Calculating main gear shaft torque from drag settings

[jurelometer]

[Note:  Updated this post to include the calculator tool - just download and click on the formula you want to use-  requires spreadshheet program compatible with microsoft .xls format]


Thought I would share some findings on the amount of force generated on the main gear shaft for a conventional reel.   This is useful  for determining the amount of force on the anti-reverse mechanism (dogs or AR bearings), as well as the main gear and handle shaft.

Opinions/corrections are welcome.


1.  Here is the formula:
    R:   radius (not diameter) of spool including line
    F:   Force (drag setting at reel)
    G:  gear ratio

Torque  = R*F*G

Simple enough.

2.  Example:  Let's apply this to a popular size small to medium saltwalter reel sized reel.  Let's say we have a reel spool  filled with line to a 1.25 inch  radius (2.5 inch diameter)  a 8  lb drag setting, and a 5:1 gear ratio.

Torque (lb-in) = 1.25*8*5 = 50

It is probably more useful to translate the torque number to more common units:

lb-ft (AKA ft-lb) = lb-in/12 = 50/12 = 4.1667
N.m. = lb-ft* 1.35582  = 4.1667* 1.35582 = 5.6493


3.  Lets look up some one-way bearings for fishing reels on the Boca site:    For shaft sizes 10-12 mm- we are looking at a range of 2- 6 Nm, depending on the bearing.    If we want a bearing capable of handling more- we need to have a shaft size of 14mm- where they move up into  15+ Nm ratings

4.  Observations:

a.  These are theoretical numbers- any friction in the system will decrease the torque some, but it should be close enough for or our purposes.

b.  Anyone familiar with using a torque wrench will recognize that the amount of force being applied on the anti-reverse mechanism of a typical reel is relatively small.    These components fail because of design choices, not unmanageable load for the reel's basic dimensions.

Agree/disagree?  

-J

[Dominick]

Since I didn't understand a word I agree.  I can't add 2 and 2 without making a mistake.  I know you are being serious but my trying to make sense makes my eyes glaze over.  Dominick

[Alto Mare]

The line doesn't stay at the same place on the spool when fishing. Just to name a few:  boat speed, wind conditions, type of line used, type of rod and position of that rod all come into play. There are other factors to take in consideration, you could get close but that's about it.
Most manufacturer will mark line retrieve on their new reel boxes, lets say line retrieve is 34" per crank, but they don't tell you where the line sits on the spool when getting that number. Those figures are worthless to me, as soon as you drop a couple hundred feet of line in the water, those figures go with it...just my opinion.

[jurelometer]

The line doesn't stay at the same place on the spool when fishing. Just to name a few:  boat speed, wind conditions, type of line used, type of rod and position of that rod all come into play. There are other factors to take in consideration, you could get close but that's about it.
Most manufacturer will mark line retrieve on their new reel boxes, lets say line retrieve is 34" per crank, but they don't tell you where the line sits on the spool when getting that number. Those figures are worthless to me, as soon as you drop a couple hundred feet of line in the water, those figures go with it...just my opinion.

I agree that real field observations beat calculations, but sometimes the calculations will help you find out things that take too much trial and error otherwise.

As the spool decreases the drag setting goes up accordingly, so I think these even out.   boat/wind/current speed, rod angle etc.  affect the pressure that the fish may feel, but not the maximum torque on the dogs/ one-way bearing/gear sleeve to handle junction, etc.   This is controlled by the drag setting.

I will give you a few examples of usefulness. 

1.  If someone wanted to add an aftermarket  one-way bearing to a reel- this would help them determine the specifications for the bearing.

2.  For the Baja Special dog enhancement you are working on-   you could have Lee cut you out a bridge sleeve to hex-head adapter.   I think you could bolt the bridge assembly to a work bench.  use a torque wrench and observe the amount  much reverse pressure it takes before the dogs start tweaking when the sleeve is aligned, tilted out of alignment etc.  You can convert the torque number to an approximate  drag setting with the posted formula.   You can compare any improvements you make against this the same way.    It will not 100% prove that it will be fixed in the field, but it might make the process of getting to the right solution faster. 

