Have a look at the article by Geoff O'Loughlin on making a rose engine.
It is on the OT page and the projects page of our site at http://www.vicnet.net.au/~pwguild

Regards
Brian

Yeah looks great

Given my surname, I really have to build one of these one day...

Cheers,
Andrew

although this is used for metal it is the best example of a rose engine that I have found. Be sure and watch the video segments.

http://www.rgmwatches.com/engine.html

Here is what i came up with as a copy of Geoff's design. I made several changes based on availability of parts.

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What does the cam run?

I've also been building a rose engine, albeit one more suitable for face turning I think. I should have it finished in, oh... [counts on fingers] ...about 10 years if I pick up the pace.

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The oval cam is for when I get enough nerve to turn an oval box, the headstock will rock side to side and follow the cam. The round cam (rosette) will have a wavy pattern cut into the face to provide the back & forth motion (pumping) of the spindle. I found plastic rosettes on ebay, but they were about $275 US, which is a little more than I want to pay at this point.

I'm still concerned with my ability to make any face turning or anything else at this point.

Ah. I see. Same principle, different placement.

So, you gonna make your own rosettes? I was talking to a bloke a while ago about making my own and he reckons that a larger diameter would be easier to make by the average woody. The "depth" of the wave would remain the same, but it'd be more forgiving of minor errors in getting the flow of the curves just right.

However, a larger dia means it needs to be made of thicker material to stop flex, which all adds to the total moving mass. Probably OK for a hand-turned shaft, I guess...

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Very nice setup, ihog. Is the speed controller for the cutter? I.e. you're turning the headstock by hand?

I'm considering putting the rosette and cam outboard of the headstock for easier swapping, but I haven't worked out the gory details yet. Most designs seem to have a stack of cams and rosettes preselected and inboard of the headstock bearings. I suppose that's OK, but the headstock has to be dismantled for new additions.

It looks like you've shamed Skew and me (and others) into accelerating our schedules - maybe only 5 years instead of 10?

Looking forward to your productions. It's about time we got some more posts on this sub-forum.

Joe

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Of course truth is stranger than fiction.
Fiction has to make sense. - Mark Twain

Joe,

Geoff said that his cutter turned at about 4,000 RPM and the trim router spins at about 18,000 RPM, so I needed a way to slow that thing down, and the controller was only $20 US. The spindle is turned by hand.

BTW, I couldn't find a spring so I wrapped a coat hanger wire around a dowel and made my own red neck spring.

That's probably OK for the breadboarding stage. But coat hanger wire is annealed, and doesn't have much of an elastic range. Decent springs are hard to find at the big boxes; usually only small and useless for substantial applications. I suggest you consider a truck valve spring or two from an auto parts store. These often consist of two nested springs: stiffer outside with a less stiff inner coil. They do this to fine tune the elastic response. Use only the inner coil. For longer range of motion, stack two (or more) of them with (a) washer(s) between.

Joe

__________________
Of course truth is stranger than fiction.
Fiction has to make sense. - Mark Twain

Joe,

You are right about the springs being hard to find. The valve springs are way to stiff to use. The coat hanger wire actually works just about right, because I can apply more pressure by tightening the back nut. Also, if I lose spring, I can always stretch the wire out and recoil it.

You don't want to overcome a lot of pressure with just a rubber against the rosette, but you need enough spring pressure to return the spindle to it's original position.

I need to change the direction of the grain on my oak rosette in order to cut it. I need to be cutting into the end grain, and not across the grain.

True enough about the stiffness of the overall valve spring. But the secondary springs are quite a bit softer. Also, placing several of them in series reduces the total stiffness. For example, if an individual spring has a spring constant of 50 lbs per inch (won't actually compress that much; that's just the stiffness), 2 of them in series will have a constant of 25 lbs per inch, or about 6.25 lbs for 1/4 inch compression.

All that said, if the coat hanger wire works OK, fine and dandy. Key to preserving or increasing elastic (i.e. non-permanent) range is to use lots of coils, as long as they don't bottom out.

Joe

__________________
Of course truth is stranger than fiction.
Fiction has to make sense. - Mark Twain

The spring from the "bendix" mechanism in a starter motor might work.

__________________
Ian (Robbo) Robertson
"We do good turns every day"


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Robbo, I knew somewhere I had seen a spring that would work. Now it's off to the salvage yard.

I also determined that I need to make the rosette's out of Perspex or Lexan.