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Member postings for Les Jones 1

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.

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Thread: DRO switch
22/01/2011 10:34:13
Hi Bob,
I am making the assumption that these are the quadrature scales with TTL outputs. Here is one way to switch the scales over. (NOTE this will NOT work with the Chinese scale that use 2 x 24 bit protocol.)

Be aware that you can not switch back and forward between machines without resetting the zero reference. This is because quadrature scales do not give out absolute position information. They only tell the DRO that they have moved one unit of resolution up or down. There are many alternative ways to solve this problem for example one of the switches used to switch a parallel port printer between computers.
Les.

Thread: steam turbine and generator
19/01/2011 16:16:48
Hi Andrew,
No it's not you it's me. I must have copied the link from the wrong tab before pasting it into the URL box. Hopefully this attempt will be correct.
Sorry for the error (And for not checking that the link worked.)
Les.
19/01/2011 15:36:20
Seeing Ian's suggestion of using a motor from a blender made me remember some information I had seen on one of the Dyson battery vacuum cleaners.
The DC31 is claimed to use the fastest motor in the world which runs at 104000 RPM.
As this motor will have a rotor on the end of it it is almost a ready made turbine generator.
I imagine it uses the same basic design as model aircraft motors so it would need the inverter electronics removing and being replaced with a three phase rectifier.
Here is a link to a web page with a little information about it.
Les.
13/01/2011 17:29:06
Hi Paul,
               Some of the brushless  motors used on model aircraft rotate at very high speeds.
I think they are really three phase motors with a rotating magnet. One of these and a three phase bridge rectifier might meet your requirements up to about 50000 rpm but I do not think they would survive at 100000 rpm.
Les.

Thread: Adding illustrations to an article
31/12/2010 15:41:54
Hi Richard,
                      Is your statement in your original post  " but I do own the copy right" correct or is it a mistake ? If you did not take the picture I do not understand how you own the copy write.
Les.
 
31/12/2010 11:43:03
Hi Richard,
                     I am not clear about the question. Is it that you have put the illustrations on a web site not belonging to you and have lost the original graphics files ? Or is the question related to copyright ?
 
Les.
Thread: DIY Vacuum heat treatment oven
31/12/2010 10:09:00
Hi Ian,
               Here are two other places you could try for refractory brick.
 
Refractory brick is easy to work. It can be cut with a wood saw.
Do not be tempted to use castable refractory  as this is not a good insulator.  It is suitable for lining a furnace but needs insulating fibre surrounding  it. I have seen wire suitable for heating elements advertised on ebay from time to time.  If you do not need very high temperatures you can make a DIY castable refractory that is insulating using a mixture of perlite,  clay and cement. I made a small furnace for melting aluminium using this and it works very well. It is only suitable for up to about 600 to 700Deg C If you are interested in this let me know and I will try to find the recipe again. I bought insulating refractory brick from a place near Liverpool airport. (Which may be close enough for you to collect,) But his website is not working so he may have stopped trading. I probably have his email address and phone number so you could contact him to see if he has what you need. Again let me know if you want this information.
Les.
 
