Author Topic: Overtemperature Protection  (Read 15831 times)

Tijean

  • Full Member
  • ***
  • Posts: 208
    • View Profile
Re: Overtemperature Protection
« Reply #15 on: December 12, 2010, 10:00:11 PM »
You are more elaborate with casting the eye. I had in mind simply embedding something like a cup hook into the molten lead plug. 1/4 npt is a good size and easy to get 1/4 pipe couplings and cut in half to braze or weld onto the exhaust. You need more contact than just the thickness of the exhaust pipe itself. A coupling can be slit down the sides with hack saw or zip disc to create a workable die to thread the lead slug.
Frank

10/1 Jkson, ST5 gen. head

Tom

  • Hero Member
  • *****
  • Posts: 1746
  • Green power is good.
    • View Profile
Re: Overtemperature Protection
« Reply #16 on: December 13, 2010, 01:25:13 AM »
Lead wheel weights are alloyed with antimony to make them harder. You might want to check what this does to the melt temp before using them.
Tom
2004 Ashwamegh 6/1 #217 - ST5 just over 3k hours.

Tijean

  • Full Member
  • ***
  • Posts: 208
    • View Profile
Re: Overtemperature Protection
« Reply #17 on: December 13, 2010, 01:57:01 AM »
Lead wheel weights are alloyed with antimony to make them harder. You might want to check what this does to the melt temp before using them.

Good catch! Yes, it looks like it does lower the melt point. Fishing sinkers are nice and soft likely purer lead. They are starting to talk about making them lead free now though, maybe out of some rare metal that will cost 30 dollars a pound.
Frank

10/1 Jkson, ST5 gen. head

vtmetro

  • Full Member
  • ***
  • Posts: 120
    • View Profile
Re: Overtemperature Protection
« Reply #18 on: December 13, 2010, 04:35:39 AM »
You are more elaborate with casting the eye. I had in mind simply embedding something like a cup hook into the molten lead plug. 1/4 npt is a good size and easy to get 1/4 pipe couplings and cut in half to braze or weld onto the exhaust. You need more contact than just the thickness of the exhaust pipe itself. A coupling can be slit down the sides with hack saw or zip disc to create a workable die to thread the lead slug.

Sounds okay, but I think that will be slower to release than what I want personally. The bigger the plug the slower the melt in an overheat situation.

I was thinking maybe a #10 dia tapped hole in a  sch. 40 1-1/2" dia water pipe exhaust. That will thread and hold fine for this purpose.

Re wheel weight lead -- the fusing temp can be checked when melting before the pour, which I'll do.with a non contact thermometer. As a guess, the antimony may not be a problem from a practical standpoint anyway -- remember the exhaust pipe itself is going to be lower temp than the EGT since it's air cooled on one side and to release we have to melt out the full thread length of the plug in the pipe. It's a heat sink for the fuse.

Ideally we'd rivet the fuse in instead of thread it in, then we'd just be melting out the internal rivet head for a release. But riveting means we have to disassemble the pipe to renew the fuse.

Luckily 620F (or less for an alloy) is a fair way down from 1000F, which was the stated limit, earlier in the thread. So I'm guessing a small gage lead screw will melt out in time. Not sure where that 1000F figure came from for a Lister limit, but sounds reasonable as a ballpark.

I'm sure there will be plenty of creativity around this, and whtever the form it takes, anything is better than the nothing most of us have now for OT shutdown capability.

 

vtmetro

  • Full Member
  • ***
  • Posts: 120
    • View Profile
Re: Overtemperature Protection
« Reply #19 on: December 13, 2010, 05:21:29 AM »
I suppose another possibility would be wrapping a fuse of some sort around the exhaust pipe, though it would probably need to be lower in melting temp.

Some type of solder might even work here. Insulating it on the outside at some contact point might help make it more consistent vs varying air temp. Experimentation with a simple spring as a load would let you know if solder had too low a melt point. It's unlikely to have too high an MP.

Anyway, plenty of room for other ideas.
« Last Edit: December 13, 2010, 05:25:04 AM by vtmetro »

mike90045

  • Mendocino Metro
  • Hero Member
  • *****
  • Posts: 1594
  • Mmmm BBQ
    • View Profile
    • Mikes Solar PV page
Re: Overtemperature Protection
« Reply #20 on: December 13, 2010, 02:51:38 PM »
Heck, a 6" loop of wire solder around the pipe would work, except vibration my eventually wear it thru.    You can get bar sticks of solder &  pure lead lead from plumbing houses.

Tijean

  • Full Member
  • ***
  • Posts: 208
    • View Profile
Re: Overtemperature Protection
« Reply #21 on: December 13, 2010, 04:22:08 PM »
I have to agree on the quicker release with just having a button on the ID of the exhaust. OK, make a quarter inch pipe coupling half and plug opposite your small hole for the fuse; you can then slip it through and into place or rivet it in situ through the access plug! I will definitely give this a shot as I have no emergency shut down of any sort. The loop of solder over the pipe, maybe covered with a bit of fiberglass insulation sounds like a good quick and dirty way for a trial.
Frank

10/1 Jkson, ST5 gen. head

vtmetro

  • Full Member
  • ***
  • Posts: 120
    • View Profile
Re: Overtemperature Protection
« Reply #22 on: December 13, 2010, 09:38:32 PM »
Okay Tijean, what about this:

Get a 12" stainless braided wire leader from a fishing store. Cut off the swivel end. Burn the nylon coating off at that end with a match. Put that end through, say, a 1/16" hole in the exhaust pipe ( 1.5 mm or so) and crimp a small split shot sinker on that end in the pipe using needle nosed pliers. Done.

The other end has a nice snap for attaching through a suitable small hole in the rack lever. Clean, simple, fast, cheap. No welding needed for those who can't do that.

« Last Edit: December 13, 2010, 10:10:50 PM by vtmetro »

Tijean

  • Full Member
  • ***
  • Posts: 208
    • View Profile
Re: Overtemperature Protection
« Reply #23 on: December 13, 2010, 10:31:47 PM »
Okay Tijean, what about this:

Get a 12" stainless braided wire leader from a fishing store. Cut off the swivel end. Burn the nylon coating off at that end with a match. Put that end through, say, a 1/16" hole in the exhaust pipe ( 1.5 mm or so) and crimp a small split shot sinker on that end in the pipe using needle nosed pliers. Done.

The other end has a nice snap for attaching through a suitable small hole in the rack lever. Clean, simple, fast, cheap. No welding needed for those who can't do that.



Lol, I quit! , you have outMcGuyvererd me ;D
Frank

10/1 Jkson, ST5 gen. head