Double pin hinge
20 replies to this topic
Posted 14 May 2009 - 09:43 PM
This hinge is not revolutionary, but merely an extension of the ‘screw eye + pin’ method. For want of a better description I have called it the double pin hinge. The pins used (not shown) were 3mm dia brass tube, cut 3mm shorter than the depth of the section. The links were of 0.8mm (0.031”) soft SS wire. There are advantages and disadvantages with the construction.
1. space saving. The furthest into the segment that the hinge construction extends, is 8mm (0.3”). this allows more room for other hardware such as screw eyes and ballast. The space saving also allows the designer to construct smaller swimbaits for the same reasoning.
2. flexibility of lateral movement. With a regular ‘screw eye + pin’ arrangement, the rotation of the segments is fixed at the pin. The pin being in the forward or rear segment. To me, this gives a rather mechanical appearance, with the pivot not being in the centre of the joint. The ‘screw eye to screw eye’ gives a better visual result, as the pivot is in the joint centre, but the joint gap becomes a problem. The double pin hinge gives two points of rotation, which allows the segments to move where the water forces want them to move, in a less restricted manner.
3. paint and top coat. It is intended that the hinge is assembled as a final operation, allowing full access for painting and top coat.
4. repair and breakdown. As the pins can be made removable, then the entire hinge can be disassembled and renewed if deemed necessary, without disturbing the finish. On final assembly, I fixed the pins with a single drop of CA glue. This allows the pin to be tapped out with a drift of the same diameter.
1. up/down movement. Because two pivot points are employed then there is twice the play. This however did not seem to be visually a problem when testing, but is a valid consideration. On the first prototype, I used holes rather than slots (see exploded view). These gave more up/down movement than slots would allow. The next prototype (under construction) will use slots. More work, but should give a better result.
2. Construction. The construction work is slightly more involved, as slots have to be cut in both segments, also the manufacture of the link is fiddly, but after a few practice runs, is no big deal. It is best to make a simple jig with two pins a set distance apart, to control the pitch of the links.
Pull test. I carried out a pull test of 47Lbs for 48 hours. I loaded the tow eye and the rear belly eye. This transferred load through three segments and two sets of hinges. The tow eye survived intact, with only slight elongation of the eye, as would be expected. The rear belly eye took major distortion and damaged the 3rd segment as the bending load compressed the wood (Albesia density 0.45gm/cm³). The eye did not actually pull out, but the damage was such that the eye could be ‘rocked’ in its hole. Repair would be possible, but would affect the paint and finish.
All hinge pins survived undamaged, as did the links of the first joint. However, the extreme bending at the second hinge caused elongation of the lower link. But as the pins survived, this link could have been easily replaced without affecting the rest of the lure. I consider the pull test a success.
Swim test. When I eventually got the bait to swim, the movement was fluid and I was happy with it. The single link for the rear section was a problem, due to the excessive movement. I solved this by adding ballast, but in future I will be using double links only.
Comments good or bad welcome.
Posted 14 May 2009 - 10:54 PM
That is pretty solid. Nice work. Do you think it would be possible to use barrel swivels? I am not sure what the pull strength of those are.
Posted 14 May 2009 - 11:33 PM
Very nice and interesting , Dave , thanks for posting !
Did you use any kind of jig to bend the wire connectors ,..... since the distance between the single eyes of at least each pair of them requires to be exactly alike ?
If I need to bend repeatative wire forms , I'd use a jig roughly consisting of a wooden board with some nails in it(heads snipped off) to bend the wire around .
Seen a similar hinge before in a Swedish crankbait making book(German edition) , but it was a single joint(not a pair of connectors) , instead of a wire form the author described the use of a sheet metal stripe to connect the two sections .
Thanks again:yes: , ....greetz , Dieter
Posted 15 May 2009 - 02:40 AM
here is an other approach i used to use, i guess originaly from jrhopkins
the "pins" need to be "threaded" for a better bond. the edges (angel) must be sharp for a smooth movement of the sheet metal (otherwise it can get stuck). sheetmetal need holes or similar for better bond.
Edited by dramone, 15 May 2009 - 02:46 AM.
Posted 15 May 2009 - 03:16 AM
V-Man, very nice indeed and a good idea. I like the holes. They really makes for a clean and professional looking job. I think I may give this one a try. Thanks for posting.
Posted 15 May 2009 - 07:31 AM
Me too John, but I might come in from the side instead of vertical. Great work Dave, simple AND effective, I just wish I had that drawing programme you are using, AND those 'pro's and 'con's' are food for thought - any 'nit pickers' should take note here, all wheels used to be square.pete
Edited by hazmail, 15 May 2009 - 07:43 AM.
Posted 15 May 2009 - 12:17 PM
Thanks for the comments guys.
Atrophius, barrel swivels would work. Just design the pin hole positions to achieve the required hinge gap. Also, because the swivel pitch is not adjustable, you will need to get the pin holes accurate.
I was not accurate enough with this first attempt and had to insert another pin in the pin jig, to produce a slightly shorter link.
Pete, not sure how comming in from the side would work.
