Member postings for John Fielding

Hi Martin,

You're welcome. I was involved with the Chrysler SBEC some years back and it also has some other funny quirks.

In North America in winter cars spend a large portion of the day in traffic queues and when the air temperature is around freezing with an engine warming up you get condensation on the radiator core which turns into a mist. Seems Chrysler got complaints from owners that when waiting at an intersection the steam rising off the radiator had some drivers convinced a hose had a leak. It was normal physical thing like sea fog. So to stop worrying the drivers Chrysler programmed the SBEC to turn on the radiator cooling fan at max rpm to blow the mist away under car. This was despite the fact that engine wasn't anywhere near operating temperature. The end result was increased cylinder wear as the engine never reached its correct temperature. Everyone in ivolved with the SBEC heaved a big sigh of relief when it was finally canned.

Final part:

One thing was that now they could sort of measure the battery temperature with some degree of accuracy, they could adjust the battery cut-off voltage the alternator supplied to suit the conditions. In North America it gets very cold in winter and batteries when very cold need a much higher charging voltage, similar in blistering hot places like Phoenix, Arizona you need to reduce the charging voltage to prevent overcharging. The Achilles Heel was the tiny temperature sensor was an el cheapo part and they failed by the thousand after a couple of years. A classic case of the bean counters stuffing up an otherwise good design. They replaced a $5 component with a 50c component and in the end lost tens of millions of dollars in warranty claims!

This failure of the sensor meant the engine computer went berserk and buggered up the fuel and ignition timing, so the car ran like a sick dog. That wasn't too serious as the computer had a backup mode called "Limp Home" where the engine was provided with some very basic setting so you could drive it, but not very far!

The biggest problems was the bit of the computer code that did the alternator control, it thought that the car was sitting in an environment of -100C. So it looked up the values you would need to charge the battery at that temperature and discovered it would need 22V and set the alternator to give that output voltage. Of course the batteries either exploded or split the casings and acid corroded everything in the engine compartment and in a few cases the car caught fire. Chrysler had to ditch the SBEC as it lost sales big time with its reliability issues.

Seems my post was too long!

The voltaic cell, to give it the correct name, consists of two separate items. They don’t actually exist in a real battery but the standard cell model consists of a voltaic source which can provide current into an external load. In the model this is a constant voltage source that can give infinite current with no drop in the voltage. The theoretical perfect cell. However, the losses incorporated have to be described and the normal method is to include a series resistor that changes its value with the state of charge. We call it an ESR, equivalent series resistance. When the cell is fully charged the ESR is in an ideal cell zero, but as the capacity is depleted the ESR increases, at some point the ESR is too large to allow sufficient current to flow and the output voltage decreases. This explains why the battery voltage drops when a heavy current is drawn.

The lead-acid cell has a reversible chemical reaction. When the cell is fully charged at about 2.5V per cell the chemicals have all been forced into one mode. But as current is drawn off the reaction begins to reverse and as the capacity decreases more of the chemical revert back to the discharged state. We can get a fairly accurate indication of the state of charge by measuring the density of the electrolyte with a hydrometer. A fully charged cell has denser liquid than a discharged cell. Sadly today car batteries are no longer open, so using a hydrometer is no longer possible.

Because the ESR varies with the state of charge then when the battery is fully discharged the ESR is maximum. So when the battery is placed on charge it is difficult to push current into it unless you increase the charger voltage. Batteries when very cold have very high ESR values and when very hot it is much lower. So the charging voltage is very dependent on the battery temperature. So when the charger is first connected the current is quite low. As some of the capacity is gradually replaced the ESR begins to fall and the charging current climbs to some maximum, and at the same time the battery voltages also rises towards the fully charged state. As the battery voltage approaches the charger voltage the ability to push current into the battery gets less and less. When the battery voltage and the charger voltage are the same the charge current is zero. But all lead-acid batteries have an internal loss mechanism and that is why if they are left unused but charged, they slowly lose capacity. So when the battery is nominally fully charged a small “trickle charge” current flows to make up the continual internal loss. Hence, why it is called a trickle charge. So when charging a battery in order to supply the correct charge voltage you have to know the battery temperature and what voltage to apply for that particular battery. There is no “one size fits all” with batteries!

