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View dakremer's profile

Awesome new hardware. Question....

by dakremer
posted 748 days ago


45 replies so far

View junebug's profile

junebug

82 posts in 1028 days


#1 posted 748 days ago

At 10” out, the hinge would support 45 lbs. The way the description is written, that load capacity is for each hinge

View dakremer's profile

dakremer

2449 posts in 1715 days


#2 posted 748 days ago

Thanks Junebug!

-- Hey you dang woodchucks, quit chucking my wood!!!!

View Milo's profile

Milo

851 posts in 1943 days


#3 posted 748 days ago

dak, maybe it would help if you told us what the project is? Something about that hinge is tickling the back of my brain, but my subconscious hasn’t dredged it up yet. If you share what your doing, maybe that would help.

-- Beer, Beer, Thank God for Beer. It's my way of keeping my mind fresh and clear...

View dakremer's profile

dakremer

2449 posts in 1715 days


#4 posted 748 days ago

if you look at my projects, recently I’ve been making Cervical Chairs. These chairs are used in chiropractic offices and needs to have the ability to adjust the backrest to different angles. It also needs the ability to fold all the way to the ground.

this design has been used for probably the last 60+ years. Its time for a re-inventing of the wheel. I’m trying to get rid of the clutter of that back mechanism and replace it with these hinges. With the mechanism in the pictures above, you are limited in the angle of your backrest by how many notches you cut out of the block at the bottom. With these new hinges, you can recline in increments of 10 degrees and lock it in place. Plus it’ll make it look less cluttered in the back and more modern. It also opens up the possibility of new designs of the chair….more aesthetically pleasing designs

I think these hinges are awesome! I’m really glad I stumbled upon them. Just wish they were cheaper.

-- Hey you dang woodchucks, quit chucking my wood!!!!

View Bertha's profile

Bertha

12951 posts in 1317 days


#5 posted 748 days ago

These are pretty slick. The thermoplastic ones seem plenty strong for your application. And you’re right, it’ll clean up that mechanism substantially.
.
In before someone accuses you of working for this company, lol;)

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog

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dakremer

2449 posts in 1715 days


#6 posted 748 days ago

haha…i dont work for this company, or have any affiliation with them at all! :) But they are pretty slick!

Here is the home page of their site, showing all their hinge models. I emailed them and they sent me a price list. If you are interested in the prices, just PM me. (not sure they want me publishing their prices, since they dont have them listed on their website)

-- Hey you dang woodchucks, quit chucking my wood!!!!

View Bertha's profile

Bertha

12951 posts in 1317 days


#7 posted 748 days ago

^yeah, that’s kind of sleazy to post private pricing. A fellow Texan was kind enough to provide me a new product to evaluate and I was seized upon for my “endorsement”. Lol, I’m headed over to that site. Thanks! al

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog

View 404 - Not Found's profile

404 - Not Found

2544 posts in 1593 days


#8 posted 748 days ago

I wouldn’t have thought adding $200 for metal hinges in a specialized chair like that would be a problem.
Anything produced as an aid for people living with disabilities or medical problems are priced at a premium anyway – just because they’re not mass produced in China.
Those hinges look perfect for that application, whilst the plastic one are attractively priced, are they worth taking a chance on when you know there are more robust ones available?
Of course the thing to do would be to try a pair – If they are adequate for a normal size person, you could always put a disclaimer on the chair (Not to exceed 180lbs etc.,), If you are making one for a super-obese person, use the metal and price accordingly.
Just a thought.

View dakremer's profile

dakremer

2449 posts in 1715 days


#9 posted 748 days ago

I agree with you Renners. As of now though, I’m in the beginning stages of designing this chair. I was going to use the plastic ones on my prototypes to save some money and to see if the plastic ones are sufficient. If I ever took this to the “next level,” then the metal ones would be the way to go for sure! Unless I make a “cheaper” model with the plastic hinges, and the disclaimer would be a good idea!

-- Hey you dang woodchucks, quit chucking my wood!!!!

View Gene Howe's profile

Gene Howe

5501 posts in 2052 days


#10 posted 748 days ago

Dak,
My Chiro often sits/kneels on my 230 lbs to perform his magic. Unless the chair is only used as a place to sit, I’d go with the metal.

-- Gene 'The true soldier fights not because he hates what is in front of him, but because he loves what is behind him.' G. K. Chesterton

View dakremer's profile

dakremer

2449 posts in 1715 days


#11 posted 748 days ago

There will be no force added to the load on the hinges besides from the weight of the person leaning back on them. With 2 hinges, they will (apparently) take about 90lbs of force 10” from the hinge. This is probably borderline sufficient. Not sure what the typical force exerted on a backrest is. If upgraded to the metal ones, it’d be rated at around 250lbs of force at 10” out. That is plenty strong.

