My first project

[ARU_CC]

Hello everyone, as I said in the presentation message, I am new to karts, I have never built anything like this, although I am very motivated to achieve it.
The plan is to be able to make a kart where I can go together with my 6-year-old son, so I will have to make something wider than for a single person, giving preference to strength and not speed.

The engine will be recycled from an old 49cc motorcycle, they are going to give it to me, I still don't have it in my hands, so I don't know its condition, this has its advantages and disadvantages, since it is water cooled, but on the contrary It has a centrifugal clutch, I hope to be able to start it.

I already have some pieces, I just received the wheels, these are 26cm 10 inches, solid and with a 1.6cm 0.62 inch axle.
I also have a bicycle disc brake and a 36 tooth sprocket and bearings for the axle.

My main doubt is that I am going to use a square profile, I don't know if 20x20x1.5mm will be enough or I need 25x25x1.5mm, that is, 0.78 inches or 1 inch?
It should hold about 100kg of people plus the motor.

I also have another question regarding the suspension, I have seen that sometimes small springs are added to the front wheels, what type of spring should I use?

Sorry if the text is not understood well, since I use the translator, and I also work in millimeters and not inches.

Regards, and thank you very much.

 

[ezcome-ezgo]

Using square steel tubing will be fine. Those wheels (tires) are garbage, trash. They will not last and will risk injury. Your sprocket is designed to fit on a bicycle wheel cartridge. It will fold up like paper under the torque of an engine.

Kartshop | The ultimate karting store online

Online Karting store with the largest selection of kart parts and racing gear in the world and official importer of OTK karts.

kartshop.com

 

[Rat]

That brake is not for a bicycle, its for a mini bike (absolutely not the same thing) it will work though

 

[Speedster]

Using square steel tubing will be fine. Those wheels (tires) are garbage, trash. They will not last and will risk injury. Your sprocket is designed to fit on a bicycle wheel cartridge. It will fold up like paper under the torque of an engine.

Kartshop | The ultimate karting store online

Online Karting store with the largest selection of kart parts and racing gear in the world and official importer of OTK karts.

kartshop.com

For low speeds, I would think they would be fine.

 

[ARU_CC]

The wheels don't seem to be of poor quality, but I certainly bought the cheapest ones I could find that had metal rims. Later if everything continues well, I will change them.

Certainly the sprocket is very thin, I will look for another one.
What would be the appropriate number of teeth? Like I said, I prefer strength to speed, so 70,80,90?

I didn't know about this store, thanks, I'll check it out

at least the brake will work, thanks

This is the type of spring suspension I am referring to, this image is taken from YouTube (Go-Kart Kit Build - Orange Krate Clone - GoKartAlley)

What do you think of this suspension? worth?

 

[Speedster]

What size of engine are you thinking?

 

[Speedster]

What size of engine are you thinking?

Oh, duh. You already said that.

 

[Speedster]

What I would do is head over to the other part of this website and use the speed calculator. Enter all your hard and fast info, and then enter the sprocket tooth count of different sizes until the top speed is as low as you want to make it. Then it will have as much torque to the wheels as possible for the speed you want to attain. Hope that makes sense?

 

[Denny]

For your purposes those springs will not be necessary or needed. I don’t think the 49cc engine is going to have near enough torque to make that kart move. Others have tried and failed miserably. A used roto tiller type engine would work better. Those tires and wheels have never proven to be a good idea or safe. The bearings in them are junk.

 

[ARU_CC]

Thank you for all your comments.

I understand that you are referring to this calculator, correct?
https://spicerparts.com/calculators/transmission-ratio-rpm-calculator

Perfect, I'll forget about the spring suspension.

If the problem with the wheels is the bearings, I can change them, in any case, only the front wheels will have them, I will have to remove them at the back to be able to adapt the axle.

I think you're right, the 49cc engine is going to be a mistake. It is also old and has not been started for many years, the liquid cooling also complicates things for it to be my first kart, although of course, it is free.

