Quote from: jurelometer on March 06, 2025, 01:00:32 AMNice snakehead!
The benefit you are reporting from adding an inner drag washer is puzzling.
Increasing the surface area does not increase the amount of sliding friction. So something else must be going on here.
The formula for sliding friction is simply the coefficient of friction for the two surface multiplied by the load pressing them together.
The amount of braking work per revolution is a function of distance traveled, which is the "average" circumference of the disk from inner to outer diameter. With a single drag washer, the larger the hole, the greater the amount of braking work per revolution for the same clamping load. This is one reason why they put larger rotors and not larger pads in performance car brakes.
This modification appears like you are making the hole smaller.
Here is one theory: Since the drag washers are not keyed or eared, they are capable of sliding against the face on either side. If it happens that one drag washer slides on the outward face, and the other on the inward face, you will get two drag surfaces for the same clamping load, and since one has a much smaller diameter, about a 20% improvement seems about right.
But if over time, they eventually both start sliding on the same side, you will see a decrease in drag over the single large washer, as you have decreased the "average" diameter. I guess that you could treat the surfaces with different substances to encourage the desired behavior.
Or if the drag star was bottoming out originally, if any new drag washers are a bit thicker, you may be simply adding more clamping load.
Or a fresh drag washer might increase the coefficient of friction.
Intentionally adding more clamping load can be also an option if the star threads are up for it. If the star is bottomming out, you can add an extra spacer washer or two, but you may lose the ability to loosen the drag all the way.
Note: I put "average" in quotes, because there is a proper formula for calculating surface distance traveled per revolution of a disk using inner and outer diameter. I think that I might have put this in another thread, but interested folk can find it by searching the web for velocity calculations for thrust washers.
Hope that you find this useful,
-J
I wanna discuss this further but I don't wanna derail the other thread.
I can't help thinking that the equations I stumbled across when searching the terms suggested above are one of those useful approximation type things that don't capture the full story. Newtons second law wasn't F=MA but that approximation holds up until things get really big or small, etc. I want to dig deeper.
For starters I'll very reasonably assume the laws of physics don't care that I disagree with an equation. Great jump off. But the universe doesn't live on a chalkboard. These frictional forces are acting on real materials that get hot and properties change with added heat. More surface area, and just really.more mass of the drag disk in general probably becomes a consideration.
And let's take the idea to the extreme. A drag disk that resembles the cross-section of a paper towel tube. Really get that average diameter out as close as possible to the outer diameter. This is a thought experiment so we'll briefly ignore the difficulty of giving a woven material of those dimensions any structural integrity. And we'll also briefly ignore the need for far tighter machining tolerances to maintain consistent pressure (I believe we've discussed this element before). Would this really perform better on a drag test? And if so are we talking about max drag at startup? What about smoothness? What about drag performance after something takes a 200yd sprint away from the boat (and gets it hot)?
As I think about this I find I'm actually fairly well situated to test this out. In all but the free time. By that I mean I have a set of hollow punches and sheets of carbon. I'd be interested in testing the rolling resistance of a reel with the entire drag surface area covered with carbon, and then test again at same setting with disks from the same sheet cut to the same OD but a much larger ID.
Would you expect to see increased max drag when cold? What about max rolling resistance after equal # of turns of the star? (I may not be using the right term. By that I mean comparative resistance while line is being pulled out at constant speed)
Oh and one last hail Mary. Say I took a made a drag disk that looked like a bullseye. Picture a bunch of nested thin concentric rings in place of one ring. I am reasonably assuming they all spin in unison and all stuck to the same side. If I calculated the braking force based on the average diameter of each ring, I just struggle to picture how the total braking force wouldn't be the sum of those values. And if so I struggle to see how that number would be increased by removing a couple of the inner rings.
I hope this doesn't read like I'm writing hate mail to the laws of physics but putting Dave's name on the address line. It just seems like a fun topic, and one where the received wisdom seems to contradict logic and some (admittedly less than rigorous) observations so to me, it's worth the challenge.
Sliding friction is not a function of surface area. so it doesn't matter if you add more surface area or how many pieces the surface area comes in. In very crude (and not 100% scientifically correct) terms, if you increase the surface area for the same compressive force- that force is pressing less per square inch of surface, so you end up back at square one with the same amount of friction.
There are different static and kinetic coefficients of friction for sliding surface pairs. they both can change with heat. in the case of greased or ungreased CF, the CoF will decrease with heat, more with grease if I remember correctly.
And before you ask about thermal expansion increasing the clamping load- we covered that here in another thread, and came to the conclusion that it was negligible.
