# Bands Cut Calculator



## jazz

Hi all,

Before I start please note that this topic is not about bands WEIGHT calculator that I presented in the forum some time ago.

This is Bands Cut Calculator that helps to measure points on a sheet of rubber which are then connected to make lines along which to cut it.

If you are like me than to determine where to cut, say, four tappered bands, especialy if the widths are not "round" but look more like 2,35 with 1,75 cm - the numbers likely to come out of other band calculators such as Jorg's (http://www.slingshotchannel.com/band_calc.html) - then it becomes very difficult. (Even 2,3 and 1,7 are not easy both in calculus and in physical terms..)

It is difficult for various reasons, at least for me:

- I need to calculate that part of the rubber which I call REST and which is neccessary to cut out in order to get the first side of the first tappered band;

- same with the last cut, if you want to be left with a sheet of rubber which is again proper rectangle than you have to take away another REST;

- RESTS are halves of the differences between wide and narrow side which when put together with wide and narrow ends cummulate up in numbers which look more and more difficult to rebmember and work with;

- on the other side, if you do not want to apply cummulative method then you have to calculate in steps looking at your ruler something like 0,75, then up 2,30, then up 1,70 etc.

Even when the bands are equal (untappered) and if you want to cut 4 or 6 bands whose dimensions are again something like 2,3 - 1,7 cm the thing becomes clogged for people like me.

In order to help myself, I made a simple calculator which needs only two inputs: wide side and narrow side dimensions of the bands and it calculates all the points on the left side and on the right side along these two vertical lines along which you mark the points on the sheet of rubber. I made a modification which helps calculate untappered bands.

Here is an illustration that simulates lines for a given width of wide an narrow sides on a sheet of TBG:









And here is the Excell file (I like to call it "program", sounds cool..):

View attachment Bands Cut Calculator.xls


It worked for me, maybe it will work for somebody else.

Please send me your comments and suggestions.

Stay tuned, more calculators comming!

cheers,

jazz


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## Pawpawsailor

This is a great tool! Thanks!


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## Saderath

A very useful tool! Great idea!


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## stej

Cool. I haven't realized that there is a REST that should be considered also. Although I think if I don't count with the rest, it doesn't matter much. But if I want to be precise, I will take care I count the REST in  Thanx.


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## jazz

Hi all, thank you for you interest, and if you ever use this utility please give me some feedback so I migh change some things if neccesary.

Hi stej

The REST is something you do not have to consider at all but with tappered bands it is easier. I call it "rest" but probably there is a better word in english so we can change it. The following illustration:

shows that even with only one band to be cut out of a sheet of rubber (I mimicked a piece of TBG) you have couple of points to consider:

- The REST at the bottom allows you to properly do the first cut and come to the first point on the left side which is 0,5 cm in this case and makes your band properly tappered (lower edge)

- The rest at the top is also not neccesary but might be wise if you want to be left with the remnant of the TBG sheet (whole gold coloured upper piece) with a stright bottom line so that next cut you starts from a stright line - unless you intend to cut later same tappered bands, then you might leave it.

The table in the illustartion illustrates this simple yet not so simple case of only one band but with couple points to consider. Just analyse the illustration and the table and everything should be self explanatory, well, because it is not a big science anyway; this way to cut the tappered bands is not mine - I picked it somewhere, most likely in the forum, and I only made a utility that helps this calculus which can be annoying (at least to me).

If you do not want to consider the REST, you can do it but then your tappered bands must be positioned in an angled position in relation to the sheet, to be honest I do not konw how I would do it, and the following illustration shows it (I hope that the slanted band contour is fairly visible; maybe try to zoom to the left and to the right side):

I made this utility for myself some months ago, it works fine, and I polished it a bit for placing it in the forum.

cheers,

jazz


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## jazz

Hi all,

here are the two illustrations, sorry for this inconvenience:

















cheers,

jazz


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## stej

Thinking about it.. consider you don't work with REST and you want to cut tapered bands 2.5 * 1.5. You measure 2.5 on one side and then 1.5. The same at opposite side with opposite order, right? You cut them and the ends are uneven because you don't consider the REST.

