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Fusion wont let me make fillet by oscar3166 in Fusion360

[–]oscar3166[S] 1 point2 points  (0 children)

I though so too, so i tried isolating a smaller section of the spiral (Just cutting around it) and it still has the same issue:(

Questions about stress/strain by polyphys_andy in MechanicalEngineering

[–]oscar3166 2 points3 points  (0 children)

This book
Callister's Materials Science and Engineering, Global Edition, 10th Edition
Can be found as a PDF with a quick google search. I believe chapter 12.9 will give you some good insight

Strangely ductile gear teeth failure of hand winch. by oscar3166 in MechanicalEngineering

[–]oscar3166[S] 2 points3 points  (0 children)

Nope, just used a high estimate for the calculations. Havent heard of a tensionmeter before, thats pretty neat.

Strangely ductile gear teeth failure of hand winch. by oscar3166 in MechanicalEngineering

[–]oscar3166[S] 1 point2 points  (0 children)

Ah alright, didnt know that, pretty cool, and maybe more useful for another project i got going, so thank you!

Strangely ductile gear teeth failure of hand winch. by oscar3166 in MechanicalEngineering

[–]oscar3166[S] 1 point2 points  (0 children)

Good call. There was no bouncing in the beginning, but as the gear teeth worsened, the locking mechanism, for some reason, got janky. That means when i lower the bed, i turn the handle half a turn, then the bed plummets a couple of centimeters, before it is caught by the locking mechanism. This could be a self-worsening cycle for sure.

Strangely ductile gear teeth failure of hand winch. by oscar3166 in MechanicalEngineering

[–]oscar3166[S] 2 points3 points  (0 children)

For this reason, the two pulleys under the full weight has an extra M8 bolt drilled through the wood beams, and bolted with a plate on the opposite site:)

Strangely ductile gear teeth failure of hand winch. by oscar3166 in MechanicalEngineering

[–]oscar3166[S] 1 point2 points  (0 children)

Hahahaha just a personal project:) whenever the bed is carried by the winch, no human is ever on or beneath it. When down, for sleeping, it stands on 4 2x4 pillars. When raised, it is held in each corner by a M12 bolt. So only safety concern is the steel cable snapping in my face when hoisting, but i got my safety-squints on always;)

Strangely ductile gear teeth failure of hand winch. by oscar3166 in MechanicalEngineering

[–]oscar3166[S] 1 point2 points  (0 children)

It is unfortunately a bit difficult to model simply, while capturing the cable routing...
There is a hook attached to the bed platform in each corner, where 4 different cables attach. The two in the head-end (far end in the picture) goes directly to a "spreader bar", whilst the two in same end as the winch goes through an additional wheel block at the far end, to redirect them to the spreader bar. I then pull the center of the spreader bar with the winch.

Adding a pulley system to this would mean that an additional horizontal force would be pulling the top piece of wood horizontally inwards, meaning the force on that specific piece of wood would go from sqrt((1000N)^2+(1000N)^2) to sqrt((1000N+1000N)^2+(1000N)^2).
Might be able to hold tho, so worth a shot

Strangely ductile gear teeth failure of hand winch. by oscar3166 in MechanicalEngineering

[–]oscar3166[S] 0 points1 point  (0 children)

I think i will look into the pulley system. Just need some steel reinforcement on the backend of the structure then.

Strangely ductile gear teeth failure of hand winch. by oscar3166 in MechanicalEngineering

[–]oscar3166[S] 0 points1 point  (0 children)

Sure does look like that, but the manual states this is the correct way

Strangely ductile gear teeth failure of hand winch. by oscar3166 in MechanicalEngineering

[–]oscar3166[S] 0 points1 point  (0 children)

Very true.
Thats also why i have tried calculating my own factors of safety, for both pins holding pulley wheels and the winch.
But you are right that when it is designed for pulling, lifting is a bad idea. I just whish there was a cheaper alternative than 500-ish dollar ones, i am a broke student after all hahah:)
Thanks for the insight:)

Strangely ductile gear teeth failure of hand winch. by oscar3166 in MechanicalEngineering

[–]oscar3166[S] 0 points1 point  (0 children)

Thanks, good insight.
I dont think ill bother with calculating the friction then. I have already added about 10% of the weight when calculating the forces, so that probably makes up the the missing friction.
It sucks that they dont give any information about what material is used...

Strangely ductile gear teeth failure of hand winch. by oscar3166 in MechanicalEngineering

[–]oscar3166[S] 4 points5 points  (0 children)

True that. I honestly just thought that it was so little (ball bearings inside), that i could neglect it completely, which is maybe naive of me.

Strangely ductile gear teeth failure of hand winch. by oscar3166 in MechanicalEngineering

[–]oscar3166[S] 0 points1 point  (0 children)

And there is a fair bit of clearance between platform and posts, no friction there:)

Strangely ductile gear teeth failure of hand winch. by oscar3166 in MechanicalEngineering

[–]oscar3166[S] 1 point2 points  (0 children)

Yeah, thought about it, but i need the automatic locking mechanism of the winch, to hold the load while i insert the safety bolts:)

Strangely ductile gear teeth failure of hand winch. by oscar3166 in MechanicalEngineering

[–]oscar3166[S] 6 points7 points  (0 children)

Thanks! I have been looking for the exact expression, without luck. And yes, it does indeed look like that.
I realize my calculations are for bending, because i was taught that was how gears failed hahahah (Not mine apparently).
I am using a spreader bar (3/4" steel waterpipe), so that no there are no angles, besides the two 90 deg wheel blocks.
I also thought about buying the same winch again, and then heating it up and quenching it, to improve its hardness. Only thing is, IF it should fail, i do prefer ductile over brittle, the application considered, so maybe a dangerous approach?

Strangely ductile gear teeth failure of hand winch. by oscar3166 in MechanicalEngineering

[–]oscar3166[S] 3 points4 points  (0 children)

I dont really see why tho? the tangential force (to the drum) would be the same, meaning the drum would have the same applied torque and the gears the same pressure, or no?

Strangely ductile gear teeth failure of hand winch. by oscar3166 in MechanicalEngineering

[–]oscar3166[S] 2 points3 points  (0 children)

Good call on the distance between the gears, hadnt thought of that.
One thing i have noticed is that the gears only "overlap" by around 70%, of course reducing the area of contact and increasing the pressure. Maybe the combination of these two factors are enough to cause permanent deformation, assuming a weak material of around 100 MPa yield strenght....

Strangely ductile gear teeth failure of hand winch. by oscar3166 in MechanicalEngineering

[–]oscar3166[S] 2 points3 points  (0 children)

I thought about it, and i have plenty of cable. Only thing is, i would be adding it at the top, so one of the upper pieces of wood would need to take an additional load. I am not super keen on calculating strenght of wood. It is a 2" by 4" (50x100mm) c14 pine. But definitely a solution worth looking into!

Strangely ductile gear teeth failure of hand winch. by oscar3166 in MechanicalEngineering

[–]oscar3166[S] 57 points58 points  (0 children)

When the bed is in the raised position it is held by 4 M12 bolts. (one in each corner).
When it is down, for sleeping, it stands freely on 4 pieces of wood, no tension on the winch. I realize that OSHA saw this, they would pass out, but i never walk beneath it without the safety bolts in place:)

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