Chiff and Fipple Forums

Now, once we have found the total force (100lbs in the case of your slab examples, 90Kg in the case of my wrap example), you don't then divide it by the number of elements (10 slabs, or 150 threads). To work out pressure, you take the total force over the total area. The force is coming from tensio...

As much as you might like to think of 150 people standing on my back try this instead A square shaped weight that's 10lb and is 10in x 10in (100sq in) Stack an identical square weight on it Pressure = Force/Area 10lb / 100sq in 0.1psi Sure there's a 10lb weight but spread out over 100 square inches ...

Is it your argument that, because a single piece of thread is involved here, the tension in the thread only acts once on the tenon, and the force is not multiplied by the number of turns? You're making it more confusing than it needs to be. You could consider each loop as "acting" on a te...

It's really a pressure versus force question. If a single thread loop exerts say 600g force on the wood below, then 150 such loops side-by-side will exert 150 times 600g, or 90Kg of total force on the tenon. That's most definitely wrong! Pressure = Force/Area -Not- Pressure = Force*Thread Count/Are...

That's..... what..... we're.... trying.... ta..... figure...... out. Just a friendly reminder, there aren't any length requirements for posts, no need to double space =) If Casey goes so far as to void warranties on his flutes for corking his tenons, that must be because they cause damage to his so...

Whoops, sorry George, I seem to have missed that bit. Can you direct me to where you caught my error? Or, run me through it again? Secondly, as I understand these things, what matters is not the total pressure along the entire length of the tenon, but the maximum pressure at any given point. So, yo...

Fair enough, though what's right for your flutes won't necessarily be right for others. I have in front of me a Burns flute section. The tenons are massive, way more substantial than the tenons on any other flute I have in my possession. I think it's fair to say, Casey, that you've chosen a fairly ...

George, I did not advocate stopping using numbers, just meaningless and unhelpful speculative ones. Lets save the number-crunching until we have real, observed and measured figures.. By doing some basic "number-crunching" you can see that the people taking the position of extreme pressure...

It seems obvious now that 2,000 loops of string wrapped directly one on top of another could make literally a ton of force underneath. But spread out over a tenon is much more modest, as in under 20lb.

So of course now let us completely ignore the numbers ...

Rob Sharer wrote:When you say "tube clamp", do you mean one of these?

I wasn't intending it to be a specific model, so no. It's a 'pretend' one that -

1. Covers the same surface area
2. Evenly distributes the same force ~17lb around the tenon

Review the turn count ? But would 200 turns change the astonishment factor significantly ? I was combining Highwood's example and Terry's ... Highwood used nice round numbers like 2,000 for the wrap. Rob I appreciate the skepticism but just wish it would come hand in hand with an explanation instea...

Now if there are about 2000 wraps (150 x 13 = 1950 but who's counting) that is 12000 N of force applied inwards which converts to over 2500 lbs or well over 1 ton. The resulting pressure would be easy to figure out and is left as an exercise for the reader... Okay, I'm just trying to get a hold on ...

The force is per wrap... According to Terry a ball park number is about 2000 wraps... Okay, so you're saying it's each individual loop that needs to be added together? So then after the first layer of 150 loops it's 6*Tension*150 as the force being applied? 100g*6=600 600*150 = 90,000g (198lb) 90,0...

The force is 6 x the tension exerted by one whole wrap - so the pressure is that force divided by the contact area of that length of thread (one wrap). If there multiple layers the forces will add - multiple windings (not layered) the pressure remains constant. Okay please correct me where I'm goin...

So, after at least three independent confirmations by experts that the total amount of pressure exerted by thread as applied to a tenon is not limited to 1 x the breaking strength of the thread , can we all agree that adding more thread at tension multiplies the total tension applied to the tenon? ...