Braking in this case is like braking on a car. The spool is slowed by changing kinetic energy into heat energy. The amount of energy transformation will be the product of the amount of friction and the distance travelled. if you dragged a brick a mile down the street it will get hotter than if you just dragged it a few feet.
But the path traveled on your drag disk is circular. The larger the circle of travel, the more braking work per revolution. These circular paths start out smaller from the inner diameter and gradually get larger toward the outer diameter, so you have to use an equation to sort of average them all out. This is a classic example of needing a integral equation. The formula is out there, but I am too lazy too look it up again. I think that I already posted it.
By making the center diameter larger, you are increasing the effective circumference. Orvis (and some others) tried playing this game by putting a very large OD drag disk with a very large ID (looks like a ring) on a fly reel design. More drag for less clamping pressure. But since the braking surface is farther from the axis, any angle off axis on the surfaces creates greater travel and therefore more chatter and stickiness. There are other downsides as well. I don't think any of these were that successful.
IMHO, the better reel designs go for larger OD drag washers with larger IDs, but not getting crazy about it.
Tribology is often counter-intuitive and there are lots of exceptions to the rules. And I don't claim to really understand any of it very well. But we are dealing with a fairly simple case here and are not trying to get very exact numbers.
-J
(https://alantani.com/gallery/35/17471_03_11_21_2_17_50_357451123.jpeg)
It's "Hail Mary"
Interesting topic —-
For me, it boils down to using the proper sized reel to match the target species.
From Dave (jurelometer):
"IMHO, the better reel designs go for larger OD drag washers with larger IDs, but not getting crazy about it."
This is why one of the highest quality DAM Quick reels are the 1401 thru 5001 series. They use a set of very large drag washers both on top and underneath a metal skirted spool. This evenly "squeezes" the spool to add drag pressure when fighting a fish —- it is very effective. Add a thin coat of Cal's —- and it is even smoother, and still has complete drag pressure from "0" to lockdown.
A danger in over dragging reels, particularly spinners —- is that the drag might over-reach the physical limitations of the frame and some other components —- and cause a reel failure or stress twisting.
And here again, don't expect the reel to do all of our work —- just as important are proper rod-handling techniques, an awareness of the mechanics of our reels, knowing exactly where and when to make adjustments when fighting a fish without looking, and experience.
Sometimes, we just need to hit the light switch —- and all of the theories & principles of electricity are not needed to do that.
Good topic!
Best, Fred
Another way to look at it is that points farther from the center will generate more torque for the same amount of friction. More of your braking surface farther from the center (larger ID) means that the frictional resistance will be distributed amongst points on the disk with greater torque.
Here is a good overview:
https://mechanicsmap.psu.edu/websites/7_friction/7-6_disc_friction/discfriction.html (https://mechanicsmap.psu.edu/websites/7_friction/7-6_disc_friction/discfriction.html)
Things to also consider are vibration dampening for certain materials (e.g., cork) PV ratings for certain materials (Rulon, Delrin), heat conduction and convection. These will all be affected by combinations of diameter(s) and surface area.
And the reel has to be designed to be capable of keeping the sliding surfaces aligned at the chosen disk OD.
I don't claim to have anything more than a not-quite-rudimentary grasp on this stuff, so if someone out there has some training in this field, I am all ears.
-J
That makes sense.
But, it seems to me, the difference in a new drag washer(s) and old drag washer(s) is as dramatic as the difference in configurations. I guess Carbontex is the state of the art, but it doesn't stand up for long. You can tell the difference after one good fish fight.
I keep wanting to come back to this but it's been a very busy week. And weekend. Didn't wet a single line though.
I will throw this out there though. A lot of what Dave is saying is basic physics and I'm not arguing it. I remember the analogy of a cereal box full of concrete. There's 3 different sized sides to choose from but the weight is the same. It would just be distributed differently depending which you slid it on. But that's basic physics. Get into statics and dynamics and classes and they start talking about where is the mounting point and angles of pull, etc. Also, and this is relevant, on any real world surface I know which side of the box would result in me starting to consider the coefficient of friction of concrete instead of cardboard first.
Even if initially, conceptually, they might read the same on a spring scale while you pull.
I still owe a better response but I needed to get something out there.
Also because F= mu N is a hyper-simplification of friction that is taught to 15 year olds. Amontons Second Law applies quite well to a block of wood on a ramp but is not great for many other real-world applications.
(https://alantani.com/gallery/38/17471-081023145622-383432237.gif)
The basic law of sliding friction is useful for a basic understanding, plus it is where you need to start. The engineers that design race car brakes care about all sorts of fancy stuff around friction, presumably with a focus on very large changes in heat. But they still use a frictional surface concentrated on the perimeter of a large disk because the basic law of friction is still in play.
