Scrambler B

[SluffAndRuff]

Thanks for the answer to my previous question.

So I was reading the rules and Rule 2.a. states that "the entire Scrambler, including the egg, must not exceed 0.90 m in any dimension."

My understanding is that the distance between any two points of the entire device must be less than 0.90 m, so diagonals count. However others I have talked to think that this means the Scrambler needs to fit in a 0.90 m cube, so only the height, width, and length dimensions count.

What's your understanding of this rule? Thanks!

[bernard]

All,

From where are you buying supplies? are you going to regular hardware stores or any specific stores?

For some parts of your device you may also find yourself finding more relevant materials at local or online hobby shops. Home improvement stores like Home Depot are great for wood for your launcher (if that's what you choose to use) but it can be too bulky for the vehicle. And I don't think I had any luck finding wheels that matched my needs there. I've heard of competitors using BaneBots wheels, Servocity wheels, 3D printing them, or laser cutting them. If you order online, just remember to do it early since shipping can take time.

For your dimension question--I think you should submit an FAQ for this. A lot of the events deal with cubes or heights and widths, so it's natural to immediately think of 90 cm x 90 cm but your point about diagonals counting seems to be possible too.

[dragon-fruit35]

All,

From where are you buying supplies? are you going to regular hardware stores or any specific stores?

Regular Hardware store such as Home depot

Home Depot and Lowes ftw! You can find most everything you need at normal hardware stores, and some things you don't need .

[chalker]

Thanks for the answer to my previous question.

So I was reading the rules and Rule 2.a. states that "the entire Scrambler, including the egg, must not exceed 0.90 m in any dimension."

My understanding is that the distance between any two points of the entire device must be less than 0.90 m, so diagonals count. However others I have talked to think that this means the Scrambler needs to fit in a 0.90 m cube, so only the height, width, and length dimensions count.

What's your understanding of this rule? Thanks!

I think you might have caught an error. Generally we would say something like the device should fit inside a 0.90 x 0.90 x 0.90 m cube, but I think there was an attempt to save some space / make it easier to read with the language you cite. I'm pretty sure the intention is still a .90 m cube, but I'll have to discuss with the committee.

[SluffAndRuff]

Okay, cool. I asked my coach to submit a FAQ as well.

Sorry for having so many questions, but after repeatedly analyzing the spring launcher diagram on the wiki (http://scioly.org/wiki/images/5/5c/SC-s ... pediag.gif) I still don't understand how to construct the locking mechanisms. My thought is some sort of rod that slips into a loop along the rubber band, but I have no idea how to execute this or how it will work.

Alternatively, I tried building a system like this one (http://scioly.org/wiki/images/6/63/SC-Nickfastswim.gif) but when I built the bar that holds the transport vehicle in place, the rubber band is too strong and pulls the car before the mass lowers all the way. When I tried making the bar grab the vehicle better, it won't let the car go even when the mass hits it...

For those of you who have built successful spring launchers, can you explain what I'm doing wrong and other possible locking mechanisms? Thanks.

[fishman100]

Okay, cool. I asked my coach to submit a FAQ as well.

Sorry for having so many questions, but after repeatedly analyzing the spring launcher diagram on the wiki (http://scioly.org/wiki/images/5/5c/SC-s ... pediag.gif) I still don't understand how to construct the locking mechanisms. My thought is some sort of rod that slips into a loop along the rubber band, but I have no idea how to execute this or how it will work.

Alternatively, I tried building a system like this one (http://scioly.org/wiki/images/6/63/SC-Nickfastswim.gif) but when I built the bar that holds the transport vehicle in place, the rubber band is too strong and pulls the car before the mass lowers all the way. When I tried making the bar grab the vehicle better, it won't let the car go even when the mass hits it...

For those of you who have built successful spring launchers, can you explain what I'm doing wrong and other possible locking mechanisms? Thanks.

Last year, we used a spring launcher very similar to this one:https://www.youtube.com/watch?v=HKisLACH9fU

We didn't have any bars running underneath the vehicle; the string connecting the back of our vehicle to the pulley at the front of the launcher was parallel to the top of the vehicle--in fact, the string essentially grazed the top of the car as it accelerated. This method works if and only if the string is parallel; if it's not, the string will pull the car upwards upon release and the car will skid/lose energy/not follow a straight path/etc. when it exits the launcher.

Our locking mechanism consisted of a PVC elbow which hooked onto a vertical nail in the back of our car. During setup, we would place the end of the string (which had a loop at the end) on the nail, and then we would lower the PVC elbow onto the nail. The PVC elbow was attached to a PVC pipe, which we used as a lever. On the other side of the PVC pipe, we attached a wooden plate for the mass to hit when we released it. When the mass hit the wooden plate, the lever lifted up on the end attached to the vehicle and thus released it without the need for a complex bar/rail system locking mechanism.

