Re: [Harp-L] Reed slot needs to be shortened

[Vern <jevern@xxxxxxx>]

It is big....about the size of a lunch-box thermos bottle, 3" dia x 8.5" long.  The low 20V rating keeps the size within reason.  If the voltage rating were higher, they would indeed approach the size of a suitcase...and would be as deadly dangerous as a cobra.  They are used to "stiffen" the 12V electrical system of a car to prevent the lights from dimming when the hi-power audio system blasts out loud bass notes.  The high-volume current peaks come from the capacitor and not from the car battery.  

IF the welding probe doesn't make good contact with the reed, there is a loud pop, a flash of blue arc, and a destroyed reed.  If there is good contact, there is a satisfying little "thunk" sound and a good spot-weld.  Charged to 18V,  the cap holds about 162 joules (watt-seconds) of energy.  Eye protection is essential.

People making electrical vehicles use capacitor-discharge welders to connect hundreds of little rechargeable batteries with stainless steel ribbons.  There is information on the internet about these battery welders.  I think that the liability risks would be unsurmountable for an individual to offer reed welders for sale. (Getting Underwriter's Lab approval, insurance, etc.)  Maybe a kit would work.  However, they are not complicated or difficult to make.  If you are interested in reed welding, contact me off-list.  I would like to correspond with another experimenter. 

Vern



On Nov 8, 2010, at 7:38 AM, joe leone wrote:

> 
> On Nov 8, 2010, at 1:42 AM, Vern wrote:
> 
>> I have been experimenting with my recently-completed  DIY Capacitance-Discharge Reed Welder. Key components are a 1 farad 20V car-audio capacitor and a power thyristor with a 1000 amp surge rating.
>> 
> 
> 1 farad capacitor? 1 farad?  What is that, about the size of a suitcase?   lolol