-- Hey you dang woodchucks, quit chucking my wood!!!!

View Doss's profile

Doss

779 posts in 888 days


#12 posted 747 days ago

First, keep in mind I’m working (at work) so I’m doing this fast and loose with little checking or fancy calculus and larger static force calculations.

These are pretty slick. The thermoplastic ones seem plenty strong for your application. And you’re right, it’ll clean up that mechanism substantially.Bertha

There will be no force added to the load on the hinges besides from the weight of the person leaning back on them. With 2 hinges, they will (apparently) take about 90lbs of force 10” from the hinge. This is probably borderline sufficient. Not sure what the typical force exerted on a backrest is. If upgraded to the metal ones, it’d be rated at around 250lbs of force at 10” out. That is plenty strong.dakremer

Incorrect. About 87.5 lbs 10” out.

If they are adequate for a normal size person, you could always put a disclaimer on the chair (Not to exceed 180lbs etc.,)Bertha

Not true. Disclaimer won’t save you from standards (BIFMA in this case… though I’m not sure if they apply specifically to your type of chair).

This hinge is not sufficient. Doubling that hinge (the math may not work out correctly):
450 lb-in = 37.5 lb-ft x 2 = 75 lb-ft

Commercial-grade furniture is usually tested at (for chair backs) 150 lbs for 1 minute @ 16” distributed via foam block and rope which is followed by a 200 lbs proof load test (can break but cannot catastrophically fail).

Translating that quickly,
16 in = 1.333 ft
150 lbs x 1.333 ft = ~200 lb-ft at the fulcrum (the hinge)

or using your 10” number:
10 in = .8333 ft
150 lbs x .8333 ft = 124.95 lbs at the hinge (I don’t know if you can scale the lbs down due to shorter distance, but it would make sense so: 125 lbs x .8333 ft = 104 lb-ft at the hinge)

I don’t know if your specific chair has to come anywhere close to that standard, but it’s something to consider.

Also, for the proof load:
200 lbs x 1.333 ft = 266 lb-ft at the hinge
Your number: 200 lbs x .8333 ft = 167 lb-ft at the hinge

These are just quick, simplified calculations and may not apply to what you are doing, but I don’t think those hinges are going to work.

If you’re going to risk it, do so with the aluminum or stainless steel ones. If you don’t want any risk, use the steel ones (not stainless). They give you over double the capacity.

-- "Well, at least we can still use it as firewood... maybe." - Doss

View dakremer's profile

dakremer

2449 posts in 1715 days


#13 posted 747 days ago

That’s what I was looking for Doss. I wasn’t sure what the standard was for chair backs. It seems like the hinge will technically function, but just might not meet standards. I think I understand your calculations, and it seems right.

If I upgrade to the metal hinge (which has 1200 in-lbs of torque) that would give me 100 lbs at 12”. At 16” each hinge will have 75lbs support. Multiply by two (hinges) and u get 150lbs at 16”.

The top of my back rest will only be about 14-16” away from fulcrum.

I need to find out the standard for “medical” equipment

-- Hey you dang woodchucks, quit chucking my wood!!!!

View Steve Peterson's profile

Steve Peterson

244 posts in 1706 days


#14 posted 747 days ago

My guess is that “medical” equipment needs to be built with huge safety margins. They definately do not want to take any chance of failure because of the high risk of lawsuits. They should be used to paying for medical grade equipment.

I vote for using the metal hinges. The basic model could use 2 of them. The enhanced model could use 3 or 4 for additional margin.

-- Steve

View Doss's profile

Doss

779 posts in 888 days


#15 posted 747 days ago

No problem. I hope you understand I wasn’t trying to be rude about it. Just typing fast and straight-forward.

EDITED
At 16”, it would be 75 lbs. Times 2 = about 150 lbs

Now that I see that number, 2 steel hinges are looking sketchy too. I was factoring in the 10” number you gave earlier for the seat back. To pass this spec, you’d need at least 3 of your hinges in steel. That still may be a cleaner look overall if incorporated properly. Might as well go to 4 if you do that though.

You may want to investigate ratcheting hinges. They seem like they can take a lot more load considering their design allows for it.

-- "Well, at least we can still use it as firewood... maybe." - Doss

View dakremer's profile

dakremer

2449 posts in 1715 days


#16 posted 747 days ago

To figure out, isn’t it just 1200 In-lb divided by 16”, which gives you 75 lb at 16”?

