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Forum topic by dakremer posted 08-02-2012 12:13 PM 2816 views 0 times favorited 45 replies Add to Favorites Watch
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dakremer

2453 posts in 1742 days


08-02-2012 12:13 PM

I have a new prototype I’m working on and want to incorporate these hinges into my design. I’ve looked high and low and these are the only hinges I’ve found that are adjustable locking hinges…..

Here is what the website has to say about them….

Economical-yet-rugged locking hinge made of tough black thermoplastic. Adjustable Locking Hinge Models provide positive locking at any 10° or 45° increment. Once locked, the hinge becomes an absolutely rigid joint, able to withstand 450 inch-lbs of torque (5:1 safety factor). Applications include adjustable fixtures, rotating fixtures, trunnion mounting, adjustable handles, foldable handles, adjustable part trays, adjustable shelves, adjustable racks, adjustable and/or fold-away work surfaces, positive positioning of lighting or nozzles, and collapsible structures. Patent numbers 5,586,363 and 5,689,999. Other patents pending. Made in USA.

MODELS AVAILABLE:
Available only as an inline model with either 10° or 45° increments. Hinge extensions line up in the same plane. Total range of movement is 220°. See Dimensions page for part numbers.

MOUNTING:
The version shown here has square hinge extensions to fit 1-1/2” OD square tubing externally, or 3/4” square tubing or bar stock internally.

SAFETY PRECAUTIONS:
Avoid any possible pinch points, especially with heavy loads. Do not release the hinge unless adequate support for the load is in place. Do not let loads swing freely.

MATERIAL & WEIGHT:
Body – Black thermoplastic
Pins – Dupont Zytel
Release Button – Black thermoplastic
Weight – 5.8 oz.

So what i need translated in to english is…...What does 450 inch-pounds of torque mean? I’d like to know how many pounds of force this thing can take at about 10” away from the hinge….2 hinges will be used, so will this double the amount of weight it can withstand??

Here is the website. I think these hinges are awesome. i’ve never seen anything like it. could be a useful piece of hardware in the shop. They make a metal version as well that is quite a bit stronger, but also quite a bit more expensive ($100ish each). This plastic version is about $19 each.

Does anyone know of a different source for a locking hinge like this or seen anything like this before? I think this is an amazing idea, with a ton of possibilities!

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


45 replies so far

View junebug's profile

junebug

82 posts in 1055 days


#1 posted 08-02-2012 01:02 PM

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

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dakremer

2453 posts in 1742 days


#2 posted 08-02-2012 01:08 PM

Thanks Junebug!

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

View Milo's profile

Milo

851 posts in 1970 days


#3 posted 08-02-2012 01:12 PM

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...

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dakremer

2453 posts in 1742 days


#4 posted 08-02-2012 01:31 PM

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 1344 days


#5 posted 08-02-2012 01:37 PM

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

2453 posts in 1742 days


#6 posted 08-02-2012 01:42 PM

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!!!!

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Bertha

12951 posts in 1344 days


#7 posted 08-02-2012 01:50 PM

^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 1620 days


#8 posted 08-02-2012 01:53 PM

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.

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dakremer

2453 posts in 1742 days


#9 posted 08-02-2012 01:58 PM

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

5624 posts in 2079 days


#10 posted 08-02-2012 02:01 PM

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

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dakremer

2453 posts in 1742 days


#11 posted 08-02-2012 02:06 PM

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 915 days


#12 posted 08-02-2012 05:15 PM

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

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dakremer

2453 posts in 1742 days


#13 posted 08-02-2012 05:47 PM

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

248 posts in 1733 days


#14 posted 08-02-2012 06:42 PM

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 915 days


#15 posted 08-02-2012 06:58 PM

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

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