Monoposto Jan 2025 onwards

 Jan 2025 - Battery management

 

Total loss system needs careful thought about energy storage during a race meeting and the necessary charging scenarios. The only approach is to estimate worst case.

This system has three modes a) Monoposto running from 20AH Lithium M/C battery and expected duration b) Charging Monoposto battery from RV battery and c) Charging RV battery from the van starter battery during going home time.

 Here is a table predicting the life of the M/C 20ah Lithium battery and RV battery (donor). AH = Amper Hours WH = Watt Hours. The table assumes the M/C battery is charged from the RV battery at some point in a two day weekend.

a) Running from a M/C battery the table labeled LOAD shows 2 days running charging is expected after 10 runs from the RV battery. It is assumed 20 runs is a two day weeked and only loads the RV battery less than 50%.

b) In the event of deciding to charge from the RV battery it must be done via a special charger that is designed for such an exercise. RV batteries are not designed to start cars. Some chargers will not operate below 12.7v.

c)  Van charges RV battery this again must be done with a charger designed for the application. It must:-

1) Automattically disconnect below 12.4v otherwise it will flatten the Van battery

2) It must be compatible with the RV battery

The following product appears to meet the requirements

 

The only reservation I have about this charger is, will the RV battery terminal voltage remain above 12.4v for long enough to charge the M/C battery? The Eco-worthy charger support person tells me the input voltage must always be greater than the charged battery if that is the case then the booster will be necessary as it approaches full charge of the Monoposto battey?

As an insurance against voltage drops and the charger cutting out prematurely I have found this Booster product

 This product takes in 9-13v and produces a regulated 13.8v at 18a current delivery, however needs cooling.

I have checked the Lithium M/C battey terminal voltage and it is offset down on the curve shown so I expect the 100ah RV battery to behave similarly probably due to resistance loss in the connectors and cutout/fuse. You only have to loose 0.1V or 0.2V and you have lost 20% of the capacity of the RV battery for charging purposes.

AI search results from Google; When comparing an Eco-Worthy charger's input voltage range to the charge voltage needed for a lithium battery, the input voltage range will be slightly lower than the lithium battery's charge voltage, as the charger needs to step up the voltage to reach the optimal charging level for the lithium battery; for example, a 12V input on an Eco-Worthy charger might be used to charge a 12V lithium battery with a charge voltage around 14.4V depending on the specific battery type and manufacturer specifications. 

It would appear ECO-worthy have possibly miss-led me here?

You can see exactly from this display the state of the battery, the amount used and when you charge the Monopost battery you will know how many runs you have had and the average consumption for each run. This will allow a computation of how much energy you have left in the Monoposto at any given time.

10th Feb 25 - Tery Griffiths  2CV clutch conversion

The perceived wisdom in the A7 racing world  is that the standard Austin Seven Clutch is less controlable than a modern diaphram spring clutch. This conversion is quite tricky as a number of items have to be fabricated. Terry Griffith's in the www.austinsevenfriends.co.uk forum Diaphragm clutch details the best recipie to make this change. Depending on the individual component part choices may result in design differences with Terry's original documentation.

The  variation in chosen components results in some design changes. Here is a list of what I did, I will start with the items closest to the engine and work outwards:

* The flywheel has to be modified to a) lighten it and b)The clutch friction plate has a differnt llanding area  c) Themounting holes (M7) and pegs are different for the 2CV spring housing. I took the oppertunity to lighten the flywheel also.

 

* The nut holding the flywheel has to be rounded at the corners to improve clearances between the clutch adapter plate and the nut.

* The 2CV clutch plate needs and adapter plate to convert made to the original A7 splined drive centre.

 

* There needs to be a "saucer" shaped release bearing adapter made that is placed between the original A7 release bearing and the diaphram springs. This was the most confusing part of the conversion for me as it had to have a 70mm step to be compatible with the spring housing. 

 

*  The first motion shaft housing needs to be modified, it needs to be reduced by ~20mm to allow room for the saucer. This is standard Terry Griffiths.

 

* The release bearing assy needs to be machined to ensure the ovrall dimentions of FMS housing + release bearing + saucer leaves a gap to the diaphram springs. This involves some careful removal of material both sides of the release bearing forging.

* The first motion shaft itself may have to be modified as the landing area of the FMS bearing is different after triming the housing. I had to remove about 5mm of 0.1mm oversize for the new site for the FMS bearing.

* Springs have to be made to link the Release bearing to the A7 actuating mechanism.

 

* The pedal has to have a) A return spring to keep the saucer off the diaphram springs when not deployed. and b) A limit stop to prevent over travel of the saucer against the spring housing as this brings in the drive to the gearbox again. 

 

Bottom left is the return spring and middle top is the limit for the pedal travel.