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Discussion Starter #1
How would I estimate the number of cells on a top bar frame without actually counting? My top bar cavity will be approximately 10" high, 18" across the top, and 7" across the bottom.

Thanks for any help.

Kevin
 

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Convert your KTBH shape into square, thusly:


then multiply height by width to get the area of each comb. Then seek out how many cells there are to a square inch - I believe Michael Bush's site has this kind of information - and run the numbers. Make an allowance for gaps at the sides and bottom of the cavity.

Just curious - is there a specific reason you need to know this kind of info ?
'best
LJ
 

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Discussion Starter #3
Hi Little John,

Thanks for your suggestion as I think I can do that :) I did see Michael Bush's page regarding cell counts on various Langstroth frame size so can refer back to that after I do my calculation.

Regarding your question as to why - one reason was simply to have a better understanding as to what is going on in my top bar hive regarding egg laying from the queen (i.e. how productive is she, etc.), expected future brood to emerge, and so on. The second reason is just trying to relate information I read and hear about Langstroth frames to my situation. After doing the calculation, I will be curious to see if my frames approximate a deep frame or medium, for example.

Again, thanks for your suggestion.

Kevin
 

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Hi Kevin - thanks for the interesting reply.

One other thing you could consider, is to make-up a one-inch square 'hole' in a sheet of paper - either by cutting the square out, or making-up a 'frame' and creating such a hole in the process using paper strips and sellotape - and then placing that hole over one of your existing combs and counting just the cells which appear within that square.
That would probably give you a more accurate figure than MB's site (for your own particular size of bee) if you think it might be worth the effort.

Whatever ... good luck with this.
'best
LJ
 

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A hexgon that measures 4.9mm from flat to flat has an an area of 20.8 mm^2. That would be 4.8 cells / cm^2. That would be an upper maximum because honey cells and drone cells will be larger.

Here is an online hexagon area tool you can use for the comb your bees are actually building. Count out twenty cells in a row and measure the distance. Divide the distance by 20. Go to this website. If you measured side to side then put that distance in as the side to side length. If you measured vertex to vertex then put it in as the vertex to vertex length. It will give you the average area of those 20 cells.

If we take the cavity dimensions and assume a perfect trapezoid minus bee space then the largest comb they could build is 114 sq. in or 735 sq cm. (17.25+6.25)/2 * 9.75 = 114. This is the upper maximum that the area can be.

If we assume its all 4.9mm cells (It isn't and you know what they say about assumptions) then we have 3528 cells per side. That is an upper limit to your estimate, it won't be more than that.

A Langstroth deep with 4.9mm foundation has 3698 cells per side.
 

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I would argue cell size is unlikely worth the OPs time and effort, it a moving target

flip side is , yes knowing your comb volume vs a lang is handy
 

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Using a snip from MSL's pic, could not a reasonably accurate cell count be found by counting cells along the 2 lines i have drawn then multiplying? After squaring the comb using Little John's method?

 

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Using a snip from MSL's pic, could not a reasonably accurate cell count be found by counting cells along the 2 lines i have drawn then multiplying? After squaring the comb using Little John's method?

OP was looking for an estimate for comparison so I think you could do that. The longer the count line then the better the average.

But Kevin said he was curious to see if the top bars approximated a deep or a medium.

LJ's method of squaring the comb is mathematically expressed as ((A+B)/2) * H. The dimension Kevin gave us was the chamber size, not the comb size, so we have to allow that the comb doesn't usually touch the wall and floor in a TBH. Up above I had an maximum possible area of 114 sq. in. I got that by subtracting 3/8 of an inch bee space from both sides of the cavity top dimension and the cavity bottom dimension and subtracting 1/4" from the cavity height and plugging those number in. In practice the real area will be smaller than on paper numbers.

A Langstroth Deep has an area of 162 sq. in. OPs top bar will have 70% of the area of a Langstroth deep IF it is built out perfectly. A Langstroth medium is 64% of a deep, and since we can't count on each top bar comb being built to the maximum area then a useful comparison might be to compare each top bar to a Langstroth medium. That might be more useful to Kevin than number of cells.
 

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Discussion Starter #11
Thanks to all, but especially JConnolly for the math and answering my question for me! As he mentioned, I will assume that my frames are essentially Langstroth mediums.

Kevin
 

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A Langstroth Deep has an area of 162 sq. in.
I have used 134 in the past based on a cad model , the one I just measured came to 136 :kn:
 

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Discussion Starter #13
I hate to throw people into the octagon, but would folks say my frames might be closer to a deep or medium?

:s
 

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I have used 134 in the past based on a cad model , the one I just measured came to 136
MSL is right. Good catch. Thanks.


It is 136. The inside of a frame is 17x8. 162 is wrong and I've no idea where that came from. I went to a Google spreadsheet that I keep and the spreadsheet has 136. But somewhere between looking at my spreadsheet and switching back to my mobile app, 136 came out as 162.


So, Kevin's top bar, if it is perfectly built out, will be 84% of the area of a Langstroth deep, or halfway between a deep and a medium. I think that in actuality he can plan on it being closer to, but slightly larger than, a medium.
 

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Discussion Starter #15
I really cannot thank JConnolly and MLS enough for your help. Most kind of you both to do this - thanks!

Kevin
 
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