If the charger cut-off voltage is set too high you overcharge the battery and boil off all the electrolyte and the battery is scrap. Again it is very fine line between just the right voltage for those conditions and one that is too high or too low. Chrysler in the 1980s went through a horrible period with "clever battery charging" technology" where they attempted to measure the battery temperature under the hood. Although in principle it was a good move the way they went about it was flawed. The battery sat directly in front of the SBEC computer near the radiator grille. SBEC is short for Single Board Engine Computer and for the first time it integrated all the engine and peripheral electronics onto a single printed circuit board. On the SBEC was a temperature sensor to measure the air temperature flowing into the engine inlet manifold. The SBEC was a box with rubber air hoses at the two ends, the air for the combustion flowed through it after the air filter, so by measuring the air temperature the fuel and ignition could be computed to get the lowest emissions, a good plan but it failed terribly. The whizz-kids at Chrysler tried to make the SBEC do everything that normally individual electronic boxes where dedicated to do.

I am a battery expert and most of the things some people know about batteries is dangerous!

A standard lead-acid battery terminal voltage is nominally 2V per cell. A 12V car battery consists of 6 cells connected in series and hence is nominally 12V. But when fully charged each cell rises to about2.5V maximum. Measuring the open circuit (no load voltage) tells you almost nothing about the battery condition or state of charge. A 12V battery when taken off charge might read 14.0V but after it has stood un connected overnight it will read as little as 12.5V. That is perfectly normal.

In my experience most (not all) of trickle chargers on the market can do more harm than good. In the battery world there are two distinct different types of chargers, cyclic chargers and standby chargers. A car battery is classed as a SLI battery (Starting-Lighting_Ignition) and is designed and made to be float charged by the alternator with a well controlled cut-off voltage. Batteries for caravans which are not charged from the vehicle but charged at home and then used later, are classed as cyclic use batteries, same as fork lift truck batteries. When they are discharged they get put back on charge. It is the same as petrol in your car. When the tank gets low you stick some more in it!

Another type of battery is the traction battery used in golf carts and fork lift trucks, these are also classed as cyclic battery use. They get charged, used to discharge them and put back on charge. Each type of battery uses similar construction and sulphuric acid. They look identical but the subtle difference is the way the plates are made.

In a SLI battery the plates are paper thin, this is to maximise the plate area as thin plates allow more plates to be stacked to give greater area. The next battery is the traction battery which has thicker plates and so less area for the same volume and finally the so-called Deep Cycle batteries which have the thickest plates and so the less area.

The ability to supply high peak currents for short periods is a function of the plate area. SLI batteries have the ability to give high current for short time period. The problem is the thin plates although they allow short bursts of high current, for starting, they cannot give the current for an extended period as the plates overheat and buckle. In automotive applications you only use the top 20 or 30% of the total capacity of the battery during starting and as the engines runs the alternator immediately bangs the charging current back into the battery to top up the tank.

Traction batteries have less ability to give high peak currents but can deliver a moderate current for long periods before they become discharged.

Deep Cycle, or whatever fancy name you choose to call them, have the lowest ability to give high currents. They are designed to give a medium to low current for extended periods, they are not designed to be used as a SLI application.

Now each of these types of battery require slightly different charging methods and cut-off voltages. A typical manufacturers will give details in the data sheet. For example, National Panasonic who supply batteries for just about any application and size or capacity, recommend cyclic use batteries to be charged to 14.0 to 15.0V, whereas for Standby Applications they recommend 13.5 to 13.8V. Standby is also known as float charging and is what car batteries used designed for. The majority of the vehicle current is supplied by the alternator and the battery only has to get involved if the current demand is more than the alternator can handle.