If we want to get into exact numbers, then I agree it gets more complicated, but we are not yet in a discussion about exact numbers. We are discussing simpler stuff, and trying to decide if we can accept the basic law of sliding friction because it seems so counter-intuitive.
If we want to start going down the rabbit hole of more advanced friction, I would start here:
The reel in the thread that started this debate was using dry drags, but most of us grease the drags. Under pressure and/or heat, the grease liquifies temporarily and becomes a liquid film. And the hotter the temps and the greater the pressure, the lower the viscosity. Now we have friction in a fluid to deal with, which is a function of surface area contact. But since the carbon fiber surface is so irregular, it probably is not a straightforward fluid surface film situation. Heck, it might be some sort of quasi- fluid/ non-fluid combo. I did a bit of reading on fluid friction for lure design purposes, and learned enough to know that if you want to go on this journey, it will be without me. I know my limitations. :)
-J
I am doing my best to keep this discussion in the conceptual range, and avoiding it going off the rails. I want it to stay interesting but I recognize it can get tedious fast. I wish we had a subforum for "excessively technical/advanced general topics"
Joe, do you have a decent spring scale I can borrow hiding behind those animated gifs? Mine was at best decent before it got rusty, now it's by no means suitable for anything scientific. I wanna do some testing.
Dave, I wanna circle back to an aspect of the original discussion. Taking as a given that OP really did see an increase in drag by adding the inner washer for the sake of discussion. You suggested that it might be due to it mating with/sticking to the opposite side thus creating an additional drag surface. But that drag surface is at a smaller diameter so my question is why would that matter if a drag disk sliding at a given diameter was happening in one side of the system or the other? And why would it change if the new drag disk started sliding on the same side as the other one?
Also, a case study. If you take a 9/0 senator and swap the stock drags for an aftermarket dura-drag setup with the eared carbon washers you are keeping the same number of stock drags disks but eliminating the outer half of the diameter as an active surface, in exchange for getting both sides of the drag disk to be active. So you are trading diameter for surface area. Those kits see absurd increases in available drag without even cranking the star down all the way.
The plural of anecdote isn't data. But this observation that stands in direct opposition to the principle being evaluated has been done and quantified enough times for it to seem very relevant.
I promise none of this is a "gotcha" type thing and I'm not seeing this as an opportunity to prove anyone wrong. We're all just in pursuit of truth.
Yes I do , and you are welcome to use them .
Back to this drag set up .. It`s easy to see why it worked .
Just read a post by Allan T. mentioning that a digital wt. scale should be more accurate than the spring types. Digital scales can be used to calibrate the spring type.
Does a digital scale require constant calibration? What about putting alota weight force on a digital scale, does anyone know if that messes with calibration?
Looking for a new one after breaking mine...
Hey Jason:
The original guy could have gotten more drag because the new material was thicker and he could tighten the drag more. Or it could have been fresh CF with a higher CoF. Lots of stuff to look at before discounting the basic friction formula.
Regarding stacking washers: if the drag surface pairs in combination are independent of other drag surface pairs that share a common clamping load, then the effect is additive. This one stumped me at first too.
Regarding testing: measuring drag is not enough. You also have to measure clamping load. Measuring the torque on the star could be a rough stand-in unless the amount of lubricant on the threads changes a bit. Then the ratio of torque to clamping load changes, and your estimate is going to be even farther off.
And lots of other things to look at like a common break-in period on the fresh drag, or even better measuring the CoF before testing.
Getting a result that you can have faith in it is actually pretty hard.
-J
Quote from: jurelometer on March 10, 2025, 02:05:23 PMIf we want to get into exact numbers, then I agree it gets more complicated, but we are not yet in a discussion about exact numbers. We are discussing simpler stuff, and trying to decide if we can accept the basic law of sliding friction because it seems so counter-intuitive.
That's kinda my point. There is probably very little point in trying to apply the very basic "laws" of friction because they are only true for a very "pure" setup, which the drag in a reel is not. Starting with first principles of friction is useful for a theoretical exercise, but not a practical one.
Quote from: boon on March 10, 2025, 09:56:12 PMQuote from: jurelometer on March 10, 2025, 02:05:23 PMIf we want to get into exact numbers, then I agree it gets more complicated, but we are not yet in a discussion about exact numbers. We are discussing simpler stuff, and trying to decide if we can accept the basic law of sliding friction because it seems so counter-intuitive.
That's kinda my point. There is probably very little point in trying to apply the very basic "laws" of friction because they are only true for a very "pure" setup, which the drag in a reel is not. Starting with first principles of friction is useful for a theoretical exercise, but not a practical one.
