Discussion
I think this is the correct thread for this question.
I'm seeking some nuts that are like this...
...but with the long end closed off, like a domed nut with a cylindrical end.
These are called shank nut/dragster lug nuts, which are (a) in the USA and (b) far too big. I'm after M8 or 5/16UNF, with closed end about one inch long.
Do such fittings exist and if so, what are they really called?
I'm seeking some nuts that are like this...
...but with the long end closed off, like a domed nut with a cylindrical end.
These are called shank nut/dragster lug nuts, which are (a) in the USA and (b) far too big. I'm after M8 or 5/16UNF, with closed end about one inch long.
Do such fittings exist and if so, what are they really called?
Dome or Acorn nuts. Not seen them that long, but there are 'long cap nuts' so I don't know whether they would suit?
Few more names here: http://en.wikipedia.org/wiki/Acorn_nut
Few more names here: http://en.wikipedia.org/wiki/Acorn_nut
Thank you, paintman,
That puts me on the right track. I found these...
...which are the kind of things I need.
The project is a wooden crossbow stock I'm working on. To make it accept a modern fibreglass 'prod' (the bow part), I'm designing an aluminium nose piece, to be fabricated from 4.88mm thick plate. This will, in effect, be a welded alloy channel, with a square aperture through which the prod will pass through to be clamped centrally.
The nuts are for a cocking device called a 'wippe'. It's tricky to describe but I'll have a go, using this very rough diagram.
Picture this made up in steel tube. The long cap nuts are at the ends of a stud that goes across the nose end of the stock. The part of the wippe with the handle at the top sits against the rearward face of the cap nuts.(Sorry cambiker 71, this is why the cap nuts have to be a smooth cylinder).
Then, the cutouts at the end of the H-shaped pivoted lever sit against the string. Pull the handle back and down in the direction of the arrow and the string is pushed backwards towards the tail end of the stock, which looks like a rifle butt. When pushed back far enough, the wippe pushes the string into the mechanism the trigger operates. The bow is then cocked, ready to shoot.
This is a mediaeval system. There are, however, pretty large forces involved. The 'prod' has a 175-pound rating, which is the amount of push needed on the string. I'm thinking an M8 stud size across the nosepiece will handle this. To fit the new fabricated channel section, I'm going to drill the stock (mahogany) crosswise and fit hardened threaded sleeves normally used for automotive rose joints. I'll Araldite these into place and use M6 countersunk stainless cap screws to clamp the nosepiece to the stock.
At the nose end, I could use plain-ended studs rather than nuts, to screw into M8 rose joint sleeves but It'll obviously be essential to be able to tighten everything up properly.
I hope this clarifies things
That puts me on the right track. I found these...
...which are the kind of things I need.
The project is a wooden crossbow stock I'm working on. To make it accept a modern fibreglass 'prod' (the bow part), I'm designing an aluminium nose piece, to be fabricated from 4.88mm thick plate. This will, in effect, be a welded alloy channel, with a square aperture through which the prod will pass through to be clamped centrally.
The nuts are for a cocking device called a 'wippe'. It's tricky to describe but I'll have a go, using this very rough diagram.
Picture this made up in steel tube. The long cap nuts are at the ends of a stud that goes across the nose end of the stock. The part of the wippe with the handle at the top sits against the rearward face of the cap nuts.(Sorry cambiker 71, this is why the cap nuts have to be a smooth cylinder).
Then, the cutouts at the end of the H-shaped pivoted lever sit against the string. Pull the handle back and down in the direction of the arrow and the string is pushed backwards towards the tail end of the stock, which looks like a rifle butt. When pushed back far enough, the wippe pushes the string into the mechanism the trigger operates. The bow is then cocked, ready to shoot.
This is a mediaeval system. There are, however, pretty large forces involved. The 'prod' has a 175-pound rating, which is the amount of push needed on the string. I'm thinking an M8 stud size across the nosepiece will handle this. To fit the new fabricated channel section, I'm going to drill the stock (mahogany) crosswise and fit hardened threaded sleeves normally used for automotive rose joints. I'll Araldite these into place and use M6 countersunk stainless cap screws to clamp the nosepiece to the stock.
At the nose end, I could use plain-ended studs rather than nuts, to screw into M8 rose joint sleeves but It'll obviously be essential to be able to tighten everything up properly.
I hope this clarifies things
http://www.crossbows.net/IFBOC-2nd.pdf Page 18 (bit slow to load)
Shows the wippe being used with a loop at the front of the bow.
Shows the wippe being used with a loop at the front of the bow.
Edited by paintman on Sunday 19th April 01:38
Yep, that's the very thing.
I decided on this rather than a goatsfoot cocking device because one would need a fulcrum peg near the pistol grip...too much strain on the wood for my liking. I can't use a stirrup and hand span (pull) the bow because I've an irreparable slipped disc. A windlass is overkill for 175lb, and very slow to operate.
I also can't incorporate a loop into the nose of the bow as the wippe's strong point. I'll be fitting a foresight on a steel bridge above the prod, to go with a peep sight (with adjustable iris) as the rearsight. The wippe will therefore have to clear the foresight.
Older Barnett crossbows could have a wippe as an option. These are like hen's teeth now...even self-cocking Barnetts (they 'break' like an air rifle) are fetching £450 or more second hand.
I believe I can work out the leverage/poundage for myself. If I over-engineer the mechanism, it will at least last longer!
I decided on this rather than a goatsfoot cocking device because one would need a fulcrum peg near the pistol grip...too much strain on the wood for my liking. I can't use a stirrup and hand span (pull) the bow because I've an irreparable slipped disc. A windlass is overkill for 175lb, and very slow to operate.
I also can't incorporate a loop into the nose of the bow as the wippe's strong point. I'll be fitting a foresight on a steel bridge above the prod, to go with a peep sight (with adjustable iris) as the rearsight. The wippe will therefore have to clear the foresight.
Older Barnett crossbows could have a wippe as an option. These are like hen's teeth now...even self-cocking Barnetts (they 'break' like an air rifle) are fetching £450 or more second hand.
I believe I can work out the leverage/poundage for myself. If I over-engineer the mechanism, it will at least last longer!
Thanks, Mick,
I reckon alloy would wear pretty quickly but steel or preferably s/s would probably work. I last used alloy rivnuts on a kit car yonks ago. They had threads for about a third of the length so I assume steel/stainless would be the same.
Sleeve rather than nuts beg a question...how do you tighten something smooth?
I reckon alloy would wear pretty quickly but steel or preferably s/s would probably work. I last used alloy rivnuts on a kit car yonks ago. They had threads for about a third of the length so I assume steel/stainless would be the same.
Sleeve rather than nuts beg a question...how do you tighten something smooth?
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