Generally there is no harm in leaving a SLI battery on permanent trickle charge provided the charger is the correct type. One of the other little quirks of lead-acid batteries is the operating temperature. When the battery is very low in temperature its ability to do the chemical reaction is slowed down. It sis the reversible chemical reaction which allws us to discharge a battery and then by putting it on charge to make the chemicals go back to their original state, we call fully charged. Unfortunately the terminal voltage tells us very little of any use. A battery when it is discharged will have a slightly lower voltage than a fully charged - under identical temperature conditions- but that is almost impossible to arrange in simple tests. The one thing we do know is the amount of charge current gives some indication of the state of charge, that is how much of the total capacity we need to replenish to get the battery to 100% charge state. A fully discharged battery if you measure the voltage might be 11V and when you connect the charger you would expect it to draw maximum current. But it doesn't do this for a very simple reason.

Edited By John Fielding on 13/03/2016 08:03:40

Hi Iain,

The bearings mentioned by Ian Phillips sound like the 608 series, very cheap and readily available. They are 8mm bore, 22mm OD and 7mm thick. I use them in several places and they last forever. The 608ZZ is a metal dust shield version but the ones I can get at a bargain price is the 608RS which is a fully sealed type with rubber oil seals on both sides. The plain version is simply the 608 which has not seals at all and is designed to run in oil.

A slightly smaller bearing is the 626 series, these are 6mm bore, 19mm OD and 6mm thick and also cost next to nothing. They are the cordless drill front bearing type so are also freely available from a bearing stockist. Again they come in ZZ and RS version as well as the plain 626.

A rule of thumb is for bearings that are well supported and force fed with oil, like car crankshafts etc, then 0.5 to 1 thou per inch of diameter is recommended. For drip fed bearings and ones where some misalignment can occur due to flexing etc, then 2 thou per inch in diameter is the minimum and often a lot more is required. On locomotive crank pins and axle boxes for example the bearing clearance is often as much as 1/16-inch to 1/8-inch total, that is on the full size jobs of course. The problem is you cannot scale nature so if a shaft needs 5-thou on the full size engine the model will need about the same!

The rear wheel bearings will need the most clearance and the crankshaft a little less, what the exact "ideal clearance" is is a moot point. You have to go with the best thumb suck and see what happens. If things bind then give it more clearance.

From the pictures I would say the bronze bush is toast! The spindle is very hard steel and hardened even more by heat treatment, so it will be able to polish it or even a tiny bit of grinding by a company who specialise in this type of work.

If it were my lathe I would bite the bullet and buy a new bronze bush and have the spindle touched up. Scraping isn't an impossible task to do at home if you take it slowly and know what you are doing. But pictures can sometimes lie!

I have never had to press out the bronze bush in a Myford but I think it could be done in situ with a big bolt and some spacer collars machined up to fit the bush exactly. It will probably need a fair bit of Sunny Jim to get it out and the new one into place.

Spiral point taps are designed to be used in CNC milling/drilling/tapping machines. One tap does all jobs and they are stronger than hand taps. Great for holes which pass right through the material, but not so good for blind bottomed holes. For this you need to provide extra hole depth and stop the tap at the required depth of thread, easy to program on a production line.

Spiral flute taps are like a twist drill and have a helix type groove. Typically that are needed for tapping threads in aluminium extrusions where the cored hole isn't a full circle. A normal straight fluted tap would hang up on the slot in the hole and snap. Again they are designed to be driven by a machine, although they often have a square tang to take a normal tap wrench as well. Production spiral point taps are a parallel shank with no square on the end. Designed to be held in collets. Some special machine taps have the pilot drill and tap combined as a way to speed up production. But you are unlikely to find these in a normal tool merchants stock. This type is widely used in the mazak casting manufactured items like carburettors etc in the older days.

