Wednesday, April 4, 2018

DIY Percussion Massage Tool

Simple Black & Decker Compact Saw Conversion - Compare to TheraGun or TimTam


I have had my share of bad bike crashes over the last several years and have some very stubborn soft tissue issues that I have been working on and trying to improve - the joys of getting old! I can remember being sore for a few days after crashing in my 20's, but now I don't quite bounce up as well as I used to. With that in mind I was searching for some tools to help my body heal and function properly when I saw a few online videos of massage tools created from jig saws, reciprocating saws, and even sanders. There are of course dedicated tools like the TheraGun and TimTam that you can purchase but they are expensive and cost anywhere from $400 to several thousand dollars for the top line percussion massagers!

My goal was to build a simple version in my shop and see how well it works. I have now gone through three revisions of this idea and have settled on a much better version for a very low cost of just around $50! The latest version is on the bottom, and the original is on the top.



I settled on using a Black & Decker Compact Saw model LPS7000. This "saw" has similar specs to other products on the market - 2050 strokes per minute, a bearable 70-75 dB sound level, and around 25-30 minutes of run time per charge - all for just $39.99!



I started by modifying some Bosch jig saw blades. I did this by grinding off the teeth, shortening them a little, rounding the ends for safety, and then finally inserting them into  some various rubber balls and even a couple of black rubber stoppers.

This process is pretty easy, and works well. However I found that it could be a little flexy and required glue to keep the blades in place. I had one ball pop off during use and I ended up with a few painful jabs. Luckily I had nicely rounded the end of the blades, however they are narrow and it can still hurt a bit.

I also prefer "frost" or "ice" bouncy balls as I have found that the rough surface on these types of balls work better for direct skin contact and doesn't irritate my skin as much as the smooth rubber balls do. The icy balls are a bit more delicate than a regular super ball and can split easily when just the saw blade is inserted and then used.

My second version was an attempt to eliminate some of the jigsaw blade flex and the various problems of inserting them into rubber parts. I also decided that I wanted to be able to use tips made from additional materials so having a threaded connection for swapping out the tips would make things easier. 

For the threaded arbor I brazed together a shortened jig saw blade to a 1/4" bolt with an added washer to make a nice threaded arbor

I then used some threaded 1/4-20 Rivnuts from my shop and chucked up a ball in my lathe to bore out a hole for the Rivnut. I used some epoxy and glued the Rivnut into the hole I made in the ball. This makes for a very sturdy threaded connection.

I also made a tapered aluminum tip with female 1/4-20 threads on the back to mount to the same arbor.


While this is a better solution and works very well I wanted to try to improve the functionality even more.

On the unmodified saw there is spring loaded blade locking mechanism that is attached to the main drive shaft with 2 small 3mm socket head 
hex screws. 

This blade retention device isn't needed if it will no longer be a "saw"! 

So lets get rid of it!
I removed the blade holder and then shortened the hardened steel drive shaft by cutting it off with an abrasive saw blade. Then I fabricated a aluminum adapter collar to fit the newly shortened drive shaft with mounting holes that matched the blade holder. This new aluminum collar has a 1/4-20 threaded hole to accept a set screw for attaching my new attachments.

Finally, I removed the jigsaw metal guide foot and the plastic frame area around the drive shaft to shorten and lighten the tool. I used a saw to quickly cut it off.

The final version is below. This works much better and is easier to handle and use with more controlled power working on a muscle - there is no more flex or extra movement that occurred when using a modified jig saw blade.


Leave any comments or questions if you want more details on how to do this mod.

Latest Update: I have modified the threaded collar to a M8-1.25 thread so it will now fit some of the EVA foam balls and tapered rubber cones that are sold on several sites including Ebay. 

In addition, one of my original units from 2017 had batteries that didn't seem to last very long, and it ran a little slower than my other units. I decided to update the batteries in the gun. I first tried some standard Li-ion Tenergy 2000mAh batteries I had on hand, but those didn't have the high drain this device needs to work well. Looking at different options for batteries I purchased 2 Samsung INR18650 35E 3500mAh High Drain Batteries for $15 and installed them in the unit. I also changed out the charge board and the charge connector to Micro USB setup and I also added a battery balance/protection PC-board to keep the 2 batteries nice and happy. I like being able to charge it via USB when I travel.

These new batteries have resulted in a super long run time of over 1 hour - which in turn also makes the recharge time pretty long - however, since I typically let it charge overnight anyway, it is still ready to go the next day as needed.