Cool Vest

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COOL VEST

by Tom Campbell

Overview:

This build it yourself design cooling vest is to reduce heat stress and fatigue on observers during the hottest of the summer nights when both the air temperature and dew point temperatures are very high. Particularly when observing in parts of the USA, Australia and other parts of the world when hot nights at the telescope can feel very oppressive. The vest cost me just over $100.00 in materials and a total of 20 hours of my personal labor. Commercial water cooled vests cost from $400.00 and up.
 

Figure 1.
Overview of the cooling vest system showing the 20 quart insulated cooler, the two 3/8" I.D.
umbilical hoses hooked up to the vest and the AC power cord.
 


The open polyester (or nylon) mesh vest has six water tubes fastened to it carrying circulating ice water to absorb excess body heat keeping the individual wearing it comfortable during hot and humid nights. The 20 quart insulated cooler is filled with some 16 pounds of crushed ice and small amount of water. The heat from the return water is absorbed by the melting ice, cold water is picked up by its small pump and circulated back to the vest. 16 pounds of crushed ice last about 4 hours before the melt water has to be dumped and the cooler recharged with more crushed ice.

The pump is a small sealed A/C powered magnetic drive aquarium pump, only 9 watts and maximum flow rated at 140 gallons per hour. The actual measured flow rate of this pump is 37.5 gallons per hour due to the flow rate restriction of the small tubing. The pump actually draws less than 9 watts due to the flow rate being lower than its designed flow rate and the physics involved with its centrifugal pump impeller.

Figure 2.
Inside view of ice/water container showing the pump, the chill water supply hose and the water
return hose.


Power for the pump is from either a household AC power source or from a power inverter while in the field. In either case a long light gauge extension cord allows the ice bucket to be relocated and the umbilical hoses allow a 12 foot diameter circle of observer mobility before the cooler has to be picked up and relocated.
 

 

Background:

This cooling vest is the final product after a year of experimenting with two types of pumps and two types of tubing material. The vest has three cooling partitions each with their own separate water tubing. That is the left front, the back and the right panel. The original design had a single 3/16" I.D. silicone tube run for each of the three panels, but it didn't quite provide enough cooling for me. I then tried using 5/16" I.D. latex gum rubber tubing (surgical tubing) that did increase the total cooling water flow rate. But it had larger wall thickness, natural rubber is a better thermal insulator and the net cooling effect was less than the original 3/16" O.D. silicone rubber tubing. I tried using a 12 volt automotive windshield washer pump which had more pressure but it had a noisy sound as well as a serious RFI problem not to mention more power consumption. Besides this type of pump was never intended for continuous use and its long term reliability was questionable. The 9 watt AC powered submersible magnetic drive aquarium pump proved to be quietest sound as well as no RFI emissions and is designed to run indefinitely. My final solution was to double the number of silicone rubber tubes on the vest since that material conducts heat better than natural rubber does. Now there are a set of two tubing runs on each of the three vest panels. The second set of tubing runs between the tubes of the first set in an "interlaced pattern". This increased the vest water flow rate from 18.75 GPH to 37.5 GPH which is adequate for this cooling vest system.
 

 

Construction:

1) Making the vest: The open mesh material (see parts list at end of article) should have at least 1/8" holes and be non stretchable. This is the key framework for the support of the silicone rubber tubing that will be fastened to it using 4" plastic cable ties. If you don't have anyone in your family, relatives, friends, etc. who knows how to sew you may have to go to a professional tailor to have it made. If you can have it cut to fit your body it will feel cooler. However I recommend it fit a little loose and use adjustable straps sewn into it so you can snug it up as you are putting it on. After the tubes are fastened to it they become an integral part of the structure of the vest making it feel like a heavy winter vest especially when its tubes are primed with water.

2) After the basic open mesh vest is made I recommend constructing the water manifold assembly and attach it to the vest before installing the cooling tubing to the vest. This gives you a start and stop point and barbs to anchor each of the 3/16" tubing and to reduce waste trimmings of the tubes later. (The first experiment I ran the tubing putting the manifold on last and had about an excess foot on each tube to trim off---a costly waste).