You left out this preceding part:
Quote from: jurelometer on March 10, 2025, 02:05:23 PMThe basic law of sliding friction is useful for a basic understanding, plus it is where you need to start. The engineers that design race car brakes care about all sorts of fancy stuff around friction, presumably with a focus on very large changes in heat. But they still use a frictional surface concentrated on the perimeter of a large disk because the basic law of friction is still in play.
My point is that the basics of friction don't just go away, because the reality is more complicated. They still teach the basics for a reason.
We are looking at variance in kinetic energy transferred to heat from changing inner and outer diameters of dry sliding flat rotational friction surfaces with the same clamping load and coefficient of friction. But not down to any significant precision, just as general working knowledge.
And it seems to me that a single dry drag disk/washer pair on a reel is a fairly simple case if we are only trying to answer these basic questions. But that is maybe because I am only aware of the simpler parts of the physics involved.
If you can enlighten me/us beyond a general statement that this is not a practical approach, I am all ears.
-J
:) The way I look at it , is there is no constant drag number in the stack on a working fishing reel .
The working diameter of the spool is changing and the gear ratio of the reel weather it be 2 to 1 or 4 to one or even higher ratios change how the drag works at giving spool diameters . I should say this is before the dog kicks in to play .
I think lever drags maybe more forgiving ..
:d
Quote from: oldmanjoe on March 10, 2025, 11:42:48 PM:) The way I look at it , is there is no constant drag number in the stack on a working fishing reel .
The working diameter of the spool is changing and the gear ratio of the reel weather it be 2 to 1 or 4 to one or even higher ratios change how the drag works at giving spool diameters . I should say this is before the dog kicks in to play .
I think lever drags maybe more forgiving ..
I agree with your main point that as the line goes in and out, the spool diameter change causes the drag to change, so we shouldn't worry too much about minor measurement accuracy. I would also add that the line being pulled through the water, especially crosswise, can also add significant friction.
But is also still useful to understand the tradeoffs. For example, a larger OD/ID disk will give you more drag for the same axial load on the system, but will require more rigidity to maintain alignment, and so on...
I would word the star drag statement slightly differently- the gear ratio does act as a divisor: you get only 1/4 of the drag stack torque at the spool on a 4:1 reel. The ratio remains constant as the spool diameter changes.
Lever drags don't have this divisor, and don't have to load up the gears if designed properly (hint: lever drags with roller clutches on the handle shaft are not "proper"), but also have an axial load issue that has to be managed.
On a star drag, the undergear thrust washer can have fairly high friction as long as it lays flat and doesn't wear out fast. Alan often prefers to use an actual drag washer for a thrust washer. So usually not as much axial load worry on a star drag stack. But minimizing axial load required for a given drag setting still has value here.
-J
Quote from: jurelometer on March 10, 2025, 10:28:49 PMQuote from: boon on March 10, 2025, 09:56:12 PMQuote from: jurelometer on March 10, 2025, 02:05:23 PMIf we want to get into exact numbers, then I agree it gets more complicated, but we are not yet in a discussion about exact numbers. We are discussing simpler stuff, and trying to decide if we can accept the basic law of sliding friction because it seems so counter-intuitive.
That's kinda my point. There is probably very little point in trying to apply the very basic "laws" of friction because they are only true for a very "pure" setup, which the drag in a reel is not. Starting with first principles of friction is useful for a theoretical exercise, but not a practical one.
You left out this preceding part:
Quote from: jurelometer on March 10, 2025, 02:05:23 PMThe basic law of sliding friction is useful for a basic understanding, plus it is where you need to start. The engineers that design race car brakes care about all sorts of fancy stuff around friction, presumably with a focus on very large changes in heat. But they still use a frictional surface concentrated on the perimeter of a large disk because the basic law of friction is still in play.
My point is that the basics of friction don't just go away, because the reality is more complicated. They still teach the basics for a reason.
We are looking at variance in kinetic energy transferred to heat from changing inner and outer diameters of dry sliding flat rotational friction surfaces with the same clamping load and coefficient of friction. But not down to any significant precision, just as general working knowledge.
And it seems to me that a single dry drag disk/washer pair on a reel is a fairly simple case if we are only trying to answer these basic questions. But that is maybe because I am only aware of the simpler parts of the physics involved.
If you can enlighten me/us beyond a general statement that this is not a practical approach, I am all ears.
-J
https://www.sciencedirect.com/topics/engineering/amontons-law
Amonton's second law only holds true when there is no adhesion. This is not the case in virtually all real-world applications, therefore the notion that surface area does not affect total friction is incorrect, rendering pointless all further theories that rely upon that being true.