The height of my backrest is only going to be 14” tall….If this is the case, then I only have to figure for 14” not 16” correct? The reason I chose 10” above is bc I figured the backrest will be 14” tall and the weight of the patient won’t be pushing against the very top of the backrest. The weight will be centered probably 2-4 inches below the top

-- Hey you dang woodchucks, quit chucking my wood!!!!

View MrRon's profile

MrRon

2786 posts in 1867 days


#17 posted 747 days ago

You might try looking into the seat adjusting mechanism used for car seats. Also check this out…http://www.alibaba.com/showroom/seat-adjuster.html

View dakremer's profile

dakremer

2449 posts in 1715 days


#18 posted 747 days ago

MrRon, those are a good thought but I don’t think those have the range I need. I need at lease 150ish degrees of rotation (maybe more). Also on that website I don’t think u can order just a few. You have to order a bunch of them

-- Hey you dang woodchucks, quit chucking my wood!!!!

View Doss's profile

Doss

779 posts in 888 days


#19 posted 747 days ago

You might try looking into the seat adjusting mechanism used for car seats.MrRon

Those are ratcheting hinges :-) Some though (on Euro cars like VWs and Audis) are fancy ratchets.

Dakremer, I told you I was calculating fast. I started doing some simplifying knowing dang well that’s not how you do it. LOL I went back up to my previous post and couldn’t even figure out where I got those numbers from (I ran out to lunch first).

So, T = FD

100 lb-ft = F(1.333 ft) => 100 lbs / 1.333 = 75 lbs

Sorry for the confusion.

-- "Well, at least we can still use it as firewood... maybe." - Doss

View junebug's profile

junebug

82 posts in 1028 days


#20 posted 747 days ago

are you looking to make these for sale, or is it a gift to a friend? I ask because there is a 5:1 safety factor in their calc’s. I know you cant take the extra capacity into account if you plan on selling them, but if its for a friend, that might be a different story. At least for a proof of concept

View Doss's profile

Doss

779 posts in 888 days


#21 posted 747 days ago

Is that 5:1 generated on a proof load, maximum load, or based off of some perceived total of their actual usage application?

-- "Well, at least we can still use it as firewood... maybe." - Doss

View Bertha's profile

Bertha

12951 posts in 1317 days


#22 posted 747 days ago

If they are adequate for a normal size person, you could always put a disclaimer on the chair (Not to exceed 180lbs etc.,) – Bertha
.
I don’t remember saying that.
.
Where did I read the stats on the thermoplastic ones? I thought they were rated for hundreds of pounds?
Edit: I also must misunderstand how the chair is to be used. Why would such loading occur a foot out on the lever? Simply commonsensically, not mathmatically, I would expect the chair to flip before a hinge would fail (?). How big are these friggin patients, lol? :)

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog

View dakremer's profile

dakremer

2449 posts in 1715 days


#23 posted 747 days ago

The patient will sit on the chair like any normal chair. They will be resting on the back rest set at different angles…

What does this 5:1 thing mean?

-- Hey you dang woodchucks, quit chucking my wood!!!!

View dakremer's profile

dakremer

2449 posts in 1715 days


#24 posted 747 days ago

Right now it is just for proof of concept. Right now I’m just building the prototype. I plan on selling these to students at school for practice chairs. However if design is right, someday I might want to consider selling these “legally” and for in office intended use….

-- Hey you dang woodchucks, quit chucking my wood!!!!

View DS's profile

DS

2131 posts in 1044 days


#25 posted 747 days ago

Seems to me, without getting too much in depth into this issue, that standard reclining chair hinges could be adapted to your application. My local Louis and Company (Werth & Co. now, I think) carries them.

-- "Hard work is not defined by the difficulty of the task as much as a person's desire to perform it.", DS251

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dakremer

2449 posts in 1715 days


#26 posted 747 days ago

Reclining chair hinges won’t give me the degree of rotation that I need, and won’t allow me to lock the position of the recline. I need to be able to lock the back rest at certain angles, and also flip the backrest all the way down.

-- Hey you dang woodchucks, quit chucking my wood!!!!

View DaddyZ's profile

DaddyZ

2380 posts in 1664 days


#27 posted 747 days ago

Even with Locking hinges you will still need the Support (leg) for the Floor when open all the way. you wouldn’t want the Patient to fall over in the chair…

But I do agree the Idea could be improved upon, how about a telescoping rod in back that reaches the floor instead of notches in a chunk of wood…

-- Pat - Worker of Wood, Collector of Tools, Father of one

View Jim Jakosh's profile

Jim Jakosh

11277 posts in 1729 days


#28 posted 747 days ago

Junebug said it: 45 lbs x 10 ” = 450 inch lbs. But they seem to be way too light for the back rest on a chair. I would not think I’d use a metal hinge of that type. It seem pretty small- especially if it would take an impact for someone losing their balance and hitting it hard. The force goes way up in that situation.

