Member postings for David Brown 9

I bought it quite a long time ago from Galvoptics in Basildon, Essex, I can't remember how much it was, but it wasn't cheap! You can also use two right angle prisms (for example from an old binocular). I tried this but didn't have much success.

I have been making and improving the intereferometer for quite a long time, I will hopefully get there eventually! There is a Bath Intereferometer yahoo group, I have posted on there once and will again once I have made some more progress.

Thanks for all the replies. I bought some Araldite rapid steel two part epoxy adhesive from Halfords and this seems to have worked fine. Despite the name it appears to work on most metals. The 2 aluminium square tubes are small, 20mm wide and quite short

This is for my Bath intereferometer for testing telescope mirrors, which I am trying to improve. It has nothing to do with a bath you wash in! It is named after the German scientis who invented it.

One of the square tubes will hold a small laser diode and the other one will support it. The joint has to be fairly strong but not incredibly so, I will not be applying any force to the joint.

The interferometer isn't actually that complicated to make, but I tend to be in a bit of a rush and not plan things out properly, so end up having to improve/modify them. I still have some way to go to get it working right.

David

I need to glue 2 small pieces of aluminium square tube together. Can anyone recommend a good glue?

David

The quote was from Fays Metals in Acton, London, and included V.A.T. I live in London, but quite far away from Acton. I don't actually need this yet, it is for the mirror cell for a 20 inch telescope mirror. I haven't made the mirror yet and it could take a long time!

I was thinking I could save on delivery, but it seems I can get the aluminium delivered more cheaply than going and getting it ! I have a travel card for work so going to Acton wouldn't cost me anything.

I need some long tubes of aluminium eventually as well and so may well wait and order everything together.

David

Hi, I have been quoted £138 for a 6 mm thick 70 cm square sheet of 6082 T6 aluminium.

Is this a reasonable price? I have never bought it before so I don't have any idea!

Also, how heavy will this be (roughly)-could I carry it? I don't have a car and don't want to pay any more money for postage.

David

Thanks a lot. Amazingly quick answers! Unless I missed something this does not appear to be available in the UK?

Do patents expire after a certain number of years? Also, if something is patented am I allowed to make it soley for my own use at home?

However, being realistic I have just got a mini-mill which I haven't had time to set up or use yet, I think it will take me around 6 months just to get the hang of making simple things on it.

So making an optical chuck would be a bit overambitious at the moment!

It is a very interesting idea to go on my long list of future projects.!

David

I have read a passing mention to something called an optical drill chuck for use in a milling machine on an American amateur telescope making website.

Can anyone explain what these are?. Also, is it possible to buy them in the UK?

David

Thank you for all the advice and offers of help. I am in London by the way (but originally from Yorkshire),

I managed to remove the head and column together from the base and get the mini-mill on to the table. I would have rung Arc for advice, but couldn't as I was at work on Friday.

To start with I thought I might be able to lift the whole thing, until I realised how heavy it is! There is an American on Youtube lifting an American version of the SX2 on to a table. All I can say is he must be incredibly strong! And he did struggle. Don't try this!

When the head and column are unbolted from the base they tend to tip forward as they are heavier towards the front., I covered the x y table with some thick cardboard just in caseithey fell forward, but i managed to hold on to them.

I won't be using the mill for a while. As I said before I have a big telescope mirror I am making which I need to make some progerss on before starting on the telescope, The mini-mill will come in very useful for drilling accurate holes and milling some aluminium parts for the telescope. I have a lot to learn!

David

Hi, I had a Sieg SX2 Plus Mini Mill delivered on Monday from Arc Eurotrade (excellent service), I have been building a hopefully suffuciently strong table for it. Soon I will need to get it on to the table.

As it weighs 60kg I will not be trying to lift it! I have no room in my small flat for lfiting gear, and anyway I am spent up for the time being! So I need to take it apart so I can lift it a peice at a time. I have found information as to how to take apart the x y table.

Can anyone advise me how to remove the head?

Also I presume I need to remove the grease from the table etc? I read somewhere that WD40 can be used?

David

Hi Neil, I have read most of that thread and post quite often on Stargazers Lounge! (I am 'Dark Star'-after my favourite science fiction film).

