Fingers crossed it'll cut ally

[routercnc]

Quickly sketched this to show aircraft vs cnc application for those interested:

(You could probably delete the 4.8V supply if using a BEC ESC)

[blackburn mark]

nice one... im not so good with the electronics but all this stuff is nice and modular,, for those that dont know BEC is just a set of 5v power leads coming out of your Electronic speed controller to run your servo tester

anyone using small motors (engraving) might get away with an old PC power supply... they have 5v and 12v coming out of them

[Jonathan]

anyone using small motors (engraving) might get away with an old PC power supply... they have 5v and 12v coming out of them

If you're careful you could even put the computer PSUs in series. Just need to make sure they're isolated. I considered doing this for my stepper motors since I've got plenty of 350W (or so) PSUs from the local car boot and if I put 6 in series that would have given a nice 72v for my stepper motors. I decided against this as 6 of those would have been a bit bulky and a good toroidal transformer came up on eBay.

A cheap way of providing the 5v supply is just using a 5v voltage regulator. Any would probably suffice since it's only providing a few miliamps in this application.

With regards to my big motor I think I could get away with the 100mm shaft collet holders. I'd probably get the 1/2" one and reduce it down to 12mm. The motor contains 4 bearings, 3 of which are 2112 bearings and one big 6089. I shouldn't be too difficult to change them but it is worth it? The biggest external diameter bearing that would fit without doing something imaginative is maybe 24mm. I can't find any angular contact bearings that would fit there.
I've been thinking of using this motor for a 4th axis / lathe but I wont go too off topic!

[blackburn mark]

yo jonathan,

i was terrified of turning down an over sized shaft so i spent weeks looking for the right size, its being shipped as we speak

im gutted you didnt find a 150mm one, im convinced it would have been easy to stick double row A/C on the nose in a shallow housing,, ill find out as soon as my shaft turns up ill start doing a bit of turning

im not totaly convinced a double row A/C bearing will be tight enough for ally, the ones iv got dont feel like they have that much pre-load, i might end up stacking the two of them

4th axis... mmmm im thinking a 100mm rotary table with my 5th stepper melded to it

im not sure anything is off topic,, is it?

[Jonathan]

i was terrified of turning down an over sized shaft so i spent weeks looking for the right size, its being shipped as we speak

Hah, I was pretty scared dismantling this motor. It was all glued/loctited together and needed some persuasion with a hammer.

im gutted you didnt find a 150mm one, im convinced it would have been easy to stick double row A/C on the nose in a shallow housing,, ill find out as soon as my shaft turns up ill start doing a bit of turning

There are 150mm ones, but they're more than twice the price of the 100mm. I could probably extend the 100mm one if it came to it - definitely some thinking to do before I buy anything!

im not totaly convinced a double row A/C bearing will be tight enough for ally, the ones iv got dont feel like they have that much pre-load, i might end up stacking the two of them

I see, so you don't think the ones that are currently in my motor would be up to it? Maybe I could link this motor to the existing milling machine spindle via a pulley...then I needn't worry about angular contact bearings. Having said that I don't know if the bearings in the spindle of my machine are up to 6000rpm.

4th axis... mmmm im thinking a 100mm rotary table with my 5th stepper melded to it

Yep, that's what I did except with a 150mm vertex rotary table. It's excellent for making pulleys:



And making 4th axis'

im not sure anything is off topic,, is it?

:) well in that case this is the 4th axis/lathe design I've started making:





I'm using two tapered roller bearings in that. The gold things are solenoids to create a sort of disk brake which I'm hoping will hold it steady enough for me to mill will it aswell as using it as a lathe by swapping to a bigger motor...the brushless one.

[z3t4]

Quickly sketched this ...

Thanks for the explanation. It's good to have it presented so clearly.

[blackburn mark]

iv got some 8mm id A/C bearings but they are open (as apposed to sealed) so for now ill stick with the skate bearings
it would be nice to seal the nose and have a nice light oil swishing around in there :)

still a bit of work to do on this but it will give those that are interested an idea of what we have been on about

[blackburn mark]

My ER11 10mm shaft turned up,, nice tight fit.. i may loctite it when im happy

Iv decided on one double row A/C bearing for now... i left room in the housing for two just in case :)

i ran it no load for ten mins... the bearing gives off more heat than the motor but nothing to drastic, if i remember correctly up tp 110 degrees is passable... it was nowhere near that

I tried to keep the housings 43mm but it wasnt really pactical
i havnt fully decided on how to setup the small motor, iv considered inserting an engraving bit straight throgh the motor but im struggling to find engraving bits with enough length to allow for more bearings on the nose... i may modifiy a needle vise....
anyway the engraving motor is not overly inportant to me but Its killing time while i wait for parts for the main build

just got to hope they will work as well as they look :)

[irving2008]

Yes please!

There was an article in MEW (Feb 2008 issue, No 135 ) about making outrunner motors but there wasn't much about how to power them. I'm guessing that the 'servo tester' provides a PWM pulsetrain and the speed controller (is this aka an 'ESC'?) sees the pulsetrain and uses electromagick to provide a 3-phase supply to the motor.

John

Quickly sketched this to show aircraft vs cnc application for those interested:

(You could probably delete the 4.8V supply if using a BEC ESC)

1/ Whats the PWM signal characteristics?

2/ 'Servo Tester' sounds an expensive beast

3/ Surely you'd want a 0-10v input so you could control spindle speed from MACH3?

[blackburn mark]

Cheers George.... i had my fingers crossed... but no joy. the motor body is 30mm i could do with at least 15mm to play with for a housing and bearings,,, those you linked are 38mm and a good bit of that length is taken with the knife,, nice try though xx

irving... the servo testers are between a fiver n tenner ebay... the rest of what you ask is errr... rocket science..
i have read somwhere that the puls rate is way to high for mach3 and would need some kind of conversion

im sure a man like you could rustle one up in your dinner break :)