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Member postings for Toby

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

Thread: Replacing Flourescent Tubes with LED tubes
22/02/2017 08:49:03

I have to admit I thought the only way of getting decent LED light was to replace the whole fitting rather than just using a retrofit LED tube. From the comments above though it sounds like they have improved a lot and I am behind the times!

Having said that, the specs don't back up the views above.

eg a Ledkia 5ft tube here**LINK**

is 2200 lumen.

A standard flozzy tube is about 5500 lumen.

Which is about what I would expect as the LED is only 22W vs the flozzy at 58W and the efficiency of LED is not that different to fluorescent. (certainly not twice as good)

EDIT: according to wikipedia a T8 fluorescent tube is about 80lm/W efficiency, leds are up to about 100 to 130lm/W now so, while LEDs are noticeably more efficient you would still need around the same power input to give a significant light output. And that is the trouble with LEDs they don't like power as they get hot and fail, hence there fact that overall the struggle to match fuorescent.

The story is slightly difference with CFL incandescent replacements, theses small, coiled, tubes are not very efficient so it is possible to get like for like LEDs that are as good if not better.

In my house all bayonet and edison screw bulbs (and GU10 spots) are now LED but any tubes are still fluorescent. If I was to replace the fitting though I would go with LED as long as cost and style were not issues. 

Edited By Toby on 22/02/2017 09:11:09

Thread: Single phase reverse electrical genious required
21/02/2017 22:16:03
Posted by Martin Newbold on 21/02/2017 20:58:09:

I have read in regard the letters W V U the following however its seems a bit greek

 

normative DIN (GERMAN ) use the first letter U mean (oder)V, W (ELCTRICAL MACHINERY) AND (R) (S) (T) FOR electrical terminals phases 120° degree R is not Run , S is not Start , T is not Time

<p style="margin: 0px 0px 1em; padding: 0px; border: 0px; font-size: 15px; clear: both; color: rgb(36, 39, 41); font-family: Verdana, " bitstream="" vera="" sans",="" "dejavu="" tahoma,="" geneva,="" arial,="" sans-serif;="" background-color:="" rgb(255,="" 255,="" 255);"="">I presume this is for Three phase so not applicable

Correct, this is for 3 phase and nothing to do with reversing them.

If you are after reversing a single phase induction motor this link might help you.......

**LINK**

 

EDIT: Somehow I missed the fact this was the end of a long thread on the subject so apologies if what I have said is not relevant.......

Edited By Toby on 21/02/2017 22:18:02

Edited By Toby on 21/02/2017 22:18:20

Thread: Replacing Flourescent Tubes with LED tubes
21/02/2017 22:03:17
Posted by petro1head on 21/02/2017 21:23:45:

Edit: been having read and from what I can see LED will not be as bright

Edited By petro1head on 21/02/2017 21:46:11

Correct, generally the fluorescent are brighter for the same size tube although LED is getting better all the time.. Are your walls and ceiling painted white? If not, doing that will double how bright it looks.

Depending on how old they are just replacing the tubes might also improve things, apart from that changing them for doubles or fitting more would be the way to go.

Thread: A milling machine problem
17/02/2017 19:29:10
Posted by Ian Parkin on 17/02/2017 19:00:06:

Given that Paul is in Canada the motor is probably star wired for 220v....here it would be 415v for star 240 for delta/mesh

Could it be that the motor has been wired delta rather than star..that would cause it to draw too much current and get hot if Paul is feeding in 220v into his VFD

a good point!

17/02/2017 18:52:31

What Paul has said is that the motor is drawing 8 to 9 amps on the mill (without any cutting load?) against a plate rating (FLA?) of 7 Amps. So it is no surprise it trips. I think the question is, why such a high current.

I think Paul really does need to go back to basics but he needs to do what John Rudd suggested. i.e test the motor disconnected from the mill (but with his inverter) so he knows if the excessive current is due to load from the mill or a problem with the motor and/or inverter.

We know the motor has been bench tested by a motor guy so it should be easy enough to compare the non-load current on the bench test with the non-load test with Paul's inverter. One assumes that, if the motor specialist says the motor is fine then the non-load bench test current is much less than the plate current. But it would be good to confirm that.

I also have another question, what voltage was used for the bench test and is that the same voltage Paul's inverter is giving? (ie 220V 3 phase) And is the motor definitely wired delta and this hasn't been messed with since the bench testing? (ok, that is two questions...)

