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Input Needed -- Regarding Counter-weight System For Equinox Shafts...


steveg

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Hi all.

Now that I have the prototype shafts built, I've been able to work some more on the counterweight design, and I have moved very close to finalizing the design. 

I have discovered through this extensive testing/design that the amount of weight needed to achieve proper counterbalance is a bit more than I was originally thinking, after the preliminary, "rough" proof-of-concept testing.  I would like to present the findings, and get some opinions -- from anyone who has been potentially interested in the counterbalance system -- as to whether these changes are acceptable, or if this would change your desire to possibly purchase the counterweights.

1.  The weight needed to counterbalance the 12" x 15" coil, (based on an "average" lower rod extension length), is roughly 28 oz.  This is a fairly substantial amount of weight -- BUT -- I must note that when the weight is applied, the machine swings BEAUTIFULLY.  It FEELS lighter, even though the "absolute weight" -- i.e. according to measurement as provided by a scale -- is obviously greater.  With my forearm in the arm in the arm cuff, swinging the machine normally, I was literally able to hold the handle of the machine with only my thumb and index finger -- and swing the machine effortlessly!  The sensation is that the machine FLOATS across the ground!  (For the 11" coil, the amount of counterweight needed is of course slightly less -- roughly 25 oz.)

2.  To include this amount of weight in the tube extensions, and yet not have the extensions excessively long, I must use larger-diameter carbon-fiber tube than I planned -- I've decided on 31mm outside diameter tubes.  I had intended to use the same diameter of tubing as used on the upper shaft (22.15mm outside diameter), but the extension length required was far too long.  

3.  Using the 31mm outside diameter tube for the counterweights, I calculate that length of the tube extending beyond the end of the shaft will be 7 1/2" for the 12" x 15" coil, and 6 1/2" for the 11" coil.  

4.  There would be no changes to the shaft design needed; anyone wanting the counterweight system in the future would still purchase a shaft with the same threaded female fitting installed in the butt end of the shaft, and the same threaded end cap that screws into the butt end.  The only changes would be to the counterweights themselves (as comparted to what I had originally planned) -- i.e. larger diameter carbon-fiber tubing, and thus a larger end cap for the ends of the counterweights themselves.

SO, my questions are, with the counterweight lengths needed now a pretty-well "known quantity" -- i.e. 6 1/2" and 7 1/2" long (11" coil and 12" x 15" coil, respectively), and the weights to achieve balance being also a pretty-well "known quantity" -- i.e. 25 oz. and 28 oz., respectively, would those interested in the weights find these specs acceptable?  Please offer your comments.

Preliminary/rough pricing info would be as follows.  One counterweight, $22.50 plus shipping ($30 total).  If an EQX user only wanted to order one weight, I would suggest the 6 1/2" long, 25 oz. weight, designed for the 11" coil; this amount of counterweight still achieves a degree of balance that feels GREAT with the 12" x 15" coil.  I am of the opinion that no counterweight is needed, for the 6" coil.  Two counterweights, one for the 11" coil and one for the 12" x 15" coil, $42.50 plus shipping ($50 total).  

Thoughts?

Steve

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Steve, let first me say that as I have been following your rod development your attention to detail, ingenuity, and craftsmanship appear top notch.   I am seriously considering getting either a lower shaft or full shaft system.  Nevertheless, here is my feedback per your request.

Adding 28 oz (1.75 lbs) of counterweight is still adding a lot of gross weight to a 3.2 lb the detector system (53% additional weight, though that weight is based on the stock detector rod system not yours) to compensate and balance the 23 oz total weight large coil.  That added gross weight still needs to be FULLY supported by your swing arm no matter how perfectly balanced the detector is.  After awhile, that is going to really be fatiguing.  I use a GPX.  The rear mounted under rod control box and side-saddle mounted full battery (vs. the battery harness system) tends to balance the large, heavy coils really well and it feels great when you first start your day, but my gosh, a few hours in and you are spent because the gross weight of the entire thing  just wears your arm out.  OTH I can swing the Equinox all day without fatigue even with its slight nose heaviness and that includes the large coil.  I know this because when my arm wore out using the GPX on a recent week long detecting marathon, I could pick up my Equinox and swing it around like a dream, even fatigued, and that is because the overall weight is less than half of the perfectly balanced GPX.  TBH, in a weird way, the larger coil feels more balanced to me than the stock coil.  I know this is not physically possible because the CG is the same on both coils and the large coil is 5 oz more weight, but it comes down to the fact that I am ONLY adding 5 oz of additional weight to swing that large coil and that does not present significant fatigue over time and I guess the nose heaviness never really registered for me in the first place as I adjusted the armrest forward as far as possible.

