Member postings for Les Jones 1

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.

Les.

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 ?

Les.

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.

Les.

Edited By Les Jones 1 on 12/04/2020 11:01:20

Sorry for missing those points.

Les.

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 ?

Les.

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.

Les.

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.

Les.

They were probably in series as the working voltage of supercapacitors is quite low. (Less than 6 volts from memory.) So the series configuration was probably to get the required voltage.

Les

As John says take some pictures of the inside of the base and tell us if any of the wires from the inside of the motor are connected to anything else such as the on/off switch, mains input cable and capacitor if there is one. I expect there to be three (Or possibly 4 wires wires) coming from inside the motor to the base. If there is no marking on the wires to identify them put some markers on them so that we can identify them when we are telling you what resistance measurements to take.Take a few pictures from slightly different angles so that we can see where wires go without being obscured by other wires. What is the history of the grinder ? For example was it given to you in a dismantled state. Did it stop working and you dismantled it without noting the connections ?

Les.

I too have never heard of " an induction motor with a permanent magnet rotor ". I think Brian's question about it being a 3 phase motor that has been modified needs to be answered.

Les.

I assume that the black wires (U1 & U2) feed the main winding and the red wires feed the auxiliary winding (Via the capacitors on the motor. If this is so then remove both links. Connect wire U1 to terminal U1. Connect wire U2 to terminal U2. Connect wire V1 to terminal V1. Connect wire V2 to W2. Before doing this confirm that the 4 wires are connected as I assume. WITH NO POWER TO THE LATHE confirm that with the forward reverse switch in one position (Forward or reverse. Ignore the off position if it has one.) you get an almost zero resistance reading between wires U1 and V1 and between wires V2 an U2. In the other position you get almost zero resistance V1 and U2 and between V2 and U1. If you do not have a meter I can suggest a method using 4 mains voltage lamps.
If you connect it up and forward and reverse are the wrong way round then swap over wires U1 and U2.

Les.

Looking at the schematic posted in the second post the only output seems to be via the 10 K resistor. This would not provide enough current to power the tachometer electronics. I suspect the 10 K resistor is the load resistor for the optical sensor. (If it does use an optical sensor.) There must be some other source of power to the tachometer. For us to be able to help you you will need to provide some more information. Does it use an optical sensor or some other method ? Can you post pictures of all the circuit boards in the lathe and the speed sensor so we can get an idea of how the low voltage to the tachometer is supplied ? Can you include pictures of the component side and the etch side of the auxiliary control board so we are sure it is the same as the one posted.

Les.

I had the same thought. It would be better if the question gave some more detail. I ASSUME 65mm is the thickness. The answers would be very different between a block 80mm square and a block 1 metre square. (Unless he has a VERY large lathe and mill.)

Les.

This is slightly off topic. A short time ago I was ordering an item fro Amazon and I was in no hurry to get it. I clicked on free delivery thinking it was the free about 5 day delivery but it was for Amazon prime one day delivery. I tried to get back to select the 5 day option but nothing I tried worked, I even tried cancelling the free prime trial offer.I ended up cancelling that order and creating a second Amazon account using a different email address. Instead of taking a few minutes to order the item it probably took about an hour.

Les.

I agree with Bill that it does not look like a three phase variac. It does not even look like single phase variac.(Although the information on the label would match a single phase variac.) Can you post a picture of the inside of the item. If you are familiar with single phase variacs then a three phase one just looks like three single phase ones mechanically linked together.

Les.

Have you checked that it is not the coil in the NVR switch that is causing the hum ? Try disconnecting the output of the NVR switch and see if the hum is still present.

Les.

Your description " with similar results " is not clear. If you have proved that one of the "amplifiers" does not work in either position with either scales then that "amplifier" is faulty. Conversely I assume the other "amplifier" works in either position with either scale. I don't think the fact that the display will change between metric and imperial indicates anything about the "amplifiers" Even if you had a schematic of the amplifier I don't think we could talk you through diagnosing and fixing the fault on the faulty "amplifier".

Les.

My understanding is that you have swapped over the two cable connections at the top right and this proved that both scales work on one of the inputs but neither works on the other input. You should now be able to prove it the fault is one of the "amplifiers" or deeper inside the DRO by swapping the positions of the "amplifiers" in the DRO. So does it always fail with the top position (For example.) or does it always fail with the "amplifier" that WAS in the top position (For example.) ?

Les.

In your first post I got the impression that each scale connected directly to the DRO (The unit with with the displays for the 2 or 3 axis's and the buttons for setting zero points etc.) I interpreted your use of the word amplifier as the internal circuits on the DRO that convert the signals from the scales to the logic levels that connect to the internal micro controller. I am assuming the scales are glass quadrature scales with 2 or possibly 3 output signals that are either sine wave or square wave. Are you now saying that the output of each scale goes via an "amplifier" before feeding the inputs on the DRO. Can you clarify how things are connected together with a block diagram.

Les.

I have done a similar thing using the rotary table to drive the spindle. The table is attached with an adaptor that fits into the end of the spindle and the drive is transmitted with an expanding collet. The spindle supports the weight of the rotary table and the rotary table base is prevented from rotating with an arm attached to a fixed point on the lathe.

The pictures above show it mounted on my Chester DB10G. The second picture shows how the rotary table base is prevented from rotating.

Les.