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I am looking at designing a straight spline for the end of a torsion bar. The equation states that the torque capacity is based on the limit of 1000 psi bearing stress. Is the bearing stress mentioned the stress that is placed on the internal spline? The spline on the torsion bar and the...

Thanks dhengr, I think I understand what your getting at now, but just to make sure lets see I can describe it back to you. To start the outer tube will be .5" higher therefore giving us the .25" in clearance between the bar and tube. There will be two .25"x.25" bar inserted in between the bar...

Ok so we are simplifying things. Im having a little bit of trouble figuring out how to model the elastic line equation. My inclination is to model the edge contacts as a simple support such as a roller, however that would imply that the deflection at the edge contact points should be zero...

As suggested by Hydtools if the bar fits close enough into the square tube that the screws are only used to hold the bar in place, as suggested there would only be two point of contact, but if the bar were fitted into the tube would not more of the bar would in contact with the tube than just...

Thanks for the help everyone, yes the load will be distributed sorry about the small mistake on wording... Yes shearing of the bolts will be something to consider but that was going to be taken into consideration after I figured out the forces acting at the bolts (need the force to determine...

I am trying to figure out how to mount a bar that will dissipate the forces from a torque. The bar will be slipped into a hollow square beam that is located 6" from the point where the torque is applied and it extends 8". There will be 3 bolts placed along the hollow square beam at 2", 4" and...

Would a spring that requires 1630 in*lb still be a very large torque for a 3" outer diameter?

Yes disengaging the torsion bar when its under that amount torque does sound like a bad idea. You are right with the description. The reason why it becomes tricky is because you need something to absorb the potential released as the lid descends in both directions, both opening and closing...

From doing the analysis it has become more obvious why a lot of the flippac torsion bars actually break... Do you think there would be a way to disengage the torsion bar after a certain point (say 80 degree angle of twist) and possibly catch the lid with some other type of system such as a...

Sorry for the mistake on the last post the .375 is the out radius and the .3092 is the inner radius. should give you closer to the 104.5 ksi that I calculated before, however I'm still unsure about if this value will cause creep in the torsion bar it all depends on the shear yielding.

Yes the spring is only a part of the project and of coarse it would be best to have an expert design the spring however several other designs are being taken into consideration perhaps after a full on discussion about the direction we cant to go an expert can be hired if we decide a torsion...

Alright rb1957 starting to get some better results with your suggestion. What I have been doing is specifying my outside diameter of the rod. For the current calculation I am using an outside diameter of 0.375". Solving for the inner diameter from the angle of twist formula with the max torque...

Although a torsion bar seems like a fairly simple system actually designing one to do what you want proves to be difficult. For some of the current calculations I have been making to get results that are within an allowable shear stress I am having to extend my torsion bar to as much as 62"...

The maximum length of the spring would be 5" so if your wire diameter is 0.5" you should be able to get about 10 active coils (I realize it will be less because we are placing the torsion spring in compression and tension so some spacing between the coils will be required to account for the...

That is a very interesting idea of placing a spring inside a tube to give you that extra torque that way you could reduce the amount of torque needed in the torsion bar. From the chart the units are actually in*lbs from calculations the maximum torque would be 4657 in*lbs. I take it that R in...

Your selecting a steel with Ftu = 180 ksi? If that is the case then Fty could be more around 160 ksi giving a Fsu around 80 ksi. I think to have a torsion bar thick enough with withstand the torque as well as the angle of twist would become much greater in length then I would want. (This is...

This is a real problem. The spring has to be able to have a 1/4 turn in both directions. The spring should live for around 10000 cycles. Do you know of any sources that can help me determine how this spring should be designed?

Thanks israelkk, I knew music wire generally had a smaller radius I just didn't know how small, looks like I will have to use a different material and rework the calculations. Any suggestions on a material generally used for springs that has a maximum wire diameter of about 0.5" ???

Thanks rb1957 you have been a big help in leading me to figure this thing out. I have a quick question about where are you getting your values?? The values I am using are from matweb and the material is: AISI 4140 Steel, normalized at 870°C (1600°F), reheated to 845°C (1550°F), oil quenched...

Thanks TheTick I have already done something very similar to what you are describing with matlab. The graph ended up looking something like this. I only considered an angle of twist from 0 to 90. At zero the lid is straight up and the torsion bar is neutral at this point (no pre-load). The...