build ideas

retired1
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build ideas

Post by retired1 » September 8th, 2017, 11:11 am

Before you buy anything, take a long look at how they will interface. I started by finding a motor that I thought was really great. It had a 4 mm output shaft Trying to find a set of either 32 or 48 pitch gear that would fit a 4 mm motor and a 4 mm axle turned out to be very difficult.

Start with a proposed wheel, find the circumference and see how many revolutions it will take to go 10 meters. Decide what time you would like to have the run take . You can now find the desired RPM (remember the no load rpm for the motor is more than you will actually get).

For this years rules, consider using long axles. Then what size axle to use. 1/8 inch will be easy to find gears for. 1/4 is fairly common also. Just make sure that both gears have the same pitch and contact angle (14.5 or 20) or they will not work.

Affordable bearings are easier to find in either size. Do you want to use ball bearings or plastic bushings? Bushings cost less and are easy to use, but no quite as efficient as ball bearings.

Common steel all thread can be found at your local big box store, but stainless has a more uniform size. If you are going to use a wing nut brake, you need one of the axles to be all thread. Solid rod for the other axle will fit the bearings better, but for some odd reason , good rod costs more.

One wrap of teflon tape will remove a bit of the slop between the all thread and the bearing. You want the rod snug in the bearing so the friction is in the bearing (less) . Bushings do not care.

All of this is my opinion only.

I am open to PM's if anybody wants more help.

kumarand
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Re: build ideas

Post by kumarand » October 7th, 2017, 5:17 pm

Where can we find the parts. It it pretty challenging.

retired1
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Re: build ideas

Post by retired1 » October 7th, 2017, 6:50 pm

Searching for parts can be very daunting.
Where are you so far? wood or metal frame?
Do you have any parts for the buggy?
What is your budget?

retired1
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Re: build ideas

Post by retired1 » October 10th, 2017, 6:26 pm

Sep 1 - what size wheel? Small has to turn at a very high speed. big may take more power than the motor can put out safely. My thought is that 2" is about the minimum and 4" is about the max.

For that diameter and thus circumference, what rpm will you need to go an arbitrary 10 m? ( in 2, 3, 4 or 5 seconds)
This will lead you to the motor speed and the appropriate gears.

Come back with that and a proposed shaft diameter and I will help you find bearings and mounting devices.

I would recommend 1/8 or 3/16 hobby plywood for the body as it is the quickest, easiest and safest way. It can have hols drilled in it to lighten it if desired.

Questions?

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Re: build ideas

Post by TylerB » October 30th, 2017, 12:29 pm

Are we allowed to use a color sensor to stop at the tape showing the end?

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Re: build ideas

Post by wzhang5460 » October 30th, 2017, 1:37 pm

It says what you can use in the rules, and I'm pretty sure that a color sensor isn't in the list of electrical components you can use.
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Re: build ideas

Post by Almandine » October 30th, 2017, 6:33 pm

I recommend using a brake as your braking system. I find easy to implement and very effective
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Re: build ideas

Post by shrewdPanther46 » October 30th, 2017, 7:21 pm

Almandine wrote:I recommend using a brake as your braking system. I find easy to implement and very effective
Could you elaborate on what you mean by "brake" ?

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Re: build ideas

Post by rajofin » October 31st, 2017, 8:34 am

retired1 wrote:Sep 1 - what size wheel? Small has to turn at a very high speed. big may take more power than the motor can put out safely. My thought is that 2" is about the minimum and 4" is about the max.

For that diameter and thus circumference, what rpm will you need to go an arbitrary 10 m? ( in 2, 3, 4 or 5 seconds)
This will lead you to the motor speed and the appropriate gears.

Come back with that and a proposed shaft diameter and I will help you find bearings and mounting devices.

I would recommend 1/8 or 3/16 hobby plywood for the body as it is the quickest, easiest and safest way. It can have hols drilled in it to lighten it if desired.

Questions?
Hi - If I were to go with 3" wheels and aim to complete distance in around 4 secs, can you give me some guidance about the parts. I am just looking to get some ideas on where to start finding parts and this will help me a lot.

Thank you

shrewdPanther46
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Re: build ideas

Post by shrewdPanther46 » October 31st, 2017, 9:37 am

rajofin wrote:
retired1 wrote:Sep 1 - what size wheel? Small has to turn at a very high speed. big may take more power than the motor can put out safely. My thought is that 2" is about the minimum and 4" is about the max.

For that diameter and thus circumference, what rpm will you need to go an arbitrary 10 m? ( in 2, 3, 4 or 5 seconds)
This will lead you to the motor speed and the appropriate gears.

Come back with that and a proposed shaft diameter and I will help you find bearings and mounting devices.

I would recommend 1/8 or 3/16 hobby plywood for the body as it is the quickest, easiest and safest way. It can have hols drilled in it to lighten it if desired.

Questions?
Hi - If I were to go with 3" wheels and aim to complete distance in around 4 secs, can you give me some guidance about the parts. I am just looking to get some ideas on where to start finding parts and this will help me a lot.

Thank you
Assuming that the diameter of your wheels is 3" inches, your motor needs around 600 rpm to cover 9 meters in 4 seconds (3" wheels=9 inches per revolution, and you need to cover around 360 inches, so about 40 revolutions per 4 seconds=600 rpm). tbh I am a bit confused as to how it came out to only 600 rpm, please correct me if I am wrong. Anyways, I would suggest using a 6V motor along with 5 AA rechargeables like everyone else (that is what I'm doing as well). You probably can get well within 4 seconds with this setup, as it is relatively light weight, and you can buy higher rpm motors to push yourself to lower times while still maintaining accuracy. There are some really good 6V motors out there, and they can be easily found. As a chassis, I would recommend either a plywood sheet, or a metal chassis. You can just visit home depot, or radio shack, to pick up everything you need (plywood, switches, batteries, wires, wheels, basic microswitch- hinge roller). I just bought everything off of amazon. Just find the specific specs you wish to acquire and check online. I am sure you will find what you need.

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