3) Constructing the 4 water manifold sub assemblies: Aside from the sewing of the vest material itself, this is the most time consuming. It is not hard.....just have a lot of patience. There are no commercially off the shelf inline 3/8" barb to four 3/16" barb manifolds that I know of. So each of these four manifolds has to be hand made. But once these sub assemblies are finished the remainder of the cooling vest construction is easy.
A). For each of the four inline water manifolds (refer to the parts list) you will need the following:
1 3/8" hose barb to 1/2" threaded male threaded adapter
1 PVC 1/2" threaded female to female coupler
4 3/16" to 3/16" barb hose splicer
1 roll of 1/2" Teflon pipe sealing tape
1 tube of two part quick set (5 minute) epoxy glue
1 tube of two part extended time (60 minutes) epoxy glue
 

Figure A


B). Manifold assembly holding fixture for tack gluing the four 1/16" hose barbs to the PVC pipe coupler:
Take a 1/8" steel or brass rod and cut it into four 10 to 12 inch segments. File to deburr cut rod ends.
Pass the four rods through the 1/2" PVC coupler.

Figure B


Using two wooden blocks drill four 1/8" holes in a square pattern. Determine and measure beforehand the
hole spacing so that the rods will have a slight bend for as they pass through the PVC adapter putting
some force between the rods and the inside wall of the PVC pipe fitting.
Remove one of the blocks and slide a 3/16" hose barb on each of the four rods moving them all the way to
the other wood block.
Insert the four rods back into the wood block that you had previously removed.
Slide the four 3/16" hose barb splicers down the rods and into the PVC coupler as shown in Figure B above.
The hose barbs will firmly be held in place by the spring action of the slightly bent rods.
Use your hand to align the axis of the PVC coupler with the axis of the four hose barbs. Make sure there
is equal spacing of the hose barbs with room enough for pushing on each of the four 3/16" hoses.
C). Mix a little of the two part 5 minute epoxy glue and apply a dab on each side of all four hose barbs
between each barb and the inside wall of the PVC pipe adapter. Rotate the fixture as needed to for
gluing access, but hold the blocks with both hands as you rotate keeping the fixture from shifting.
Allow at least 1 1/2 hours for the glue to become firm before removing the wood blocks and pulling the
metal rods out. Once the fixture is removed you will find all 4 hose barbs firmly tack glued in place.
 

Figure C


D). Mix some more 5 minute epoxy glue and apply with a Q tip between the barbs building a "glue bridge"
across the end of the PVC adapter. This is a multistep process to build a glue bridge that requires
holding and rotating the manifold in a horizontal position to allow the glue to flow toward the
center of the opening leaving a smaller and smaller hole until it closes. Allow 10 to 15 minutes
between each glue application until the "glue bridge" is complete.

Figure D


E). Mix a small batch of extended time epoxy glue (60 minute epoxy) and using a plastic syringe inserted
into the opposite end of the PVC coupler place about one cc of this glue between the 4 hose barbs
and allow it to flow outward surrounding each hose barb forming a good seal between the barbs and
the threaded wall of the pipe coupler. This slower setting epoxy flows smoother, makes a better seal
when it sets and provides great mechanical stability for each of the hose barbs that is needed when
hoses are pushed on and off of them.

Figure E


F). Use the end of a match stick to tamp the uncured epoxy glue until it has completely flowed around the
outside of the hose barbs and spread to the ID of the PVC coupler. Use care not to cover the ends of
the hose barbs with the uncured epoxy. Push an 1/8" metal rod through each of the hose barbs to make
sure the ends and inside of them are cleared of glue before it sets.

Figure F


G). Lastly screw the 3/8" to 1/2" mpt adapter into the other end of the PVC adapter.

Figure G


H). Repeat steps A through E until all four inline water manifolds are completed.
 


4) Assembling the vest water manifold system (Refer to Figure 6 for assembly guidance):
A). The following parts are used for this step:
The four inline manifold sub assemblies.
Cut one sheet of 1/16" polyethylene plastic to a 3" X 5" rectangular shape. (eg., a flat piece from the
lid of a 5 gallon dog food container).
Four short sections of 3/8" ID X 5/8" OD silicone rubber tubing.
Two short sections of 3/8" ID X 1/2" OD silicone rubber tubing.
Two polypropylene 3/8" "Y" barbed tubing adapters.
One tubing pinch valve.
Two 3/8" barbed tubing coupler inserts.
B). Drill two 1/8" holes in each corner of the 3" X 5" plastic manifold frame.

