Member postings for Russell Eberhardt

Decent quality chrome plating on steel always started with copper plating, then nickel, then chrome. It will then last a lifetime.

Russell.

Have you tried putting a dial guage on the side of the quill and checking the sidewards play?

Russell.

When I rebuilt my Atlas lathe I found that the ways were a couple of thou wider at the tailstock end than under the chuck. Not being confident of my scraping ability at that time I trued them up using a new carborundum oilstone, frequently checking the width with a mike. Although not the "correct" way to do it, it worked a treat.

Russell.

By all means polish the handwheels etc., but slides should not be polished. A slight surface irregulaity is needed to retain lubricant. Two flat, polished surfaces will tend to stick together. I would just use wire wool with a bit of oil to remove the surface rust.

Russell.

Sorry, it looks as if you're right. The wires from the windings are not connected correctly. Normally the main winding would be connected between U1 and U2.

Alex,

I would definately give the supplier a b******ing!

Russell.

.. or make the die blocks from PTFE?

Russell.

I see from your pictures that the six terminals are labeled but they can't easily be seen. The labeling of the terminals is more or less standardised. There is a helpful data sheet here.

Nick's suggestion to email the supplier if you are not sure is best. His suggestion to connect the mains across the connections with the bars is almost certainly incorrect.

I wish I could make a motor giving 1.5 hp for only 180 W input. It would make my fortune and solve the world's energy problems!

Russell.

I built one to GHT's design(The Model Engineers Workshop Manual by Geo. H, Thomas) but with the hole for the tool drilled at 40 deg. to the axis so that 1/16 of a turn of the 40 tpi adjusting screw moves the toolbit radially by one thou. It makes it dead easy to bore to size. The angled ttoolbit makes it easy to measure the tool bit radius.

Well worth the effort of making one for cylinder boring.

Russell.

Shouldn't that be anticlockwise (when seen from the front?

Russell.

A simple alternative to a hand rest for me is a piece of bar held in the toolpost but it must be close to the work for safety. Yes, use high speed and make sure your tool is really, really sharp.

Russell

Edited By Russell Eberhardt on 03/08/2012 15:54:25

It is difficult to simulate the spark gap because of the negative resistance when the arc first starts but it is perhaps the most important component. After all, the object of the excersise is to put energy into the spark in order to ignite the mixture.

Some real world waveforms with a simplified explanation can be seen here

Have fun and keep your fingers away from the high voltages

Russell

But keeping the workshop tidy is !!

Russell.

Good write-up and interesting site. Hope they win today!

Russell.

I think we are saying the same thing. Yes, of course it's the induced voltage in the secondary that starts the spark but what causes that induced voltage? The collapsing flux in the core in which the energy is stored.

As an aside, does anyone remember the fashion for capacitor discharge ignition in the 1970s? In those systems the energy was stored in the capacitor but to get enough energy stored it had to be charged to a high voltage by an inverter. I built one to a design published in "Wireless World". They had the advantage that the charging time was shorter and so would work at higher revs. I believe that they are still used on some small engines - perhaps that system could be usefull for models as they can be made more compact.

Russell

Hi Martin,

My point was that it is the energy stored in the inductor that creates the spark. Before the contact breaker opening the capacitor has no stored energy. What you are seeing in Andrew's simulation is the energy being transfered back and forth between the inductor and the capacitor after the points open.

He has not simulated the spark gap so no energy is lost in the spark and the ringing continues with losses, mainly in the inductor, absorbing some of the energy on each cycle.

I no longer have Spice installed on my computer so can't show you a fuller simulation but if Andrew wants to continue he will find a simple model for a spark gap here.  In practice it is more complicated as the spark gap displays negative resistance when the discharge starts.

I'm afraid my grey cells are getting a bit sparse as well

Regards

Russell.

Edited By Russell Eberhardt on 26/07/2012 10:09:18

Edited By Russell Eberhardt on 26/07/2012 10:17:43

Martin,

Think about it like this:

The spark occurs when the points open. At this point in the cycle the capacitor voltage has been held at zero by the closed points so it has no stored energy. On the other hand, the inductor is passing a high current through the points and thus has energy stored in its magnetic flux. It is this ebergy that creates the spark. The main purpose of the capacitor is to restrict the rate of voltage increase across the points and prevent arcing across the points.

Hope that helps.

Russell.

Nice work Andrew.

However, in practice, the case with the capacitor may look very different as the sparking plug gap breaks down before the peak voltage is reached and draws energy out of the resonant circuit. Thus the ringing effect will be reduced.

You could simulate that approximately by adding a high voltage zener diode as the spark gap as I doubt your simulator includes spark gaps.

Russell.

I've given up on layout blue. Unless it is used up quickly it gets thick, clogs up the brush and glues the lid to the bottle. For me marker pens are much better especially for fine work such clock wheels. they show up fine lines really well.

Russell.

Why are you using a "buzz coil" as opposed to a conventional contact breaker system. I thought buzz coils (or trembler coils) went out with the model T Ford.

Russell.

Peter,

The normal technique is setting the rest to a degree or two from the side of the wheel so the tool being ground is normally only in contact with the corner of the wheel as it's advanced. Sometimes however, such as for drill grinding you do use the side of the wheel but carefully - don't apply too much pressure.

As everyone says though a cup wheel is better. I keep a white 60 grit cup wheel on one end and a diamond wheel on the other.

Russell.