1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.


  2. Click here to enter the drawing for your chance to win a Boker Urban Trapper Cocobolo , Bladeforums.com swag or memberships!
    Be sure to read the rules before entering, then help us decide next week's giveaway by hitting the poll in that thread! Entries close at midnight, Saturday June 15!

    Once the entries close, we'll live stream the drawing on Sunday, June 30 at 5PM Eastern. Tune in to our YouTube channel TheRealBladeForums for a chance to win bonus prizes!

    Questions? Comments? Post in the discussion thread here

    Also, previous Live Stream Prize Pack winner, ooitzoo, has chosen to "pay it forward" with his knife that he won and is doing his own giveaway, check it out here: https://www.bladeforums.com/threads/nib-cold-steel-prolite.1663761/

Finally made some progress on my forge

Discussion in 'Hammer & Tongs' started by brodbeckrt, Jan 14, 2017.

  1. brodbeckrt

    brodbeckrt

    27
    Feb 25, 2016
    So I started my forge over the summer and had to put it on hold to sell my house. In the midst of all of the fun stuff that comes with moving I broke my leg. Needless to say we're finally moved in. I have been itching to get my forge completed and I made some progress on the burner. Good news is, it is burning and gets really hot. Bad news is I cannot get a smooth burn. I'm thinking it's my blower set up. I just threw it together to get it hooked up. I'm guessing there is a lot of turbulence in the air which is causing the crappy burn. Either that or I need to figure out a finer way to adjust my air from my blower.
    [​IMG]


    Sent from my SAMSUNG-SM-G935A using Tapatalk
     
  2. brodbeckrt

    brodbeckrt

    27
    Feb 25, 2016
  3. Stacy E. Apelt - Bladesmith

    Stacy E. Apelt - Bladesmith ilmarinen - MODERATOR Moderator Knifemaker / Craftsman / Service Provider

    Aug 20, 2004
    A gate valve works better as it can be slowly opened and closed to fine tune the air volume.

    If the problem seems to be too much air, put a choke plate on the air intake of the blower motor.

    If the problem is not enough static pressure in the air manifold, get a bigger blower.
     
  4. brodbeckrt

    brodbeckrt

    27
    Feb 25, 2016
    So if I put a choke plate on the intake and the problems worsens I need a bigger blower?

    Sent from my SAMSUNG-SM-G935A using Tapatalk
     
  5. Callum.D

    Callum.D

    58
    Jul 17, 2015
    Yup, to second stacy; Turbulence is caused when the velocity of a fluid within a pipe (or in this case a burner) reaches the point at which it transitions from smooth laminar flow to turbulent flow. Basically this means that if turbulence is indeed the cause of your problem reducing the airflow into the burner and thereby changing the ratio of viscous to inertial forces should see it transition back to a smoother laminar flow. However if reducing the airflow has no effect then your probably not pushing enough air through and you'll need a bigger blower.

    At least I think thats how it all works, I studied fluid dynamics a wee while ago.
     
  6. Stacy E. Apelt - Bladesmith

    Stacy E. Apelt - Bladesmith ilmarinen - MODERATOR Moderator Knifemaker / Craftsman / Service Provider

    Aug 20, 2004
    Callum pretty much has it.

    If the problem is having to close the manifold valve too much to lower the flow, the reduction as the air passes through the valve will create turbulence. In a butterfly valve, the air is directed at an angle, creating a vector, increasing turbulence. In a gate valve, the air passes straight through a smaller space, so it isn't stopping the laminar flow as much (streamline airflow).

    By adding a choke, you can lower the air flow into the blower, thus not closing the manifold valve as much. This makes a larger opening for the air to pass through, and decreases turbulence. At tuned full flame, the perfect setup is the manifold valve wide open and the gas needle valve wide open. The regulator valve and the choke are used to fine tune the flame to a smooth and even burn. Neutrality of the flame at full burn is the desired result when everything is tuned ( neither oxidizing nor reducing).

