JBlaze

Hinge Stress Test

9 posts in this topic

I have already posted these first few pics in another thread but for those who have not seen them I am including them in this thread so you will understand what I trying to achieve.

I thought I had an original idea in this hinge but it has been posted before by Diemai. Not sure how strong it will be but I am putting one in a junk balsa lure and will hang it from a scale with some weight to see when and if it distorts or fails and at what weight the hinge or the twist pins will pull out of the balsa wood. The hinge is made from 105 lb. Test .031 spring temper Stainless Steel.wire . I think that any line that I use would snap before this hinge would fail. But I am curious to see what happens as I add weight to this thing. The twisted tow eye and rear hook hanger are also made of this same wire and are imbedded in the balsa 1¼ inch they are glued in with thin CA. I am expecting one of these hangers to fail before the hinge does. I think this hinge if successful will lend itself to easy installation in split baits or a one piece bait. I drilled the holes for the hinges slightly deeper than the hinge arms are long. I hardened the insides of the holes by injecting them with thin CA. After it dried, I redrilled the holes and filled them with D2T epoxy. I then inserted the hinge arms in the holes about ½ way and slid the two PVC hinge spacers over the arms and pushed the hinge arms the rest of the way in. Remove the spacers and let cure. I have always planned to stress test tow eyes and hook hangers but have never done it yet. So, I guess I will kill two birds with one stone. You can see by the pics how this hinge is made and installed.

Thursday afternoon 2/19/2009 at 3:30 pm I started the weight/stress test today. I added weight until I reached 20½ lbs. and the bucket was full. I will let this hang for 16 hrs until I got off work Friday morning.

Friday Morning 2/20/2009 at 10:30 am The hinge is still not deforming and I see no sign of the twist pins or hinge pins pulling out. I am going to leave it a few days to see what happens

Tuesday Afternoon 2/24/2009 at 3:30pm It has been 5 days now since I have checked on the hinge. Iwent out to the man cave to see how the hinge was holding up under the 20½lb load. I didn’t see any signs of deforming or anything coming apart so I got a larger bucket and put the bucket of wheel weights in it and reattached it to the lure and set a bucket of bolts in it also. This pulled the scales down to almost 30 lbs. I still didn’t see any signs of stress so I started adding more wheel weights The scales passed 0 a third time and locked at 34lbs. They are designed to weigh 30lbs max. Next, I got the bathroom scales and started adding more wheel weights a few at a time. I finally started seeing the gap between the first section of the lure and the hinge coil widen. I stopped adding weights and weighed the bucket of weights. It weighed in @ 45lbs. I hung it back up and added more wheel weights until the hinge started pulling out again this time it slid out rather quickly about an inch and stopped again. I stopped and weighed the bucket. It weighed in @ 54lbs I picked it up by the hanger and gave it a couple of hard bounces and the lure finally finished pulling apart.

As you can see in the last picture, The coil had tightened up on its end wraps (I believe that a larger hinge pin would have not permitted this to happen, the hinge pin that I used .031 was only ½ the diameter of the hole in the coil .062). Also the hooks in the hinge arms had straightened out. I think that hardening the inside of the hinge arm bores with the CA gave those hooks a little more grip on the wood. (maybe someone else would have some insight on this.) Another thing, the upper rear hinge pin arm had started to pull out also. I think both of these things happened when I gave it the hard bounces to get the hinge arms to finish pulling out. Also, you can see that neither the twisted wire tow eye pin nor the rear hook hanger have budged.

This lure was cut from a junk piece of soft balsa wood it has not been hardened with the wood hardner and does not have any epoxy top coat on it. I think a top coat and a dip in the wood hardner would have strengthened the assembly even a little more.

I have always worried that a twisted tow eye or a hook hanger might pull out of one of my lures with a big fish on. I don’t catch that many big ones but always expect the next strike to be the fish of a lifetime.

After performing this stress test, I feel that I have nothing to worry about from my balsa lures that have not been thru wired. I think that any fishing line that I use would break long before I would have lure failure. The exception to this would be slapping the lure on the water to clear it of moss or weeds. After having two lures explode from this procedure, and some good advice from JawJacker. I don’t do that anymore.

Pete, looking at the results of this coil and pin hinge test, there is no telling how much weight you could put on your DNA hinge before it would fail. If you could somehow secure it to keep it from pulling out of the lure, I bet it would easily support 100 lbs or more.

Hopefully, this was not confusing but if it was, let me know and I will try to explain.

