Member postings for John ATTLEE

Dear All,

I predominantly use the four-jaw independent as it is more flexible as I can chuck round, hex, square and rectangular. I used to take ages to dial the work in but with practice I can now do it very quickly. I do quite a bit of work using square stock.

I also use the Hopper method but with a deviation which I will eliminate in future. What I was doing was finding the jaw with the lowest point on the dial, holding it at the 9 o'clock position, setting zero, rotating 180, taking the reading from the dial gauge, setting zero to half of the reading, release the back jaw just the right amount, tighten the front jaw one thou too much (ie less than zero) and then tighten the back jaw to bring back to zero. I would then correct the other pair of jaws but would inevitably have to rest zero at some point in the process.

Hopper's method is superior because it determines the correct 'zero' immediately and should be even quicker. I can't wait to try it!

John

Dear All,

Going back to the cost of the Hall switch, we are not comparing like with like! I should have said that I was considering the Honeywell 4AV series VANE switch. This would enable me to position the 12 switches accurately so that the 12 cylinders would all fire at the correct moment. Instead I used the Sharp GP1A51HRJ00F photo transistor which has a similar mounting arrangement but is much cheaper

The IGBT is about £1. You need a 1K resistor between the Hall switch and gate of the IGBT. Provided there are 3 ms of time available to charge the coil up, I don't see what the advantage of a sizeable CDI package is. Clearly the Hall switch is a huge improvement over the points system which is a failure waiting to happen. Does the CDI give a higher voltage spark or a fatter one?

John

Dear All,

For many years I have been working on the REME Museum's Rolls Royce / Rover Meteor M120 petrol engine fitted to the Museum's Conqueror ARV. The Meteor is an automotive version of a Merlin engine.

I have developed what I have named a "Discombobulator" and is applicable to a magneto or coil and distributor system.

The rotor arm and points etc are replaced by a rotor / chopper disc that has a transparent sector. As many photo transistors as there are cylinders are accurately placed radially around the circumference so that the chopper disc switches each photo transistor on and off. The angle of each sector is arranged so that the coil will be charged for 3 milli seconds at max desired RPM.

The mechanical (and vacuum advance if fitted) mechanism is retained and works in the usual way.

Current through the coil is controlled by International Rectifier, Ignition, Insulated gate, Bi-polar Transistors, (Ignition IGBT), type IRGS14C40L. Again, there are as many IGBTs as cylinders.

When the photo transistor turns the coil "ON" via the IGBT, the coil is charged up. When the photo trani turns "OFF", the IGBT stops the current going through the coil and a rather large spark is generated.

I am using six Renault Clio, four cylinder coil packs for the V12. The IGBT takes care of all the nasty high voltage spikes. Obviously, there is no HT distributor. There are two plugs per cylinder which are fired at the same time by the same coil.

I could have used Hall Effect switches but with 12 of them at about £15 each, they were too expensive.

I am pleased to say that the system works very well indeed.

Neither the Meteor nor the Meteorite (the V8 version) have any form of vacuum advance, so timing is independent of load and is only controlled by a simple mechanical advance system. I think that it is inconceivable that an improvement in torque and fuel efficiency cannot be achieved by carefully mapping the advance curve. My next development will be to mount the base plate with the photo transistors on a baseplate running in bearings. The position of the baseplate can be controlled by a servo motor or stepper motor controlled by an Arduino and suitable driver.

I would describe a Discombobulator as an ignition system comprising a rotor, position sensors, IGBTs and coils for each cylinder. Sensing can be by photo transistor or Hall Effect. The system can operate at crankshaft speed using the 'wasted spark' system.

I should point out that the Meteor M120 already has electronic fuel injection controlled by an Arduino using the Speeduino system.

John

I would normally do exactly as Emgee has done with DRO. I find DRO on the Z axis very useful. However, I have done it by taking the blade out, touching off the appropriate surface of the arbor. I then raise the table by the appropriate amount (half the blade dia + half the head or a useful bit of round HSS bar 3/8 dia). Seems to work fine even with me!

John

We are not providing professional advice under a contract. Unless we were grossly negligent, I cannot see how there can be a problem. If one of us did give such bad advice it would only be a few micro seconds before we were shot down by someone else on the forum.

