Tuesday, 14 April 2015

Midget no more

Alas the Midget has gone!
After four years of fun I've traded up to a TR6.
I've always had a love hate relationship with Triumphs. My Stag was a nightmare in the end (but sounded glorious).

Fired up and ready for her new owner (the car that is!)

Check out the new blog if you are interested in Triumphy things:

Sunday, 3 June 2012

Frogeyes for a midget

Now, I've always been keen on the look of the Sprites famous frog eyes.  In fact I was looking for a Sprite when I bought the current Midget. In the end the premium was just too much and I'd only have ended up fitting a 1275cc (or bigger) engine, disk brakes, etc.  In the spirit of the Frogeye Sprite, and for additional rally style, I decided to fit some enormous spot lights to ABW.

After some research, then searching, I selected a pair of seven inch spot lights from Sim. These are very similar to the “Oscar” lamps from CibiĆ©, which were popular on rally cars in the 1960s and 1970s (and are still available today). The Oscar is a circular auxiliary driving lamp specifically designed to combine excellent performance. A distinguishing feature is the classic design with a chrome ring.

SIM seven inch spot lights

Having removed the front (and rear bumpers) – see previous article ("De-bumper or not de-bumper?") – the front bumper mounts were the obvious place to mount the lights.  It took several attempts to manufacture a bracket stiff enough to offer adequate support for the large lights.  L-shaped stainless angle brackets were bolted direct to the bumper mounting bolts with a half inch hole facing upwards for mounting the spot lights.

Having fitted the lights, the next task was to wire them up.  This was reasonably straightforward.  However, because I wanted to use halogen bulbs, which draw a fairly high current, I wanted to utilise a relay and some hefty automotive cable. The relay was a 4 pin, 30 amp item. As an aside, some time ago I purchased some decent ratchet crimping pliers; this is just the job that makes them worth every penny spent.  For those interested in similarly fitting spotlights, the wiring diagram is below.

Spotlight wiring diagram

I chose to power the relay from a source that was already available behind the dashboard from the ignition switch.  Thus the spotlights will only operate with the ignition key switched on.  Alternatively, I could have taken the power from the lighting circuit, or specifically the main beam lighting circuit.  I decided to keep it simple and flexible.

I fitted the new spotlights with halogen bulbs.  The fitting was able to take H4 bulbs.  These are duel element (high and low beam) which is a bit of a waste, since only the high beam is wired for use.  However, the bulbs are readily available and also match the halogen bulbs fitted as a conversion to the Midget's headlamps, which means spares can be reduced.  Wiring the H4 bulb is not entirely obvious - the picture below shows which terminal should connect to which socket on the bulb block connector.

Terminal layout for H4 halogen bulb

I was pleased with the switch holder, which was sourced on e-bay.  This looks from the right period and an amber warning bulb was fitted. I attached the switch holder to a sheet of stainless, bridging from the bulkhead to the lower edge of the steel dashboard.  This enabled me to use existing holes, rather than drilling new ones, which may eventually be in the wrong place. For now I positioned the switch centrally, next to the Brantz rally odometer (see previous article: "Rally trip meter tips").  Setting it back just a little looks best.

Period spot light switch and warning light (centre)

I'm happy with the final result.  The output is pretty bright!  The look is sporty; ready for the next regularity rally. Next job:  rear fog light.

Rally lights fitted - ready for action!

Monday, 30 April 2012

De-bumper or not de-bumper?

Now that is the question!  I have been toying with the idea of decluttering ABW since I bought her almost a year ago.  The car already came with a fast-cam Oscelli engine and Minilite look-alikes.  The addition of some large driving lights and a little more "rallye stylee" finally convinced me that naked was the route. The weight penalty for the bumpers and hangers must be considerable.  I have also struggled to find a decent pair of rear quarter bumpers to replace the existing crinkled chrome, misshapen efforts. And  I could never get them hanging straight either.

Now the purists will no doubt shake their heads and groan at any modifications.

An obvious downside is that I will need to avoid bumping into anything.  Although, I'm far from convinced that the existing heavy ironwork would do anything other than transmit the impact to the chassis and bodywork. I don't intend testing this hypothesis.

At the back I've retained the over-riders; these also serve to hold the number plate illumination.  I have filled the excess holes with some low-profile allen head bolts, with rubber gasket for a waterproof seal.  In time I plan to fit a rear fog warning light and perhaps an auxiliary reversing spotlight.  I may switch to a horizontal rather than square number plate.  Phase 2!

A naked rear!
Around at the front end, I have removed the bumper and used the forward facing bolts to mount some brackets for spotlights and to locate the front number plate. Fitting the driving lights to my satisfaction took some time - more on that later!

