Monday, October 3, 2011

Portable 12 Volt Motorcycle Helmet Air Conditioner

Motorcycle Helmet A/C: The Holly Grail.

There have been many patents and prototypes for an air cooled helmet. A few companies even got products to market but most seem to have failed. The exceptions are cool suits which are expensive, cooled by ice and very bulky. The other system I have seen is a small compressor Air Conditioner. Currently produce only for the military, the company would not reply to my inquiries.

Looking at the other idea and patents for helmet air conditioning. I got to pick and choose what worked the best. The use of the Peltier seems to be the only common denominator I ended up using.

The best delivery system for cold is liquid, not air. This was one reason I ruled out air delivery systems.
Whole systems built into the helmets adds too much weight and any holes added compromise the integrity of the helmet.

This lead to the following bench test contraption.

To Start with, I purchased a complete Peltier cooling system for around $30 USD on the internet. This is the system that is used in 12V carry along cooler/warmers.
This included cold and hot heat sinks. Neoprene insulating pad, Duel shaft fan and a Thermal switch. Plugs into a 12 Volt outlet. The TEC is a mystery. The seller thinks it may be 80 watts and there are no markings.

 The Plan:
To loop poly-tubing through the channels of the cold side and run them to a cap embedded with water loops. The Peltier system would fit in a small back pack and plug into a 12 volt accessory plug.

This is what 39 feet of 1/8" ID polyethylene tubing looks like wrapped around a 6" by 5" finned aluminum heat (cold) sink. I used aluminum ducting tape to hold it in. The center area was left open for the photo.

This is the first completed system. 

I had to make tubing connectors, The cap was custom made by Ebayer Hatsbyaya, $4 and fits perfectly, is placed the cap over a mixing bowl (simulated head). 
I took test temperatures under the bowl. 
I placed the pump before the chiller in the off chance if there was any heat generated by the pump, it would not bleed into the chilled water heading to the helmet.

Pump #1:  A new windshield washer motor, $9 from the web. It never worked. I took it apart to find one of the o-rings used to seal the drive shaft was larger than the space allotted letting the motor case fill instantly with water.

Pump #2 Shown above is a 12 volt RC model fuel transfer pump. This pump lasted 105 minutes. Upon dis-assembly I found the impeller had stripped off the shaft. I assume that the back pressure of 1/8: tubing was to great. $15 pumps were not built for this.

Pump #3 A Mr. Gasket Electronic fuel pump, $48 at Autozone. This pump lasted 2 hours. Pump failure is undetermined as of yet not having the time to cut it open but there was a lot of oil in the water.

What follows is the very limited data I was able to collect.

The first several tests caused coupling failure, each cost a day in drying time for the new coupling. My kingdom, such as it is, for a 3-D printer!

Test #1 R/C model pump, set up as shown above. 
72 seconds to circulate once.
10:55 Turned chiller and pump on. Ambient temperature, 86 F
12:00 Turned the pump off and left the Peltier running to cool the sitting water.
12:16 Turned pump on.
12:20 Ambient temperature 96.5 F, Interior of mixing bowl 87.5 F
12:35 Ambient temperature 99.5 F, Interior of mixing bowl 89.0 F
12:40 Pump failure.

What was achieved:

The system as set up did manage to cool a helmet by 9-9.5 F. There was no head body heat load nor a heat load from the sun. However, neither the tubing nor the cooler have any insulation.

Changes after test one:

Both aluminum heat sinks were polished where they contact the TEC. This insures a more uniform contact surface for a higher thermal transfer.
The poly tubing was replaced with 24 feet of 1/8" OD copper tubing. I found that tube bending tool did not work as well as using a spring cover over the area to be bent.

Set up number two, ready for testing.

Test #2  Mr. Gasket pump, set up as shown above. 
6 seconds to circulate once.
4:10 Ambient temperature. 92 F. Start chiller, no pump.
4:35 Water temperature at chiller inlet, 93.5 F.  Water temperature at chiller outlet, 73.0 F Core temperature of chiller, 53.3 F
4:36 Start pump.
4:46 Inlet temperature, 84 F outlet temperature 79F.
Mr Gasket pump spurts oil into the water loop and seizes.

Lessons learned:

Pumps are the Achilles heal of the system.
1/8" OD tubing is too small to be effective in real world use. I believe it also lead to the pump failures.
Efficiency through insulation has much room for improvement.

Future plans:
As I post this, I am waiting for the remaining parts to assemble a complete, off the shelf, wearable unit that can be tested under real world conditions. 

Parts for the next unit include: 
2-Corsair H60 coolers (Received)
Larger TEC  (Received)              
Aerogel Insulation (Received)

This project is open source. Anything posted in this article is free to be used for personal consumption.

I will continue to work on this blog as needed as information is prepared

If this has been a help, saved you money...send a little my way. Any proceeds will be used to fund this and other ideas as they come along. Sorry, donations are not tax deductible.

Thanks for looking at the musings of a Crazy Old Man!


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