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Member postings for John Haine

Here is a list of all the postings John Haine has made in our forums. Click on a thread name to jump to the thread.

Thread: Win10 Home / Linux LAN - anyone got one going?
14/08/2018 07:02:48

Google Drive, or similar cloud storage?

Thread: Lathe tool angles
13/08/2018 17:13:04

As to speed, you can turn brass faster.

13/08/2018 17:12:35

I use a tangential tool - Diamond Tool Holder - ground to the standard angle for brass as well as steel, it isn't a problem. It may be a problem if the brass you are turning is a very sticky grade, but all the brass bar I've had is clearly hard brass and I've never had a dig in.

Thread: Peace Flame
13/08/2018 17:09:32

The auto-changeover might also be problematic as the pressure from a propane cylinder hardly changes until it's empty as the liquid evaporates. Wouldn't it be easier to just connect the cylinders in parallel with both valves open?

One thing that does affect the pressure is temperature, as the latent heat of evaporation has to be supplied by ambient heat. Propane is I believe reputed to be more affected than butane. I guess if you have a pressure regulator that should avoid problems except at very low temperatures when the cylinder pressure may be too low to regulate. Even in the UK I believe that this can make winter caravanning problematic.

You will also need I think a flame failure device so that if the flame does go out the gas flow is stopped - I recall that some of these used to have a sensitive solenoid operated by a thermocouple, I don't know if these are available and suitable for propane.

Ages ago I did a little bit of consulting for British Gas Research on microprocessor controlled gas cookers. As gas cookers are popular because they still work in a power cut, there was interest in having something not needing mains. One idea we had was to use the pilot light to generate some electric power using a thermopile, question was whether a pilot could generate enough power. It turned out the the relevant BS required that the minimum pilot light had to dissipate the BThU equivalent of 250 W! Even if we could only get 1% efficiency we could have 5 volts at 500 mA for our electronics! Shortly after that pilot lights were banned in new appliances - 10 million homes x 250 watts being 2.5 gigawatts! We looked at all kinds of ideas to generate the power, my favourite being a stirling engine.

Thread: Facing Error
13/08/2018 09:50:57

I have always understood that lathes are built/adjusted to face slightly concave as that's better from a fit p.o.v. than convex, and this is done by slightly offsetting the headstock but having the cross slide perpendicular to the axis. So this may indicate that the h/s has too much offset.

Thread: Machine cleaning
13/08/2018 07:16:49

Try Muk-Off? Good for bikes and alloy wheels. Halfords.

Thread: WM18 Earth Fault - Looks like Controller blew
11/08/2018 22:29:00

If you have had it only a few months it is THEIR problem, not yours. I would suggest that you are careful not to do anything that dilutes their responsibility for fixing this.

Thread: What is this piece of Engineering - Model Aero Engine ID please?
11/08/2018 19:47:41

Crankcase of a model aero engine.

Thread: no recoil
10/08/2018 20:53:08

Dick, those points have been covered. There's a direct observation that there's no recoil which would be consistent with at least one of not both impulse faces being on the wrong centre.

10/08/2018 15:13:21

Yes, though recoil is a side effect of how the anchor escapement works it is a sign that it is doing the right thing. If the pallet faces are circular arcs and there is not recoil it shows that the axis of the arc is in the wrong place. I fear the solution most likely to succeed is to make a new anchor.

Thread: Can this motor be reversed?
09/08/2018 20:18:59

I guess you'd agree that if I just reversed the mains connections to the whole motor, it wouldn't reverse? So if I reversed the connections to the run winding and also the mains connections, it would be exactly the same as if you reversed only the connections to the start winding. So you can swap over either but not both.

The key thing for the OP is to look at the motor, not the capacitors, and check that both ends of each winding are accessible.

Thread: Small Brushless Motors - can they generate?
09/08/2018 18:56:48

I don't think it's quite that simple is it Dave? If you just let the HE or opto device generate a pulse then the pulse width and rate are both inversely proportional to speed, so the average is constant. You need to allow each sensor pulse to trigger a constant width pulse T, so when you integrate those the average is proportional to rate up to the point where T is equal to the internal between sensor pulses. Still a simple circuit though.