If you are going to build these to sell, check the BIFMA ( Business and industry Furniture Manufacturing Assoc) standards. If you had a failure and someone got hurt, that would be what they would be held to in the market place!
I worked in QA for a furniture manufacturer, and we had to test the heck out of products to meet the standards.

A ratcheting support that cannot fall out accidentally would be my choice to meet your needs.

Good luck, Jim

-- Jim Jakosh.....Practical Wood Products...........Learn something new every day!! Variety is the Spice of Life!!

View Doss's profile

Doss

779 posts in 888 days


#29 posted 747 days ago

How big are these friggin patients, lol? :)Bertha

What I was thinking too.

If they are adequate for a normal size person, you could always put a disclaimer on the chair (Not to exceed 180lbs etc.,) – Bertha
.
I don’t remember saying that.
Bertha

That’s because you didn’t. LOL TOTALLY my fault (Doss is taking full responsibility) on the misquote. That was renners, not you. I apologize. Like I said, I was in a rush at work posting up.

Jim is reflecting my exact thoughts.

-- "Well, at least we can still use it as firewood... maybe." - Doss

View dakremer's profile

dakremer

2449 posts in 1715 days


#30 posted 747 days ago

I’ll respond to everyone later tonight. I’m on my iPhone right now and don’t want to type it all out!

This is exactly why I love LJs. Lots of people with lots of good ideas to troubleshoot problems with each other. Thanks for all the help so far!

-- Hey you dang woodchucks, quit chucking my wood!!!!

View dakremer's profile

dakremer

2449 posts in 1715 days


#31 posted 747 days ago

I’m actually almost done making one of the cervical chairs and I’ll add more pics/video of chair in action and how it’ll be used….

-- Hey you dang woodchucks, quit chucking my wood!!!!

View dakremer's profile

dakremer

2449 posts in 1715 days


#32 posted 747 days ago

Here are some pictures of the chair I finished tonight….

-- Hey you dang woodchucks, quit chucking my wood!!!!

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dakremer

2449 posts in 1715 days


#33 posted 747 days ago

-- Hey you dang woodchucks, quit chucking my wood!!!!

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dakremer

2449 posts in 1715 days


#34 posted 747 days ago

So the purpose of this chair is for cervical chiropractic adjustments – hence the name Cervical Chair… The patient will sit in the chair while the chiropractor stands behind them and palpates their neck. The doc will/can also perform the adjustment as the patient sits in the chair. The reason for the reclining backrest, is because if a patient is too tall for the doc, then we recline the backrest to lower them to a good working height – this is better than them slouching into a lower position, to keep their spine in a more stable, relaxed position.

The reason for the backrest to fall all the way to the floor (like in the last picture), is to have the ability to palpate the entire spine, perform orthopedics, and for better positioning of patient/doctor during certain adjustments.

The reason I would like to use these new hinges that we are discussing is because the pictures you are looking at above are about the same as what you would have found 60+ years ago. The design has not changed really at all. It is obviously a time-proven and safe mechanism. However the mechanism in the back doesnt lend itself to much design change. The chair to me, looks old fashion. I’d like to modernize it, by removing all that clutter on the back of the chair. Also as you can see, this chair is very limited in the different backrest angles it can achieve…

-- Hey you dang woodchucks, quit chucking my wood!!!!

View dakremer's profile

dakremer

2449 posts in 1715 days


#35 posted 747 days ago

These new hinges will allow me to total redefine the look of the Cervical Chair, and allow for more angle choices for the doctor during his exam and adjustment.

The only force that will be applied to the backrest is the weight of the patient leaning against it…

Does that 5:1 safety ratio mean that it can technically hold 5 times the amount of weight, but its only meant for the listed weight??? I still dont get this.

-- Hey you dang woodchucks, quit chucking my wood!!!!

View Lifesaver2000's profile

Lifesaver2000

512 posts in 1736 days


#36 posted 747 days ago

I can’t really help any with information about using the hinges, but after looking at the chair you have posted (which looks very nice BTW), I having been having some thoughts about how your new design would change the workflow of the practitioner who would be using this chair.

What I see with your current (old) design, is that the user would apply just enough pressure to the back of the chair to support the patient’s weight and release the support, then raise or lower the back to the desired position. I could see where the practitioner could easily do this while remaining in a comfortable standing position.

