Member postings for Andrew Johnston

Nothing personal intended and I apologise. If I've understood Duncan's follow on post correctly there never was a signal problem, so nothing to solve.

I'm happy to hold my hand up and say it's all my fault. Some years ago, after a disagreement on this forum about the Fast Fourier Transform, I resolved to never get involved with electronics threads. Stupidly I broke that rule. I must stick to my own rules.

Andrew

Ok, so the Arduino has changed - makes sense. Simplest solution is to stick two or three more diodes in the supply line. If interference on the 5V line hasn't been a problem I wouldn't worry about trying to fix it unless it has been proved to be such.

Andrew

Edited By Andrew Johnston on 11/09/2020 14:45:55

If I've understood correctly the system has been working fine for two years, but has suddenly had a number of failures? This is put down to the applied supply voltage. Has the system been run from a different supply, or flat batteries, over the last two years? If not, then why would the same supply voltage suddenly cause failures? Has anything else changed? Sticking Zeners/capacitors in without understanding the issue is a job creation scheme for monkeys.

Andrew

For small sizes of steel, below 1-1/2" diameter, I buy standard 10ft lengths from commercial suppliers. Likewise I buy the standard 20ft lengths of hot rolled steel. For hot rolled it is cheaper to buy the full length than a shorter length. I also buy full 1m x 2m sheets of steel. After a number of years I've built up a good stock of steel, such that I don't need to buy much now. I mark the steel before storing, on rounds I stamp the EN number on the end.

I don't use aluminium on my traction engines, other than for fixtures. I have bought a lot of aluminium section and plate for work. Section is bought in standard 20ft lengths and plate cut to size from commercial suppliers.

Silver steel and gauge plate comes from Coventry Grinders, usually in 500mm lengths.

Cast iron, bronze and brass come from M-Machine (cut to the length I need) or Macc Models nearest standard size. I normally add a bit for fumbles. So if things go right I build up a small stock. Plastics come from a local supplier (EDP Plastics) in Cambridge.

I rarely buy material from Ebay. Usually only when it's mega expensive elsewhere, such as tungsten alloy, or I just need something for making a fixture and don't care about the machinability or finish, Such as this lump to make a former for the engine chimneys:

Andrew

Consider what happens to still water; it goes stagnant and everything in it dies.

Andrew

Despite calling it strength I think SoD means stiffness. If all beams are the same length and weigh the same then they must have the same cross sectional area. The deflection of the beam shown by SoD is inversely proportional to the moment of inertia. So it's simply a case of comparing moments of inertia for constant area to find the stiffest shape. All the information needed is in Machinery's Handbook.

Andrew

The RH & LH gauges are marked for 20mm, 3/4", 1", 2-1/2" FT and 3-1/2" FT dies. The numbers run from 50 to 145 on both gauges. I also have a RH gauge for 1-1/4" dies where the numbers run from 70 to 145. A die marked 77 is pretty close (±1) on both RH gauges. So I surmise that the numbers are linear across the complete range of dies, at least in the sizes we are likely to use. The height at 120, measured with gauge blocks, is 0.359".

I measured the angle on two gauges with a clinometer. I got 2°55" and 2°52". I'd agree that the markings appear to be 1/16" apart, as measured with a rule.

Andrew

Oh dear, that's a shame and a loss of valued insight. Sorry to see you wind down, although I understand the reasons. Good luck with the other ventures.

Andrew

As far as I'm aware the angle stays the same, as it controls the transition from cutting to guiding. I don't know the value of the angle.

I have LH and RH height gauges for 3/4" and 1" dies. Height gauges vary; I've got one for 1/4" and one for 1/2" but the values overlap slightly. So presumably one or the other would also do for 5/16" and 3/8" dieheads. In theory it should be fairly easy to make a height gauge. One just needs the angle, the spacing of the ticks and one reference point from a known good die.

I don't know when the new grinding fixtures came in; I'd hazard a guess in the 1960s. They're not in my Ed 22 version of the handbook.

Andrew

On my M300 the rear pads hold a beveled pattern bar for a hydraulic copying unit:

The front pads carry a trip bar for an Ainjest high speed threading unit:

The Ainjest unit is bolted on the right hand side of the saddle and the rectangular trip bar runs the full length of the bed below the electrical actuator rod.

