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Member postings for 9fingers

Here is a list of all the postings 9fingers has made in our forums. Click on a thread name to jump to the thread.

Thread: Home Workshop Site
10/09/2019 08:40:06

+1 on that Jason.

I noticed some dodgy typing in his post too indicating that he might still have a way to go before firing on all cylinders.

Wishing Adam all the best for his recovery.

Bob

28/08/2019 21:50:54

Ketan, Please include me on the lengthening list of good wishes to Adam. We have never met but I visited John several times and benefitted from his generosity.

Bob

Thread: Myford Super 7 screw cutting gears (metric)
25/04/2019 09:00:02

Just a public THANK YOU to simon for sending me an extremely professional 34 tooth changewheel.

What a Gent!

Thanks

Bob

18/04/2019 21:19:01

Does anyone know of a source of either a set 21, 33 and 34 tooth gears or just a 34 that will get me out of a current problem please.

TIA

Bob

Thread: CovMac Lathes
14/08/2016 13:07:20

Hi Phil, yes I noticed that when I looked at your photos last night. Bit of a mystery. I wonder if your starter is subtle different from the one I looked at for Chris?

There is not really any such thing as two phase as it it just double the voltage. I did read about a system that was used somewhere for a while which was two phases at 120 degrees explicitly for running motors without the need for a starting capacitor but of course the phase to phase voltage would not be doubled in that case.

Chris's stayrite starter had a circuit diagram pasted inside, a bit tatty but that is what I based my write up on. Maybe yours has too and you can see if it is essentially the same or different. Chris's motor was not labelled as Stayrite so I think it might not have been paired with the Stayrite starter originally. The wiring was bodged with six red wires threaded up some garden hosepipe (Not by Chris I hasten to add!) but (bless him!) had just cut through the lot so it was a detective job to work out what was what in the first place. Hence connecting lightbulbs to the starter first to watch what happened.

Apologies if I have introduced noise into the discussion....... It was not intentional

Bob

13/08/2016 23:18:10

You need the higher current to get the motor moving.

I think it harks back to days when capacitors were expensive and short lived and copper was relatively cheap. It predates the reversible electrolytic capacitors that were then used as start capacitors of relatively high value but limited to a few starts per hour.

Bob

13/08/2016 17:54:37

Not quite right Phil I'm afraid.

The motor/starter combination is single voltage. The windings are paralleled up by the control box during starting only and when you release the start button, they are connected in series for the run mode and the start winding is switched out.

Please see my write up for the detailed operation.

Bob

13/08/2016 09:39:22

I did the work on this stayrite starter for Chris Mills and it is written up in annex G to my motor paper.

Thanks to NTLworld withdrawing my free webspace, the new link to the paper is here

https://drive.google.com/open?id=0B_GZrXNsNxTlQzd6aldlQjJtUDQ

Identifying the winding should be easy. look for three isolated winding, two similar which will be the two run windings and one different which will be the starter.

Under the grey cover in the starter will be the capacitor(s). check that these and not leaking either chemically or electrically and if so replace with similar rated new ones.

hth

Bob

Thread: Bending Brass - Advice sought
18/01/2015 12:09:15

Possibly a good idea. I've just ordered a sample from fleabay.

Cheers

Bob

18/01/2015 10:59:07

Hi Julian,

Thanks for your reply.

Are you suggesting the heat to anneal the brass followed by cold(cooler!) forming or forming whilst at dull red temperature?

The latter will mean my jig will need to be quicker fitting than the current back of envelope design supports with several screws to be tightened before bending.

TIA

Bob

Edited By 9fingers on 18/01/2015 10:59:32

Edited By 9fingers on 18/01/2015 11:00:04

18/01/2015 10:45:08

Thanks Michael, I did not know that but I'm getting the picture.

Looking at your link, CZ121 seems to be workable hot which could be an option - anyone got experience?

I presume the angle must be hot drawn in the first place?

Alternatively Is angle available in consumer quantities in cold forming alloys? Bearing in mind that I also have to do some limited machining on the parts to a visible standard eg clean csk holes.

Bob

18/01/2015 10:31:15

Hi Jason,

Thanks for the rapid response.

No sadly the length is not to scale - overall about 300mm and I'll need to make about 20 off.

They are part of a guide system for barrister bookcases that I'm making to a custom design.

Bob

18/01/2015 10:19:19

I want to make a quantity of the part shown in the drawing from stock brass angle 10 x10 x1.5 or imperial equivalent.

bookcase end stop.jpg

Where suppliers state the type of brass angle they tend to quote CZ121 which looks to be formulated for best machining quality rather than bending.

I need to start from stock material as I don't have the equipment needed to form the angle from sheet stock which has optimum bending qualities.

My question is how readily can 1.5mm thick CZ121 be formed to a 5mm radius on a scale from "piece of cake why even ask" to " you have got to be joking mate"

Also will heat be needed - desirable - helpful - essential etc

This will affect how I design and build the bending tool.

n.b. The overall length will be about 300mm. The drawing just shows this particular formed feature.

 

TIA

Bob

Edited By 9fingers on 18/01/2015 10:32:50

Thread: CovMac Lathes
01/01/2015 21:35:30

Thanks for your kind comments Brian.