Safety Fast front end.
However, I am still on the hunt for some decent replacement rear quarter bumpers and I have carefully stored the front bumper and various fixings.  I do not think the existing items are good enough to re-chrome, but if I can find some quality original items I will consider refurbishment. There is always a chance I will want to change my mind, so I am keeping the options open.

Anyway, what happens to all those bumpers - especially the rubber ones - that are removed?
In the mean time, naked is the way!

Saturday, 21 January 2012

Amps vs. Volts?

Having had problems with battery discharge I decided it would be advantageous to fit some sort of gauge to test the performance of the electrical system.  In any case, period accessories look great!  The only question was which instrument to choose?

In a fight, who would win?  Amps or Volts?
Ammeters are widely fitted to classic MGs and Minis, with a variety of indicator ranges (for example, +/- 45 amps).  But what does the ammeter show?  These measure the electrical current flowing through the circuit.  Typically they are wired in series with the load.  This means that the current flows through the ammeter itself, requiring beefy, heavy duty cables connecting to the device to withstand the potentially high currents. "ABW" has been retrofitted with an alternator.  The electrical current is therefore even higher than might be expected from the original dynamo system.

Whilst useful for measuring the drain under load (for example, from head lights), the car already has a red ignition warning light, which gives a good indication when charging is not occurring.

Voltmeters are connected across a current load and measure electrical "pressure".  This makes fitting a simpler proposition, because they use standard car wiring.

The voltmeter principally provides information about the status of the battery. With normal alternator / voltage-regulator functioning, the voltmeter will read around 14v, falling to 12-13v as the load on the alternator increases (for example, when lights, wipers, and heater blower are used together).  If the alternator fails, then the voltage reading will start to drop as the battery takes on the work and begins to discharge.  Ratings below 12v, particularly on starting, can also indicator a problem with one of the cells on the battery.  A high reading indicates that the alternator is failing to regulate output and possibly cooking the battery and wiring loom.

Given the relative difficulty in fitting an ammeter compared to a voltmeter, and the information that can be gleaned from each device, the latter seems the obvious first choice.  A scan on the internet confirms this opinion.

Smiths voltmeters
MGs were originally fitted with Smiths gauges and I'm keen to keep that period look and feel - so Smiths it is!
The Smiths voltmeter gauges work by internal bi-metal resistance, similar to fuel and temperature gauges.  Like the fuel gauge, the voltmeter does not respond instantly, but the needle climbs slowly when power is supplied.  The gauge draws some power, so is best connected to the "ignition on" circuit with the other gauges.

Being standard on many British cars, especially popular BMC models, a wide variety of suitable 2" gauge designs were sold over the years, some still available new today.  These are variously marked "volts", "battery", "battery condition", or a combination there of!
Various Smiths voltmeter designs

Sourcing a Smiths voltmeter
Several firms supply new or refurbished units.  Perhaps the most extensive range is available from the Gauge Shop (http://www.thegaugeshop.com), who specialise in period Smiths and Jaeger gauges.  Speedy Cables (http://www.speedycables.com) are manufacturers and suppliers of automotive instruments, including Smiths gauges, which are skilfully crafted to the original specifications using the original tools and dies. They also do a cracking business recalibrating speedos.

Being a cheapskate I plumped for ebay!  The result was a rather battered gauge, probably from a mid-70s MGB.  Still it only cost me £7!  Unusually it came complete with a bulb and fixing bracket.

I hunted down some very useful instructions entitled "Smiths - The Care of Instruments" on PDF from Mk1 Performance Conversions (http://mk1-performance-conversions.co.uk), a website dedicated to early Minis. The guide, from 1966, is helpful for a range of instruments.  The voltmeter page is reproduced below, showing a wiring diagram.

From "Smiths - The Care of Instruments", published 1966
The ebay voltmeter has been dismantled, glass polished, and the grot cleaned out.  The face is not perfect, but has come up presentable.  The v-profile bezel was difficult to remove. It is retained with three small tabs.  Ideally the bezel should twist to register with corresponding gaps in the lip of the casing, but some hard caulk material effectively glued the bezel to the body.  Carefully prising two of the tabs up I was able to pull the bezel off.  It has cleaned up reasonably well, with black paint to the inner side coming off with paint brush restorer fluid to reveal clean chrome.

I've reassembled the unit, with a fabricated piece of rubber to seal the glass and bezel.  If the face was perfect, I would invest in a new bezel and new rubber o-ring (all of which are available from several suppliers, for example AES:  http://www.autoelectricsupplies.co.uk).  As it is, I'll probably make do and replace with a better specimen later. Now all I need is a a dashboard panel - more to follow...

