Author Topic: The Thin Axle problem  (Read 8664 times)

Offline popcorn537

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The Thin Axle problem
« on: October 22, 2015, 08:01:44 pm »
A major problem facing design of high load dynamic k'nex structures is the the fact that our axles for load-bearing wheels is limited to a quarter inch or so. I am aware that there are some custom pieces made out of materials stronger than ABS plastic floating around, which I have.


However, I'm wondering if anyone has developed some sort of multi-axle mechanism that could hold a greater weight and transmit a greater torque to a given rotating element? This problem has bugged me for quite a while.

Offline mathsboy314

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Re: The Thin Axle problem
« Reply #1 on: October 22, 2015, 11:24:50 pm »
As you probably know, there are tan rods (red rod size) and black rods (grey rod size) which are stronger than their normal size piece.
http://www.knex.com/shop/16437/tan-rod-5-18in/
http://www.knex.com/shop/16231/stard-black-rod-7-12in/

I don't completely understand your question, but Austron has developed an automatic variable transmission gearbox that changes speed depending on torque.
https://www.youtube.com/watch?v=MYgnVh9PYrc

Offline popcorn537

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Re: The Thin Axle problem
« Reply #2 on: October 23, 2015, 03:15:06 am »
Imagine trying to hold the spinning 6 foot ferris wheel from one side, only using standard pieces, and without just supporting it with rollers on the bottom.

Offline Sorunome

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Re: The Thin Axle problem
« Reply #3 on: October 23, 2015, 09:29:43 am »
The only real thing you can do is either get that metal rod from that huge knex Ferris wheel set, or use the tan rod/black rod and design your model in a way so that where you attach the wheel to the axle it is very close to where you support it to the main model, resulting in a better distributed force.
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Offline mathsboy314

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Re: The Thin Axle problem
« Reply #4 on: October 27, 2015, 06:14:06 am »
Do you have any friends who have access to a 3D printer?

Offline popcorn537

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Re: The Thin Axle problem
« Reply #5 on: October 27, 2015, 04:35:51 pm »
I have one. Do you have a custom part idea to approach this?

Offline mathsboy314

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Re: The Thin Axle problem
« Reply #6 on: October 28, 2015, 11:34:46 am »
I suppose you could print a thicker rod and some custom connectors and gears to fit on it?

Offline Linkin_J_Knex

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Re: The Thin Axle problem
« Reply #7 on: February 06, 2016, 12:19:36 pm »
can't you use the metal rod from the 6 ft ferris wheel, or use rollers at the bottom to spin the build?
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Offline Sorunome

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Re: The Thin Axle problem
« Reply #8 on: February 11, 2016, 10:30:21 am »
Yes, you could, but many people don't have that set, and thus that rod. For those interested, you could actually pick up any metal rod from your local hardware store, just make sure it'll fit your knex pieces!

Using rollers to spin it has also been done a few times already, I think, don't know any model out of the top of my head right now, though.
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Offline mathsboy314

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Re: The Thin Axle problem
« Reply #9 on: February 12, 2016, 05:50:11 am »
Quote
Using rollers to spin it has also been done a few times already
An example of this is Sorunome's Ring lift.

Offline Linkin_J_Knex

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Re: The Thin Axle problem
« Reply #10 on: February 12, 2016, 01:47:55 pm »
Yeah i don't have the 6 foot ferris wheel either. I don't have many k'nex sets, only a mismatch of pieces. over time ive got loads tho. I wish i could afford the original knex coasters or ball machines.
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Offline Sorunome

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Re: The Thin Axle problem
« Reply #11 on: February 12, 2016, 04:39:57 pm »
Yeah i don't have the 6 foot ferris wheel either. I don't have many k'nex sets, only a mismatch of pieces. over time ive got loads tho. I wish i could afford the original knex coasters or ball machines.
The original roller coaster isn't that much, you can get it for like 20€ on ebay.
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Offline Linkin_J_Knex

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Re: The Thin Axle problem
« Reply #12 on: February 14, 2016, 04:42:38 pm »
i suppose there are some cheaper and more accessible sets, i just cant buy too much at the moment. i'm saving up money.
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Offline Paul sterling

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Re: The Thin Axle problem
« Reply #13 on: May 06, 2016, 12:51:54 pm »
Hi Gents,

as an idea (or a set of guidelines) as to making a mechanism as strong as possible.

maybe try this

avoiding cantilevers (a shaft supported at just one end)

keep unsupported shafts/lengths to a minimum

transfer loading from the up and down direction into the horizontal direction (and thus take tension loads into compression, where K'nex is very strong)

At Corus, double stacked rollers were popular for rolling extremely heavy steel sections, but for everything else, single stack two deck rollers were quite suffice.

also, efficient beam design, where supported by two points, dictates that the beam is subject to greater bending moment towards its centre, so the beam should be deeper and stronger in the middle, yet smaller and lighter towards the ends. gantry cranes of high tonnage usually show this.

hope this helps.

Paul.

Offline Linkin_J_Knex

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Re: The Thin Axle problem
« Reply #14 on: May 06, 2016, 05:03:30 pm »
 :o

I think i can decipher most of that to teenager English. When i grow up i want to know all the engineering and technical stuff XD
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