By continuing to use this site, you agree to our use of cookies. Find out more

Member postings for Bob Mc

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

Thread: Astronomical Binoculars.
27/12/2016 18:35:29

Hi All...

I seem to have generated some interest with my larger than normal pair of binoculars.

To give a little bit of history for those who may not have seen the thread containing the description; I was given the parts for the binoculars as the original owner had no means of providing a mount suitable stand for the telescope; it was mounted on a simple steel post which although providing a means of adjustment, made viewing any heavenly body near the horizon practically impossible unless you had been trained in yoga.

The telescope is quite heavy....you can't lift it manually like a normal pair of binocs, it is about 48" long and some 28" wide, and so the original owner could not use it.

For those not familiar with these sorts of telescope, being a Newtonian Reflector you have to look down the scope to look up at the sky, which is ok when looking directly down the scope as it is some 4ft off the ground .... but when the heavenly body is horizontally positioned you have to get down to take advantage of it.. ... and so I made a new stand have a look at the pics...

Right....any questions... rgds...Bob...

Below.....Scope on original stand..

dsc_0324.jpg

Below... Scope on old stand, you can see it is difficult to get to eyepieces when heavenly body is near horizontal position.

dsc_0003.jpg

Scope on new stand I designed using automobile gearbox lifter.

Binocs on new stand.

Eyepiece arrangement which can be completely remove from the tubes for cleaning etc.

dsc_0029a.jpg

Hope it provides some interest....

Thread: Screwcutting Clutch for Myford Lathes
10/12/2016 22:14:45

As promised some more pics of 2x6 inch reflecting binocular scope..

nb.....Sorry I seem to have taken over this thread .... my apologies...

I forgot to mention that collimation of the two mirrors can be done whilst observing, this is a necessity as I have to trundle the scope across rough ground and it gets a good shake up every time..

The pics... rgds....Bob.

Collimation adjustment knob...right tube.

dsc_0034b.jpg

Mirror Cells collimation adjusters.

dsc_0028b.jpg

Inter pupil distance adjuster.

dsc_0328.jpg

A look down the eyepiece end.

dsc_0330.jpg

Slipping magnetic clutch

dsc_0035b.jpg

10/12/2016 21:53:50

Hi Neil...

The 2x6 inch scope has turned out to be better than expected, I would say its similar in image quality to an 8 inch reflector but with a more comfortable viewing situation.

I had some problem with the original stand because although it was easy to look down into the eyepieces when the scope was pointed in near vertical positions, but when oriented horizontally I had to crouch down to get to the eyepieces which made any observation uncomfortable. So after much searching and deliberation I bought an auto gearbox lifter and altered it .... I can now adjust it eyepiece level to suit the height of the observer and the altitude of whatever is being observed.

The Azimuth bearing is the actual ram support of the unit and is surprisingly smooth, I fitted a manual slow motion drive to the Alt bearing for fine tuning, this is coupled by a magnetic yoke to the OTA's Alt support so that at any time one can 'grab' hold of the tubes and move it about.

Will post some pics ..

rgds....Bob.

10/12/2016 15:53:02

Thanks Cloggs...

It is true that I do have more time on my hands nowadays but after 50 or so years of working I need a break!!

Thanks for noticing the workshop is reasonably clean, but if you have ever suffered from the 'gremlins' which hide tools and bits as other members of the model engineering fraternity have mentioned, then the only option is to tidy up and in the process SOME of the stuff will be found!!

By the way there is no future article about the machine, there was however the original article about using Arduino processors for the screwcutting and leadscrew control of the lathe....see MEW issue 235.

I try to keep busy as best I can and on those cold rainy days I could sit in front of the telly and watch Parkinsons adverts for funeral insurance .... you get a free pen you know...just what everyone is in dire need of..!

I have been busy re-making a binocular reflecting telescope as well as fixing up the lathe and doing other things...will post some pics...

all the best rgds Bob.

dsc_0027.jpg

10/12/2016 11:10:37

Thanks Cymro, Michael G...

... I have now fitted a DC treadmill motor to the lathe, so its features are ... forward/reverse spindle, variable spindle speed, screwcutting any thread...and slow to fast leadscrew motion; all these functions available without changing gear wheels or having to listen to metal gear clanking noises.

will post some pics...

rgds...Bob. underneath... lathe now with homemade pulley cover.... the black box on top is for rpm readout...not got round to that yet..!

dsc_0028.jpgdsc_0027.jpg

Fitted to lathe.. a 20tpi inside thread mandrel nut I made using the screwcutting feature.

