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Calibrating Lifeline Chest Expander Cables - An Experiment

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Jan 24 10 11:39 PM

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So, as I said, I took my Lifeline chest expander into the gym today to test the resistance of the cables. I did this by hanging the expander off the pullup bar (tied with a belt), then attaching weight plates to the handle and see how far it would stretch.

The cable tested was a yellow - rated at 70 lbs. at double stretch (that is, per side).

So to begin with I took some measurements. To ensure consistency, all lengths were measured between the tips of the middle plug of the expander handles, i.e. the shortest distance between the cables:

At rest (without being previously stretched): 30 cm (11.8"). With about 2 inches from this point to the cable ends on each side, this comes out to more or less the advertised 16".

Finishing position of back press (with scapular spread at the end of the movement): 125 cm (49.2")
Finishing pos. of front press: 122 cm (48.0")
FP of front lateral raise: 119 cm (46.9")
FP of overhead downward pull: 123 cm (48.4")
FP of front chest pull: 122 cm (48.0")
FP of bicep curl: 106 cm (41.7")

So into the gym I went, and decided to start off the experiment with a mere 20 kgs (44 lbs.). Seeing as the Lifeline yellow cable should provide 70 lbs. / 31.8 kgs at a stretch of 60 cm / 23.6", this should not have stretched the cable much at all. I was (unpleasantly) surprised to discover that the weight stretched the cable all the way down until the plate touched the floor, and would have continued stretching it further had the pullup bar been positioned higher. The cable was stretched thin and looked about ready to snap. Stretch at this point = over 130 cm between the reference points.

This pissed me off quite a bit.

I removed the weight and started experimenting with lower resistances.

5 kgs / 11 lbs. slight stretch – did not bother measuring it

10 kgs / 22 lbs. stretched to a whopping 84 cm / 33” (more than double stretch)

15 kgs / 33 lbs. stretched to a huge 127 cm / 50” (further than I stretch the cable in any of the exercises)

Since this was as far as the cable could go with the weight still hanging above ground (without touching it), I decided to call it a day. The findings of this little experiment are very disappointing – the quoted resistance obviously has no grounding in reality, i.e. the yellow cable most certainly does not provide 70 lbs. at double its original length. In fact, a mere 22 lbs. were sufficient to pull it further than double length. This is less than one-third of the claimed resistance.

Perhaps there is a trick of physics that I’m overlooking, but as far as I’m concerned I will not bother with cable poundages anymore – two yellows are “heavier” than one yellow and one red, and that’s it. I will measure progress by colors.

I must say that I wasn’t expecting the cable to perform as advertised – any measurement of resistance had to be unreliable. But this is still a huge surprise. The resistance rating seems to be completely random.

Other interesting observations:

The cable seems to stretch in a linear proportion to the weight attached: 15 kgs divided by 10 kgs – weight increase by a factor of 1.500, 127 cm to 84 cm – length increase by a factor of 1.511 (more or less equal).

Measured the cable at rest after stretching – 34 cm / 13.4”, or an increase of 4 cm / 1.6”

Measured the cable at rest after I’d gotten home – 30 cm, like before. Good elasticity.

Last Edited By: BigBruvOfEngIandUK Jun 5 11 3:48 PM. Edited 1 time

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#1 [url]

Jan 25 10 4:56 AM

Thank you Fatman for the time and trouble you took for researching

This is a real let-down.   I'm sure nobody expects precise accuracy with advertised cable poundages,  especially with things that stretch,  but one would ( and should ) have expected reasonable proximity to stated manufacturer's figure, perhaps a margin of 10% each way.

I can't believe Lifeline would be so up the creek with their cable measurements.  How discouraging to find that your two yellows and one red don't seem to to be anywhere near the 200lbs one would have expected,  after your experiments.  I know I've mentioned before that one can get too caught up in figures,  but it's nice to have one or two poundages in the back of one's mind to use as goals and sources of satisfaction.  Let's face it,  that's what one uses in weight training to gauge their progress.

