Spindle design? ever been tried?

[Kipper]

I was in inquisitive mood today and was experimenting after noting the speeds of modern spindles. So i'm on holiday at the moment so was tidying up "the shed" i've been looking into high speed spindles for a short while and looked through the stuff I had laying around and I present you with my findings on the crap...ahem good stuff I found laying around I found a turbocharger impeller and housing and wondered if a vacuum cleaner could "reverse power" a spindle...Anyone ever tried this? My findings are that I cannot measure the speed of the spindle (my tach craps out "mt139a by snap-on" @ 30.000rpm) however it sounds really nice (read high pitched whine...turbo style. My judgement on this leads me to think it may work for engraving use! reason being it is major high speed and only requires a "shop" vacuum cleaner! (Henry in my case and he's an old chap nowadays) I first tried it by the method "I thought would work" and I was wrong :shrug: I thought to draw the air through the outlet of the the turbo! and it only made 20.000 rpm....However when I drew it through the inlet side it made the bearings I had work overtime!! It blew the mind of my tacho too lol is this a new application or is there an existing product out there? I was thinking it could power the spindle...And collect dust/crap from the cutting area (if it didnt abrade the turbine too much . Any thoughts are welcome and if indeed it is a new application i'd wish it to be open source for all for free.

[aggie_67]

Don't the bearings on a turbine require pressurized oil feed??

[vladdy]

You don't need a great deal of oil pressure, but at least 10 psi so it will live for awhile...

sucking debris through a turbo spinning at 20k+ will shorten it's life expectancy quite drastically, and also someone standing close to it at the time, yep, I saw that once up close, and once was one too many...

Try using air pressure instead of vacumn, you may be pleasantly surprised..

enjoy..

[Kipper]

If you've seen turbo's before you'll notice that this one has no centre section where the oil supply goes...This one has a temporary bearing block which had some bearings from an old shop vac motor thrown into it. I'm going to modify this further to see what happens when it sucks dust up at whatever silly rpm it gets up to :evil: I doubt it will expire...maybe it'll polish itself a little lol...then if it works i'll have a go with "Big Daddy"

[vladdy]

Hmm.. it actually might work, probably won't get the accuracy of a 'normal' spindle, but for wood engraving or similar it may be 'good enough'. A couple of bearings in the middle still leaves a fair bit of shaft hanging out both ends, or were you thinking of trimming off one side and adapting a collet to the part still attached ??
Very fine dust will probably pass through with little short term damage, however a bigger 'chunk' if it gets wedged between the vanes will probably cause a fairly noticable 'off balance' situation..
I have seen a few where even a piece of carbon coming loose will damage the exhaust side vanes quite badly, sometimes even breaking off most of them,
still worth a try, looks like you have it half done already...

enjoy..

[Kipper]

It's free so i'm just playing with it vladdy. The inlet will be meshed to stop big chunks going in and I was hoping to use it only for MDF at small bit sizes 1.5mm (some big number in old money :shrug and very high speed... When I find some better odds and ends it'll get a sturdier assembly with a collet on and if I dont post back then it was a bad idea It's on the back burner till I get the mill converted over anyhow....Oh and theres a few doors to paint too :lol:

[NC Cams]

How do you plan to deal with the following:

1. radial clearance in the sleeve bearing. Spindle bearings are traditionally preloaded to remove radial/axial clearance for as to maintain running accuracies.

2. Axial clearance in the sleeve bearing - ditto reason above.

3. Radial and axial clearance also drastically reduce radial and axial stiffness in the spindle. Although you may have speed, you surely won't have running accuracy.

For the above reasons alone, I'd be highly disinclined to 'play' with a turbocharger as a machine tool spindle candidate.

BTW, most of the turbo's that I've seen run at the same oil gallery pressures that the rods and mains run at which is multiples of the 10 psi suggested previously. More like 30psi min and as much as 60 psi under full speed/WOT use.

[Kipper]

1&2 could be taken care of by traditional preloading thereby rendering point 3 null. point 4 being you wouldnt play with it...well then dont As for the btw I havent yet seen an engine that gives out more oil pressure due to the TPS ...more like it is in relation to the speed the oil pump spins at :shrug: Thats if I interpreted the WOT as "Wide Open Throttle"

[motomitch1]

Turbo Spindle & hand grinders have been around for years so it will work.

http://www.emazing.com.au/tools/airturbine.htm

[NC Cams]

Kipper: as I have been an engineer involved in the designd and applications engineering for both ball and sleeve bearings, please, Please PLEASE tell me how to "preload a sleeve bearing"??????? Especially when sleeve bearings are NOTORIOUSLY INTOLERANT of metal-to-metal contact..(BTW:most turbos are sleeve bearing equipped because ball bearings have a hard time tolerating the speeds and temps of a turbo) ..

Motomitch: Yes, they have. But the ones you refer to were DESIGNED for that type of use in mind. This application is an automotive turbine housing used in a turbocharged application. The ONLY axail and radial thrusts it was designed to absorb/withstand are due to those generated by gas pressures - not the cutter reaction loads generated by machining.

Regarding oil pressure: idle pressure is one thing, off idle, cruise and WOT (wide open throttle) are totally different.

My 350 chevy idles at 20-25psi but pops up to 60psi as soon as you get over idle. My turbo Mustang back in the 80's saw a minimul of 40 psi and went higher when hot and at higher speeds.

Essentailly, the oil pressure that engine reaches is a function of the pump capacity, the speed of the pump/engine, oil viscosity and the loss factor due to clearances in the engine. The TPS signal is absolutely irrelevant to relief valve modulated, mechanical oil pressure pumps.

[vladdy]

Took a look at an old turbo [off a tractor] in the garage, and your idea should work for mdf and such, lighter cuts on relatively soft material...If you lop off the exhaust side and make some kind of a spacer to get two bearings a little further apart it will help accuracy..
the screen in the inlet side is definitely a good idea...
It's not going to be really tight and accurate, but then the cost reflects that as well...
Do you have any idea of how you are going to adapt a collet on the end??

enjoy..

[lwill]

Could you do the same thing with just vacuum cleaners?
Aside from all the bearing issues, why not take a smaller vacuum cleaner, like a small 1 gal. shop vac with a 1" hose, gut the motor, and drive the impeller using a larger shop vac? Would the increase in air volume increase the smaller ones speed? Would the low tolerances and higher clearaces in the vacuum (compaired to the turbo) even work? Some cheap house hold vacs suck through the impeller (the clattering sound I hear when I clean up around the litter box!), if it would work you would not have to worry as much about the dust going through it. Of course it would not be very heavy duty, but could make a cheap (and self cleaning) spindle for a small diy engraver. With some upgraded bearings it might not be much worse than a dremel.
I have some dead ones around the shop and might give it a test if I have time to dig though my junk.