I enjoy solving puzzles and jobs like this motor help keep the little grey cells working.

Bob

30/12/2014 15:49:42

I've now completed my investigation and documentation of Chris's COVMAC motor and associated AEI Stayrite series parallel starter.

The details have been incorporated into the latest version of my motor paper at Annex G

The current version can be downloaded from here:

http://homepage.ntlworld.com/bob.minchin/Induction_motors_Issue3.pdf

I hope that it will be of interest.

Cheers

Bob

28/12/2014 12:17:46

I have to agree with Roger, that a VFD and three phase motor is by far the best solution for a working lathe. I can't imagine anyone wanting to revert to fixed speed powered lathe (or mill) having used infinitely variable speed drives.

However i can see Chris's point regarding historical accuracy. If the AEI Stayrite is not original then the EE motor would have needed something similar although I'm not totally convinced that a single phase motor would have been fitted to such an industrial lathe originally.

My hunch is that it could have been converted to single phase operation when it was refurbished in 1955 and the AEI Stayrite fitted then. I've not found anything internally to date the box. Usually capacitors are dated if nothing else but curiously not in this instance. They are made by DALY - a name from the right era - and don't look like they have been changed from original manufacture of the control box.

Chris's point about hiding the control box away is viable as provision is made in its construction to have remote start and stop buttons wired in. A DOL starter of "correct age" could be re connected internally to provide this function and look the part.

Bob

27/12/2014 21:03:27
Posted by CHRISTOPHER MILLS 1 on 27/12/2014 20:50:22:

Hi Bob,

I think this website will only accept Jpegs as visual inputs.

Best.

Chris.

OK when I have the write up complete, I'll add it as a new appendix to my motor paper and link it here.

I'll also send you you own copies of the individual documents. I now have all the instructions in word format after doing OCR on photos of the insides of the controller.

Bob

27/12/2014 20:53:12
Posted by Phil Whitley on 27/12/2014 20:29:56:

Hi Chris, when you say it blew a fuse, do you mean a fuse in the 13A plug?, not surprising really, you will need a seperate circuit wired back to your consumer unit and rated at 35 or 40 amps. Not a problem, as some modern electric showers draw this region of current and because of the clutch on the input shaft of the covmac, you will be starting the motor off load. There is a long way to go before you need to press the start button!

I am having a day off eating tomorrow!!

Happy Christmas!

Phil.

I've only been starting off load - not even a belt so a 13amp fuse will supply the 34 amps for a short while.

Ultimately I will recommend a 32amp commando plug with a type c 20 or c 32 amp MCB for the installation.

Bob

27/12/2014 20:47:48
Posted by Phil Whitley on 27/12/2014 20:05:39:

Hi 9fingers, I would be interested to see the motor/ starter sort out! This is why I emphasised to Chris how important it was to get the original starter with the motor. It is an AEI Stayrite, and looks like it is the right one for the series parralell capacitor start. I have been in electrical engineering since 1967, and although these were not common, we did used to meet them on things like original Heidelberg printing presses which had been fitted where 3 phase was not available. There is nothing similar in my "Brooks" motor book, but I gather Chris marked the terminals when he disconnected the motor from the starter, so it should be a matter of servicing the starter and reconnecting as was. Capacitors in these installations are sometimes fitted in the starter itself, and switched in when needed. In the meantime I will have a rkae around my old paperwork and see if I can come up with any diagrams.

Phil

I've all the diagrams in visio and instruction .doc files - all I need is a way to upload the files to this forum. Any ideas?

I'll possibly use .pdf for maximum readability for here though.

Eventually I'll write a new section to this as my collected work on induction motors

http://homepage.ntlworld.com/bob.minchin/Induction%20motors%20-%20Issue2.pdf

Bob

27/12/2014 16:59:16

I've not posted in this thread to date but have been involved with Chris's COVMAC lathe assessment and move since being introduced via a mutual friend.

I've been working with single and three phase induction motors for very many years but finding this one with 5 power connections and a separate controller was a new one on me and also a couple of friends older than I.

I now have the motor and controller on the bench and had some time to investigate it thoroughly.

There are a total of 6 terminals each going to the ends of 3 three separate windings. One of these is the Start winding marked Z1 and Z2 and the other two winding are both used for Run A1-A2 and A3-A4. It has no internal capacitor or centrifugal switch.

If you come across one of these motors then it is vital that a standard direct on line (DOL) starter is NOT used.

The regime for starting these motors is to connect the run windings in series and momentarily connect the start winding with a series capacitor in parallel with the run windings. Once the motor is up to speed, the controller disconnects the start winding AND switches the run windings from series to parallel.

As far as I can tell, this series parallel switching is there to keep the starting current reasonable. Even so the peak start current on this motor (3HP) is 34 amps before settling down to just over 10 amps once running.

Full load current is specified as just over 13 amps.

img_0925.jpg

 

img_0926.jpg

I will be supplying Chris with full documentation of the motor and controller. If there is interest here, I can publish it here too if I can workout how to insert files.

Cheers

Bob

 

Edited By 9fingers on 27/12/2014 17:06:39

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