Thread: Can this motor be reversed?
09/08/2018 16:39:59

The critical question is whether one end of both the start and run windings are commoned together inside the motor or outside. You need to swap the connections to either the start or the run winding, so you need to find the appropriate connections. If the common is inside it might still be possible to get at it; but if you can't then the motor cannot be electrically reversed.

Thread: Gear Hobber : Design ideas please ...
09/08/2018 15:52:10

Another reason to use LinuxCNC! It looks like he is using a gear as a spindle encoder with 3 sensors offset presumably each by 1/3 tooth and x-ored to get a x3 pulse rate as well - but impressive how LinuxCNC is effectively implementing a gearbox between the hob and the blank.

Thread: no recoil
09/08/2018 11:24:18

Deleted double post...

Edited By John Haine on 09/08/2018 12:07:24

09/08/2018 11:06:31

Russell is correct, but looking at the relevant Clickspring video this is essentially an anchor escapement with a small amount of recoil. Do you mean recoil in the technical sense, or impulse? Recoil is the action whereby the pendulum overswing forces the escapement wheel to turn backwards, which actually absorbs energy from the pendulum which is given back with interest slightly later.

When you apply "several turns" on the barrel, what percentage of winding is that? What if you fully wind?

One thing to try is to see if the clock will run when you apply a greater torque to the train than the spring can, either manually or by a weight.

Thread: Gear Hobber : Design ideas please ...
09/08/2018 07:25:35

You could drive the spindle with a stepper as you say, but normally the spindle is rotating rather fast for a stepper to cope with and give reasonable torque/power to drive the cutter.

You mention having an encoder on the hob spindle - that's just what a number of the schemes described above do. The problem is that you need a very fine encoder to make the numbers work, so JS for example used one with effectively 4000 lines - 4000 pulses per hob rotation. Other schemes described here try to avoid this by having for example 1 pulse per rev and electronically multiplying this up using a phase locked loop, implemented either in hardware or software, then dividing down to drive the blank.

08/08/2018 09:37:30

I can't agree that a PLL is tricky in this case. There will only be a limited range of spindle speeds - possibly only one, and a fixed division ratio between the VCO and the spindle pulse - following JS's practice perhaps 4000, or 4096 to be convenient in binary. The 4046 has an edge triggered frequency/phase detector which makes locking pretty reliable provided the VCO frequency is well centred. It may jitter rather, but there is also a pretty large division ratio between the VCO and the spindle carrying the blank so the phase errors will be reduced by this ratio. It's true that one will not be able to stop the milling spindle and restart it in sync but I'm not really sure that's a requirement - anyway it may be possible to add some such synch as a refinement. The programmable divider is simple, the MEW article had a circuit for one, or it comes from the application notes for the ICs - 4000 series CMOS has programmable dividers, in fact the 4059 chip will divide by any number between 3 and 15999 but I think has to be programmed in binary which is a bit tricky.

Yes the whole thing is possible in software if you are skilled at real-time programming and using a processor with high enough clock speed, but such skills are rarer than building fairly simple logic circuitry using 4000 series devices on strip board.

07/08/2018 16:39:31

In MEW a while back there was a design for exactly this. It needs a high count encoder on the mill spindle to generate pulses that are divided down to drive the stepper that rotates the gear blank. I seem to recall that Sir John also had some ideas on this.

This is something that I've been contemplating to use with my digital dividing head conversion. Failing a high count encoder (which is expensive and tricky to add to the spindle), a better approach IMHO would be a one pulse per rev encoder and a phase-locked loop to multiply the spindle speed up so you set the division ratios using two dividers, one in the PLL and the other dividing down the PLL's VCO to drive the stepper. I've even got as far as buying the program switches! I think it should be doable with a few CMOS dividers and a 4046 PLL chip.

 

Edited By John Haine on 07/08/2018 16:41:40

Thread: Need a Frame 56 size motor pulley
07/08/2018 09:25:37

Do you have a lathe, or is this the motor for it? It would be easy to get a pulley with a standard larger bore, say 13 or 19 mm, and make a little bush which you loctite in place.

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