John

Dear All,

In my, albeit limited experience, 3 axis DRO provides at least a 100% increase in productivity whether on a lathe or milling machine. I would have thought that the DRO would be more reliable if fitted by the factory or supplier.

John

The other difficulty is that there is no standard protocol about when or how the batteries are isolated after an accident. Since the voltages are quite high and DC, this is a bit of a problem. Surely the batteries should be required to be isolated if the air bags go off.

John

Dear All,

This thread has motivated me to re-commission my Picador drill grinding jig. I will make a similar base.

What a shame that it has been produced with such cheap and coarse screw threads.

John

I am between Petersfield and Portsmouth. I have a Victoria U2 milling machine.

Why not make some tooling (which might need a milling machine) and line bore using a lathe with the line boring tool running between centres and the tooling replacing the compound slide? That should keep the set up time down.

Happy to chat on 'phone.

John

What machine is it for and do you know what caused it to fail. Is the hardening to resist the wear or to increase the strength? How come only five internal splines are stripped? I would have expected it to be all or none! Is the shaft 150 mm long or is that just the length of the splines? How long are the internal splines? What is the form of the spines?

John

The last guides I made was for a JAP engine. It was easier to make new guides than mess about trying to find NOS ones. I used PB because it was what I had in stock! The engine would only be running very few hours so life was not an issue. So useful to learn of better materials on a forum.

John

Surely, the seat will have to re-cut the seat in any case. I use an engine machine shop because it is so cheap it is not worth doing myself. I recently had a problem with a side valve continental engine in a Hyster forklift. It was not worth taking the engine out to take it to the machine shop. Fortunately after the valve guides were replaced, and after a quick grind, the valve faces and seats were fine.

John,

I have made valve guides out of PB using your original technique with poor equipment and my limited skills and it was fine. If you did the ID first and then had the arbour running true, it is hard to see what could go wrong.

John

Compared to most on this forum I am a novice with a 1950s Denham DL lathe. I used to use a three jaw but I now normally only use the four jaw. I have found with practice I can get the bar to run pretty true within about 40 seconds. The 4 jaw has the advantage that it can take square or rectangular bar. I do use the 3 jaw for production of several identical items.

Whilst I can take out the eccentricity with a 4 jaw, run out at a distance remains a problem. I am now starting to machine between centres with some success.

I thought that the experience of a relative novice might be helpful.

John

I expect that "AM" is Air Ministry.. I have a Denham DL6 or 7 (I can't remember which. It is quite slow and TC insert tools are not supposed to work with it. They do! Productivity is significantly improved with 2 axis DRO.

John

Dear All,

I use synthetic paints for my classic commercial vehicle projects. Cellulose thinners will ruin any synthetic paint if you mix it with it. However, this property makes it very good for cleaning brushes and spray guns because it breaks the paint down. I quite often use white spirit for economy. For a really good job I would use the correct thinners from the paint manufacturer.

John

Dear All,

I know that, in theory, my Denham DL6 with plain headstock bearings and very low RPM should not benefit from carbide insert tooling but it certainly does! I use a combined tool post and tool holder and this means that the cutting tool is always at the right height. Obviously, I run it in top gear unless the work is more than about 3" in dia.

I can turn or bore to about a thou. The machine is fitted with a three axis DRO system which I think is essential to make up for my limited skills. I use three passes to eliminate 'spring back' and obtain a consistent size to be measured. Thereafter, the DRO displays the correct dia, after three passes have been taken. I would not hesitate to advance the tool just a thou.

I certainly achieve good enough results for my automotive work. I very rarely use HSS cutting tools in the lathes now.

John

Nigel,

Regarding you original problem, I have had this very one myself but with a full size tank transporter trailer! Try "Insert" and then select "Extenal Reference" which will allow you to access your other TurboCad files ie drawings,

I found that none of the usual copy and paste techniques worked.

John

I think that it is a Petter AVA1 as I had one many moons ago.

John

Don't even think about it. That crane will be designed so that everything is only just strong enough for its task. Keep your crane for what it is good at. If you need to lift something heavier, hire the right equipment for the job.

John