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Device for driving straight

Posted: November 6th, 2017, 3:48 pm
by wchamp
My kids are convinced they can use a guidewire that is on the track or above the track that will help guide their buggy to go straight. I don't think this is allowed. Thoughts?

Re: Device for driving straight

Posted: November 6th, 2017, 4:25 pm
by dmis
Look at rule 4.c.iv. It would appear that the guidewire would need to be removed before the vehicle moves, but can be used to position it.

Re: Device for driving straight

Posted: November 6th, 2017, 4:53 pm
by shrewdPanther46
yea as long as it is removed prior it is allowed (aligning purposes really- its not going to help the car go straight). The only way to get a car that goes perfectly straight is finding a way to make sure the axles are perfectly parallel with each other, and the transmission of rotational energy from the motor to one of the axles (front or back, I am using front so the car doesn't fishtail during braking) is even.

Re: Device for driving straight

Posted: November 7th, 2017, 11:53 am
by windu34
Take it from someone with a pretty extensive background in vehicle events: no matter how perfect you think your manufacturing tolerances are and no matter how perfect you think your calculations are, your vehicle will never go perfectly straight and your chassis will never be perfect. It is crucial that you have a way to adjust the steering of the vehicle by have one of the axles adjustable and a sturdy frame to prevent accidental alterations during runs and in transport. I feel that competitors in vehicle events take chassis way to lightly - it is one of the most critical aspects of your car and you should never comprise your chassis for a decrease in weight. That said, there are plenty of ways to decrease the weight of your chassis (Carbon fiber, 3D printing) while maintaining rigidity.

As for steering, if a laser is not allowed for aiming and removal afterwards, use a rifle scope that either attaches and detaches from your vehicle or have a separate aiming structure/housing.

Re: Device for driving straight

Posted: December 31st, 2017, 10:31 am
by shrewdPanther46
windu34 wrote:As for steering, if a laser is not allowed for aiming and removal afterwards, use a rifle scope that either attaches and detaches from your vehicle or have a separate aiming structure/housing.


Hi,
So my school has an invitational coming up in a week, so we don't want to have to buy a rifle scope, then design and 3d print a mount, retest everything etc. etc.

So, is there a somewhat consistent way to line up the car straight given only the starting point and end point?
Also, for those that have gone to competitions, do supervisors generally have a centerline that is marked and visible on the track (ex: a piece of masking tape down the center of the track) ?

Re: Device for driving straight

Posted: January 2nd, 2018, 5:35 pm
by shrewdPanther46
ideas?

Another thing, we were able to get our car to go straight, but rarely, it just randomly curves off to the side by around 6-7 cm (to either the right or left, so its kind of erratic). Any clues on this?

Re: Device for driving straight

Posted: January 3rd, 2018, 6:30 pm
by windu34
shrewdPanther46 wrote:
windu34 wrote:As for steering, if a laser is not allowed for aiming and removal afterwards, use a rifle scope that either attaches and detaches from your vehicle or have a separate aiming structure/housing.


Hi,
So my school has an invitational coming up in a week, so we don't want to have to buy a rifle scope, then design and 3d print a mount, retest everything etc. etc.

So, is there a somewhat consistent way to line up the car straight given only the starting point and end point?
Also, for those that have gone to competitions, do supervisors generally have a centerline that is marked and visible on the track (ex: a piece of masking tape down the center of the track) ?

Centerlines are a 40/60 chance and not in your favor. Sometimes they are there, sometimes not. I cant think of anything other than a scope except some sort of stick with 2 pieces to aim with

Re: Device for driving straight

Posted: February 4th, 2018, 5:59 am
by mderoller
I think to get the center line bonus you just want to make your buggy as wide and long as the rules allow.

For aiming we are using the front dowel, which has to extend at least 20cm above the floor, and we have exactly centered with the front wheels, and a dowel in the rear, which is also centered with the front wheels. The front wheels are at the maximum width 30cm. The buggy is also close to the maximum length of 60cm. The rear wheels are the drive wheels and much narrower, but square with the front wheels. So lining up the front and rear dowels with the finish point, if the front and rear wheels are not perfectly square, the long wheelbase reduces veering from the center.

Re: Device for driving straight

Posted: March 15th, 2018, 3:42 pm
by SPP SciO
windu34 wrote: It is crucial that you have a way to adjust the steering of the vehicle by have one of the axles adjustable ...

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Hey windu, my students (and myself!) were recently impressed with your 2016 Ev, featured on the Best Of wiki page and youtube. Was steering the purpose of those cables running between the two axles? They looked like mini versions of the ratchet straps one would use to secure stuff to a car roof. Not sure what you were using, but would a threaded rod be able to function in a similar way? Also, it seemed as though they were on both sides of the vehicle - is this critical, or just added security? Any insight or advice would be appreciated!

Re: Device for driving straight

Posted: March 15th, 2018, 4:39 pm
by windu34
SPP SciO wrote:
windu34 wrote: It is crucial that you have a way to adjust the steering of the vehicle by have one of the axles adjustable ...

.


Hey windu, my students (and myself!) were recently impressed with your 2016 Ev, featured on the Best Of wiki page and youtube. Was steering the purpose of those cables running between the two axles? They looked like mini versions of the ratchet straps one would use to secure stuff to a car roof. Not sure what you were using, but would a threaded rod be able to function in a similar way? Also, it seemed as though they were on both sides of the vehicle - is this critical, or just added security? Any insight or advice would be appreciated!

Steering was the purpose of the straps, which consisted of zipties, 100lb test braided fishing line, and o-rings. This concept was something we threw on to the vehicle at the last minute before States and never got around to upgrading the system for nationals because it worked well enough and did the job. Using threaded rods is absolutely the better way of doing this, however it will add alot of weight. For battery buggy, I would NOT recommend threaded rods unless you need to add weight. Although threaded rods would be way more precise and sturdy, its really too much weight and the straps i made worked well. They required adjustment before every competition (not every run, when testing, we only needed to calibrate once before testing session and it was good) to adjust the car steering to make it go straight and it was pretty darn accurate. Having it on both sides of the vehicles was necessary to maintain proper tension to make sure the vehicle didnt shift its steering during setup for the run(s). If you email me, I would be willing to send you a manuscript of the methodology I used to tune it.

Re: Device for driving straight

Posted: March 15th, 2018, 5:46 pm
by SPP SciO
windu34 wrote:[ ... Using threaded rods is absolutely the better way of doing this, however it will add alot of weight. For battery buggy, I would NOT recommend threaded rods unless you need to add weight....


Thanks for the quick reply! Frankly their vehicle is already heavy since most of my supply is servocity parts, including the motor. It’s not particularly fast (< 4 seconds) but they stand to gain the most from improving accuracy, and the lateral drift is tough. I’ll take some pics tomorrow and send you an email.