Redemption! - A.K.A. Rotary Tumbler Part II

completed tumbler - success!

A few months ago I posted about a failed attempt to make a rotary tumbler.  Dejected, I left the useless pile of parts where they lay and moved on to other projects.  This is part two of the saga where I build one that actually works.

One day in a desperate attempt to find more room in my garage, I decided to throw out a bunch of stuff.  One thing on the chopping block was a VITAMASTER belt massager.  Like a lot of my stuff...cool but ultimately useless.

vitamaster belt massager

I picked it up at a flea market years ago because I thought it was retro cool.  It was fun in college watching curious girls jiggle on it, but now it's just one more thing to draw blood from my four year old.  So I cued it up for the trash but soon had second thoughts.  "Heavy gauge steel pipe, I could use that.  Same with the base.  Cool enclosure I could repurpose.  Electric motor..."  Hey, wait a minute...  I opened it up and what was inside but a 1050 rpm, 1/10 HP electric motor.  Maybe this was just what I needed to salvage my failed rock tumbler.  Just a bit more powerful than the 1/150 HP of the original motor and three times more powerful than the motor in the Thumler model B that served as the inspiration for this project.  I did some quick calculations to check the final drum speed with this motor and realized that it just might work.

can I fit this...

...into this?

Go back to my original post to see the construction of the base.  Here are my revised gearing calculations with the new motor.  My drum is about 6 27/32" in diameter.  I want it to spin at 40 rpm.  My roller shafts are 0.62" in diameter (at the rubber bushings).

6.84375" (40 rpm) = 0.62" (X rpm)

Solving for X tells me I need my rollers to spin at 441.5 rpm.  This motor is rated at 1050 rpm.  If I divide my roller rpm by my motor rpm I find I need a reduction ration of 0.42.  Last time I used a 25 tooth gear.  I knew I needed a larger motor gear this time to compensate for the slower motor speed.  Luckily I had a 30 tooth gear.  Dividing the 30 tooth motor gear by the 72 tooth roller gear gives a reduction ratio of 0.42, just what I was looking for.  Check the math for the expected drum speed:

30 teeth (1050 rpm) = 72 teeth (X rpm)

= 437.5 rpm shaft speed

0.62" (437.5 rpm) = 6.84375" (X rpm)

= 39.6 rpm drum speed

Close enough!  Next I removed the motor from the massager and did a quick check to be sure it would fit into the tumbler base.  It looked good so I lined everything up, marked for the screw holes, and drilled.  Then I bored out the motor gear and fit it on the motor shaft with a set screw.  Luckily the drive belt still fit.  Finally I soldered the wires to the switch and power cord.

new motor in place

I filled the drum with 5 pounds of stainless pins and as much water as it could hold and placed it on the tumbler.  Nervously I flipped the switch...The tumbler sprang to life spinning the drum without any signs of hesitation.  Looks like I had the power I needed.  But...the stainless pins sat lifeless in the bottom of the drum as it spun around.  My rotary tumbler was all rotary and no tumble!  Obviously it wasn't going to polish anything that way.  Looking back at the original design, I realized that the Thumler drum is hexagonal.  The sides of the hexagon help to flip the contents as the drum spins.  My round drum simply spun around the contents.  I needed something in the drum to agitate everything.

I went to Home Depot and walked the isles looking for something I could add into the jar to act as flippers.  I found some plastic channel meant to go between pieces of wall paneling.  There was an extra piece on the channel that I didn't need so I scored it with a utility knife and snapped it off.

original channel

trimmed

I cut the channel down to size and made a few relief cuts so that it would conform to the shape of the jar.  I decided to secure it to the jar with pop rivets.  I melted holes through the jar and channel with an old soldering iron.  Then I put a layer of silicone caulk on the channel to prevent leaks before riveting it in place.  I backed up the rivets with washers to keep from pulling the rivets through the soft plastic.

