In spring 2007, a good friend, Roland Hege, in my local wood turning club, Southern Piedmont Woodturners in Concord, North Carolina, USA, thought I might be interested in his proposed construction of Jon Magill's MD Rose Engine. He was right. I have been wood turning for a while and felt a Rose Engine would be very handy to add some unique decoration to some of my wood turnings. Little did I know what all could be done with an Ornamental Rose Engine.
So, after much research and very little practical information I set about to build my own design for my prototype Rose Engine. I did not know the full capabilities of a Rose Engine since my friend, Roland, had not finished his and neither of us had seen a working machine. I did quickly discover that purchasing a European antique Rose Engine was way too expensive for me. Over one hundred years ago a new Rose Engine cost about the same as a European country estate and today an antique machine still is very expensive.
I have the highest respect for the purist in Antique methodology in any field. The old Rose Engines are works of art themselves and I am intrigued by the Victorian methodology. Especially, when I consider that they were built with very limited tooling and materials. As I have been fabricating the parts of my Rose Engine I've really gained respect for the old craftsmen and of how time consuming and difficult it would be to create one these masterpieces without modern technologies.
Unfortunately, I personally do not have the resources or the inclination to pursue a strict Victorian methodology in my Rose Engine work. I don't have a problem using electricity, lights, electric motors, plastics, metal alloys like aluminum and tool steel, ball bearings, accurate drilling and the other technologies that were not available in the Victorian Rose Engine period.
I know there is a group of Rose Engine craftsmen that prefer to use the authentic Victorian equipment and adhere to the Victorian techniques. I am unfortunately not included in this group.
Contained on these pages are some notes, comments, photographs of the construction process and a gallery of test pieces.
After two months of planning, research and drawing; it took me about a month to fabricate my prototype Rose Engine to the test stage. The headstock moved in both rocking and pumping motions with the tail stock coordinated for both motions. After testing it, I was not happy with the overall sturdiness of the machine. The cumulative effect of the light weight machine and overall fit tolerances was showing in the work. I now firmly believe that a Rose Engine must be fabricated to very, very tight tolerances to produce clean detailed work.
About the same time I was able to rig a test on my prototype, I discovered and joined the ¨Society of Ornamental Turners¨, the oldest ornamental turning club in the world. Copies of all of their bulletins since 1948 are available for their members to purchase. This is the most comprehensive collection of information about Ornamental turning and Rose Engines I have been able to find. I was also able to obtain a copy of The Principles & Practice of Ornamental or Complex Turning by John Jacob Holtzapffel. He perfected and manufactured high quality ornamental lathes and built a few Rose Engines in the 18th century.
I was also able to communicate with a very experienced and respected Rose Engine expert, Ghost Duplessis in New Orleans. His most valuable help cleared up most of my application and design issues and I decided to stop work on my prototype and completely redesign my Rose Engine.
At this stage of development, I wanted my improved custom Rose Engine to produce the most superb work possible. The basic design and fabrication criteria would be to fabricate the highest quality rose engine within my capabilities.
Following is a list of my second generation Ornamental Rose Engine design criteria:
The Rose Engine
- It needs to produce the finest work possible
- It needs to have the 16" diameter work capacity of my wood lathe.
- The spindle thread must be 1.25"x8 tip to fit wood turning chucks and have a Morse Taper.
- The spindle head must be adjustable for level and run out.
- It must perform both rocking and pumping headstock motions.
- Rosette cam changes must be quick and easy.
- It needs repeatable, fine phase adjustment between the rosette cam and the spindle.
- Cutting tools must move in X, Y & Z axes and allow all axis rotational adjustments.
- The spindle must have provision for thread cutting the work.
- The Rose Engine should attach to most wood lathe bed ways for mobility.
- The spindle should be driven by a hand crank and a variable speed motor.
- The tail stock should coordinate with rocking motion.
- The spindle should be lockable to any combination of 360 divisions for ornamental index work with adjustable phasing.
- It should be stiff enough to perform engine lathe work on the softer metals.
The resulting design of this custom Rose Engine & Ornamental Lathe is made up of ten basic assemblies: (The following link within this document.)