10/12/2016 09:50:50

In response to Cymro..

I don't know if this post should be in 'Screwcutting clutch for Myford's' ... my apologies to Neil Lickfold.

There was a forum discussion about some aspects of using Arduino's for controlling the leadscrew ... see 'Syncing up Arduino's'... the article was in MEW issue 240... this was my own design and was really an overview of what I did to my 70 year old lathe in order to get round the problem of providing a screwcutting facility and motion control of the leadscrew since the back gearing on this lathe did not exist and the original leadscrew was worn out.

In the space and time I had available for the article some of the features were not really covered, such as the fact that there is no encoder as such and the design is probably the most cost effective way of solving the problem when faced with the choice of buying a new lathe or having a go at re-modelling an old lathe.

Since I made the controller quite a few years ago there have been improvements and a re-thinking of the original design as I understand that only one processor is now needed to provide the signals for the leadscrew and headstock motors so that connecting (syncing) the two Arduino's is not needed.

I am not pursuing this re-design as I am very happy with the control unit I have, it works a treat and I have made quite a few threaded items, the only problem I have had is that the headstock stepper driver motor is underpowered somewhat and care needs to be taken to ensure that the cuts are not too heavy and the threading tool is sharp.

The 'different contributor' you mention was probably Chris Gabel who wrote a great article about using the Electronic Leadscrew Groups device (see iss 235 MEW), and I have no doubt that this is a much better system than the one I designed, and as he mentions there is plenty of backup from its vast member base, however this is not a cheap option and I would argue that the cost of applying the system to an old lathe needing refurbishment should be considered against the cost of purchasing a new lathe.

Well I'm happy to answer any questions you may have...

rgds...Bob.

Thread: Things to save from a CRT TV being scrapped
10/09/2016 11:01:04

I had worked as a tv engineer for many years and dealt with changing the old black & white and CRT colour tubes, one thing you may not be aware of is that the high voltage used for colour tubes around 25kV charges up the glass dielectric just like a capacitor, and the charged glass slowly releases its charge over quite a long period of time into the 'plates' producing a very high voltage.

The same goes for the black & white tubes but with only about 16kV.

So...when handling the tube, don't put your finger in the little connector hole!!! even if it was months ago that the tv set was used and even if you short the thing out with a couple of screwdrivers from the hole connector to the outer coating of the tube..! it can re-charge itself and give you a nasty reminder that the electric stresses in the glass are still there.

I don't advise smashing the tubes and there is not much inside to use, the colour tubes do have a 'shadow mask' which is like a very fine sieve .... please also be aware that on being smashed a kind of dust seems to be emitted which may be the phosphor from the screen.

..Bob..

Thread: Neil in for Overhaul
06/02/2016 20:48:14

Best wishes and hope you get well soon...

Bob..

Thread: Patrick Moore in Model Engineer
30/12/2015 21:38:23

The binocular telescope was originally made by a member of the Manchester Astronomical Society, it has lain neglected in a garage for some years and the mirrors were in dire need of re-silvering, the inter pupil distance mechanism was also badly made and I re-made it all using perspex. I am told by the company who have done the mirrors that their tests showed that they are identical in focal length and accurate to 1/8th wave...I have been told that the views of the moon are particularly good and seems like you are hovering over the surface...

I will let you know...!

pic of inter pupil mechanism.

dsc_0328.jpg

30/12/2015 16:42:29

dsc_0323.jpgHi Neil & all.....

am at present re-building a 6 inch reflecting binocular telescope... awaiting mirrors coming back from re-silvering.. hope you like pics...

dsc_0324.jpg

Thread: Syncing up Arduinos
18/12/2015 21:17:49

Thanks John A Stewart for sharing your cnc groups ideas which seem very comprehensive, I can't help asking if you know if the Atlas/Craftsman lathes were made in Michigan ...?

Also thanks to Martin for clearing up a question I had about Mach3 for a lathe, and Mr Q for his words of encouragement .

I would agree with Mr Q, that it would be better to see what other designs are in the pipeline before committing yourself to any particular design, at least these days there is something to use as a model, I hope our Editor Neil would give us a hint in the magazines or in the forum as to what sort of solutions others are going to be submitting for publication, and using his editorial skills I have no doubt he could do this without spilling all the beans..!

nb...were you employed in the communications/radio industry..? I can't help but have a smile when I greet you with..... Hi Q..! (refers to inductor quality).

