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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: Emco Compact 5 Motor Problem
05/01/2016 19:44:31

I have a problem with the motor for my Emco Compact 5 CNC lathe. This machine has a 180V DC brushed motor of some 440W. The fuse on the drive board blew some months ago: replacement fuses also blew immediately power was applied. I took the motor to a repairer who said that they had fixed a small problem with it.

But it still blows fuses. I installed a new board from KB. With the motor on the bench it ran fine but, as soon as I installed it in the lathe, the fuse blew. I suspect that the problem is down to a short circuit in the motor when it is running (it measures open circuit between the wiring and casing when stationary).

What to do? I cannot find an equivalent DC motor in my web searches and Emco do not appear to support this machine any more (even if they did, I would need to mortgage the dog to be able to afford it). So, do I change to a 3-phase motor & VFD? Find a brushless DC motor of suitable power/speed/size? Convert to treadle power? What does the collective wisdom of the forum suggest?

Ta

Dave

Thread: Aircraft General Discussion
27/08/2015 12:50:18
Posted by Gordon W on 26/08/2015 16:42:08:

I remember seeing a TV program about the chap who actually tested the seats, can't remember the name. He got some pretty horrific injuries just doing the job, displaced organs etc., but reckoned to recover after a few weeks.

Many years ago I read Doddy Hay's autobiography "The Man in the Hot Seat". Hay was one of the first "test pilots" employed by Martin Baker to test the early ejector seats. An interesting read, if you can find a copy.

Thread: What did you do today (2015)
11/08/2015 22:12:22

Pistons done now for my Bobcat infernal combustion engine. Trial assembly and I am chuffed that it turns over smoothly. I had worries that it would bind and need lots of fettling to free it up.

Thread: Aircraft General Discussion
10/08/2015 21:24:54

We were having lunch today when Sally B taxied in and parked outside the canteen. Not sure why she visited Cambridge, which is just down the road from her "home" in Duxford. Must have been getting ready to buzz Andrew...

Thread: What did you do today (2015)
31/07/2015 21:03:41

I finally finished installing the DRO on my lathe tonight. Considering that I bought it at this year's Ally Pally show, that is fast work by my standards...

Thread: increasing the bending stiffness of steel pipe or tube?
08/06/2015 19:07:59
Posted by Michael Checkley on 07/06/2015 23:22:47:
This second statement is incorrect as the second moment of area of the cross (taking moments about the same plane) will change as the cross rotates about its centroid.

This is a common misconception, which is why I mentioned it. For a shape such as a cross with equal leg legs, the second moment of area is the same at any angle: do the math for a "+" and a "x" and you will see!

07/06/2015 21:56:55

I just did a quick check of a 50x5mm steel tube when filled with concrete. The maximum increase in stiffness (ignoring differences between the tension & compression sides) is only 10%. As mentioned above, the best way to significantly increase its stiffness would be to put it inside a bigger tube or get a solid bar.

Incidentally, a bar in the shape of a cross has the same stiffness in any direction. So a + and a x that would fit in the same tube would be equally stiff.

Thread: What did you do today (2015)
31/05/2015 20:38:22

Having fitted handwheel dial to the lathe, I finished screw for my machine vice. Oh what a joy to be able to turn to a shoulder at last! Why could Myford not fit something like this as standard?

Handwheel dial.jpg

The bad news is that the screw for the vice does not fit the nut. It screws in a short way and then jams. A check with a thread gauge showed that the 16 TPI die that I used cut a different pitch: peeved, to say the least! It is not easy (for me) to photograph, but you can see the problem below.

Thread.jpg

24/05/2015 22:57:04

Finally got around to using my new roughing cutter in the mill. Goodness: why did I not try one before? I have been creating mounds of swarf in record time!

11/04/2015 13:19:35

Metal storage.jpg

I have been sorting out my raw material storage. My stepdaughter acquired some plastic storage trays at some time in the past that she donated to me. They were not very useful on their own but, with a bit of 6mm MDF, they now fit neatly under my bench.

Thread: Who is going to Alexandra Palace tomorrow
19/01/2015 21:47:55

I enjoyed my day out at AP, even managed to smuggle a bag of tools into the workshop without SWMBO noticing. I thought that the flying display put on by the pigeons was impressive, too.

Waiting for the train up to London, I am always amused to see the army of "old gents" at the station: I know exactly where they are going!

Thread: Favourite Engineering quotes.
17/09/2014 21:10:46

For the Aeronautical Engineers (Quoted by AJ Coombe):

"Crinkle, crinkle, little spar,

Strained beyond the yield point far.

Up above the world so high,

Bits & pieces in the sky"

And a re-take of an old one by an F1 colleague:

"If it looks right, you are not looking hard enough"

Thread: What did you do today? (2014)
26/08/2014 21:14:53

Having pushed my luck with parting off a big lump of cast iron with my new rear tool post, I must admit that I chickened out of the power feed malarkey tonight. However, both the HSS tool & KIT-Q-CUT worked well on a 16mm steel bar. Ah, parting is no longer such sweet sorrow!

23/08/2014 22:08:19

parting 100mm cast iron.jpg

I have been playing with my new rear parting tool. First off, parting a 100mm diameter cast iron bar (adaptor plate to mount a chuck on my rotary table). Yes, the tool overhang is a bit silly, but I wanted to know whether it would do it...

Next up, do I have the nerve to part a steel bar using the power feed (and a shorter tool overhang)?

Thread: Bad Design ?
08/04/2014 22:28:51

Compressor blade. Outrunner. If that is going into a ducted fan I'm standing well back!

Thread: Engine Demonstrator Compressor Project
10/03/2014 19:40:38

Brian's mention of scuba made me think of an industrial nitrogen cylinder: large volume at some 300 bar should keep a V10 going for a few minutes. But (one of the) obvious problems would be controling the temperature if the flow was too high. And the safety of all that stored energy.

Thread: Any one know what this is and what's it used for?
03/03/2014 18:06:06

Ah! So that is what it is. I did wonder what on earth it was when it (or something similar) came up on eBay recently.

Thread: Myford Super 7 Headstock Lubrication
30/12/2013 12:15:33

Two steps forward! I have just removed the oil cup: no blockages, but very little oil in the passage. Checking the Myford manual, I should be using Esso Nuto H32. I am actually using Castrol Magne BD68 (as called up for my little Emco mill). It looks like it is far to thick to flow throught the Myford headstock. Read the blasted manual.

I will update you all when I get my hands on the right oil... Time to invest in one of those Reilang oil cans, too?

Thanks for the help. I should have asked earlier!

PS. Who thinks up these names for oil??

Dave

30/12/2013 11:17:46

Thank you for your suggestions. They confirm my fears that all is not well in the headstock. As soon as I get permission from SWMBO to go to my workshop, I will take the oil cup off & see if the oil passage is blocked. I will let you know my findings.

Dave

29/12/2013 19:57:34

I have been a "silent" member of the forum for some time, but the time has come to poke my head above the parapet. I have owned my Super 7 for about 30 years, during which time it has seen several moves and the occasional spell in storage. The lathe is now back in use BUT the lubrication of the headstock has been worying me. The Myford instruction booklet requires the headstock front bearing to be lubricated twice a day. On my lathe, the oil level in the cup does not drop and I have not topped it up for years.

This seems to be wrong: does anybody have any suggestions for the lack of oil use? The headstock does not appear to run hot or sqeal. Should I strip the headstock to investigate, or leave well alone?

Thanks, Dave

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