## Gravity Vehicle C

eab2114
Member
Posts: 5
Joined: November 19th, 2018, 6:28 am
Division: C
State: DC

### Re: Gravity Vehicle C

Hi! I made a vehicle with a wooden frame and a ramp with a wooden frame and curved plywood surface. However, the problem I'm continuing to encounter is that the steep angle of the ramp causes the dowel/front of the car to hit the ground before the wheels can get moving. Does anyone have ideas for making the transition from the ramp to the floor smoother in the limited space (50 cm) available? What about changing the front of the car in a way to prevent the dowel from hitting the floor first?

knightmoves
Member
Posts: 233
Joined: April 26th, 2018, 6:40 pm

### Re: Gravity Vehicle C

eab2114 wrote:
November 30th, 2019, 4:41 pm
Hi! I made a vehicle with a wooden frame and a ramp with a wooden frame and curved plywood surface. However, the problem I'm continuing to encounter is that the steep angle of the ramp causes the dowel/front of the car to hit the ground before the wheels can get moving. Does anyone have ideas for making the transition from the ramp to the floor smoother in the limited space (50 cm) available? What about changing the front of the car in a way to prevent the dowel from hitting the floor first?
Put the wheels as far forwards as you can - get the axles as close to the front of your car as possible. If you look at your car form the side, you want the bottom of the dowel to be hidden by the wheel - then it won't hit the ground.

Tendan
Member
Posts: 59
Joined: January 27th, 2019, 5:37 pm
Division: C
State: PA
Location: There

### Re: Gravity Vehicle C

knightmoves wrote:
December 3rd, 2019, 10:26 am
eab2114 wrote:
November 30th, 2019, 4:41 pm
Hi! I made a vehicle with a wooden frame and a ramp with a wooden frame and curved plywood surface. However, the problem I'm continuing to encounter is that the steep angle of the ramp causes the dowel/front of the car to hit the ground before the wheels can get moving. Does anyone have ideas for making the transition from the ramp to the floor smoother in the limited space (50 cm) available? What about changing the front of the car in a way to prevent the dowel from hitting the floor first?
Put the wheels as far forwards as you can - get the axles as close to the front of your car as possible. If you look at your car form the side, you want the bottom of the dowel to be hidden by the wheel - then it won't hit the ground.
You could also use larger wheels or a combination of the two.
2019 - 2020 Events
~ Boomilever
~ Circuit Lab
~ Detector Building
~ Gravity Vehicle
~ Machines

yugo
Member
Posts: 5
Joined: December 26th, 2019, 6:55 am
Division: C
State: NY

### Re: Gravity Vehicle C

Hi, hope the winter break is going well for everyone!

Due to an unfortunate designation of events by my coach, I have to work this event for the 2020 season, despite having little prior build event experience. I was scrolling through the forum, and I see that many people are saying ball bearings will be very efficient for this year's competition. May I ask why they would be so much more effective as opposed to normal axles, and how they are supposed to be utilized (e.g. how you attach them to the chassis, and how do you attach the wheels to them)?

Sorry if my questions are fairly amateurish, I primarily did lab and study events last year, so I am a bit concerned as to how well I can prepare for this.

xiangyu
Member
Posts: 220
Joined: April 6th, 2019, 8:32 pm
Division: C
State: MI
Location: Where you can't find me.

### Re: Gravity Vehicle C

yugo wrote:
December 26th, 2019, 7:07 am
Hi, hope the winter break is going well for everyone!

Due to an unfortunate designation of events by my coach, I have to work this event for the 2020 season, despite having little prior build event experience. I was scrolling through the forum, and I see that many people are saying ball bearings will be very efficient for this year's competition. May I ask why they would be so much more effective as opposed to normal axles, and how they are supposed to be utilized (e.g. how you attach them to the chassis, and how do you attach the wheels to them)?

Sorry if my questions are fairly amateurish, I primarily did lab and study events last year, so I am a bit concerned as to how well I can prepare for this.
Hello!

