Eric Johnson (00:00)
Welcome back folks. This is Boiler Wild episode ninety one. My name is Eric Johnson. I am the host, the one and only host of Boiler Wild. Boiler Wild is a podcast where I talk about boiler industry topics as well as personal development. They go hand in hand. We need to get better in the boiler industry. We need leaders in the boiler industry. And I know the listeners of Boiler Wild are the people who want to get better every day.
Eric Johnson (00:29)
people who want to be leaders and to help others grow in the boiler industry and help solve some problems for our customers in the boiler industry. Because that's that's what it's really at the end of the day all about. Somebody calls you up, hey I got a problem, whether you're an engineer or whether you're a service company or whether you're a manufacturer. It's all about solving problems. And that's what the boiler industry
Eric Johnson (00:58)
is solving tons of problems. today I got a little bit more technical. This is really for my service technicians out there, although you can listen if you're not a service technician. I want to talk about the five key concepts of
Eric Johnson (01:14)
How to
Eric Johnson (01:16)
adjust burner linkage. And backing up, what is burner linkage? Burner linkage is mechanical linkage, mechanical rods and arms and jack shafts that move around from a single point motor from s one source motor and it's going to move multiple sources. It's on a natural gas burner is just going to be moving
Eric Johnson (01:43)
one motor, typically a Honeywell Module 4 motor, will be moving a gas butterfly valve and the air damper. this is a very common type of burner control, even though online if you look, especially on LinkedIn, it will say, if you have a linkage burner,
Eric Johnson (02:00)
That's ancient. It needs to be upgraded immediately. Nobody needs to learn linkage anymore since we have parallel positioning. Parallel positioning, if you're not familiar with, is a motor for each
Eric Johnson (02:13)
valve or a motor for each damper. So you're gonna have a motor for your firefly gas valve, you're gonna have a motor for your air damper. If it's dual fuel, you'll have a motor for your oil valve. And that's all controlled by a computer essentially, the computer being like a fire eye Nexus system or a Siemens L V five system. That's what parallel positioning is if you are not familiar with that. But I want to talk about linkage. Linkage still
Eric Johnson (02:42)
has a place. One, just all the existing stuff out there. There's a lot of existing linkage and what you see online typically are companies that are on the bleeding edge or companies that are reping big rep firms that are trying to push linkage list AKA parallel positioning systems and they're sometimes not naming any specific names, but I've heard and seen some
Eric Johnson (03:06)
slightly unethical ways of selling burner upgrades or telling customers that linkage is obsolete and they need to upgrade or saying something can't be fixed and only producing an upgrade and they'll say, Well, we're selling what's good for the customer and is it good for the customer or is it good for your
Eric Johnson (03:30)
your sales. And if there if if it maths out, that's great. But I have heard some sketchy stuff going on. But whatever. no matter of the fact, linkage is still a thing. Manufacturers still make linkage burners, especially on lower horsepower boilers. A fifty horsepower boiler can easily have a linkage burner.
Eric Johnson (03:56)
you know, somebody doesn't want to pay for parallel positioning, they'll throw on linkage still. Like I just saw a couple months ago a Cleaver Brooks integral burner, the typical fire tube with the integral burner on the front door, it was linkage. Brand new. So until all the boiler manufacturers stop producing linkage burners and all the rep firms and service companies say, Hey, we don't have any linkage in our territories anymore
Eric Johnson (04:24)
We have to learn linkage. And I am un under the opinion that you can't just walk in to a boiler room and see linkage burners and say, we don't work on that. You'll have to upgrade. Otherwise, that's ancient technology. That's you're essentially lying to the customer. For decades and decades service technicians and other people have understood how to work on linkage burners.
Eric Johnson (04:52)
It is not a terribly hard concept and it's not like you can't learn it. But if you have people who don't know how to do it and they just walk in and say, Nope, you gotta upgrade. This is obsolete. And then they just leave it at that and say, we can't fix it. This is obsolete. You are lying to the customer. And yeah, but you do you. I'm here to teach. And people tell me all the time, why are you teaching linkage? That's obsolete. Just
Eric Johnson (05:21)
Throw on parallel positioning every time you see it. Great. Even if I had parallel positioning in my back pocket, parallel positioning doesn't
Eric Johnson (05:29)
doesn't fix a problem at eight PM on a Friday night when you have to set up or adjust some linkage. So I wanna go over five key concepts and this may be a little different because a lot of people are like, I'm a hands on learner and I can only learn through seeing. Yes, but I'm gonna try to teach you linkage audio only. But I got five key concepts. A lot of linkage training is figure it out harder and I have worked
Eric Johnson (05:58)
Decently hard to make it so you don't have to figure it out harder, and that you need to understand some core concepts, and then once you understand those concepts, you'll be golden. And here are five core concepts of understanding linkage adjustment. So linkage adjustment really, there's nothing special about burner linkage adjustment, it is physics, it is mechanics. There's a thing called four bar linkage.