If I understand how the new hinges work, the new workflow would be to support the weight, bend down and release the hinge on one side, reach over and release the hinge on the other side, move to the desired position, then again reach to each side separately to lock in the hinges. Several additional steps, along with having to find and manipulate what appears to be a rather small knob for the situation (although this might be replaced with something larger).

I don’t claim to know anything about how a chiropractor works, but it seems to me that the second process I describe would be much more troublesome for the practitioner than the first. If this change in the seat back position is not done very often, it might not matter, and might be worth the extra trouble for the increased versatility.

I only mention this because I have in my own work encountered changes in how thing are done that, while making for a more streamlined or attractive appearance, make the actual work much less convenient. I am curious if you have “gone through the motions” of how the chair would operate with your new design, versus the old-fashioned method.

View dakremer's profile

dakremer

2449 posts in 1715 days


#37 posted 747 days ago

lifesaver, you make some good points, and I have thought of this. You are correct on the first description of how this (old) design works. The new hinges have spring loaded buttons, so once you depress the button, you can change the angle, and then simply release the buttons to lock back in place. The doctor would have to reach down and hit both buttons simultaneously. Going through the motions, the old way of adjusting the backrest angle (pictured above) is a little easier. I think its a trade off though. The new hinges would allow more positions for the backrest and new possibilities of design….however it will be a few more/different steps in adjusting the angles.

I’m not sure how it’ll work out. I think I’m going to buy the plastic ones and just see if the concept is even worth pursuing. If it proves to be too much more work adjusting the backrest…then its probably not worth it!

-- Hey you dang woodchucks, quit chucking my wood!!!!

View Lifesaver2000's profile

Lifesaver2000

512 posts in 1736 days


#38 posted 747 days ago

Just keep in mind that some of the best ideas can end up in an entirely different place than where they start, so if you keep working at it you might come up with something even better than what you are thinking of now. Good luck and I hope you keep posting here so we can keep up with your progress.

Of course, when you get close to a final design you might want to keep it under wraps. If you can get this where you want it you might have a real money maker of an idea.

View MrRon's profile

MrRon

2786 posts in 1867 days


#39 posted 746 days ago

I think it’s time for someone to invent a new hinge. Hinges of the type you are looking for, are usually designed for a special application and not readily adaptable to other applications. I’m thinking of ladder joints, adjustable car seats, recliners, all designed from the bottom up.

View Lifesaver2000's profile

Lifesaver2000

512 posts in 1736 days


#40 posted 746 days ago

MrRon, I have one of those ladders that has four sections with three joints, that can be set up at several different angles or folded around completely for storage. When I first read this post I was thinking that a version of that hinge would be perfect for this application. There sure wouldn’t be any question of it supporting enough weight, since it will hold me up off the ground….

View dakremer's profile

dakremer

2449 posts in 1715 days


#41 posted 746 days ago

The problem with all of those hinges is that they are ugly. These hinges are so sleek/modern looking :).

There has been a lot of good discussion on here about this, and I really appreciate it. I think the only way to tell for sure if they’ll work or not is to just go ahead and try it. I’m going to order the plastic ones, just to see if the concept will work. If it won’t work, I’m sure I can find something to do with these hinges. I’ll keep you guys posted

-- Hey you dang woodchucks, quit chucking my wood!!!!

View Doss's profile

Doss

779 posts in 888 days


#42 posted 746 days ago

Again, those are ratcheting hinges that you all keep referring to. It is because of their design that they able to support a lot of weight since the faces of the ratcheting gear prevent motion in a particular direction.

dakremer, I have designed 3 different hinges today to deal with the mode of operation and loads you need (and more). Now, I just need to fab them up and test them.

-- "Well, at least we can still use it as firewood... maybe." - Doss

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dakremer

2449 posts in 1715 days


#43 posted 746 days ago

Are you inventing a new hinge for me?? That is awesome. I will be more than happy to test them for u on my prototype

-- Hey you dang woodchucks, quit chucking my wood!!!!

View junebug's profile

junebug

82 posts in 1028 days


#44 posted 746 days ago

technically, yes.. the 5:1 safety factor means the hinge is designed to fail at 5 times the listed figure.

Another problem I see with this particular hinge in this situation is locking them at the same angle. I feel the back of the chair could twist a bit when lowering the chair. Once locked in, the patient would be a little twisted. Probably not enough to be troublesome for the spines alignment, but it would make the chair feel unsafe possibly making the patient tense up.

View dakremer's profile

dakremer

2449 posts in 1715 days


#45 posted 746 days ago

That’s a good point Junebug. I never thought of that. That problem might occur no matter which hinge you choose

-- Hey you dang woodchucks, quit chucking my wood!!!!

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