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Recoil Saw bounces its way through wood

The working prototypes of John Zimmerman's recoil panel and hack saws
The working prototypes of John Zimmerman's recoil panel and hack saws
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The working prototypes of John Zimmerman's recoil panel and hack saws
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The working prototypes of John Zimmerman's recoil panel and hack saws
A sketch of a recoil pruning saw
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A sketch of a recoil pruning saw
A sketch of an improved version of the recoil hack saw, with an alternate type of spring
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A sketch of an improved version of the recoil hack saw, with an alternate type of spring
A sketch of an improved version of the recoil hack saw
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A sketch of an improved version of the recoil hack saw
A sketch of a recoil file
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A sketch of a recoil file

Using a hand saw is nobody’s idea of a good time, but one inventor is trying to at least make it a little easier. John Zimmerman, a software developer by trade, has created what he calls the Recoil Saw. Essentially, it’s just a saw – various types of saws, actually – with one or more spring-loaded impact bars attached to the blade. At the end of each stroke, the spring compresses as the bar hits the material being sawed, then releases that energy back into the following return stroke. The idea is that users can pretty much just bounce their way through cutting jobs, as opposed to having to purposefully stop and start between every stroke. Zimmerman, who admits he’s probably not the most unbiased tester, said that he has found it cuts twice as fast as a regular saw.

“I came up the the idea while working on a separate invention that required cutting many pieces off of metal bars, with a hack saw and miter box,” he told Gizmag. “I live in an apartment so using a power saw was not really an option. I wanted a less exhausting way to cut, and the idea for the Recoil Saw came to me after countless tiring cuts.”

Zimmerman has created working prototypes of recoil panel and hack saws, and he has also sketched out designs for a pruning saw and a file. While the bar/spring mechanism on his prototypes might look a little cumbersome, his sketches feature a much more compact mechanism that combines the bar and spring in one simple unit.

A sketch of a recoil pruning saw
A sketch of a recoil pruning saw

“At this time, I am looking to find hand tool manufacturers interested in licensing the recoil saw, which is still patent pending,” he told us. “Of course, to me it seems like a great idea, who wouldn't enjoy spending less time sawing?”

Below are two videos that he shot; one of his recoil hack saw cutting through a board, and one of a regular saw doing the same job. Of course, it's not exactly a scientific testing method as it's impossible to confirm that the same amount of force was being applied to both saws, but it’s still an interesting comparison.

Via InventorSpot

13 comments
Frederick Welsh
You guys better stick to electronics and leave this sort of thing to a first year engineering student, an apprentice carpenter or Bob Vila on a slow day. What in the world is this guy doing cutting wood with a hack saw? Has he found some wood cutting blade somewhere? These are for metal. The chips he is making sure look like an abused hacksaw to me. A decent back saw would have this done in half the time. The first year engineering student might notice that this is a version of a perpetual motion machine. Somehow, we will get more force out of that recoil mechanism than we put in and that will make everything faster. Ain\'t gonna work that way. The inventor should run a race with a regular hand saw and your editor should learn more about woodworking.
Bill Bennett
ok, why use a fine tooth metal cutting blade to cut wood? you still have to load the spring, why not just use a wood saw, in any case, you will expend energy to load the spring, what is the return of energy?
Michael Crumpton
This actually a brilliant idea. A lot of the energy in sawing is used bringing the saw to a stop in order to reverse direction, and of course that energy is usually wasted. In this invention that energy is stored and then released to help the stroke reverse direction. I suspect this might actually work.
Joseph Manske
I won't bother repeating the issues with using a hack saw to cut wood. It's pretty clear that this person doesn't do a lot of hand sawing. Any energy that could even conceivably be saved through these springs (which still need to be compressed, wasting energy) is wasted by creating a shorter cutting stroke that becomes less efficient when compressing the springs. "Using a hand saw is nobody's idea of a good time"; It is to me. I use hand tools almost exclusively in my projects.
Fred Conwell
Run a test simultaneously to compare with & without. He is using the energy wasted on the back-stroke to impel the saw forward, conserving that energy. Great idea. Five years from now all handsaws will have a similar device.
Paul Anthony
I think this may be a working advantage. If you ever ran across a trampoline you would probably feel the same effect, the bounce back propels you to the next step, much like the stroke would be propelled back into the opposite direction. Perhaps a physicist could calculate the momentum and change thereof. I think this guy should set up a test fixture, one with a set downward pressure and set force for the forward and return stroke using the full stroke for a standard and his modified saw. I have just such a device already set up if he would like to use it. I am in San Diego California. You can go to this site to see the description and there is a link to the circuit schematic. http://members.cox.net/paulvild/RecipricatingTestCircuit.shtml Also, he may want to use a metalic substance as a test subject. This is so that the woodworkers wont get distracted by the selection of the blade.
jjsmail
Well D\'UH! Of course it cuts faster, as the bumpers allow the user to use the entire blade without slowing down at the ends to avoid hitting the frame. Anyone that has ever used a saw knows that you use primarily the center section of the blade to avoid hitting the handle or the saw sliding out of the cut. These shock absorber/limiters allow use of the entire blade. Twice the cutting length = twice the speed. Not rocket science.
jimbo92107
40 seconds versus 61 seconds. The faster saw wins the race. Doesn\'t matter what kind of saw he was using. Rebound from the springs allows the blade to travel faster across the piece, reducing the time it takes to finish the cut. This is an excellent innovation. If you have to use hand saws, this is the way.
Matt Rings
LOVE IT! Three thousand years of saw technology leaps forward in the year 2010. Hope he makes millions, as he makes the rest of us more efficienct, without having to changes sawing arms in the middle of a long cutting task. Three Cheers! Doc R
Deepak Parida
amazingly simple!!!! wow!