Need information on a blower

[billp]

Now I was looking for an answer to the question of how big of a blower do I need for a coal forge.
I had placed this question on another post but I fear it has gotten buried in the back so I'm re-posting it here for an answer. Now specs were given by Goatman on air pressure and pipe size in the other post, but they left me scratching my head and still not sure.
I know, I know a box of rocks and a bag of hammers may be smarter, BUT?

I have a fire pot 6" at the bottom 8" at the top with a 2" depth, home made, my blower will be about (including the 90 degree turn) 6" to 8" from the bottom of the fire pot. This will go into a table 2' square and for right now no hood.
OK, now I'm looking at 2 blowers; one has 60 cfm, .42 amp, 3,030 rpm, 1/25 hp. The other 148 cfm, 1.37 amp, 3160 rpm and 1/25 hp. both have adjustable air inlets, which is the better choose? There is only about $8.00 difference in the price but the smaller one has a round discharge while the other square. So for me the round is easier to rig up to the forge but I still want the best for the job not the easiest.

OR, to make matters worse are either of these blowers right or do I need something smaller or bigger? Now Frosty did respond before but still left a few questions for me, sorry Frosty.

So you see I am still very new and know very little but slowly and surly I'm getting better. And yes I do plain on going to classes but only one place near me teaches and want start back till the first of the year. So for now it's books and the help from all you much more experienced guys out there who I really do appreciate.

Again if it's not asking to much, Help!
Bil P

Edited April 6, 2009 by billp
spelling as always

[Mick]

Hi billp, I have been going through the same process over the last week. Just found this thread about half an hour ago whilst trolling through various posts. I think it may answer some of your questions, It did for me.

http://www.iforgeiron.com/forum/f22/blowers-842/

Sorry can't figure out how to do that s a hyperlink, but you can copy / paste it in your browser.

Mick

Well there you go, hit the post reply button and bingo it turned into a hyperlink.............ahhhh the wonders of modern science.

Edited April 6, 2009 by Mick
I just had a WOW LOOKIT THAT moment.

[billp]

Thanks Mick
It kind of helps but then again????
I do know I would give my left something or rather to get a hand crank blower. It does seem to me that the hand crank is the best answer but, I just can't fine one around in my area.
My grandfather had one on his farm but I was about 10 or 11 when the family sold it off and heaven only knows where that blower is today.
Anyhow I'll keep looking and working out the problems of the electric blower.
thanks again
Bill P

[orgtwister]

i think the 148 cfm is to much i have i think a hundred cfm on mine and is to much i would go with the 60 if i had to choose one .I don't know what they are asking for the blowers around me you can find electric blowers at the flee markets for around 10 bucks i paid 5 for mine about 10 years ago

[Mick]

OK Bill, it seems that both of us are in the same place as far as forge building and smithing experience goes, so you know that what I have figured out is not based in hard experience. If it makes sense to you it may be of some assistance, use it as you see fit.


What works on one mans forge may not work on another. The number of variables in any forge set up ensures this.

Some of the variables, other than the blower itself :-
1. Diameter, length, shape (bends etc,) air tightness and materials of air delivery plumbing. All of these will have an effect on the percentage of loss in air volume, (cfm) and air pressure delivered to the tuyere. {Your lungs have a fixed capacity to exhale, if you blow that capacity through a drinking straw you can create a strong blast of air, if you do the same through 6 feet of vacuum cleaner hose you would barely notice the result at the other end.}
2. The tuyere design. How well the ash dump seals off the bottom of the tuyere and how much the grate (and fuel and clinker) restricts air flow out of the tuyere.
3. How big you need the 'hot' fire to be. (A fire big enough to heat 1/4" round stock would not be enough for 3".) The bigger the fire you need the more air you need delivered out of a bigger tuyere.

Whatever blower you use, hand crank, bellows or electric, it will need to have a capacity in excess of your forges requirement in order to overcome losses and restrictions within the system. The excess air is then 'tweeked' out by using intake restricter, inline air gate or air dump. Obviously if you go too big the ability to fine tune would be soooooo much harder to achieve.

From Mr Woolridges post in the thread above I am assuming that a blower with bigger blades that moves more air per revolution is going to work better for forging than one with little blades that is spinning like crazy. We seem to be more in need of air volume rather than high air pressure, but air volume that will not stall when confronted by restrictions in the system.

On that basis I would opt for the 128 cfm blower you spec'd earlier. It would not be too hard to glue, stick, weld or jam a round pipe into a square plate to make a manifold for the square outlet on that blower. Being that it is built with an intake restricter this should provide you with the all important 'tweekability'.

Oh and I had another 'WOW LOOKIT THAT' moment. To keep track of a thread just click on the bit that says 'Thread Tools' at the top of the page, then click subscribe to this thread. Sure beats the heck out of trying to remember and find the ones yor interested in.

Let me know how you get on.

Mick

[Oak Hill Forge]

You can always regulate a larger blower (within reason) by restricting the inlet or the outlet, but you can't make a blower that's too small blow more. You could even divert extra air elsewhere if you have too much (such as up the chimney if you have one to create draft.

[billp]

The blowers I'm looking at go for 72.95 to 64.95 new and are sold to go with an inflation system by a growers supply catalog. I was looking on line at Dayton blowers and these are the same if not close to size and price that Dayton offers. It's been a while since I have shopped flee markets and such but looks like I may have to start back again. Seeing that I started with an old metal hair dryer on a tire rim forge which just did work, then moved up to a small 2" 13 CFM Dayton blower which was like day light to dark in the difference it made. So with this new forge I do want it right to start but to be honest would still prefer some type of hand cranked blower over all.

So if anyone knows of any place or person selling hand cranked blower I would love to know who, what, and where. I keep looking but so far no luck but somehow I think that's par for the up and coming blacksmith with out just falling into one out of pure luck.

Any how you make since Mick and Oak Hill as both blowers have a inlet damper to regulate the amount of air the bigger might be better as you can always back off a little but you can't go up if your at your limit at the start.

Bill P

Edited April 7, 2009 by billp
same again spelling & to add information

[Finnr]

Try a local HVAC place they often have blowers from junked furnaces that will serve you very well cheaply or free.
Finnr

[Francis Trez Cole]

In my forge I use a dayton blower Model # 99080464 picked it up nat granger $65.00 My fire pot is 12"x12"x4"d and I have no truble reaching welding temp. been using it for the last 10 years