Looking for some 6mm diameter steel shafting. Primary requirement is stiffness. Is stainless better than silver steel?
Also looking for metal tube with a no slop sliding fit over it..found
1/4" OD brass thin wall....anyone know if that is gonna fly?In message , The Natural Philosopher writes
I buy 86 [1] 13" [2] lengths at a time of silver steel, it's also sold in just over 3' lengths. You don't normally buy it in other lengths
what length are you after ?
[1] don't ask why, no idea, nor do the supplier [2] - so you can cut 1/2" off each end to get 12" without the risk of distortion
Stiffness, not a lot of difference. If you want to run it in a bearing with minimal work, silver steel is very accurate. Whether brass thin wall tubing is suitable depends on the speed, load, duty, lubrication....
Silver steel can be hardened and tempered to suit your application. Stainless steel is likely to work harden and become brittle. There some knowledgeable metallurgists over on British Blades who might help.
minimum about 9", but can cut to size. I have found it all right, in suitable sizes.. also stainless. Just wondered which was stiffer. Needs to take a large bending load without plastic deformation. I'd rather it snapped..
Its actually wing attachment cantilevers for largish model gliders. Slide on, locate laterally, and go fly..but without the wings bouncing up and down..tried 4mm piano wire..no good.
I can send you a "foot" to play with if you want
Oh..no need. we will be getting a fair bit in..several models have lost their wing joiners, and a new one needs some more. andd that's going into production shortly.. It was just a case of which to buy really..
But thank you for the offer anyway, that is appreciated.
This is where I get mine from
Yes and no, depending upon the grade of stainless steel, but there won't be a lot in it.
Not without knowing what the wall thickness actually is. Generally, I would drill and ream something if I wanted it to be a specific fit. Silver steel would be an advantage here as it is dimensionally more reliable than bar stock.
Colin Bignell
So can a martinsitic stainless steel, such as 416.
There is a huge number of different grades, with many different properties.
Colin Bignell
Carbon fibre, Kite spar's easy to get and cheap enough in that size.
LOL. Don't you realise that every type of steel, hardened or otherwise has exactly the same Young's modulus i.e. exactly the same deflection per unit force applied? All that changes with constituents and heat treatment is the tensile strength and hardness but the stiffness stays exactly the same.
I doubt it.
There are two different concepts getting a bit mixed up. As Dave Baker says elsewhere, all steels have more or less the same elastic modulus, or stiffness. What does vary is the load at which they fail, and the mode of failure. So a "high tensile" steel will yield, i.e. deform permanently, at a higher load than mild steel, and a brittle material will fail such that the bits more or less fit together afterwards, whereas a ductile material will stretch first. Heat treatment of many materials affects these properties, but not stiffness. All a gross simplification, but hey, it was free.
Could you make it as a hollow tube, rather than out of solid? For a given weight, potentially much stiffer and stronger. Without being able to do the sums, I'd also guess that a really good fit between the two pieces is very important, not just to avoid things flapping around, which seems OK for birds but perhaps not models, but because a loose fit may lead to some locally high stresses at the end of the tube.
I think I'd be looking at composites (pultruded grp is good stuff) or aluminium tubes in tubes.
Not strong enough and too flexible.
While that's broadly true on the range of workshop alloy steels, doesn't stainless typically drop about 10%?
I presume there are also some varieties of unobtainium that go the other way too...
If you want the stuff to break on impact use wooden dowels. How big are these wings and what are they made from? Steel rod sounds far too strong for the job.
Wiki seems to suggests that high carbon steel has 10% gtreater young's modulus than stainless. And twice as much as cast iron.
However, I take your point that the variation is not great over the range of alloys in question.
Well you obvously dont know..
Right. I hadn't appreciated that the stiffness was almost independent of composition. I knew the other properties varied enormously.
That's inevitable anyway. Weight is not too serious oddly enough, as a typical sailplane needs a bit of ballast to cope with wind..increases flying speed without having to dive.
Well people can and do use those, but there is a drawback, and that's wear as they get plugged and unplugged, and under flexure. Eventually you have a lot of slop and black dust. If C/F is used. GRP its white dust :-)
Aluminium is simply too easy to take beyond the plastic limit. And tube is easy to BUCKLE. Where the tube is not sheathed inside the structure, is where the greatest compression occurs. Dead easy to get the top of the tube buckle inwards. Solid rod doesn't do that..
Basically the stresses at the wing root, where forces are so high you can more or less ignore the fact that the wing is clamped to the fuselage, are pure cantilever bending. We tried 4mm wire but under even mild manoeuvres the wing flex was pretty high. Given that the shafts extend several inches into fairly close fitting tubes, this had to be pure flex in the steel rods at the place where the tubes stop. Ultimately what is needed is great stiffness at normal loadings, and enough strength so that even under extreme G - pullout from a dive in emergencies, if the wings flex, they don't permanently bend the rods either. The ultimate breaking strain then becomes the spars more or less where the rods end, which I have stressed to about 10G. That's enough for this model. Some high performance gliders are stressed to around
100G, which is enough to cope with pullout from dive speeds up to about 200mph or more. World record is somewhere around 300mph, but this model isn't intended for that sort of performance, or anything like it.Anyway, I now feel confident that either will do as well. I suspect silver steel has the slightly greater ultimate strength, so will go for that. It's also more available.
There is no point in making the rod stronger than the wing itself though. That's a classic tapered I beam of hardwood with balsa webbing and a stressed skin over the lot where the stresses are highest.
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What do you mean by "strong" (with numbers), is this for axial bending or torsion, and likewise do you need stiffness to be axial bend or torsional? Also do you care about stiffness / volume, or stiffness / mass, because CF will beat steel easily by mass. If you're mass limited rather than diameter then you could go to 10mm pultruded tube that's enormously strong and still cheap, until you go to the woven tubes.
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