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Attaching Cams, Pulleys, Cranks, Gears and Handles to Wooden Shafts – Dug’s Tips 4

June 15, 2011 by  

Attaching Cams, Pulleys, Cranks, Gears, and Handles to Wooden Shafts

To get things moving in an automaton, some parts must be attached firmly to round wooden shafts. But how? And which way is best for your project? Read on! The techniques discussed below apply to cams, pulleys, eccentrics, cranks, gears, handles, and other parts. I’ve used the term “cam” throughout to simplify the descriptions.

Glue the Cam to the Shaft
If you don’t plan to remove the cam from the shaft, glue is certainly an option. However, if you need to fix or change the mechanism, it’s nice to be able to take it apart easily! That said, glue has its place — especially for simple automata with few parts.

Tip 1: Try using a small amount of cyanoacrylate glue (e.g. Super Glue or Krazy Glue). These glues have a low shear strength. Should you need to remove the cam, a sharp blow parallel to the shaft can break the glue’s bond, hopefully without damage. Apply a bit of acetone or nail polish remover first to soften the glue.

Tip 2: If you don’t want wooden parts to come apart, use polyvinyl acetate (PVA) wood glue, commonly known as “yellow glue” or “carpenter’s wood glue”.

Drive a Fastener Through the Cam
Drill a pilot hole into the edge of the cam and into the shaft, then insert a pin or faster. Generally, this method is easiest to use on thicker cams that are not too large. You have several fastener choices:

Small Nails (also known as brads, panel pins, and gimp pins)
A small-headed round-wire nail can be driven though the cam and into the shaft. Try to get the nail all the way through the shaft and into the opposite side of the cam. If the nail has a raised head, drill a slightly larger opening to recess the head. This is a simple, tidy solution that can be used on smaller diameter shafts, although the nail can be difficult to remove without damaging the wood.

Small Wood Screw
A long, narrow wood screw can also be used. This approach requires a thick cam. It also helps if the cam has a spot on its circumference that is not too far from the shaft. You’ll want to countersink the screw head so that it’s below the surface of the wood. This method is reversible, strong, and particularly useful for attaching hand-cranks to the ends of shafts.

Metal Rod
A short length of brass rod can be inserted into a hole drilled all the way through both cam and shaft. The hole in the shaft should be no larger than 1/3 the diameter of the shaft. Try to drill the hole through the exact center of the shaft. Because the rod can be pushed through and out, this arrangement is easy to take apart.

Wooden Peg
Wooden pegs can be used in a similar manner to the brass rods mentioned above. Pegs made from toothpicks can be used on somewhat smaller shafts and are nearly invisible in cams made of Baltic birch plywood. Hardwood pegs of a larger diameter are easier to remove, however.

Tip 1: Use a V-block to help you drill straight into the edge of the cam. This helps to ensure that the pin enters perpendicular to the shaft and is parallel to the cam’s sides.

Tip 2: Toothpicks are between .075 to .086 inches in diameter. Use a drill bit between #49 and #44, working your way from the smaller to larger size to get a perfect fit.

Use a Screw Eye and Screw
For this method, a screw eye is turned into a pilot hole in the shaft. Slide the cam onto the shaft, against the screw eye. Finally, drive a small wood screw through the eye and into the cam. A well-chosen flat head wood screw will seat neatly inside of the screw eye. This method is easy to disassemble, provided that other parts of the mechanism are not in the way. This method may be used for somewhat thinner cams.

Tip 1: Over-tightening the screw can cause the cam to tilt on the shaft. If this happens, use a thicker cam and ensure it fits tightly on the shaft. You can also bend the screw eye slightly to offset a tilt.

Tip 2: Seat the screw eye into the shaft such that its neck is buried completely into the shaft. This allows the lower portion of the screw eye to bear some of the rotational force.