Hi Jonathan,

I had to pull the spindle out to replace the two angular contact bearings in the rear housing. They were pretty shot and made a crackling noise at times. That told me they were beginning to break up. I shopped around and finally located a pair from a competent bearing supplier. The original Hoffman bearings had a different part number but the new ones were cross referenced after a lot of effort on the Internet.

The correct ones are the most expensive in this series, as they have very tight tolerances. Being an imperial bearing they are hard to find and not made by many manufacturers today, hence the high price, In UK money they were about 25 pounds each. Some folks have fitted common or garden taper roller bearings, which are a fraction of the price, but I wanted to put the best possible bearing into the lathe. The originals had lasted since 1971 when the S7 was made so I can't really complain! Some dumb previous owner had packed the bearings with gungy grease but the bearings are designed for oil lubrication.

Hi Brian,

Since I have installed a homemade full flood cutting fluid system I now use the Locline to hose down the bed and slides after use. The nice thing about soluble cutting oil is it is a really good lubricant and the water evaporates leaving a thin film of oil on the bedways. So no rusting takes place and the extra little oil finds it way into all the nooks and crannies.

One point about the Myford ML7R and Super headstock wick oiler which you are probably unaware. If you pull out the spindle you have to pierce the wick with a sharp scriber or darning needle to stop the spring pushing it upwards when you draw out the spindle. There is a 2BA grubscrew you take out and then force a sharp pointer object into the wick, bofore you try and pull the spindle forwards. However, you will see when you have the spindle out and the bull gear that the hole for this 2BA screw is drilled right across and exits the casting next to the bull gear. So although you think you are flooding the tapered bearing when you pump oil in through the oil cup, most of it drops down through the hollow casting into the drip tray. How did I find out?

Well when I pulled the spindle out of my S7 I also removed the bull gear and then pulled the wick out to inspect it. When I came to put the wick back in place I held the wick down with my fingers and as I pushed the darning needle back into the wick if punctured my thumb!

I managed to find the pictures from when I made the modifications to my S7. Date stamp is Nov 2014, doesn't time fly when you are having fun!

Now I recall the tailstock needed two oil nipples as it wasn't possible to cross-drill the bottom block. The oil nipples have to close to the rear of the tailstock so they don't clash with the saddle when working right up to it. You will see if you push the tailstock up the saddle that it comes a fair way back along the sides of the tailstock.

The saddle was ground on the working faces and then I cut the new oil grooves. The exact placement isn't too critical, but the intention was to get the cross grooves as close to the outer sides as possible so some oil can get to the vertical shears. The original oil grooves leave a large part of the slideways starved of lubrication.

On my saddle the portion at the front looked like corduroy trousers where the swarf chips had become stuck and abraded the cast iron. Hence, I had the saddle working faces surface ground to remove these imperfections. This is another reason to improve the swarf guard to improve the wiping action. Without the swarf felt wiper the saddle acts like a vacuum cleaner and the dirt gets pushed under the saddle to cause mayhem as the normal oil grooves cannot flush out the muck. It just made a lovely grinding paste!

Oil grooves in tailstock base

The other modification which prompted all of this work was the tailstock riding upwards as it has no positive vertical clamping apart from the bed locking clamp. When the tailstock gets a bit worn as you slide it along the bed it is possible that the top portion rides up slightly and a piece of swarf can get into the gap at the front. This causes the barrel to tilt upwards and upsets the centering. So I made an additional clamping arrangement. Note this modification is not for the faint hearted as you need to drill some holes in the castings, but with care it is not too difficult to do and the end result is worth the effort. If anyone wants the details then just shout. You can see the additional clamp bolt nyloc nut in the picture of the tailstock base.

Extended oil grooves in saddle

A couple of pictures of my Myford S7 swarf guards. The tailstock has an oil nipple added and this is cross drilled right through the casting to near the back. Then two communicating holes go down to the slideways and a 2mm wide groove is milled almost the full length of the slides on both sides. When you apply the oil gun oil floods out all the way around the surfaces driving out any rubbish.

