1084 and 15n20 San Mai

1084 sharp finger style. The customer provided all the antler for the handle scales. Sheds from his property.

Hi Kirk, yes it has been a long time.  I have still been shooting and occasionally building bows.  I just got back from the Gene Foster Rendezvous at the Fresno Field Archers range.  I have retired and keep my interests in motorcycles, archery, etc.  Since I built a CNC router a few years back I am getting into that a lot.

Did I ever tell you that I am an electrical engineer?  Back to the power supply.  A few photos would help a lot.

I think I understand that you have measured 2.43 volts from one end of your heat strip to the other; on the positive and negative leads where they connect.  With no heat strip connected the voltage was higher, 3.xxV, because in this case no voltage is dropped in the cables from the charger to the strips because no current is flowing.  With the strips in place and 50 amps of current flowing there will be voltage drop in the wires since they too have resistance.  To drop 1.2 volts at 50 amps requires only 0.024 ohms which is in line with what heavy wire resistance would be if it is several feet long.

To get the power needed to heat the strips the V x I needs to be about 120 watts, according to your original data.  If you use 12 volts it takes 10 amps to get this power - that is why I think a 300 watt power supply will work.  Using lower current means that you can use smaller wires as well.  It seems a 30 volt, 10 amp supply should do the trick.

Can you photograph how and where you measured the 2.43V drop in your strips?  A photo of the battery charger gauges in operation will also help.  Lastly, can you measure the resistance of the heat strips from one end to the other?  On paper, you should get 0.0486 ohms with the 2.43V and 50A in the strips.  Measure the resistance with no power applied.  You may not be able to measure this low of resistance with most volt meters.  Before trying to read the resistance of the strips connect the two meter leads together and read their resistance and subtract it from the reading you get across the strips.

I have been interested in the SS heat strip and power supply method for years but do not build enough bows to warrant it out for my use but I would like to help bowyers make a better setup.

Cool story and pictures.  I like the full draw pic.  Congrats!

Beautiful bow, Kirk. What is the riser wood?


Mark

Quote from: Kirkll on November 10, 2025, 11:49:09 AMThis unit puts out 60 volts, 300 watts DC....

I think you want one of the 30V/10A supplies instead, that one only goes to 5A and that may not be enough.

For instance:
https://www.amazon.com/dp/B0DDPVDWPZ/ref=sspa_dk_detail_1?pd_rd_i=B0DDPVDWPZ&pd_rd_w=Mf0oy&content-id=amzn1.sym.7446a9d1-25fe-4460-b135-a60336bad2c9&pf_rd_p=7446a9d1-25fe-4460-b135-a60336bad2c9&pf_rd_r=7MTFR5P1RQK3J8E4FN5N&pd_rd_wg=IJ9PJ&pd_rd_r=2f5cc0db-2656-468d-a47c-77c2ee609cfc&sp_csd=d2lkZ2V0TmFtZT1zcF9kZXRhaWw&th=1

Quote from: Kirkll on November 10, 2025, 11:49:09 AMIsn't hooking up the positive and negative leads together with the heat strip between the leads a short circuit?

No, not if there is enough resistive load in the circuit. When operating in constant voltage mode the supply adjusts the current to keep the voltage constant at the desired setting. If you short the leads the resistance drops to near zero and the current has to spike super high to maintain the voltage output. This is what they are referring to.

Quote from: Kirkll on November 10, 2025, 11:49:09 AMEven if it doesn't turn off, keeping a constant voltage to reach temps needed for the heat strips may kick the unit off too with the other built in saftey features.

As long as you stay within the voltage/amperage/total power output limits the supply will run forever at that setting without issue.

EDIT - Just had a thought. Can you measure the resistance of the heat strips between where you attach the battery charger clamps?


Mark

Don't forget about adding nock weight to stiffen up spine on the 800's (heavier nocks, arrow wraps), if you don't mind/care about a lower foc.

Awesome stuff Norman!  

Quote from: Roger Norris on Today at 08:10:14 AMSo here is a question for the group....what would the PERFECT 2 blade double bevel head look like?

Also....are fixed bleeders like the Zwickey has a positive or negative?

The old/original German Kinetics Silver Flame - Crazy wicked sharp, and left massive blood trails.  Come to think of it, I need to scrounge some of them out of my broadhead bin and give them another go. I too got on the single bevel bandwagon and have been using 150 grn Cutthroats the past few years. They are nice heads, but the Silver Flames I think are more lethal.

So here is a question for the group....what would the PERFECT 2 blade double bevel head look like?

Also....are fixed bleeders like the Zwickey has a positive or negative?