Now what if you cut the ends on both sides so that the cuts are even again? The area is much smaller so you don't have such huge offcuts. The algorithm in XLS would have to count with it of course.


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## jazz

Hi stej,

can you please post an illustration showing what you suggest, I am not sure I understand it completely. But whatever it is I am looking forward to the possibility to save some rubber..

cheers,

jazz


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## stej

Hi jazz...

I wanted to come up with algorithm how to count it, but didn't manage it under time pressure..

So I'm attaching your image with proposed cuts. It of course shortens the band a little bit, so it's needed to cut the band 'little bit' longer. I hope you understand


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## jazz

hi stej,

now I understand! As far as I can see, and depending on how you pile bands on top of each other, the whole surface will have a tendency to go either circular or zig-zag, depending if you pile them same sides above each other or you change narrow-wide etc., which would bring new problems. On the other side I think that it looks promissing...

However, I think that I should make this in reality just to be sure.

Thank you for your interest and I will come back to you when I get some results.

cheers,

jazz


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## stej

Great 

However, I don't understand the problem with piling the bands.. Could you explain that?


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## jazz

hi stej,

Sorry, this is probably my english; I mean cutting more than one band so you draw them on top of each other.

In that sense, you can have same widths on one side (narrow, narrow..) and then their joint shape tends to make a circle as in this illustration:









or you can altrenate them as in my drawing at the beginning of this post (the concept I picked up somewhere here in the forum I guess);

or, if I follow your drawing right, if you also alternate them but align the bottom line of the first band with the bottom of the sheet of rubber (which is here assumed to be rectangular) then you get again a very normal drawing except that it joint shape is slanted on one side - more and more as more bands are drawn, as in this illustration:









Now, I know that there is again possibility that I did not understand you right. If this is so then I would kindly ask you that when you have more time you make a drawing with, say, four bands to be cut (just to be consistent with this thread) 2,5 to 1,5 cm from a given (any) rectangle sheet of rubber so that I understand it better then.

This discussion is important to me, and I have to say again - because TBG is gold for me, I do not waste even a bit of it so that I am very interested in understanding your point.

cheers,

jazz


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## Trap1

Hi,

I tried to PM you but got a message saying that you 'could not accept any messages' is this a quota thing?

Regards

John


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## jazz

Trap1 said:


> Hi,
> 
> I tried to PM you but got a message saying that you 'could not accept any messages' is this a quota thing?
> 
> Regards
> 
> John


I really do not know, Trap1..!

If it is some quota than it is not related to me since I had one PM in quite some months.. Tray again later and if not place whatever you intended here in this thread, or you can send me an email at [email protected]

cheers,

jazz


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## Trap1

jazz said:


> Trap1 said:
> 
> 
> 
> Hi,
> 
> I tried to PM you but got a message saying that you 'could not accept any messages' is this a quota thing?
> 
> Regards
> 
> John
> 
> 
> 
> I really do not know, Trap1..!
> 
> If it is some quota than it is not related to me since I had one PM in quite some months.. Tray again later and if not place whatever you intended here in this thread, or you can send me an email at [email protected]
> 
> cheers,
> 
> jazz
Click to expand...

Hi Jazz,

I tried PM again & same problem so I sent email to above addr. Maybe it is me tho I see if I can contact a moderator & find out!

John


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## RioRodent

With regard to the discussion above about where the "Rest" should be....

Is there really any need for the end of the bands to be 'square', since they are trimmed off after tying to both the pouch and the frame?


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## jazz

RioRodent,

I must admit that I do not completely follow your thought probably because English is not my first language; if you could do a drawing of what you mean it might help me since I intend to make a piece of software out of this Calculator (not as an Excel file) and any suggestion by the user is very valuable to me.

Thanks,

jazz


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