Aug 132011

From time to time I receive requests from sideshow performers for me to build them a pump for their own gavage acts. I am not in the business of manufacturing such devices. You will have to find a machinist to fabricate this for you, or else have the tools and skills to do it yourself. I can only describe what I did to build my own. I did not have a lathe, only a drill press. You will almost certainly have better results if you use a lathe instead of a drill press. The dimensions I am giving work for a particular sized barrel; I just happened to pick up an acrylic cylinder as scrap of this size. If you start with a different sized cylinder none of the following dimensions will work, and you will have to modify everything.

I built two pumps back in the early 1990s when I invented this stunt. One was stolen in Copenhagen, and the other remains with me. Both were essentially the same size. I started off with a clear acrylic cylinder 10” in length, 4.485” OD, and 3.975” ID. Clearly this is a 4” ID nominal tube. From there I used a drill press to machine an end cap, again out of clear acrylic, to seal one end. This was the most labor-intensive part of the fabrication, as I had to machine it to a few thousandths of an inch over the ID of the barrel. If you plan to do this yourself, you will need a reliable dial or digital caliper. The end cap on my unit was .675” thick, again made of clear acrylic. When your end cap almost fits into the barrel, use a heat gun to soften the end of the barrel. I chose not to use adhesives to secure the end cap into the barrel, but perhaps one could; I honestly don’t know what would work best. Both of my pumps held liquid under pressure for years with no leakage or malfunctions. You will notice the presence of “crazing” on the end of my barrel; this is a common phenomenon with all many plastics under stress. I suppose one could further secure the end cap with a metal band, or drill screws or pins into the plastic, but I didn’t need to.

From there a brass plumbing fitting was installed in the end cap. This was threaded with pipe thread, so you will need a pipe tap that corresponds to the threads on the fitting you are are using. The fitting needs to dimensionally match the tubing you will be using. Since I used tubing whose ID was 3/16” you will need to choose a metal fitting that will allow that size of tubing to slide over the hose barb. The tubing is elastic, and will expand a bit to fit over a hose barb. I sealed the junction of the threaded hose barb and the acrylic end cap with plumber’s epoxy on the outside of the unit. Black vinyl tape was wrapped around the junction of the hose barb and tubing to provide strain relief. If I were doing this today I would probably use silicone tape instead.

The plunger of the pump is a series of acrylic disks which hold the O-rings in place on a stainless steel rod. The opposite end of the rod is a plastic T-handle. There are two sizes of disks, which are sized to allow just a portion of the O-ring to be exposed to the inner surface of the pump. Again, the dimensions I’m providing are for a barrel whose nominal ID is 4”. The inner disk is 3.550” across and .229” thick. The thickness is nominally ¼”. The larger disk is 3.917” across and the same thickness. I started out using 4 O-rings, but later on found I could get by with just 3. For a 3 O-ring stack you will need 4 large disks and 3 small disks. I chose to tap the centers of these disks to match the threads on the stainless steel rod, which in this case was 3/8” coarse threads.

Believe it or not I was initially unable to find O-rings that fit this application! I fabricated my own using over-sized O-rings and Loctite Prism cyanoacrylate (superglue) #11. The ends must be diagonally tapered at the butt joint. I’m quite confident that anyone building a gavage pump in the 21st century should be able to find 4” OD O-rings commercially. Obviously the thickness of the O-rings needs to match the thickness of the plunger spacer disks. The ones I used were .240” thick.

The stainless steel rod I used was 14” by 3/8”. Both ends were tapped for 3/8” coarse threads. The plunger disk end was tapped 3” and the T-handle end was tapped 2 & ¼” or just a tad longer than the T-handle is thick. I ground a couple of flat spots on the rod to allow the rod to be chucked into a vice while I tapped the rod. This will also allow the use of a crescent wrench to hold the rod while assembling and disassembling the plunger handle. While I used galvanized washers, I wouldn’t recommend it for anyone building one today. I would stick with all stainless steel washers and nuts. On the plunger disk end I used an ordinary stainless steel nut in the middle, with nylon locking nuts at the end. If I was building this today, I would use nylon locking nuts at all four points; two on the plunger end and two on the T-handle end. Use a washer under all four nuts. Besides a crescent wrench, you will need a socket wrench to access and rotate the nut on the outside end of the T-handle.

The T-handle I used was also plastic, in this case a section of polyethylene whose dimensions are 6” by 1& ¾”. The center hole was counter sunk to allow the nuts and washers to fit inside elegantly and to prevent the center rod from biting into the flesh of the gavage assistant. In my case the countersink was a 1” wide bore.

The tubing I used was Tygon R-1000, 5/16” OD and 3/16” ID. The part number I used was AAU00012. As of this writing, this part number is still current. The tubing length I used was 7’. The end was tapered, and a series of cuts were made into the sides near the end to facilitate fluid flow. These cuts were made with a diagonal wire cutter.

I used PAM brand non-stick spray to lubricate the plunger when performing my act.