It is not a practical approach because it relies upon a "law" that is simply not true for the application being considered, and leads us to incorrectly discount a completely valid premise, which is that increasing the surface area of the drag increases the total force required to overcome it (to some degree, however small). Other factors which you have highlighted likely contribute to the increase in overall drag force, but in light of the above, the statement below is not entirely applicable, no?
Quote from: jurelometer on March 07, 2025, 06:08:54 AMSliding friction is not a function of surface area. so it doesn't matter if you add more surface area or how many pieces the surface area comes in.
So I've been reading up on here and on the interwebs, and while I'm nowhere as 'sciency' as you guys here, I can mostly understand what you guys are talking about, and would like to give my 2 cents in layman terms.
So it seems that J is spot-on about how surface area does not affect friction, I think why it seems counterintuitive to us is for 2 reasons:
1. More surface area will definitely give more friction if PSI is the same. But since we are applying the same pressure with the star drag, the pressure is distributed across a wider surface area, effectively reducing PSI.
2. My thoughts on race car tires having more grip with slicks and fatter tires does not hold water, because there are other forces at work in a race car tire. The soft tire actually holds onto the small imperfections of the road much like a Velcro effect, which is why surface area matters, because more surface area = more 'adhesion'. In a fishing reel our washer surfaces are mostly smooth, which reduces this effect significantly. If we were to have a metal washer that is grooved surface area will definitely affect drag power, but our drag washers wouldn't last very long.
3. The added drag I am seeing could be due to a variety of reasons, from inconsistent torquing down of the star drag, to the new washer being slightly thicker and newer, and definitely dryer (I have never been able to completely degrease the old one).
In any case, in the name of science and having more drag to stop those angry snakeheads, I will be getting a new drag washer to replace the outer one as well, and run it dry this time. I will report with the results!
I love science. I truly do. Our collective understanding has increased. And that's the victory.
Vogelspinnen, maybe you can mark the star position with white-out or something in-between tests of original washer vs 2nd washer modification—-max. drag. One mark on reel body, one on the star point. Still not an exact science type of thing, but a 2lb. difference in drag friction is significant.
Quote from: Vogelspinnen on March 11, 2025, 06:56:12 AMSo I've been reading up on here and on the interwebs, and while I'm nowhere as 'sciency' as you guys here, I can mostly understand what you guys are talking about, and would like to give my 2 cents in layman terms.
So it seems that J is spot-on about how surface area does not affect friction, I think why it seems counterintuitive to us is for 2 reasons:
1. More surface area will definitely give more friction if PSI is the same. But since we are applying the same pressure with the star drag, the pressure is distributed across a wider surface area, effectively reducing PSI.
2. My thoughts on race car tires having more grip with slicks and fatter tires does not hold water, because there are other forces at work in a race car tire. The soft tire actually holds onto the small imperfections of the road much like a Velcro effect, which is why surface area matters, because more surface area = more 'adhesion'. In a fishing reel our washer surfaces are mostly smooth, which reduces this effect significantly. If we were to have a metal washer that is grooved surface area will definitely affect drag power, but our drag washers wouldn't last very long.
3. The added drag I am seeing could be due to a variety of reasons, from inconsistent torquing down of the star drag, to the new washer being slightly thicker and newer, and definitely dryer (I have never been able to completely degrease the old one).
In any case, in the name of science and having more drag to stop those angry snakeheads, I will be getting a new drag washer to replace the outer one as well, and run it dry this time. I will report with the results!
Are you cutting your own washers , do you have other type of material to work with ?
Quote from: boon on March 11, 2025, 05:50:59 AMhttps://www.sciencedirect.com/topics/engineering/amontons-law
Amonton's second law only holds true when there is no adhesion. This is not the case in virtually all real-world applications, therefore the notion that surface area does not affect total friction is incorrect, rendering pointless all further theories that rely upon that being true.
It is not a practical approach because it relies upon a "law" that is simply not true for the application being considered, and leads us to incorrectly discount a completely valid premise, which is that increasing the surface area of the drag increases the total force required to overcome it (to some degree, however small). Other factors which you have highlighted likely contribute to the increase in overall drag force, but in light of the above, the statement below is not entirely applicable, no?
Quote from: jurelometer on March 07, 2025, 06:08:54 AMSliding friction is not a function of surface area. so it doesn't matter if you add more surface area or how many pieces the surface area comes in.
Thanks for the link.
I would first like to point out a for the record that while I am getting nicked on this thread for oversimplification (rightfully, I might add), I am getting nicked on the thread that spawned this one for potentially scaring folks off for being too technical. On the exact same topic. Can't win :)
I would also like to note that we are probably better off not just focusing on how much (or little) surface area matters. I don't want to leave behind the discussion on the importance of where that surface area resides (how much of it is farther from the disk center).