Thanks also to Mr S.O. Duffer for taking the trouble to have a look how Arduino clocking varies, and his program for providing two tones... I have to agree with Mr S.O. Duffer that using Arduino based systems for CNC is probably not the best way to go, however others have produced something which is very impressive, unfortunately the one I looked at on Utube was all in Russian and there were no details of how it was achieved.

rgds...Bob..

17/12/2015 18:20:30

Hi all again....

with reference to John Haine's and Martin Connelly's posts, I had a quick look at the Mach3 cnc system and it is very impressive and to be honest is probably the way to go if you have the equipment..... and therein lies the problem..., from what I can ascertain, and I may be completely wrong, but is it not the case that you need a proper cnc lathe with digital encoders and ballscrew drives for Mach3 to be of any use?

Please don't think I am being discourteous to your posts or finding fault, I have been on the receiving end of this sort of response in other forums and it can be very dis-heartening.

Unfortunately my old lathe which is about to have its 70th birthday soon does not have the benefit of these new fangled devices and it would not be economical to try and fit them at this stage in its life, the idea behind using the Arduino system that I have outlined is that it does not require any encoders and will operate with whatever type of leadscrew is installed.

Please correct me if I am wrong, and again I thank you for the interest shown in my article on using the system I described.

rgds..Bob.

17/12/2015 10:28:01

Andy...

you are my hero..!! ha ha ha.... lawnmower...!! that's great...

thanks...bob..

17/12/2015 09:24:01

Thanks to all for your interest, in defence of my design which was started some 7 or 8 years ago there were not many designs aimed at the particular problem of providing an electronic gearbox to replace change wheels on a lathe at that time.

I have to tell you that in no way was I expecting to publish an article on this, and it was something that I required for my own use exclusively. My knowledge of programming Arduino's at the time was zero, I specifically had to learn about it for this project.

I certainly did not want a full CNC system which the Electronic Leadscrew Group were producing, I needed a simple effective and cheap as possible solution to the problem otherwise it would have been much easier to purchase a lathe with everything ready and working.

I can understand why the idea of syncing two boards seems to be like 'cutting the lawn with scissors!' however at the time the main concerns I had about using 2 separate boards were that, yes, they might drift...especially as they had resonators fitted and were of Chinese origin, to be honest I was not over confident about their quality.

I decided to to do a few simple experiments to ascertain how much they did actually drift, however with no proper measuring equipment the only recourse of action was to program each board with the Blink program set to 500ms periods and see if they stayed in sychronisation, it confirmed my suspicions, after perhaps a minute or so I definitely detected a change in the blinking phase.

I was also concerned as to whether variations in supply voltage and temperature variations would affect these things, and I was also aware that there would be a difference in frequency of the two oscillators and that perhaps as one increased in frequency the other might be going down.

After much deliberation and not wanting the onerous task of wiring up for one resonator I had to make a decision, would I take the risk of perhaps ruining a piece of turned work I had spent much time and effort on for the sake of a few minutes of re-wiring? or just get on with it and at least be sure that if there were any more unknown gremlins lurking in the shadows then this would lay them to rest.

One member has suggested using a computer to derive the signals for the drivers, which is ok but then you need a monitor and a keyboard as well next to your lathe, yes you could use a laptop, which nowadays are much cheaper than when I started, in fact many things have changed over the time since I started building it and I would have perhaps designed differently in light of hindsight.

I hope this explains some the reasons for the design, and I hope it shows that an old lathe can be given a new life with a little bit of effort which has become easier since the introduction of new boards and a better understanding of using the Arduino's

All the best for Christmas..... Bob.

14/12/2015 18:28:11

Hi Jason.... another good question..!

Andy has hit the nail on the head in his response.

Basically use could have been made of a more powerful processor which would in principle have the capability of providing 2 sets of independent clock pulses from the one processor.... however and unfortunately the Arduino can't do this.

I have to admit that although I worked in electronics for many years I was not involved in programming.

I decided some time ago that it was rather pointless to start learning programming when I had so many other things to take up my time and interest.

the Arduino programming was however much simpler and the open source ideology along with the many forums and articles makes the whole thing less daunting than trying to get to grips with full blown programming.

As stated in the article... 'there are I am sure other ways of doing this' ... and I have recently been told that one of the Atmel processors is capable of providing the required pulses, but I have not pursued it.

