Mousetrap Vehicle C

[binary010101]

We're tying the string to the axles, so we're using friction tape to make sure that the string doesn't move.

[packer-backer91]

I have a problem with keeping constant tension on the string that is pulled off our axel. From my initial test my guess is our design only used about 15-25 of energy provided by mouse traps yet ours had one huge amount of acceleration for maybe 5 feet then coasted to the 7m line with easy but there was no energy to bring the vehicle back. This was a huge disappointment for my team we had put over 20 revolutions of string on the axel to only get maybe 3.5-4 of them to actually get power from the mousetrap. This event is turning out to be much more complicated than I would have thought in comparison to the other vehicle events I have done through the years

[winneratlife]

We're tying the string to the axles, so we're using friction tape to make sure that the string doesn't move.

While that actually makes sense, I found it useful to...instead of tying the string on, I used a metal axle (basically a long pole screw) and two nuts to sandwich the end of my string. Tighten it a ton and you shouldn't have any problems with moving string. Friction tape does work too, in that regard.

I have a problem with keeping constant tension on the string that is pulled off our axel. From my initial test my guess is our design only used about 15-25 of energy provided by mouse traps yet ours had one huge amount of acceleration for maybe 5 feet then coasted to the 7m line with easy but there was no energy to bring the vehicle back. This was a huge disappointment for my team we had put over 20 revolutions of string on the axel to only get maybe 3.5-4 of them to actually get power from the mousetrap. This event is turning out to be much more complicated than I would have thought in comparison to the other vehicle events I have done through the years

a) I'm assuming you mean 15-25%?
b) Describe the problem more, although I partially understand. I think you're problem may be that the string must be tight! When winding it up, hold the string so that there is no slack at all. When finished winding, place the wheels attached to the string on the ground after you set your mousetrap. The string should not be all over the place, or it will unwind without turning the axle. You may also want to use friction tape like binary so that the string doesn't move, or use the nuts idea. (I'm assuming you're using the pin-axle design?)

[packer-backer91]

The string is tight we it starts but once the mouse trap activates the wipe pulls off only a small amount of string is pulled off, I have seen one two video's from YouTube a similar system to the one I use and the mousetraps/wipe act slow, controlled, and constant. While mine as soon as its activated it pools a small amount of string off in the begging of the run then some how string is loose. for the wipe we use a carbon tube while extremely strong/light has no flex in it. This may be the secret to what I have not tried may be a flexible fishing rod or something like that. For the other vehicles I have seen it takes the complete run for "kill bar" to hit the other side of the mouse trap. While mine takes about 1/2 sec to hit the other side [that was shocking I almost got hit with the wipe in the face activating the mouse traps]. This produced good acceleration but for only a few feet the coasted to the end, thus no remaining energy to come back. So in total my coach showed that he only got a small amount of actually work from the mouse trap to be used the 15-25% of the total work that can be done with the mouse traps. From this the speed was impressive and if maintainable will be fast [less than 5 sec one way]. My coach believes it because the string we pull with has nothing to pull against as the vehicle starts thus allowing for the string to get loose thus causing the mouse trap to just snap down pulling off no more string. I know this may be confusing but is the best way I can explain it.

I wanted to use the pin axel but that will not work anymore we need a smaller axel so we can use less string

[winneratlife]

The string is tight we it starts but once the mouse trap activates the wipe pulls off only a small amount of string is pulled off, I have seen one two video's from YouTube a similar system to the one I use and the mousetraps/wipe act slow, controlled, and constant. While mine as soon as its activated it pools a small amount of string off in the begging of the run then some how string is loose. for the wipe we use a carbon tube while extremely strong/light has no flex in it. This may be the secret to what I have not tried may be a flexible fishing rod or something like that. For the other vehicles I have seen it takes the complete run for "kill bar" to hit the other side of the mouse trap. While mine takes about 1/2 sec to hit the other side [that was shocking I almost got hit with the wipe in the face activating the mouse traps]. This produced good acceleration but for only a few feet the coasted to the end, thus no remaining energy to come back. So in total my coach showed that he only got a small amount of actually work from the mouse trap to be used the 15-25% of the total work that can be done with the mouse traps. From this the speed was impressive and if maintainable will be fast [less than 5 sec one way]. My coach believes it because the string we pull with has nothing to pull against as the vehicle starts thus allowing for the string to get loose thus causing the mouse trap to just snap down pulling off no more string. I know this may be confusing but is the best way I can explain it.