Eric Johnson (06:25)
That is like a mechanical property, but you don't have to learn all that. there's a lot lot of stuff that's like four bar linkage that's like typically it's not really anymore, but it's a form of it. But like steering racks on a car is a form of four bar linkage. older windshield wiper, like there there's a four bar linkage is everywhere in the world. And
Eric Johnson (06:51)
the same concepts apply to burn linkage, but these are five concepts that are broken down for people in the boiler industry they have zero math in And it is just you have to understand picture these concepts in in a way that makes sense to you. And once it makes sense to you, you'll never look at linkage the same again. Yeah. And this was me. The I'm I am speaking from experience because I used to be a service technician.
Eric Johnson (07:18)
And I used to work on linkage burners all the time. And I thought when I or initially saw linkage, my like I would walk into a boiler room and my heart would drop whenever I saw a linkage burner. Like, my gosh, I don't know how to work on this. And like hopefully the composition is good and hopefully everything's good. And when it was really out of whack, I'm like, man, and I would get so frustrated and so fearful of the burner because I'm like, I there's so much going on every time you make an adjustment.
Eric Johnson (07:48)
Everything else moves and h this is impossible. And then finally one day it clicked. And after that, it was like, let's rip all the linkage off. I I can redo it. And I used to work with some people who like, well, we gotta mark everything so we can put it all back correctly. I'm like, No, we don't gotta mark it. No, like once you understand the concepts, you can just throw it all back together. And a lot of linkage burners have been
Eric Johnson (08:14)
adjusted by people who don't know what they're doing and sometimes it's easier to rip everything off and to redo all the angles and everything and make it correct versus trying to adjust a poor adjustment from the beginning. So I'll stop blabbering about it and get to the core concepts.
Eric Johnson (08:37)
let me do some key definitions.
Eric Johnson (08:41)
These are just for me and this is for you, but this is what I call the things that are the parts, but you may call something different. Manufacturers may call something different, but I'm gonna try to keep it consistent on this podcast. I try to keep it consistent for my training. So we have a driver crank arm. That is the lever, that is the arm that is either coming off the mod motor, coming off a jack shaft. It is an arm with slots or holes in it. Then you have the receiver crank arm.
Eric Johnson (09:10)
That's also the arm coming off jack shaft or that's on the air damper or on the butterfly gas valve. The driver crank arm is the one that's powered. It is it is either powered directly from a motor or it's being pushed f by a connecting rod. A connecting rod is a rod that is going between the driver crank arm and the receiver crank arm. And this is
Eric Johnson (09:38)
a little bit hard to see until you see a burner with it, but you can't designate a driver crank arm or a receiver crank arm. Sometime depending on how you look at the burner and what linkage adjustment and angles you're looking at, an arm can be a driver crank arm and then in the next problem it can be a receiver crank arm, depending on how in depth the system goes. But I'm gonna try to
Eric Johnson (10:08)
explain that and hopefully you you can understand that and then so then you have travel. Travel is gonna be the distance something moves and since this is all linkage adjustment, we are rotating around a shaft or we are rotating around a motor shaft. So all travel is going to be in an arc. Everything's moving in an arc.
Eric Johnson (10:32)
These if you've seen burner linkage, everything moves in an arc. Valves will open and close in an arc because it's all based on a a shaft connection. The air dampers will all move in an arc. It's all based on a shaft connection.
Eric Johnson (10:48)
Building block one on the driver crank arm moving the rod connection farther from the shaft increases connecting rod travel distance. So what you have to visualize is a driver crank arm, which is going to be the arm and it's going to have some slots in it. Let's say two slots in it, and the connecting rod.
