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I Forge Iron

Cobbling together a gasser


ThoffmanApis

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Working in the garage this weekend doing some cleaning and straightening, I found enough parts to cobble together a horrible version of a propane forge.  Pictures are still to come but to get your cringing to start early I’ll give you a little description.  The body is an unused 1 gallon paint can from another project.  Cut a couple holes in it and used a scrap piece of PVC for the center.  I mixed up some homemade refractory from left over clay from building my charcoal cart forge, and filled the can around the pvc and a 1/2 inch pipe for the burner hole.  Whipped up a T-burner with a 0.025 MiG tip.  Really the only thing I had to purchase was a regulator and a couple of fittings.  All in all I’ve got about an hour of labor involved and was able to mostly use scraps laying around the garage.  

Fired it for the first time last night to start tuning the burner.  Trimmed down the MiG tip only to realize my welder tip file for .025 tips is broken.  Ah well, guess it can wait a day or two until I run past the store.  Hopefully by then I’ll have pics as well.  Up next is to forge a small cradle for it to sit on.

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Cool, I don't know how long the clay will hold up but cross that bridge when you get to it. It might take a while to get up to temperature also. Takes clay a while to heat up. More experienced souls than I will have some advice for you soon I'm sure.

Pnut

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And let the cracking begin.  It's a fun experiment at any rate. I think if I get the burner tuned before the whole thing falls apart I'll call it a success. 

Replaced my broken torch files and cleaned up the cut from yesturday.  It's running really rich at the moment so more trimming on the tip is in order.  

I've got no flare on the burner pipe right now, just relying on larger size of the hole through the forge wall. Thoughts? Should I flare it out slightly or just not worry about it with such a rudamentary build?

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Getting rid of threads to 'improve airflow in a "T" burner has been shown to be a waste of time. However, getting rid of threads from the two air entrances to increase their size might do a lot for this burner; this is because the exit and mixing tube are supposed to be smaller than the air entrances, to promote swirling (and therefore gas/air mixing)--just a thought.

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Cutting the threads out lowered the efficiency of my version of a flare so I stopped. I use a thread protector on my Ts rather than a tapered flare and then mostly to make it easy to mount burners.

Guys were starting to put tapered flares on their burners and I figured what the hey and chucked one up in the lathe and cut the ID into a 12:1 taper. That T burner didn't work quite as well with the tapered flare as it did with a thread protector. I tried just cleaning out the threads and that was worst of the 3. 

Then I drove down the HVAC place at the end of my road and bought a coupler thinking I could make a longer flare with all that thick iron. Not worth the effort so that was my last experiment, I still have the second coupler but spent enough time to satisfy my curiosity.

It was a mystery why a thread protector made more induction than one that was smooth inside. Then some years later I was looking through a couple web sites about high performance bush planes, a close friend of mine bought a really CRAZY expensive one so I thought I'd see what the buzz was. WOW Petzel! :o

Anyway, the top of the line best bush planes on earth seem to share skins with ridges like sharp corrugation, others with all these little tabs sticking out of the skin. As it turns out a fluid (air counts) flowing over a curved surface forms a low pressure boundary layer and so the moving fluid doesn't actually touch the surface strongly. Less friction allows it to move faster, faster air means more lift so your bush plane can take off and land in less space.

It made me wonder if the threads in the thread protectors weren't behaving like the ridges on high performance bush planes where the air (fuel air mix) flowing across the threads was making a low pressure boundary layer and accelerating as it exits the burner.

No I have nothing but opinion and supposition to support the thought and I still think it's nuts. However I can't think of another reason why leaving the threads in the thread protector works better than turned and polished smooth.

Frosty The Lucky.

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On the other hand, not once have I seen those who did get rid of internal threads for the purpose of smoothing interior surfaces to improve flow, claim it did so. Yet the amount of work to smooth burner parts by removing threading is plain to see; especially for those who have no lathe. On the other hand, removing threading to increase inside diameters is a solid move.

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I’ve spent a lifetime in the aviation industry, specifically maintaining, repairing, and building aircraft, everything from high lift designs, like STOL bush planes, to high altitude, high speed aircraft. The raised tabs you saw are called vortex generators and they are used industry wide for a couple of different reasons depending on the application.  They are typically straight into the airflow or angled slightly, never completely perpendicular to the airflow over the wing.  The dynamic function of creating a bounty layer is as you describe but in order for it to work it must be over a curved surface which a t-fitting is not, it’s straight on the inside. While the airflow is bending through the fitting it’s the surface curvature that counts in  Bernoulli’s Principle.  If your supposition were true I think we would see every throttle body in every high performance installation threaded as such.  But I’ve rebuild a lot of carburetors, aviation, automotive, etc. and I’ve never seen a threaded one.  The other similar situation would be high performance intakes of combustion engines.  Porting and polishing to create the smoothest surface is the way to go, I’ve never heard of porting and threading to increase airflow.

Don’t get me wrong, I’m not saying you didn’t get the results you did with threads vs no-threads.  I’m just saying I don’t think your logic is supported by aerodynamic theory.  I’d love to see a smoke chamber test on high speed camera to show the airflow through a t-fitting to see what’s really going on because I agree that your results are nuts, very counter intuitive if you ask me.

My soapbox aside, I just finished some touch up clay work on the forge.  I am in complete agreement for anybody who’s thinking it, clay was a bad idea, but it was left over so oh well....  As for the burner, I think my first change will be to shorten the tube, it’s 6 inches as that’s what I had laying around, but based on Frosty’s design it should be 4 inches, i.e. 8D on a 1/2 inch diameter.  So we’ll see how a shorter body changes things.  If it’s still on the rich side I’ll be shortening up the MiG tip to hopefully draw in a little more air.  I’ve still got to rivet together the cradle I forged up and then we’ll call this experiment done.