Welcome to the builder world. Hopefully you'll find that it's a lot of fun (between frustrations ) Ball bearings are used to reduce friction. It's essentially a wheel within a wheel that turns very smoothly. You would put a fitting axle through the inner circle and fix the outer circle in plalce on your vehicle. This way, when the axle turns, it won't be rubbing against the vehicle frame. The axle would have the wheels on it. (So essentially you still have the axle, the ball bearings are just an add on)

Watch this video by Mark Rober on Mousetrap Vehicles, it explains a lot of the basics for vehicle events like gravity vehicle (just skip all the mousetrap bits): https://youtu.be/b7zWwo9dbiU?t=398

Hope this helps let me know if you have questions.
Xiangyu
2020 Events: Wright Stuff, Gravity Vehicle. Circuit Lab, Boomilever, Ping-Pong Parachute, WIDI

Inv.1/Inv.2/Reg
WS: 4/1st /
WIDI: 13/2nd /
Boom: 1st/1st /
Circuit: 15/7 /
GV: - /5 /
PPP: - /6 /

Medal & Ribbon Count: 8
East Grand Rapids High School Team Captain

yugo
Member
Posts: 5
Joined: December 26th, 2019, 6:55 am
Division: C
State: NY

### Re: Gravity Vehicle C

xiangyu wrote:
December 26th, 2019, 8:17 am
yugo wrote:
December 26th, 2019, 7:07 am
Hi, hope the winter break is going well for everyone!

Due to an unfortunate designation of events by my coach, I have to work this event for the 2020 season, despite having little prior build event experience. I was scrolling through the forum, and I see that many people are saying ball bearings will be very efficient for this year's competition. May I ask why they would be so much more effective as opposed to normal axles, and how they are supposed to be utilized (e.g. how you attach them to the chassis, and how do you attach the wheels to them)?

Sorry if my questions are fairly amateurish, I primarily did lab and study events last year, so I am a bit concerned as to how well I can prepare for this.
Hello!

Welcome to the builder world. Hopefully you'll find that it's a lot of fun (between frustrations ) Ball bearings are used to reduce friction. It's essentially a wheel within a wheel that turns very smoothly. You would put a fitting axle through the inner circle and fix the outer circle in plalce on your vehicle. This way, when the axle turns, it won't be rubbing against the vehicle frame. The axle would have the wheels on it. (So essentially you still have the axle, the ball bearings are just an add on)

Watch this video by Mark Rober on Mousetrap Vehicles, it explains a lot of the basics for vehicle events like gravity vehicle (just skip all the mousetrap bits): https://youtu.be/b7zWwo9dbiU?t=398

Hope this helps let me know if you have questions.
Xiangyu
Thanks so much! Another thing I've seen here is the usage of BaneBots materials? I checked some of the wheels they had, and I am unfortunately a bit lost. Are the hubs basically the connectors of the wheel to the axles/chassis? And are there advantages between choosing the T40 over the T81, for example? Perhaps more significantly, should one use them over other forms of wheels?

xiangyu
Member
Posts: 220
Joined: April 6th, 2019, 8:32 pm
Division: C
State: MI
Location: Where you can't find me.

### Re: Gravity Vehicle C

yugo wrote:
December 27th, 2019, 4:56 pm

Thanks so much! Another thing I've seen here is the usage of BaneBots materials? I checked some of the wheels they had, and I am unfortunately a bit lost. Are the hubs basically the connectors of the wheel to the axles/chassis? And are there advantages between choosing the T40 over the T81, for example? Perhaps more significantly, should one use them over other forms of wheels?

Hello again,

I'll be honest and say that I don't have too much experience with banebot wheels and if someone else wants to chime in that will be great! (What is the difference between T40 and T81?)

You are correct, the hubs connect the wheels to the axle. It basically features a lock screw (which "locks" it to the axle) and a platform where the wheels "snap in".

I currently use the T40 wheels (Not for any particular reason) and they work pretty good. The only problem right now is that I am experiencing a slight skid on the left backwheel (my brake is placed on the right side) of about 1-2 cm when the vehicle stops.

Let me know if you have any questions and happy holidays.