channel in place

inside view

Another problem that I had with the jar was a slight leak around the lid of the jar.  I tried several solutions to seal it, even including molding my own silicone lid liner.  It still leaked.  Eventually I came across a foam mat that I had laying around.  I cut it to size, placed it inside the lid, and voila!  No more leaks.  The final problem was that the rollers slipped on the jar if they got even a little wet.  I added some 3M grip tape around the outside of the jar; not very elegant but it worked.

seal for lid of jar

Finally a rotary tumbler that works!  Now to find out if it actually polishes anything...  In a previous post I tested a Harbor Freight ultrasonic cleaner for cleaning dirty brass rifle and pistol cases.  It worked pretty well on recently fired brass that wasn't too dirty.  But it came up a little short for cleaning really grungy cases.  I grabbed a handful of very dirty .45 ACP pistol cases and some fired and tarnished military surplus .30-06 and threw them in.  I added two tablespoons of Dawn dish detergent, 1/4 teaspoon of Lemi Shine, and one gallon of water.  Then I ran the tumbler for four hours.

Oooooh, shiny!
(52 rifle and 86 pistol cases if you were wondering)

Same batch of cases, cleaned ones on top (duh).

Doesn't get much dirtier than this.  No problem for my tumbler.

even the primer pockets got cleaned

inside is a little discolored but there is absolutely no powder residue

Wow!  The results were surprising.  The cases were not only clean inside and out, but shiny too.  Primer pockets, deep inside the .30-06 cases...spotless.  It even removed the red marking paint that was on the bottom of the .45 cases that the ultrasonic cleaning couldn't budge.  If it can clean these cases, it should be able to handle anything.  This will definitely be how I clean my brass from now on.  Well it was a long road, but I am glad I finally got this project finished.  My tumbler seems to work every bit as well as the Thumler and best of all it was built entirely from scrap; didn't cost me a penny.

Hammerli 850 Trigger Upgrade

Original plastic trigger on left, new metal trigger on right.

Here is a project I did back in June 2008.  One of my favorite airguns is the Hammerli 850 AirMagnum.  It is a .22 caliber CO2 powered bolt action air rifle.  It holds 8 pellets in a rotary clip, has good power, and it relatively accurate.  Best of all, it is powered by an Airsource cylinder and can get around 200 shots per cylinder.

Hammerli 850 AirMagnum

While plastic stocks do not bother me, plastic triggers do.  I don't know why, it just makes the whole gun feel cheap.  So I decided to make a metal replacement trigger.  Not much to show for the build pictures. I just started with a piece of metal that was the right thickness, scribed the outline of the original trigger on it, and carefully ground, cut, milled, and filed, away the excess material down to the scribe marks.  I finished it up by polishing it with some emery paper followed by the buffing wheel on my Dremel.

left side

right side

front view (notice narrower profile of new trigger)

after bluing

I narrowed the trigger a bit to my liking.  After sanding and polishing I blued the trigger with some Berchwood Casey Perma Blue.  The new trigger works great and feels even better.

3D Printed Key

OEM San Jamar Key

In my office there is a paper towel dispenser.  The key to open the dispenser was lost long ago.  So every time I want to open it, I have to jam my office key through the hole and pry until the case opens up.  Each time I risk breaking my key and it damages the dispenser.  Time to make a replacement key!  I figured this would make a good opportunity for another stab at CAD design and 3D printing.

Paper towel dispenser.

Close-up of the keyhole.

So I took a few "careful" measurements of the key hole and drew up a rough sketch.

My precision blueprints.

I spent about an hour in 123D Beta drawing up a new key.

CAD image

Then I uploaded the design to Shapeways and ordered a key.

The finished key.

Crap!!!  After I drew the outline of the key, I extruded the image in the wrong direction; creating the zig-zag portion upside down.  The key didn't fit.  Well, I really didn't feel like paying for another 3D print.  So instead I just cut off the bottom portion of the key and epoxied it back on in the right direction with some JB Weld.

