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Member postings for DrDave

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

Thread: Centroid Acorn
19/09/2018 13:33:21

Hi Alistair,

I treated my Emco F1 mill to an Acorn controller earlier this year: have a furckle around in the forums for my words & pictures. I found that the board was easy to use and wire into the machine. I would say that the main pros are that the board works via ethernet (not an obsolete parallel port) and that Centroid's videos and wiring diagrams take the pain out of installing and setting it up. The con is the price!

I was sufficiently impressed that, when I had a bit more cash, I bought a second Acorn for my C5 lathe. Update of this will be finished shortly, just as soon as I modify the auto tool changer to take a stepper motor.

Dave

Thread: What did you do Today 2018
21/08/2018 12:47:18

I am tarting up the control box for my lathe. Instead of bodging something from a bit of of-the-shelf steel from Wickes, I ordered some bespoke sheets to be cut to size for me. They have just arrived so I am feeling smug.

Or I was until I realised that I have no excuse not to finish the job now. Hump!

Thread: Aircraft General Discussion
19/08/2018 11:39:37
Posted by J Hancock on 19/08/2018 08:15:42:

For those who don't know of, or have never been to, the AVRO museum in Woodford, I can only suggest

a visit. The enthusiasm of the volunteers running the museum is priceless.

Do the research for the best time to visit, allow at least five hours to do it all.

I mentioned this to Mrs Dave this morning, with a view to visiting. Her reply was “Woodford? Is that the one near Chingford?” Sigh.

Thread: Aluminium thread strength
16/08/2018 20:57:28
Posted by mark costello 1 on 16/08/2018 20:41:52:

Why would 5 ° make a difference in Aluminum threads?

The (nominal) tapping drill sizes are 6.6mm for the 5/16 BSW and 6.8mm for M8. This gives a smiggion more area in the aluminium & thus a greater strength. The smaller tapping drill is partly due to the 5 deg difference and partly due to the Whitworth thread being coarser (1.41mm vs. 1.25mm).

15/08/2018 20:45:48

I am enjoying this topic; lots of good info. But they say that if you ask two Stress Engineers the same question, you will get three different answers! I was somewhat more conservative than Richard when I was a Stress Engineer. I had two rules of thumb that I used for stressing threaded holes:

1) At ultimate load (the load at which the structure can deform but shall not break), the effective thread length is 1D, and

2) If you want to be able to get the bolt out again after it has been in service, then assume that the first thread takes half limit load (at limit load, the structure shall not deform)

I developed these rules over the decades that I did stress analysis of aerospace structures. This does not mean that I am right & Richard is wrong, just how different people approach this complex subject.

Thread: 3-Phase Motor Conversions: Are They All Hype?
31/07/2018 17:04:32

What a difference a day makes. I have been using my lathe much of today and it is a machine transformed. No more worrying about stalling the motor whilst turning.

Thanks again everyone.

Oh, I have left the maximum frequency at 50 Hz. I might consider 60 Hz later; the headstock gives speeds for both frequencies, so I should not be overspeeding anything. Still need to check the chucks, first, though.

30/07/2018 19:41:01

As an aside (and not wanting to hijack the “blue chips” thread); one of the test pieces that I used was, I think, an old car king pin. Anyhow, it is rusty, so I think that it is steel. It has a hard band where it used to sit inside a bearing. Hard to turn with the swarf comming off like wire wool. Mostly blue, with an occasional flash of orange. When one bit caught fire, I though it was time to change to a rather more mild bit of steel...

30/07/2018 19:37:00

Rewired to delta and, pause for dramatic effect, what a difference! On 50% setting, double the DoC used before & it does not bat an eyelid. Bootiful. No speed drop that I can hear.

That you all for your help & comments.

However.

I am a bit miffed that the reseller charges a premium price for the S7 upgrade, but appears not to set anything up. Quite what their added value is to justify the higher price than buying the same bits from, say, eBay is not clear. I will avoid them in future.