 Posted by on 08/13/2011 Art, Personal History Comments Off on Building a Pump for the “Tube” Act
Aug 112011

I was skeptical Jan Gregor was going to get us there on time. I heard his vintage alarm clock go off early in the morning; genuine brass bells and a clapper making the ringing noise. By then I saw sunlight coming through my window and thought we might be running late. The Google map directions said it would take an hour and 48 minutes to drive to the Leatherman factory in Portland, and I thought we should have given ourselves more time.

I had booked this tour about two months previously. Leatherman offered it only on Wednesdays, and the available openings closed up fast. Looking at this trip in another way, I’d been waiting for this moment for more than 20 years…

I discovered the Leatherman tool sometime in the late 1980’s. Back then I didn’t read any hype or promotion about the tool, I just bought it because it looked worthwhile. I quickly realized that this tool was a game changer, a tool so incredibly useful that I’ve carried incarnations daily on my belt ever since. The robust elegance of the tool was immediately obvious; it didn’t have twee little thingies like toothpicks that the Swiss Army knife did. I found myself using the needle nosed pliers much more than the knife. The way that the pliers folded into the handle was remarkable, it was robust as a tool yet it folded neatly and compactly into its own handle.

The first incarnation of the Leatherman tool was about 90% perfect. I can think of only three drawbacks. The most important was that the folding tools, especially the knife blade, did not lock into place. The second was that the edges of the handles were not rounded. Gripping the tool was a bit uncomfortable when the pliers were unfolded. The last issue was that the tool was just a tad too small. Over the years Leatherman corrected all these issues, and the current model I carry on my belt is the “Core.” The Core is a full-sized tool, slightly bigger than the original model. Its folding blades lock out, and the handle channel edges are rounded.

As Gregor and I drove towards Portland, I sipped coffee from his Thermos. I tried to mask the anxiety I was developing about being late. The e-mail from Leatherman said that if we weren’t there by 9:55 we were out of luck. Jan tried to reassure me; “this clock is 10 minutes fast, we should be there in plenty of time.” What if a semi truck jackknifed in the road? What if it was transporting watermelons that splattered everywhere? There were too many things that could go wrong; we should have left a half-hour earlier…

We dutifully followed the Google directions, and lo and behold we found the Leatherman plant on time! We actually arrived early, and decided to enjoy a couple of egg McMuffins at the nearby McDonalds. While most corporate tours end in the gift shop, this one started there as well. We looked at all the snazzy new models on display, as well as prototypes that Tim Leatherman created back in the 1970’s. Our tour guide Meei arrived, and we all put on wireless headsets in order to hear her voice over the din of the plant. We all put on protective eyeglasses as well. We entered the floor of the huge plant, which employs several hundred workers. The first stop was a large blanking machine, which punched out tool components from a strip of steel wound on a large roll. We were handed a rough blank and we passed it around. Not surprisingly, every blank that is punched out has a significant burr on one edge, which much be removed.

Then we were led to a polishing-deburring machine. This was a large vibratory tub that contained small ceramic cylinders. A gritty paste was added which we were told was silica. Hundreds of tool components were added, and a large cover was dropped over the vat so that blobs of paste wouldn’t escape. A magnet was later used to separate the blanks from the abrasive. Another station used glass impact bead to create a matte finish on some components.

Other stations along the tour featured both automated and hand-fed punches that folded the flat steel into channeled handles. Random pieces were pulled from the line to visually inspect for cracks that might result. Other blanks were cut by a high power laser beam. Surprising, we were able to watch the laser beam cutting the metal without needing darkened welding goggles. A laser beam was also used in another station to cut through the anodizing on tool handles to create custom engraving.

One station included workers that loaded rough pliers into a conveyer belt. The belt fed a robotic arm that quickly passed the pliers over a rotating abrasive belt. Watching the robot was mesmerizing.

Perhaps not surprisingly, the tools had to be assembled by hand. This was done in U-shaped work stations that allowed 4 or 5 workers at a time. Some handles were held in customized jigs while the fold-out tools and washers were aligned by a drift pin. Most Leatherman tools are held together by rivets, but some are joined by threaded fasteners. Thankfully Loctite is applied to the fastener threads during assembly! Years ago I had purchased various non-Leatherman multitools for comparison. One was a unit that used proprietary threaded fasteners. I happened to be in Europe when one of the threaded fasteners came apart, thus leaving me dead in the water. That episode put the kibosh on my celebration of multitool diversity…

About an hour after we started, our tour came to an end, back in the gift shop were we started. It was by far the most impressive corporate tour I’ve ever been on! I ended up buying a t-shirt and a small “Squirt ES4” which included useful wire stippers. No photographs were allowed of the shop floor, so I’m afraid I wasn’t able to illustrate this blog entry. Later on Jan took me to an excellent pie shop in Portland, and wondered aloud if Leatherman workers might assemble “Frankenstein” tools of their own design…

If you like machines, power tools, robots, steel, and live in the Pacific Northwest, I highly recommend taking this tour!

 Posted by on 08/11/2011 Personal History 2 Responses »