Hovercraft B/C

[Ashernoel]

What are the tracks for hover like supposed to be like? On hard wood surface, perfect flat metal, or a regular lab table?

At my last tournament it was on a curvy lab table with a big bump in the middle, and I don't think that's how it should be.. impossible to calibrate and test for because the hover literally slowed down to a snails pace in the trough..

[Adi1008]

What are the tracks for hover like supposed to be like? On hard wood surface, perfect flat metal, or a regular lab table?

At my last tournament it was on a curvy lab table with a big bump in the middle, and I don't think that's how it should be.. impossible to calibrate and test for because the hover literally slowed down to a snails pace in the trough..

I don't think there's a standard track or anything. I've seen it be on plastic tables, floors, lab tables, tables pushed together, etc. MIT had it on these really fancy, well-made metal tracks. It would be really nice if there was a standard track, but I think it would make it much tougher for people running the events. I'd expect a metal track to be quite heavy and unwieldy, and it's unreasonable to expect every proctor to be able to build something like the track at MIT.

I also agree that calibrating for Hovercraft is really tough, at least for me. My calibrations never help at all during a competition because the surfaces vary so much (or have bumps, vary in width, span multiple surfaces, etc) and friction/balance play such a huge role.

[Adi1008]

[accidental double post]

[Ashernoel]

What are the tracks for hover like supposed to be like? On hard wood surface, perfect flat metal, or a regular lab table?

At my last tournament it was on a curvy lab table with a big bump in the middle, and I don't think that's how it should be.. impossible to calibrate and test for because the hover literally slowed down to a snails pace in the trough..

I don't think there's a standard track or anything. I've seen it be on plastic tables, floors, lab tables, tables pushed together, etc. MIT had it on these really fancy, well-made metal tracks. It would be really nice if there was a standard track, but I think it would make it much tougher for people running the events. I'd expect a metal track to be quite heavy and unwieldy, and it's unreasonable to expect every proctor to be able to build something like the track at MIT.

I also agree that calibrating for Hovercraft is really tough, at least for me. My calibrations never help at all during a competition because the surfaces vary so much (or have bumps, vary in width, span multiple surfaces, etc) and friction/balance play such a huge role.

That makes a lot of sense. Mass score is easy to prepare for, but it seems time score it a toss up. Teams try to get within the vicinity in their two runs. Using their first run as a baseline, they get one chance to adjust it for their final run. I guess the best preparation would just be to have a reliable way to change speed, and then hope you get lucky on the timing of the run.

[Zioly]

What are the tracks for hover like supposed to be like? On hard wood surface, perfect flat metal, or a regular lab table?

At my last tournament it was on a curvy lab table with a big bump in the middle, and I don't think that's how it should be.. impossible to calibrate and test for because the hover literally slowed down to a snails pace in the trough..

I don't think there's a standard track or anything. I've seen it be on plastic tables, floors, lab tables, tables pushed together, etc. MIT had it on these really fancy, well-made metal tracks. It would be really nice if there was a standard track, but I think it would make it much tougher for people running the events. I'd expect a metal track to be quite heavy and unwieldy, and it's unreasonable to expect every proctor to be able to build something like the track at MIT.

I also agree that calibrating for Hovercraft is really tough, at least for me. My calibrations never help at all during a competition because the surfaces vary so much (or have bumps, vary in width, span multiple surfaces, etc) and friction/balance play such a huge role.

That makes a lot of sense. Mass score is easy to prepare for, but it seems time score it a toss up. Teams try to get within the vicinity in their two runs. Using their first run as a baseline, they get one chance to adjust it for their final run. I guess the best preparation would just be to have a reliable way to change speed, and then hope you get lucky on the timing of the run.

Agreed. I guess for this event, it's not so much as having pre-determined numbers that correspond with certain lengths or times (example: scrambler, air trajectory), but rather having a really good "feeling" for your device. It's definitely more variable than other build events, but it's definitely a challenge nonetheless.

[Tesel]

So I'm aware that I'm asking all these questions far too late in the season, the original plan was to have another teammate build and have me test.

However, I'd like to help out with revising our build since we have had problems with changing speed and with levitation.
Does anyone know the necessary specs of a lift blower fan that would work with a hovercraft for SciOly?
Also, how do you recommend changing speed? We've tried a slide resistor and a bad potentiometer with almost no success.

[antoine_ego]

So I'm aware that I'm asking all these questions far too late in the season, the original plan was to have another teammate build and have me test.

However, I'd like to help out with revising our build since we have had problems with changing speed and with levitation.
Does anyone know the necessary specs of a lift blower fan that would work with a hovercraft for SciOly?
Also, how do you recommend changing speed? We've tried a slide resistor and a bad potentiometer with almost no success.

I'm not qualified to talk about blower fans, but as for standard computer fans, if you're aiming for maximum weight, you want at least 800 Pacals of static pressure with at least 120cfm. For changing speed, I'm not going to disclose my method, but I've seen successful designs that involve just slapping a resistor on the back fan. A good potentiometer could work, assuming you got one that could handle the current draws of your fan starting up.

[Tesel]

So I'm aware that I'm asking all these questions far too late in the season, the original plan was to have another teammate build and have me test.

However, I'd like to help out with revising our build since we have had problems with changing speed and with levitation.
Does anyone know the necessary specs of a lift blower fan that would work with a hovercraft for SciOly?
Also, how do you recommend changing speed? We've tried a slide resistor and a bad potentiometer with almost no success.

I'm not qualified to talk about blower fans, but as for standard computer fans, if you're aiming for maximum weight, you want at least 800 Pacals of static pressure with at least 120cfm. For changing speed, I'm not going to disclose my method, but I've seen successful designs that involve just slapping a resistor on the back fan. A good potentiometer could work, assuming you got one that could handle the current draws of your fan starting up.

That's fine, I don't expect everyone to share all the important details about changing speed since there's so many ways to do that.
I'm intrigued by the idea of just swapping out resistors, sounds simple and replaceable and not as likely to fail.

[TechCoach]

What is the part number of the motor from digi-key that suffice? We have been there and must have missed that.

Here is the link: http://www.digikey.com/product-detail/e ... ND/2560506

That is a really good looking blower! Specs are definitely above the requirement

Hello,

We have this blower for lift and a small hobby motor mounted propeller for thrust. The blower is on 8.4 v NiMH battery. We are having trouble reducing the speed. We tried a few different wind tunnels, mesh, flaps and weights placement. Our craft is 2 Kg. The lift seems to be so powerful that a tiny thrust is enough and difficult to adjust. We have burnt one POT so a bit hesitant to use it again. Are there any other ideas to bring down speed? Thanks.

[Tesel]

OK, so now I'm confused.
Are the specs different for a blower fan and for just a normal fan?
Right now our team has picked out two options:
http://www.digikey.com/product-detail/e ... ND/2560583
and
http://www.digikey.com/product-detail/e ... ND/2560506
Which would be better for lift?
From what I see, the first is close to not enough CFM, while the second one is close to not enough Pa.
Would one be recommended over the other?
I ask just because these are expensive fans and I don't want to spend too much.

Also, anyone know of any 120mm fan grills that would definitely meet the spacing requirements?