30/07/2018 17:15:40

John, thanks for confirming that the connections are wrong. I’ll rewire & try again after dinner.

30/07/2018 16:38:07

The cover plate is not very useful, but reference to t’internet suggests that the motor is wired as star.

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30/07/2018 16:09:35

I have revised the controller parameters (they were slightly low, but not greatly so). Slightly improved performance, but still gutless at 50%. I fear that the motor is wired as star, not delta. Unfortunately the S7 installation results in it being almost impossible to access the connector on the motor. Checking/changing this will be a PITA!

I’ll post the results when I have dug managed to get access to the motor: this might take a while...

30/07/2018 15:12:13

Thanks for the prompt replies. It appears that I erred in assuming that the supplier would set up the VFD, as this is sold as suitable for the S7. I will have a dig around in the bowels of the controller & see if I can get it to work. Somewhat annoying because it is attached to the back of the lathe stand...

30/07/2018 14:27:13

Having read many descriptions of how good the VFD/3-phase motor drives are for upgrading your lathe, I took the plunge & bought a set for my Super 7 from one of our reputable suppliers. Whilst it runs well, it always sounded under-powered, even though the motor is rated at 550 W (¾ hp). Even “light” cuts make the lathe audibly slow down. The other night, I even stalled the motor. With the lathe on its second highest speed, potentiometer set to “5”, and drilling out a 6 mm hole to 10 mm (in steel), I was a little surprised at this. I would not expect any problem doing this with the original, single phase motor.

So, is the VFD set up incorrectly (I left the settings as supplied), am I doing something wrong, or are the virtues of the VFD overstated? Is this behaviour to be expected at 50% speed and are my expectations too high? What are other people’s experiences?

Thread: Tangential Tool holder
29/07/2018 22:03:14

I thought that putting a radius on the corner of the tool was done to avoid having a sharp corner when turning a shoulder.

Thread: What did you do Today 2018
24/07/2018 12:01:45

I must have lived a charmed life; I never understood how people managed to break taps. I broke an 8BA tap this morning, my first one. No warning. At least there was enough poking out the other side of the hole to get a pair of pliers on and, with some difficulty, get the mortal remains out. “Pride cometh before...” and all that!

Thread: Aircraft General Discussion
03/07/2018 09:35:43
Posted by Andrew Johnston on 03/07/2018 09:17:06:

The B17 Flying Fortress flew over the office twice yesterday afternoon at around 1000ft. Not sure what the accompanying aircraft was. It had a twin tail but didn't look right for a Mitchell, so probably modern. They were quite close, less than the B17 wingspan; presumably filming?

Andrew

OV-10 Bronco? It is a twin-boom aeroplane that is commonly used for air-to-air photography.

23/06/2018 19:43:23

Strange how these things happen. We went from Bedford to Chichester to have dinner last night with an elite group of former aerospace colleagues. One of them, who lives in Bognor, left this moring to drive up to Old Warden for the weekend to visit the Moth “do”. So we will probably see him there tomorrow!

Thread: Lost and Found
20/06/2018 11:28:11

A different take on the “wrong car” tale. One day, my mum drove up to the Post Office to collect the mail from her Post Box. Before she could get out of the car, a man (distracted by the mail that he had just collected from his Box) walked up, opened the driver’s door and nearly sat on her knee! He was somewhat embarrassed, apparently.

Thread: Emco F1 Mill Upgrade
19/06/2018 22:44:50

Thanks, Nige. I was a bit worried when I started the mod. There is no way back and, if something didn’t work, it could have ended up as an expensive boat anchor...

Dave

Thread: Lost and Found
19/06/2018 21:23:24
Posted by Jon Lawes on 19/06/2018 21:16:41:

A guy I work with spent ages waiting for his wife to pick him up from work. He didn't have a mobile back then so he took the bus home, smashed open the front door and gave his missus a mouthful of foul mouthed abuse for not coming to get him as usual.

"But you drove this morning?"

I bet none of you lot have misplaced a car... laugh

That certainly trumps my “spare” bag of cable tie bases!

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