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Wood Model of a Clutch

This is the 2nd wood mechanical marvel I have designed from thebook 507 Mechanical Movements by Henry Brown which is a reprint of a book first written in 1868.

The pinion at the top gives a continuous rotary motion to the gear below, to which is attached half the clutch, and both turn loosely on the shaft. When it is desired to give motion to the the shaft, the other part of the clutch, which slides upon a key or feather fixed in the shaft, is thrust into gear by the lever.

Most of Levy's mechanical marvels fit within a 12" long by 6 deep by 6" high envelope. I tried to make my design fit into roughly the same envelope.  Here is start of design from Google Sketchup:

This is a challenging design. One must design the 2 gears and make them.  One must also design the clutches and make them also. 

 I found this link to design and print a paper template for the wood gears.

The gear design I chose was pressure angle of 25, gear one = 28 teeth, gear 2 = 14 teeth, and pitch was 11.85.  Large gear had pitch diameter of 4" and small 2". Shaft hole was 3/4" in both gears. I glued the paper templates onto 3/4" oak blanks using white Elmer's glue.....then bandsawed them:

After bandsawing, the paper and glue wipes off easily using warm water and a dishrag. On the small 2" pitch diameter gear, I sanded the OD of the gear blank before bandsawing just with my hand.  On the larger 4" pitch diameter gear, I put the blank on a 3/4" dowel and used the drill press sanding drum:

To test the gear set, I mounted both of them onto dowels located in a 2x4.  I started with 3 inch centerline, the theoretical centerline distance for a 2" and 4" pitch diameter gear set.  That was too tight as expected.  I increased the centerline distance to 3-1/8" and they turned reasonable well, with some rough spots. I took the dremel with a sanding drum and gave a lead in chamfer on the outside of each tooth. The set spun smoothly after that.

Here is my temporary set-up for trying the 2 gears:

Here is video showing the 2 gears running freely.

I turned a walnut split log down into 2.5" OD for the clutch pieces. I decided to drill 3/4" dia holes, 2 of them at right angles, in one piece to create the female portion of the clutch. To make the male potion, I set the table saw at 3/8" thickness, and pushed in a 3/4" dowel about 8" then shut the saw off.  This gave half a dowel thickness...or a half moon shape.

11/15/09.......going on the road for a week, so will have to wait until thanksgiving to finish up this model 


Got back from being on the road.  Decided the male 1/2 dowel pieces were not lined up correctly with female clutch piece. Used radial arm saw to saw off the glued on male pieces. I then put male and female clutch pieces on 3/4" dowel, clamped dowel in vice. and positioned new male pieces for gluing:



I then tested the fit, and where required used the Dremel tool with its small sanding drum to enlarge the female areas....until I got the best fit possible.


Next, was to make the shifter piece on the lathe.  I used a 3/4" Forstner bit in the lathe to center bore this piece:




Once I had the ID bored, the OD turned...I was ready to cut it to length in the lathe using a hacksaw:


I also had to cut a 1/4" keyway into both the 3/4" shaft and the female clutch piece. On the female clutch piece, I re-hung the blade in my hand coping saw, then sawed a 1/4" wide by 1/4" deep keyway.  I used a 1/4" wide sharp chisel to complete the square keyway.  I used the Dremel with a cut-off wheel to cut the long edges of its keyway, then a chisel to finish it:


I then had to glue the round pieces together.  I glued them while still on the 3/4" shaft to keep alignments correct:


I glued up the bearings which hold the small gear also.  I allowed 1/8" clearance to allow for polyurethane coats of the parts:


On this project, I partially designed Clutch no. 48 in Google Sketchup, then made the parts. I now need to update google sketchup to the actual design...then make the base and back plates to mount the items.


 Here is the updated Google Sketchup drawing of Clutch No. 48:


 Now it is time to dry clamp up the assembly and see how things work.....or don't work

Everything fit ok, except purple shifter needs to be 1/4" longer.  Must be mistake in Sketchup model somewhere.  Made new piece 1/2" longer.

The only problem I had was that the gears spun even when the clutch was dis-engaged. Two possible solutions..1)add a piece of ash spring on top of the top using clothespins to hold playing cards on your bike tire to make noise.  Other solution was to buy 2 thin nylon washers and put on each side of small gear to increase friction.  I bought 2 nylon washers at Ace Hardware and sanded them to optimum fit.


I also decided to use a 3/4" inch cap versus 1/8" dowel to retain the purple shifter.  Here is an updated Sketchup drawing of the model using a cap.

Here is a link to a higher quality picture of the Sketchup 3D drawing


And now for the finished model of Clutch Number 48:


 Link to Jacob Maley operating Clutch No. 48






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