11

I'd recommend searching for shaft couplings. These are a great option for connecting two rotating shafts in a non-permanent fashion. A set screw (as mentioned) can work in low load cases, but is often best with a flat spot cut into the shaft so that you've got more than just friction between the screw end and shaft to constrain things. The setscrew may also ...


10

As already mentioned in many contexts you will make one part essentially consumable in order to reduce wear on an expensive or difficult-to-replace part. Similarly if you have a situation like a shaft mounted in a cast iron casing (eg an engine block) it makes sense to protect both, relatively complex and expensive parts with a cheap, expendable and easily ...


10

A method which works extremely well and which does not require set screws and/or flats on the shaft and which can be added or removed easily and rapidly is a collet based connector. While any one of these will only work for a limited range of shaft sizes, units are available off the shelf for a wide range of shaft diameters and you can make or modify them ...


7

While it is an interesting idea, I don't think a "static treadmill" is going to give you results similar to walking. A PFTE(teflon) surface would be really low friction, but I think there are some bigger issues you may need to address first. Walking is essentially a repeated process of balancing, tipping, and re-balancing. The algorithms your brain uses to ...


7

Typically jewel bearings (as you've described) are not used in large scale industrial equipment. The main reason jewel bearings are used is their inherent hardness. The bearing material has very little wear over the life of the bearing. Most of the wear occurs to the shaft riding in the bearing. In industry, you typically want to avoid wearing the shafting ...


7

You need to separate the braking from the winding / unwinding. Have a look at a ship's capstan. You want a miniature version with very high friction between it and your rope so there is no sliding and no heating. You then control payout using a brake mechanism on the capstan. Figure 1. A cable-pulling winch. Image source: Egerton.


6

There are two methods that immediately come to mind. Attach it with a set-screw. Use a weak adhesive. This would be strong enough to hold the items in place while in service, but weak enough that it could be twisted apart without damaging the individual parts.


6

You need to control how fast you apply the power. Some sort of damper mechanism that would allow power to be gradually applied and not cause it to spin out. You could try and wrap the 'power string' over different sized pulleys so that you changed the gear ratio. If you used a cone it would be similar to a CVT where starting out you would have a low gear ...


6

In addition to ashgetstazered's answer, some materials (Aluminum, I'm looking at you!) will gall badly when meshed against themselves, while moving reasonably smoothly against a different material (e.g. bronze bushing). So if you have a good reason to produce one part out of a given material, you then choose the mating part's material to minimize galling or ...


6

No it doesn't, and it isn't meant for that either. A standard flat washer, that is. It's meant to give the nuts and bolts a better support, and it protects the material against the nut which may otherwise scratch it upon tightening. A washer may even reduce the friction on the nut, since the fastened material may in many cases have a higher friction against ...


6

Your initial assumption is a bit flawed. You can not just draw the conclusion that all friction is the same. It is like saying all birds i know of can fly thus all birds can fly. Which is obviously untrue. Moreover, continuing this similie, you also imply that there is only one kind of flight. In reality friction is a highly complicated phenomena that ...


5

Friction is probably one of the primary reasons; as friction also correlates to wear. Friction is much more complicated than the equation we learned back in physics. Published friction coefficients are very much ball park figures because the friction greatly depends on the micro surface texture. This causes of friction link does a good job explaining some of ...


5

You can't calculate friction coefficients this way. At the atomic-scale level, the friction coefficient depends on the interactions of the two materials across the interface. If you measure the behaviour of the interface between materials A and B, and A and C, you can't say anything about the interface between B and C. In any case, friction coefficients are ...


5

There are two types of losses in magnetic bearings, windage and electromagnetic losses. Windage or aerodynamic loss is the dissipation of rotational energy due to the viscosity of air or other gases trapped between the rotating and stationary portions of the system. These effects are more significant in high speed applications and clearly non-existent in a ...


5

There are two things going on. First, even if this "actuator" can produce constant torque, the torque required to keep the load spinning will be at least in part a function of the spinning speed. There will be some friction and other forces that increase with increased speed. Viscous friction increases linearly with speed, and other effects, like air ...


5

If that is true, then would not be better off just to remove the whole setup and have the axis of rotation free from bearings ... Ball bearings change a system from sliding friction (as in a journal bearing) to rolling friction which is usually considerably less. Ball bearings prevent wear in one place as would occur with a horizontal rotating axis at the ...


5

In laminar flow, you assume a fuild layer near the pipe wall with flow velocity = 0, and progressivly faster flowing layers towards the middle of the pipe. That's why it's called laminar. Because there is no flow near the pipe wall, the roughness does not affect pressure loss. In most practical applications, you will be outside of this flow regime. Then the ...


4

The bearings themselves may have ideally 0 friction, but there will still be some losses of rotational energy in the system as a whole. Even if the vacuum was perfect, anything that conducts electricity even a little becomes a transformer secondary in the presence of changing magnetic fields. Conducting material in the rotating thing will dissipate power ...


4

Friction is not a property of a material, it is a property of the interface between two objects, which may be the same or different materials. One interface I can think of that has that property is a thin layer of grease -- the force required to move increases with velocity.


4

I haven't heard this bit of advice and as with most things in engineering it really comes down to WHICH materials and in what CONTEXT. I can think of one main reason why you might want to make them out of different materials: Differing hardness. What this means is that only one of the materials should 'wear' and then you could design it so that this part ...


4

The simplest way by far is to select a prospective bolt, calculate the clamping force this creates when it is torqued to rated torque, and use the bolt circle as an approximation of the moment arm. Compare this against the rated torque spec and duty type for the gearbox. Grade 5 bolts are ordinarily adequate for industrial uses. Some fussier machines or ...


4

The problem you have is more complicated than you think. Any industry that deals with the storage and movement of granulated/powdered materials has to deal with this and most have unique solutions. You need to look at the principles of hopper design. Some of the things that affect any design will be: The angle of repose of the material you intend to use. ...


4

... then how is it stopping the vehicle's car, that is bringing it instantly to rest. It's probably an error in your writing but brakes don't bring a vehicle instantly to rest. They decelerate the vehicle in a more-or-less controlled manner over a period of time or distance. I mean how are the components/vector components of the forces applied by brake ...


4

Brakes primarily convert kinetic energy to heat energy. So a large area can absorb more heat lowering the peak temperatures ;of course this is strongly affected by the thickness/mass of the discs and other factors. AND the larger area can get rid or more heat . High temperatures cause deterioration of pad materials ,so lower ( not as high) temperatures ...


4

I've loaded a winch with Spectra line, not quite as abrasive as Kevlar, but similar in strength and size. The key factor in such problems is to load the spool while the line is under tension. I used a heavy wheeled tractor as the load. As the winch turned the spool, the tractor was pulled across an even surface with brakes applied as required. The amount of ...


4

Assuming the same material and tolerance, I pick the right-hand detail. Due to having a larger resistance arm against shimmying and lateral shock when the wheel falls into an unsymmetrical pot-hole or passes over random construction debris like broken cinderblocks, pieces of metal, pebbles, etc. remember direct loading stresses are secondary to lateral ...


3

If you have to select a material for this application, I would use ultra high molecular weight polyethylene (UHMW). It has a very low coefficient of friction, very high wear resistance, and is a lot cheaper than Teflon.


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