A trainer who is not aware of the results of your research could be training for years and not getting much stronger at all,  moving up to "stronger" cables only because the previous ones are weakening.

Unless something is going badly wrong back at the Lifeline factory,  the only thing I can think of is that your cables have weakened through the years of constant use,( because of the rest length of your cable after stretching taking the time of a trip home to return to normal.)  How many years is the question.  If this is true and you've only been using the cables for a year or so,  that's not very good as far as I'm concerned.  I don't think anyone should expect say five years of use without significant weakening,  but if the Lifeline cables are lasting only ( or less ) than a year,  then I think there's something seriously wrong with their quality. 

I'm trying to source a spring scale so that I can do the same sort of experiments that you did with weights.  The sooner the better because my orange cables are still relatively new.  In saying that,  I've noticed some "kinks and bumps" starting to appear in my cables with only a couple of week's use.

I don't know if other Lifeline users have experienced the same things happening,  but I'm wondering if you shouldn't be getting back to Lifeline with the results of your research,  and asking for their comments.

I know I certainly will be if I obtain similar results as you did,  with the spring scale.

I would rather pay twice ( or more ) the amount for a decent set of cables that I knew were consistent, than buy cheap junk that gives me no reliable indication at all of my progress, or lack of.  

I think I saw somewhere on the Net that your "snake oil salesman" Matt Furey no longer promotes Lifeline and I wonder if this has something to do with it.  I might be making connections where there are none,  however.



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#2 [url]

Jan 25 10 3:48 PM

Well, perhaps the cables are not providing the quoted resistance, but all is not as bad as it seems.

Going from one colour to the next still provides a good gauge of progress. So even if going from two oranges to three oranges is not really "100 to 150 lbs.", you are still getting 50% stronger. And if you can move up to stronger (presumably new) cables, it wouldn't matter much if the old ones were weakening.

I don't think my cables have weakened from use, I only got them last July or something (so around 6-7 months). And the cable does return to its original length at rest, so I don't think the resistance is lower than when I bought them. It's just not the resistance they quote. Which is still shitty, but not tragic.

The cables are not weakening in other words - they just weren't as strong as they were advertised to be in the first place.

That said, I've been thinking about e-mailing Lifeline to get this thing sorted out. I don't know if that will have any effect, but from our interaction thus far they seem like a very decent and user-friendly company.

And Furey is now too busy promoting the benefits of backwards walking and Chinese erection secrets to care about expanders anymore... or exercise in general, from the looks of it

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#3 [url]

Jan 25 10 5:22 PM

Yes you are quite right Fatman,  all is not lost.  One can still get a pretty decent workout one way or the other, and at the end of the day, " are you stronger and do you feel good ?" are the main questions.

Trouble is, I am happy to let most things ride, in life,  but once I latch onto something I find interesting,  I become a compulsive delver.
As the researcher for my deceased wife's family's Maori Land,  I've found a few land blocks that were previously unknown to the family,  and this business of Lifeline's cables has me intrigued no end.  Why the hell should I worry I don't know,  but tomorrow I'll be picking up a 40kg digital scale to measure my new orange cables.  If it turns out they are well short,  that won't stop me using them, at least until I buy The Hook,  but at least I'll know what the story is.  I certainly will be contacting Lifeline to ask what their comments are,  not to be contrite or anything,  just to find out, that's all.

It'll set me up for measuring my springs as well,  and eventually when I start training with The Hook I'll write down my workouts and periodically test the Hook cables,  just as a contribution to the knowledge base.  I'm sure most of it is already well known,  but it's an interesting project for 2010.

Wonder what Furey's up to at the moment  :-)    ?? 

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#4 [url]

Jan 25 10 5:53 PM

I am very interested in your spring-scale test. This is how they test cable pulls for competition purposes (from what I've heard).

The yellows might not provide 70 lbs. of resistance apiece, but they sure give me a hell of a workout.

And testing the Hook (not that one dares doubt the infallible El Capitan) will also be of great interest. I see that his surgical tubing cables are rated by resistance (5 lb., 10 lb., 25 lb.). Perhaps he will share with us the method he uses to determine cable resistance?