The repaired key.

Hey, it works!

View of key from inside box.  Not a bad fit.

The corrected CAD file.

I fixed the CAD file and uploaded it.  Just in case someone else needs a replacement key for their San Jamar paper towel dispenser, you can purchase this key directly from Shapeways.  If you have your own 3D printer you can get the file from Thingiverse and print your own.

High Standard Thumb Saver

High Standard Thumb Saver

About a month ago I made a magazine catch for my High Standard Supermatic Trophy pistol by hand.  It worked well enough that I thought other High Standard owners might be interested in it.  So I decided to look into having my Thumb Saver mass produced.

I drew up a CAD model and submitted it to a plastics manufacturer to see about having the part injection molded.  While the cost per part was very low, the set up costs for making the dies was prohibitive.  I didn't think I could sell enough to ever recoup my expenses.  Plan B was to have the part 3D printed.  The cost per part is higher, but there are no set up costs.

So, I optimized the CAD model for 3D printing and ordered a sample.  I redesigned the part a few times to increase strength and minimize volume.  A few tweaks and a few samples later, I had what I was looking for.

Too small!

Note to self: check measurements carefully.  My CAD file was in centimeters.  The printing service defaulted to millimeters.  The first prototypes were just a little too small.

too weak

I had to find the right printing process with the right material.  Some plastics are too weak for anything beyond a prototype.

Too thin.

The next version was better but I felt a few areas were too thin.  So I beefed them up for greater strength.  I also removed material where it wasn't needed.

just right

rear view

The final part is printed in nylon; strong but flexible.  I think it should provide years of reliable service.  I use it  every time I shoot; it makes loading so much easier and faster.  This one is designed for the military grip models.  If there is enough interest, I may make one for the slant grip models as well.  If you would like one for your High Standard, the Thumb Saver can be ordered here.

Custom Ruger 10/22 Part IV - Troubleshooting

This was supposed to be a 5 shot group!

I finally made it out to the range to test out the custom Ruger 10/22 I built.  I just couldn't wait to see how accurate the rifle was.  Unfortunately, I never got to test the accuracy.  As soon as I started shooting, I experienced an unusually high rate of failure to fire (FTF) malfunctions.  A failure to fire is when a round is loaded into the chamber properly, the hammer drops, but the round doesn't go off.  Now it isn't unusual to get a few bad .22 rounds in a batch that won't fire, especially with bulk ammo.  But my FTF rate was about 44%, regardless of the brand of ammo!  Obviously something else was wrong.

I inspected some of the FTF rounds and noticed that the primer strike looked light.  In fact on some of the cases, it looked like the firing pin just barely nicked the outer rim of the case.  Since each round was feeding perfectly, and the bolt always closed completely, I thought the firing pin might be the problem.

I used the depth gauge on my digital calipers to measure the firing pin protrusion.  It measured 0.018".  It should be about 0.035".  The bottom of the pin also seemed to be rounded over, almost like it had been dropped or dry fired a lot.  Maybe I found the problem?  So I ordered a custom firing pin from KIDD Innovative Design.  It was specifically designed to address inconsistent ignition.

Stock Ruger firing pin in front of KIDD firing pin.  Notice the KIDD pin is longer.

The new pin was beautiful.  Well as beautiful as a piece of metal can be.  The extra quality of the KIDD pin  is plainly evident.  Installation was very easy, took just a few minutes.  With the new pin in, I measured the firing pin protrusion to be 0.036".  Much better.

After I reassembled the rifle, I loaded up a few plastic snap caps and pulled the trigger.  Rather than the rounded little dimples the original firing pin left, the new pin left a long, deep, well defined dent.  As long as it doesn't pierce the case rim, I think we're in business.  Only one thing left to do; get out to the range and shoot!

3 strikes from the old firing pin and one from the new pin.
I'll give you one guess which dent is from the new pin!