Here’s how I make the link:
Wrap wire around nail, held in vice. Short end held with long nose pliers, long end held by hand. Using pliers, wrap twice, tidy loops and cut with side cutters (pic link 01).
Locate loop on pin jig (pic link 02), wrap around second pin just ¾ turn. This fixes the loop position.
Return to nail in vice. Locate second loop on nail. Insert brass rod tool in first loop. This tool allows you to apply tension to the link while wrapping the second loop, by hand. Tidy loops and trim with side cutters. Crimp tags with long nose pliers (pic link 03).
Place link on a scrap piece of wood. Locate centre punch in loop, hit with hammer a few times. This rounds the loop and flattens any kinks/bends/blemishes and generally tidies the result (pic link 02).
Hope this is clear enough. I am sure there are other ways of doing this, but this works quite well. even just after a half a dozen links, the production becomes quite efficient.
Posted 15 May 2009 - 04:34 PM
Only one thing to pick about is a swimbait needs the front section to move the back section, double hinging somehow defeats this purpose as there is a "slip" of energy transfer in the movement of the front hinge before the energy transfer occurs. Food for thought?
Posted 15 May 2009 - 08:44 PM
LP, interesting thought. My thought is that the water forces move the individual segments, rather than the segments just following the one in front, but I am not going to bet more than a ringgit or two.
Innitially, only the 4th segment was moving, but after some temporary re-modelling of the front section with some low density plasticine, which actually floats, I was able to get it to swim as desired.
Your idea can be tested out by locking one end of the link, thus converting it into a single pin hinge. But first I will have to repair the MK1 after the damage of the pull test. I will get back with the results, not sure when.
Posted 16 May 2009 - 02:53 PM
Here is a video of the double pin hinge in action: doublehingepin04.flv video by folicallychalled - Photobucket
Posted 16 May 2009 - 04:08 PM
Check this out: STRIKE PRO - Casting into the future
Posted 16 May 2009 - 06:00 PM
Very nice Dave, swims in the tub great, so should be good on the lake.
LaPala, they must be using watch or clock chain!!!!, I have seen these, similar to bike chain, but when I think about it, so is this link of Daves.pete
Posted 17 May 2009 - 01:11 PM
Dave, Well done! That is a smooth and beautifully fluid swim. Congratulations.
Posted 18 May 2009 - 10:03 PM
I dismantled a bicycle chain link to examine more possibilities. The pitch of the holes is exactly 1/2" and the hole diameter is 3.5mm (0.138"). The 3mm dia tube is a little sloppy, but no more than the twisted wire. Would be much tighter on a 1/8" dia tube. But, like the swivel idea, drilling accuracy would be very important.
The links have a rust proof coating, so should fare well in the water. They weigh in at 0.9 grams per plate and strength is beyond doubt. I see no conflict with any patents likely to have been issued regarding chain links, as this idea only uses the plate. I have not researched patents though.
Just another one for the hinge library.
Posted 18 May 2009 - 10:27 PM
That lure swims beautifully. Excellent job on the hinges. And nice music for the video.
If you don't mind, one thought. That's all I have left at this hour.
I find the repetitive back and forth of the wire against the pin is what wears out the pins, though, not the trashing of the fish after it's eaten the bait.
If I were you, I might think about using Captsully's bicycle spoke pins instead of hollow tubing. The brass will eventually wear, because it's softer than the sst wire, and it could collapse or deform under load. Once it's damaged in the joint, it looks like it would be a bear to change out.
But the bike spokes are solid, so they might be heavier and affect the ballast weighting.
I know, when I changed to spoke hinge pins, and the larger .092 screw eyes to accomodate the larger guage wire, it affected how I ballasted my swim baits.
Posted 19 May 2009 - 07:17 AM
Mark I used the brass tubing in a bait. It seems to work great, the advantage to the tube is if it needs to be changed, a slightly larger diam drill bit drilled inside of the tube will remove it clean as a whistle. a compromise might be a stainless tube, but I don't think the brass will wear out to fast, but I will try it and see.
Posted 19 May 2009 - 07:46 AM
Mark, a valid point. Question is, what is a reasonable life expectancy of a lure, in hours. 500hrs, 1000hrs, 5000hrs?
Next time I visit the electronics mall, I will pick up a solenoid and see if I can rig up some sort of life testing rig. I have been thinking about such a rig for a long time. Seven strand wire also needs testing.
Posted 19 May 2009 - 08:09 AM
"I have been thinking about such a rig for a long time. Seven strand wire also needs testing."
Dave, so have I, use a fish tank aerator (240V @ a second hand shoppe) - if you pull it apart it has an electro magnet and an oscillating arm which operates the pump mechanism, slow it down with a dimmer. Save some time, a solenoid would be too slow. pete
Edited by hazmail, 19 May 2009 - 08:11 AM.
Posted 19 May 2009 - 08:44 AM
The reason I suggested the bicycle spokes is that it's solid sst wire, and of a decent thickness. It is easy to remove for maintenance, just by pushing it with a small punch until you can get some needle nose pliers on it, and then pulling it out.
But, Dave's right. If the wall is thick enough in the brass tubing it should last a looooong time.