I guess, what I am saying is that it seems to me that if balance is a real issue for folks, they may be better served going to a harness setup that both provides a fulcrum balance point AND also supports a portion of the gross weight taking stress off the swing arm (even though IMO harnesses are a PITA to use in the field during target recovery) rather than adding 1.75 more pounds of gross weight to the detector system.  That's my perspective as a short, fat weak guy I guess vs. tall hulk guy who can swing nearly 4.75 pounds of detector all day long.  Light gross weight is one of the reasons why I gravitated to Equinox in the first place.  Your system is a viable alternative to the down side of using a harness, but the weight does add up and makes a difference after a few hours of swinging. Good to provide the coutnerbalance options but just thought I would provide my perspective on counterbalance systems.

BTW - remind me what are you using as the counterbalance filler?  Perhaps you can use a more dense material pushed further back in the counterbalance assembly to use moment arm to further reduce the added weight necessary for the CB?  Also, how adjustable is the CB as the moment arm will change depending on the overall rod length and the placement of the arm rest with respect to the control head handle.  I guess I am a little fuzzy on how you arrived at the set counterbalance assembly length dimensions and weights for all user shaft length configurations for different arm lengths, user heights, swing angles, etc. that would seem to me to all have an impact on the true balance point.  But I'm not a mechanical engineer, ergonomics expert, or craftsman, so I could be totally off base.

 

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Chase --

Quote

Steve, let first me say that as I have been following your rod development your attention to detail, ingenuity, and craftsmanship appear top notch.   I am seriously considering getting either a lower shaft or full shaft system.  Nevertheless, here is my feedback per your request.

Thank you for the VERY kind words!  I appreciate the compliments!

Quote

Adding 28 oz (1.75 lbs) of counterweight is still adding a lot of gross weight to a 3.2 lb the detector system (53% additional weight, though that weight is based on the stock detector rod system not yours) to compensate and balance the 23 oz total weight large coil.  That added gross weight still needs to be FULLY supported by your swing arm no matter how perfectly balanced the detector is.

You make a very good point here, which you then "flesh out" with additional supporting thoughts later in the paragraph.  Yes, I had the same concern -- and thus the reason for my post.  When I did the actual testing to discover the actual amount of weight needed to perfectly counterbalance, and realizing just the amount of weight we are talking about, it was something that made me think, a bit.  I realize that this amount of added weight could be a negative for some, EVEN THOUGH perfect balance would be achieved.

I, like you, are very little, if at all, bothered by the nose-heaviness of the Equinox.  It's almost a non-issue for me, though I do "sense" it a bit, with the 12" x 15".  But honestly, until I heard some others talking about "nose heavy" and "arm pain" and "poor EQX ergonomics," etc., I probably never would have even thought about it.  As a tall (6'2") guy, and fairly athletic (well, at least, I USED to be, LOL), the machine is not "uncomfortable" to me, at all.  BUT -- since it IS, for some others, I thought I'd try to fix that -- hence, this counterweight idea.  

I think what I'd say is this -- if you are someone, like me, who is not bothered at all by the EQX ergonomics, then the counterweights are not needed.  BUT -- if you are one of the folks who is bothered, especially to the degree where you are experiencing pain, with the EQX's ergonomics, then maybe counterweights would be an option (as would a harness, as you mentioned).

BUT -- it is here that I'd like to introduce a "new" idea -- it's a bit "long-winded," but I think it's important...

Aware of my affinity for data (as a scientist), and my tendency toward perfectionism, and then combining that with some conversations I've had with a number of folks on this issue over the past day or so, I've realized a bit of a different view, with respect to the counter-balance issue.

And that is -- WHY should I assume that PERFECT BALANCE (from the perspective of a "physics equation regarding a class 1 lever") is absolutely necessary?  IF you are interested in perfect balance (as my quirky brain is), then 25 oz. of counterweight, for a 6' 2" person using the 11" coil, and the fourth button hole from the bottom of the middle shaft, IS the "physics-perfect" counter-balance weight.

BUT WITH THAT SAID, if you are a person who feels a bit of elbow pain when swinging the EQX for several hours, why should it be assumed that you need PERFECT balance, in order to feel relief from that pain?  The fact is, the coil is applying a "downward force" at the end of a lever, and you are trying to counteract that force, using your arm.  The point of a counterweight is to counteract that force with WEIGHT, instead of your arm muscles!  BUT -- what if you removed only, say, 50% of the weight of that coil whose force your arm is trying to counteract?  In other words, instead of using 25 oz. of counterweight, what if you only used 13 oz.?  Would THAT be "enough" counter-weight, such that now, the much smaller force your arm has to "counteract," is now NOT A PROBLEM AT ALL?  

Said another way, if swinging the 6" coil on the EQX causes you ZERO issues, but swinging the 12" x 15" coil is problematic, then really all you need to do is counteract the ADDITIONAL weight that the 12" x 15" coil adds, over the 6" coil.  And since the 12" x 15" coil is roughly 50% heavier than the 6" coil (660g vs. 300g), then adding 13 oz. of counterweight, instead of 25 oz., effectively turns the 12" x 15" coil into the 6" coil, in terms of how it feels!  YES, the Equinox with the 6" coil is still quite nose-heavy, but FEW if ANY EQX users complain about "pain" or "ergonomic issues" with the 6" coil.  SO, if enough counterweight is added to make swinging the 12" x 15" coil feel EXACTLY LIKE swinging the 6" coil (i.e. still "nose heavy," but much LESS so), then is it not true to say that 13 oz. of counterweight is "enough" for many folks?

MY POINT HERE IS THIS -- I think I may be too fixated on "perfect" balance, and need to ALSO consider the idea of "improved" balance -- customized to each person's needs.

So, from that perspective, if a customer wants SOME OTHER weight, besides the "physics-equation-perfect" amount, I can EASILY produce that, as a "custom" weight, and at no additional charge. FURTHER, if a customer is NOT SURE of how much weight he or she may desire, I could perform 90% of the assembly of the counterweight, and then send it -- along with 25 or 30 ounces of LOOSE lead shot, and the "end cap" not yet attached. That way, the end user -- the customer -- could experiment with what the preferred "added weight versus reasonably balanced" point is FOR THEIR SPECIFIC DESIRES.

In other words, one could fill the counter-weight tube half way with lead, TAPE the end cap on, and go on a hunt. Good enough? Excellent. TOO HEAVY? Just untape the end cap, remove some lead, go hunt again. Then, at which point the "right" combination of extra weight vs. improved balance is found FOR YOUR PREFERENCES, then -- simply trim the tube to the length needed to contain that amount of lead shot, GLUE the end cap on, and there you have it! A "customized" counterweight that is proper for each individual's preferences! Yes, switching coils, etc., changes things a bit, as do many other variables, as you correctly pointed out, Chase.  But again, if you find the desired balance, to your satisfaction, for the 11" coil, it will still feel "pretty good" with the 15" coil, AND with the 6" coil, etc.

OR, let's say a customer just wanted me to produce a counterweight for them, that "makes my 12" x 15" coil feel exactly like my 6" coil when I'm swinging it," then I can do that, easily. I'd build them a 13 oz. counterweight...

This is where my thinking has currently evolved to, and I'd love to hear some feedback on this "adjusted" approach to "counter-balancing "that I'm pondering...

THANKS for your well-thought out points, Chase!  

Steve

 

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Agree, you should just supply a kit (large or small weight kit) that enables the user to assemble his own custom counterweight system, if needed because 1) perfect balance depends on the coil, the user height, user arm length, where they have the elbow rest and pod mounted relative to each other, rod length used, the swing angle to the vertical the user prefers, any other "accessories" a user has strapped to the rod (flashlight holder, power bank, stand assembly, pinpointer mount, etc.) and 2) as you said, perfect mechanical balance is not necessarily what is required.

Also, your design should use a high density material (weights instead of shot, tungsten putty?) that enables you to place it as far back in the assembly as possible and take advantage of the moment arm, be easy to assemble and adjust, and that minimizes overall gross weight added to the detector system.

Frankly, I question how much those who are having arm pain have adjusted their arm rest (including proper use of the strap which is essential) and detector rod length to the extent possible to alleviate the situation.  To me, the counterbalance proposition has always had more drawbacks than advantages because of the gross weight added to the overall system.  OTOH a well balanced detector design such as the F75 (though it also uses and S-shaft which can help also) that is also slightly heavier is ideal, with a harness being my second choice.  In the end, IMO, my Equinox does not strike me as a grossly imbalanced machine, unlike the person who is swinging it.

Regarding the lead shot - is it captured in a manner that precludes it from moving around and causing a racket when you swing or move the detector? Since it is shot, the volume fraction of air reduces the density overall.  Any extraneous noise  would make me truly imbalanced.  I have used tungsten putty to add weight and balance to model race cars because you can incrementally add whatever weight you need, where you need it and due to its density, you only need to use a small volume of it for a few ounces of added weight.

HTH

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Chase --

Your thoughts are greatly appreciated.  Sounds like you like the idea of letting the user "finalize" the counterweight, to their desired specs.  I think this is an alternative that many may prefer...

As for the "other ways" of doing things (changing the distance of the weight from the "fulcrum" (handle), different materials, etc.) I have thought about a good number of these issues, but haven't come up with any better alternatives or adjustments that don't drive up cost too substantially, or don't really help all that much, in the end.

Take the idea of extending the "moment arm" back farther from the handle (fulcrum).  Problem is, while this DOES help some, the amount it helps, is relatively minimal.  To move the weight say 6" farther from the handle, only reduces the amount of weight needed by a couple of ounces at most...so there's that tradeoff...

Solid weights, instead of shot, would be ideal, I agree.  However, having weights fabricated to fit inside the tubes would add to cost, substantially.  Lead shot is the cheapest "heavy" alternative, and obviously there is a need to keep the costs down, in order to sell at a price the market would bear.  Tungsten, while "putty" is a good idea, is more expensive,  and tungsten putty is slightly less dense than lead, so it would drive up cost, and actually slightly increase the volume needed to achieve the same weight.

Yes, I am working on a way to keep the lead from "rattling" inside the tubes...

THANKS for your continued brainstorming!  Each of these ideas keeps my mind working/thinking...

Steve

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Hi Steve,

Your shafts look great and you put a lot of thought and work into your systems.

I have been using a lead counterweight  for 3 months with the 15" coil.

But, as Chase says the weight does take it toll and fatigue arrives earlier. Especially for me as I have shoulder issues.

Now I am not using anything and going better - able to go longer with the lighter set up.

The key thing is to have the shaft extended correctly and not extended so far as cause an un-natural arm swing action...this is with any detector & coil combo.

But each to their own and we come in all shapes and sizes, what feels comfortable for me is not for someone else.

I wish you success with your venture.

NSC

 

 

 

P1140683.JPG

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NSC --

THANKS for the kind words!

VERY nice setup you have there; that looks VERY similar to what I'm working on!

You are completely correct about correct shaft extension length...no doubt about it.

Interesting that the extra weight caused your sore shoulder to act up.  Makes some sense though.  And that's the tradeoff -- balance makes it swing EASIER and MORE COMFORTABLE, but that is ASSUMING that the extra weight is not an issue for you.  For some it is, and they are better off with the imbalance issues; for others, it's not, in which case balance is a definite positive.

NICE job on the weight!

Steve

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Yes i thought you were counter weighting for the water only.

I was wondering what you were doing, I think the machine is a touch too heavy to be adding weight for land swinging.

That is why I said I would need a pool or wait until spring to test a counterweight.

Details my friend...lol

 

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Alluminati, 

No, I am trying to offer a way to counter-balance the machine for LAND hunters, since many have reported the nose-heaviness of the machine as being a problem -- even to the point of causing arm/elbow pain.  I'm trying to offer a solution to that issue, for those who are struggling with the imbalance/ergonomics issues with the EQX.

Steve

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SO -- HERE are my latest thoughts, based on all of the feedback here, and elsewhere.  I'd like to hear input/thoughts on the revised idea.

I am considering making the counter-weight tube of black PVC, instead of carbon fiber.

If I were to use black PVC, here are some thoughts to consider.

Using PVC, the threaded insert into the end of the shaft would not change, and the threaded end cap FOR THE SHAFT would not change (i.e. the cap used to cap the shaft whenever the counterweight is not being used). The PVC tube would screw into the shaft the same way the carbon-fiber one would.

HOWEVER -- if I use 1 1/4" PVC, there are some advantages.

1. PVC is heavier -- and since we are TRYING to add weight, heavier is better, in this case.
2. With the PVC, I will be able to add a threaded end cap onto the PVC counterweight and not have the cost of the counterweight increase from my initial pricing thoughts]; the advantage there is having the end cap that screws on and off would make it VERY easy to add/remove weight as necessary (the "adjustability" or "flexibility" that many folks have asked for, with the weights).
3. With 1 1/4" PVC, the inside diameter is larger than the carbon-fiber tube I was going to use. And therefore, the length of the PVC tube can be reduced by 30%, and still hold the exact same amount of weight (and this does not include the fact that the PVC counterweight can be even shorter still, since the tube itself weighs more than a carbon-fiber tube).

SO -- what this means is, you could make a counterweight extension only 2 1/2" long, that would give you 12 ounces of counterweight, for instance.

And 12 ounces of counterweight is 1/2 of that needed to PERFECTLY balance the 11" coil; in other words, the machine would feel MUCH better to swing with 12 oz. counterweight, AND STILL would weigh only about 3 1/2 pounds total, including the counterweight

OR, another way to look at it is, 12 ounces is the weight needed to make swinging the 12" x 15" coil feel exactly like swinging the 6" coil (i.e. it counter-balances ALL of the additional weight that the 12" x 15" coil adds to the machine, compared to having the 6" coil attached). So, if you feel the machine is comfortable with the 6", but not so, with the 12" x 15", then a 2 1/2", 12 oz. counterweight accomplishes making the 12" x 15" feel like the 6" coil.

I would still give the customer the option to have the weights sent WITH, or WITHOUT, the lead/weight included.

The only negative I can think of, going this "black PVC" route, would be that it would not be as aesthetically pleasing as a carbon-fiber tube would be. 

Thoughts?

Steve

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