 

Edited By Toby on 17/02/2017 18:53:21

17/02/2017 11:45:24
Posted by John Rudd on 17/02/2017 11:02:50:

Paul,

If you remove the belt from the motor/gearbox and run the motor, this will tell you if the gearbox is loading up the motor.....

When you run without the belt on, what is the motor current then?

If nothing changes or there is little change, then I'd agree with Muzzer's thoughts on a wiring issue...

Edited By John Rudd on 17/02/2017 11:05:15

that is definitely where I would start..........

Thread: Quality digital vernier calipers
12/02/2017 22:22:36
Posted by Nick_G on 12/02/2017 21:38:58:
Posted by Neil Wyatt on 12/02/2017 21:26:21:

OK, it's clear that not enough people who are contributing to this thread read MEW (shame on you!)

To show you what you are missing and shed some light on different calipers, please see this article I have uploaded:

www.model-engineer.co.uk/article/digital-caliper-comparative-review/

Neil

.

Thanks for the link Neil,

But what IMHO would really be of value in a review is one written by someone who has used a product frequently for 12 months or so then drawn conclusions.

I however could not have done that for the budget M&W because it did not last anywhere near that long. wink

Nick

It still depends on the particular unit used in the review though. If you had done a year later review it would be doom and gloom. If I had done one based on my two it would be all good

what we really need is a 1 year on review on 30 plus units. But I doubt Neil has the budget for that

12/02/2017 21:51:46
Posted by Nick_G on 12/02/2017 21:25:16:

.

Hi Toby,

Would frequently find themselves a new zero point combined with wild readings. These readings were usually so far off the mark that an error was obvious. But did little for me to have any confidence in them. They also felt cheap and of no better quality than some £7 Aldi ones I once bought.

Taking them to bits and cleaning helped sometimes but an expensive or frustrating mistake was only a matter of time.

Nick

that is a shame, obviously their quality control isn't perfect.....

12/02/2017 21:13:48
Posted by Nick_G on 12/02/2017 19:28:52:
Posted by Neil Wyatt on 12/02/2017 19:02:53:
Posted by petro1head on 12/02/2017 18:29:35:

What would you say is a mid price point

How about £23.70 on special offer?

www.machine-dro.co.uk/150mm-6-digitronic-digital-caliper-moore-wright-basic-line-110-dbl-series.html

Neil

.

Those are the M&W ones I mentioned previously that ended up in my junk bin. sad

Nick

can I ask why?

like I said earlier, I have two of these and cannot fault them for the price......

12/02/2017 19:17:21

Keep an eye on MSC, they occasionally have mytutoyo verniers on sale.

eg this one: **LINK**

was selling for £59.99 (plus vat) a couple of weeks ago.

Personally I have a couple of cheap Moore and Wright 6" from machine DRO, these ones:

**LINK**

I was testing one of them today against some slip gauges and they were no more than 1/2 a thou out (which is their resolution) from 1/4" to 3". Given the slip gauges are probably well over 50 years old and more than a bit rusty in places I didn't think that was too bad

More importantly they are consistent, even with a significant variation in pressure, something I have found a problem with the cheap no-name verniers I have.

Thread: Tuning
08/02/2017 12:04:31

I think we have some rubbish management and some rubbish workforce. Governments and electorates are (nearly) always rubbish

Thread: Meddings MF4 drill electrics
05/02/2017 17:17:23

I realised I had not updated this with the latest progress - the inverter is temporarily on a bit of ply so I test everything out but wired into the original start/stop switches.

Yes, I know the wiring is not exactly to the regs but it will get done properly when I put it all in a box, honest!

After a bit of playing with the inverter settings I was ready for some drilling. First a 10mm drill through 10mm of steel, then follow that up with a very cheap 20mm blacksmith drill. The drill was visibly blunt but it didn't even break a sweat, even when leaning on the star handle I could only get the current indication on the inverter up to 1.85A (no load is 1.7A). IIRC this was on 300rpm.

I do think I need a bigger drill vice though....

drilling20mmlr.jpg

Thread: Lathe motor replacement
03/02/2017 12:45:14
Posted by Hywel Evans on 03/02/2017 12:12:42:
Posted by Toby on 03/02/2017 12:06:43:
Posted by Hywel Evans on 03/02/2017 11:43:21:

Hi Toby

Thanks for the info. I can't do the test at the moment because I only have one pulley wheel on the new motor and the old 4-wheel pulley is seized on the old motor shaft. I am going to do some more tests this weekend on a warmed up lathe.