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#5 [url]

Jan 25 10 7:08 PM

I jacked up a digital 40kg scale today and will pick it up tomorrow in 11 hours time  ( just after midnight here in NZ 26th )
Not cheap,  especially for someone like me on a benefit,  but once I've got it, I've got it. 

I'm going to test everything I've got here and I'll get back to you on the oranges and the steel springs ASAP.

Later after I receive The Hook I'll do some testing to start with.  I'll determine where the designated poundage lies and then see what they are when stretched to my arm span.  Then I was thinking of spending a year ( divided into 13 four-weekly periods with three workouts a week ) just working with The Hook, mainly as a chest expander, and at the end of every period I would test The Hook cables and post the results to El Capitan.  I'm not sure if he's interested as I wasn't going to mention it until I ordered the equipment.   But I'll still do it for my own interest,  and of course you can let me know if you want me to post you my ( simple ) workout and test results. 

Yes I bet you still get a helluva workout with your yellows and red.  I find that two oranges are pretty much the same overall as four of my Chinese springs ( 10 good reps FCP each ).   Apart from the springs a bit heavier at the start,  and the cables a bit heavier at full stretch,  which I'll be able to put a quantity on when I measure them. I've gotten a bit more used to the soft handles now so I'm currently FCP with the conventional knuckles out position. I would rather have the triple grip, though.  I still OHPD with knuckles out as well for 11 good reps to the front.  I always leave one rep "up my sleeve" in a set. 

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#8 [url]

Jan 26 10 3:46 PM

Here's what I've found,  Fatman.

I marked my three orange Lifeline cables and tested them each three times from resting + 8",   32" and my full span @ 64" (palm) handle to (palm) handle ( I took that measurement using the hard handles of one of my steel spring expanders ) It's hard to self-measure one's span accurately,   but with all the measurements I took, the mode measurement was 64".  The scale I bought is actually a luggage gauge with a handle that has a digital readout in it,  and a clip strap to feed through a suitcase handle.  I marked various measurements up the edge of my bedroom door and stood on one end of whichever expander I was measuring the cables of,  then used the scale on the other handle,  hauled up to the relevant measurement,  held steady for the "beep", then read the results.  The measurements of course were a bit wobbly,  but I was fairly careful and got reasonably consistent  averages.
O1 @ 32" =  15.5lbs  average
O2 @ 32" =  15.8lbs       "
O3 @ 32" =  15.6lbs       "

O1 at full stretch =  28lbs average
O2 at full stretch =  27lbs     "         
O3 at full stretch =  26.6lbs  "        

Resting + 8" pull out = 10lbs each orange average.

So far these measurements support your findings that the pull weights go up in a Linear fashion, not Exponential, as the cable is stretched.

Fatman and Sam
I e-mailed Lifeline with my results and I await their comments.  Actually,  while I was typing the e-mail,  a large penny dropped and I am thinking that their reply will be to the effect that the pull weight designations are for three cables all up,  not each cable separately.  Therefore my Orange cable expander,  cables tested to twice their length,  comes to 50lbs total fully cabled (3). 
At least two of my 32" measurements came to 16.4lbs,  and three times that is 49.2lbs, not far from 50.
If this assumption is correct,  then the following measurements probably wouldn't be far from the mark :-

The measurements come to an 80lbs pull weight on full stretch of all my orange cables. Therefore,  I'm currently pulling 53.3lbs ( two cables 80/3 X 2 ) at full stretch FCP for 10 reps. This arithmetic is supported by an actual test of two cables at full ( mine ) stretch of 53lbs even.
By the same proportion, your two yellows and red would come to 70yellow X 8/5 = 112.   112/3 X 2 = 75 rounded off.   60red X 8/5 =  96.   96/3 = 32.    75 + 32 =  107lbs @ 64" stretch handle to handle.   Looking at your FP measurements 48" seems pretty short. I'm sure you're not 48" palm to palm are you  ?  Even though you said that you have shortish arms, I would put you at at least 56" palm to palm (where you hold the handles )   That would give you a respectable 94lbs that you are hauling FCP for 10 reps rest/pause style.  Most impressive in my book.

