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Hand Cranking for a Assembly fixture rotation
3

Hand Cranking for a Assembly fixture rotation

Hand Cranking for a Assembly fixture rotation

(OP)
Hi,

I need a hand cranking methods to rotate by 1600NM. I was searching in Boston gears but unable to find out.
The fixture rotation rpm is 0.5.
Thanks!

RE: Hand Cranking for a Assembly fixture rotation

1600 newton-meters (torque) at 0.5 RPM, by hand? Is that about 0.1 horsepower ?

It would get tiring after a bit.

RE: Hand Cranking for a Assembly fixture rotation

I think you want a speed reduction gear-train … 80Nm at 10rpm would drive 1600Nm at 0.5rpm

another day in paradise, or is paradise one day closer ?

RE: Hand Cranking for a Assembly fixture rotation

Yeah - the HP continuous output of a pair of human's legs for someone in good shape is about 0.1Hp. Hand cranking will work for about 10-30 seconds or so for anyone not on a sailing team.

They make gear stages so just add them together if the input force is too high, but each adds friction and eventually that goes south. Lowering the input force means increasing the input rate, so you get a different set of metabolic problems.

RE: Hand Cranking for a Assembly fixture rotation

Even the vague possibility of this being a 737 application is slightly disturbing to me.

RE: Hand Cranking for a Assembly fixture rotation

why "737 application" ?

another day in paradise, or is paradise one day closer ?

RE: Hand Cranking for a Assembly fixture rotation

Cause it's a high torque handcrank mentioned in an aicraft discussion board. It makes me think of the cursed 737 max trim crank.

RE: Hand Cranking for a Assembly fixture rotation

If the stab is turning 1/2 RPM then things have totally gone south. And selecting from Boston Gear on an aircraft application is the wrong place to begin.

RE: Hand Cranking for a Assembly fixture rotation

(OP)
Hi 3DDave

I have chosen the Haacon Type 242.3 Manual crank to do this.
Please give your comments
Thanks!

RE: Hand Cranking for a Assembly fixture rotation

Wait - you have a random design which seems impractical based on power availability from any normal person and you would like me to go and find documentation for a random some mechanical thing? To say what about it, exactly?

RE: Hand Cranking for a Assembly fixture rotation

I guess that he wants you to check that it's ok to support the torque selected by a random person (me) in the internet
based on a guess.

RE: Hand Cranking for a Assembly fixture rotation

1600 newton-meters (torque) at 0.5 RPM.

When you see torque and RPM, you should instinctively calculate the associated power.

Wolfram Alpha says that's 0.112 hp.

If it's continuous, then you'll need one of these (offered as a visual aid to assist with clarifying thoughts):



If it's just to adjust a fixture once in a while, then either back away from the 0.5 RPM requirement, or add an electric motor.


RE: Hand Cranking for a Assembly fixture rotation

3D Dave,
It looks like you have an "Action Item". Just be glad he didn't put in a due date. glasses

RE: Hand Cranking for a Assembly fixture rotation

(OP)

Sorry for the in-proper information!
Actually i need to rotate a heavy loaded fixture overhanging on an axis. And this one needs to be rotated by hand crank method.
I calculated the maximum torque 1600 NM.
And it is not a continuous rotation.
I searched and found the Manual crank (Haacon Type 242.3).

RE: Hand Cranking for a Assembly fixture rotation

I think you're misleading us with "output rpm = 0.5", when you add "it is not a continuous rotation" (which is implied by stating an output rpm).

I think you should say you have to rotate the mass through 180deg? in 15sec?

Sketches still very simplistic. If you think you've found a handle to work, why ask us ?

another day in paradise, or is paradise one day closer ?

RE: Hand Cranking for a Assembly fixture rotation

Ideally, a fixture would be designed so that the axis of rotation is in-line with the system's center of mass. Then the item could be easily rotated with a fingertip.

If that's impossible here, then it's a lifting exercise. The rotation is essentially incidental. So one should be searching for a winch assembly. Or a jack.

...And redundant straps in case someone bumps into the rachet pawl.