- The spindle head
- Thread cutting
- The rosette cam
- The index and phasing system
- The rubber assembly
- The cutter alignment device or compound X-Y table
- The cutter and motor
- The lathe bed or table
- The chuck or work piece holding device
- The chuck alignment adjusting spider
How many different cuts can be made with a Rose Engine? The correct answer is a very large number. Following is a list of the current cut combinations possible on this Rose Engine. Several variables, like the depth of cut variable, are continuous. Actually, even very small changes in anything show up in the work so I think these figures are very low. As currently outfitted, this Rose Engine can make about 9,331,200 different cuts by changing combinations of the following variables.
|List of variables that will change a cut on this custom Rose Engine:
|Rosette cams - lobe count 6, 12, 12a, 12b, 18, 24, 36, 48, 24e
|Simultaneous 2nd Cam - lobes= 4, 6, 12
|Rubber shapes - pointed, slight rounded, square end
|Cutter shape - pointed, round, concave round, concave V
|Cutter diameters - 1",1.5", 2", 2.5", 3", 5"
|Depth of cut or Z-axis - light, medium, deep (no original surface left)
|Cutter position in X-axis - 3 positions front, 3 positions rear of center
|Cutter height or Y-axis - center, 2 positions above, 2 positions below center
|Cutter angle in relation to horizontal plane
|Work piece shape - same as cutter radius, not the same; either end or center same shape
|Total possible combinations of cuts:
I calculate the cuts possible with a fully outfitted Rose Engine to be over 400 million. That is with a regular chuck. Other complex chucking devices would greatly increase the number.
The spindle is the very heart of the Rose Engine. I wanted mine to be made to very tight tolerances. So I asked my friend Brian Dutter, a very skilled and conscientious master machinist with a reputation for the finest quality work, to fabricate it for me. It is threaded 1-1/4¨x8 tpi to fit standard wood turning chucks and accessories. Tommy holes are located behind the chuck thread to hold the spindle while loosening a chuck. The head bearing is a radial angular contact back to back ball bearing to take any thrust load. The spindle is threaded for a spanner nut to secure the main bearing. There is a key way cut for the cast iron drive pulley. The back spindle bearing is a deep groove ball bearing. Each bearing surface on the spindle is a different diameter to ease installation of the bearings. There is also a key way for the main index wheel. The back end of the spindle is threaded for the brass rosette cam tightening nut to allow quick rosette cam changes and adjustments. Also, different pattern sleeves for threading can be installed on the back of the spindle for cutting various pitch threads. The spindle has a 3/8¨ through hole for a draw bar and a number 2 Morris taper in the front end. The spindle fabrication required a lot of work. I feel pretty sure that the conversion of an existing wood or metal lathe to a Rose Engine would be much more economical from the spindle standpoint.
Almost all of the antique Rose Engines I have seen in photographs have sleeve bearings for the main spindle bearings and for both the rocking and pumping motions. With Rose Engine work, we are trying to do very very delicate work by moving a heavy spindle head with the work piece by the rubber moving over little hills and valleys on the rosette cam. So in order to reduce the spindle head movement friction as much as possible, I decided to use all ball bearings allowing motions with very little force on the rosette cam. Hopefully, this will facilitate the more delicate work. Even though the spindle head of this Rose Engine weighs 40 pounds, its rocking and pumping motions are extremely smooth and sensitive.
The round drive belt is routed with idler sheaves so that either forward and reverse cranking directs the acceleration forces directly into the headstock pivot bearings center pivot point. This keeps the spindle head in balance no matter how large the torque forces originating from irregular hand cranking or resistance from high rise rosette cam lobes. None of the cranking force will change the spring tension force on the cam lobe. Thus, the hand cranking forces will not add to the force of the rubber climbing the rosette cam lobe. This minimizes the cam lobe disengagement from the rubber and much less spring pressure is required for consistent cam to rubber contact.
The hand crank has a 6" radius handle which allows steady slow turning if necessary. The high count, high rise or sharp pointed cam lobes need to be turned very slow to produce a smooth cut. One revolution per minute or less for the spindle is not uncommon.
I plan to have a geared down electric motor with step idler pulleys that will give 1/4, 1/2, 1 and 2 rpm spindle speeds.