Eric Johnson (11:09)
is the rod that is going to connect at some point along those slots. And when we move the rod farther, so away from the shaft connection, it is going to increase the the connecting rod travel distance. So what I like to explain with this is when if you were to stand up and hold your arm out to your side
Eric Johnson (11:38)
And so your arm is gonna be level with your shoulder, your hand pointing out to your side, and now you move your arm in front of you, so your hand is pointing in front of you out from your chest. What has moved farther? Did your hand move farther or did your elbow move farther? So your your shoulder is the driver, the pivot point, which would be the shaft in this case. Let's say it could be a motor shaft. This is the powered
Eric Johnson (12:07)
Connection that's why on the driver crank arm, and your elbow and your hand are connected together. Your entire arm is the driver crank arm. But when you hold it out to your side, it's in one place, and then you rotate your arm to be in front of you. And now you can look at your hand, you can look at your elbow. Both of them are in front of you, but your hand moved
Eric Johnson (12:34)
a farther distance than what your elbow did, even though both are connected to your arm. Both are part of the driver crank arm in this case. So as you move farther from your shoulder, your hand is farthest from your shoulder, hopefully, if your if your arm is correct, your hand is farthest from your shoulder. And anytime you move your arm, if you if you were to hold something in your hand,
Eric Johnson (13:02)
It is going to move farther than if something was going to be connected to your elbow. Your elbow is going to move in a smaller arc than what your hand does. So even though they move together, when you swing your arm back and forth between pointing forward out from your chest and then over to your side in a horizontal manner, even though you're doing that, your hand is going to move in a f a farther distance, a farther arc.
Eric Johnson (13:32)
So when we are connecting a connecting rod to the end of our driver crank arm, or if that connecting rod would be connected to our hand, which would be the farthest distance away from our driving point, which is the shaft or sh our shoulder in this case, that is going to move the farthest distance. And then if we want that connecting rod to move less distance, we are going to move it towards the shaft.
Eric Johnson (13:59)
or towards our shoulder. So then, and this is what trips up a lot of people, building block two, once you understand that's that the driver crank arm on the receiver crank arm, moving the rod connection farther from the shaft decreases the arm's rotational travel distance. So this is the direct opposite of the driver crank arm. So a lot of people want to memorize the driver crank arm.
Eric Johnson (14:27)
And then automatically apply that to the receiver crank arm and they don't realize that there's a difference. So when you have a driver crank arm and a receiver crank arm, the driver crank arm is gonna move no matter what, even if the connecting rod wasn't connected to it, because it's a driven arm, it's powered. The receiver crank arm, it's gonna receive input or receive force from the connecting rod. So if you were to take off the connecting rod,
Eric Johnson (14:56)
And the receiver crank arm was on a valve, say the butterfly valve, the butterfly valve isn't gonna move. It may move just due to gravity, but say it's sticky, the it's gonna stay in one place. That receiver is never gonna move unless you reconnect the connecting rod to it. So they they operate in a different manner. So on this one, what you want to think about is
Eric Johnson (15:24)
pushing a door open. So let's say we have a door, you're gonna stand up to a door and you're gonna go farthest from the hinges and you're gonna push the door forward four inches farthest from the so where the handle is, you're gonna push your hand forward four inches. How far is the door going to open? It's probably gonna open just just a little bit, maybe ten degrees, maybe fifteen degrees, but you're just gonna crack the door open even though you push your hand forward forward
Eric Johnson (15:54)
four inches. You are farthest from the pivot point. So once again, going back to the building block two, on the receiver crank arm, moving the rod connection farther from the shaft decreases the arm's rotational travel distance. in this example, we're gonna have a receiver crank arm connected to a gas butterfly valve. So think about the gas butterfly valve shaft being the hinges of the door. So when you're standing in front of the door,
Eric Johnson (16:20)
And you're pushing on the handle when the handle is on the opposite side of the hinges, you push the handle four inches forward away from your chest. How much is are the hinges actually rotating on the other side of the door? The door moves four inches in front of you, the handle moves four inches away from you, but that door it the
Eric Johnson (16:46)
hinges are barely rotating. So if that door the hinges were actually a gas butterfly valve, it's gonna be barely rotating. Okay. So then let's go to the opposite end of that. Let's go to the left side of the door. If we're looking at the door front on, and the left side of the door we have the hinges. Now push four inches right next to the hinges. And assuming that the door is not super hard to open,
Eric Johnson (17:13)
Push for your hand forward four inches right next to the hinges. How far is the door gonna open? It's probably gonna open seventy, seventy degrees, eighty degrees, because you are now super close to the hinges and pushing against the door, even though you only moved four inches away from you, you are now so close to the where it pivots.
Eric Johnson (17:38)
On the receiver crank arm, or in this case on the door, that the door is going to travel a very, very far distance. So if we were to have a receiver crank arm on a gas butterfly valve and we were to move our connecting point or connecting rod all the way down towards the shaft, that connecting rod is being pushed against the receiver crank arm.
Eric Johnson (18:05)
So the power is coming from the connecting rod because it's a receiver crank arm. The receiver crank arm isn't going to move itself. But since it's all the way closest to the shaft and we push just slightly, the shaft is going to move a ton. Just in the same concept, in the way that if we push on a door right next to the hinges, with four inches of push, the door is going to open.
