Hovercraft B/C

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rc2000
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Re: Hovercraft B/C

Postby rc2000 » Wed Feb 14, 2018 6:07 am

Would anyone mind recommending me some DC motors & props for lift. I've really been struggling with it. For thrust I plan on using a computer fan.

Also: Im using 2 of these https://www.amazon.com/1600mAh-Battery- ... +volt+nimh to power my hovercraft. Any tips on connecting them?

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Re: Hovercraft B/C

Postby kinghong1970 » Wed Feb 14, 2018 12:43 pm

search amazon for mini tamiya connector male

or cut the connector and solder

https://www.amazon.com/s/ref=nb_sb_noss ... ector+male

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Re: Hovercraft B/C

Postby RestingDoll » Wed Feb 14, 2018 12:59 pm

jajefan wrote:
nicholasmaurer wrote:
RestingDoll wrote:
The issue is that nothing in the problem indicates that Poiseuille Equation should be applied (viscosity, laminar flow, etc).


I think that is a fair criticism. The ES agreed he should have given more information to indicate the Poiseuille equation was needed. I think his assumption was that most pipes meet the requirements of using Poiseuille: they are reasonably long and not so wide as to generate turbulent flow.


I know this isn't the place to get clarifications, but are the tests allowed to test content not specifically listed in the rules manual? My concern arises from the fact that under rule 4. b. iv. Fluid Mechanics (Div C), Puiseuille's equation is not listed as a topic. It would be good to know for future competitions, as my team did not prepare adequately for topics outside of those listed for the invitational.


The listed topics are more of a guide rather than a strict set of what can and cannot be tested; even so, I would consider Poiseuille to be a subtopic in viscosity.

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Re: Hovercraft B/C

Postby reed303 » Wed Feb 14, 2018 1:38 pm

kinghong1970 wrote:search amazon for mini tamiya connector male

or cut the connector and solder

https://www.amazon.com/s/ref=nb_sb_noss ... ector+male


For those who might be unfamiliar or unable to solder wires, "wire nut" connectors like these are useful
https://www.lowes.com/pd/Utilitech-25-P ... /999953854
Strip off about 3/8" of insulation , and twist the wires together with the connector. The gray or blue size should work for most hovercraft wiring. They also make re-wiring very easy.
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Jake R
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Re: Hovercraft B/C

Postby Jake R » Fri Feb 16, 2018 6:07 am

I know that you need a high static pressure for lift fans, but does cfm matter for list as well? for example, i found this one that i might use https://www.digikey.com/product-detail/ ... ND/5230580 is that a good choice for lift? (max load)
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Re: Hovercraft B/C

Postby QuantumEcho » Sat Feb 17, 2018 6:53 pm

Does anyone know how long on average it takes for a SOINC.org FAQ to be answered?
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Re: Hovercraft B/C

Postby geniusjohn5 » Sat Feb 17, 2018 10:54 pm

Jake R wrote:I know that you need a high static pressure for lift fans, but does cfm matter for list as well? for example, i found this one that i might use https://www.digikey.com/product-detail/ ... ND/5230580 is that a good choice for lift? (max load)


CFM barely matters compared to static pressure when it comes to lift fans. Taking a look at the fan you provided in the link, I think that fan looks effective.
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Re: Hovercraft B/C

Postby LittyWap » Sat Feb 17, 2018 11:29 pm

Hey all,

I was wondering if anyone had any fluid mechanics/Div C practice tests. I was less than satisfied with mine and my partner’s performance at a recent tournament despite having the best build score, (16.89s, 16 rolls). Does anyone have any tests from fargone tournaments; your Physics II homework, anything at all?! I need to really power wash the cobwebs out of my brain.
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Re: Hovercraft B/C

Postby Adi1008 » Sun Feb 18, 2018 12:25 am

LittyWap wrote:Hey all,

I was wondering if anyone had any fluid mechanics/Div C practice tests. I was less than satisfied with mine and my partner’s performance at a recent tournament despite having the best build score, (16.89s, 16 rolls). Does anyone have any tests from fargone tournaments; your Physics II homework, anything at all?! I need to really power wash the cobwebs out of my brain.

You could probably find solid fluid mechanics questions in any introductory physics textbook, like Giancoli or Halliday and Resnick
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Re: Hovercraft B/C

Postby IvanGe » Sun Feb 18, 2018 1:40 am

QuantumEcho wrote:
Does anyone know how long on average it takes for a SOINC.org FAQ to be answered?


it takes a while but if it's over a couple weeks then your question was probably discarded.
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Re: Hovercraft B/C

Postby geniusjohn5 » Sun Feb 18, 2018 2:24 pm

What affects the effectiveness of a fan more? Amperage or Voltage? I'm deciding between a 1600 mah 8.4 nimh battery and a 3000 mah 8.4 nimh battery.
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Re: Hovercraft B/C

Postby dmis » Sun Feb 18, 2018 3:42 pm

geniusjohn5 wrote:What affects the effectiveness of a fan more? Amperage or Voltage? I'm deciding between a 1600 mah 8.4 nimh battery and a 3000 mah 8.4 nimh battery.


Oh boy... I think you have a bit of a misunderstanding of both of those concepts. Both current (amperage) and voltage will have an effect on the effectiveness of the fan, but the current through the fan is not really dependent on the capacity (amount of energy of the battery). Notice that when you mention the "amperage" of each battery there is an h after the ma. That means miliamp hours. The addition of the hours to the unit changes the meaning of the term. The battery with the 3000 mah will run longer before needing to be recharged, while the 1600 will run out faster. The 3000 may also be slightly faster/more powerful, due to the lower internal resistance of the battery. I would assume those effects to be largely negligible, unless the fan you have is rated for a lot of current (more than 5A).

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Re: Hovercraft B/C

Postby MattChina » Sun Feb 18, 2018 6:00 pm

rc2000 wrote:Would anyone mind recommending me some DC motors & props for lift. I've really been struggling with it. For thrust I plan on using a computer fan.

Also: Im using 2 of these https://www.amazon.com/1600mAh-Battery- ... +volt+nimh to power my hovercraft. Any tips on connecting them?

I would just buy connectors and solder them to the fan. I think its better not to solder anything directly to the battery.
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Re: Hovercraft B/C

Postby geniusjohn5 » Sun Feb 18, 2018 7:42 pm

Can anybody provide a link for connectors? I'm trying to find a way to connect the 8.4 v NiMH battery pack to the rest of my circuit.
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Re: Hovercraft B/C

Postby dmis » Sun Feb 18, 2018 7:55 pm

geniusjohn5 wrote:Can anybody provide a link for connectors? I'm trying to find a way to connect the 8.4 v NiMH battery pack to the rest of my circuit.


There are tons of different types, each with advantages and disadvantages. Amazon, ebay, hobbyking, other hobby shops, etc. Some examples to look up are xt60, turnigy connectors (or mini-turnigy connectors) banana plugs, or Dean's connectors. You could also use quick connect crimp terminals.


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