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How to calculate force for problem attached.
4

How to calculate force for problem attached.

How to calculate force for problem attached.

(OP)
Hiii

I need to calculate force required(F1) to pull the plate out with block leaving behind on Floor(to eventually calculate motor HP).

If
W1 is Weight of block
W2 is weight of plate
Cf1 is Coefficient of friction between block and plate
Cf2 is coefficient of friction between plate and floor

Anyone contribute anything on this will be really helpful.


Regards

RE: How to calculate force for problem attached.

(OP)
Sure IRstuff

We manufacture machinery used in Hard coke oven plant.

and this plate carry compressed cake which is placed inside coke oven and after that plate is pulled outside leaving cake inside coke oven.

We wanted to calculate motor required to pull this plate outside and also chain that be used for same and hence wanted to know force required.

I hope detail will be sufficient if need any other detail please let me know

Regards

RE: How to calculate force for problem attached.

Is this any more simple than ((W1 x g) X Cf1) + (((W1+W2)x g) X Cf2) ?? with weight in kg and G = 9.81

With the Cf, there will be a static value and a kinetic or moving value which is normally a bit lower than the static one

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

RE: How to calculate force for problem attached.

ask a magician how he can remove the table cloth form under the dinner settings. you want to pull really hard on the plate so that the inertia of the body overcomes the friction from the plate ... tricky.

only slightly more seriously ('cause i think the above idea could lead somewhere), can you incline the plate? how do other people do this?

Quando Omni Flunkus Moritati

RE: How to calculate force for problem attached.

I'm not sure I'd trust any Cfs unless they were derived empirically from actual measurements of the actual situation, at which point I'd know how much force is required anyway. Then I'd throw a "safety" factor of 3 or more at it anyway just for the day after " ♫ Someone left the cake out in the rain ♫ ."

Some types of motors pull REALLY hard when started from zero rpm, and some don't. I'm guessing you have a gear reduction and maybe a clutch in there somewhere too.

RE: How to calculate force for problem attached.

(OP)

above mentioned system is already implemented.

What we do is we stop the block by structure whose wheels rests on plate.
when plate is pulled structure stops the block from moving along the plate. while structure rolls on plate

We cannt incline the plate due to various constraint.

As the cake is too big(34 tonne) so cannt think of pulling it hard too.

We wanted to calculate force. i hope calculation mentioned by LittleInch will help.

regards

RE: How to calculate force for problem attached.

(OP)

tmoose There will be gearbox after motor.

RE: How to calculate force for problem attached.

(OP)
Thanks everyone for their comments

I will make my calculation as instructed by LittleInch

If someone have anything to add please let me know, that will be really helpful.

RE: How to calculate force for problem attached.

i have a feeling that the force is only part of the solution, I think how quickly it is applied is critical to success (remember my party trick analogy).

with LI's calc, one of the Ws is the plate, negligible compared to the weight of the body? but when you pull the plate, what stops the body from moving? how'll the body react when it has a force of Cf*W applied to it? I guess part of the problem is to get the body slipping on the plate very quickly 'cause once the body is sliiping there is much less friction force going into the body, limiting the impulse/work on the body.

Quando Omni Flunkus Moritati

RE: How to calculate force for problem attached.

This does presume that your "structure" must likewise resist the force W1 x g) X Cf1, since that's where it'll be manifested, and it's what keeps the cake from going with the plate. The structure won't have to resist the force required to overcome the friction from the bottom of the plate, since that's the oven itself.

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RE: How to calculate force for problem attached.

'cept that the "structure" is on wheels ? maybe it's chocked somewhere ??

Quando Omni Flunkus Moritati

RE: How to calculate force for problem attached.

ISBind:
I would look long and hard at what you have been using, what has been working. The equipment for the coke oven industry has been around for a long time, is tough as hell, with design factors of safety of 3, 4 or 5, due to wear and tear. This is because any failures cause a real mess in the process, the working environment is absolutely awful in terms of heat, abrasive/hard materials being handled, difficult and lack of maintenance, etc. etc. I don’t know that I would try to reinvent the wheel on this type of equipment, rather try to improve the details which are causing any problems. A slight change in chain size or motor size may not be a great savings, and may just add to inventory complexity at the plant. I would assume that coef. of friction can vary all over the place, as a function of the coking coal used, the coke turned out, and mostly how clean the running tracks, guides, wheels, your bottom plate, etc. between each application of the plate pulling operation. I would think that getting a handle on these values might req’r. some testing at each plant and with each different piece of equipment. What sizes of motors, chains, etc. are being used now and how long do they last. Then what can I do with my design to clean tracks, guides, wheels, etc. to minimize the grinding friction of clogged guide ways, so they work better?

