Author Topic: Pyramid /Molle/ Thickness Question  (Read 2208 times)

0 Members and 1 Guest are viewing this topic.

Offline DC

  • Member
  • Posts: 10,396
Pyramid /Molle/ Thickness Question
« on: March 19, 2019, 12:04:21 pm »
In the picture the black line is an arc of a circle. Assume it's a pyramid limb so theoretically it is the same thickness all over. Now let's make a Molle. Cut it off and splice on a lever. The red line is the lever. If I push on the end of the lever with the same force as we used for the full limb does the shorter section of the arc still retain the circular, pyramidal, even thickness properties? I'm thinking yes but there's a lot smarter people out there than me.

Offline NonBacked

  • Member
  • Posts: 99
Re: Pyramid /Molle/ Thickness Question
« Reply #1 on: March 19, 2019, 01:53:51 pm »
DC –

For the Mollie design, if you pull the tip of the RED line even with the tip of the BLACK line, the working portion of the limb will be under more strain. So, adjustments need to be made to maintain the draw length: 1. wider & thinner working limb, 2. Longer working limb, 3. Thinner limb & lower draw weight.

That’s the fun part of Mollies…lots of options.

Offline bushboy

  • Member
  • Posts: 2,256
Re: Pyramid /Molle/ Thickness Question
« Reply #2 on: March 19, 2019, 07:09:41 pm »
Not sure if this is a help,but this is what I go for in a pyramid mollegebet self bow
Some like motorboats,I like kayaks,some like guns,I like bows,but not the wheelie type.

Offline Rākau

  • Member
  • Posts: 244
  • Aotearoa-the land of the long white cloud
Re: Pyramid /Molle/ Thickness Question
« Reply #3 on: March 21, 2019, 12:40:35 am »
grouse tiller shot bush. I'm struggling through a molly at the moment and that photo will help.

Offline sleek

  • Member
  • Posts: 6,681
Re: Pyramid /Molle/ Thickness Question
« Reply #4 on: March 21, 2019, 06:20:18 am »
In the picture the black line is an arc of a circle. Assume it's a pyramid limb so theoretically it is the same thickness all over. Now let's make a Molle. Cut it off and splice on a lever. The red line is the lever. If I push on the end of the lever with the same force as we used for the full limb does the shorter section of the arc still retain the circular, pyramidal, even thickness properties? I'm thinking yes but there's a lot smarter people out there than me.

Assuming both are the same thickness and width, if you pull both with the same amount of pressure, the Molly will bend further, with a tighter radius. If your goal here is to have the tips end in the exact same spot under the exact same draw weight, then you need to make the Molly wider,  and thicker. Thickness will increase its bend radius and bring the tip up to meet the pyramids tip, the extra width will compensate for reduced working limb mass and allow you to keep the draw weight the same.
Tread softly and carry a bent stick.

Dont seek your happiness through the approval of others

Offline DC

  • Member
  • Posts: 10,396
Re: Pyramid /Molle/ Thickness Question
« Reply #5 on: March 21, 2019, 09:44:09 am »
You guys aren't quite answering the question I asked. I probably asked it wrong. I'm just wondering if a section of a pyramidal limb will still bend in a circular way? Rather than elliptical.

Offline sleek

  • Member
  • Posts: 6,681
Re: Pyramid /Molle/ Thickness Question
« Reply #6 on: March 21, 2019, 10:17:57 am »
You guys aren't quite answering the question I asked. I probably asked it wrong. I'm just wondering if a section of a pyramidal limb will still bend in a circular way? Rather than elliptical.

Yes
Tread softly and carry a bent stick.

Dont seek your happiness through the approval of others

Offline PatM

  • Member
  • Posts: 6,737
Re: Pyramid /Molle/ Thickness Question
« Reply #7 on: March 21, 2019, 10:30:37 am »
The whole elliptical versus circle is a bit silly.  A circle IS an ellipse.  It's all a matter of degree and shape of bend.

Offline sleek

  • Member
  • Posts: 6,681
Re: Pyramid /Molle/ Thickness Question
« Reply #8 on: March 21, 2019, 10:36:39 am »
The whole elliptical versus circle is a bit silly.  A circle IS an ellipse.  It's all a matter of degree and shape of bend.

Its more of a rectangle than a square really...
Tread softly and carry a bent stick.

Dont seek your happiness through the approval of others

Offline DC

  • Member
  • Posts: 10,396
Re: Pyramid /Molle/ Thickness Question
« Reply #9 on: March 21, 2019, 11:25:57 am »
Yeah, I was just wondering if the shape would change with the straight outer limb.

Offline sleek

  • Member
  • Posts: 6,681
Re: Pyramid /Molle/ Thickness Question
« Reply #10 on: March 21, 2019, 11:45:37 am »
Yeah, I was just wondering if the shape would change with the straight outer limb.

Nope, with the shape being a pyramid limb, you want its bend to look exactly like an otherwise full pyramid bow woukd look like.
Tread softly and carry a bent stick.

Dont seek your happiness through the approval of others

Offline PatM

  • Member
  • Posts: 6,737
Re: Pyramid /Molle/ Thickness Question
« Reply #11 on: March 21, 2019, 12:12:12 pm »
Yeah, I was just wondering if the shape would change with the straight outer limb.

Nope, with the shape being a pyramid limb, you want its bend to look exactly like an otherwise full pyramid bow woukd look like.

 It has to bend more though, no?   The lever is not bending so something else needs to bend more.

Offline sleek

  • Member
  • Posts: 6,681
Re: Pyramid /Molle/ Thickness Question
« Reply #12 on: March 21, 2019, 12:30:22 pm »
Yeah, I was just wondering if the shape would change with the straight outer limb.

Nope, with the shape being a pyramid limb, you want its bend to look exactly like an otherwise full pyramid bow woukd look like.

 It has to bend more though, no?   The lever is not bending so something else needs to bend more.

Yes it bends more. But more than what? A lomger bow tip to tip? Yes. A shorter bow? Maybe not, and even shirter, probably not. But my point was, you dont make that happen by just making it thinner. And we have already gone into the thickness and width discussion.
Tread softly and carry a bent stick.

Dont seek your happiness through the approval of others

Offline DC

  • Member
  • Posts: 10,396
Re: Pyramid /Molle/ Thickness Question
« Reply #13 on: March 21, 2019, 12:36:46 pm »
I can see that it has to bend more. At least to get the draw length.