Working with handicaps.

A mechanic at the forklift supply company I sold for stammered really bad.  A simple three or 4 word sentence took minutes to say.  In addition he couldn’t read and barely write, yet every week working against flatrate he put 80-100 hours in. He was the go to guy when others couldn’t figure out the problem.  

A couple of years after I started he damaged his hand so much they were going to put him on 80% disability, and since it was the companies fault pay him handsomely for his pain and suffering.  

Instead he made a deal, if he could become a salesman ( remember the stammering?) he’d forgo much of the settlement.  

In the end he became their best used equipment salesman and a very good seller of new equipment as well.  

The reason I bring this up is because I need some help with math.  It’s one of my weaknesses. 

If I want to increase the area of a circle by 60% what is the formula?  

I USED to be really good at this.  

Multiply the current area by 1.6. Done. 

Edit- area of a circle is pi (I cant for the life of me figure out how to make that symbol on my phone) r². So it would be (pi*r²)*1.6. R is the radius of the circle. 

Deleted. 

Foot removed from mouth. 

If you have the original area and want to increase it by 60%, you multiply it by 1,6.

A=area

r=Radius

If you then want to draw that larger circle, you will need the lower formula. That formula has the radius broken out.

Thank you, so if I want to make a jet flow 60% more, a jet say .125 

The ream I’d need would be .200?  

In reply to frenchyd :

Yes, you are spot on.

That's not correct; it ignores the fact that there's a square in the formula. The relationship between the diameters is linear (you can just multiply by a factor), but the resulting area is proportional to the square of the diameter. 

The area of Frenchy's 0.125" jet is:

0.125 diameter divided by 2 to get radius is 0.0625.

0.0625 squared is about 0.0039

0.0039 times Pi is about 0.0123, and that's the area of our original jet.

If we multiply that by 1.6 we get 0.0197, which is the 1.6 times the initial area that we are looking for. From there we divide by Pi to get 0.0063, then take the square root of that to get a radius of 0.079, times 2 for a diameter of 0.158. That is the drill you need for a 60% increase in area over 0.125.

BUT, if we just multiply that 0.125 jet by 1.6 for a drill of 0.2, we get a radius of 0.1, squared to 0.01, times Pi for 0.0314. Remember the original area was 0.0123. So a drill of .2" would give us 255% of the flow of 0.125", or a 155% increase.

I've been sloppy about rounding from the calculator, and I know that flow isn't perfectly related to area, but I think that's outside the question.

In reply to Ransom : WOW, thank you. That makes sense for me and I can follow your steps if I should want to solve a similar problem.  

In reply to frenchyd :

Awesome! I'm never sure when I write something like that whether I'm making things clearer or muddier. Glad it helped!

To put it simply, you multiply the diameter or radius by the square root of 1.6

If you want to make it 80% larger, multiply by square root of 1.8.

In reply to ProDarwin :

Boy is that simpler than walking through all the steps.

Hopefully my long-winded version helps illustrate why you can't just apply the factor to the diameter, but that's a much simpler way to do it.

frenchyd said:

Thank you, so if I want to make a jet flow 60% more, a jet say .125 

The ream I’d need would be .200?  

Ransom nailed the math but there's another factor that you need to take into account for your specific project. 

Orifice flow is effected by more than just the bore diameter.  The length of the bore and the shape of the inlet and outlet and the surface finish also play significant roles.  That's why Holley (and I suspect other carburetor manufactures) flow test their jets and then put the numbers on them.

That's not to say that you can't drill jets but that you may not get the results that you expect.  I've seen jets with tapered inlets and outlets flow less after they were drilled out.  Due to the tapers the drilled jet had a longer bore with a sharper inlet and outlet as compared to the unmodified one resulting in reduced flow. 

In reply to APEowner :

The cool thing is flow can be improved or reduced with the same tricks racers have been using since the 1940’s  ( I suspect the really sharp racers were using them long before  then)  not just Holley but Weber’s, SU Stromberg, etc.  

Plus unlike gas,  alcohol is wildly tolerant with clear indicators  of too rich or too lean.   Too rich the engine just gets lazy,  but doesn’t make big black deposits.  Too lean and it starts barking like a goose, but because alcohol is sooooooo cool it doesn’t melt stuff as easy as gas does. Just another reason us old Luddite ‘s should use E85 

Ransom said:

In reply to ProDarwin :

Boy is that simpler than walking through all the steps.

Hopefully my long-winded version helps illustrate why you can't just apply the factor to the diameter, but that's a much simpler way to do it.

Well, you got at the underlying reason... the radius is squared to get to area.  If the relationship were cubed, you would take the cube root, etc.

Similar example.  Torsional rigidity varies with diameter^4.  If you want a swaybar x times as stiff, you multiply the original diameter by the 4th root of x.  A 17.8mm bar is twice as stuff as a 15mm bar.