Collar Glued on to the Cam
Glue a small block of wood, round or square, onto the cam to serve as a collar. Then, attach the collar to shaft with a fastener. The collar should be securely glued to the cam. For the strongest glue joint, orient cam and collar such that the long grain of the wood is used as the gluing surface for both pieces. The hole running through both cam and collar should be carefully aligned. This technique is the best choice for thin cams, and is the easiest to disassemble.

Tip 1: If aligning the holes in the two pieces proves difficult, use the base end of a drill bit the same size as the shaft to align the parts while gluing them. Rub a bit of candle wax on the drill bit to prevent the wood glue from sticking to it.

Tip 2: A tight fitting wood screw with its tip ground flat can act a set screw that presses against the shaft to hold the cam in place. This arrangement will allow you to reposition the cam on the axle. Be careful though: don’t apply too much force to the screw or expect it to hold under a lot of pressure.

There are many other ways to attach parts to wooden shafts, but these methods should serve you well for most situations. And as for attaching things to metal shafts: we shall have to leave that topic for another time!

Dug’s Automata Tips, Techniques and Tricks
A quarterly column by automata-maker and enthusiast Dug North

Copyright 2011 Dug North

Warning: The topics covered in this column include the use of tools and materials that have the potential to cause damage to property and/or bodily injury. Your safety is important and it is your sole responsibility. Always read and follow the safety instructions that come with tools and materials you use. Wear safety glasses, use guards and other forms of safety equipment, follow safety precautions, and use good judgment. Seek the guidance of experienced outside sources whenever required.

Comments

13 Responses to “Attaching Cams, Pulleys, Cranks, Gears and Handles to Wooden Shafts – Dug’s Tips 4”

  1. Karl Franklin on June 17th, 2011 12:53 pm

    Your blog is the best in the world. It is the first thing I check when I go online! I love all the varied automata that you find. I have started (drawn anyway) adding automata techniques into my homemade furniture designs. Pulleys and cranks for opening doors, weights for closing them, etc.
    Keep up the GREAT work!

  2. Marcelo Kraiser on June 20th, 2011 9:53 am

    Great blog!
    Best regards and thanks for the tips and posts.

  3. Dug North on June 20th, 2011 5:01 pm

    Karl – Best of luck with adding the automata techniques to your furniture designs. It’s a great idea. While your at it, you might also consider some nifty secret compartments.

    http://www.finewoodworking.com/SkillsAndTechniques/SkillsAndTechniquesArticle.aspx?id=26008

    All the best,

    -Dug

  4. Dug North on June 20th, 2011 5:02 pm

    Marcelo – Thank you! We’re glad you like the tips!

    -Dug

  5. Benjy T on July 20th, 2011 1:47 am

    I’ve just discovered this Marvelous site and I think I’m in Heaven! Anything mechanical has long been a fascination of mine, esp. musical instruments. In years past when re-building player pianos a type of glue from animals(please don’t think me a barbarian) was used to to glue wood together as it could be easily heated, saved and re-heated and joints broken apart with little to no splintering with simply the application of heat. It was how the pianos were originally made in the early 1900′s and is still available from The Player Piano company in Wichita, KS, USA. This subject is probably covered elsewhere in this “treasure trove” but I thought that I’d just toss it out once again.
    I look forward to many more fun evenings perusing your vast Wealth of Knowledge!
    sincerely,
    B Templeton

  6. James Webb on July 25th, 2011 10:15 am

    Dear Doug, What a world we live in when you have to include a warning about the use of sharp tools or procedures in which one can get hurt ! “Duuuuuuh!”
    When was growing up, we didn’t have X-acto tools but made razors to cut balsa parts for model airplanes from used, broken razor blades. I was a right of passage in getting a few razor cuts and then to experience a bit of model airplane glue getting in the cut. This was the era when one could use airplane “Dope” and not get arrested !
    Plans of some of the models I built can be found on http://www.solidmodelmemories.com

    Last Tuesday, I myself became part automata when I had a stent made out of Goretex placed in my abdominal aneurysmn. The procedure only required an overnight stay in hospital. Now I must carry a card to get through security scans because the stent is wrapped with wire.

