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### Author Topic: climbing a slope  (Read 2339 times)

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#### junkman

• Jr. Member
• Posts: 14
##### climbing a slope
« on: March 08, 2011, 05:58:07 AM »
hi, I am making a robot for track race.But having some problems.
I am using 4 DC motors 12v 300 rpm and 2 kgcm torque  each (this one: http://www.vegarobokit.com/product_descriptions.aspx?product_id=74&sub_category_name=Gear%20Motors&category_id=41) and the whole robot is little less then 1 kg(1 kg is max weight allowed).

Now the problem.There is a 30 degree slope which the robot must climb. There is a plastic bag which is on stuck on the face of slope  using tape. Then a layer of oil is applied in the face of the bag making it slippery.
What happened? Well we took the max run up we could(about 1 foot) went at full speed but only made it 3/4 up, before our bot came down the slope.

I got to make some bot that turn and every thing and also climb slopes. I don't have much experience (its the first thing i made that moves) so i got some questions?
What is better 4 small motors and 3 wheels or 2 big motors and 2 wheels?
what better bot as lite as possible or bigger motors(which are more powerful but also weigh more)?
how balance speed and torque (it cant be slow but need to climb to slopes)
any other to help me win tips

the rules for race are 25cm*25cm*25cm max size, 1kg max weight, external power source will be provided(it means there is a 5 meter long wire going form robot to remote and the to dc adapted is no batteries )

#### dave239

• Beginner
• Posts: 3
##### Re: climbing a slope
« Reply #1 on: March 08, 2011, 08:50:53 AM »
Hi
Can you explain the slope requirement more fully.
It would be helpful to know the width of the slope and how much is covered by the plastic bag (in width and distance up the slope).
I was trying to get an idea of whether any wheel can be clear of the oil.
Also what material is the slope made from and is there anything in the track design to absorb the oil so that the rest of the track stays clean?

#### waltr

• Supreme Robot
• Posts: 1,944
##### Re: climbing a slope
« Reply #2 on: March 08, 2011, 08:54:43 AM »
Oh, that is a tough task. I can only think of two possible solutions:
1- use tires with more traction on a oily surface. Thinking Snow studs.
2- use motors that have a higher top speed. You did try hitting the ramp at top speed. how much more speed do you think might get the Bot up the ramp.

good luck and have fun

#### junkman

• Jr. Member
• Posts: 14
##### Re: climbing a slope
« Reply #3 on: March 08, 2011, 10:49:36 PM »
i didn't measure the slope exactly but it something like 50 cm at 30 degrees(I didn't take a ruler but it was as long as my hand or almost double the size of robot).Event heads clean the track between every team.

The main frame of track is made of wood and covered in black card paper(or at least feels like card paper)to make look like a road. There are some metal door handle converted into speed breakers,and a grass pit at th end.(I didn't reach this far in the track with my bot) basically a collage  is hosting the event and is using whatever they find(broken trolley wheels,scrap metal,bricks,etc) to make obstacles.
Quote from: waltr
1- use tires with more traction on a oily surface. Thinking Snow studs.
also i am using 4cm thick 5cm diameter tiers with rubber grip but will 2cm(thinner tiers) be better?(i read some where thiner tiers make bot go faster)My tires are flat(like f1 car tires), snow studs mean like tractor tires?
Quote from: waltr
2- use motors that have a higher top speed. You did try hitting the ramp at top speed. how much more speed do you think might get the Bot up the ramp.
i dont wana increase speed because it will mess up my turning. Track is about 35cm wide and car 25cm wide. Going out means i got to restart the races. Will higher torque help more then speed?

#### Soeren

• Supreme Robot
• Posts: 4,672
##### Re: climbing a slope
« Reply #4 on: March 09, 2011, 12:19:42 AM »
Hi,

Slightly spiked tires should do.
Spikes made from either hardened steel or better wolfram (tungsten carbide).

A single wheel that you can lower at the back of the 'bot, with these spikes on it, should be able to penetrate both the oil and the plastic and grab the wood that probably is beneath it.

A servo can be used to lower and raise the wheel.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Engineering is based on numbers - not adjectives

#### garrettg84

• Robot Overlord
• Posts: 187