Does anyone in the forums have ideas on how I can prevent that skid? I've tried spring methods but didn't like it as I am incapable of making sure I start counting at the same location (since springs aren't a "tight lock").

Xiangyu
2020 Events: Wright Stuff, Gravity Vehicle. Circuit Lab, Boomilever, Ping-Pong Parachute, WIDI

Inv.1/Inv.2/Reg
WS: 4/1st /
WIDI: 13/2nd /
Boom: 1st/1st /
Circuit: 15/7 /
GV: - /5 /
PPP: - /6 /

Medal & Ribbon Count: 8
East Grand Rapids High School Team Captain

PM2017
Member
Posts: 514
Joined: January 20th, 2017, 5:02 pm
State: CA
Location: Enjoying College! :D

### Re: Gravity Vehicle C

xiangyu wrote:
December 27th, 2019, 5:15 pm
yugo wrote:
December 27th, 2019, 4:56 pm

Thanks so much! Another thing I've seen here is the usage of BaneBots materials? I checked some of the wheels they had, and I am unfortunately a bit lost. Are the hubs basically the connectors of the wheel to the axles/chassis? And are there advantages between choosing the T40 over the T81, for example? Perhaps more significantly, should one use them over other forms of wheels?

Hello again,

I'll be honest and say that I don't have too much experience with banebot wheels and if someone else wants to chime in that will be great! (What is the difference between T40 and T81?)

You are correct, the hubs connect the wheels to the axle. It basically features a lock screw (which "locks" it to the axle) and a platform where the wheels "snap in".

I currently use the T40 wheels (Not for any particular reason) and they work pretty good. The only problem right now is that I am experiencing a slight skid on the left backwheel (my brake is placed on the right side) of about 1-2 cm when the vehicle stops.

Let me know if you have any questions and happy holidays.

Does anyone in the forums have ideas on how I can prevent that skid? I've tried spring methods but didn't like it as I am incapable of making sure I start counting at the same location (since springs aren't a "tight lock").

Xiangyu
T40 wheels are 0.4 inch thick, T81 are 0.8 inch thick. (So T81 wheels are significantly heavier.)

As for skid, probably the best way would simply be to simply account for that in your data, and use an empirical fit rather than an idealized model for your braking variables.

Also I missed post #500 but I finally hit that benchmark whooo!
West High '19
UC Berkeley '23

Go Bears!

yugo
Member
Posts: 5
Joined: December 26th, 2019, 6:55 am
Division: C
State: NY

### Re: Gravity Vehicle C

Hello everyone!

Another question: In order to create the threaded rod braking system, I presume the threaded rod would take the place of the axle in the vehicle. In that case, is it still possible to fit the ball bearings onto the threaded rod? And would all of this work with latex-layered CD wheels?

Thanks!

Yugo

xiangyu
Member
Posts: 220
Joined: April 6th, 2019, 8:32 pm
Division: C
State: MI
Location: Where you can't find me.

### Re: Gravity Vehicle C

yugo wrote:
December 28th, 2019, 4:11 pm
Hello everyone!

Another question: In order to create the threaded rod braking system, I presume the threaded rod would take the place of the axle in the vehicle. In that case, is it still possible to fit the ball bearings onto the threaded rod? And would all of this work with latex-layered CD wheels?

Thanks!

Yugo
Yes, the threaded rod would replace the axle. You should be able to find threaded rods with the diameter fitting to the bearing, which should work. As for CD's, typically people have adaptors to hook them to the axle. I don't use it so I'm not too familiar with it but I know some people 3d print their own adaptors or buy it somewhere online (Not sure where but others feel free to chime in).

Xiangyu
2020 Events: Wright Stuff, Gravity Vehicle. Circuit Lab, Boomilever, Ping-Pong Parachute, WIDI

Inv.1/Inv.2/Reg
WS: 4/1st /
WIDI: 13/2nd /
Boom: 1st/1st /
Circuit: 15/7 /
GV: - /5 /
PPP: - /6 /

Medal & Ribbon Count: 8
East Grand Rapids High School Team Captain

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