(BTW- I think the Baja Special dog/ratchet project is a great idea.  It can most likely be a component level fix, and should apply to the US Senator line as well.)

3. It helps provide me some sense of the amount of force on the reel components.  The changes in manufacturing and materials capabilities allow for some new designs that could meet these forces without overbuilding the reel as is done today.   This also applies to reel modifications, but to  a lesser extent.   For example, it shows that the dog/ratchet assembly on the Baja Special should be able able to withstand much greater pressure than it does today,  as long as the components can be kept in alignment.


This of course presumes that my math is correct- always a risky proposition

[mhc]

This of course presumes that my math is correct- always a risky proposition

I applied your formula and logic to the max drag results George got using the same 5+1 drag stacks on two 349s with different gear ratios, 349 (2:1) 29 lbs & 349H (3.25:1) 18 lbs. http://alantani.com/index.php?topic=4983.0

Assuming both had 1.25" of line (around 1/2" from the lip of the spool) the amount of torque the drags could hold before slipping on each reel is;
349)  1.25*29*2.1 = 76 lb/in or 6.3 lb/ft or 8.6 Nm
349H) 1.25*18*3.25 = 73 lb/in or 6.1 lb/ft or 8.2 Nm  

Pretty close given the variables.

Like you said - a torque wrench would be a quick bench test of modifications, using the formula to calculate a ball park figure of what torque will be generated.

[RowdyW]

Well if you are lost a Radio might help if it is a 2 way. 

[jurelometer]

I feel my chain getting yanked     But  this stuff isn't that tricky.

Torque is  just rotational force applied at a distance from the center.    So if we are applying 8 lbs of drag  with the line one inch from the center of the spool, we are applying 8lb-in of torque.  Gears provide a mechanical multiplier so we have to multiply by the gear ratio.  Now divide by the number of inches in a foot (err... 12).   Now we have ft-lbs of torque (units on your torque wrench) based on reel type and drag setting.  Piece of cake.

If you have ever tightened a bolt with a torque wrench, you will know that a couple of  ft-lbs of torque is not very much force.   That should be useful info for all the folks customizing dog and one-way bearing setups.   Also, since upping the gear ratio increases the torque, the same star drag reel  will have less total drag capacity with a higher gear ratio, etc., etc.    

[Robert Janssen]

...the amount of force being applied on the anti-reverse mechanism of a typical reel is relatively small.    These components fail because of design choices, not unmanageable load for the reel's basic dimensions.
Agree/disagree?  

I didn't bother to check the math or anything, but it sounded about right.

Agree. I don't know offhand what force is required to, for example, break a Senator dog, but it is a lot. Many, many times over what the drag / line is capable of. In the case of one-way bearings, yes-- this is absolutely an important design consideration. This, along with wear. I met a design engineer at another company, and we started talking about unforeseen wear and real-world circumstances of the life of a trolling reel. He was wondering what would happen if a boat was trolling a lure that skipped across waves, all day long, every day, every month, for years. pull, skip, pull, skip, yank, stop, yank, stop... so he put an antireverse mechanism in his CNC machine and programmed it to do a yank/stop cycle one million times. it took a couple of weeks. (The mechanism held. He didn't say what it looked like)


Not entirely unrelated earlier thread: http://alantani.com/index.php?topic=4589.msg35751#msg35751

.

[mhc]

Jurelometer
I hope you don't think I was yanking your chain? I agree with you, it's not that tricky, the formula explains very well, and simply, why the same drag configuration gives different max drag with different gear ratios and diameter of line on the spool. It lines up very well with George's observations when he tested his 349s for max drag.

I have recently added a couple of modified dogs and dog posts to a couple of 349 bridges using very basic tools and techniques, hence my interest and reference to 349s and max drag. I am not all that confident with my posts in particular. With your calculation, I can now screw the bridge down and test each post and dog to the max torque that I can expect/want on the gear sleeve for the target max drag, before assembling the reel and doing any practical tests of the complete system.
For example; if I think I can find a drag set up that will provide 30 lbs on a 349H with a full spool, the calculation is;

1.5*30*3.25 = 146 lb/in or 12.2 lb/ft or 16.5 Nm.