Figure 6.
Overview of the vest showing the custom made in line manifolds, the two "Y" splitters, the two
quick disconnects and the tubing pinch valve that allows the user to control the chill water flow.


C). Use four 8" long tie wraps to fasten together two pairs of the inline manifolds.
D). Locate and drill four 1/4" holes in the 3" X 5" plastic frame used for securing the manifold pairs.
E). Use two 8" long tie wraps to fasten the two manifold pairs to the plastic frame using the holes
drilled in step D.
F). Locate the small hose barbs about 3" in front of the seam of the left front/rear vest panels, near the
bottom of the vest, as shown.
G). Use four 4" long tie wraps to secure the plastic manifold frame to the vest by passing each tie wrap
through one of the small corner holes, through the vest mesh and out through the second corner hole.
H). Hold off with the large "Y" tubing/valve/quick disconnect inserts until the vest tubing is installed.

5). Routing and fastening the 3/16" ID silicone rubber tubing sections on the vest:
A). It is important to feed this tubing by turning the entire bulk roll as you need it
rather than pulling off the tubing while the roll is laying flat. This prevents twisting of the
tubing allowing it to lay down flat and close to the vest prior to fastening with the small
tie wraps. (note: Disregard the excess and open tube ends as you will be starting and terminating
the tube ends on the manifold ports. This picture was my first time at routing the tubing.)

Figure 3.
Showing the 3/16" I.D. silicone rubber tubing supply roll as it is being fastened to the vest with
small cable tie wraps.


B). The top two inline manifolds are the chill water supply (8 ports) and the bottom two inline manifolds
are for the return water (8 ports).
C). The vest is defined as having 3 sections (left front, back and left rear). The boundaries are NOT
the vertical seams of the vest. Instead each boundary is an imaginary line from the rear of each
arm opening straight down to bottom hem of the vest.
D). Each vest tube is approximately 10 to 12 feet long, the tubes run vertically up and down, spaced about
3 inches apart and the bend radii is roughly 1.5" at the top and bottom. The vest tube bend radii
can be as tight as one inch but any tighter bend may result in a kink. Also there are two tubes for
each of the three sections. The second set of tubes are placed between (interlaced) for a total of
six vest tubes spaced at about 1 1/2 inch intervals.

Figure 9.
Rear view of cooling vest showing me wearing a water cooled headband with the system.


E). Starting with the left front section take the 100 foot roll of tubing, push the open end of the tube
onto one of the water supply manifold ports (aka hose barbs), make a slow sweeping bend and route it
upward along the left vest boundary. Use some temporary 4" tie wraps to hold the tube in place as
you route it on the vest. At the top of the vest shoulder, curve the tube toward the neck of the vest
and then route it down just inside the front opening of the vest. Next make the vertical up and down
runs until the tube gets near the left vest boundary. The tube should be running downward before
making a final sweeping turn toward one of the water return ports. Cut the tube and plug the open
end of this first vest tube onto one of the water return ports. Don't cut the tubes too short or
you will have to remove it and start over.

Figure 4.
Showing some of the routing paths of the tubing.


F). Right front vest tube routing: Connect the bulk tubing to another water supply port, run the tube back
to the left vest boundary and upward to the shoulder of the vest. Route this tube behind the neck
opening, over the right shoulder close to the neck opening and down along the inside opening of the
right vest section. Make the vertical up and down tube runs with the last vertical running downward
along the right vest boundary. Curve the tube, run it across near the bottom rear of the vest ending
at the water return manifolds. Cut the tube and push it onto one of the water return ports.
G). The back of the vest tube routing: Connect the bulk tube to one of the supply ports, route it up the
left vest boundary, make vertical tube runs up and down the vest back with the final vertical running
down along the right vest boundary, across the bottom back of the vest, cut the tube and push the end
of this tube onto one of the water return ports.

Figure 5.
A clearer picture of how the tubing is routed on the front panels.