My idea in using this system of two Ard'os just kept it simple and easy to understand although wiring up for one clock is not the easiest thing to do.

If you are really considering having a go, I would try to do the wiring of the xtal clock circuit done first and test it using the 'Blink' program ... if the two Leds keep in sync over a minute or so...you are in business...!

The other thing that didn't come out in the article very well was the fact that if there are any overall errors in the leadscrew pitch, this can be accommodated with the system and as stated my leadscrew is just a piece of threaded rod, ....will provide details if you need them.

Please remember that this is a 'model engineering project' and although I have produced a number of different threaded items such as a spindle end nut for my Atlas lathe, the spindle motor of 3.1Nm is not really capable of taking deep cuts and an amount of experimentation is needed to determine what it will actually cut, in hindsight I should have fitted the next higher power of stepper motor, something of the order of 5Nm, the drivers I mentioned are capable of powering a motor of that size.

Any more info required..... I am only too pleased to help.

rgds...Bob.

14/12/2015 16:35:53

Hi Andy... A good question...!

The reason why synchronisation of the two Arduino's is necessary is that the two motors (one drives the leadscrew and the other the Spindle), need to have their relative speeds constant, notice the term 'relative' .

For example if the required ratio of Spindle speed to Leadscrew speed was 1:4 then for 1 turn of the spindle there would be 4 turns of the leadscrew ; if the pitch of the leadscrew was 1mm then 4 turns would produce a pitch of 4mm on the work.

Now if the Arduino driving the leadscrew motor began to increase or decrease its speed relative to the Spindle motor speed, the ratio of 1:4 is altered and the required pitch on the work would no longer be 4mm.

It is an unfortunate fact that no matter how good the clock circuits are in any two microprocessor systems they will not keep in sychronisation if they are completely separate systems.

The Arduino can only provide a minimum clock pulse period of 1microsec duration, using two Arduino's the clock pulse rates will most certainly alter over time which is the root cause of the problem, and so by using only one clock for the two Arduino's the problem of clock drift is eliminated.

It might be thought that the difference in speeds would be so small that it really wouldn't amount to much, however when the work requires long pitches to be made all the errors begin to add up, If you have two Arduino's just try the Blink program with a 500ms delay period for switching the Leds on & off... it won't take long for the two Leds to be out of sync.

Hope that helps, if you need any more info I am only too glad to help.

rgds..Bob.

14/12/2015 15:23:25

Hi Andy...

I wrote the article about using Arduino's .... if you need any information just let me know on this forum.

..rgds...Bob McMenemie.

Thread: Affordable CAD software?.
13/12/2015 12:39:33

Thanks everyone for the responses...

its great to know that once you are a member of this forum there is a wealth of information from people that understand the situation and have the experience to provide a solution...

Thanks .. will be spending some time looking at your suggestions.

..Bob..

12/12/2015 19:48:06

Please let me know if this has already been discussed, however I can't find any reference in the Threads for this topic.

I would like to make a start producing drawings using some sort of CAD, however I was blown away when I saw the price of Autocad..!!

is there anything that would be suitable for model engineers and which could be used for uploading to ME magazine for example, surely there must be something reasonably priced....well less than £50 in my case or its out of my league.

Have looked on Ebay and although there are copies of what is claimed to be Autocad, it appears that they are either free trials or somewhat legally 'iffy'; in the first case I don't want drawings disappearing from my files after a certain time, and in the second case I don't want to end up in clink..!!

Thread: Screwcutting Clutch for Myford Lathes
28/03/2015 19:54:36

Re: Hi Q...

I do apologise to Neil, he has actually sent me a message on the 17th, I am new to these forums, did not realise I had an 'inbox'.

Bob.

Magazine Locator

Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!

Find Model Engineer & Model Engineers' Workshop

Latest Forum Posts
Support Our Partners
Eccentric July 5 2018
rapid Direct
Warco
MIDLNDS GARDEN RAIL Jan 2022
emcomachinetools
cowells
JD Metals
Eccentric Engineering
Subscription Offer

Latest "For Sale" Ads
Latest "Wanted" Ads
Get In Touch!

Do you want to contact the Model Engineer and Model Engineers' Workshop team?

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.

Digital Back Issues

Social Media online

'Like' us on Facebook
Follow us on Facebook

Follow us on Twitter
 Twitter Logo

Pin us on Pinterest