RE: How to calculate force for problem attached.

I would like to add that the friction values might be hard
to determine. I used to work in the heat treating /material handling
business. Hot metal can be very "sticky"

RE: How to calculate force for problem attached.

(OP)
Hello everyone

Said "structure" will be locked by hydraulic cylinder from sides

That way structure will stop the Coal Block from moving where as its wheel will allow it to move with plate

RE: How to calculate force for problem attached.

then it should be as "easy" as LI posted above ... once you have good data for the range of Cf

Quando Omni Flunkus Moritati

RE: How to calculate force for problem attached.

For a specific detailed answer, you need to provide the following information:
The weight of the plate= Wp
The weight of the block= Wb
The material of the floor=Mf
The material of the plate= Mp
The material of the block= Mb
Then anyone can calculate the static coefficient of frictions called U1 and U2, put all of that in the following formula to obtain the Required Force:
(Wp+Wb)*U1+Wb*U2= RF

RE: How to calculate force for problem attached.

"Then anyone can calculate the static coefficient of frictions called U1 and U2" ... aye, there's the rub ...

Quando Omni Flunkus Moritati

RE: How to calculate force for problem attached.

(OP)
thanks for showing interest

weight of plate 21 tonne
weight of block 34 tonne
plate M.S.
floor brick
block coal

how to calculate U1 and u2???

i know it seems stupid but is there any software that can verify this?? like can it be checked in any analysis software???

and we dont have any friction factor available

Regards

RE: How to calculate force for problem attached.

have you tried coming up with a friction factors via interpolation/extrapolation of existing material data? Chances are you'll have to fill in the friction factors yourself if you use software.

also, can you draw us the FBD of the block itself? The block will go with the plate when you pull it out slowly (as there is no inertial tipping moment) so your design does incorporate some form of resistive force opposing F1? Unless your plate moves at speed of light i can't imagine the block staying in the oven

RE: How to calculate force for problem attached.

"The block will go with the plate" ... isn't there some structure resisting the body?

Quando Omni Flunkus Moritati

RE: How to calculate force for problem attached.

ISBind:
Reread my first post for some of the deeper meaning btwn. the lines. You are not going to find these friction factors in some nice clean mech. engrg. handbook list or some computer program. In that industry, these are brute force calcs., not finesse calcs. If you really want to know what those avg./approx./max. friction factors or forces are, you’ll have to measure the force it takes to push that plate in and out empty; and then do the same test with the block of coal in place. Do this at each plant (for different oven design details, etc.), at different oven positions (for plate guidance system fit-up, clogging, etc.); do this as many times as you want and look at the averages and the max. force required, for some design criteria. Then, back calc. for some Coef. of Friction if you wish. With your OP and your latest post, you seem to expect this to be some nice M.E. text book problem. It is not, in the slightest. I wonder if the smarter thing to do wouldn’t be look at what’s working and not working very well, or needs continuous repair, and ask what can I do in the way of design to improve that performance. RE: motor HP, what are they using now, and how long is it lasting? Long life means maybe you can reduce the motor size a bit, for a few dollars saved; maybe downsize gearbox, chain, etc. But, you’ll more than use that savings the first time one of these parts fails. Calculating the motor HP the way you are trying to do is a really tough assignment. Refining what’s working may be the easier route, or at least knowing what works is a good starting point for a design improvement or new design.

RE: How to calculate force for problem attached.

"Long life means" it's working well .. don't touch the damn thing!

Quando Omni Flunkus Moritati

RE: How to calculate force for problem attached.

i know it seems stupid but is there any software that can verify this?? like can it be checked in any analysis software???

and we dont have any friction factor available


What order of magnitude hp u talking about? there are application sales engineers all over the world who would love to come look at ur application and 'SIZE" it for you in exchange for chance to SELL u there stuff. CALL THE EXPERTS who sell ur size motor and invite them to come SIZE this for you?

Meanwhile if YOU want try YOUR hand at figuring this out yourself, try this free sizing software that can model this applicatioin:

http://www.kollmorgen.com/en-us/service-and-suppor...

www.KilroyWasHere<dot>com

RE: How to calculate force for problem attached.

rb1957: "The block will go with the plate" ... isn't there some structure resisting the body?",

Yeah there is, ISBind mentioned some kind of resistive component with wheels. But that resistive force was not indicated on his first FBD.

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