I have done some internet research but it can all be very contradictory depending on whether there is a load or not and so forth. Given that the voltage is constant above 50 Hz the V/f ratio will decrease and so I understand the torque must also decrease. If that is the case then the current should also decrease, in a no load situation, which it does from 1.9 to 0.6 A on going from 50 to 100 Hz. However, when hooked to the lathe it increases, regardless of whether the chuck is on or not, so the gear train is obviously having an effect but doesn't seem to have anything amiss with it. Interestingly, when the backgear is engaged the current only increases from 2.1 to 2.8 A which seems OK to me.

Hywel

 

That certainly makes sense. The implication of the backgear results is that the main resistance in the gear train is after the backgear, ie spindle?

And the implication of that is that the bearings are shot, however, there don't seem to be any obvious signs of that in the performance of the lathe, though I am not admittedly doing any precise work. I did notice that when I topped up the grease in the bearings there was a period when the last motor struggled to get up to speed - too much grease perhaps?

Edited By Hywel Evans on 03/02/2017 12:12:56

maybe, but maybe not? I *think* (it has been a long time...) that my boxford spindle bearings are set with a pre-load that is measure by the resistance to turning using a spring balance. So there is supposed to be some resistance in the spindle. Whether yours is correct or not or whether the grease is causing a problem I don't know.

edit: mind you, you did say the previous motor went up in smoke. Any other reason for that other than something overloaded it?

Edited By Toby on 03/02/2017 12:50:06

03/02/2017 12:06:43
Posted by Hywel Evans on 03/02/2017 11:43:21:

Hi Toby

Thanks for the info. I can't do the test at the moment because I only have one pulley wheel on the new motor and the old 4-wheel pulley is seized on the old motor shaft. I am going to do some more tests this weekend on a warmed up lathe.

I have done some internet research but it can all be very contradictory depending on whether there is a load or not and so forth. Given that the voltage is constant above 50 Hz the V/f ratio will decrease and so I understand the torque must also decrease. If that is the case then the current should also decrease, in a no load situation, which it does from 1.9 to 0.6 A on going from 50 to 100 Hz. However, when hooked to the lathe it increases, regardless of whether the chuck is on or not, so the gear train is obviously having an effect but doesn't seem to have anything amiss with it. Interestingly, when the backgear is engaged the current only increases from 2.1 to 2.8 A which seems OK to me.

Hywel

That certainly makes sense. The implication of the backgear results is that the main resistance in the gear train is after the backgear, ie spindle?

03/02/2017 10:46:38

I was curious about this so I checked my lathe (boxford VSL, 1.5hp motor, running from cold) to see what current it takes at various speeds.

First I should point out that I appear to have it set to allow speeds between 0 and 50Hz. This also means the V/f curve is probably different to yours. So not quite the same but anyway I used speeds of 25Hz and 50Hz as a comparison.

This inverter doesn't give a current reading, rather a percentage of max rated load of the inverter. Unfortunately I cannot remember what that is and I am not removing it from its housing to check the rating plate. Anyway.......

No load (but driving the spindle/chuck) I get 28% at 25Hz and 40% at 50Hz. So that is a 43% increase in current for a doubling of input frequency. You are getting a 66% increase (taking the warmed up 100Hz figure).

Not sure if that helps, I would still suggest doing the test mentioned in my last post if you can, just to see if it is the motor causing the problems or just load from the lathe.

Thread: Tuning
02/02/2017 19:52:39
Posted by Neil Wyatt on 02/02/2017 13:33:52:

The difference with Myford is that almost everything is adjustable, and therefore to get it spot on great deal of skill goes in at the factory.

A typical far-eastern lathe will be mass produced using jigs and generally designed so that little skill is required for actual assembly whilst still giving in-spec results.

One example is the Myford headstock which requires careful adjustment using jacking screws in order to turn parallel. This requires a degree of skill and a significant amount of time and testing.

Most far-Eastern lathes are bored on a jig that matches the inverted-v form of the lathe bed; place the headstock in position, fit screws to the required torque, and you have headstock alignment.

The need for careful assembly has been superseded by a design that requires more advanced machinery and initial setting up to produce (an inverted V bed instead of a flat bed). This latter approach is better suited to mass production. In the end it's like sliced bread, mass produced loaves from value white to multi-seeded batches at prices fit for every pocket, with the option of artisan loaves for those who can afford them.