It would seem that my 200lb target for FCP is just a teeny bit ambitious.

I measured my springs from the Chinese set.  Both brand new and used ( four months ) were almost the same poundages,  within one pound @ 32" stretch.  The 32" of course is irrelevant to the steel springs.  I used that as a comparison mark only.   They averaged out at 7.9lbs each,  which backs up my assertion that two chinese steel springs + one orange cable,  at least at 32".    The 4lbs @ 8" from rest just goes to show how wrong I was thinking the steel springs were harder to start initially ( 2 springs + 8lbs whereas one orange = 10lb )
Where I was also up the creek was in my estimation of four springs equaling two oranges at full stretch.  The springs came to 20.4lbs new, and 19.6 used, averaging 20lbs.  As they are slightly parted at the ends, due to my span being right on the string tight, this seems to be in keeping with fairly typical 20lb springs.  But with me using four for the same FCP number of reps,  I am mystified as to why I think that 80lbs steel spring pull weight feels the same as 53lbs rubber cable.  In scientific terms, buggared if I know!  Could be that the soft handles of the Lifeline set make it feel that way.
It'll be interesting to see what happens when I buy a pair of triple-grip handles. With the chinese springs,  all five would make a very respectable pull @ 100lbs full stretch.

What was a real surprise was the York springs.  I bought a NakedGym ( a new sporting firm in New Zealand ) and a York set from Rebel Sports and when I unpacked them, I found them identical.  I suppose NakedGym is re-packaging York and marketing under its own name, ( which is supposed to reflect the ancient Greek custom of athletes training in the nude.  One would hope so. )

The York springs separated right from the first pull,  although they remained consistent from then on.  Nevertheless their measurements at 8" and 32" were all over the place,  which of course I guess doesn't really matter. 
What was surprising was that at my full stretch,  the York/NakedGym springs were an average of  31lbs each. Even with the used springs being an inch or so longer the new ones, the pull weight at full stretch remained consistent with them all.  I must admit I don't use them much because I prefer the Chinese springs,  but I measured them again and again, and always the same poundage ( within a pound and a half ).
If anyone put all five York springs on their expander and pulled the lot out on a FCP or a OHPD,  they would be hauling a whopping 150lbs +.
All right, it might not be anywhere near the World record,  but hell,  I'm sure the gorilla's compound at the zoo would not seem unfamiliar.

Finally I measured the old plastic handle expander set that uses bungie cord.  I've cut the cords down so that the handles are closer together.  I use this set-up exclusively for proper Archer's Pulls,  the way I think they should be done.  Starting hands close together,  same as a bow,  then pull to opposite pectoral, which is directly under the ear when the head is turned in the direction of the "arrow".
For a distance of 33" and four cables, it's an 80lb pull, which I suppose is not bad for ten reps and a hold. I have to say I often have to drop down to three cables because I find that the Archer's Pull is quite unusual ( a least for me ).  I can go well on four cables for a week, then suddenly I'm just not there with four at all,  and have to drop down to three cables.  Once I had to even drop to two.  None of the other "Big Six" exercises treat me like that and again it's a mystery to me.  The only thing I can think of is that the Archer's Pull, done in this manner, is an extremely powerful exercise,  even in the relatively muscle-relaxed Chi Kung world, and I'm wondering if there are energy meridians than are more powerfully affected by this movement, than the other exercises. 








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#10 [url]

Jan 26 10 4:09 PM

Macky,

Thanks for the input, very interesting findings.

About the range of the FCP, I was measuring between the tips of the middle plugs (shortest distance), not handle-to-handle. My brother actually took the measurements with a tape measure (and did not miss the opportunity to make fun of my bizarre hobby, I can assure you), so they're pretty reliable. The handle-to-handle measurement would probably be at least 10" longer overall, maybe 58" or more - I have shortish arms, but not circus-short

I am inclined to agree with you - three cables provide the quoted poundage, although this is NOT what they state on the website.