APEowner said:

frenchyd said:

Thank you, so if I want to make a jet flow 60% more, a jet say .125 

The ream I’d need would be .200?  

Ransom nailed the math but there's another factor that you need to take into account for your specific project. 

Orifice flow is effected by more than just the bore diameter.  The length of the bore and the shape of the inlet and outlet and the surface finish also play significant roles.  That's why Holley (and I suspect other carburetor manufactures) flow test their jets and then put the numbers on them.

That's not to say that you can't drill jets but that you may not get the results that you expect.  I've seen jets with tapered inlets and outlets flow less after they were drilled out.  Due to the tapers the drilled jet had a longer bore with a sharper inlet and outlet as compared to the unmodified one resulting in reduced flow. 

Hehehe he you said orifice. 

Mndsm said:

APEowner said:

frenchyd said:

Thank you, so if I want to make a jet flow 60% more, a jet say .125 

The ream I’d need would be .200?  

Ransom nailed the math but there's another factor that you need to take into account for your specific project. 

Orifice flow is effected by more than just the bore diameter.  The length of the bore and the shape of the inlet and outlet and the surface finish also play significant roles.  That's why Holley (and I suspect other carburetor manufactures) flow test their jets and then put the numbers on them.

That's not to say that you can't drill jets but that you may not get the results that you expect.  I've seen jets with tapered inlets and outlets flow less after they were drilled out.  Due to the tapers the drilled jet had a longer bore with a sharper inlet and outlet as compared to the unmodified one resulting in reduced flow. 

Hehehe he you said orifice. 

Now I'm glad that I didn't mention that I prefer to ream orifices as opposed to drilling them...

Frenchy, you're the man. If you can land a damn jet plane on a pitching, rolling, and yawing carrier, you don't need to know basic math! My granddaughters were doing the Pinewood derby for Pre-Girl Scouts. I couldn't make the cars for them without at least giving them a basic physics lesson in potential energy vs. kinetic energy. The equation for potential energy was much simpler than for kinetic. And that was more relevant for their race cars. I think I was successful. Good luck to you, my man. But seriously, don't stress it.

For what its worth, the initial stroy Frenchyd told about the mechanic turned salesman made my night.

APEowner said:

Mndsm said:

APEowner said:

frenchyd said:

Thank you, so if I want to make a jet flow 60% more, a jet say .125 

The ream I’d need would be .200?  

Ransom nailed the math but there's another factor that you need to take into account for your specific project. 

Orifice flow is effected by more than just the bore diameter.  The length of the bore and the shape of the inlet and outlet and the surface finish also play significant roles.  That's why Holley (and I suspect other carburetor manufactures) flow test their jets and then put the numbers on them.

That's not to say that you can't drill jets but that you may not get the results that you expect.  I've seen jets with tapered inlets and outlets flow less after they were drilled out.  Due to the tapers the drilled jet had a longer bore with a sharper inlet and outlet as compared to the unmodified one resulting in reduced flow. 

Hehehe he you said orifice. 

Now I'm glad that I didn't mention that I prefer to ream orifices as opposed to drilling them...

I realized how flawed drills are at making round holes when drilling out sheet metal with large sized drill bits.   

Appleseed said:

For what its worth, the initial stroy Frenchyd told about the mechanic turned salesman made my night.

I learned much more about selling from him than he learned from me.  I was the top, National major account salesman for the company and in his 4 months with me he taught me about how to read body language, sales timing, and when to just shut up and put the sales order in front of the customer and get the signature.  Shockingly it was much earlier than I had ever thought possible.  

He never lost his stammer, so much for the fast talking salesman idea.  Years later I spent a day with him again and I was very pleased that so many of his customers greeted him like an old friend and handed him referrals.  

frenchyd said:

In reply to APEowner :

The cool thing is flow can be improved or reduced with the same tricks racers have been using since the 1940’s  ( I suspect the really sharp racers were using them long before  then)  not just Holley but Weber’s, SU Stromberg, etc.  

Plus unlike gas,  alcohol is wildly tolerant with clear indicators  of too rich or too lean.   Too rich the engine just gets lazy,  but doesn’t make big black deposits.  Too lean and it starts barking like a goose, but because alcohol is sooooooo cool it doesn’t melt stuff as easy as gas does. Just another reason us old Luddite ‘s should use E85 

Please allow me to elaborate.  For those who understand all these,  skip past.  

I test flow jets with a simple calibrated vial and a stop watch. If they flow too much I put a nick in the jet which disturbs the flow.  Too little I can put a taper into the hole.  Change it from a sharp edge to a radius edge increases flow more.  

I lack the complete set of rheims  I used to have so I have to be a bit clever sometimes.  Try something and test, a test takes only a few minutes. Remember again alcohol is very tolerant, close is good enough.