I'd also venture to point out that 'upgrading and tweking' is not unique to imported lathes. Before the days of inexpensive far-Eastern machines, there were an awful lot of articles in Model Engineer on how to improve and fine-tune a Myford. We even ran three such articles in MEW recently.

Neil

I am with Neil on this. Not wanting to offend anyone but it does make my cry when people hold up the likes of myford as "good engineering". Nicely made perhaps, and well engineered for their time but nowadays good engineering means design for manufacture which means not needed experience and costly trades just to bolt a lathe together.......

The difference between tweeking a chinese lathe and a myford (when new) was the myford probably needed to be tweeked in the factory to be useable, the chinese lathe comes out running pretty ok as it is (but can be tweeked to be even better). Which is really the better engineering?

ps. of course I am only picking on Myford because Neil mentioned it, the fact I own a boxford is irrelevent

Thread: Lathe motor replacement
02/02/2017 19:22:32

that is quite a drop off in current from 50Hz to 100Hz at no load, I am starting to guess here but I suspect that is because the inverter stops increasing the voltage at 50Hz (ie V/f becomes flat). I think this leads to flux weakening and the consequence will be a drop in torque as the speed increases. (hopefully I am not mixing my induction and syncronous motors up....)

Anyway, that doesn't explain the large current when connected to the lathe.

I'd do another test. If you can, change the belts/pulleys to get the same spindle speed as you currently get at 100Hz but now running the motor at 50Hz. So the load will be the same but motor speed will be the motor design speed for the 230V input.

What does the current do then? If it is still high then it might well be that you have excessive drag in the lathe, so maybe you need to find out why? Or if it reduces significantly then it means you have a problem running the motor at 100Hz, in which case I would be talking to the supplier again.

02/02/2017 16:45:31

That no load current doesn't look too bad although it is a bit high, especially compared to John's figures.

But I am guessing it is working ok at 50Hz.

I am not sure what the supplier meant by "quadratic". That is a bit of a vague term, it implies a square law but in practice the function could be basically linear over the range we are looking at! I think fans and pumps can create loads that are roughly the square of the speed but that is not what we are looking at here.......

Unfortunately (as is typical) the motor spec is for 50Hz and no mention of FLA or efficiency at other speeds so this is hard to really judge.

Given it was bought as a kit, surely the supplier should be able to say what the FLA is at 100Hz?. They obviously think it is capable of this (and I think it does vary depending on motor design), so they should know what setup is required on the inverter to run reliably like this.

02/02/2017 16:03:52

hmm... with just the chuck fitted that is no-load, not full load. I would expect less than 2/3 FLA unloaded. I could be wrong but I don't think that what you are seeing is right. I am also concerned the supplier appears to have suggested that having a chuck fitted constitutes a load. That is is not right......

Does the inverter have the option to display the current when it is running. I suspect so (most do) and that would tell you what it is doing at 50Hz. Once you are happy about that I would then move on to other speeds.

fwiw, I would expect less than 2A no load at 50Hz (ie just chuck) on a 3A FLA motor.

Like I said above, my drill is at about 1.7A without load, grabbing the chuck and trying to slow it down (don't try this at home kids....) only gets me up to about 1.8A before my hand/rag starts burning. My point being that it should take very significant load before it gets anywhere near full load current.

02/02/2017 15:19:24

I sort of agree with Ian but with one proviso.....

As Ian says, the chuck will effect the startup current but not the steady state running current. If it is the startup current that is high then perhaps increase the startup ramp time?

I assume from what you say that this current is what is reported by the VFD and hence phase currents averaged. Plus it is the VFD that is "tripping" and shutting the motor down rather than an overload trip somewhere else?

You also don't say if the 5.6A is with the lathe fully loaded. If it is then it doesn't sound unreasonable even if it is a bit high. Personally I would only run it like that for very short periods. If I was machining something that was going to need a bit of grunt I would change the belts to bring the motor speed closer to its design speed (ie 50hz) it will be more efficient and less stressed then.

fwiw, my meddings drill has a FLA of 3A @230V. I have yet to get it past 2A on the VFD display but then I am currently only running at 50Hz and have only drilled up to 10mm holes so far. Unloaded it starts and runs at about 1.7A if I remember correctly.

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