The Rose Engine uses a half nut thread follower, clamped in the rubber clamps, on the rear end of the spindle for cutting threads in a work piece. The headstock spindle assembly and work piece moves on the linear bearings as the spindle is turned while engaged with the thread follower. A 60 degree double angle cutter is used to cut the threads. If threading other than the Cabarrus Standard 12 threads per inch is desired, a threaded sleeve would be installed over the rear spindle end with the appropriate threading and corresponding thread follower. The design allows a little over an inch of threading length capacity.
A nice feature of this system is that at any time during the thread cutting operation the headstock can be rocked to disengage the lead thread follower and at the same time rock the work piece away from the thread cutter. This feature works when the cutter is positioned on the back side of center when cutting inside (female) threads and the cutter is positioned on the front side of center for cutting outside (male) threads. This is the same concept as engaging a threading half-nut on a metal lathe.
A 36 hole index wheel is fixed to the spindle by key way. The side of the index wheel toward the spindle used to secure the spindle in any of 720, or 1/2 degree, positions for ornamental work. Each rosette cam has 20 vernier holes to divide each main index wheel hole. This rosette cam vernier will also give 720 half degree divisions to adjust the cam position in relation to the spindle (work) when doing Rose Engine work. This results in 0.009¨ positioning ability on an 2 inch diameter work piece. Smaller increments can be adjusted with the cutter height if necessary.
The shape of the rubber travel and thus the rosette cam can be determined by doing a little geometry and drafting using the desired final design shape and diameter. This procedure is reviewed in an article by Amateur, "Making A Rosette from a Pattern", in the Society of Ornamental Turners Bulletin #46 page 22 March 1972. In summary, one complete phase of the rosette cam shape must be cut as a master. This can be done by hand or any method you can devise. I used a milling machine and band saw to cut several. My friend, Roland Hege, cut several Sine wave shapes for me with a CNC milling machine. If one rosette cam lobe master can be somehow formed, the rose engine index feature can be utilized to repeat that master cam lobe around the a rosette cam with the rose engine itself. A rosette cam design can easily be cut inverted with the Rose Engine by clamping the rubber on the rubber rest on the opposite side of the cutter and duplicating a cam. The rosette cam lobes then become valleys and the valleys become lobes. Although, the the valley cut of a rosette cam will not have a smaller radius than the radius of the cutter.
The rosette cams are also drilled with 1/8 and 1/3 phase adjustment index holes so different indexed spiral rates or pattern repeats can be obtained in relation to the rosette cam lobe phase. Simply loosen the knurled brass cam nut and change the rosette cam, add rosette cams or change the phase of the rosette cam. This design allows use of any number or combination of rosette cams at the same time.
I have been using Ultra High Molecular Weight Polyethylene (UHMWPE) for rubbers. It's almost as slick as Teflon and cuts and machines very nicely with sharp tools. I get it in 3/4" square bars and cut it to 4" lengths and whatever end shape I need. I ordered last from http://www.mcmaster.com for $2.46 per linear foot. The Part Number is 8702K111, Polyethylene (UHMW) Rectangular Bar 3/4" Thick, 3/4" Wide.
"Ultra high molecular weight polyethylene, is a very tough material, with the highest impact strength of any thermoplastic presently made." "It has a very low coefficient of friction, is self-lubricating, and is highly resistant to abrasion (15 times more resistant to abrasion than carbon steel). Its coefficient of friction is" ... "comparable to that of Teflon, but UHMWPE has better abrasion resistance than Teflon. It is odorless, tasteless, and nontoxic." (quotes from Wikipedia)
This seems to me like the very best material to use for a friction rubber since it is so easily machined and has such a low coefficient of friction which results in negligible wear to the rosette cams and the rubber itself. Also, the price of $0.62 each plus shipping for a simple rubber is difficult to beat. I've used one particular UHMWPE rubber pretty exclusively for about 6 months with no noticeable wear. I do put a drop of oil on the rosette cam and my spring pressure is only about 1.3 pounds.
I think a ball bearing rubber has the lowest friction of any rubber we could use. Different diameters of ball bearings will produce different cutting results so a different shape rosette cam is required to get the same cut result as with a pointed rubber. The relationship between the diameter of the work piece, the diameter of the rubber and the diameter of the cutter determine the shape of the cut resulting from any one rosette cam shape.