Andrew

So that's where I've been going wrong.

I take the time to read what I've written before posting and try and correct spelling errors and grammar. So I must be a lousy engineer. Of course Chris is confused; engineering and model making are not the same thing at all. A good engineer might be good model maker and vice versa, but one doesn't automatically infer the other.

Andrew

My Harrison M300 (1500lbs) is bolted to the manufacturers sheet metal stand. I understand that the lathes were shimmed to the stand during assembly. So it is an all round bad idea to separate the lathe and stand. The manual recommends slinging using either an eyebolt in the M16 thread in the bed cross member or with a sling around each end of the drip tray, so lifting on the stand rather than lathe itself.

Andrew

Using an engine crane is a right royal PITA. It doesn't generally have enough reach to place the machine where you want it on the trailer and the legs and trailer wheels or rear stands always seem to clash. If at all possible roll the machine on and off the trailer. I use lengths of 2" steel bar as rollers.

Andrew

If by a car trailer you mean one designed for moving a car forget it. You need a two, or ideally four, wheel trailer with a solid floor and ideally a rear ramp. Once the machine is loaded and the balance is right, ~50lbs downforce on the hitch, then block the base of the machine in all directions. And I mean blocks, don't rely on straps. Perfection would be to mount the machine on large cross baulks of timber before loading as that will also help to stop it tipping during loading anf unloading. Once on the trailer and blocked then add straps at angles to prevent any fore and aft or side to side movement. While you may not expect to do an emergency stop, you don't want the machine sitting alongside you in the car if you have to.

This is how I moved a cylindrical grinder over 100 miles. I was cautious and limited myself to around 50mph on the M25:

The straps have been removed along with the tie for the counter-balance weight. A better trailer was this one, moving a repetition lathe, only 15 miles but it's still securely fixed. For ease of loading the lathe is actually sitting on a pallet truck, but everything is still blocked and tied:

Note the stands at the rear of the trailer, very useful when loading/unloading. Make sure you tow with a sensible car, ideally at least 1.5 tonnes kerb weight. It's no fun when the trailer takes charge of the car.

Andrew

We're talking two completely different cases. When driving the M300 we're comparing driving a motor in star at 415V with driving the motor in delta at 240V. In this case the power output, and torque, remains constant.

In a star-delta starter the applied voltage does not change. The motor is designed to run in delta. Direct off line startup currents would be very large. So the motor is started in star (with the fixed applied voltage) so phase currents and start up currents will be lower. The currents, and hence torque, in star are about a third of the values when the motor is running in delta. So when the applied voltage doesn't change the power output, and torque, are different in star and delta. They're both higher in delta.

Andrew

LH boring bar works fine and has the appropriate reach:

Andrew

I don't understand why they would say that? The frequency doesn't change, so neither does the speed. Given that the plate I showed indicates that the output power stays the same then the torque must also stay constant.

Remember that the phase currents in delta are higher than in star. So if the current limit in the VFD wasn't increased that may explain why the motor didn't start properly in delta. The start currents will also be proportionally higher so may be the VFD was going into current limit? A longer ramp time may ameliorate that.

Andrew

Although the motor on the M300 is reasonably accessible my lathe is up against a wall. I've had a quick look but can't immediately see a ratings plate anywhere on my motor. Going on the experience of Alistair who has recently installed one the terminal block has six contacts which means it is dual voltage. Being a cynical old git I wouldn't put it past the manufacturer to buy dual voltage motors but mark them as 415V only in order to charge more for a dual voltage motor option.

A motor designed to run at 415V in star will expect 240V in delta, ie, divide the voltage by the square root of three.

Andrew

Sigh, that is incorrect. Here's the plate from the 3-phase motor I bought to drive my Pultra lathe:

The two lines for 230V delta and 400V star have identical powers.

Andrew

Do you know that, or did someone tell you? In my manual the spindle motor part number is the same on both 415V (UK) and 220V/380V (European) schematics.

I run my M300 on 3-phase so I'll avoid the debate about VFD plus 3-phase motor versus single phase motor. Although in either case the switch gear may well not work, nor may the coolant pump.

Andrew