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Good Morning,

I have spent many days, weeks, extra long hours, trying to figure out cylinder head air flow on my Flow-Bench. I have long ago come to the conclusion that shiney smooth has LESS Air Flow than slightly rough surface. Slightly rough has at least 2% more Air Flow at the same differential pressures. Look at a fast flowing river, there are small back eddies at the edges of the river banks, the major flow rides on a cushion of eddies allowing less resistance. Rub your hand over the Olympic Racing sculls/boats and they have a pebbley surface. The same as Golf Balls. Don't get caught up in the "Glitter is the Best" game. Some Turbulence causes better air/fuel mixing as well as not hindering Flow Volume.

Intake and Exhaust port flows are opposite. Exhaust is high pressure, path of most flow is the longest path, there is no flow on the inside radius of the bends, often times reverse direction of the main Flow.  Intake Flow is opposite, run a string through the port and pull it snug, that is the path of most Flow.

The difference in a Forge, there is no pulse length. The flow is only one direction, except where it isn't. There will be reverse flow in some corners, depending if it is Atmospheric Burner or a Blown Burner. Absolutely identical except different.

Neil

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9 hours ago, swedefiddle said:

The difference in a Forge, there is no pulse length. The flow is only one direction, except where it isn't. There will be reverse flow in some corners, depending if it is Atmospheric Burner or a Blown Burner. Absolutely identical except different.

Neil

I'll counter that with it's absolutely not identical except not different.  Unless we're talking of the areas where the flow is multi-directional except where is only one direction. LOL!!

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Good Morning,

Some people think 'Hot Air' is exciting. Maybe if you have a big enough container to contain the self induced 'Hot Air'.  Up, Up, Away, in my beautiful..........  LOL

Air does weird things when it is compressed or there is a low pressure. Whodathunk atmospheric is High pressure??? Add some liquid gas and it becomes weirder!! Noncompressable and compressable in one can of worms. Poor worms!!

Isn't the English language fun? Absolutely Definite possible Maybe.

Neil

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  • 2 months later...

Update on this build:  

It's been a fast fall and haven't had much time to play with this. Bottom line on the build, it sucks.  Ha ha.  As noted above, it takes forever to heat up. 30-40 minutes to even get the forge to temp and then the clay just wicks the heat away from the metal.  It's just not worth the propane to continue use.  Of the few times I fired it up I ended up lighting up the charcoal too as I had projects to get done and didn't have hours to spend waiting around.  It was a fun experiment regardless.  It certainly hasn't dissuaded me from going to gas in the future but it will have to wait until I can either invest the proper time in a build or invest the money going the commercial route. 

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On 8/21/2019 at 2:24 AM, swedefiddle said:

trying to figure out cylinder head air flow on my Flow-Bench.

My dad told me a long long time ago that you either port or polish but do not port and polish. You need the turbulence inside the intake and heads so that like you say the air moves faster but also the fuel mixes better with the air. Any way i was having basically the same thoughts i guess. 

Wish i had a flow bench. 

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Good Morning Billy,

Yes, you port to change the airflow. Higher Flow allows the engine to work better at higher RPM, NOT at lower RPM. The components for an engine have to have all the right pieces to allow it to make horsepower. Some make their horsepower at low RPM, some at high RPM. There is no ONE component that makes or breaks the power.

Semi-Polish removes the rough edges. Mirror polish is a decrease of at least 2%. Think a fast moving river, there are eddies at the edge of the river that actually move the water in the opposite direction as the main stream. The main stream is riding on the cushion of the eddies, not the friction of the river edge. The slower moving the river, the larger the eddies, the less volume in the flow. A slightly rough edge allows the eddies to be smaller, thus allowing more Flow. Yes I know, Fluid and Air react differently, but in this example it is easier to get a visual example, not specifically what is actually going on, but close to it.

Lining a canoe up a river partially uses the eddies to push the canoe up the river. Yes, probably without a paddle LOL.

Neil

 

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I will have to take your word on the science behind it. I have built only a couple of motors but they were from blueprint. I take care of what is behind that motor. I build trannies and rear ends for a living. The car is a whole bunch of components that must work in concert with each other. No matter how many horsepower the wrong second or third member can greatly diminish what that car should be capable of. 

I was just thinking that we were both thinking basically the same thing...to smooth. 

One other thing i would like to mention here. A while a back ago when i was building my gasser i read on i think on Ron Reill's site that a good way to line up the jet with the mixing tube is with water. Attach a hose to the inlet and push water through the jet and look to see if it comes straight down the middle. Of course you want to blow it out real good and make sure it is totally dry before using. 

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Good Morning Billy,

If you leave your Forge burner a little loose, you can hear the change when you move it and tighten it where it is the loudest. K.I.S.S.

Yes, the same thoughts. Potaato, Potahto LOL  The hard part to get your head around is "There is a Pulse length", Yes it is able to be calculated. Think, fuel stand-off above a Carb, that is the pulse bouncing back up, before it turns around. Yes it is happening at any RPM. If you take a small strand of cotton at a Tailpipe, you can see the pulse in the exhaust. Yes, the pulse length changes with RPM. It is a matter of picking your optimum, there is no such thing as perfect.

Above the clouds, It is always Sunny!!!

Neil

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