I did a similar trick with the saddle. The original oil grooves stop too far from the vertical shears so they get starved of oil. I extended the grooves and put in some cross grooves to let the oil get to more of the working surfaces. Note on the saddle picture how the inner vertical shears have a wiping pad to stop the swarf adhering to them. I will dig out the saddle modification pictures later and post them.

Tailstock wiper modification

S

If you think brass swarf is bad, try machining a lot of cast iron. Those pesky tiny fragments get everywhere and find their ways into most chucks. A regular ritual here is at New Years I strip and clean all my lathe chucks and properly lubricate them. Makes a huge difference to smooth working and accuracy.

I had an old and battered Burnerd chuck off the Super 7 which would never hold true and felt rough when I adjusted it so hid it away in a cupboard. I assumed it was simply worn, so that was chuck #1 to get the treatment, so I could figure out how the do the rest. Surprise-surprise it is now almost as good as my expensive replacement. It was full, and I do mean full of swarf from countless years of use. The grease was like concrete. Hence, the anal fascination with cleaning all the chucks in the workshop!

I think that is the Dikes engine, designed by an eccentric American. At one time they were popular as steam winches on boats IIRC.

Yep! Did that to my Super 7 a few years back and posted the idea. Interesting to see how the internal shears have worn where the top of the tailstock slides don't go full depth. I always considered that a poor design. I also did the saddle with the same idea, you need to sweep the swarf not only from the top of the ways but also in the gap. I never understood why Myford neglected this fact.

The other thing I did was I milled some oil grooves on the underside of the tailstock and cross drilled the bottom casting to allow the oil to flow to all surfaces. Did the same on the saddle and now when the oilgun is applied you can see the oil coming out all around the saddle. Makes a huge difference as you can flood the slideways with aoil and push out all the gunge that normally collects!

Last year my good lady was visiting the UK to see the daughter and grandson, so I having to stay home at the ranch and keep the doggies company, looked at the various suppliers websites and made a few purchases.

Postage from the UK to South Africa normally costs more than goods cost. And in many cases just disappears in transit never to be seen again. So good lady did her usual trick and took two suitcase, one inside the other and brought back two full ones! Best part was the free carriage and the excellent speed of delivery. Ordered one item in the morning and it was at the daughters house by mid afternoon. We don't get that sort of service here.

One of the purchases was a QCTP for the Myford Super 7. I had been promising myself one for a while and Chronos had a suitable set on special, so I jumped in. The previous time they were out of stock so I had to bail out of the purchase. When good lady arrived home all the items were unpacked and inspected. The TC tipped lathe tools were considered a bit iffy but usable with some regrinding, not Chronos supplied but AN Other supplier, who I will give a miss in future. But to be fair for what I paid I wasn't expecting Brown and Sharp quality!

I finally came to fit the new tool post and had to make a slight modification to the Myford top slide, as I knew I would having firstly studied the ones on offer, but it went smoothly and it was all back together and working in a couple of hours. What a pleasure not having to faff about with shims and old bits of feeler gauges to set the tool height.

Then I noticed there was a small hole which was designed to take a dowel pin for indexing the top part. I thought that would be a good addition so planned to drill a row of holes in the top slide to set definite angles, but it was not to be!

Measured up the hole, which is narrower at the bottom than the top, and decided I needed to ream this hole to something I could use. It was a tad under 1/4" and bigger than 6mm, sort of in between oddball choice I thought, I schemed out a spring loaded pin effort that I could just pull up to retract the dowel pin when I slackened the centre bolt so I could rotate it simply. So I applied the 1/4" hand reamer expecting it to easily walk through the block. Not a chance. The metal is really tough and hardened, the reamer wouldn't even touch it, it was so hard, which surprised me until I realised who the manufacturer was. The box said Soba, but it is actually Shobha, which is a well respected company jn India who make a whole variety of machine tools and accessories. One of the largest ball bearing manufacturers in the world is based in India and Tata Steels is by far the largest steel manufacturer in the world.