That thread is the reason I am estimating 6 months to a year for the grinding, testing etc. of the mirror, and it could easily be a year and a half! Or even two years!That is the main reason I want to make a mirror grinding machine, to make the process faster. It has also taken me around a year to nearly finish my 14 inch mirror and telescope. The mirror is ready for aluminizing, which means it is basically finished, the telescope needs a bit more work but should be finished in 2-3 weeks.

David

By the way I bought the single phase motor from a Machine Mart store, I should probably have asked questions but the person who sold it to me did not give the impression of knowing anything about electric motors. When I said 'I think I need a starter as well?' he shrugged with complete disinterest!

I cannot imagine an electrician would charge less than £200, probably more, to connect up the motor, this makes the total cost too high for me, especaily as I have just bought a mini-mill!

I will spend the next few weeks reading about electric motors motors and electricity. For a start I will get Electric Motors by Jim Cox in the Workshop Practice Series.

When I think I have a reasonable understanding I will post again on how I think the motor should be wired. It may be in a few months not weeks! If I am confident I understand how to wire the motor, NVR switch and starter I will go ahead, after getting further advice on here, if not I won't. On the other hand, if the drill press motor works reallly well maybe I won't bother!

David

Oh well, on to plan B. I see no reason that I cannot use the motor from my existing drill press. In fact I should be able to use the main part, with the motor and drill, without dismantling anything. It anyway comes off the pillar easily. I can make the grinding machine so that it is easily removed. A number of d.i.y. grinding machines on line have a motor which is easily removed.

I can then use it again as a drill press when I need to, I am unlikey to need to for a few months.

The drill press has a NVR switch . It is a Titan 700 watt drill press, model number TTB541DBT, bought from screwfix. The lowest RPM is 210.

I will possibly try to figure a way to attach a pulley to the drill press chuck/taper. If this is not a good idea I could try using one of the pulleys that are used to change speeds on the drill press, without removing the pulley, I could posssibly use one of the existing belts or buy a new one if necessary, once I have calculated the length needed.

The only problem is that there is a safety mechanism which stops the motor starting when the cover where the pulleys are is open, I could figure out how to disable this or I could probably cut a hole in the cover for the belt to the second pulley to go through. The cover is rather flimsy, possibly tin?

I have bought a washing machine pulley which is 101/2 inches in diameter, I will work out the size needed for the second smaller pulley and length of belt.

I plan to use the machine to grind for no more than 2 hours at a time. I will not be leaving the machine unattended for more than very short periods as I will need to keep adding grit for grinding at frequent intervals. If I use the machine for only 4 hours in total a day at weekends I will double the amount of grinding I can do, as it is hard physcial work and I cannot see myself doing more than 2 hours a day maximum by hand, probably less.

I am not very fit and I am not as young as I was!

David

Sometimes I am not very clever, there is a very small wiring diagram inside the cover of the motor!

It is headed connections, in two parts, CCW and CW. To CCW it shows two LINES,, one going to W2, U2 and V2. The other to U1, V1 and W1, I will have to double check all this when I find a magnifying glass as the numbers are very small, but I think I have got them right!

There are 2 LINES to CW, one to W2, U2 and V2, the other to U1, V1 and W1.

Any advice gratefully received! I will try to take a picture of the wiring diagram, increase the size and post it on here, once I fiigure out how to do this, probably at the weekend.

David

So I could use the starter I have from Machine Mart and the NVR switch from Axminster and that would give me protection against overloadinng and posssible burning out of the motor and a no volt release so that the motor would not start up again after a power failure?

I need to know how to connect the motor to both the starter and NVR switch. There is no obvious way of connecting the motor to the electricity supply or anything else! I presume I need electric cable-any advice on what to buy whould be appreciated.

On taking the cover off the motor there are 6 terminals, to one side of these there is a motor starting capacitor on the other side there is something that looks similar to the motor starter capacitor but nothing is written on it. There are 9 wires going in to the terminals, one is red, 2 are blue, one is brown, one is yellow and there are 4 black ones. I will try to find some kind of manual/ wiring diagram on line.

Do I connect the starter/ NVR switch direct to the mains? Which should be connected first?

David

Hi, Bazyle-the Axminster one you linked to has no overload protection-do I need this?