RE: Hand Cranking for a Assembly fixture rotation

Aerovelo Human-Powered helicopter is maybe the ultimate optimization for this.

Aerovelo Atlas - Sikorsky Prize

This is a forum for practicing engineers. School projects are not generally welcome.

RE: Hand Cranking for a Assembly fixture rotation

(OP)
@SAITAETGrad
This is not for a School project!
I am designing a tool to rotate and position the heavy equipment
I am finding difficulties to calculate the torque for eccentric load of 680kg.
The axis of rotation is horizontal and the distance between Center of mass and Center of rotation is .25m

I am using τ=Iα
Here is the confusion, when i calculate Alpha:
I am using manual crank and there will not be any continues rotation. I just want to rotate and position the equipment. In this case when i change the rotational speed(n) my output torque value is drastically varying.

If any one can give me the clarity that how to calculate the Speed of rotation for manual crank? Or we simply take 60RPM for Torque calculation?

Thanks!

RE: Hand Cranking for a Assembly fixture rotation

A manual crank back at the axis of "rotation" is not the correct approach.

By the time you have the gearing ratio to lift 680kg, upon release it'll spin at "a million" RPM killing someone.

RE: Hand Cranking for a Assembly fixture rotation

(OP)
What if i am adding counter weight to match COG and COR?

RE: Hand Cranking for a Assembly fixture rotation

Then you'll have the opposite problem when the 'Unit Under Test' (UUT) is removed from the fixture.

---

You should be able to design a cradling fixture that can be attached to the UUT, to allow it to be lifted from its cart. The lifting is by winch, with due concern for all possible failure modes. Redundant support must be provided, at ALL times.

The axis of rotation would be through the CoG, allowing effortless rotation. That way you actually could use a little hand crank to perform the rotation. BECAUSE the lifting force has been dealt with separately, by the winch.

The above suggestion does not constitute Engineering advice. You really should find someone to assist you with this. 680kg is more than sufficient to crush your coworkers.





RE: Hand Cranking for a Assembly fixture rotation

(OP)
we have proven this design with electrical motor and Hydraulic jacks
But now we decided to increase overhanging distance and also wanted to move from electric and Hydraulic to Manual

so i decided to go for Screw jacks for lifting and Gear drive for hand crank

the whole structure looks like Frame welding fixture but we are using this tool for assembly also. Hence we need to rotate and position accurately

And still i did not find the Correct Torque calculation for offset/overhanging load!

RE: Hand Cranking for a Assembly fixture rotation

do you mean T = F*d ?

another day in paradise, or is paradise one day closer ?

RE: Hand Cranking for a Assembly fixture rotation

Gopalakrishnan -

Thanks for the clarification.

Agriculture uses hand winches like these to lift grain augers.

From memory, once you get that type of crank moving, it is turning at a rate of approximately 180-240 RPM.

Most augers these days come with hydraulic lifts and wheel drives to make handling easier.

I think this is an application niche similar to yours.

RE: Hand Cranking for a Assembly fixture rotation

(OP)
rb1957

Torque = Force X Distance is the basic formula.
But i do want to calculate the torque for over hanging load with COG eccentric to Center of rotation!

RE: Hand Cranking for a Assembly fixture rotation

why wouldn't the torque due to the weight about the axis of rotation be W*d ?

This is the static torque you have to apply to the structure to stop it rotating (it wants the CoM to align with the CoR).

Then you have to apply additional toque to get the thing to rotate, that'd be I*alpha.
There is also the option of looking at the problem from an energy perspective (as you've lifting the CoM).

another day in paradise, or is paradise one day closer ?

RE: Hand Cranking for a Assembly fixture rotation

Gopalakrishnan -

Looks like a good option on the face of it. But I can't determine if this meets your regulatory and design requirements.

RE: Hand Cranking for a Assembly fixture rotation

Hopefully you already considered this? Be very careful of the possibility of back-driving the mechanism. If the drive mechanism is not somehow self-locking, letting go of the hand crank will allow it to spin freely, and break somebody's arm.
I don't know this particular product at all; presumably this is what the catalog page described as "internal self-actuating load brake."

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