Hulett Ore Unloader in 1:32th

[Bernhard]

Thank you all for your interest.

Russ, the rest of the day I will spend with a few bikini beauties, drink beer and think a bit about how to proceed.

Hauk, I have worked in mechanical engineering for a long time and therefore know pretty well how such a machine should be built. Unfortunately, most hobby machines do not even come close to meeting this requirement, or they are far too expensive. I have therefore bought a self-built machine. It's not perfect in terms of craftsmanship, but it meets my mechanical requirements.

Bernhard

[Bernd]

Thanks for your hint, Bernd. In fact, I have been able to find the drawings by Mike Rabbit for some time. Apparently there has also been a CD with photos. Do you know where I can still get them?

Bernhard

Hi Bernhard,

I have no idea where you would be able to find the CD. I did not even know there was a CD available. Sorry.

I will be following this project closely. I'm fascinated by your machine work. I have two CNC machines, a Sherline and a ROBO router/engraver. I only work in HO (1:87) scale so these machines suffice for me.

Bernd

[Hauk]

Hauk, I have worked in mechanical engineering for a long time and therefore know pretty well how such a machine should be built. Unfortunately, most hobby machines do not even come close to meeting this requirement, or they are far too expensive. I have therefore bought a self-built machine. It's not perfect in terms of craftsmanship, but it meets my mechanical requirements.

But you are also using a manual Wabeco mill, right?

[Bernhard]

Bernd, show us more of your work!

Hauk, yes, I have been working with the Wabeco for some time and I am very satisfied with it. However, there are many parts in the current project that you can hardly make on a manual machine. That's why I decided to buy a CNC machine.

Bernhard

[Lawton Maner]

Can those with CNC machines please chime in on the +/- of theirs.  The field is moving so fast that some of the older ones are outdated.

[Bernhard]

That's not so easy to answer, Lawton. It always depends on what you want to do with the machine and what you are willing to invest.
But I can try to show you what makes a good CNC milling machine from my point of view.

Stability
The more unstable the machine, the more the tool vibrates. This shortens the tool life and the quality of the surface becomes poor.
In our area you can often find offers for self-built machines made of wood.  This does not work at all!

Stable guides
Preferably pre-stressed profiled guide ways. Everything else is not recommended, e.g. round guides that are not supported over the entire length, plain bearings or guides on rollers.

Drive of the axles
Recommendation: ball screw with preloaded nut. This has no backlash. A trapezoidal screw, on the other hand, always has some backlash.
Of course, the spindle must be correctly mounted (radial-axial bearing on the locating bearing side, radial bearing on the non-locating bearing side).
The worst thing I have seen in this regard: the spindle is mounted in two plastic plain bearings and fixed directly to the motor with a bushing. This is the perfect self-destruction mechanism for the motor. The machining forces act directly on the bearings of the motor, which are in no way designed for such loads.

Motor mounting
If possible, motors should be mounted directly on the spindle with a coupling. Belt drives worsen the positioning accuracy. Very bad are for example Y-axis drives with 2 spindles, one motor and one long drive belt.

Milling spindle
Preferably with water cooling for good heat dissipation. With air cooling you have to keep an eye on the temperature, because heat expansion of spindle and tool lead to errors in Z-direction.

Modular control
Separate power stages for all axes simplify troubleshooting and repair.

And finally, of course, all axes must be precisely aligned, then it will work.

Bernhard

[Bernhard]

The rear casing of the angular gear is made from a piece of pipe.



The recess for the bevel gear bearing is milled out.



The cover is made on the CNC milling machine.



Then the parts are soldered together.

   

[Bernhard]

The bearing for the bevel gear is mounted and four more parts are ready.

[Bernhard]

The front casing is actually made of sheet metal. But it is relatively difficult to bend it to fit exactly, so I make it out of solid material.
First, a brass block is roughly hollowed out.



Then the inner contour is milled on the CNC machine. To prevent the part from being deformed in the vice, I leave 0.8 mm of wall thickness. This is very oversized, but you won't see it on the finished part.



For the re-milling of the outer contour I first have to build a small clamping device.


   

[Bernhard]

The inner wall is milled out of 0.3 mm sheet metal.



Finally, the brackets are soldered on with the resistance soldering device.



The finished parts:

   

[Bernhard]

Now I have to get into series production: I have to turn 36 steel wheels. Repetitive tasks have never been my thing, but I have to get through them.
First one side is faced, then the running groove is cut.



Since I can't cut such parts on my lathe, I cut them off the bar with the circular saw.



After 12 hours of work, 36 pre-machined wheels are ready for the next operations.



But how can the wheels be clamped for further processing? This is not possible with the normal three-jaw chuck.
I therefore have to make special additional jaws first.

   

[Bernhard]

I turn three rings that can be put on the jaws of the three-jaw chuck without any clearance.
They are pre-machined from behind on the milling machine.



The rings are put on the chuck, clamped against a disc and secured with stud bolts.
Now the face can be turned over first.



Then the clamping diameter is turned out.



With this I can clamp the wheels on the running surfaces, then face the second surface and make the axle hole. Clamping on the running surface ensures that the axle bore runs exactly round.

   

[Bernhard]

Now the circumferential groove is milled on both sides with a torus cutter. The cutter has a diameter of 5 mm and an edge radius of 1 mm.



Since I want to conduct electricity to the model via the rails, all wheels still have to be provided with an insulating sleeve made of plastic.



Normally I don't count my working hours, because it's all just a hobby. But here I made an exception: for the production of 36 wheels I spent about 42 hours.

Bernhard 

[finescalerr]

Well, that was quick, simple, and easy. What's next? -- Russ

[Barney]

AH Gasp  -Just took the tablets and a dose of Oxygen Was going to come out from under my Rock - But second thoughts I stay here
Barney