    You should be able to tell if there is not enough air from your present blower because you will be running the blower with the manifold valve wide open and still can't get a good stable flame. When running at full tilt and properly tuned the flame should be stable and sound like a small jet engine at idle. The sound should be smooth and even.


    As said, if the above things don't stop the problem (which it likely will), then a larger blower is probably needed. It is always better to have a slightly oversize blower. It will increase static pressure and can be choked back to lower the air volume if needed. If the blower is far too large, over choking can create starvation turbulence.

    Adding VS to the blower is another good thing. A DC blower is easily speed adjusted, and 3Ph blowers c an run on a VFD. You still want the right size blower, though.



    I will add some more info on blowers:
    There are all sorts of things that will deliver air. They range from old fashioned bellows to digitally controlled toroidal blowers. THe most common is a centrifugal blower. The ones most folks use are the common squirrel cage type. They have even rows of closely spaced and slightly angled vanes. These work OK, but have lower static pressure, especially at low speed. The centrifugal blowers with angled larger vanes (often curved - toroidal) will deliver more air and at a higher static pressure. The static pressure does not drop as much when turning slowly. This is needed for larger burners and almost a requirement for a coal burning forge. These are very expensive compared to the squirrel cage types. In most cases, a Dayton squirrel cage blower that delivers 80-150 CFM is suitable for a blown forge.

    THe cheap low cost blowers are fine for cooling computers and motors, but not so good for burners. A good rule of thumb is that if the output end isn't at least a 2.5X2.5"" opening it is probably too small. Hair dryers and leaf blowers are not the things to use. The better grade blowers have 3X3" or larger exit ports. 120VAC blowers can be speed controlled with a light dimmer. A dedicated fan speed control is a bit better, as the light dimmers aren't rated for the lode of many blowers. A DC blower can be controlled by many types of speed controllers.

    Somer basic prices listed in order of power and usefulness ( 1-2-3):
    1) Toroidal forge blower ( electric or hand crank) - $500-$600.
    2) Dayton 120VAC squirrel cage forge blower, 125-150 CFM - $100-$120
    2) Dayton 12VDC squirrel cage forge blower, 100-150 CFM - $125-$150
    2) Used squirrel cage blower from a boiler or large gas/oil heating unit - Free to $100 (Can range greatly in CFM, so get the specs first. Many are far too big.)
    3) Cheap squirrel cage blower from eBay, HF, or yard sale - 50-100 CFM - $20-$75
     
  7. brodbeckrt

    brodbeckrt

    27
    Feb 25, 2016
    Thanks everyone for the advice! I just picked up a gate valve and figured out a way to plumb everything with less turbulence. We'll give it a shot. If not it's time to go blower shopping

    Sent from my SAMSUNG-SM-G935A using Tapatalk
     
  8. Callum.D

    Callum.D

    58
    Jul 17, 2015
    let us know how it goes
     
  9. brodbeckrt

    brodbeckrt

    27
    Feb 25, 2016
    Callum and Stacy, thanks again for the advice. After trying another set up, replacing the tee with an elbow and adding the gate valve, I did get a better burn. It had a lot less sputtering. From my interpretation of Stacy’s description it should sound just like a louder version of an oxy-acetylene torch. Correct? It still didn’t sound like that. I still could definitely hear sputtering.

    Also seeing the descriptions of the blowers listed, mine has to be too small. It doesn’t have any performance specs on it, but it’s only like a 1/50 HP motor and the outlet size is only 2”. Will I need to resize my blower inlet piping for a larger blower with something like a 3” outlet? Obviously I will have to get a reducer to tie into my 2” piping but do I have to replace anything else?

    Since I was just testing the set up I didn’t have any of my blower connections completely air tight, in case I had to change it. Would that have had enough of an effect on the system to throw it off? I am thinking that it does have some effect on the blower pressure but wouldn’t completely screw it up.
     
    Last edited: Jan 20, 2017

Share This Page