We averaged ~1.6s to 9m.

I can explain in more detail (hopefully), and so can Bernard--he helped me design a significant portion of my launcher. Unfortunately, I don't have any pics and we disassembled the device after Nats, but I do have a few pics of an earlier design (still a spring launcher) somewhere on my computer.

Finally, if the rubber bands are pulling the car prematurely, try reducing the amount of rubber you use. You'd be surprised at how little rubber you actually need to attain a sub-2s time.

[bernard]

Adding onto fishman100's comments (http://scioly.org/phpBB3/viewtopic.php? ... 19#p284965) but I don't want to quote everything...

Here's another angle to the same device fishman100 linked above: https://www.youtube.com/watch?v=vvgHKscFOyA. The spring mechanism of the launcher is too quick to see; at the rear of the vehicle there's was a loop of fishing line, which an archery release held onto. As the mass falls, it stretches the elastic, connected to a loop of fishing line attached to a vertical dowel on the vehicle. Vertical dowel is keep the loop parallel to the ground, otherwise upon release from the launcher it would probably jerk up. In the video I've just linked, you'll see two eye bolts towards the front of the launcher; the attachment of the fishing line loop to the vertical dowel was at this height. And it wasn't much of an attachment, just a notch cut into the dowel using a hacksaw. I didn't have any problems with the loop detaching before the mass was released.

As the mass is released, the elastic is stretched (you'll want the right length of elastic, which you'll get through trial and error). Finally when the mass is just about to hit the floor, it hits a string attached to the trigger of the archery release, releasing the car from the launcher. (I made the mistake of using elastic here instead of string--so at the tournament it decided to stretch instead of release the vehicle. You've been warned so you can't make the same mistake!)

Some additional notes: remember that your falling mass can't hit the floor (this is still in the rules, right?) or that's a construction violation. The no-touching-the-floor rule is why I went with this loop approach to launching the car. Initial attempts last season had a single line that pulled the car but after the car was released, the line could touch the floor--a tier if someone decides to call me out for it! Best to avoid any risks breaking rules before the competition. With the loop method shown in the video, the loop is kind of taut and looped through the eye bolts after launch so no worries about it touching the floor.

For elastic, I tried a number of kinds last season. Started with metallic springs--didn't like them. I think I only decided to use Tan Super Sport rubber (the kind provided in Freedom Flight kits that need it) because I was on Wright Stuff. It's good stuff. I think normal office rubber bands would work fine, but it's convenient to have a continuous length of rubber: fewer knots. And if you plan on testing a lot, make sure to use o-rings (even if you don't test a lot, use o-rings) and some additional reinforcement if you choose to use fishing line along with it. Fishing line cuts through the rubber bands quickly due to tension and eventually cuts through the o-rings. Also, avoid metal attachments to your elastic (and if you must then don't test your launcher without a vehicle in it). Stretched elastic and metal can give some bad finger bruises or at best snap your fishing line.

I documented our device with photos and I'm happy to share, but I'd have to find them--hopefully they're not on the SD card I lost...

[SluffAndRuff]

Thanks both bernard and fishman100 for the thorough descriptions and tips.

I modified my launcher by slightly altering the locking mechanism and elastic I used, and now it works, but I'm getting around 1.9 seconds from 0.5-8.5 meters. I guess this is decent but clearly you guys have gotten better times, so I'll continue to experiment and modify mine.

And lastly, bernard, pictures would indeed be helpful if you'd like to share. Though don't go through too much trouble trying to find them.

[fishman100]

Thanks both bernard and fishman100 for the thorough descriptions and tips.

I modified my launcher by slightly altering the locking mechanism and elastic I used, and now it works, but I'm getting around 1.9 seconds from 0.5-8.5 meters. I guess this is decent but clearly you guys have gotten better times, so I'll continue to experiment and modify mine.

And lastly, bernard, pictures would indeed be helpful if you'd like to share. Though don't go through too much trouble trying to find them.

1.9s in VA will definitely put you at or near the top, but if you want to reduce your time further don't forget about other factors such as friction, car's mass etc.

[SluffAndRuff]

Thanks both bernard and fishman100 for the thorough descriptions and tips.

I modified my launcher by slightly altering the locking mechanism and elastic I used, and now it works, but I'm getting around 1.9 seconds from 0.5-8.5 meters. I guess this is decent but clearly you guys have gotten better times, so I'll continue to experiment and modify mine.

And lastly, bernard, pictures would indeed be helpful if you'd like to share. Though don't go through too much trouble trying to find them.

1.9s in VA will definitely put you at or near the top, but if you want to reduce your time further don't forget about other factors such as friction, car's mass etc.

Okay, that's interesting. I know that VA is not an extremely competitive state, but still...

Also, my car is quite light - about 150 grams without the egg. Based on other posts in past forums this seems lower than the vast majority of cars, so I think I can easily lower my current time substantially.