This question is aimed at those of your who are using forced air for your propane forge.  I'm assuming most of you are using a 2" pipe from your blower to your burner.  What are you using to control the flow of air?  My blower doesn't allow restriction of the intake, so I will require a valve of some sort to control how much air I have moving.

The simplest would be an inline ball valve. Of course not knowing what type of motor the blower uses, the best would be a rheostat to slow down the motor.

It would help to know what type of blower you have.

If your blower cannot tolerate inlet throttling, there's a pretty good chance it will not tolerate discharge throttling either.

If it can't take throttling and can't be speed-controlled, you might find you need a tee with one leg to the burner and the other bleeding off surplus air. If you do, then it is a really good idea to route the bleedoff to an air curtain in front of the forge, keeping your tongs/handles cool.

Ball valves work and can be cheap, but have horribly non-linear characteristics and, with 90 degrees of travel, do not give fine control. Many use gate valves with some success. They are designed as shut-off valves, rather than control valves, but are reasonably good at controlling flow in this application, thanks to their fine-threaded adjustment: typically 10-20 turns from fully-open to fully-closed. Globe valves are normally the "correct" tool for the job, actually being designed to regulate flow and having similar fine-thread adjustment to the gate valves. That said, anything that works well enough to get the job done is good and the cheapest thing that gets it done well is optimum for most of us.

Sorry.  It's a Bouncy Castle type blower.  It's designed to keep blowing when it hits a resistance and return the air to it's intake to keep the motor cool.  I've been advised, repeatedly to use a gate valve and not a ball valve because of the linear flow problems.  Just curious what most of you are using to control the air flow.  I found a 2" Gate Valve for $26............which was a lot cheaper than the brass one at the local hardware store for $40!

Simplest is to just cut a slot in your pipe (I am using PVC from blower to gas inlet) and drop in a piece of sheet metal.  basically a simple gate valve.

You can also try a motor controller.  If it is a basic brushed AC motor, should be able to try that.  Harbor freight has a cheap one sold as a Router motor speed control.

I have a leaf blower I'm trying to use but even with the 2" pipe blocked down around 90% it was still too much air for my burner.  Could not get the forge lit and that was on lowest setting. 

DF - In The Shop on YouTube has a 3 part series of videos about a gate valve which also diverts excess air.  According to him it provides more linear control then a chopping gate valve

Here is video 2 in the series which gives a good shot inside the valve:

 

Here's a thread on the gate valve I made for a previous incarnation of my forge. It worked great.

 

Both "valves" are very interesting.  Thanks.

 I did something similar to what timgunn1962 suggested.  I use a brass gate valve to control air to the burner.  I think I got it at Moorlane Sutton Supply in OKC.  The rest of the air goes to an air curtain.  Haven't had much time to play with the forge but I'm retiring in August and when the weather cools this fall, I'll be spending a lot more time forging.  Good luck with your build.

Interesting idea.

On 6/7/2019 at 1:15 AM, Paragon said:

motor controller.

FYI: I've had problems with motor controllers in my shop (harbor freight).  when turned down, every time the compressor turns on the motor slows, big flames out of the forge, etc.  Admittedly, I've only got 40 amps in my shop and it's pretty maxed out, and it's a Harbor Freight controller.  But if you are in a similar situation, be aware.

DanR