Author Topic: Wheels not moving on surface  (Read 494 times)

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Offline preetham1104Topic starter

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Wheels not moving on surface
« on: February 27, 2013, 04:35:58 AM »
The part in italics is not really important.. It is just the story of how the situation arose.

Hi,
       I don't know where to begin from. I am in grade 9, and recently, we had a working model competition. So me and my friend decided to build the 50$ robot for the competition, and we were all set for it. We filled in the form, and sent it. We started off be knowing as much as possible about robotics. Thanks to SOR and "Howstuffworks", I can say I learnt quite A LOT about electronics.We were informed  that we were selected for the working model comp. only 10 days before the competition was supposed to be held. Since we live in Bahrain, it is almost next to impossible to get parts here. So we decided to order it online from Amazon. But as you may have guessed, the parts usually take 20 days to reach the Middle East ("GENIUS" thinking by us  :P :D).. We didn't realize it would take so many days, so we kept waiting till 2 days before the comp. (Again, "GENIUS"  :D ) I must add that during the 8 days, we built the structure and decided to use CD's as wheels. Two days before the competition, we realized we were in big trouble as the parts showed no sign of reaching prior to the expected date. So, we decided that we would build a RC car. We contacted most of the shops, but most of the "Transmitters" and "receivers" were out of stock. So, we then decided to rip off the electronic part of a ready-made RC car.
(The competition got over a week back, and we didn't win. We didn't expect to, because some of the other models were spectacular)


We bought a normal kiddish RC car for around 3 BHD (or 10$), ripped off the cover, removed the electrical board etc. We didn't change anything. We placed it in the structure we had made out of cardboard, and somehow, put the DC induction motors on to a cardboard which we then stuck on 2 CD's. We did the same for both motors. (P.S: We removed the gears, and put the motors directly on to the 2 so-called wheels. We then tried it with the wheels suspended in air. It worked.  We then placed it on the ground. We encountered the following problems:

1. The structure collapsed the first few times, as I guess the attaching of the induction motor to the cardboard wasn't strong enough. We then made it stay with SuperGlue and Duct tape. (Because, you know, duct tape fixes everything  :P )
2. Then, when the structure was stable, we moved the transmitter in every possible direction, but the car refused to budge. It wouldn't even move a millimetre. When we lifted it and then tried moving the transmitter, the wheels would spin perfectly, and I must add, very fast. But on the surface, it wouldn't move.

We thought maybe the CD was too weak, we we added 2 more CD's to the wheel. Once again, movement in air but no movement on ground. The structure, I guess, weighs very little. As much as an empty blackberry box, I must say. We also tried putting two wheels in the front to balance it, but still, it wouldn't budge on the ground.  >:(

Please tell us where we messed up, and what would be more advisable as wheels for future projects?

Thanks a lot..

Offline enoon

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Re: Wheels not moving on surface
« Reply #1 on: February 27, 2013, 06:12:59 AM »
(P.S: We removed the gears, and put the motors directly on to the 2 so-called wheels. We then tried it with the wheels suspended in air. It worked.  We then placed it on the ground. We encountered the following problems:

That is your problem :)
By not using gears you get an extremely high speed but no torque... it spins in the air but it has no strenght to turn with a weight on it.
Put the gears back on! :)

Offline preetham1104Topic starter

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Re: Wheels not moving on surface
« Reply #2 on: February 28, 2013, 06:44:29 AM »
:D Oh okay.. So the purpose of the gear system is to provide torque? Well, at least I learnt something new from that!
Thanks a lot enoon!

Offline newInRobotics

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Re: Wheels not moving on surface
« Reply #3 on: February 28, 2013, 07:08:20 AM »
Purpose of gear system can be either to reduce RPM and increase torque or vice versa :)
"Computer games don't affect kids; I mean if Pac-Man affected us as kids, we'd all be running around in darkened rooms, munching magic pills and listening to repetitive electronic music." - Kristian W

Offline enoon

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Re: Wheels not moving on surface
« Reply #4 on: March 01, 2013, 11:57:07 AM »
:D Oh okay.. So the purpose of the gear system is to provide torque? Well, at least I learnt something new from that!
Thanks a lot enoon!
:)
That and what newInRobotics said!

 


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