So when you assume the stuff is made in China (everything is made in China these days - is a common cry) well you may be wrong. It is more likely to be made in India.

My precision 3-jaw chuck is made in Chezk republic and it is superb, holding its tolerance over many years of abuse and it wasn't expensive when I bought it here about ten years ago,

Edited By John Fielding on 08/03/2016 15:37:15

I must remember when next I go to buy some new fluorescent pipes to call them tubes!

Stainless steels are not all non-magnetic. Of the three common types two are fairly magnetic and one in almost non-magnetic.

The tale I will relate might have some relevance to all those who use CAD to make diagrams and parts for projects. If nothing else it makes us think before issuing a drawing!

Many years ago I was gainfully employed by a large concern that designed and manufactured military equipment. My forte was a RF Design Engineer and I had several projects under my care, both in development and in full production. Once you release a product onto the shop floor it becomes your personal "enfant terrible" and can haunt you for as long as it remains in production.

One day I received a call from a production operative on the shop floor giving me a heads up that there was "trouble at mill" brewing. When I asked which product was the cause of the current trouble he told me. But that product had been running for years and never gave any problems. After the initial teething troubles whilst the operators learned how to assemble and test the new animal things ran smoothly. So I was very surprised to hear there was now a problem.

My informant said it went deeper than that as there was a possibilty that all the production over the last few years might be affected. Horror thoughts like vehicle recalls to replace some parts at great expense went through my mind! Did I stuff up when I designed it?

Then my informant let me down gently, the new inspector on the line had rejected all the production for the last week and nothing was going out of the door and they wouldn't accept the word of a "nobody" to tell them to release the product for shipment.

Well, I put on my running shoes and made haste to the shop floor. My office was in a separate building removed from the factory and it took me a few minutes to get there. When I arrived a huddle of concerned people were gathered around a large table with the last few days production stacked on it. Each and everyone one of the finished items had a red label attached with string which bore the depressing words "Rejected".

I asked who had rejected the items and was shown to the door of the new inspector. He was a polite but firm gentleman who told me he couldn't pass the items as they did not conform to the drawings he was issued with to inspect said items. I was gobsmacked!

I asked him to point out what deviation there was between the finished items and the drawings. He informed me the screw slots on the items did not correspond with the assembly drawings and since the two differed they were not exactly to drawings, hence they failed! When I asked if the items actually worked and met the specification he informed me that apart from the screw slot problems everything else was perfectly in order.

When I told him the screw slot orientation was merely diagramatical and not meant to imply the screw slots had to be exactly as drawn, he agreed. But he also pointed out that the inspection drawings did not say this!

Apparently the others had made the same noises but he dug his heels in and wanted it from the "Design Authority", which would be yours truly. I told him he was perfectly correct, the items offered for inspection indeed did not comply with the supplied inspection drawings and I would immediately issue a temporary change note so the items may be passed for shipment. In that case he told me as soon as he received a copy of the works order informing him that a change note was to be issued he would release the items to the shipping department.

Although I could have, and was quite entitled to, give him a verbal b*llocking" for wasting our time, that would have been the wrong thing to do. He had made a very valid point, which if he had made the suggestion through the normal channels would have most likely been ignored. He showed us that there was a valid point, as the customers also were issued with the same inspection drawings so they could check goods delivered conformed to specification and if they had troubled to inspect with as much care as our man did would have been quite correct to reject the delivered goods. This would have been a highly embarrassing situation.

Although this is a silly and trivial occurrence it made me think about how we often take things for granted and don't give sufficient thought to the consequences. The upshot of this little "trouble at mill" was a directive issued by the Chief Engineer that in future all assembly and inspection drawings must add a note that "Screw head slots are purely for indication purposes unless noted otherwise". Problem solved!