Eric Johnson (18:31)
A lot farther, significantly farther, than if we were on the opposite side and have the handle and we were only to push the handle four inches. That is the same exact concept. So once again, building block two on the receiver crank arm, moving the rod connection farther from the shaft decreases the arm's rotational travel distance. And that is exact opposite of building block one, which is on the driver crank arm.
Eric Johnson (19:00)
Moving the rod connection farther from the shaft increases connecting rod travel distance.
Eric Johnson (19:06)
Key concept three or building block three. Adjusting the connecting rod length moves the receiver crank arm's starting position without changing its rotational travel distance. So this is an important one and this trips people up all the time. So you have the connecting rod between the driver crank arm and the receiver crank arm, and the rod length needs to change sometimes depending on.
Eric Johnson (19:33)
If you are going to be moving your connection along the arm and you want to keep the same point on your receiver crank arm. So between two points of the arms, if you were to move the connection on the receiver crank arm away from the shaft or towards the shaft, the actual distance, if you didn't change the length of the connecting rod, the actual distance is going to change.
Eric Johnson (20:01)
And it's either going to open or close your gas butterfly valve in this case. It's either gonna open or close your gas butterfly valve. So you need to adjust your length of your connecting rod. Well, what a lot of people do, and I struggled with this, is they will try to adjust their connecting rod length to try to make up for where.
Eric Johnson (20:29)
if they need less gas, they're gonna say, I need to shorten my connecting rod. And that's not always the case. And it doesn't actually change how far or how much the gas butterfly valve in this case opens. It's only gonna change where it opens. So if you have your receiver crank arm and it opens your gas butterfly valve from zero degrees
Eric Johnson (20:59)
to 60 degrees. So we have total degrees of travel will be 60 degrees of travel. If we adjust our rod length to now be longer and say now we have 20 degrees extra that we've adjusted into it. So now our starting position is going to be 20 degrees instead of zero degrees. So our gas barfly valve is going to be 20 degrees and we're the ending of it is going to be 80 degrees.
Eric Johnson (21:28)
So we still have the same amount of rotational travel. So instead of zero to sixty, we're now going 20 to 80. We didn't change how much it's gonna open. So it's not gonna go 20 to 60 now. It's gonna go 20 to 80, just like it was doing zero to sixty. So when you are adjusting the rod length, if you're trying to make a gas butterfly valve open less.
Eric Johnson (21:57)
Just adjusting the rod length is not gonna do that. You were just moving that
Eric Johnson (22:03)
span of how much it opens or closes or moves, you're just moving it along the opening process or the closing process.
Eric Johnson (22:12)
So once again, if if you were to have a receiver crank arm set up with a certain connecting rod length of whatever, and you tested everything out and it went from your your gas butterfly valve went from zero degrees to sixty degrees, you're like, well, we need more gas. We need to make an adjustment. But at sixty degrees at high fire, let's say, you you had good fuel. So if you just adjusted your connecting rod.
Eric Johnson (22:40)
To try to get more fuel on the low end since it was at zero degrees, you are now adjusting your connecting rod only. You're sliding that scale up. So you're going to 20 degrees and 80 degrees, but now you're good at 20 on low fire. You've changed your connecting rod length and you're like, great. And then you slide it up to high fire.
Eric Johnson (23:05)
But now you went past sixty and now you're all the way at eighty. You're like, whoa, whoa, whoa, way too much fuel. And now you're going back and forth of like, wait, I made my connecting rod length different and it made low fire good, but now high fire is too much. And you go back and forth of like, wait, every change I do adjust something else on the curve and now you're struggling. And a new person would go back and try to change the adjusting the rod length again.
Eric Johnson (23:35)
And what they really need to do is change the connection along the receiver crank arm or the driver crank arm to be different so that they either open up the degrees of travel or close down the degrees of travel. And and we'll talk about that. But what the building block three, all you need to know is adjusting the connecting rod length moves the receiver crank arm's starting position without changing its rotational travel distance.
Eric Johnson (24:04)
Typically, when you're making linkage adjustments, you're gonna have to make two adjustments. You're gonna have to adjust the connecting rod length, and you're gonna have to adjust the
Eric Johnson (24:15)
connection along the receiver crank arm or the driver crank arm because in order to keep a valve or a damper in the correct position if you slide a connection along the arm you have to adjust the connecting rod length to either be longer or shorter to keep the
Eric Johnson (24:35)
damper or valve in the correct spot.