H). Minimize the tubing crossovers to the manifold ports by swapping tubing connections.
I). Repeat steps E through H until you have the second set of vest tubes installed. There are a total of
6 tubes on the vest connected to 6 water supply ports and their other ends connected to 6 water return
ports. Trim the excess from the tie wraps and rotate to keep them from snagging the outer garment.
J). The extra two water supply and two water return ports are for connecting a water cooled head band and
a water cooled neck collar. I haven't detailed these two items as they are still under development.
So if these extra two water supply/return ports are not used, cap them with something. DO NOT run
short sections of tubing between the spare supply and return ports just to prevent water spillage.
The latter creates cold water "shunts" reducing the cooling efficiency of the vest.
K). Build the two 3/8" ID tubing "y"s, connect to the four 3/8" barbs, use a short piece of 1/16" wall
thickness (3/8" ID X 1/2" OD) silicone tubing where the needle pinch valve is and mount the two
barbed quick disconnect inserts. Use tie wraps to secure the "y"s to the vest.

6) The "ice bucket" modifications.
A). Drill two 5/8" holes through the upper side of the cooler.
B). Drill a 1/4" hole through the upper side of the cooler.
C). Cut off the stock plug of the pump power cord and push the cord through the 1/4" hole from the inside.
Position the pump in the corner as shown.
D). Push the ends of the two 5/8" OD (3/8" ID) hoses through their holes, connect one to the pump and
route the water return hose as shown. Use 3/4" wire clamps, glued to the inside wall with two part
plastic epoxy glue to hold the return hose in position.

Figure 2.
Inside view of ice/water container showing the pump, the chill water supply hose and the water
return hose.


E). Glue a couple of 3/4" wire clamps on the bottom to keep the pump from shifting.
F). Glue smaller wire clamps on the inside wall to dress the pump motor power cord.
G). Use plastic tie wraps on both hoses and the power cord on the inside and outside walls for a strain
relief. The tie wraps should be as close as possible to the cooler wall, tight enough so you cannot
rotate them on the hoses and power cord yet not too tight that would restrict water flow.
H). Apply plastic epoxy glue around the three holes, both inside and outside, completely covering the tie
wraps and the rim of the holes to form a water proof seal. Once the plastic epoxy glue sets the
silicone tubing cannot be rotated within their holes. (no glue that I know of will adhere directly
to silicone rubber).
I). Mount a 3 prong AC power plug on the end of the pump power cord.
K). Insulated sleeves for the umbilical water lines consist of an inner layer of 1/8" polyester material
and an outer layer of nylon parachute material. The trick is sewing the seam with the insulating
material on the outside and then turning the sleeve inside out to hide the seam and for the
parachute material to be on the outside.


 

Operating instructions:

1) Priming the system: Before wearing the vest hook its tubing quick disconnect inserts to the cooler's two umbilical mating hose couplers. The water supply connectors are marked with red dots. Fill the cooler with crushed ice and only enough water to cover the intake of the pump. Make sure the vest, the umbilical hoses and the ice bucket are nearly the same level. Power on the pump and if you see air bubbles in the water supply line add a little more water to cover the pump and the supply line air bubbles disappear. Now look at all of the smaller tubes on the vest and initially you may notice some air bubbles moving in them. Keep the pump running until you no longer see bubbles in any of the vest tubing and touch each tube to see if they are all cool. After this system priming procedure is completed a siphon is established allowing the water flow rate to be the same regardless if the ice bucket is higher or lower than the vest. Detach the water umbilical lines using their non leak disconnects now that the system water prime has been established.

2) Donning the vest: First a snug fitting stretch polyester tee shirt is recommended underneath the vest to keep the cold tubes from direct contact with the body. Next you put on the cooling vest and tighten the 3 front straps so it fits snugly on your body (link to figure 7). Next pass the umbilical tubes through the 3 large tie wrap loops on the bottom right of the vest and mate the quick disconnect couplers (Link to figure 8). Power on the pump if it is not already running. If you are using the optional head and neck coolers put them on making sure their tubes have enough slack for mobility of the neck and head. If not using the optional head or neck cooler (link to Figure 9) their water supply and return port barbs must be capped. Worn over the cooling vest is an insulated and water proof winter vest (link to figure 10), or a winter jacket with its sleeves cutoff. This outer garment improves the efficiency of the cooling system by preventing ambient heat from being absorbed by the tubes as well as reducing the absorption of the heat of water condensation on the tubes.

