Thursday, June 29, 2017

Kamae Guy; A D.I.Y. Kendo Dummy

This is a design diagram. Not all parts are labeled but you can extrapolate measurements based on scale.
The "1cm = 7 in." notation means that one centimeter on paper represents 7 inches in real scale.
The dummy is designed to clamp a shinai into place and use springs to hold a chudan no kamae while the user practices various waza..
Note the padded sections where the shinai connects; foam knee pads for kote, a garden pad for dou, toolbox liner over old denim jeans for men.
The backside of the KamaeGuy dummy.
Note the wide plywood base used to stabilize the device.
The edge of the base should have edges that are rounded off and sanded smooth the avoid injuring the user's feet.
The screws that are driven up through the base should have slight pilot holes and be counter-sunk to avoid scratching the floor.

Materials and Construction
This dummy can be built with supplies that are typical of construction site scraps; as none of the 2x4s are longer than 4 feet. If you were to buy all of the materials from a home supply store it would cost a little over $100.
The materials consist of the following:
  1. 2x4 lumber
  2. 3/4 inch plywood sheet
  3. 3 inch wood screws 
  4. 7 inch threaded bolt
  5. 4 carriage bolts to tighten the hand clamps
  6. 5 wing nuts
  7. metal washers for the bolt and nut
  8. 10 small eye bolts for the spring and clamp assembly
  9. picture hanger wire (I forget which weight rating the wire was but it was relatively heavy for picture wire)
  10. padding materials; knee pads, garden kneeling pad, toolbox liner, old clothes
  11. duct tape (to hold the padding in place)
  12. springs (from a tractor supply store, you could probably try salvaging springs from a trashed trampoline)
  13. a drill; screw tips, one inch spade bit, drill bits the width of the bolts and wood screws, smaller bits for pilot holes...
  14. pliers
  15. wood clamps (helpful but nut necessary)
  16. a saw (a chop saw works well for most cuts, I used a sabre saw for curved cuts)
  17. sand paper; coarse

The difficult part is setting up the springs. The smaller extension springs (about 6 inches and 8 pounds of pull) connect at the shoulders and pull the shinai left or right to keep it centered.
 You will notice that the springs can hook on to multiple rings; use the inner pair for relaxed springs the react softly and slowly for beginners and the outer rings to increase spring tension for harder faster reactions.
 The larger extension spring (about 10 inches and 15 pounds) on the bottom pulls the "hand" clamp down; be careful when tensioning these springs, this is the hardest part, otherwise the kamae will be off center or the force/reaction will not be realistic.
 I can't actually remember the exact specifications for the springs but it may actually be better for you to experiment and look at different springs. The shoulder springs connect to the shinai clamp with steel picture frame wire, the bottom spring connects directly with no need for wire. If the kamae is off just undo the wire and adjust it length.

The dummy is divided at thigh level to create an artificial spine that reacts realistically to tsuki. This also makes the dummy easier to take apart and move or fit inside of a car.
The two halves are connected with a threaded eye-bolt that is tightened into place with a wingnut which does not require special tools to assemble/disassemble.
Notice the two blocks of wood that were added to the point where the two halves are split. This is to support the dummy as it tends to press forward at the joining point; these support block are not shown on the design diagram as they were a later workaround.

A bolt connects the two halves. The block on the front help stabilize the central post.
The back side could also probably benefit from another set of these blocks.
A large spring that pulls the "hand" clamp downward.
This larger spring gives the dummy much of its reactive speed. 
The secondary set of eye bolts allows users to set the springs in a tenser position.
This adds a higher degree of difficulty where the dummy will have greater speed and strength.
Just stretch the springs out and hook them higher/wider apart.
The carriage bolts should have the rounded side on top with the wing nuts on the bottom so nothing will poke through the top padding.
The padding on the bottom side will be stressed by contacting the wing nuts.
The padding on the bottom is protection in case you bump into the clamp during tsuba-zeriai practice.
Note the way that the picture wire is wrapped and crimped down with pliers so there are no lose ends.

Kamae Guy in use; applications and limitations

This video let's you see the Kamae Guy dummy in use, but the unedited video lacks explaination of what is being shown, so I want to point out specific waza with relevant time points.

  • Men-uchi (0:29) - While the user stikes a small men-uchi the dummy keeps chudan-no-kamae
  • Kote-uchi (1:20) - Note that kote is more difficult with the dummy because A) the wire "arms" are an obstacle which could damage your shinai and B) the padded hand clamp is in line with the shinai instead of being angled to the sides like a human's hands.
  • Dou-uchi (1:25) - Because of the forward mast for the front it is easier to practice dou strikes from the back side (though you do not get the benefit of a partner in kamae). After striking with zanshin you can return to front by using a men or dou strike on the back side.
  • Kote-Men (1:40) - For consecutive strikes, the shinai is going to be moving after the first strike so it will be an obstacle to consider as you move through subsequent  strikes. A stationary dummy is good for ni-dan (two step) waza but more complex waza involving an advancing or retreating partner are harder to emulate.
  • Suriage-Men (2:00) - Shikake waza that involve creating an opening in your opponents kamae are the main practical point of this dummy. The user must develop the power, control and timing for these waza
  • Uchi-otoshi (3:00) - By using enough force and/or applying a good follow through to uchi-otoshi to effectively alter the "partner's" position, you will see that the shinai locks into a resting position.
  • Hayasuburi/ Resting position (3:07) - While the dummy is in the resting position you can practice kihon men from either side. If you are practicing hayasuburi with the dummy in front you should be careful; if the dummy's shinai is moved past the locking point then the wires will uncross and the springs will pull the shinai back to chudan (with initial over correction as the springs return to equilibrium) quickly.
  • Tsuba-zeria / hiki-waza (3:40) - When pressing Kamae Guy into a tsuba-zeria position, the heavy bottom spring will be trying to pull the shinai back down into chudan-no-kamae. For this reason, you will need to practice hiki-waza with knowledge that the dummy's shinai may come down on your head if you are too slow (the shinai will come down faster and harder if the springs are set at higher tension).
  • Tsuki (4:10) - When striking tsuki against Kamae Guy you will note that the head tilts back slightly. 
  • However, as the pivot point where the top connects to the bottom rotates a little this seems to stress the wood so later designs could benefit from support blocks similar to the two on the front in order to prevent the wood from splitting.
  • Tsuki-Men (7:47) - As the head is being pressed back a user could practice following up with men after tsuki as the artificial spine is recoiling.
  • Gyaku-dou (7:26) - From the front, it is difficult to practice dou because of the springs but you can practice hiki-dou.

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