The cutting tool must be held very steady and in a repeatable position. An X-Z compound milling machine table with 0.001" adjustments is used. A 0.010 deep cut is a big cut with a Rose Engine. I put one each hex-head gib screw in the X and Z gib adjustments to allow convenient adjusting of the tightness of the tables.
I plan to use several different cutting devices. So, I fabricated a round tool post on which will be clamped the cutting tool, allowing the cutting tool to be positioned at any height or angle to the work piece. A wood router, WeCheere cutting tool, a handmade drilling frame or any other type of cutting tool can be used by making different tool clamps to fit the tool post.
A metal lathe quick change tool post is also fitted to the X-Z compound with a vertical spacer block. The 1/2" square and boring bar tool holders can be used to attach the various cutting frames. Also, the quick change tool post will give about one inch of repeatable vertical adjustment.
I first used a Porter Cable router with a variable speed control to drive my cutting tools. I find I'm using a 1/2" boring bar with a 90 degree 3/16" square cutter the most. I have several boring bars setup with 90 and 45 degree cutters with different length and shape cutters. This arrangement has been used in the vertical, horizontal and odd angle orientations. I can see the limitation of the router arrangement is the physical size of the router body in two aspects. One is the size of the router prevents locating the cutting tool where needed. So far this has only been a problem decorating the inside of bowls. The other problem is when the router is rotating in the horizontal plane it is physically in the way of seeing the cutting action from my comfortable work seat. This Rose Engine is large enough to rotate the router to any angle in relation to the work. So, I could turn the router over 180 degrees and cut in the other direction. I have turned a 5" diameter cutter tool with good results.
My first overhead drive was mounted on a cross bar elevated above and attached to the lathe bed. To eliminate any possibility of drive motor vibrations effecting the cut quality, I decided to build a free standing overhead drive crane. The articulating arm design of the crane head allows locating the cutting device anywhere along the lathe bed. This is a very convenient arrangement. A work light is mounted on the other end of the crane arm.
The first universal cutting frame is fabricated from 6011 aluminum and is designed for 3/16" round cutters that can cut from 7/8" to 3.25" in diameter. All bearings are ball bearings. It can rotate to any cutting angle and cut from 4" to 5.5" deep into a hollow vessel. It will be mounted in a 5/8" boring bar attachment for a quick change metal lathe tool post.
The cutter is driven by a 1/2 HP variable speed motor through an overhead round urethane belt drive system. An overhead drive for a cutting frame allows the motor to be detached from the cutter assembly. The overhead can be moved to different locations on the cross bar and rotated to any position. The tension on the belt can be changed by moving the pivot point to other positions on the pivot arm. Jon Magill, thank you for the suggestion of the PSE variable speed motor. It has plenty of power and is very smooth and quiet.
Drawings of my universal cutting frame are available for download in the Download section of his website.
This universal cutting frame is quite a project. Even though, I tried to make the design as simple to fabricate as possible, there just are a lot of setups that need to be fairly accurately machined. The cutting frame itself is made up of 5 frame parts, a cutting head and ball bearings, two axles, two idle pulleys with ball bearings and a double drive pulley with double ball bearings. All that stuff needs to be milled or lathe cut to dimension and have holes accurately bored, drilled and/or tapped.
Thank you to all who have provided guidance.
I an using a cast iron wood lathe bed to mount the Rose Engine. Utilizing an existing lathe bed for mounting the Rose Engine would mean it could be used on almost any wood lathe. I am lucky enough to have an extra Jet wood lathe to dedicate to the Rose Engine. The self centering T-nuts attaching the machine to the lathe bed are made to fit on my Jet wood lathe and also on the wider ways of my wood turning club's Powermatic wood lathe. Although they would not be not self centering, the T-nuts could easily be made as bar nuts to fit any width lathe ways. Later I will make a universal set of bar nuts to use my machine on virtually any wood lathe bed.
I will have to fabricate a set of pivot bearing shims to raise the spindle head assembly to the correct rubber height when using the Rose Engine on the wider ways of the Powermatic wood lathe. The machine is designed for the main pivot ball bearings to rest directly on the cast iron ways of my Jet 1242 cast iron lathe bed.