Refurbished  Smiths voltmeter

Saturday, 31 December 2011

Rally trip meter tips

Having got excited about classic car rallies, we decided to go the whole hog and fit a rally trip meter. This was of course an opportunity to spend many hours as a contortionist upside down under the dash.

The model selected was the Brantz International 2 Pro from Right Track Enterprises Ltd; probably the most popular device used by classic car rally enthusiasts. It is a highly accurate odometer with dual displays and is ideal for stage rallies. The odometers can be accurately calibrated in miles or kilometres to match a measured distance on the rally. The second trip meter can be zeroed at any stage and even run backwards (useful, for example, when a navigational error is made and one is retracting ones steps).  Importantly, this unit is allowed to be used in most regularity rallies, as it merely duplicates the car's odometer and doesn't calculate average speed directly.

Brantz International 2 Pro rally trip meter

Fitting the unit is quite straightforward, with direct connections to each side of the battery, so as to reduce interference from other circuits/devices. An in-line 2A fuse was fitted on the live wire. The only two difficulties are fitting some sort of impulse sending source and where exactly to fix the Brantz unit so it is clearly visible (without cutting chunks out of the dash board or looking too much like a lash up).

The unit requires a Brantz sensor. Several types are available. The neatest solution is a small sensor that screws in between the gearbox speedometer drive output and the speedometer cable. Unfortunately, although two sizes are available, both have metric threads (18mm x 1.5mm for Ford/GM and 20mm x 1.5mm for Japanese cars). I'm amazed that no one has made a UNF version for British classic cars – there must be sufficient MGs and Triumphs to justify this, surely? Other sensors include wheel sensors or prop shaft sensors, though both are quite exposed to the elements. Electronic sensors are also available for modern cars.

For the MG Midget, the solution is to fit a Brantz Universal Speedometer Cable Sensor. This is a plastic unit that fits on a straight section of speedometer cable. The outer sheath is cut, a 13mm section removed, the cable passed through the device which replaces the segment removed, then back into the speedometer. The unit is clamped securely to both remaining portions of outer sheath with small fuel line clips, which make a neater job than jubilee clips. I mounted the unit about four inches behind the speedometer on a nice straight portion of cable run.

Brantz Universal Speedometer Cable Sensor

Fitting schematic from Brantz instructions

Sensor as fitted, just behind speedometer

The rotor within the unit floats in air, so as to put no additional strain on the speedometer. The speedometer cable passes through and is gripped by the centre of unit. The MG cable was quite a tight fit, requiring the guide hole to be enlarged slightly. The rotor generates five pulses-per-revolution of the cable.

Sensor fitted, the next job was to mount the Brantz somewhere. The first effort was on the dashboard in front of the passenger. A stainless steel bracket was fabricated to avoid drilling holes in the dash. Although serviceable, the angle of the dash, sloping away, meant the face of the unit was slightly obscured – a vertical arrangement providing much clearer visibility. The final solution was to mount between the radio (fitted below the centre of the dash) and the transmission tunnel, just ahead of the gear lever. This offers excellent access to the controls for both driver and navigator. However, it did require removing the radio unit (twice in the end) and routing cables through the bulkhead. A new stainless steel bracket was fabricated and fitted to the underside of the radio console, leaving space behind to store the Brantz remote control unit. The final result is quite pleasing.

Brantz rally trip meter fitted to MG Midget "ABW"

Thanks to Esme and Peter for the kind gift of the trip meter and thanks to Peter for assistance with the fitting. Now all we have to do is justify all this effort with a good result at the next rally.

Saturday, 12 November 2011

Clutch woes

After being laid up for a few weeks with drive-train problems, "ABW" is now back from the local garage and trundling around in the Autumn mist.  The lengthy time away was a result of a total and catastrophic failure of the clutch.

The clutch on the MG Midget can only be accessed by removing the engine... typical!  In most old cars the gearbox can be dropped to get to the offending item.  Being an engine out job, I determined that this was a little too much to take on myself (at least in an acceptable time-scale).

The clutch itself is quite a simple single dry plate affair.  It has a single drive plate with friction linings attached by rivets.  The centre (hub) of the plate slides on spines machined on the gearbox output shaft.  Drive from the plate to the hub is transmitted through springs to allow a cushioned take up of power.  The plate is sandwiched between the rear face of the flywheel and a spring-loaded pressure plate carried inside a cover bolted to the flywheel.  Drive is disengaged when the pressure plate is drawn backwards against the force of the thrust (pressure plate) springs.  This movement is activated by levers inside the cover, ultimately connected to the clutch pedal hydraulically.