I also hope this test helps someone to feel a little better about using homemade twist pins and hinges when building or assembling their lures. John

Hinge stress test pictures by JBlaze1952 - Photobucket

Edited by JBlaze

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JB, excellent work and a good result. The thin CA makes all the difference.

I did a very similar experiment to test twisted eyes (plain twist and loose barrel twist). I sealed the inside of the holes with polyester resin, but its viscous properties does not allow it to soak in sufficiently.

The wood I used was slightly heavier than balsa, at 0.3gm/cm3. I found the loose barrel much stronger than the plain twist, holding 47Lbs for weeks.

I tried the same test with light balsa, but it pulled out very early, at about 15Lbs. This is why I say that the thin CA makes the difference.

I am hoping for similar results to yours, when I seal with propionate with vacuum assist.

Once again, great post, thanks for sharing.

Dave

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@ JBlaze

John , you really have taken an effort to share the results of your experiments with us , thank you so much:yes: !

You have explained your pull test thoroughly , easy to follow and to understand .

I agree with you , that the outer coil windings would not have deformed as fast , if the hinge pin would have been larger in diameter .

I am also quite surprised , that the wire ends had straightened out , I rather would have expected the wood grain of the balsa to crack up and release the glue plug around the wire !

Thanks to having reinforced the wood previously:yes: !

I also agree , that the final result of your test is evident , that none of your target species would pull your lure apart , since under fishing conditions you still have the flex of the arching rod and(mono)line to feather down the pull force of a fighting fish , a bad snag to pull free could be worse , probably :?.

To add strength to this type of hinge one might secure the "U"-bent wire ends epoxied into the wood body by crosswise wire pins , leading through the wood and engaging right into the deepest points of the "U"-bents .

Should be assembled in a dry fit at first and later all set in during one process with the still wet glue !

Thanks again for sharing :yes:, greetz:yay: , Dieter

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John, great work and great result - I had just sent an email to 'Jamie' saying I would have to do a test on the hinges and see what happens, then I came across your post. You have excelled, and saved me a heap of time. As Daemai said, it would be a big fish that would put 54lb on a line attached to a good rod. Thanks again, and excellent work.pete

Edited by hazmail

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Thanks guys. I still don't have any idea how much weight the twist pins (hook hanger and tow eye), will support before pulling out I think I will try to rig something that will grip the two halves of the lure to see how much weight those will hold before pulling out. I was suprised that the lure held that much weight before coming apart. But the CA does make balsa really tough and hard. It sounds like you are drilling in concrete after the wood dries out. I sealed a couple of balsa cranks with it a few months ago and the fumes just about made my head explode. The lure had a real sharp ping sound to it when I dropped it on the concrete.

By the way pete, those are nice looking lures you showed in the "whats on your work bench" thread. Can't wait till you post them in the gallery. Looks like you are doing a really nice job. The paint job is very sharp too. I like your spacers or hinge protectors or whatever you call them. Excellent idea. Are they made of foam? John

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John,

What is this "CA" you guys are talking about. I haven't used balsa up to now but I do have a couple ideas that require balsa. I searched for CA in this forum and came up empty. You guys are talking about it as if it was as obvious as the air we're breathing so I'm a bit embarrassed to ask.:o But I won't learn if I don't ask.

Dave

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Hi Dave, don,t be embarrassed, I asked the same question a while ago when I was getting my feet wet, It is basically, super glue or cayraclinite (I know I spelled that wrong) You can get several different thicknesses at the hobby store. The thin CA really penetrates the balsa wood and makes it much stronger. It adds very little weight to the lure. Be careful when using it , more than once while installing a twisted wire hook hanger or tow eye, I have had it penetrate from the center of the lure to the outside of the lure gluing my fingers to the wood. :eek:

John

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John I copied yours, they are made from PVC pipe, which when I checked my junk bin, found are in various thicknesses, from 1mm to 3mm, so 2 - 3mm was just about right. As for the lures, I am having varying results, from great to so so with the action - this is a lot to do with my inexperience with weighting these. Playing with tails now, as these seem to have a positive effect.pete

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Hey Pete, I am glad that you thought the pvc was a good idea. What I can see of your joints, looks very clean and professional.

Even though you are having mixed results, I think your swim baits are going to be very special once you figure it out. You are much farther along with yours swimbaits than I am with mine. I have two that are almost ready for a swim test both are floaters/wake baits and one that I want to be a slow sinker or suspending version. That is a tough one and I think weight placment is going to be a hard one to solve to get the right action especially on these smaller lures. My new grandson takes up most of my spare time now. He is seven months old and I wouldn't trade this experience for anything. I will eventually get there with the lures.

John

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