I decided not to put it off any longer. I ordered up a 120mm diameter round billet bar 2" deep from the local metal merchants. This is pretty well the limit of what I can easily turn in my small lathe. To make it easier to mount in the chuck, first off I put a 2" hole down the centre using a Rota-broach hole cutter. (*) see note

The final boss had 18 radial holes:
* 6 to mount the steering wheel flange
* 6 recessed holes to mate with the existing collapsible boss
* 6 to mount the cover plate
However you need a rotary table or indexer to accurately position these holes or an incredible amount of luck.

The resulting wheel is much improved classic style suiting the car and owner.

See clearance S/W to plexiglass

Dashboard side

Profile with additional 20mm clearance

Contents

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Note(*):For those who have not discovered Rota-broaches you don't know what you are missing. They are precision hole saw (you do need a vertical drill to use them however).

Tonneau design

This page is intended to illustrate the wonderful work that Karen did who made my Tonneau. The original pattern was made of Toolstation groundsheet and marked up with paint stick then cut out with sissors. This is not Karen's main job but I think you will agree she has made a fine job. The first test will be on the road to Applecross soon with the Westfield Club (WSCC).

View from front

Rear off side

 

Contents

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Fuel System modifications

I have had to make a number of modifications to the original fuel system design as a result of experience when using the car. The first sign of trouble was on my return from the IVA, I decided to top up the tank in my garage and to my horror the tank was pressurised, the cap just about blew my head off.

The second problem is the fuel gauge, despite my efforts to make it accurate, was not. It was telling me it was empty and it had 1.5Gallons left. The standard VDO gauge is 380mm and the tanks as designed is 420mm. 40mm is roughly equivalent to the error of the gauge.

I had a read at the forums particularly on the matter of pressurisation and it turns out that HP fuel systems can cause this problem particularly when there is no room for expansion in the tank and where a simple one way valve is fitted. The fuel comes back from  the fuel rail slightly temperature elevated and therefore wants to expand the fuel in the tank. The one way valve compounds the problem as it is designed to let air in and not out. There is also a charging of the tank when you start the car up for the first time. Repeated start stop compounds the problem.

There is a valve called a Mocal valve that is designed to alleviate these problems as it works in both directions with limitations of course. This valve has a 0.5 bar negative inlet trigger point and a 0.75 bar positive pressure relief threshold. This is an expensive part ~£60 from various sources.

I fitted the Mocal valve and although this prevented the tank pressurising it dumped neat fuel occasionally under the car. My driveway has a 15deg slope and when driving up, the two way valve becomes temporarily blocked by fuel and then when the tank becomes pressurised it dumps neat fuel into the overflow till equilibrium is reached within the tank at 0.75 bar.

This in my opinion is an inherent problem with aero style tanks where the Mocal valve has to be connected at the same height a the top of the tank. It would be slightly easier if there was a filler neck, where no fuel was present and no fuel would be expelled.

The puma ECU has provision for a Carbon filter for such an eventuality along with a solenoid valve. When you are above a certain rev range it dumps the filtered fuel into the inlet manifold and weakens the mixture from the fuel rail. All by computer control.

I decided not to use that system as I had nowhere to put a carbon filter and I had no idea what would have happened with my variation in the design of the fuel system.

I pondered the issue for several weeks and came up with a three part solution.

* I install a fuel filler pot with a one way lead free valve from Car Builders Solution. The design of which forced a 45mm air gap at the top of the tank. No matter how hard you try it will not allow filling of the tank beyond a -45mm limit.
* Installed an overflow container with a glass bowl so I can keep an eye on any overflow events from the Mocal valve. It turns out it only overflows after driving up the driveway, after the tank has been filled and then only a very small quantity of fuel is discharged. The overflow reservoir can be emptied occasionally. Better than leaking fuel at the pits or the start line.
* Modified the VDO sender to read correctly by extending the range. I don't have any pictures of this modification, trust me it was difficult.

The overflow reservoir was made out of a large fuel filter from a large us car or lorry obtained from ebay.





Modified fuel system

Overfill protector

Mocal valve and overflow reservoir

Contents

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