 
Thread: Anyone used an Inverter with a Colchester Student
14/12/2010 15:12:27
Hi Hugh,
                  The answer to your question depends on the design of the inverter. If the inverter has the neutral point connected to earth then the input RCD will not trip if there is a short to earth on one or more phases (Or if you touch one phase.) In this situation you would receive a shock (240 volts) (Or the inverter would be damaged in the case of a short to earth.) If the output was floating a short to earth on one phase or you touching one phase would not trip the input RCD. The difference with the first situation is that you would not receive a shock or the inverter would not be damaged. If one phase was shorted to earth and you touched another phase you would receive a 440 volt shock. Again the input RCD would not trip. The way an RCD works is to detect the difference in the current in the neutral and live (3 lives in the case of 3 phase.) If there is no short to earth then the current in the neutral will be exactly the same as the current in the live. (Or the vector sum of the current in the three lives.) I think it would be a good idea to put a three phase RCD on the output of the inverter. NOTE even an RCD will not protect you from touching two phases or live and neutral.
Les.
Thread: Horses for Courses
10/12/2010 10:26:09
Jeff Dayman has answered that question in his reply.
Les.
Thread: Pprojecting a circle onto a boiler barrel
08/12/2010 09:21:25
Hi Vincent,
                    You could make a tool similar to the hole cutters that Toolstation sell but with just one blade sharpened as a scriber. To see a picture of the hole cutter on Toolstation's website enter "hole cutter" in the search box. If you drill a pilot hole and mount the mount the tool in a pillar drill or some kind of guide you can let it move up and down to keep the scriber in contact with the surface as it is rotated. I used this method to cut a hole for the burner in a furnace that I was making. For that the scriber had to be quite long at the hole was tangential. I was cutting a hole about 2.5" dia. in a cylinder of about 13" dia. It has just occurred to me that if you use two blades then keeping both blades in contact with the surface would remove the need for a guide IF the axis of the hole being cut goes through the centre of the main cylinder.
Les
Thread: speed control pcb for Clarke CL300 lathe
23/11/2010 09:17:25
Hi Bill,
             I have noticed this morning (23/11/10) that someone is selling a control box for a Chester Conquest lathe on Ebay. I think this is the same as the CL300. It is faulty but could probably be repaired   The item number is 290503483892  It is a pity that you have already ordered one.
Les.
Thread: The Impecunious Engineer
12/11/2010 18:32:24
Hi Chris,
                  One thing you could try is to have a suitable value high power resistor in series with the supply to the welder and a high power relay (contactor) with the coil connected in parallel with the welder. Connect the contacts on the relay across the resistor. When first switched on there will be a significant voltage drop across the resistor so the relay will not pull in. When the initial current surge has gone away the relay will have enough voltage across the coil to pull in. The resistor will then be shorted out. The resistor needed would need to be between about 2 an 5 ohms.  You would probably have to make a suitable resistor from a long length of wire coiled up.
Les.
Thread: Restoring a steam engine
10/11/2010 12:15:18
Hi Jan,
                 To include pictures in a post you first have to upload them to "My photos"  (To do this clock on "My photos" near the top left of the web page.) Once you have them there you can add them to a  post by clicking on the "Insert image" button. (Next to right button at the top of the box where you enter the text .)
Les.
 
Thread: current indicator
06/11/2010 14:58:55
Hi Gordon and John,
                                      I have just re read the original post. The 100 meter run of cable  will have a significant capacitance causing some current to flow even when the pump is not running. This will probably be enough to light the LED dimly so a resistor will probably be required between the ends of the string of diodes. (I would suggest about 27 ohm as a starting point.) It may be better to use a 3 volt torch bulb instead of the LED, diode and resistor.
 
Les.
06/11/2010 13:01:05
Hi Gordon,
                    I think this is the item that John mentioned.
 
Les.
05/11/2010 22:18:36
Hi Gordon,
                    Although  there are no suitable diodes on Ebay there is someone selling 35 amp bridge rectifiers for £1.45 Here is a modified design that can be built with two bridge rectifiers.
 

D1 only needs to carry about 20 mA so almost any diode would do. This diode is to prevent reverse biasing the LED with about 2.8 volts. 
Les.
05/11/2010 15:21:02
Hi John and gordon,
                                        John, you are correct. I have drawn the LED the wrong way round. One other thing I did not mention is that the circuit as it is will not work with a white or blue LED as the requre about 3 volts.
Gordon, I would go for 10 amp diodes as the starting current on some types of motor can be very much more than the running current. The energy saving extension lead has one socket that the main load is plugged into. The other sockets are only powered up when the main load draws current. (For example a computer as the main load and monitor and printer plugged into the other sockets.) If you used this method you would plug the pump into the main socket and say a table lamp into one of the others. There are also plug in energy monitors that diplay current or power. 
 
Les.
05/11/2010 12:44:24

Hi Gordon,
                      If an LED indicator w ould be bright enough you could try this circuit.
 
It would be connected in series with either the live or neutral feed to the pump at the house end. The diodes need to be able to withstand the starting current of the motor. They only need to be a low voltage rating as they do not have the mains voltage across  them. You could also use a 3 volt torch bulb (Without the series resistor.) If you did this then replacing the lower diode with a string of four would make it brighter.
Les.
Thread: M4 coupling nuts, where can I get them ?
11/10/2010 22:18:08
Hi Murray,
                   From John S's  suggestion Farnell have standoffs. Here is the link to the web page. Farnell standoffs    The postage would make them too expensive if you only require a small number.
Les.
Thread: Rhoestats
08/10/2010 20:24:35
Just a clarification to my last post. I do not mean a resistor across one diode of a bridge.
I mean as a single diode as a half wave rectifier.
Les.
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