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Old May 10, 2010, 07:11 AM
Charged up and buzzing
vampire67's Avatar
Germany
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Quote:
Originally Posted by mlmcquiggjr View Post
The collet shaft is 8mm. The motor shaft 8mm.
That was the beauty of the proposal I immediately fell for.

I have seen the ideas to use collet holders and BLDC before.
Mostly the holder had much larger shaft diameter and needed some linking to the motor the complicated the whole thing. Worst case some gearing was required.

But this is realy my style.
Lean and mean and no part with questionable added value

The availability of these cheap HK motors with 8mm shaft makes everthing much simpler and cheaper.
The only other smaller motors that I found with 8mm shaft are Scorpion 402x. Whould cost about twice as much but would be good for 1..2kW.

Quote:
Originally Posted by mlmcquiggjr View Post
How about cutting down a pusher prop and ditching the shroud idea.
I think it doesn't matter if push or pull.
The shroud is needed for guiding the airflow were it's needed most.

The added protection is a nice plus too.
I wouldn't like to have a spinning prop in front of my nose when I'm nosing around a running cut process
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Old May 12, 2010, 04:56 AM
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michaelghammer's Avatar
Denmark
Joined Dec 2004
559 Posts
Quote:
That was the beauty of the proposal I immediately fell for.

I have seen the ideas to use collet holders and BLDC before.
Mostly the holder had much larger shaft diameter and needed some linking to the motor the complicated the whole thing. Worst case some gearing was required.

But this is realy my style.
Lean and mean and no part with questionable added value
You could make it even leaner and meaner: remove the 8mm shaft from the Turnigy motor and replace it with the collet chuck shaft. Mount the motor in a firewall attached to the z-axis. And there you have it: Bob´s your Uncle

You could refine this design a bit by cutting the shaft down to length so it doesn´t protrudes out the back of the motor. If you replace the stock bearings of the Turnigy with ceramic bearings you would have an inexpensive and compact spindle.


This weekend I tried adding a shroud to my spindle. I cut the prop down further to the same diameter as the motor (50mm) and CNC cut two blocks of blue foam to create a 50mm duct. The idea was to force all the cooling air through the motor and past the windings.

The result wasn´t very good. I had problems with the balancing of the prop and this resulted in vibrations. The duct worked fine, but the bell of the motor wasn´t cooled enough from the inside and got hot. So I ditched it all for now and cut some plywood firewalls with the original spindle setup... mustn´t forget to build model planes

I will give the cooling idea one more try with a 70mm duct and a 70mm prop...

- Michael Hammer
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Old May 12, 2010, 07:51 AM
Slipping the Surly Bonds
dz1sfb's Avatar
Attica, MI
Joined Dec 2006
10,495 Posts
Michael,

Why not install a dust collection system with a small shop vac. This could move some air past the motor and collect up the nasty dust. I don't remember who said it, but dispersing the dust around the room is a very, very unhealthy idea.

Ken
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Old May 12, 2010, 08:00 AM
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michaelghammer's Avatar
Denmark
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559 Posts
A dust collecting system is on the wish list. But to be effective it would have to collect the dust when it exit the cutter. I don´t want it to be sucked through the motor.

I made a fuselage from blue foam that was made in two steps. First the inside was hollowed out and then the outside was made. I tell you, that electric charged blue foam dust almost drove me insane. It was everywhere and sticking to everything. That taught me the need for a dust collecting system...

- Michael Hammer
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Old May 12, 2010, 10:09 AM
There's Something in the Air
Ne-Aero's Avatar
United States, NH, Hillsborough
Joined Jul 2005
265 Posts
Have you considered using a commercial Fan unit like this one instead of cutting down a propeller and building your own shroud?

John
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Old May 12, 2010, 10:27 AM
Charged up and buzzing
vampire67's Avatar
Germany
Joined Aug 2005
531 Posts
Quote:
Originally Posted by michaelghammer View Post
You could make it even leaner and meaner: remove the 8mm shaft from the Turnigy motor and replace it with the collet chuck shaft. Mount the motor in a firewall attached to the z-axis. And there you have it: Bob´s your Uncle
I wouldn't actually recommend this.
The motor dome is rather weak and would not stand much chances of surviving the vibration happening during a serious cut session.
A club mate had the motor dome collapsing at his TRex 600 during flight with quite dire effects.
I think the bearing block for serious milling should be a little more solid than that.

Additional idea:
I will try to mont the motor with elastic mounts on the bearing holder.
This way the alignment of the bearings should be better and we don't get excessive tension in the bearings by misalignment.
That should help improve bearing life.
I think little rubber mounts for IC engine should help here.

regards Peter

P.S. just found out the holder schould be 43mm, not 44mm ...