Eric Johnson (24:38)
Building block four, when both crank arms are parallel and connected at equal distances from their shafts, the receiver crank arm matches the driver crank arm's speed and travel throughout the entire stroke. A lot of people call this like the one-to-one relationship. So when you have a complicated linkage system that is probably dual fuel, but it doesn't have to be. But sometimes with a jack shaft, typically they'll have a jack shaft, but you have multiple arms and jack shafts.
Eric Johnson (25:08)
of connecting linkage, all the linkage that connects from the modulation motor, w whether that's the Siemens motor or the Honeywell motor, whatever motor that's used to drive the single point positioning system, which is the linkage system.
Eric Johnson (25:26)
All the linkage in between except the last two connection points on the air damper and on the butterfly gas valve in this example, or it could be the oil valve, all those connections are just to travel or to connect or to transfer the movement from the motor. They are not for adjustment.
Eric Johnson (25:49)
So if you're setting up a linkage burner and you're trying to adjust the air fuel ratio, you are not going to be making adjustments that are near the motor or in between all those linkage connections around the jack shaft. You're gonna be making your adjustments at the final points on the receiver arm and the connecting rod that is closest to the butterfly gas valve and to the air damper.
Eric Johnson (26:19)
All the other points are for travel and you may have to adjust them and not make them a one-to-one relationship, but typically it's easiest if if you just do a one-to-one relationship. So on a Cleaver Brooks integral burner, the a Cleaver has it, they they actually have a diagram that will tell you the angles that you should put all the arms at,
Eric Johnson (26:43)
Depending on the size of the burner, the motor will either be above or below the jack shaft. And Cleaver wants a one-to-one relationship. So if you have a drive crank arm and you put the connecting point on the arm all the way at the end, the one-to-one relationship would be you have the same exact length receiver crank arm and you would put the connecting rod all the way at the end of the receiver crank arm.
Eric Johnson (27:09)
And what this does is it makes the driver crank arm and the receiver crank arm parallel. And now since they're parallel on how four bar linkage works is the driver crank arm and the receiver crank arm will move at the same travel speed and distance along their path. So it is how you directly transfer the modulation motor movement into further linkage.
Eric Johnson (27:39)
And you have to understand that because it's not next concept is probably the most hardest concept to understand about setting up linkage burners. But first I want to make sure building block four is what you understand. When both crank arms are parallel and connected at equal distances from their shafts, the receiver crank arm matches the driver crank arm speed and travel throughout the entire stroke. And that is typically going to be used
Eric Johnson (28:09)
In transferring the movement of the motor along the linkage system until the final endpoints when you're closest to the valve or the damper, where the final adjustment comes in and where you start getting weird is when you're closest to the valve and damper, and you start having to adjust and to say, all right, well.
Eric Johnson (28:38)
I have one motor that goes from zero to ninety degrees. My air damper I need to make go from 10 degrees to 80 degrees on my air damper. And on my gas butterfly valve, I need to make it go from five degrees to 60 degrees. So how do you do that when you have a motor that only goes from zero to ninety degrees? You the motor goes from zero to ninety no matter what.
Eric Johnson (29:08)
Zero degrees is low fire, 90 degrees is high fire. That's set. You can't change that. And that's on typical burners. Sometimes you can have a 160 degree motor, but I'm just talking about typical burners are zero to 90 degrees for single point positioning. So how do you do that? How do you make all this stuff is mechanically connected together, but my air damper moves a farther distance than what my
Eric Johnson (29:38)
Butterfly gas valve moves. So this is going to be building block five. So when crank arms are set at different angles, an arm rotates fastest at 90 degrees to the connecting rod and slows down as the angle flattens. And this is going to be
Eric Johnson (29:52)
how much the shaft of the butterfly gas valve or of the air damper move and how fast they open. So you'll always hear somebody say, hey, your gas is too fast or your air is too fast. You need to slow it down. It's like, well how do you slow it down? Because I have a mod motor that moves in 30 seconds from zero degrees to ninety degrees
Eric Johnson (30:23)
And it doesn't change speed. How am I changing the speed of my air damper and my gas valve in relationship to each other when the when they're all connected to the same motor? This is how you do it. So your you have to understand and look at the angle of your receiver crank arm and your driver crank arm, but I'm just going to talk about the receiver crank arm. But the receiver crank arm and your connecting rod, the angle they make.
Eric Johnson (30:51)
So if they're at ninety degrees to each other, if you look at a receiver crank arm and the connecting rod to it, if they're at ninety degrees to each other, that is going to be the fastest point in the in the arc that it's going to move. And if you are approaching the ninety degree mark, you're gonna be speeding up the opening. If you are moving away from the ninety degree mark, you're gonna be slowing down the opening.