I originally did not really like the accuracy of the threading system of wood turning chucks. My prototype concept was to fabricate a faceplate directly on the spindle and use a center hole for alignment in attaching chucking accessories. The problem was, I would have to custom fabricate every chucking accessory including a male thread for a regular wood turning chuck. I finally decided a spindle thread of 1.25¨x8 threads per inch would be the most practical choice to allow use of standard wood turning chucks, face plates and Cole jaws. Other chucking devices could still be fabricated or adapted if needed. For instance, an eccentric chuck would be nice.
The spindle of this Rose Engine has the common wood turning lathe chuck thread of 1.25¨x 8tpi. Since my chucks are threaded very deeply I extended the threading of the spindle about a 1/2¨ longer than normal. This seems to have very much tightened the fit between the chuck and spindle over that of the regular wood turning lathes. I did not have to buy any new chucks to start working. So far, I am using large and small jaw sets on a Oneway Stronghold chuck, a set of large Cole jaws, two face plates and various MT-2 taper chucks for mounting work pieces. The stronghold chuck seemed overkill at first, but it is extremely nice for holding a long work piece. With a 1"x8 tpi adaptor I can use all of my smaller threaded chucks. It is very convenient to be able to move the chuck and the workpiece from the regular wood turning lathe to the Rose Engine for embellishment and, move it back again if necessary.
A necessary accessory for chucking work is a magnetic stand and a 0.001¨ dial indicator to center the workpiece in the chuck before work. The work piece must be centered on the spindle to within a few thousands of an inch to produce finely detailed work consistently around the workpiece. This is not as much of a problem when the piece is totally cut on the Rose Engine.
Roland Hege and I have designed, specifically for a Rose Engine, a spindle to chuck adjusting spider for very fine adjusting of the chuck and thus the work to the center of rotation of the rosette cam. This spider apparatus will allow corrections for any of the systems (rosette cam, spindle or chuck) that might not be exactly true with the spindle rotation. When doing very light cuts of a few thousandths of an inch, the work absolutely must rotate true or the error will be obvious in the work. This is especially true when making light cuts in plastic or metals.
The chuck spider allows adjustment between the spindle center and the work center in all three axes. An 8.5 degree turn of an adjusting screw moves the spindle 0.001 thousandth of an inch. So, fine adjustment is very easy. It does not take but a few thousandths run out anywhere in the Rose Engine from the cam to the workpiece to show in delicate cuts.
Brass tipped set screws are used to keep from damaging the adjustment surfaces and ensuring smooth accurate adjustments.
Several conditions can cause chuck and thus work run out and the effect can be additive:
- The chuck seats differently on the wood turning lathe spindle used to rough cut the workpiece than it seats on the Rose Engine spindle.
- Dirt on either the roughing wood lathe spindle threads or the rose engine spindle threads.
- The cam center hole is not cut in exact center of the valleys of the rosette cam.
- The cam hole is bored too large. If the hole is only bored 0.004" too large the run out could be as much as 0.008".
- The rose engine spindle nose threads and face might not be perfectly aligned with the spindle bearings
It is a real luxury to be able to easily and precisely center the workpiece with the cam action. You can mount a previously turned work piece in the rose engine chuck and center it quite easily. I am most pleased with this addition to my Rose Engine and now consider it an absolute necessity.
The spider can be quickly adjusted if adequate measuring surfaces are cut on the workpiece. First, lock the Rose Engine headstock so it can not rock. The axial adjustment is accomplished with the set screws on the back of the spider and aligns the line through the center of the spindle to be parallel with the line through the center of the work. To accomplish this the workpiece must have a flat surface on the edge of the face of the work to indicate (measure with an indicator). The maximum and minimum values are noted, the indicator is set to "0" at the value half way between and the back set screws are adjusted to the "0" value. The indicator should show the same reading as the spindle and workpiece is rotated with the headstock rocking motion fixed.
Second, unlock the spindle and install the cam that will be used to cut the pattern. The radial adjustment is accomplished with the set screws on the sides of the spider and aligns the work center line to correspond to the spindle center line. To accomplish this the workpiece must have a small portion of the outside of the work piece cut as a cylinder surface to indicate. While rotating the spindle and workpiece the values of the indicator for each of the cutting positions (rosette cam valley positions) are noted and the same maximum and minimum procedure as above is used to center the work piece.
Now, the workpiece is exactly centered to the cutting action dictated by the rosette cam and any misalignment's are corrected. It takes less time to do than to explain.
rocking tail stock