Diy Brushless Spindle

[Jonathan]

[QUOTE=njhussey;30976
How does the motor work with a prop on it in a plane then? There is a circlip to stop the shaft pulling out if the motor is used as a pusher or reverse mounted but nothing to stop it being pulled out apart from the bearings and the grub screw as you say. This seems to be enough for a model so I'd have thought it would have been enough?[/QUOTE]

On a plane the magnitude axial force (thrust) from the motor is much smaller than in our application, plus accuracy (end-float, radial clearance etc) is pretty much irrelevant for just spinning a propeller. The bearings will wear out much faster than if they used angular contact beraings, but the cost isn't justified. If sufficient axial force is applied to a deep groove bearing the balls will ride up the sides of the rings outside of the superfinished races on to the rougher (relatively speaking) area of the ring, causing increased wear.

I'll reply to the rest when you've done a drawing...

[blackburn mark]

i personaly wouldnt get to bogged down in all the rocket science... make sure you get some tension in your balls and make sure your shaft cant easily rotate in the bearing bore (loctight the nose bearing if its a tad slack) and all should be fine

any slack will result in balls skidding or a sypathetic rolling rotation/vibration between your shaft and your bearing bores
(a very short life span for either and poor finishes)
iv used super cheap skate bearing on my er11 with aprox 2kg of tension between the two and its still going strong
if you get any high pitched squeals/squeaks etc when the spindle runs up or down you need to fettle

the beauty of these spindle is they are cheap n simple
iv seen threads on diy spindles that are works of art and that have followed the theory to the letter, however, i get good finishes in acetal and alli so seen no point in getting all posh if the aim of the game is to get yourself up and cutting :)

PS: your bellville washers are bagged n ready neil, i just need to get off my arse and post them :(

[blackburn mark]

I would also load the angular contact bearing in the same orientation (both loaded with "upward" force). This would make the bearings strong in plunge operations, but weaker in operations where the bit is moving up out of the work piece. Would this be a problem though? Most operations are pressing into (down) the work piece.

on most occasions your tool would be pulling down as you are cutting but as i have said above, get some tension in those balls and and loctight your nose bearing and you should be fine

bearing heat may be an issue if your running above 10000rpm (keep an eye on the temp though as it may take a while for your bearings to settle in) if your cutting plastics and pcb's and your not in a crazy arsed rush then 10000rpm is a tad fast... i cut acetal at between 2000rpm and 4000rpm (6mm 3mm tooling) im sure i read somewhere that anything up to 110 degree C and your ok .... mine dont get anything like that hot

the small engraving spindle i made gets pretty hot when i run it above 30000rpm so i tend to run it closer to 20000rpm , i dont run that one very often so its hard to say how long the bearings will last?

[njhussey]

I'll reply to the rest when you've done a drawing...

Well I've had a look at the design and tewaked it a bit. Will probably do a MK2 spindle using this method or I might tweak this one I've already machined. this one is only really going to be cutting up to 6mm balsa and 3mm ply so I can't imagine the forces as being huge. I might stretch to some delrin/acetal and even try some Ali for a laugh



This shows the top collet (but I haven't bothered showing the grub screws) on the 8mm shaft which is pre-loading theinner races against the bottom collet. I'm guessing I could get away with not securing the bottom collet (locktite) as it will be trapped between the bottom bearing inner housing and the ER16 collet.



This shows the assembled unit (minus the bolts but we all know what they look like!!)



The bearings in the above are not spaced the correct distance, they will be a further 10mm apart so I can get some Bellville washers in between.

This design has the inner races locked to the 8mm shaft and the outer races are constrained by the endcaps...............comments?

[njhussey]

PS: your bellville washers are bagged n ready neil, i just need to get off my arse and post them :(

Cheers Mark, no huge rush as I've still got lots to do on the router (everything apart from the base!!) which I'm hoping to break the back of over the weekend.

[Villacherman]

Neil,

I like the design. Is there enough wall thickness of the collar (8mm ID X 10mm OD) to accommodate a small screw?

What about a collar that has a thicker wall and a little standoff, like this... gives you more meat to tap into.



This could also allow for a more tortured path on the bottom collar to keep dust out.

My last comment is to not forget to think about how you will assemble this... go through the steps in your mind, sometimes I design something and find out I can't assemble it because there are inaccessible features! :(

Adam

[Villacherman]

I just figured out grub screws are 4-40 set screws... I'm learning everyday!

Neil, was the shaft of the motor hard to swap out for the collet shank? Anything I should not do? I want to give it a try this weekend. I'll do all the usual, keep things straight and support, remove the circlip, etc...

[njhussey]

I just figured out grub screws are 4-40 set screws... I'm learning everyday!

I'd be using 2 off M2 x 3 grub screws and locktite in each collar (will prob make it 3mm thick for extra purchase of the grub screws) as per the attached photo.

Neil, was the shaft of the motor hard to swap out for the collet shank? Anything I should not do? I want to give it a try this weekend. I'll do all the usual, keep things straight and support, remove the circlip, etc...

I removed the circlip and pulled the bell off the motor complete with the shaft. Then put the bell on the vice so the shaft was between the jaws but the bell resting on top (obviously with a cloth on the jaws to stop marks) and using a 6mm piece of steel I had lying around gently tapped the shaft out of the bell (obviously remove the retaining grub screw first!!) slid out fine!

I've not put the collet shank in the housing properly yet (although I did fit it slightly on to see how it spum ) as I'm waiting to make the bearing housing first. Been far too busy at work this week to do any machining in my lunch but hoping to get it done next week. This weekend I'll be making my router gantry sides and trying to get that sorted although I keep changing my mind on how to do it!!

[rnr107]

Hi blackburn mark,
Looks very interesting concept! :-)
I just have 1 question so, How do you get the original shaft out of the motor?
Is it fitted with an interference fit to the bearings?

Ta,
RNR

[Villacherman]

Rnr107,

I just removed the shaft yesterday on my Turnigy G110 outrunner motor, so this is specific to my motor, others will vary...

1) remove the 4 M3 screws from the propeller mount.
2) remove the e-clip (circlip, retaining clip, however you want to call it) from the side of the motor with the shaft sticking out.
3) pull the shaft out by hand (I've heard you may need more force on other motors)

That's it! I really like the G110 for its simplicity in this manner, though it is a little pricier.

Adam