build ideas

retired1
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build ideas

Postby retired1 » Fri Sep 08, 2017 6:11 pm

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

Postby kumarand » Sun Oct 08, 2017 12:17 am

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

retired1
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Re: build ideas

Postby retired1 » Sun Oct 08, 2017 1:50 am

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

Postby retired1 » Wed Oct 11, 2017 1:26 am

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

Postby TylerB » Mon Oct 30, 2017 7:29 pm

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

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Re: build ideas

Postby wzhang5460 » Mon Oct 30, 2017 8:37 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

Postby Almandine » Tue Oct 31, 2017 1:33 am

I recommend using a brake as your braking system. I find easy to implement and very effective
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shrewdPanther46
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Re: build ideas

Postby shrewdPanther46 » Tue Oct 31, 2017 2:21 am

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

Postby rajofin » Tue Oct 31, 2017 3:34 pm

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

Postby shrewdPanther46 » Tue Oct 31, 2017 4:37 pm

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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Re: build ideas

Postby rajofin » Tue Oct 31, 2017 6:50 pm

Thank you for your help..really appreciate it!!!

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Re: build ideas

Postby shrewdPanther46 » Tue Oct 31, 2017 8:22 pm

no problem. let me know how it goes
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rajofin
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Re: build ideas

Postby rajofin » Sun Nov 12, 2017 2:16 pm

shrewdPanther46 wrote:no problem. let me know how it goes
I think you got 600 rpm since you didn't account for gear ratio reduction. With 4:1 reduction, we will need around 2400 rpm. Isn't this right or I am on a wrong path?

Also, I see in many videos wheels used are as https://www.youtube.com/watch?v=SeO5pAGueIA. Any idea where to get those. Couldn't find them on homedepot unless I am getting confused. TIA.

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Re: build ideas

Postby shrewdPanther46 » Sun Nov 12, 2017 3:07 pm

rajofin wrote:
shrewdPanther46 wrote:no problem. let me know how it goes
I think you got 600 rpm since you didn't account for gear ratio reduction. With 4:1 reduction, we will need around 2400 rpm. Isn't this right or I am on a wrong path?

Also, I see in many videos wheels used are as https://www.youtube.com/watch?v=SeO5pAGueIA. Any idea where to get those. Couldn't find them on homedepot unless I am getting confused. TIA.


I made the assumption of direct gearing. Depending on the mass of your vehicle (and torque of the motor), and the optimum speed vs. torque ratio for your specific car, you will need different gear ratios. I suggest not thinking too hard right now about your ratio and just buy a generally high quality motor, and then toy around with your ratios. But yes, you are generally thinking along the right path.

Those wheels are banebots wheels. Banebots.com sells them
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ramnath.t@gmail.com
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Re: build ideas

Postby ramnath.t@gmail.com » Thu Nov 30, 2017 1:01 am

Could you please suggest how to attach the BaneBots wheel to the 1/4 in threaded rod.


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