Here is a list of all the postings Les Jones 1 has made in our forums. Click on a thread name to jump to the thread.
|Thread: 3 Phase in a Model Engineers workshop|
One important question asked by Andrew Johnston on 14/6/20 at 09:31 has not yet been answered, I was thinking of doing a simple test using 6 old fashioned mains filament lamps of 60 to 100 watts rating. (All the same rating) The idea is to have three series connected pairs of lamps with each pair connected across the three phases on the motor. (Making the connection at the output side of the thermal trip that feeds the spindle motor is probably the easiest.) The brightness of the lamps would give a reasonable idea of phase balance.(50 watt GU10 bulbs could also be used as they are easier to obtain. ) Another test that could be done is to disconnect the spindle motor at the output of the thermal trip and see if the contactor stays in and the coolant pump motor runs. I am inclined to agree that someone is required on site who is used to working on three phase motors and tracing exactly how the contactor maintainer contact and interlocks are wired.
Edited By Les Jones 1 on 14/06/2020 09:21:39
It sounds like the contactor is not holding in. Is the start button just a push button switch or is it the type were the button actually pushes the contactor closed ? (It is probably just a push button as I have only seen the type were the start button pushes the contactor closed on hobby machines.) The start button is normally wired in parallel with an auxiliary contact on the main contactor. WITH THE MACHINE ISOLATED FROM THE POWER connect your multimeter set to a low ohms range to the two connections on the start button (You will probably get a reading of a few tens or hundreds of ohms at there will be a path through other circuits.) Now manually push in the main contactor. The resistance reading should drop to almost zero ohms.If you can post the internal wiring diagram of the machine that would be a great help to suggest other possible causes of the problem. I first thought the problem might be inbalance between phases but the fact that the contactor pulls in while the start switch is held in disproves this theory.
|Thread: component tester|
I think you need to give more details than just "A component tester" For example model number, manufacturer, the magazine article you built it from. I think it is expecting a lot for it to be recognised from just a picture of the display.
Edited By Les Jones 1 on 08/06/2020 08:47:59
|Thread: Lathe motor|
A series wound motor is a bad choice for driving a lathe as it's speed varies a lot with load. They can be reversed (Both when supplied with AC or DC.) but you need to change the internal wiring of the motor to reverse the relationship of the current through the armature and the field winding. If you supply some details of the motor that is fitted that may be a better option than the Kenwood motor.
|Thread: Clark CL430 question on threads|
If it gives a change wheel setup for any thread you should be able to work out the leadscrew pitch. If you can't work it out post the information here ant there will be may members that can work out the leadscrew pitch.
|Thread: Oscilloscope kits - any recommendations?|
7 BCD Scales
Static state of clock line between frames Low
Clock in the data on the negative going edge.
28 bits in a frame of data
CPI 2540 (Metric)
LSB sent first
Static state of clock line between frames Low
21 bits in a frame of data
Data is sent as two groups of 24 bits.
Static state of clock signal between frames Low
The first group is the absolute position. It has some arbitary value at power on.
48 bits in a frame of data
HF (Bin 6 scales)
Static state of clock line between frames High
Clock in the data on the positive going edge.
The data output is the number displayed on the LCD display.
24 bits in a frame of data
CPI 2540 (Metric) (2000 in imperial mode.)
This is only half of it as it would not let me include it all in 1 post. The rest is in my next post.
|Thread: Motor Reverse|
Assuming that the black cable is the only other cable going to the motor as well as the blue cable to the capacitor then if the black cable is two conductors plus earth then the motor can't be reversed externally. If it is four conductors plus earth then it probably can be reversed externally. If you are prepared to take the motor apart then it may be possible to reverse it. This may involve digging into the end of the winding to get at the point where one end of the start winding is connected to one end of the run winding and to an external wire. the connection between these winding ends would have to be separated and brought out as two separate wires.
|Thread: Cutting down a linear glass DRO encoder|
Here are pictures of my plug.
Looking an the Farnell website I think I have identified the connector as a Binder 680 series connector.
They are quite expensive so I think I wil try to make some kind of connector to test the scale. When I know it is OK I will fit a different connector to the scale.
|Thread: What are you doing|
Have a look at this design for a saw table for these band saw that folds out of the way when using the bandsaw horizontally.
|Thread: RCD socket|
|Thread: Imperial V Metric|
If I was cutting a 2.4 mm wide slot I would not use a 2.4 mm cutter even if I had one. I would use a 2mm cutter to cut a slot that would probably be a little over 2mm wide. I would then clean up the sides taking light cuts until the slot was 2.4 mm wide.
|Thread: Brook Cub 1/2 hp Motor - Capacitor or not?|
I suspect it could be the centrifugal switch in the motor sticking in the open condition. The click may be the switch dropping back to the closed position. Have a look inside the dewhurst switch and check how many wires (Other than the earth wire.) go between the switch and the motor. If there are only two then the fault is almost certainly in the motor. If there are four then post a diagram of how they are connected to the switch. Do you have a multimeter ? This is so we can get you to do some tests to prove it is not the dewhurst switch. Is the switch a forward - off - reverse switch or just off - on ?
|Thread: Wiring LED battens|
Do the wires to the original two lights come out at one point in the ceiling or two ?. Also how many wires come out at each point on the ceiling ? There may be more than three wires coming out out of the ceiling. One may be a permanent live which is joint to a wire going to the switch. There could be a third wire joined to this point taking the live feed on to feed something else.
Edited By Les Jones 1 on 12/04/2020 11:01:20
|Thread: How do I drill this hole|
Sorry for missing those points.
As the circle is 60' diameter i agree that the wheels are on the same axle does not matter. I am confused as it is a fully functional replica car how you are going to drive the axle. Are you going to machine out the diff housing and use bevel gears so the drive system is similar to the original or is the drive via spur gears or belt to a point close to a wheel ? If it is the second method how can it be considered a replica ?
Would it not be easier to have the bearings in the wheels and the axle fixed. If it was done that way the hole would not need to be so precise. It could be clamped in position with grub screws. Also if it was to be a working model the wheels should not be locked together.
|Thread: DC-DC converter|
They take almost no current so there is no need to use a switching regulator to save power. There is probably noise on the output a the switching frequency. I suggest using using an LM317L linear adjustable regulator and also fitting a few uf tantalum capacitor mounted in a dummy battery in the battery compartment of the calliper.
Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!
You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.
Click THIS LINK for full contact details.
For subscription issues please see THIS LINK.