Eric Johnson (31:21)
So if you set up your gas valve to slowly open on low fire and you have it, the connecting rod set at low fire at ninety degrees, it that is going to be the fastest it is going to open. That that is gonna peak. So for every degree of travel that your modulation motor is moving or opening and adjusting or turning the linkage system, your
Eric Johnson (31:51)
Butterfly gas valve is going to open very quickly because your connecting rod and your receiver crank arm are at ninety degrees to each other. But if you change it and you said, all right, we're gonna adjust everything and my receiver crank arm and my connecting rod are now gonna make an angle and it's gonna be at thirty degrees to each other.
Eric Johnson (32:19)
And so they'll make a 30 degree angle. And now it's going to open up or as it rotates, it's going to move up to 90 degrees. So when you go 30 degrees and you're moving towards 90, the 30 degree is going to be slowest in relation. And then as it arcs up towards the 90 degrees, it is going to get faster. It may not get to 90 degrees, depending on the travel and how everything's set up.
Eric Johnson (32:48)
But it is going to get faster. So your butterfly gas valve in this situation is going to start slow because you have it set at an angle, the connecting rod but and the receiver crank arm, that connection is going to be set at a small angle and is going to be moving up towards 90 degrees. But if you were to do it opposite and you were to say, All right, I'm going to set my air damper to be
Eric Johnson (33:15)
Quick on the low side and then slow down because as the air damper opens, the how the the curve of the air damper, I don't need as much travel at the end. So you're going to say set the air damper at
Eric Johnson (33:34)
Seventy degrees.
Eric Johnson (33:36)
And it's gonna open up through ninety and keep going. So you set it at seventy degrees, the receiver crank arm on the air damper and the connecting rod, the angle between them, you set it say at seventy degrees, and this is all relative. You're never gonna get out a protractor and like actually make it, but it's all relative to each other. You're not actually measuring degree angles. You can measure it, but I've never measured this degree angle. I only measure
Eric Johnson (34:04)
the angle of degrees sometimes with a digital angle finder of the actual arms. But the receiver crank arm and the in the connecting rod angle, you let's say it's at 70 degrees and it's moving up through 90 where it's going to peak. So it is going to be slower than the 90, but it's still going be relatively quick i when it's opening. So as the burner lights off and it's going from low fire to high fire,
Eric Johnson (34:30)
It is going to speed up the opening of the air damper. As it passes through 90 degrees, and the receiver crank arm keeps sweeping open, the bigger the angle gets, 100, 110, 120 degrees, the bigger the angle gets, as it flattens out towards 180 degrees, it will never make it to 180. But as it flattens out, it is going to slow down the opening of the air damper. And
Eric Johnson (34:58)
depending on the your air damper size and everything, you can make it so that the air damper will open relatively quick at the start. It's gonna peak at 90 degrees, how fast it's opening, and say three-quarter firing rate, your air damper is going to be pretty much almost all the way open. And the difference between three quarter firing rate and a hundred percent firing rate
Eric Johnson (35:27)
The air damper is gonna slowly open, just barely a little bit more, because of how you set it in this case. I'm not saying that's gonna be the case all the time, but that this is just the example. And this is by far the hardest concept for people to understand once they realize and get past the first two building blocks of the driver crank arm and the receiver crank arm, they moving away or closer to the connection point.
Eric Johnson (35:55)
is different and opposite of each other. This is by far the hardest part because and I struggled with this. I'm like, how do I make my butterfly gas valve open faster when it's directly connected with this motor that moves at the same speed? This is not possible. Well it's you have to adjust the angle of your driver crank arm and your receiver crank arm so that they're not parallel to each other.
Eric Johnson (36:25)
Which will then adjust the connecting rod angle to the receiver crank arm, or you can do it on the driver crank arm. You'll have to typically do both, but for this example, I'm just only talking about the receiver crank arm and the connecting rod angle. And you'll make your connecting rod longer and you can change your angle. So then therefore it'll make the angle smaller. You'll have less degrees.
