## Center of mass shifting wingnuts

christian3624
Member
Posts: 2
Joined: February 10th, 2020, 5:42 am
Division: C
State: NY
Has thanked: 0
Been thanked: 0

### Center of mass shifting wingnuts

Hello possible opponents,

On my gravity vehicle, there is a braking system that relies on two 3/8" wingnuts traveling to the right on two threaded screws. This seems to make the gravity vehicle turn to the right by shifting its center of mass to the extent that when it reaches twelve meters it's off by a whole meter.

I am open to any suggestions about how I can fix this. Currently, we have a 500-gram weight on the left side of the vehicle to counteract the weight of the wingnuts which seems to work but requires that we make the vehicle slightly off from level on the ramp compared to the ground.

MTV<=>Operator
Member
Posts: 137
Joined: February 8th, 2019, 12:41 pm
Division: C
State: NY
Has thanked: 8 times
Been thanked: 4 times

### Re: Center of mass shifting wingnuts

Hello possible opponents,
Definite opponent if you are in New York
christian3624 wrote:
February 11th, 2020, 6:38 pm
On my gravity vehicle, there is a braking system that relies on two 3/8" wingnuts traveling to the right on two threaded screws. This seems to make the gravity vehicle turn to the right by shifting its center of mass to the extent that when it reaches twelve meters it's off by a whole meter.

I am open to any suggestions about how I can fix this. Currently, we have a 500-gram weight on the left side of the vehicle to counteract the weight of the wingnuts which seems to work but requires that we make the vehicle slightly off from level on the ramp compared to the ground.
I seriously doubt that the moving of two small wingnuts from one side of the vehicle to the other could possible shift the center of mass enough to make it curve. It's possible your vehicle may be curving because the axles aren't exactly parallel. Try pushing the right side of the front axle forwards or the right side of the back axle backwards with respect to the vehicle. If possible, use a caliper to make sure you have the same spacing between your axles on either side of the car. What wheels are you using? Increasing traction should keep it on a straighter path as well. Also, make sure you have enough mass over each axle. Having all the mass concentrated over one axle will cause the other one to be more unstable linearly.
THHS '21 Builder Cult Member
2017-2018: Mousetrap, Hovercraft, Towers
2018-2019: Mousetrap (8th regional), Boomilever (3rd regional), Wright Stuff
2020 Events/YUSO/regional
Gravity Vehicle/9/5
Detector Building/8/7
Wright Stuff/--/10
Ping Pong Parachute/--/--

christian3624
Member
Posts: 2
Joined: February 10th, 2020, 5:42 am
Division: C
State: NY
Has thanked: 0
Been thanked: 0

### Re: Center of mass shifting wingnuts

MTV<=>Operator wrote:
February 11th, 2020, 7:04 pm
Hello possible opponents,
Definite opponent if you are in New York
christian3624 wrote:
February 11th, 2020, 6:38 pm
On my gravity vehicle, there is a braking system that relies on two 3/8" wingnuts traveling to the right on two threaded screws. This seems to make the gravity vehicle turn to the right by shifting its center of mass to the extent that when it reaches twelve meters it's off by a whole meter.

I am open to any suggestions about how I can fix this. Currently, we have a 500-gram weight on the left side of the vehicle to counteract the weight of the wingnuts which seems to work but requires that we make the vehicle slightly off from level on the ramp compared to the ground.
I seriously doubt that the moving of two small wingnuts from one side of the vehicle to the other could possible shift the center of mass enough to make it curve. It's possible your vehicle may be curving because the axles aren't exactly parallel. Try pushing the right side of the front axle forwards or the right side of the back axle backwards with respect to the vehicle. If possible, use a caliper to make sure you have the same spacing between your axles on either side of the car. What wheels are you using? Increasing traction should keep it on a straighter path as well. Also, make sure you have enough mass over each axle. Having all the mass concentrated over one axle will cause the other one to be more unstable linearly.
Your probably correct in saying that the wing nuts don't weigh enough to effect the vehicle. As the vehicle is currently at my school I can't make adjustments right now.
As far as the wheels are concerned, we're using the banebots T81 4-7/8 in blue wheels.
The wheel base is about 5 in width the whole vehicle is only 12 in length.

What has dumbfounded me is that consistently for almost every run, before about 7 - 8 meters the vehicle goes straight, but then after 7 meters it decided to veer off in either direction. But when the vehicle is adjusted on the ramp in the opposite direction as the veering, the vehicle seems to go straight, except the next day when I do the exact same thing as the run where it worked, it decides to turn again.

MTV<=>Operator
Member
Posts: 137
Joined: February 8th, 2019, 12:41 pm
Division: C
State: NY
Has thanked: 8 times
Been thanked: 4 times

### Re: Center of mass shifting wingnuts

christian3624 wrote:
February 11th, 2020, 8:09 pm
MTV<=>Operator wrote:
February 11th, 2020, 7:04 pm
Hello possible opponents,
Definite opponent if you are in New York
christian3624 wrote:
February 11th, 2020, 6:38 pm
On my gravity vehicle, there is a braking system that relies on two 3/8" wingnuts traveling to the right on two threaded screws. This seems to make the gravity vehicle turn to the right by shifting its center of mass to the extent that when it reaches twelve meters it's off by a whole meter.

I am open to any suggestions about how I can fix this. Currently, we have a 500-gram weight on the left side of the vehicle to counteract the weight of the wingnuts which seems to work but requires that we make the vehicle slightly off from level on the ramp compared to the ground.
I seriously doubt that the moving of two small wingnuts from one side of the vehicle to the other could possible shift the center of mass enough to make it curve. It's possible your vehicle may be curving because the axles aren't exactly parallel. Try pushing the right side of the front axle forwards or the right side of the back axle backwards with respect to the vehicle. If possible, use a caliper to make sure you have the same spacing between your axles on either side of the car. What wheels are you using? Increasing traction should keep it on a straighter path as well. Also, make sure you have enough mass over each axle. Having all the mass concentrated over one axle will cause the other one to be more unstable linearly.
Your probably correct in saying that the wing nuts don't weigh enough to effect the vehicle. As the vehicle is currently at my school I can't make adjustments right now.
As far as the wheels are concerned, we're using the banebots T81 4-7/8 in blue wheels.
The wheel base is about 5 in width the whole vehicle is only 12 in length.

What has dumbfounded me is that consistently for almost every run, before about 7 - 8 meters the vehicle goes straight, but then after 7 meters it decided to veer off in either direction. But when the vehicle is adjusted on the ramp in the opposite direction as the veering, the vehicle seems to go straight, except the next day when I do the exact same thing as the run where it worked, it decides to turn again.
I'm not sure what is causing that inconsistency, it could be the floor. You definitely want to increase your wheelbase though, that will certainly decrease the curving. If possible I would double it to 10 in. The shorter the wheelbase is, the more the path of the vehicle will be affected by a small inaccuracy in the ramp, floor, etc.
THHS '21 Builder Cult Member
2017-2018: Mousetrap, Hovercraft, Towers
2018-2019: Mousetrap (8th regional), Boomilever (3rd regional), Wright Stuff
2020 Events/YUSO/regional
Gravity Vehicle/9/5
Detector Building/8/7
Wright Stuff/--/10
Ping Pong Parachute/--/--

### Who is online

Users browsing this forum: No registered users and 1 guest