Ok, now getting back to the question of the surface area effect dry sliding friction:
I do agree that it was incorrect to say that surface are does not matter at all. I should have said that it does not matter much for simpler cases like ours. For the folks playing spectator:
Relatively recent advances in the science of tribology have turned this topic into a complex one, but starting way back in the 1500s or so, sliding friction was considered the result of load and mechanical resistance. The surfaces resisted sliding because they had ridges, pits, grooves, etc. Even if the surface appeared smooth, the imperfections were there, however tiny. It was thought that friction was simply the force required to overcome these mechanical barriers to movement. Some basic experiments can be be performed that support this. You can predict the amount of force required if you know only the force pressing the surfaces together and the coefficient of friction for the surface pair, and surface area does not matter. But as Boon pointed out, these basic laws break down as the situation becomes complex.
One reason behind this is that this resistance to sliding is not just mechanical. there are molecular forces in play, such as inter-molecular attraction between some materials of the different surfaces. There can still be some friction when the surfaces are smooth down to the molecular level. This is what is being referred to as adhesion in friction (at least from this layman's viewpoint).
More surface area, more molecules potentially in contact, and therefore the greater potential for adhesion. But the contribution of adhesion to total friction will vary.
There will be cases when the basic formula will be reasonably accurate, which means that surface area will not have an significant effect of friction, and cases where the formula starts breaking down.
So the debate sort of boils down to this: Is the case of a single carbon fiber washer spinning against a lightly polished stainless steel disk at fairly high loads with low to moderate speeds in an unsealed environment within the bounds of the basic laws of friction, or is this a situation where adhesion plays enough of a role that the basic formula breaks down and surface area also comes into play?
It should be noted that while adhesion is always present to some degree, the coefficient of friction includes the effect of adhesion. So I am not convinced by the argument that the simple existence of adhesion makes the basic laws of friction nearly useless. When adhesion is not a dominant factor in the coefficient of friction, then surface area should not have a significant effect on friction.
I am thinking that when looking at simpler situations in a simple fashion, we don't have to worry too much about adhesion.
There are papers that support this viewpoint, for example:
The importance of adhesion between slider and support in frictional phenomena is reviewed. The conclusion is that it is negligible as long as the term friction is used in its common sense, i.e. as long as frictional force is reproducible for a given path and is a definite function of the normal load. The basic reason for the absence of adhesion in air is that both slider and support are covered with adsorbed films (which represent a weak boundary layer) so that no atomic contact between the two solids is present. https://www.sciencedirect.com/science/article/abs/pii/0043164876902180 (https://www.sciencedirect.com/science/article/abs/pii/0043164876902180)
Also note that even the coefficient of friction is not correctly a single value. It will vary depending on some of the factors mentioned above, and probably some other stuff. Nevertheless, the simple single-value coefficient of friction is listed on material tables everywhere and has value even if it can not always be applied directly in more complex situations.
When designing advanced machine tooling, all the friction details matter. For estimating the drag on a simple baitcaster, I am still at meh.
For now, I am sticking to my guns on surface area not mattering (much), but admit that I should have been less absolute in my original statement.
-J
I know the plural of anecdote is not data but anecdotally it seems to be the case that increasing the surface area of a reel's drag commonly leads to a (highly non-scientific, heh) perceived increase in drag.
More broadly, most of the time in the context of AT.com it's "I did some mods to my reel and I got more drag". There's not enough control (nor really the intent, to be honest) to determine with any particular robustness the exact reason for the increase - it's good enough that it achieves that goal, often spectacularly.
In the general scope of "mods to improve a reel's performance" there are other reasons for larger surface area, too - more surface area is going to conduct heat better out of the drag washer into whatever the "sink" is (the spool on a lever drag or the drive gear, shaft, etc on a star drag) so there are other benefits to doing it.
With my cynical hat on, I wouldn't exclude the possibility that reel manufacturers have discovered they can cut drag washers for multiple reels in concentric rings and thus get more drags from a sheet of CF, or something equally driven by the goal of reducing manufacturing cost while still achieving the required level of performance from the reel. Beancounters over engineers :)
Summation of my thoughts: Does drag surface area increase drag force? Probably. A meaningful amount? Dunno :d
:) All good points to look at . I hope people do take the time to read the papers posted . I need to catch up on the reading myself . Understanding each component of the drags is key .
This thread can break down all the things that can be done to build a drag stack for different applications . We can build stacks for low drag numbers or pull the anchor up and everything in between .
A instrument can make music , but it takes a few to make a concert .
This thread has been great.
