Here is a list of all the postings Stuart Bridger has made in our forums. Click on a thread name to jump to the thread.
Thread: Ink jet printer woes |
30/01/2020 10:10:39 |
I gave up with a HP cartridge based printer as it was getting through very expensive cartridges at a rate of knots. Also had issues with the print head. So about 6 months ago I switched to an Epson "tank" based system. A bit more expensive up front, but so far so good. |
Thread: High blood pressure ! |
29/01/2020 10:59:53 |
I would get another GP appointment and ask for a risk assessment. They take in a number of factors BP, diabetes, weight, height, chloresterol level, smoking habits, age, gender, etc. The output is a percentage chance of heart attack or stroke in the next n years. Then can re-run the assessment with and without tablets and you may find the difference is minimal. You can then come to a more qualified joint decision |
Thread: Painted T Slots |
26/01/2020 11:29:27 |
How about using an old end mill, and just run it down the side of the slots. I don't expect the travel will allow you to get right to the ends, but it will break the back of the job. |
Thread: Desoldering how to? |
24/01/2020 15:35:06 |
The positive thing is that the OP's PCB is not too dense, with good size tracks and pads so could be a lot worse!
|
24/01/2020 15:29:16 |
Whwn I worked in electronic repair, I had a VERY fine pair of stainless steel pointed tweezers, so fine I was always stabbing myself with them. But they were pefect for working the hole to free stuff up after desoldering Edited By Stuart Bridger on 24/01/2020 15:30:42 |
24/01/2020 12:30:54 |
QUALITY desoldering braid combined with a decent iron would be my answer. If it was an IC or other component, I would recommend snipping the legs, then working one joint at a time. That said I have desoldered quite large pin count ICs complete with success. It will be fiddly to get all 6 connections to the switch loose, but you should be able to do it. |
Thread: vfd |
16/01/2020 21:28:07 |
For a suds pump, you can get away with a motor run capacitor across the 3rd phase. No need for a VFD. |
Thread: Does solder seep into copper plate ? |
16/01/2020 13:48:52 |
Yes soldering does result in alloying between the solder and the surfaces of items being joined. |
Thread: Colchester Bantam power feed problem |
15/01/2020 14:58:00 |
I have the same issue on my Chipmaster, which shares a common apron I think? From memory the article in MEW implied it was quite a task to resolve? If I test it by winding the chuck manually feeding up to the stop, the pressure builds up and then the feed drops out with a hell of a bang. Under power it just tends to drive the stop along the bed. I am just living without the feature although it would be a nice to have. |
Thread: VFD Question |
14/01/2020 08:48:52 |
Posted by Robert Atkinson 2 on 13/01/2020 23:07:59:
Posted by Stuart Bridger on 13/01/2020 17:18:03:
A bit more research on VFD operation (specifically on the Emerson Commander that I use) shows that the the VFD will modulate output voltage progressively up to the "base frequency" set. Above the base frequency full supply voltage is applied and just the freqeuncy is varied This is where the 29Hz comes in. Setting the base frequency to 29Hz ensures that this voltage/frequency curve is optimised for 230V operation. Agreeing with Robert's post above
Edited By Stuart Bridger on 13/01/2020 17:19:52 No it's NOT. The VOLTAGE is reduced when the FREQUENCY is BELOW the rated frequency of the motor. I'll say it again it is FREQUENCY (speed) and CURRENT (torque) that determine the motor power, the voltage rating just sets the current at one frequency. Robert G8RPI.
Robert, I have to say that I completely agree with your statement, effectively you are just describing what happens when you reduce the frequency from base/rated frequency downwards, whereas I described what happens when you increase frequency upwards to the base frequency. Exactly tthe same. |
13/01/2020 21:24:02 |
1. No one has suggested that you don't exceed 29Hz. It is a VFD setting to optimise performance at slower speeds. I can still get the rated 3000 RPM spindle speed out of my chipmaster, albeit with reduced torque. The clue is the V in VFD variable. 2. There is no doubt that this solution is a compromise, but it does work for those who have a single voltage motor and no 3 phase 415v supply available. It was much easier for me to fit a VFD than to replace the motor. It certainly is a viable option that can be considered, IF you don't need the full torque of ex industrial machine. Edited By Stuart Bridger on 13/01/2020 21:25:36 |
13/01/2020 17:18:03 |
A bit more research on VFD operation (specifically on the Emerson Commander that I use) shows that the the VFD will modulate output voltage progressively up to the "base frequency" set. Above the base frequency full supply voltage is applied and just the freqeuncy is varied This is where the 29Hz comes in. Setting the base frequency to 29Hz ensures that this voltage/frequency curve is optimised for 230V operation. Agreeing with Robert's post above
Edited By Stuart Bridger on 13/01/2020 17:19:52 |
13/01/2020 16:30:40 |
The much discussed document from Inverter Drive Supermarket may not be the best worded. What I believe that he is saying that you can get equivalent peformance supplying a 415V motor with 230V up to 29Hz, Efficiency above this frequency starts to drop off. Setting 29Hz as the "base frequency" of the inverter optimises the inverter operation for this situation. Most importantly the full load current must be set to match the motor as it will draw more current for the same power and this needs to be limited ot prevent overheeating the motor. Nowhere in the article does it say don't exceed 29Hz. I run mine up to 50Hz purely so I don't exceed the design rating of the lathe. |
13/01/2020 12:19:01 |
Posted by Steviegtr on 12/01/2020 23:22:46:
I still do maintain that fact. I was not pointing at you. But a star connected motor on 240v will have the windings basically connected in series for each pair so 2 240 windings in series with 240v applied will give a pretty crap power curve Your statement may well be true for industrial use. For hobby use, I have been running a Colchester Chipmaster on 240V with the original 1963 415V motor star connected motor using the 29Hz configuration suggested by Inverter Drive Supermarket for the last 9 years. I have never been lacking in torque/power for the use I put it to. I did try turning 1.25 inch mild steel at 2000RPM witha hefty DOC and feedrate with carbide tooling once. It did slow down the spindle speed a bit, but I was getting seriously hot chips and a stunning surface finish. But that is way beyond my typical usage. Edited By Stuart Bridger on 13/01/2020 12:19:51 |
10/01/2020 16:22:06 |
As mentioned above I use the technique highlighted in the article by Colin@Inverter Drive Supermarket. Edited By Stuart Bridger on 10/01/2020 16:36:01 |
Thread: To use chuck or collets |
10/01/2020 11:12:33 |
Depends what you are doing and accuracy required. |
Thread: VFD Question |
10/01/2020 10:13:55 |
This is a good explanation and the technique I use on my Chipmaster with a 415V star connected motor with a 240V VFD |
Thread: The blind leading the blind |
09/01/2020 12:13:57 |
Posted by not done it yet on 09/01/2020 11:48:15:
Video or pic? Could be a difference between ‘looking at’ and ‘using’. However, eye protection should be the order of the day whenever in that working area - there may be others making flying chips! Most certainly not a good advert. 100% agree. When I worked in industry over 30 years ago, all machine shops were designated eye protection areas. It was mandatory even if just walking down the gangways. Edited By Stuart Bridger on 09/01/2020 12:14:11 |
Thread: Colchester Student Mk1 Won't Start |
23/12/2019 15:07:54 |
if the holes are small, what about coating with an Epoxy sealant? |
Thread: 2nd Hand Hearing Aid Reprogramming? |
18/12/2019 13:50:55 |
I would highly recommend Tripp hearing, not used them for the subject in question though. |
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