    No, the walking aneurysmn, Al Gore, has nothing to do with this product ! Gortex was originally developed by DuPont as a synthetic leather that cold breath. The only problem was it would not stretch in use. The patents were sold to a European country where they made shoes. Now it’s come full circle in medical uses ! My wife is part automata with her having new knees put in place !

    I now return to continue building automata just for fun and few bucks that might come my way !

    The Spider

  7. James Webb on July 25th, 2011 10:34 am

    “Oooooops !” I made a mistake !

    The correct website for all the model plans of the thirties and fourties is;

    solidmodelmemories.net I forgot the leading letters, but it’s not www.
    Just Google this address and you’ll get to the site.

    “QUESTION !” “HELP !” I wish to make my own small bellows but cannot find plans anywhere ! Are there plans available ! I some automata I’d like to “voice !”

    Thanks for the help !
    The Spider

  8. Dug North on July 29th, 2011 6:05 pm

    Spider,

    Thanks for the correction on that web site. It looks like the address is http://smm.solidmodelmemories.net/. Great stuff!

    As for the bellows, I’ve had some trouble finding plans myself. I imagine comprehensive books on music boxes and singing birds would have a section on bellows construction and/or repair. I have yet to lay hands on such a book, though. You could always take apart a cuckoo clock to see what’s in there! In fact, there are a few pictures of bellows on Wikipedia page for Cuckoo clocks: http://en.wikipedia.org/wiki/Cuckoo_clock.

    One last idea: I wonder if one could use the paper Train Whistle by Rob Ives as a working model? I assume you intend to use thin leather rather than paper, so the construction techniques might be a bit different. Here is his site where you can purchase and download the Train Whistle: http://robives.co/blog/train_whistle_working_sound_model

    If you make any discoveries on this front, let me know!

    All the best,

    -Dug North

  9. Dug North on July 29th, 2011 6:20 pm

    B Templeton,

    Glad you’ve found the site!

    You are talking about “Hide Glue”, right? It is also used in guitar-making and cabinetry, I believe. It seemed like it would be a lot of work to heat the glue while working with it, but then again, I’ve never actually tried it. I have read that one of its great merits is that it softens with the application of heat. That property could make it very, very useful. Thanks for bringing it to our attention!

    Best,

    -Dug North

  10. James Webb on August 2nd, 2011 5:42 pm

    Animal hide glue ! When I was taking shop in high school, Sharon Hill, Pa, in the early 50′s, all we had was animal hide glue. “Titebond” and other glues of today were not developed at this time. The animal glue was kept in electricall heated pots which were turned on when we came into class and turned off when we left.
    The trick with using animal hide glue was maintaining the correct temperature and getting the glue on the joint and clamped quickly !

    Talk about a tough joint ! The other glue that was in common use was casein, a milk by product ! Beleive it or not, egg whites were used as the glue in the making of brown paper drums. Note: “Glue made from the hides of some politicians and most bureacrats will not hold anything together !”

  11. Dug North on August 3rd, 2011 2:50 pm

    Spider,

    Thanks for the additional information on the animal hide glue. It sounds like it would require some extra work and preparation, but it might be worth it in some situations. I still read about woodworkers who swear by it.

    Best,

    -Dug

  12. Andy Rockett on December 20th, 2011 2:05 pm

    Just a quick word on hide glue. I’m a luthier by training and use a number of different glues. But good, old fashioned, hide glue (also known as pearl glue) is still one of the very best.

    It is strong enough to handle joints that are under a lot of tension/stress, yet they can easily be dismantled with fairly moderate heat. It seems like a lot of fuss at first but actually it is very simple to work with. I would recommend it unreservedly.

    Andy

  13. Dug North on May 25th, 2012 8:08 pm

    Thanks for the expert opinion on hide glue! Sounds l like great stuff!

    -Dug

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