Dave, I appreciate the effort you put into your posts. And I appreciate that someone takes on the sometimes tedious duty of reminding us that the laws of physics don't care about our ideology or whether we understand them. We all need a "mr buzzkill" in our lives to keep us in line.
But I'm also glad I followed my instincts when it seemed like an overly reductive interpretation lost some relevant nuance. I am not burdened by the notion that I understand any of this fully. In fact it's quite liberating to accept that I'm not an expert. I don't think I actually made any useful statements. I just asked annoying questions.
Yeah. A good discussion. I appreciate all the contributions too.
I don't want us to overlook that this this discussion has been primarily focused on dry CF drags, but the majority of us grease the drags, which means that we are most likely diving into a partial fluid film situation of some sort that is going to be more complex and variable with heat and rpm changes. I am already over my head in tribology here, so I am not going to touch this one.
I also don't want us to overlook Boon's point that if something appears to work, it could be a worth a try. Messing with reel drag is a low stakes game compared to something like aircraft engine design. But I would just suggest that if something appeared to help one one aspect of drag, it still might hurt others, and we shouldn't be too confident that we know why it worked. This makes it a bit harder to judge the outcome...
-J
To broaden the topic as Joe and Jason has suggested, I think we need to look at drag design as a series of tradeoffs. I see lots of discussion on more or better drag without any definition of what it means. Here is a stab at some starters:
1. Coefficient of friction.
A pair of materials has a unit-less relative smoothness number called the coefficient of friction (CoF). The higher the CoF, the less clamping load you will need from the drag tension knob/star to achieve the same amount of drag. Less clamping load is desirable because it takes less force to tighten the drag, is more tolerant of less than perfect planar surfaces, requires less axial load on the drag system, and probably some other stuff too.
These surface pairs will have different static (from a dead stop) and kinetic (already moving) CoF numbers. The closer the numbers, the more close the startup to ongoing drag will be.
Some material pairs can have a certain amount of elasticity, sort of stretching as it eases into slipping into static friction. I don't know if this technically falls under CoF, but this a related valuble trait in a reel drag.
2. ID and OD of drag disks-
We discussed this one already, but to recap, more of the drag happening father from the center results in more braking work per revolution for the same clamping load. But a larger diameter and lower surface area (especially combined) will magnify drag surface alignment issues (uneven drag) and affect heat conduction and convection.
3. Stacking.
Putting more surface pairs into play allows us to achieve more combined friction for the same clamping load, but it also traps heat, and at least in practice, the load doesn't appear to transfer fully down the stack, especially with eared drags. Too much stacking, especially if you have to make the washers thinner to achieve it, can lead to shearing and unreliable drag performance.
4. Durability/Reliability/Maintenance.
The ideal drag design lasts for a long time with the same behavior, is not sensitive to environmental issues like heat/cold, wetness, corrosion, etc. I think that this is primarily a material choice. Some designs do try to address this by sealing the drag chambers, but this also seals in heat, and whatever water that leaks in as the seals degrade quickly or slowly over time.
5. Other stuff.
There are a bunch of things to consider that can matter to varying degrees like affect on design simplicity, volume, manufacturing and material costs, and so on.
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So lets look at a hypothetical situation starting with material choice:
Let's chose Delrin on stainless steel. Delrin has very close static and kinetic CoFs, and is relatively impervious to water and most chemicals- making it very low maintenance. It will accept reasonably high surface speeds and reasonably high clamping loads. It is also inexpensive.
But the overall CoF for Delrin is low, meaning more clamping load is required for the same drag relative to other materials. And Delrin starts getting squishy at a pretty low temperature. So Delrin would be a good material for an inexpensive low maintenance reel used in situations where longer runs at higher drag is not required. bumping up the drag diameters can help a bit, but that will require better alignment, and more accuracy costs more to manufacture.Stacking may not be too good of an idea with it's low heat tolerance.
Rulon is sort of in the same camp as Delrin, except that it has extremely high hear resistance, albeit at a much higher price point. So Rulon can be a good target for a smooth reliable drag that can handle longer runs, but is still is going to struggle at some point when the clamping load requirements gets too high unless you are willing to accept a large volume drag area. Rulon could be an ideal choice for a higher end fly reel drag, but would be less than ideal for a large lever drag conventional.
And so on.
Delrin, Rulon, Cork, Carbon fiber all have their place IMHO. So does stacking and not stacking drag surface pairs. And so does large and small ID/OD drag washers. The system has to be looked at from multiple perspectives.
No free lunch. No absolutes. Only tradeoffs. I like designing stuff, and am continuously humbled by all the tradeoffs that I missed after I reckoned that I must have thought of nearly everything this time...
