Gears

[windu34]

I would suggest metal, as they wont shear under large forces. Plastic gears are simply inconsistent and never reliable in comparison to metal gears.

Normally, I would completely agree with you, but for this application, plastic gears are better because of the reduction of weight and rotation inertia and the fact that there is simply no large force acting on the gears that could possibly cause a tooth to break. Check out Nestor's implementation for EV: https://www.youtube.com/watch?v=pKC8MYRgflI

[retired1]

Also the whole car probably weighs about 1/3 of the electric car plus the brushed motor is no where near as fast or as strong as the brushless.

[shrewdPanther46]

I would suggest metal, as they wont shear under large forces. Plastic gears are simply inconsistent and never reliable in comparison to metal gears.

Normally, I would completely agree with you, but for this application, plastic gears are better because of the reduction of weight and rotation inertia and the fact that there is simply no large force acting on the gears that could possibly cause a tooth to break. Check out Nestor's implementation for EV: https://www.youtube.com/watch?v=pKC8MYRgflI

Thanks for feedback windu34. I took a look at Nestor's video. Is there any reason as to why he is not directly gearing to his motor?

[retired1]

Plastic gears with metal hub and set screws---- The easiest I have found is SDP-SI.com Thrash around a bit and you will find it.. The site is slow responding to some clicks.
I selected metric, but inch is available. Filters-I chose a mod 0.5 as it is close to a 48 pitch. Check the hub with set screw box. I used acetyl/brass box. I used a 4 mm bore (3 and 6 mm are available in this exact gear. Teeth run from 22 to 45.
Price is about $7.50 each, but you get exactly what you order. Watch out for the up charge for orders less than $50 (i think).

If I had looked closely at this, it would have saved money in getting what I wanted that is totally compatible rather than the cheaper chineese ones. Shipping was fast- some of the import ones were out of stock and a very delayed arrival.
I am going to use them on the balsa wood buggy.

[SPP SciO]

Just wanted to share some info that may not be helpful for elite teams but may help a team trying to get started -

My students spent a lot of time experimenting with a variety of plastic gears and simple 6v hobby motors. Limited success, mostly because they found it really hard to make all the pieces cooperate, so everything that “worked” was less than ideal. I sprung for this: https://www.servocity.com/970-rpm-econ-gear-motor and they used it to directly drive a wheel. I don’t have any time data to share but it’s much quicker than anything else that they tried. Getting it to run straight was a challenge they quickly figured out how to solve.

In general as a coach I’ve found that if you lack the tools (and knowledge and skills...) to scratch build something well, it’s worth looking at a single vendor for off the shelf supplies. Looking through the servocity site for example, my students can shop for all the parts they’d need, and I can order them knowing it’s money well spent since all the pieces are compatible. The mixing and matching, especially if you don’t have bins of spare parts, is an expensive and time consuming process.

[shrewdPanther46]

Just wanted to share some info that may not be helpful for elite teams but may help a team trying to get started -

My students spent a lot of time experimenting with a variety of plastic gears and simple 6v hobby motors. Limited success, mostly because they found it really hard to make all the pieces cooperate, so everything that “worked” was less than ideal. I sprung for this: https://www.servocity.com/970-rpm-econ-gear-motor and they used it to directly drive a wheel. I don’t have any time data to share but it’s much quicker than anything else that they tried. Getting it to run straight was a challenge they quickly figured out how to solve.

In general as a coach I’ve found that if you lack the tools (and knowledge and skills...) to scratch build something well, it’s worth looking at a single vendor for off the shelf supplies. Looking through the servocity site for example, my students can shop for all the parts they’d need, and I can order them knowing it’s money well spent since all the pieces are compatible. The mixing and matching, especially if you don’t have bins of spare parts, is an expensive and time consuming process.

Glad to hear that your students have found success. I'm just curious, how would you connect such a motor directly to the wheel? If the wheel is placed directly on the motor shaft, wouldn't it be necessary to use to separate motors (assuming the optimal 4 wheels, 2 wheel drive in the back), one of them being synchronous (but since its synchronous is compatible with AC, idk how this would work) ? I am curious as to what your plan is.

Also, I was wondering how your students were able to get their vehicle to run perfectly straight with so much ease. From what I have done, no matter how accurate you think your vehicle is, it will never go perfectly straight, resulting in the need for "dynamic" steering...

[SPP SciO]

Glad to hear that your students have found success. I'm just curious, how would you connect such a motor directly to the wheel? If the wheel is placed directly on the motor shaft, wouldn't it be necessary to use to separate motors (assuming the optimal 4 wheels, 2 wheel drive in the back), one of them being synchronous (but since its synchronous is compatible with AC, idk how this would work) ? I am curious as to what your plan is.

Also, I was wondering how your students were able to get their vehicle to run perfectly straight with so much ease. From what I have done, no matter how accurate you think your vehicle is, it will never go perfectly straight, resulting in the need for "dynamic" steering...

The wheel they're using has a hub which fits directly onto the motor shaft (which is 4mm) with a set screw. A motor mount keeps it screwed onto the chassis. "Perfectly straight with so much ease" is definitely an overstatement - What I meant is, straight enough to get the centerline bonus over the course of the run. There's definitely room for improvement, for the sake of accuracy (but if a car systemically drifts a certain amount you can adjust for this a little when testing). They have a three-wheeled vehicle, with the one drive wheel centered, and the braking system on the back axle.

Major caveat - I'm in no way advocating this as "the" solution - my students have a long way to go before they're competition-ready and it's a guarantee that the design will change over time. It's quite possible that we'll realize soon why 4-wheeled, gear-driven vehicles are the norm.

[rajofin]

Can you point me to the hub that you are talking about? Seems like I do not know enough to find one that could directly make wheels rotate without using gears.

[shrewdPanther46]

Can you point me to the hub that you are talking about? Seems like I do not know enough to find one that could directly make wheels rotate without using gears.

Any wheel hub that fits over the diameter of whatever the motor shaft diameter it is. You can look for one, or create one. Finding parts that are compatible is definitely a challenge for this event, so I suggest you take the time to choose wisely.

[TheWingsOfFire]

What are some ideas on how to actually transfer the motor's power to the axle? Which gears do I use?