Funny thing about the steel springs. So the actual resistance you measured is more than 50% over the rubber cables (80 compared to 53 lbs.), but in reality it feels the same. You even said that the two oranges feel "heavier" at full stretch. I'm pretty sure it has to do with how the resistance curve hits you at the sticking points, which make or break a lift/pull. From what you just wrote it seems that any "resistance" rating is pretty ambiguous - I would rather use an alleged 50 lbs. if it limits me to 3 reps than do 10 easy ones with 100 lbs. Kind of mind boggling, eh?

Let us know Lifeline's answer. What I am pretty sure they did is as follows:

They made a series of rubber cables of different toughness/pull resistance.

The series consists of 9 different "resistances".

The lightes one is light enough to be used by children, the heaviest one is heavy enough to challenge a strong athlete. The other ones fall in between: "light-strong", "moderately heavy", etc. Slap on some numbers to go with the cables, and there you go.

Thanks again for the research.

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#11 [url]

Jan 26 10 4:45 PM

That's interesting work on the calibration findings. I thought the same that it might be all three cables together that give the resistance rating. Will be interesting to see if you get a reply from Lifeline.


Macky, 200lbs FCPis a lot but I should think in the short term 150lbs is attainable. I'm doing the 7 springs now which is 140lbs and I'm certainly not a big build by any stretch and it only took a few months to reach that amount. I'm aiming for 8 springs which would be 160lbs and then I'll just keep going. I use the slow cooking method where when I add an extra spring once I can pull all my current springs easily. Slow cooking is where you put a long length of cord from the handle to one end of the spring. This means with the handles at full stretch the new spring only gets stretched a small amount. Over time I shorten the cord until eventually I'm stretching the whole spring. It's a method the old timers used to make continuous progression. I've also got a couple of purposely over stretched springs that do a similar thing as the cord. It just allows you to get past the sticking point and work in the strongest range and then gradually shorten the cord to work in the weakest range of the movement.

Paul.

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#12 [url]

Jan 26 10 5:30 PM

Yes I did some more measurements and the pull weights are nearly linear,  not quite, especially on the first 8" to 16" measurement.
What the hell.    I guess that the most important measurement is the full stretch one,  as I can't think of any major strand pulling exercise that doesn't use full range of motion.

58" full span sounds a lot more like it.  With that span,  you're knocking 97lbs full stretch.  Which is real good, as far as I'm concerned.  I've now revised my target to 100lbs,  but hey,  having a good workout, feeling good, and getting stronger is really what it's all about. I've got congestive heart failure so I have to pace myself,  but it's all still very enjoyable.

I really think that the soft handles yanking on the base of my thumbs has got a lot to do with how the rubber at 53lbs feels like the steel at 80. All though I've got a bit more used to it,  it's still mighty uncomfortable, and I can't understand for the life of me why Lifeline came up with such a cocked-up idea. They must have tested their soft handles. Did they test them with one teal cable and then say it's OK ?  I'm sure things will change when I obtain some triple-grip.  The last thing any trainer needs is to be pre-occupied with uncomfortable mitts while performing otherwise powerful exercises.
Maybe you are right re differing resistance curves.  It might throw the momentum around a bit and make the "lock-out" seem harder than it really is.
I pull out fairly quickly and after a significant pause,  fight the cables on the way back in. 

Now that I've done the Lifeline cables,  and had a look at the steel springs,  the only numbers I'm interested in now are the full stretch ones. If I get any more Lifeline cables, I'll only measure them at my full stretch,  unless someone asks me to do some more work for them.  Once The Hook comes along,  I'll crank up a few parameters, and then stick to them for a year.





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#13 [url]

Jan 26 10 5:43 PM

Hi Paul

Yes I remember your seven springs with 140lbs haul on them. That's huge. Interesting training method you've described.

Keep me posted on how you're doing,  if you would.  There's a lot of very strong trainers around, but some individuals just seem to progress much faster than the others. 