If I ever finish the mirror grinding machine I will write about it, thanks for all the advice. I have already made a very heavy duty grinding table from wood that I can barely move! The first thing I want to get working is a rotating turntable, then I will try adding the over arm to hold the grinding disc. Doing this by hand I have made this from concrete, poured in to a mold, with 2 pennies stuck to it. A lot of people use mosaic tiles.

Once I have made significant progress with the grinding I will write about it, about the techniques, I do not think these have changed that much in around 150 years! (At a guess). This will be in a few months, I am estimating somewhere between 6 months and a year to finish the mirror!

David

Hi, I have to laugh at myself sometimes!

I bought a single phase 1/2 hp 4 pole Clarke electric motor from Machine Mart as I thought that this would be much simpler than a 3 phase motor. I noticed that their website advised buying a '2-4 amp starter' as well. That's fine, I thought, I'll just plug that in to the mains, plug the motor in to the amp and away I go. Of course it turns out that the starter amp is a 'motor protective cicuit'-MKS1TM-K-40, which you have to wire (presumably to the mains) and I presume I will have to connect the motor to it somehow.

I have understood that this gives protection to the motor and stops it coming on again unexpectedly after a power failuire? So it is probably a good idea. The manual for the protective circuit says it should be fitted by a qualified electrician. As this would come to a lot more than the cost of the motor there is no chance of me doeing this!

How difficult/ potentially dangerous is it to do it myself? I have a multi meter and am pretty sure I can figure it out.

The instructions say 'first press stop' then connect 'YKD' There is also a 'thermic set up table' I at least know that I need to turn of the electricity at the mains first!

I guess from reading on this forum lots of lathes etc need something similar so I am guessing a lot of people who are not qualified electricians have fitted these.

Plan B is to use my pillar drill motor, which goes down to 210 rpm and I can just plug it to the wall. But I would quite like to keep using it as a pillar drill!

By the way, I am hoping that the Seig SX2 Plus i have ordered does just plug in to the wall!?

David

Thanks for all the advice. I have ordered the Sieg SX2 Plus from Arc. I went up to Leceister as I wanted to have a look at it to be sure I can fit it in my small flat. It should be fine. I would have like something bigger perhaps but have no room!

Ketan was very helpful and actually discouraged me from buying some things staight away, this must be pretty rare!

I got the R8 collets and a few other things. Now I need to order a chest for it to go on, probably from Halfords.

I won't be doing much with the mill for a while, as I need to concentrate on making progress on grinding my 20 inch telescope mirror, before I start making the telescope! When I get round to milling something I will post again.

David

The next thing is where to get a 'counter shaft' and timing belts? I presume I can connect the first smaller pulley directly to the shaft on the motor? i will need to wait until I have the washing machine pulley to see the size of the shaft I will need to fit the hole (bore?).

David

Hi, thanks for all the replies.

Ian, where did you buy the motors and inverter? The Machine Mart inverter costs £274! Although it does go up to 2 hp.

I would like to get a 1/2hp motor 4 pole electric motor, as then I should defintely have enough power. A 20 inch mirror is pretty heavy!

I would prefer something I could just plug in. The manual for the Machine Mart inverter states 'All models must be connected via a separate isolator, and must be protected by a fuse or circuit breaker,' I could probably figure this out. But single phase motors seem a lot simpler, as I presume I can just plug them in to the mains?

The only thing I am slightly worried about is starting the machine at 40 rpm staight away, but I don't see why this should be a problem, as the mirror will be secured to the turntable.

David

Hi, my hobby is making mirrors for telescopes.

I am planning on making a mirror grinding machine. A 3 phase motor plus inverter from Machine Mart would come to over £400, which is too much! So although it would give variable speed? (I am not sure of this?) I plan to get a single phase motor I can use without an inverter. Probably 1/2 hp or 3/4 hp. 4 pole.

I am planning to buy a washing machine pulley, around 14 inches in diameter. I can buy smaller pulleys from machine mart. The rpm of the motor will be 1500. I need my grinding table to rotate at around 40 rpm. How do I calculate the size of the second (and possibly third if necessary?) pulley and the length of belt to get the rpm reduced 40 rpm?

Also, can I just plug this kind of motor in to the mains or is there anything else I need to buy for it to work safely?

David