Question on blower for forges?

[millironknives]

I am just wandering what some of you have for the size of blower cfm on your forced air gas forges? By this I mean Propane forges. Not little coffe can forges but large up right forges. I ask because I have a 90 cfm blower on mine and I can reach welding heat up to 2400 degrees is the highest I have taken it to test it. But when warming up and when placing a billet in the forge it drops and takes a little longer to come back to welding heat that I want and I was wanting to know if I took and put on a bigger blower if I could solve the slow come back and slow preheat. mine is made from a large 16 inch pipe 2 foot tall and has 2 inch pipe for the blower burner tube going in the the forge at the bottom and at an angle to give the swirl effect. In my thread of my new shop pictures there is a picture of my forge. I am putting all the propane I can get in with this blower and still mix and burn it. any more and it would be dangerous. but I have looked at a ton of forges on the web and just for reference my forge body is bigger then geno's but he has a hell of a lot bigger blower. I was thinking of going to a 500 cfm blower to solve the problem but thought I would ask first.

[paul harm]

i'm not sure , but maybe you should reduce from the 2" to 1 1/2" inlet pipe . I'm sure someone else will have something to say - paul

[Bob Warner]

I doubt that changing the blower would help.

I am guessing that you are using kaowool for your refractory, can't tell from the photo in your shop photo picture. If you used castable, you would not get that drop, just very little and it would not affect your work. Every forge with kaowool I have seen has that temp drop when cool steel is placed in it.

Notice that Geno has castable refractory in is forge.

[millironknives]

No I have my forge lined with 2 inches of #8 lb kaowool and then poured with 1 1/4 thick cateable refractory. The type slips my mind but it is from refractories west and it is the same stuff used to make tim zawatas forges he sells. It is the best they sell for knife forges as it is highly resistant to temp shock and flux. It is bright white when fired and dried. Any way I also piut a 1/2 inch layer of kaowool on the outside of the forge with a light sheat metal skin. I know this is way over kill but I was trying to make it as effeicent as possible (propane is high priced as it is) and not be heating other things in my shop as well. Doing this made a huge diference as I can touch the outside shell and not burn my hand now. Also good for my kids. As my old forge used to stay extremely hot on the oustide for hours. I also beleive I get a better aneal this way just shutting down the forge and letting it cool slowly. And I mean real slow.
So where does that leave me?