At the range I tested out some CCI Standard Velocity, CCI AR Tactical bulk, and Remington Thunderbolt bulk.  Without any regard for accuracy I just squeezed off 10 rounds in rapid succession, swapped mags, and continued until I had fired 100 rounds.

Here are the results.
CCI Standard Velocity: 10 shots, zero FTF
CCI AR Tactical: 30 shots, 2 FTF
Remington Thunderbolt: 60 shots, 3 FTF

Note that all FTFs were with bulk ammo.  Each FTF round fired when I loaded it back in the magazine and tried to reshoot it.  So, I went from a 44% FTF rate to a 5% FTF rate.  Much better and par for the course I suspect with bulk ammo.  I am guessing higher quality ammo will function 100%.  Problem solved.  Now to test for accuracy.

At the range.

High Standard Speed Loader

High Standard speed loader

Recently I spent a day at the shooting range with my wife.  She had a fun time shooting a couple hundred rounds through a .22 High Standard Supermatic Trophy pistol.  But we probably spent more time reloading the magazines than shooting.  And holding that little follower button down on the magazine became uncomfortable pretty quickly.

Volquartsen MagLatch for Ruger MK pistols

A day or two later I came across this MagLatch for the Ruger MK pistols from Volquartsen.  Since the Ruger magazine is similar to the High Standard, I figured I could make one to fit the High Standard magazines.  Of course I could have machined one out of nylon but I have been looking for projects for a supply of ShapeLock that I have.  This seemed like a good one.

ShapeLock

ShapeLock is an ultra-high molecular weight low temperature thermoplastic.  What that means is when it gets hot it becomes very pliable, almost like clay.  But when it cools and sets it is a very hard plastic, almost like high density polyethylene (i.e. plastic cutting boards).  It is great for quickly making prototypes, molds, tooling, custom parts, joints, mounts, etc.

Disassembled the magazine

I started by disassembling and cleaning the magazine.  Then I reassembled the magazine without the spring.  I didn't want the spring tension to work against the ShapeLock as it set.  I wedged a little piece of plastic in between the magazine and follower to hold the follower in place.

Magazine without spring.

Everything ready

Next, I nuked a mug of water taking it up to about 170 degrees F.  You are supposed to have the water at 150 degrees, but the water cools pretty quickly when you add the ShapeLock.  A small hot plate kept the temperature up while I worked.  The ShapeLock was placed in a small strainer and submerged in the mug.  In hindsight, the mug was too small for the amount of ShapeLock I was using.  I had to keep kneading and re-submerging the ShapeLock to get it thoroughly heated.  If I were doing it over, I would have used a much larger bowl of water.

Warm ShapeLock wrapped around magazine

Once it was heated, I kneaded it into a disc about 1 cm thick.  Then I wrapped the disc around the magazine and squished it in place.  I held it for about a minute until it started to set.  Then I let it cool for about 10 minutes.  By then it was holding it's shape, but it was still easy to cut.  So I started removing excess material with a utility knife.  Once it got harder to cut I used a scalpel that I heated with a torch to melt through the ShapeLock as I cut.  Be sure to save all of the trimmings.  They can be reused later.  After a bit of cutting and shaping, I installed it on the magazine.  It fit!  Looks like this thing might work after all.

Rough cutting

Test fit.  It works!

The final step was making this unsightly hunk of plastic look presentable.  I cut it down to size on my scroll saw.  I used a relatively course wood blade at the slowest speed.  Then I smoothed it up on the belt sander.  It sands OK if you keep the pressure low and let it cool every so often.  I removed any last bits with a high speed cutter in my Dremel tool.

It looks much better in person than it does in these pictures.  More important, it works perfectly!  Slide it on, lock it in place, and just drop your ammo in.  No more sore thumbs!

Update:  I have made a commercial version of this.  It is available here.  Full details in this blog post.