I wanted to use the pin axel but that will not work anymore we need a smaller axel so we can use less string

Not sure what you're saying, if somebody else could clarify it for me maybe I could figure it out...
The only thing I can really tell you is that you do not want the "wipe" (I'm assuming that this is the extension of the killbar) flexible for 2 reasons:
1. I once had an event supervisor almost DQ me for it, claiming that not everything is in its lowest energy state at the beginning of the run (I don't think most supervisors care, but never take a chance)
2. A flexible bar can lead to oscillation, i.e. the vehicle coming all the way back, then going further as the bar gives a bit, then coming back, and back and forth until it centers near the starting line. While the distance is largely unaffected, it can waste large amounts of time (this cost me a 3rd place at Clio, which would've made me the first person in my school's history to take 3rd at a building event at that invitational)...

[packer-backer91]

This does bring up a good point, that I believe that a bent/flexed rod like I have seen on YouTube would be illegal because, I don't think they will conceder when the rod is bent to be at its "lowest energy state". At some Regional’s you would be right that the supervisor’s don’t care [like mine] but at State they fallow the rules well. Last year was the first year that I saw something run incorrectly.

What I meant in my explanation in summery is that the whip/ kill bar starts with the string is Tight then once vehicle starts travels a few feet [accelerating] but then coast to the end and has no power to return. This is because the string was some how became loose thus allowing the mouse trap to snap down with the normal speed [unlike the slow controlled motion needed to power the vehicle].


Has anyone else had a similar problem to what I have now or have a solution. I would like to stay away from anything that applies any friction [means loss of speed capability] it looks like I have no choice.

[winneratlife]

This does bring up a good point, that I believe that a bent/flexed rod like I have seen on YouTube would be illegal because, I don't think they will conceder when the rod is bent to be at its "lowest energy state". At some Regional’s you would be right that the supervisor’s don’t care [like mine] but at State they fallow the rules well. Last year was the first year that I saw something run incorrectly.

What I meant in my explanation in summery is that the whip/ kill bar starts with the string is Tight then once vehicle starts travels a few feet [accelerating] but then coast to the end and has no power to return. This is because the string was some how became loose thus allowing the mouse trap to snap down with the normal speed [unlike the slow controlled motion needed to power the vehicle].


Has anyone else had a similar problem to what I have now or have a solution. I would like to stay away from anything that applies any friction [means loss of speed capability] it looks like I have no choice.

The friction tape goes on the axles, but doesn't touch the frame. It only adds friction to the string-axle connection, so that the string is more tight. This should solve your problem.

[packer-backer91]

well I got my vehicle to work now but is SLOW [between 23-33seconds] I expect it to get a little fast with some fine tuning, but what are some of the other times that others have gotten. My school could not go to an Inv. which puts me at a large disadvantage from where I usually am for build it events. I really don’t know if what I have is a good time, but to me is way to slow, although for only a few test runs their has been some large improvements already in the time. This event is going to be much more difficult than I expected, it will take me a long time to maximize the number of wheel rotations that produce the most speed with getting the most out of the mousetrap.

[winneratlife]

well I got my vehicle to work now but is SLOW [between 23-33seconds] I expect it to get a little fast with some fine tuning, but what are some of the other times that others have gotten. My school could not go to an Inv. which puts me at a large disadvantage from where I usually am for build it events. I really don’t know if what I have is a good time, but to me is way to slow, although for only a few test runs their has been some large improvements already in the time. This event is going to be much more difficult than I expected, it will take me a long time to maximize the number of wheel rotations that produce the most speed with getting the most out of the mousetrap.

Um, at regionals, I prefer anyhow. But, at states, I believe it will make a difference. Again, what design are you using?

Make the vehicle lighter. Also, in my region, I could easily take second with my current car (behind Troy), and the speed was 40 seconds-ish. Of course, I built a lighter one (I didn't use balsa before), so I except to cut down on the time.

[packer-backer91]

what, my vehicle is not slow, It is already made out of balsa for all of the frame only have 3 pieces of metal [2 axels and a strip of Aluminum to connect the trigger mechanism on each mouse trap together] on the whole vehicle, the problem is we have to use double DVD wheels which weigh a lot more than I wanted it to. I broke a wheel on my vehicle and I don’t know how/why it happened after the first test I ever did, might have happened just from rotating the wheels on the put a little too much stress on the wheel and then it broke. I really can’t get rid of more weight because the wheels with axels are probably about 60% of the weight, mousetrap with whip is about 30% of weight and only 10% of weight is the balsa wood. If I had a guess the balsa wood in the frame is probably only 50-90 grams. I don’t know another light yet strong wheel that can be used as an alternative for the DVD's.