Elliptical path on wheel rim?

[John Hill]

How do I machine an elliptical groove in the rim of a wheel?  I dont even know if elliptical is the right word but I want to machine a groove in the rim of a wheel so that I can get movement parallel to the wheel's  axis,  sort of like the action of a swash plate.

Thanks

John

[Bluechip]

What? Barrel Cam ??

Similar to pic ?

Dunno, John. Tried to do it myself a couple of years ago with a uController, 2 steppers , one on a rotary table and t'other on the x-axis but although the principle is, I believe, sound my attempt was not too good.

Did work but the set up needed much more refining and was abandoned.

Dave

[John Hill]

Yes Bluechip, something like that!

[Fergus OMore]

Maybe Ornamental Turning is what you are looking for. Elliptical chucks?

There's a Society in the UK. Maybe- Charles Holzapffel and Ornamental Turning. Tubal Cain did a book on the topic as well.

Regards

Norman

 

[JohnC]

If you put the wheel on a faceplate and packed up one side you could use a parting tool to cut a groove perpendicular to the lathe axis but angled to the wheel axis.  Tried to post a sketch but failed, will try again!
John

[JohnC]

[embed=425,349]<iframe width="480" height="360" src="http://s1094.photobucket.com/user/JCphotob/embed/slideshow/"></iframe>/embed]

Sorry, best I can do for now is a link to photobucket!
John

[John Hill]

Fergus, ornamental turning is interesting and, I think, uses a sliding spindle so I will have to think about that some more!  We have one of the world's best collections of Holzapffel and other OT lathes in our town and maybe I should pay that museum another visit!
Thanks.

JohnC,  I have tried to avoid anything that tilts the wheel for cutting the groove as that will complicate things when I try to put a follower in the groove later but I might have to resort to that method eventually!
Thanks.

[BillTodd]

traditionally techniques such as a dividing head gear coupled with the milling table can produce simple cams and spirals.

To produce your cam , I'd suggest drawing or printing the shape as a graph with displacement against angle . you can then either wrap the print around the part and carefully follow the path, or use the coordinates with a dividing head and dro.

if you want just a simple ellipse,  you could cut a suitable piece of tube at an angle then use the cut face as a guide.

[John Hill]

Thanks Bill but how to handle backlash when the table changes direction?

I have been wondering if there is any established technique that moves the lathe top slide back and forth (that is with the top slide turned parallel to the spindle)?

[BillTodd]

backlash isn't too much of a problem if stepping and plunging on a mill.

you might be able to turn the groove , albeit slowly , if you mounted the cut tube  on an arbour with the work piece and arranged a spring loaded cam follower on the topslide (you would have to remove the leadscrew)

you may find inspiration if you look at spiral oil groove cutting techniques on the web

[John Hill]

Oil groove!  Good reference Bill as it seems a lot of people have made weird and wonderful methods of cutting the figure eight grooves!

John