3) Manual flow rate control: If after a while of sitting still and you begin to feel chilled simply turn the needle pinch control valve (link to Figure 8) to reduce the water flow rate to your desired level of cooling comfort. This takes several minutes before any difference is felt. If you want quicker action turn off the pump or disconnect one of the lines for a few minutes after making a needle valve adjustment and then start the water circulating again.

4) Mobility: There is about a 12 foot diameter circle, with the ice bucket in the center, that the cooling
umbilical tubes will allow. To move further simply pickup the cooler with one hand and you can move as far as the extension cord will allow.
 

Figure 7.
Me putting on the vest and tightening the closing straps. Also shown is a view of the non leak
hose quick disconnect coupler inserts.


5) Temporarily disconnect the water umbilical: If you need both hands free and you need to walk further to carry something from the car to the scope. The vest will still feel cool for 3 to 5 minutes before it begins to feel warm. Reconnect the water and it only takes a few seconds to cool down again. Repeat as necessary until you can remain connected to the umbilical.
 

Figure 8.
A close up view of a non leak quick disconnect coupler being mated to its insert connector. Also
shown is a better view of how the vest tubing is routed and fastened.


6) Extras:  Currently under development is a backpack mounted ice water reservoir powered by a 7.5 amp hour battery strapped to a small 100 watt power inverter. This prototype unit holds half the amount of crushed ice, weighs about 25 pounds and the ice will last about 1 1/2 hours. The advantage is total freedom of mobility and the battery will last several hours for at least 2 or 3 replacements of crushed ice. This system has been great in helping me do my yard chores during the heat of the summer days. I wear a white insulated outer garment over the vest tubes while working in the Sun instead of using the black vest I wear at night (for stealth reasons). The only disadvantage of the backpack cooling unit is its weight, bulkiness, not being able to sit comfortably in a chair and my appearance looking somewhat like that of a Moon walking astronaut.

 

 List of Materials

3 Yds Open Mesh Fabric JoAnn Fabric Polyester or Nylon Drape Materials Dept.

1 Ea Vest Pattern Wal-Mart McCall's #8285-H Exact # depends on body size

AR Misc Bias tape, one inch belt material, plastic buckles, 4" and 8" cable tie wraps, etc.

100 Ft 3/16" I.D. Silicone Tubing U.S. Plastics 54032 1/16" wall thickness (5/16" O.D.)

18 Ft 3/8" I.D. Silicone Tubing U.S. Plastics 54037 1/8" wall thickness (5/8" O.D.)

1 Ft 3/8" I.D. Silicone Tubing U.S. Plastics 54036 1/16" wall thickness (1/2" O.D.)

2 Ea 3/8" Shutoff coupling body U.S. Plastics 60688

2 Ea 3/8" Shutoff coupling insert U.S. Plastics 60813

1 Ea Flow control pinch valve U.S. Plastics 64062 Fits 1/2" O.D. of P/N 54036

2 Ea 3/8" "Y" hose barb U.S. Plastics 64016

1 Ea Danner Mag-Drive pump Marine Depot DN115 Danner model# 1.5, 140 GPH

1 Ea 20 Quart ice chest Wal-Mart Rubbermaid or equiv.

4 Ea 1/2" Female PVC coupler Ace Hardware Both ends 1/2" female pipe thread

4 Ea 3/8" barb to 1/2" Male ADPT. Ace Hardware PL-328 Hose barb to male thread adapter

16 Ea 3/16" X 3/16" barb splicer Ace Hardware PL-101 Nylon 3/16" hose splicer

Links to Vendors:

http://www.usplastic.com/catalog/default.asp

http://www.marinedepot.com/ps_AquariumPage~PageAlias~powerheads_pumps_danner_mag_drive_supreme.html

Figure 10.
Finally an insulated sleeveless wind breaker is worn over the cooling vest.
 

 

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