Best

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#14 [url]

Jan 26 10 7:00 PM

Macky,

From the experiment I did, it seems like a yellow cable produces 15 kgs (33 lbs) of force when stretched to a length that's around my full stretch. So 3 yellows = 45 kgs, or 100 lbs more or less. 2 yellows + 1 red = a bit lower. Your calculations appear to be right.

Most people who have experience with both soft and hard handles agree that heavy pulls are almost impossible with the former, so get the plastic ones when you can. I'm sure they will enable you to pull a bit more resistance immediately.

Paul,

You use Spenby springs, correct?

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#15 [url]

Jan 26 10 9:19 PM

Yes, I've got 3 sets of Spenby expanders and two other modern type which a lot of companies sell with their own name on. The modern springs take 27lbs to reach the same length as the Spendby ones and are quite tight as soon as they start to stretch. All my Spenby springs take between 18 and 20lbs to reach full stretch.

Macky - the slow cooking method is an old school method I read about somewhere on a strand pulling website, not sure where it was now though.

Paul.

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#16 [url]

Jan 27 10 12:05 PM

Hi Fatman
I know you're not particularly concerned at all,  but I'm sure you're hauling 100lbs with your YRY combination ( I've just read your new training log format ) Your span handle to handle could well be 60".  That might seem too much, but it's not fingertip to fingertip,  and two inches less than mine both sides is quite a lot shorter.  Therefore 107lbs @ 64" for YRY = 100.3lbs for 60".
The interim measurements that I did were interesting,  and gained some insight into Lifeline's cables,  but really I believe the most important figure is the full-stretch one.  Let's face it,  that's when you are at your maximum tension,  and still have to return the cables to "zero" in an orderly and controlled fashion without turning yourself inside-out.

No word from Lifeline as yet.

Hi Paul
Does Spenby make and sell expander sets these days ? All the sites I see on Google seem to only be dealing with vintage Spenbys.  Are/were they a British make ?  They look a lot like the Terry's I had in the 60's and 70's.

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#17 [url]

Jan 28 10 1:49 AM

The Spenbys were a British make and the Terry's were too. The main difference were the springs, the Terry's springs taper at the ends while the Spenby's don't. Spenby don't make them any more as far as I know.


Paul.

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#19 [url]

Jan 28 10 4:10 AM

Thanks Paul and ayeedee

I didn't think new Terry's and Spenby were around any more,  but down here in NZ we often have "new" equipment arriving that has been in Britain or US for some time,  and unless one has been delving around on the net,  one doesn't know about it for a while.

The Chinese set that I bought looks very much made after the Terry's style with wooden handles that will rotate and springs that taper at the ends.  These springs I have used for four months and they have largely retained their strength at just under 20lbs my full stretch,  as I posted in my results.

The set cost NZ$15 which is about $10.60US I think so it was cheap. I went back to the store for a look around and they had hammock attachments with five springs that were identical to my expander.   I bought 3 attachments for NZ$40 all up which has loaded me up with good springs for a long time.  In saying that,  for some strange reason I've ended up using the Chinese springs with my York plastic handles,  which I've taped for gripping more firmly.   It is this combo that I measured for my tests.

Yesterday I did a PR of five strict reps with 5 springs ( 100lbs ) OHPD to the front with knuckles out,  so I'm quite pleased with that.
And a PR of 12 reps with 4 springs FCP ( the rep count was the PR ) 80lbs.

I have to say though that despite me proving myself wrong with a couple of my measurements,  as to the relative difficulty between the springs and the rubber,  the rubber strands still have a much different feel to them than the springs, at least to me.  I am using both in my limited workouts,  at least until I obtain The Hook.






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#20 [url]

Jan 28 10 3:51 PM

That is what really puzzles me too.

So the steel springs were measured to offer more resistance... but actually offered less (or just as much as the rubber cables, which registered a much lower pull on the scale).

Gotta be the sticking points.

What I would really like is to get my hands on some steel spring expanders and see what happens.

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