Welcome to KnifeDogs


A Family Friendly Knife Oriented Community Founded For Knifemakers, Collectors, & Enthusiasts.


  •  » Forums for individual knife dealers.
  •  » Forums for businesses supporting the knife industry.
  •  » Knife makers individual forums for visiting, support and sales.
  •  » Forums for knives.

...then you have come to the right place!


we will try to help you with your problem.


YES! I want to register an account for free right now!


Page 1 of 2 12 LastLast
Results 1 to 10 of 13

Thread: Hiccuping forge

  1. #1
    Join Date
    Aug 2009
    Location
    Corbett, Or
    Posts
    366

    Hiccuping forge

    It's been a while since I've forged (just over a year) but I've been hitting it up the past few days. Made some improvements on the forge by putting in a needle valve. Seems to give me better temperature control as my forge quite often ran hot. Anyways, an old problem I had with the forge hasn't gone away like I was hoping it would. Best way I can describe it is my forge gets the hiccups. I have a forced air burner. There's a picture of the set up in this thread. http://knifedogs.com/showthread.php?...-Forge-is-Done! Anyways, after I've been forging for a while and the forge gets hot, it "hiccups." The burner sounds like it goes out then come right back to burning. When it "hiccups", it makes a sound kinda like you're blowing over the opening of a beer bottle or something. Hopefully what I wrote makes sense. Anyone ever have a problem like that? If so, how did you fix it? It always makes me jumpy when this happens. Makes me think I'm gonna blow up the whole shop or something...


  2. #2
    Join Date
    Aug 2009
    Location
    Gresham, Oregon
    Posts
    1,830
    Peter, Its your gas/air mix. After my forge heats up I turn the gas down and add more air. Just something you need to fiddle around with.
    http://www.hawknknives.com/

    Second chances don't stop at two.....

  3. #3
    Join Date
    Aug 2009
    Location
    Corbett, Or
    Posts
    366
    Okay. I wondered if that was it. Thanks for the help!

  4. #4
    That was easy! Peter will you let us know how that worked for you? I'm curious how you're going to adjust you gas/air mix, too. I guess I'd better go look at the picture...
    Dave

    Why doesn't Tarzan have a beard?

    Website

  5. #5
    Join Date
    Aug 2009
    Location
    Corbett, Or
    Posts
    366
    Will do Dave. I'm planning on forging a little tonight. I'll post a new picture so you can see my setup a little better to. I can control the gas/air mix pretty well with it.

  6. #6
    Great Peter, I'm looking forward to your success!
    Dave

    Why doesn't Tarzan have a beard?

    Website

  7. #7
    Join Date
    Aug 2009
    Location
    Corbett, Or
    Posts
    366
    Well no success tonight. The forge was being temperamental and didn't want to start... Not sure what the deal was. Maybe I'll have time to try it tomorrow.

  8. #8
    Good luck Peter!
    Dave

    Why doesn't Tarzan have a beard?

    Website

  9. #9
    Join Date
    Apr 2012
    Location
    Lancashire, UK
    Posts
    53
    Peter,

    It sounds like the hiccupping is the flame burning back down the burner tube.

    I'm guessing the gas mixes with the air some way from the chamber?

    At some point, the mixture speed towards the chamber needs to be higher than the speed the flame can travel through the mixture. The general idea behind the "flare" used on some burners is that the mixture speed drops as the area increases and somewhere in the taper the flame is moving through the mixture as fast as the mixture is moving in the opposite direction, resulting in a stable burn.

    The flame speed through the mixture varies with temperature and pressure, getting faster as it gets hotter. This is probably why it only shows up when the forge is hot.

    It also varies with Air:Fuel ratio. As this is what you want to control in order to vary the flame temperature, you ideally want to have free rein on the mixture and not be constrained by other factors like avoiding hiccupping.

    As the flame-front accelerates, it radiates heat and generates a pressure wave in front if it, accelerating it further. If nothing stops it, it will keep accelerating until it reaches the speed of sound. What stops it in your burner is running out of mixture; neither gas nor air will burn on their own.

    With a blown setup, you may be able to move the gas jet closer to the forge chamber; that way, there's less distance for it to accelerate over. Otherwise, it's a case of turning up the mixture speed to faster than the flame speed, or use a smaller tube to get the mixture speed up.

    With your setup, the gas goes in a long way from the chamber, so I'd be inclined to move the gas feed to the horizontal pipe. Your pic doesn't show the forge end of the burner arrangement, so it's not clear how easy it will be to move the gas feed, but I'd guess around where the clamp is would give enough distance to mix over. It doesn't necessarily even need to be fully mixed before it reaches the chamber; it is plenty hot and turbulent in there and will finish the mixing. Startup will probably be more difficult if the mixing in the burner tube is really poor though.

    Your burner tube looks pretty small already, so going smaller is unlikely to be sensible, especially if you are thinking of welding.

    It's a nice tidy job you've done on the forge.

    Tim

  10. #10
    Join Date
    Aug 2009
    Location
    Corbett, Or
    Posts
    366
    Tim, thanks for the advice! I had already done a little reading on other forums and I read about someone having a similar problem due to having the burner tube sticking to far into the forge and they were getting a preignition of the gasses. I pulled my burner tube out a bit and have figured how to run the forge at a cooler temperature and that seems to have solved the problem. I always had a hard time getting a low end temperature out of my forge. It likes to run hot. I think I've finally got it straightened out though. : )

    Peter

Page 1 of 2 12 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •