Designing FID pec fly 30 decline to 30 incline - thoughts?

[Maluket]

I've been trying to design a flat/incline/decline pec fly that adjusts from 30 degrees decline to 30 degrees incline for my personal use. I would love some feedback or suggestions on what I have so far. I could easily be missing something important - I'm not an engineer, I'm not an exercise expert, and I haven't done pec flies in years. If it would actually work, or if the problems are fixable, I'll probably ask Stephen of Strength Equipment if he's interested in building it, and how much it would cost. Budget could be a factor, though I'd hate to put in all this effort and get nothing out of it.

Here's a see-through view of what I've come up with so far. Ignore that I haven't put in the pullies to lift the stack or the stuff that switches between pec and delt. That should be pretty standard stuff and I think I've left sufficient room.


PecFly1.PNG

If it isn't clear, the angle adjusts by sliding the seat along the 1" rails on linear bearings. The triangle behind the seat moves up and down at a 60 degree angle, and the seat pivots on the connection point, so that pivot point always moves at a 60 degree angle. The pivot point should remain roughly behind your chest, and so your chest should always be roughly in line with the axis of rotation of the arms of the machine, since they are also at a 60 degree angle. The triangle locks in place from the back, though it would be just as easy to pick the right or left side. With the seat fully upright, you're doing 30 degree incline pec flies. With it declined as far as it will go, you're doing 30 degree decline pec flies.

I'd want holes corresponding to 10 degree increments, and labeled as such. I haven't drawn that part.

Although it's going to be a custom piece for my own personal use, I'd like to design something good enough for general production and general use. It would give me a good sense of satisfaction to see it for sale and used by more people than just me. So for example, it should suit people of various heights (I'm 6'3"). It should be reasonably straightforward to manufacture and thus not prohibitively expensive. It should be able to handle enough weight to keep a competitive powerlifter from maxing it out, even if I don't personally need a stack that big. It should be practical to bolt together or weld together, depending on the buyer's needs. I'll get mine welded for simplicity and aesthetics.

You may note that there are still three bolts attaching one piece of the frame to the rest. It can't be fully-welded because that triangular piece needs to be able to slide on and off after powder coating.

I think one common reason that people don't consider pec fly machines to be serious is that many people can lift the whole stack on them. The picture shows a 300-pound weight stack composed of ten tens and ten twenties. This calculation is likely a little off, but in the picture, the cams have a 12.5" radius, so if they move through roughly a 90 degree arc, the cable and thus weight stack will move 12.5" * pi / 2 = about 19.5 inches. With my arms slightly bent for dumbbell flies, I'm probably moving the weight about 22 inches up. So I figure a 300 pound stack would be roughly in the neighborhood of doing dumbbell flies with 300 / 2 * 19.5 / 22 = about 133 pounds per dumbbell, which is to say a number I should never reach. Serious powerlifters can upgrade to a 400 pound stack by replacing the ten pound plates with more twenties, assuming they can stomach going anywhere near a pec fly machine in the first place.

The pivot point behind the seat back looked like a weak point to me, with it just kind of sitting out in space, which is why I sketched it with a big, impossible to break triangle of 3" tube holding it up. It might be overkill.

I'm a little worried about the strength of the "wings" holding up the rear of the seat rails. If it's a weak point, perhaps something could be bent around the frame for extra strength.

[morebarbell]

That's really cool! I hope you continue to post updates as the project progresses. What software did you use to draw the image??

[Maluket]

That's really cool! I hope you continue to post updates as the project progresses. What software did you use to draw the image??

Thanks! And I will try to remember to keep this updated.

Quick Answer: SketchUp

Long Answer: So this all started with little back-of-the-envelope sketches (literally) in pen. Clearly I needed to be able to erase, so I tracked down the only pencil in the house. I also dug through drawers until I found a ruler and a 30/60/90 degree thing. I don't remember when I bought them, but it's possible they're as old as when I was in gradeschool and used to draw cars. Well, the pencil was clearly newer since the eraser wasn't a rock. So I drew a number of iterations on paper that way. Since I have no idea what I'm doing, I kept making mistakes of the "oh, that won't work in the real world for this reason" variety (and may still be making some of those). But eventually, I ran out of pencil eraser. Buy more pencils? Hah! Too simple! No, time to find a free CAD program and teach myself CAD. SketchUp seemed to be reasonably-well-liked for freeware. I figured it would be easier to see how the parts moved that way, and easier to see it from multiple angles. Well, I'm not sure I'd describe teaching myself CAD as easy, and I've not figured out how to move parts in any quick way, but at least it's involved less swearing than I expected. I made a handful of mistakes while drawing it in SketchUp too, but they were small and easily fixed.

[vic84875]

Linear bearing for the seat adjustment?, i will say no. In that application, bushing is smooth enough. You will save big bucks.

I think that if you are going to change the angle of the seat; you will also need to make the handles -angle/adjustable-, so they always can be set parallell to the back-pad ; otherwise it will be very akward on your wrists.

I would not put to much time and effort into the seat adjustability, but, i will put that time and effort into making a pec fly-pec deck- rear delt, super combo.

If you have the will power; i advise to you learning AutoCAD. Even if you are not an engineer, it is a precission tool and it will save you time in sketching for the rest of your life.

Anyways, good idea.

[2MoreRepz]

Impressive, reps added! It looks to be somewhat similar to the Fly on the 1st Gen Nautilus Double Chest. The seat adjustment is simple but genius! Keep us updated.

[Maluket]

Yeah, the linear bearings only showed up in the most recent couple drawings. I didn't want to throw in expensive components like that, but I began worrying that with three separate shafts, the total friction would add up enough to make adjusting the seat difficult and annoying. I could be wrong. Maybe I should keep both designs, and discuss it with Stephen if/when I go to get this actually built. I don't feel any need to spend more for something "better" if it's not actually improving the function and usability of the machine.

I don't think you want the handles always parallel to the back pad. I think you want the handles perpendicular to your arms, as they would be with dumbbells.



I'd love to be using the industry standard, but AutoCAD only has a 30 day free trial, and costs $4195, so it's not really an option for me.

[Maluket]

Impressive, reps added! It looks to be somewhat similar to the Fly on the 1st Gen Nautilus Double Chest. The seat adjustment is simple but genius! Keep us updated.

Thanks! Here are some pictures of the seat settings from 30 incline through 30 decline (hmmm, 5 pictures max... skipping 20 incline). Reading my original explanation, it seems even less clear than the original picture. Now if you look carefully, you'll notice that, when looked at perpendicular to the seat moving from the pivot point, the arms pull further away from the seat the more you are inclined or declined. However, you'll also be up higher in the seat in full incline, and slide down in it in full decline, which looks like it would compensate. They're all small distances anyway. And that's good, because it's not perfect for all heights. Shorter people will find themselves closer in decline and farther in incline. Taller people will have the opposite problem. I doubt it will be noticeable.








PecFly30i.PNG
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PecFly0.PNG
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PecFly30d.PNG

[rlundregan]

Thanks! Here are some pictures of the seat settings from 30 incline through 30 decline (hmmm, 5 pictures max... skipping 20 incline). Reading my original explanation, it seems even less clear than the original picture. Now if you look carefully, you'll notice that, when looked at perpendicular to the seat moving from the pivot point, the arms pull further away from the seat the more you are inclined or declined. However, you'll also be up higher in the seat in full incline, and slide down in it in full decline, which looks like it would compensate. They're all small distances anyway. And that's good, because it's not perfect for all heights. Shorter people will find themselves closer in decline and farther in incline. Taller people will have the opposite problem. I doubt it will be noticeable.








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Your explanation here is much clearer than the original. I started to respond to your first post, but after reading it a few times, my response was dumb, so I deleted it. I like the concept of moving the seat to change the angle. I'm sure you can find a way to minimize the distance of the user from the arms.

[ygohome]

Cool Maluket. It is nice to see someone making their own stuff.

Once you get a prototype created you should be able to see right away where any changes are needed. Or are you planning on making just one for yourself and thats it?

I'd probably look into getting a patent if it isn't too expensive to do.

[Maluket]

Ah, I see a problem. The holes for 30 degrees and 20 degrees incline are only 7/16 of an inch apart, center to center, and they're also 7/16 of an inch in diameter... so the first two holes are touching. Even if they weren't, being off by a fraction of an inch in positioning the holes would correspond to being off by a significant angle. That also means that any slop in the system would correspond to a pretty shaky seat tilt-wise near the top. I think I need to put the seat adjustments on the bottom.

If I'm adding a square rail to the bottom for that, though, it seems like I should drop the linear bearings, and go with two square rails on the bottom. That aligns with what vic84875 seemed to be suggesting anyway, and is closer to earlier iterations of the thing.

I had problems with that approach too, though. I need to remind myself exactly what they were.

[Maluket]

Cool Maluket. It is nice to see someone making their own stuff.

Once you get a prototype created you should be able to see right away where any changes are needed. Or are you planning on making just one for yourself and thats it?

I'd probably look into getting a patent if it isn't too expensive to do.

I'm not planning to get into manufacturing or to make multiple iterations, so I kind of need to nail it on the first try. I figured that once I had something that looked good to me, I'd see if Stephen of Strength Equipment (http://www.strengthequipment.net/) wanted to build it for me. He's done good work for me in the past, and has the experience to know what will work and what won't.

If such a simple concept is patentable, I don't know what to say about the patent office. To me, there are only a few ways to make a seat recline. This is just one of them. It seems nuts if that's patentable, or the specific use of such a basic concept is patentable. I guess I could look into it, though. Stranger things have happened in the patent office, or maybe I'm already violating someone's patent of "seat recline method #3 for fitness equipment purposes".

[Maluket]

Your explanation here is much clearer than the original. I started to respond to your first post, but after reading it a few times, my response was dumb, so I deleted it. I like the concept of moving the seat to change the angle. I'm sure you can find a way to minimize the distance of the user from the arms.

Heh, and my original explanation was dumb. Much clearer in pictures, I think.

I've assumed that we want the axis of rotation to pass through the user's shoulder joints, so maybe two or three inches forward from the pad. If that's wrong, it's easy to move things in or out to get something closer to ideal.

[rlundregan]

I'm not planning to get into manufacturing or to make multiple iterations, so I kind of need to nail it on the first try. I figured that once I had something that looked good to me, I'd see if Stephen of Strength Equipment (http://www.strengthequipment.net/) wanted to build it for me. He's done good work for me in the past, and has the experience to know what will work and what won't.

If such a simple concept is patentable, I don't know what to say about the patent office. To me, there are only a few ways to make a seat recline. This is just one of them. It seems nuts if that's patentable, or the specific use of such a basic concept is patentable. I guess I could look into it, though. Stranger things have happened in the patent office, or maybe I'm already violating someone's patent of "seat recline method #3 for fitness equipment purposes".

You and Stephen seem to have a pretty good working relationship, it might be worthwhile for you to design the thing together. It could lead to something that would be patentable, and could sell pretty well. I'm not knowledgeable about the fly machines that are available, but I'm not aware of any with adjustable angles like you are considering. If you can produce that and make it useful for rear delts, you could really be on to something....

[Maluket]

You and Stephen seem to have a pretty good working relationship, it might be worthwhile for you to design the thing together. It could lead to something that would be patentable, and could sell pretty well. I'm not knowledgeable about the fly machines that are available, but I'm not aware of any with adjustable angles like you are considering. If you can produce that and make it useful for rear delts, you could really be on to something....

Well, "working relationship" being that he custom made me a couple pieces in the past and I was very happy with them. He probably wouldn't even remember me until reminded what I bought. I've never even talked to him on the phone, just sent a lot of emails back and forth. The two pieces were simpler to describe, more like "just like this machine but a little different". He was easy to work with, his prices were competitive, and the quality was very high.

Yeah, I couldn't find anything adjustable either. I understand that Tyler Hobson of Rogers Athletic is working on one, but that it's only going to vary between 10 and 20 degrees. I figured if I was going to splurge for something "fluffy" like a pec fly / rear delt machine, it should be as flexible and capable as possible.

I think it would work pretty well for rear delts, but not really be ideal. Your face will be mashed into the seat, worse if you're doing decline. That said, I suspect that you really want some incline for rear delt, or you'll bring too much back into it. I'm not sure, though. When I used to do rear delt on my old Bowflex, it felt good doing them on an incline. But that's a Bowflex.

Maybe I need to make a removable head rest, just something that slips on and off. Slip it on when doing pec flies with enough of an angle to want the neck support. Slip it off for rear delt.

[Maluket]

...I think I need to put the seat adjustments on the bottom...

I could add a square rail to the bottom without adding any friction. It's just a positioning rail, not a load-bearing rail. My GHD uses that approach. The seat is starting to look kind of science-fictiony.


PecFlySeat1.PNG

[daniel327]

I think I need to put the seat adjustments on the bottom.

Also, you might benefit from adding a minor incline to the seat par to prevent yourself from sliding down the machine.

[Maluket]

Also, you might benefit from adding a minor incline to the seat par to prevent yourself from sliding down the machine.

An excellent idea. Thanks!

Edit: A fixed incline to the seat bottom would mean you're kind of squished when doing 30 degree incline flies. An older design used a seat bottom on a hinge so that it would incline and decline with the seat back. But sitting on a hinge seemed fragile, and not as good for rear delt somehow, where I'd rather sit flat. So I guess the question is - is it better to be held more securely for declines and be a little squished for max incline? Or is it better to just have to brace yourself with your feet on the ground in decline? Or is there some different approach that avoids these trade offs completely? There might be a way to allow the bottom to separately adjust angle, for instance. I'd wanted to keep required adjustments to a minimum, but maybe it's worth it here if there's a good way.

[Maluket]

I'd probably look into getting a patent if it isn't too expensive to do.

Looks like it's too expensive to do. Per Wikipedia:

"In the United States, in 2000 cost of obtaining patent (patent prosecution) was estimated from $10,000 to $30,000 per patent...

Alternatives to applying for a patent

A defensive publication is the act of publishing a detailed description of a new invention without patenting it, so as to establish prior art and public identification as the creator/originator of an invention, although a defensive publication can also be anonymous. A defensive publication prevents others from later being able to patent the invention."

So I guess this thread is my "defensive publication", assuming this design of how to do the incline/decline while staying properly oriented to the arms isn't already floating around or patented. I gather it means that others can use the idea freely, just not patent it (assuming the patent office finds this as prior art).

[qaz123]

I think the pivot points need to always be directly above your shoulder joints and I am not sure that would be the case with this design.

[Maluket]

I think the pivot points need to always be directly above your shoulder joints and I am not sure that would be the case with this design.

You know, I kept drawing for having the pivot axes going through where I'd typically grab the handles, which is to say mid chest. But of course it needs to go through the shoulder joint as you say. You can grab the handles lower, but it still has to pivot through the shoulder joint to match your anatomy.

It should be fixable by moving the rear hinge part up a few inches to be at the shoulder joint instead of mid chest, and then following the consequences through the rest of the machine.

So yeah, I think you're right, and I had it wrong. Thanks for spotting that! Reps on recharge.

[qaz123]

Maybe make the whole bench and seat so they slide forward and backwards as one unit independently of their adjustments in angle.

Kind of like the pendulum shoulder/incline machine from MD's thread.

[vic84875]

I see your point, but it is hard to emulate the dumbbell movement with a machine.

There is a pec fly machine, plate loaded, i believe it is manufacturer by hammer strenght, were the arms are independent, and it has a setup of bearings that allowed 6 degrees of freedom. Sorry, I can not find the link today (maybe someone can help)!). Your best bet will be to emulate that machine, with an independent pulley system, and stack, for each arm. I think that with your design, the wrists are going to suffer, the motion just does do not look natural.

Wow!. Students, professionals, corporate employees, etc, get autoCAD for free some way or another. I was not aware of that price tag, ridiculous. I do not recommend it anymore. Has been around for years, i learn to use it over 10 years ago in high school (First version was DOS based) primary controls remain the same, and most users do not need the last version, maybe you can get a 6 years old version, used, for $20 or something.

Good job on your sketches,illustrated your designs very clearly.

[Maluket]

I think the pivot points need to always be directly above your shoulder joints and I am not sure that would be the case with this design.

OK, fixed. Not that the picture looks much different, but the pivot axes should now go through your shoulder joints at all settings, or at least roughly so. Depends on height and build and all that.


PecFly3.PNG

Maybe make the whole bench and seat so they slide forward and backwards as one unit independently of their adjustments in angle.

Kind of like the pendulum shoulder/incline machine from MD's thread.

Well, yes, and I admit I hadn't thought about it. Having an inclining seat where you can move the whole thing forward and back would seem to solve any problems getting yourself aligned. Add up and down movement for total adjustability. There should always be some setting that puts the pivot axes through your shoulder joints at the right incline. It would also be easy to set the thing up wrong. But once you'd owned it a while, you'd know exactly which settings felt right to you.

What I was trying to do was keep it simple - only one adjustment, and it automatically keeps you aligned with the pivot axes. Do 20 degree declines, hop off, one click and you're at 10 degree inclines or whatever else you wanted. But it's possible it was just the wrong solution, too simplistic. One size fits all rarely fits all.

Hmmmmm.

[qaz123]

OK, fixed. Not that the picture looks much different, but the pivot axes should now go through your shoulder joints at all settings, or at least roughly so. Depends on height and build and all that.


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Well, yes, and I admit I hadn't thought about it. Having an inclining seat where you can move the whole thing forward and back would seem to solve any problems getting yourself aligned. Add up and down movement for total adjustability. There should always be some setting that puts the pivot axes through your shoulder joints at the right incline. It would also be easy to set the thing up wrong. But once you'd owned it a while, you'd know exactly which settings felt right to you.

What I was trying to do was keep it simple - only one adjustment, and it automatically keeps you aligned with the pivot axes. Do 20 degree declines, hop off, one click and you're at 10 degree inclines or whatever else you wanted. But it's possible it was just the wrong solution, too simplistic. One size fits all rarely fits all.

Hmmmmm.

if it is mainly for you I would make it as adjustable as possible and mark your favorite settings with different colored sharpies or something.

[spikeo]

you dont need to make the whole bench incline/decline to attack the upper/lower pecs-if thats your reasoning behind it. You have to with a bar/db's because you are always pushing vertically against old mate gravity, but on a pec deck if you adjust the seat down your arm-torso angle opens up engaging more upper pec.
eg. flat bech your arms move at 90 deg to your torso, at a 30 deg incline your arms are at 120 deg to torso.

Apart from that i love the way you are adjusting the bench angle! simple but brilliant

[Maluket]

you dont need to make the whole bench incline/decline to attack the upper/lower pecs-if thats your reasoning behind it. You have to with a bar/db's because you are always pushing vertically against old mate gravity, but on a pec deck if you adjust the seat down your arm-torso angle opens up engaging more upper pec.
eg. flat bech your arms move at 90 deg to your torso, at a 30 deg incline your arms are at 120 deg to torso.

Yeah, that was my reasoning behind it. I understand what you're saying, but if moving your hands up and down is just as good as actual incline and decline, why are there so many incline and decline pec decks? Is it just a marketing gimmick for the unaware, or is there more to it? I've assumed that having the motion centered on your shoulders instead of above or below would just be a better motion to engage the muscles properly and fully.

Apart from that i love the way you are adjusting the bench angle! simple but brilliant

Thanks! But I'm now leaning in the direction that qaz123 suggested - having an independent angle adjustment. If I was a manufacturer, I could see making some prototypes and setting it up so that you get the best settings for the greatest number of people with a single adjustment as per my original design. But I'm not a manufacturer. I'm just some guy that wants a piece of equipment. I can't afford to make a "prototype" only to find out it doesn't fit me like I thought it would. It's a safer bet to have (at least) two adjustments instead. I think I have that approach almost worked out, at least for comparison purposes. It's actually simpler in some ways.

[fishpat86]

Yeah, the linear bearings only showed up in the most recent couple drawings. I didn't want to throw in expensive components like that, but I began worrying that with three separate shafts, the total friction would add up enough to make adjusting the seat difficult and annoying. I could be wrong. Maybe I should keep both designs, and discuss it with Stephen if/when I go to get this actually built. I don't feel any need to spend more for something "better" if it's not actually improving the function and usability of the machine.

I don't think you want the handles always parallel to the back pad. I think you want the handles perpendicular to your arms, as they would be with dumbbells.



I'd love to be using the industry standard, but AutoCAD only has a 30 day free trial, and costs $4195, so it's not really an option for me.

Project looks interesting, not sure about the biomechanics of it though but I am hungry so not firing on all cylinders in the brain department.

As for the bolded part. I am a CAD Technician and believe me you should be glad you don't have AutoCAD 3D as it is an absolute ****er to learn. I do civil engineering drawings/models and BIM models and they are an absolute ****er to work with!

EDIT: Just seen post #7, looks good!

[Maluket]

Maybe make the whole bench and seat so they slide forward and backwards as one unit independently of their adjustments in angle.

Kind of like the pendulum shoulder/incline machine from MD's thread.

if it is mainly for you I would make it as adjustable as possible and mark your favorite settings with different colored sharpies or something.

OK, here's a possible approach along those lines to accomplish the same thing without being the same sort of mechanism as the Pendulum. I pushed the rails apart more since they're now more critical for stability since there's no third point of bracing like before. It should move back and forth on the rails super smoothly now since we've eliminated the rear triangle piece with its friction. The middle rail is just for positioning and frame strength and doesn't touch the seat other than through the pin thing. The seat back angle adjusts on a disk with holes along the edge (holes not shown). It's a simpler design in some ways, doesn't require any bolting, and is more forgiving of design mistakes. It should have enough range of adjustment that just about anyone could get comfortable on it unless your feet don't touch the ground, but it's two inches shorter than my bench, so hopefully that's not a problem for most people. It'll certainly work for me at 6'3", and it's a simple design modification to lower it if necessary for the mass production that's never going to happen but I'm pretending is a constraint.


PecFlyB1.PNG


PecFlyB2.PNG

[qaz123]

Definitely on the right track I think.

[vic84875]

http://www.youtube.com/watch?v=V7BAh-qUMOU

I found it !. Minute 3:45; aprox

Before; i was telling you that if you want to emulate a dumbbell movement, perhaps, these machine will be better. I do not own one, but when i'm on the road i train at commertial gyms (no place like home), and they are quite nice, the motion has a natural feeling. Also, it is easier to manufacture and it is less expensive.