mirror o matic

[Demonperformer]

I am giving some (possibly) serious thought to making one of these [http://www.mirror-o-matic.com/demo.pdf], but all my internet searches for a 1/4hp 1725rpm motor produce nothing but a ton of stuff from america on ebay (even when I ask it to give me UK stuff only) plus a few items from UK companies for three figure sums. Am I being totally unrealistic in expecting to be able to find something cheaper in the UK? Has anyone on here built one of these? Did you find a good source for the motor?

Thanks.

[Gina]

I'm afraid the link isn't working.

[Demonperformer]

Sorry about that, Gina. Put the bracket as part of the address instead of outside ... corrected and think it works now.

Thanks

[skybadger]

Hi Demon performer

I made one of these, or more accurately, finished off another chaps. The motor just needs to be what you have available, In the UK its typically a 1/4HP 1425 RPM that you can buy new for £60 or so or buy secondhand for £20 or so. There are three opportunities to change the output gearing, on the output drive of the powrhead, from an intermediary pulley or from the oscillator pulley.

I have pictures of mine on the website.

Hope this helps

Mike

[skybadger]

One of these...

0.25KW (0.33HP) SINGLE PHASE 4 POLE (1500RPM)

will do.

I susopect that if youwant to drop it straight into the dimensions you will need to check the frame size matches.

One other recommendation is to go for a fixed pulley ratio on teh mirror platter and use a motor speed conrtoller to adjust to desired. Then use a set of pulleys on the oscillator to give you a oscillator speed to suit the platter.

Have you noticfed the worksheet in the back of the MOM for motors, pulleys and effective RPM ?

Cheers

Mike

[Gina]

That looks very interesting. Should certainly cut out a lot of hard work but the one in the PDF looks rather complicated. Probably nothing like building an observatory though

[Gina]

One of these...

0.25KW (0.33HP) SINGLE PHASE 4 POLE (1500RPM)

will do.

I susopect that if youwant to drop it straight into the dimensions you will need to check the frame size matches.

One other recommendation is to go for a fixed pulley ratio on teh mirror platter and use a motor speed conrtoller to adjust to desired. Then use a set of pulleys on the oscillator to give you a oscillator speed to suit the platter.

Have you noticfed the worksheet in the back of the MOM for motors, pulleys and effective RPM ?

Cheers

Mike

That looks like a shaded pole motor to me or even synchronous in view of the speed. So the only way to control the speed is to alter the supply frequency. That would require a high power inverter.

EDIT... Yes, it's a capacitor start synchronous motor. A 50Hz supply with a 4 pole motor gives 1500 RPM

[pete_l]

You might even get away with using a (woodworking) router. Though they tend to have faster RPMs than the one specified. On the upside, even cheap ones have electronic speed control, so you could simplify the design by doing away with a lot of the pulleys and just dial up the speed you want on the router's control.

A ½-inch, 1200Watt router can be had from about £40 new.

[Gina]

I didn't realise they were that cheap!

But yes, a commutator motor is what's wanted.

[Demonperformer]

Thanks, guys, that gives me something to think about

[skybadger]

Aye, I wouldn't necessarily be wanting a shaded pole motor for this - the speed controller is a definite bonus from looking at the MoM group on Yahoo.

Also if you want to go to larger mirrors, mine tops out at about 16" without a rebuild due to the powerhead layout and you will also need a larger motor to handle the larger loads at that point.

cheers

Mike

[Demonperformer]

You might even get away with using a (woodworking) router.

So using something like this might be suitable as a power supply? Vastly faster rotation rate (11k-31k) but presumably that could be dealt with by using appropriately sized gears?

@skybadger - do you have a link to the MoM group?

Thanks

[JamesF]

Try:

Mirror-O-Matic : This list is for discussion about the "Mirror-o-Matic" telescope mirror grinding machine, as developed by Dennis Rech.

James

[Demonperformer]

Try:

Mirror-O-Matic : This list is for discussion about the "Mirror-o-Matic" telescope mirror grinding machine, as developed by Dennis Rech.

James

Thanks James

[Gina]

I guess the power required depends on how big a mirror you want to grind. That router from ScrewFix looks OK for small mirrors even if it generally gets the thumbs down as a router. Seems the motor unit is fine - it's the fittings that let it down.

I guess it would also depend on how much pressure is used, so a lower power motor could be used at a lower pressure and take longer.

[Demonperformer]

Try:

Mirror-O-Matic : This list is for discussion about the "Mirror-o-Matic" telescope mirror grinding machine, as developed by Dennis Rech.

James

It seems that a long time ago I registered with Yahoo. I can't remember doing so, but worked it out when I tried to use my DP username and it said it was not available and it liked one of my (previously) favourite passwords. So now I am waiting for Yahoo to reactivate my account before I can access all that yummy information. Watch this space.

[JamesF]

It seems that a long time ago I registered with Yahoo. I can't remember doing so, but worked it out when I tried to use my DP username and it said it was not available and it liked one of my (previously) favourite passwords. So now I am waiting for Yahoo to reactivate my account before I can access all that yummy information. Watch this space.

I use (literally) hundreds of passwords for all sorts of services relating to client work. I prefer other authentication methods where possible, but that often isn't an option. Obviously it wouldn't be a very good thing to reuse passwords relating to one client's services for another either.

For that reason I use an application called "revelation" for tracking all my passwords, which it can generate randomly and store in an encrypted file protected by a passphrase. Depending on your operating system of choice, you may find something similar that works for you.

I like it because it means I never use the same password twice, they're strong passwords (ie. hard to guess or crack) and I don't have to remember them. It is a good idea to back up the encrypted file on a regular basis though

James

[Gina]

I've joined the MOM group Not that I'm planning on mirror making just yet but I like to take a long run in Get my head round all the aspects of the job and assimilate plenty of good advice from the experts. I have no doubt I will be mirror making in time, I've often thought I'd like to make my own scope. I made the odd rather half-hearted attempt when I was young but now I'm well into astronomy with a vengeance I just need to collect up the funds and find the time. Trouble with me is that I keep collecting new projects Great fun though

[ponytale]

I have looked at this idea a few times and wondered about a washing machine motor

and some of the controls it seems they run from slow wash cycles can oscillate back and forth and can spin from 400- 1200rpm via control panels .

they can be had for free on freecycle etc , any thoughts/comments would be appreciated ,Tony

[Demonperformer]

Found this and had to make a quick decision as it was ending in about 5 mins. My only concern is that it has a second spindle, but presumably that could always be removed with a hack saw if nothing else. £25 and within pickup distance was too good a chance to miss.

Build starts here ...