-J
Quote from: jurelometer on March 12, 2025, 04:50:44 AMI would first like to point out a for the record that while I am getting nicked on this thread for oversimplification (rightfully, I might add), I am getting nicked on the thread that spawned this one for potentially scaring folks off for being too technical. On the exact same topic. Can't win :)
Ha! You can never please 'em all ;D
There is a time and a place for a "deep dive". This felt like one of them. I always appreciate your considered thoughts, and that you take the time to articulate them.
Wow, I need to reread this entire thread,
Just a few comments from an over eight single dad of 2 very mouthy girls:
1. Grease your drags -
2. Asking light gear to do big tasks - lube parts often to prevent premature failure
Quote from: Gobi King on March 13, 2025, 02:05:30 PM1. Grease your drags -
This is a good example of tradeoffs.
Greasing a carbon fiber drag decreases the overall coefficient of friction (bad), and introduces more heat and velocity related variability in drag (bad).
But it decreases the difference between static and kinetic COF especially once there is any contamination (good). It also reduces the risk of galvanic corrosion, especially if the CF comes in contact with aluminum (very good).
At the factory, the clean dry CF wins out when testing. Meanwhile in the real world, most of us actual users are willing to require a little more clamping force to get more smoothness, durability and reliability in return. And we don't notice the drag load variability since the effective spool diameter change and line on water friction already introduce a ton of variability as well.
This is probably why reel manufacturers were reluctant to grease drags until after it became popular as a maintenance technique in the field.
Quote from: boon on March 13, 2025, 01:59:59 AM[
Ha! You can never please 'em all ;D
There is a time and a place for a "deep dive".
Not all the time? Now you tell me. I have a whole wedding toast that I need to rewrite now. :)
-J
We oughta come with an adjective for Dave's description; "the closer the numbers, the more close the start-up to ongoing drag will be". This, I assume, means the CoF of the 2-surfaces works as drag better under the condition of the 2-CoF's being close to one another. People talk about "start-up", as less is better, but not how to get it and maybe maintain it.(post 31 near the top).
Quote from: Gfish on March 13, 2025, 10:36:52 PMWe oughta come with an adjective for Dave's description; "the closer the numbers, the more close the start-up to ongoing drag will be". This, I assume, means the CoF of the 2-surfaces works as drag better under the condition of the 2-CoF's being close to one another. People talk about "start-up", as less is better, but not how to get it and maybe maintain it.(post 31 near the top).
I am a bit confused by your statement (or is it a question?).But I think that Igot the gist of it. Check out the sentence before the one you quoted:
QuoteThese surface pairs will have different static (from a dead stop) and kinetic (already moving) CoF numbers.
The closer the static and kinetic coefficient numbers are, the closer start-up to ongoing drag will be. This is beneficial.
Lower overall CoF is not generally beneficial for a reel drag for the reasons that were discussed.
Generally speaking, the options to changing the coefficient of friction for the same surface pair are limited to polishing and lubricating. This can lower the both CoFs, but can bring them closer. Often a worthwhile tradeoff for most of us.
Regarding adjectives: I can suggest an adjective for you: "free"
You are welcome for the free overview on drag design.
-J
Yes, yes. Thank you Dave, Jason, boon and everyone else for a great discussion on drag washer resistance. Research and organized writing is work, hopefully it was fun work. I definitely benefited from it. "The best things in life are free!".
The adjective comment was real, not trying to make fun of that part of it. I thought it might be fun to try and come a name for measuring that condition.
Quote from: Gfish on March 24, 2025, 05:31:28 AMThe adjective comment was real, not trying to make fun of that part of it. I thought it might be fun to try and come a name for measuring that condition.
I'd probably go for "consistency" or one of its synonyms like "steadiness". Actually the more I roll "steadiness" around my brain the more it feels like it fits.
First, my apologies to Gfish. I misunderstood his intent on on the "adjective" comment.
Getting back to the question, here is my take: the word you are looking for is a noun, and it is difference. I am using this definition: "A degree or amount by which things differ"
In our case: "the difference between the static and kinetic coefficient of friction". Since the static CoF will be larger than the kinetic, we can experience an instant of higher amount of drag to start the spool turning. This is a one shot deal for every run. Until the spool stops turning, you wont experience that static CoF again.
What we experience as an ongoing sticky drag requires something to be out of whack, like the surfaces not being well aligned and causing the clamping load to change during rotation. There can also be differences in surface finish, corrosion and/or contamination that can temporarily increase the CoF when pairs of "bad" spots happen to to be in contact.
If the drag is sticky enough, I guess you could get into micro stops and restarts, and bring the static CoF back into play.
A drag material that has relatively high and not very different static and kinetic COFs is valuable, but the most important thing is probably a stack that maintains alignment of the surfaces under drag load.
-J