Eric Johnson (36:51)
So once again, like say 30 degrees, and if you're having 30 degrees and you move up towards 90, it the valve or damper is gonna start slow. And as you approach 90 degrees between the connecting rod and the receiver crank arm, it'll move faster. So it's gonna go from slow to fast. But if you and I've seen people do this and I've done it myself, but if you set your
Eric Johnson (37:19)
receiver crank arm on a gas butterfly valve and your connecting rod at 90 degrees and you set that at low fire and you're like, all right, I'm good to go. Let's light this off. And you adjust the connecting rod length so that you have low fire good and you're like, all right, let's start modulating up. And you barely hit the potentiometer, the manual potentiometer on the burner. And
Eric Johnson (37:47)
The mod motor barely moves, your air damper barely moves. Yet since the connecting rod and the receiver crank arm are at ninety degrees, your connecting rod moves just a little bit, but it is going to open up. That is going to be the fastest part of the arc. And your butterfly gas valve is gonna open up a lot in relation to your air damper and you're gonna go rich on your O two and probably
Eric Johnson (38:16)
spike your CO and have to run and remove your combustion analyzer probe from your stack and you know, freak out and then get
Eric Johnson (38:25)
confused and start complaining that you can't learn linkage. But there is a light at the end of the tunnel if you just know those five building blocks. And I know I don't think anybody's ever tried to explain setting up burner linkage on a podcast, but I'm attempting to do it. Hopefully you understand some of this. You can write down these building blocks. I will go over them again.
Eric Johnson (38:51)
I'll also put them down in the description. That's a good idea. I'll put them down in the description. And you know, you can copy paste those, screenshot them. I will have more resources coming out soon-ish on burner linkage adjustment. So if you're interested in that, let me know. Building block one on the driver crank arm, moving the rod connection farther from the shaft.
Eric Johnson (39:16)
Increases connecting rod travel distance. So this is going to be holding your arm out to the side, and your shoulder is the power to your arm. Move your arm in front of your chest horizontally. Your hand is going to move a farther distance than where your elbow does. On the opposite of that, building block two, on the receiver crank arm, moving the rod connection farther from the shaft decreases the arm's rotational travel distance.
Eric Johnson (39:45)
To in order to learn this or visualize this, go stand in front of a door, push the door handle four inches away from you, go stand on the opposite side of the door where the hinges are and push the door, assuming the door isn't a super heavy door, push the door forward four inches and see how how much farther it opens based on the same amount of push. You've only pushed four inches with your hand.
Eric Johnson (40:10)
You have the door when you are closest to the hinge is gonna move the farthest. This is also if you guys, and hopefully you do, but if you guys use a pipe wrench or use wrenches to take off nuts and bolts, if you have a 36-inch breaker bar on a lug nut and you are pulling at the end of the breaker bar and it breaks loose, and you use that 36-inch breaker bar, you are trying to
Eric Johnson (40:39)
Lift it above your head and then you push it all the way down to the ground, and then you lift it above your head and you push all the way down to the ground, and you are moving the breaker bar in this huge arc. Yet you're barely turning the lug nut. But if you get a little twelve inch wrench, now that it is broken loose, you get a little twelve inch wrench, you can move your hand just in a little small half circle.
Eric Johnson (41:04)
And do the same amount of work that you were with that 36 inch. It's because you are farther away from the rotation. Same thing with the door. If you push the handle, you are farther away from the rotation. So even though you're doing the same amount of work, the door is going less. And that is for the receiver crank arm. Building block three, adjusting the connecting rod length moves the receiver crank arms.
Eric Johnson (41:29)
starting position without changing the rotational travel distance. So once again, if you need to set up where your valve is going to start, you can adjust the connecting rod length. However, if you need a valve to open less degrees or if you need a damper to open less degrees, just adjusting the connecting rod length will not do it because you are sliding the
Eric Johnson (41:56)
The amount of degrees you're sliding it along its rotational travel distance. So instead of zero to sixty in this example, we're going 20 to 80. Adjusting the connecting rod length doesn't make the your butterfly gas valve open less or open farther. It just slides where it opens along its travel distance. building block four.
Eric Johnson (42:21)
When both crank arms are parallel and connected at equal distances from their shafts, the receiver crank arm matches the driver crank arm speed and travel throughout the entire stroke. This is the one-to-one relationship on linkage. And this is typically how it's preferred to transfer the power of the mod motor along linkage on larger burners until you get to the farthest endpoints. One-to-one relationship because you're
Eric Johnson (42:49)
taking the full speed of the motor and you're not speeding it up or you're slowing it down and you're just transferring it without trying to modify how much the linkage moves, whether it moves more or moves less. And this is going to be both crank arms, your driver and receiver, are going to be parallel to each other. And the connecting rod is going to be equal distance from the shaft. So typically it could be all the way out or it could be at the midpoint on your
Eric Johnson (43:18)
Driver and receiver crank arms, but when your mod motor moves forty five degrees, your receiver crank arm is gonna move forty-five degrees at the same amount of speed. And then building block five. When the crank arms are set at different angles, so aka not parallel, an arm rotates fastest at 90 degrees to the connecting rod and slows down as the angles flatten. So the ninety degrees
Eric Johnson (43:47)
Is going to be between the connecting rod and the driver crank arm or the receiver crank arm. That's where it's going move quickest. And if as you move away from 90 degrees, it's going to slow down. If you move towards the 90-degree angle, it's going to be speeding up. So on a gas butterfly valve, you're typically going to have a very acute angle or small angle. So say 30 degrees, and you're going to slowly
Eric Johnson (44:16)
open your gas butterfly valve on low fire and then it's gonna open up faster as you get towards high fire and that's just because the curves and the physics of a gas butterfly valve and you'll do something different on your air damper depending on how your air damper behaves and the size of the burner. But that is what you need to
Eric Johnson (44:41)
No, in order to adjust and understand linkage, if you're trying to memorize linkage adjustment, you are already doing it wrong. I tried to memorize linkage adjustment. I've seen other people try to memorize it. There's no memorizing linkage adjustment. You have to understand it. And what had really helped me to understand it is I made it large in my mind. And I always related it back to forty eight inch pipe wrench versus a twelve inch pipe wrench and on a pipe.
