Can a Reeling Motor Tow a Car Faster Using a Speed Reduction Arrangement?

[Paola Flores]

Hi!,
I just wanted to give you an update as a mean to say thank you because all your ideas were extremely helpful! I passed Thermodynamics thanks to this project, and I ended up working on it alone so the last few semester weeks were hell hahaha. Anyway, just in case any other student finds this thread and for everyone that has shared their opinion, the peltier efficiency was around 5%, I had to use dry ice in a aluminum container on top of a heat dissipator attached to the cold side of the peltier, and applied a temperature around 300^oC to the hot side, above that temperature they will surely pop. I used thermal insulation tape on the peltier sides to protect the internal glue from overheating and keep the heat transfer on the two main faces. Ended up getting like 3-4 V max with a 500 mA current, none of the motors I had ordered worked with such a small current so I went to an electric shop and bought an RC car motor that had its own small plastic gearing case and attached a plastic nylon reel to it to tow a small 100g laser cut car, I did not even try to go for the prize cause this was the only working design out of 3 failed attemps and I was fed up and sleep deprived on the presentation, but everything went well and just by reaching the top of the slope where the competition was held you had a full mark on your project, at the end no one really tried to win the competition cause it was much harder that expected and everyone was so done with this project, but I'm happy because I feel like I learned a lot.
Anyway, I just wanted to say thank you everyone for your opinions, here are some pictures of the parts I mentioned above.

https://ibb.co/deSbgU
https://ibb.co/kbLU1U
https://ibb.co/iBAq89

 

[NTL2009]

Thanks for the update. That tower of dry ice and large heat sink is impressive! I think you did very well to get 1~2 Watts out of that Peltier. I'm sure you learned a lot, as you were originally thinking of tens of watts and much larger motors.

These Peltiers seem so attractive at first glance: temperature delta in, electricity out! No moving parts! Small and light! How elegant!

But in practice, getting meaningful power out becomes quite involved. Congratulations on getting full marks on this!

I remember the first time I played around with a Peltier at a hobby level. I held it pinched between my fingers, applied power, and was thrilled that I immediately felt heat on one side, and cold on the other. That thrill dissipated as fast as the heat dissipated from one side to another through the junctions, and it just turned into a heater (in a second or two)! Yes, it takes a lot of attention to heat transfer on both sides to attain significant results.