Then, using a factor of safety of 2, the dogs and posts will need to withstand ~ 30 Nm. If they do pass the test and the reel fails practical tests later, it will not be the dogs or posts that caused it.    

I'm going to find a torque wrench and try it.

[Alto Mare]

Dave, you're a very smart man, I got that from the very first time I talked to you. Thank you for doing these figures for us. Calculations will get you close, but you will still need to use it on the field.
When doing upgrades, we take a short cut here, we already know that most of the vintage reels we upgrade have been made stronger than expected and some have been in service for well over 70 years, Penn already did the hard work for us.
This was a big achievement on their part and I personally believe that it won't happen with the newer models of today.
This is one of the reason we like to invest in those.
Sal

[johndtuttle]

This post is more important that most realize...not for the mechanical dogs so much as I think they are far stronger than they need to be. The case of the Baja Special is a different one as the ratchet and dogs are "tippy" and can be slightly out of axis when they engage as well as the teeth being particularly fine and sharp meaning they have less handle back play but can "bite" the dog.

With AR Beaings however, we see them fail often as they are on the handle side and the gear train (closer to 6:1 in most recent reels) multiplies that force considerably. Combine that with 15lbs of drag and you end up with 90lbs on the bearing. Most are not "rated" for this load and really only function reliably due to their having a "safety margin" over their rating (typically 100% or more).

This is why so many fail in conjunction with corrosion due to their exposed position in the handle in conventional reels. A little corrosion, a hesitation to bite plus a force greater than the bearing is designed to manage and the handle goes knuckle buster.

This is why they all have back up dogs now.

As well, the AR Bearing being placed in the handle so that the gear train experiences the forces first causes unnecessary wear, whereas for example in a spinning reel they spare the gear train all force (unless you try and crank against the pressure) as they stop rotation before the gear train experiences it.

Final upshot: In a conventional reel the handle side is the convenient place for an ARB but they are highly stressed there due to the effects of gearing and exposed to corrosion. Understanding the forces is key to understanding why back up dogs are there.

[jurelometer]

MHC:  sorry- didn't want to include you with the chain-yankers.  I am curious as to how you plan to attach the torque wrench to the bridge sleeve.   Btw - I think you skipped a step in your unit conversions for the 349- the Nm number should be much lower.

Also an interesting question- what kind of torque measurement tool is reasonably accurate at these low settings.  Not sure I would trust the one that sets my lug nuts.

Reel224:  all in fun.  Does my head look that pointy?   Honest- it's just the hair . If you just want to know the drag setting, use a drag scale on the line.  This is more about the forces on the other end of the system.

Robert:  thanks- some interesting data.   I think that the Q in the post you referenced was really about force and not torque.  The easy answer  would have been use a scale on the handle and then adjust for new handle length.

Sal:  agree with everything except the "smart" part .   The testing and innovations you have contributed to us all  are the basis for some of my ideas.  The classic Penns have a consistent design that was effective for the customer usage and manufacturing methods of the 1930s.  80 years later these are still viable reels with some part upgrades.  I think the key to getting a better dog system is to keeping the parts flat and aligned-  this is what the numbers tell us, and this is where the baja special design is "challenged".  

John:  agree.   I am curious as to the effect of slipping on one-way bearings in terms of longevity.  Also, if stacking one way bearings really distributes the load evenly.  Since the inner race has to jiggle and rotate for the bearing to lock, it would seem that only the first one to grab would lock completely...

[jurelometer]

MHC:   Just thought of something.  You could use a crescent wrench and a spring pull scale for measuring the torque at the gear sleeve. Just stick the scale hook in the hole in the cresent wrench.  Divide the force by the distance of the lever.   

[MFB]

Anybody looking for a serious upgrade, should consider one of these. Max torque 8450 Nm 

Regards

Mark

[mhc]

Btw - I think you skipped a step in your unit conversions for the 349- the Nm number should be much lower.

Correct, I skipped lb/inch to lb/ft and have now fixed it thanks - no really, it is a simple calculation 

I haven't got round to thinking about the torque wrench connection, but I like your idea of a wrench and pull scale for the low torque.