Clutch components, 1275cc MG Midget

When the clutch pedal is pressed down, the clutch master cylinder forces hydraulic fluid through hydraulic pipes to the clutch slave cylinder.  A piston in the slave cylinder is connected to the pivoted clutch release arm by a short pushrod.  As the hydraulic fluid pushes the piston out, the release arm moves and the forked legs at the other end of the arm move forward against the clutch release bearing. The release bearing contains a carbon (graphite) block, that stands proud of its housing cup. This carbon-faced bearing pushes against the release bearing thrust plate.  The thrust plate actuates the three clutch release levers radiating from the hub which are pivoted so as to move the pressure plate backwards, so by releasing the clutch plate.  When the clutch pedal is released, the pressure plate springs force the pressure plate back into contact with the friction linings on the clutch plate and at the same time force the clutch plate against the flywheel (in the pressure plate - clutch plate - flywheel sandwich).

It was the carbon release bearing that failed in this instance.   The garage tells me that lumps of carbon fell out of the casing when the gearbox and engine were separated.  When the bearing failed the slave cylinder that actuates the other end of the clutch release arm over-extended, causing the piston to leave the cylinder and the clutch pedal to lose resistance and go to the floor.  The slave cylinder was replaced.

The failure came as a bit of a surprise, and occurred when Mrs C was driving the car. The clutch was a little noisy, but no more than the gearbox, or what one might expect from a car of this vintage. There were certainly no nasty squeals when changing gear,  a tell-tale sign of of a badly worn clutch release bearing.  However, I did start to get strange noises from the starter motor just before the clutch failed. This could have been caused by bits of deteriorating carbon bearing becoming stuck in the teeth of the flywheel and the starter motor pinion. The starter motor has been now been checked and seems okay.

We've now done over 1,500 miles since buying the car, in around six months.  Whilst this is not much by modern standards, it is still quite a lot for an old girl and a lot more than she was used to before I got hold of her!  Wear of the clutch release bearing is accelerated if the clutch is ridden or held down for long periods in gear whilst the engine is running.  Note to self:  remember to put car in neutral at traffic lights and junctions!

Thanks to Alan and the team at Darley Dale Garage for getting "ABW" back on the road.

Tuesday, 13 September 2011

Shakespeare Irregulars

Early September saw “ABW” take part in her first historic road rally:  The Shakespeare Rally, organised by A La Carte Rallies, and took place in the heart of England, near Stratford-upon-Avon,.

This was a regularity challenge over two days, designed to test each crew’s ability to maintain a precise average speed over a route requiring complex navigation on public roads. The idea is to provide a competitive event, without encouraging high speed driving.

Participating cars included Jaguars (E-Type, XJS, and Mk1), Porsches (356 and 911), Triumphs (Stag and TR4A), Austin Healeys (3000 and Sprite), Lancia (Fulvia), a Corvette, and of course an MG Midget!

Lined up, ready to go.  Le Mans start not necessary!

The target speed was 24mph (apart from a couple of slower narrow lanes), designed to maintain safety and protected cherished, and in some cases valuable classic cars. That’s the idea!  Sounds slow... perhaps a little tedious? Unfortunately, as soon as you’ve made a mistake or got delayed, you’ve got to try and make up time. Crews are being timed to the nearest second through several intermediate time controls on each stage, sometimes with secret controls located out of sight. At the end of the event, the team that has visited all these controls and who has the fewest early or late penalties overall is the winner.

Speed tables are used to accurately re-calibrate the speedo in the car, based on a precisely measured circuit (so in our case we were using 23.9 mph tables for this rally). Mrs C was navigating and checking average speed – the tables giving us exact times for precise distances (to the 1/10 mile).

Arguably more important is navigation. The rally used a series of ball and arrow diagrams to describe junctions where a deviation from “the ordinary course” was required, supplemented by clues and instructions that are not always obvious. The diagrams are usually referred to as tulips; not because they look like flowers, but because they first came to prominence in the Tulip Rally (Tulpen rally) of the 1950s. Getting the route wrong makes you hopelessly behind on the average speed, hence the importance of navigation.

“ABW” and the crew came a credible “not last” in our first taste of this type of event. This was despite missing one of the first turns and getting hopelessly off course on the first morning. Gradually we improved our accuracy and reduced the penalty points – even scoring a near-mythical zero on one section (completing the section to the nearest second at average speed).  The winning Jaguar MK1 team scored only three hundred penalties over the whole weekend; I think we managed that on one stage!

Approaching a control point

More importantly we had a great time, met some new friends and fellow classic car enthusiasts, and had an excuse to clock up a couple of hundred miles in the car. The navigating and regularity driving was mentally challenging, but good fun. Fortunately there was time to relax and recuperate each evening.  To top it all navigator and driver are still on speaking terms.

A great event that was excellently planned and executed by A La Carte Rallies. Bring on the next challenge!