Eric Johnson (45:11)
And if you've ever used a 48-inch pipe wrench and you're loosening something, you take it from above your head and you're swinging it down to the floor and you're doing all this work and like you know you're struggling, you're using a 48-inch to try to, you know, get a two-inch pipe apart that's really stuck, and you're swinging it from above your head all the way down to the floor, yet the
Eric Johnson (45:33)
pipe has barely moved a hundred degrees. It's barely turned. So it it it gets exhausting. But if you have a little brand new half inch pipe and you're using a 12 inch pipe wrench, you can just swing your your fist in a little arc and you're doing a ninety degrees of motion in a little arc. It's because you're much closer to the pivot point. That's the same concept with the door.
Eric Johnson (46:01)
But when I when I was thinking about linkage, it's like, okay, if I'm moving away from the pivot point on the receiver arm, if I use a 48-inch pipe wrench, okay, let's blow this up. 48 inch I'm moving away from the pipe, I'm gonna be moving a huge distance to do a little bit amount of work. But if I move towards the pipe, I'm gonna be moving a much smaller distance to do the same amount of work. And that's that's what really helps me.
Eric Johnson (46:30)
Is making everything big because linkage adjustment burners are very, very finicky, and sometimes you can breathe on linkage and make a burner run rich or lean. And you know you'll learn that. But linkage adjustment is an imperfect art, but it is still an art. And if you just make the problems really big, it's like all right, if I just move this connecting rod out slightly.
Eric Johnson (46:57)
Like what would happen if I move this connecting rod three feet this way? And it's gonna be the same concept, but it's gonna be a much smaller change. So if you're like, all right, if I move this connecting rod all the way out from this arm, what is gonna happen? Okay, great. Well, that's what I wanna happen, but I just need it in a smaller amount. So I'm just gonna only slide this connecting rod along this arm just a touch away from the shaft, but I know
Eric Johnson (47:26)
what's gonna happen since I blew it up in my mind versus well I'm gonna make this little change, I have no idea what's gonna happen because I can't visualize this tiny little change that I'm gonna make. And that's where I really struggled is trying to visualize these tiny little changes. But once I made everything huge in my mind of well if I make this giant change, what's gonna happen? The same change is going to happen just at a smaller amount of rate or smaller amount of change.
Eric Johnson (47:56)
when you go to make that little adjustment.
Eric Johnson (47:58)
But stick with it. I will have more resources. Go look in the description for all five building blocks. And I will have those in the description so that you can copy them. And if you have any questions or want to talk about this more, I am always open to trying to explain linkage better. And I'm really trying to get it so that people have something to hold on to versus
Eric Johnson (48:24)
Well, they just need to figure it out, or they just need to memorize harder because telling somebody who doesn't understand and is confused to figure it out or memorize harder or it's not that hard. Why don't you get it? That is not helpful conversation. That leads to frustration and that leads to people not adjusting linkage or fudging linkage and combustion points so that it looks good, but it isn't really.
Eric Johnson (48:52)
And that is no good because now we're sooting up boilers when we don't need to be sooting them up. And that gets expensive and it's no fun for anybody. So that's what I have for today. Let me know if you're totally confused, if this was just a waste of an episode. I've spent a lot of time trying to write out these building blocks, the five of them. I think I'm the first person to ever do that. But it is the concepts are nothing new.
Eric Johnson (49:17)
But it's trying to make the concepts in a easy to understand way for burner guys or gals to understand how to adjust linkage and not feel alone in the boiler room when they see a linkage burner and have to adjust it. So that's all I have for you. I appreciate you all for listening and stay wild.
