sprocket vs gear box 3

[harrinshotmail]

The reduction ratio needed im our application is 1800.
Following are the ways to do it:

1. Use an AC invertor and bring its speed down to 140rpm. Then use worm reducing gear 60:1 ratio. Then use a sprocket to reduce the speed further by 4.5 ratio to get a final rpm of 0.5 rpm. The motor chosen is 865rpm
2. Use a 1740 rpm motor and use 2 sets of sprocket reduction to get 0.5 rpm and an ac invertor.
3. Use a double reduction worm gear and 865 rpm motor to get the final rpm to 0.5 rpm

Which of the above 3 is the best choice. The output torque required is 16000in-lb at 0.5rpm. Please suggest a choice from the above 3 or any other choice. The motor only runs few seconds only to rotate a dumper manually. So there is no heat problem. Please help.

 

[harrinshotmail]

The flat disc brakes are dumped. The inside dimensions of the cage are 38" high x 42" long. The parts basket which is placed inside is 34" high x 40" long. I am only giving two sides because the 3rd side is not important as it won't be used in the calculations. The basket has 4" high feet.

The axis of rotation is exactly 19" i.e. centre of the cage.
I just wanna verify my calculations if the part has 4000lbs and it is full. What will be the torque required to rotate it at 0.5rpm in 3s?

 

[rgajewski]

You may want to consider if the "load" is going over center, a system that will not allow the dumper to speed up. I'd prefer hydraulics over anything that has a chain. I can put a fuselink in the system to eliminate a run-away synerio.
Just my opinion.
Ray

Every once in a while the voices in my head have good ideas.

 

[diskullman]

Wow! This gets overcomplicated when asking a room full of engineers> From economic standpoint, I would buy a 1/4HP 1800:1 ratio gearmotor from Hub City, Ohio, Boston or other mfgr then use a sprocket on the gearbox output, getting to your final driven ratio. Direct coupling is more difficult to align, and the final sprocket drive will give you more options for mounting.

This type of question is why there USED TO BE local distributors. A little bit of engineering background with vast product knowledge, to custom tailor the application to the customer, creating the most efficient drive, both in energy usage and initial equipment and operating costs. This commodity has been replaced by your big catalog, and figure it out for yourself

Russell Giuliano

 

[harrinshotmail]

Let me ask this: if we have a worm gear box and a motor with 2hp attached to it how much hp and torque we loose from the motor to the gearbox motor due to the effeciency of the gearbox?
The question I am trying to get an answer is how do you calculate torque. Please read this thread and answer the question. I donot think I can put this question in bold font otherwise I will.
Russell: What type of gears will the gearmotor have: worm gear, I assume?

 

[MikeHalloran]

At 0.5 rpm, the moment of inertia is less important than the eccentricity of the load.

If you had a 4000 lb weight with its center located 19" away from the axis of rotation, then the worst case torque required to start rotating it would be the product of those two numbers, i.e.

T = W x r = 4000 lb x 19 in = 76000 in-lb = 6333 ft-lb

Which is pretty substantial. Maybe I'm misunderstanding the problem.

If you've got a rectangular basket that may be completely or partially full of heavy awkward stuff, you can't assume that it will be, or stay, uniformly distributed throughout the available volume. One bad case would be when it's all jammed up on one side, or worse, in a corner... in which case, assuming that it's all at the edge of the basket is not all that unreasonable.

Of course, it can all spontaneously fall to the other side of the basket, giving you an overrunning torque just as large as the starting torque.



Mike Halloran
Pembroke Pines, FL, USA

 

[spigor]

Harrinshotmail, according to a worm gear manufacturer's data a typical design can have efficiency in a range 0.4-0.91 and low values are for high ratios. It means even as much as 60% of the transmitted power could be turned into heat in the worm gear. If you want high efficiency and high ratio and still compact design then you should go for the modified epicyclic gear, but they probably don't sell them off the shelf, so it only makes sense if you want to produce a whole number of this stuff of yours.

 

[harrinshotmail]

WE cannot use your formula in this case because the load is not offset by 19".The center of gravity and the center of rotation are almost same. It may be only 1" to 2" out. So 4000 x 2" = 8000 in-lb or 666lb-ft.

I donot think we can ignore the inertia in this case.If the weight of the basket is 4000lbs.

T = 4000/12 x (40x40 + 34x34)x 0.017rad/sq.sec = 15617 in-lb i.e.131lb-ft(you can see that this is double). In calculating Inertia we can add to the inertia the square of the offset distance with the load, I mean, 4000x2x2=16000lb-sq.in and the new value of torque will be 1324 lb-ft

Since T =Inertia x angular acc.

Assuming t= 3s N=0.5 rpm ang acc will be 0.017 rad/sq.sec

i totally understand the load will be shifting but the weight will be decreasing as we will be emptying the basket too.

2nd question repeated: if we have a worm gear box and a motor with 2hp attached to it how much hp and torque we loose from the motor to the gearbox motor due to the effeciency of the gearbox? I'll give an example:
If u have a 2 hp motor connected to a worm gear box at 1740 rpm the torque will be 72in-lb. Now what will be the value of hp and torque at the other end of worm gear if it is 60:1 ratio and the effeciency is 35%.

Please see the picture of the dumper

 

[eromlignod]

Oh brother! Tell me that's not made out of 80/20!

My car doesn't even weigh 4000 lbs! Are you sure that slotted-aluminum contraption with little bearings will even support the weight?

I think I'm going to run away from this one.

Don
Kansas City

 

[gearcutter]

As hydtools originally suggested; I would look at doing this simple job with a simple single hydraulic ram & rotating arm arrangement. You would end up with, simple to design, both speed and proximity controls. As an example, look at how a skip bin type garbage truck does the job of rotating the bin and get some ideas from that.

Ron Volmershausen
Brunkerville Engineering
Newcastle Australia

http://www.aussieweb.com.au/email.aspx?id=1194181

 

[gearcutter]

I'm sorry, I've just read one of your responses where you mention the requirment for 360deg rotation. Perhaps a ram may not do what you require.
Why is the full rotation required?

Ron Volmershausen
Brunkerville Engineering
Newcastle Australia

http://www.aussieweb.com.au/email.aspx?id=1194181

 

[gearcutter]

A ram could do the job if you use a rack & pinion arrangement. The rack would be attached to the ram imparting motion to the bin via the pinion. This would give you full rotation but may not suit your application as it would require cycling of the ram to the return position.

Ron Volmershausen
Brunkerville Engineering
Newcastle Australia

http://www.aussieweb.com.au/email.aspx?id=1194181

 

[harrinshotmail]

For Don:I have this equipment running for 10years.

I donot need 360 degree but atleast 270 deg. This we we can insure that there are no parts left inside.

I just need to order few more.so I am looking for best possible way to design the same thing. I need to know what are the different possible ways to achieve this- with worm gear, AC drives, sprocket, may be all of them but what is the best way to achieve the rpm and torque.