P.P.S.
Quote:
Originally Posted by dz1sfb View Post
I don't remember who said it, but dispersing the dust around the room is a very, very unhealthy idea.
You seemed to have missed this tag:
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Old May 17, 2010, 07:29 AM
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darook's Avatar
Johannesburg, South Africa
Joined Apr 2006
471 Posts
HI. Where can I find info on how your brushless motor is set up and how you power it and control its speed?
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Old May 17, 2010, 07:45 AM
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michaelghammer's Avatar
Denmark
Joined Dec 2004
559 Posts
darook,

I´ll post some more pictures tomorrow. But basically you need an Electronic Speed Controller or ESC, a servo tester and a power supply.

ESC: http://www.hobbycity.com/hobbycity/s...idProduct=7339

Servo tester: http://www.hobbycity.com/hobbycity/s...idProduct=8296

The ESC I bought was not the best choice because it doesn´t supply the servo tester with power through bec. So I had to feed the servo tester with 5V from the power supply. If you buy this one: http://www.hobbycity.com/hobbycity/s...ies_35-40A_ESC You just have to plug it directly to the motor and the servo tester.

Vampire67,

The idea about mounting the motor on rubber "feet" sounds like a good one. I think it´s time to get the tools out


- Michael Hammer
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Old May 17, 2010, 08:12 AM
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darook's Avatar
Johannesburg, South Africa
Joined Apr 2006
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Thanks Mr Hammer! I have subscribed and am watching with interest!

The reviews on those two ESC's were not good at all, lots of burnouts and problems etc.
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Old May 18, 2010, 02:44 AM
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Denmark
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As promised, some pictures of the spindle, ESC and servo tester.

You can see the servo tester is connected with 5V from the power supply (in). The ESC is connected to the out port of the servo tester. If the ESC was equipped with BEC you wouldn´t need the power in.

The ESC has worked very well and I´m quite happy with it. At $14 it´s great value for the money.

All the electronics are mounted in a wooden box. You can probably tell that electronics are NOT my "forte´" but things work and when I close the lid no one will know

The driver board is situated in the far end underneath the "Ensalada Electronica". I havn´t cut all the wires to correct length, because I´m planning to move to a new house and the box will probably need to be further away from the machine. The three stacked power supplies are coupled in parallel and supply the driver board with 25V. The last power supply is for the spindle. 25V for the motor and 5V for the servo tester. All power supplies are from "old" thermo printers and are designed to power one Nema 23 stepper + thermo element.

A big 120mm fan sucks air from the box and a smaller fan helps in the other end. Both fans run on 5V instead of 12V which lowers the noise level a lot.

- Michael Hammer
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Old May 18, 2010, 07:39 PM
Friend is a 4 letter word...
JussiH's Avatar
3rd stone from the sun
Joined May 2007
2,670 Posts
Michael - godt gået. Overvejer nu stærkt at bygge dit design i stedet for at købe MDL2 eller lignende.

Thanks for sharing! Excellent work!

Jussi
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Old May 19, 2010, 09:04 AM
Charged up and buzzing
vampire67's Avatar
Germany
Joined Aug 2005
531 Posts
Quote:
Originally Posted by michaelghammer View Post
All the electronics are mounted in a wooden box. You can probably tell that electronics are NOT my "forte´" but things work and when I close the lid no one will know
The only thing that frightens me is your creative way of wiring the mains lines to the power boards.
Kids, don't try this at home, these are professional stuntmen at work

Take care, man, we need you for more scratch designs

EDIT
Or are these notorious 110VAC ?
I know guys that use more Volt in their planes

But denmark sounds more like 230VAC ...
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Old May 26, 2010, 03:25 AM
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Old May 26, 2010, 03:57 AM
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Denmark
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Thanks Jussi, good luck with your future CNC router...

vampire67, obviously we use 230V in Denmark And 380V as well. So we´re well prepared for the introduction of electric cars... Can´t wait to get my hands on a Nissan Leaf

Quote:
The only thing that frightens me is your creative way of wiring the mains lines to the power boards.
Kids, don't try this at home, these are professional stuntmen at work
I know it´s not pretty. But all connections are soldered and the powersupplies have fuses. And I usually hang around the machine when it´s working.

The spindle have been doing quite a bit of cutting since the last post and I´m very happy with it. So tweaking has been postponed a bit... I need to get my daughters CL-415 flying boat finished instead...

I want to share a few pictures about my approach to fixing stuff to the work surface. The work surface is 10mm MDF which acts as a spoiler board. The MDF board has an array of holes in it, made with the router of course. In to these holes I can insert little brass "thingies". The "thingies" are normally used to hold shelves in closets, two on each side. I bought mine in the local DIY hardware store.

I put these thingies on two sides of the wood that I want to cut. On the other two sides I also place the thingies, but with a distance to the wood. Pairs of wedges are inserted between the thingies and the wood.





- Michael Hammer
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Old May 26, 2010, 04:01 AM
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Denmark
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Pictures:




- Michael Hammer
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Last edited by michaelghammer; May 26, 2010 at 04:22 AM.
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