designing a catapult for physics class.

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M

MikeMike

Lifer
Feb 6, 2000
45,885
66
91
1kg weight limit
.5 meter arm length.
has to go over a 1.5m wall 3 m away.
cannot be a slingsot dsign.

i was thinking of making it a sidearm throw, as that would allow me to have the most pull back.

i will be using surgical tubing for my force to appl to my arm.

any hints???

MIKE
 
N

notfred

Lifer
Feb 12, 2001
38,241
4
0
If you can't make a slingshot that can shoot 10 feet over a 5 foot obstacle, you suck.
 
D

DrVos

Golden Member
Jan 31, 2002
1,085
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Make a trebuchet, its supposed to be one of the more powerful/efficient catapults out there.
 
H

Howard

Lifer
Oct 14, 1999
47,982
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81
Originally posted by: DrVos
Make a trebuchet, its supposed to be one of the more powerful/efficient catapults out there.
Click to expand...
I would recommend a trebuchet if it is allowed.
 
M

Martin

Lifer
Jan 15, 2000
29,178
1
81
Originally posted by: Howard
Originally posted by: DrVos
Make a trebuchet, its supposed to be one of the more powerful/efficient catapults out there.
Click to expand...
I would recommend a trebuchet if it is allowed.
Click to expand...

true, but I've never seen a trebuchet without a slingshot.

But I guess I could be done.
 
GagHalfrunt

GagHalfrunt

Lifer
Apr 19, 2001
25,284
1,997
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Given the short arm length, a trebuchet would likely not be the best design. That generates it's force from the length of the arc and is generally a heavy design. If you can use rubber bands like surgical tubing to apply the force a mangronel would be far more powerful.
 
A

AlienCraft

Lifer
Nov 23, 2002
10,539
0
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Originally posted by: GagHalfrunt
Given the short arm length, a trebuchet would likely not be the best design. That generates it's force from the length of the arc and is generally a heavy design. If you can use rubber bands like surgical tubing to apply the force a mangronel would be far more powerful.
Click to expand...
The arc is derived from the length of the sling, not the arm.

 
H

Howard

Lifer
Oct 14, 1999
47,982
10
81
Originally posted by: GagHalfrunt
Given the short arm length, a trebuchet would likely not be the best design. That generates it's force from the length of the arc and is generally a heavy design. If you can use rubber bands like surgical tubing to apply the force a mangronel would be far more powerful.
Click to expand...
You mean a mangonel?
 
A

AaronB

Golden Member
Dec 25, 2002
1,214
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Arm length, sling length. It doesn't matter. A trebuchet will be hampered by the weight limit.


A mangonel would be an excellent idea.

link to a "sort of" mangonel project.

I only consider the above to be a good example because it clearly shows how a mangonel works with the rubber bands
 
S

Spencer278

Diamond Member
Oct 11, 2002
3,637
0
0
Just build your standard counter catapult but instead of using a counter wait get like 30 CO2 cartigies set up 30 nails to punture the CO2 watch object go flying oh and try and minimize the angle that you shoot it at. The key to pointless physic class is to bend the rules so just put your .5m arm on top of a 10 foot base and you should be all set.
 
J

JRS4224

Senior member
Oct 2, 2003
204
0
0
When I made one in physics class I used wood and rubberbands used for planes that you get in a hobby store. The egg went way further then it had to go and I could just add or remove bands as I pleased.
 
C

ClueLis

Platinum Member
Jul 2, 2003
2,269
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I would go for the mangonel-type design. It's easy to build, and would have sufficient power for what you are describing.
 
W

WinkOsmosis

Banned
Sep 18, 2002
13,990
1
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Trebuchet? It's not like he's trying to lay siege to the White House.

Just put some springs on an arm and call it a day.
 
M

MikeMike

Lifer
Feb 6, 2000
45,885
66
91
yea, i just wanna set the record. record happens to be like 210ft.

would the sidearm, type lauch work? i would have to adjust for the spin of the ball no?

MIKE

 
B

BadgerFan

Member
Aug 4, 2003
132
0
0
I would say make it out of PVC piping, have the arm function as a spring, or see if the Home Depot has some kind of cheap torsion springs. If you use torsion springs you will have to figured out some kind of cheap bearing set up. Perhaps a peice of PVC inside another, with graphite lube.
 
R

RaynorWolfcastle

Diamond Member
Feb 8, 2001
8,968
16
81
I made a trebuchet for a physics class a couple of years back... it turns out that to properly model and optimize your design you have to know lagrangians (or was it hamiltonians). Either way you needed some pretty potent math/physics so our teacher just gave us a base design and told us to tweak it as best we could. That mostly involved messing with the counter weight/projectile weight/string length...

oh btw, you should definitely make it a trebuchet, it's pretty impressive how far it'll shoot something if properly balanced
 
M

MikeMike

Lifer
Feb 6, 2000
45,885
66
91
yea, but HOW THE HELL do i keep it under 2.2lbs!!!

and the lever arm can be no longer than .5 meters!!

MIKE
 
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