This weekend I will be away from home, but next week I want to start building the chassis, I will show the progress.

Thanks

 

[Rat]

Thank you for all your comments.

I understand that you are referring to this calculator, correct?
https://spicerparts.com/calculators/transmission-ratio-rpm-calculator

Perfect, I'll forget about the spring suspension.

If the problem with the wheels is the bearings, I can change them, in any case, only the front wheels will have them, I will have to remove them at the back to be able to adapt the axle.

I think you're right, the 49cc engine is going to be a mistake. It is also old and has not been started for many years, the liquid cooling also complicates things for it to be my first kart, although of course, it is free.

This weekend I will be away from home, but next week I want to start building the chassis, I will show the progress.

Thanks

I wouldn't cut and run on the 49cc engine if it's and actual motorcycle type like a Pw50, Yz50, CR50R, or a clone if any one if them simply because they are clutched and generally have at least a 4 speed gearbox.

If you meant a minibike or mini chopper, than Denny is on point; it's junk and even an 80cc is going to go nowhere fast trying to move more than 150lbs around and a 2 seater kart is going to weigh no less than that dry.

You're going to want no less than 196cc or 5hp, but ideally any 7hp with the gov turned in is going to be more fun for longer as the little dude gets to being not so little anymore.
Toys that can grow with a kid tend to make the best memories over the ones quickly outgrown that just end up forgotten

 

[panchothedog]

Like Rat said. That engine will work ONLY if it has a 3 or 4 speed transmission attached to it. If you're trying to run just a clutch, then 196cc minimum. A torque converter will work much better than a centrifugal clutch. NOW about your frame material. You need 25 x 25 =1". But 1.5 mm wall thickness, = 1/16". It will fold up in half the first time you hit a bump. If there is anything available between 1.5 mm and 3 mm it might be OK. Otherwise use 3 mm which is 1/8".

 

[panchothedog]

Remember, you are building a motorized vehicle. Not a bicycle or a pedal toy.
Don't end up with something so cheap and flimsy that it gets you or your son hurt, or worse trying to save $10 or $20. If you can't afford to do it correctly, then don't build it. Do it right, or find another hobby.

 

[Rat]

Remember, you are building a motorized vehicle. Not a bicycle or a pedal toy.
Don't end up with something so cheap and flimsy that it gets you or your son hurt, or worse trying to save $10 or $20. If you can't afford to do it correctly, then don't build it. Do it right, or find another hobby.

I've said that to someone... Do it right or Not at all.
Even if you have to build slowly, or stockpile materials before you build (stockpiling is better because then youre less likely to be in a groove half built and out of materials. I'm assuming we own a welding rig and have at least intermediate skills running it.

 

[Speedster]

I understand that you are referring to this calculator, correct?
https://spicerparts.com/calculators/transmission-ratio-rpm-calculator

This is the one I had in mind: speed calculator, although the one you posted might work. But this one is meant for go karts, and would be a lot easier to understand. At least for me!

 

[panchothedog]

Speedster, you commented that using square tubing will be fine. That is completely true. But it doesn't look like anybody picked up on the fact that he wants to use 1.5 mm tubing. That is a wall thickness of .059". Way too thin.
It should be a minimum of .095", and even better if it were .125". He is in Spain
I think, but wherever he is, he is buying steel sold in metric sizes. I don't think he even read my comment in post #12.

 

[ARU_CC]

I was certainly taking this project more as a toy than as something so serious, my mistake, I thought I could do something low cost with the engine they were going to give me.
Well, I'm glad I wrote in this forum and won't have to regret it in the future for wasting my time and money.
It is time to be able to plan correctly and invest in the correct materials.

As you have said, I will look for a correct engine, in reality they are not expensive either, a 200cc single speed.

I will look for the square profile with a wall thickness of 3mm, or the closest they can have, I live in a small town and there are not many places where I can find these materials.

Yes, I have stick welding equipment and basic welding skills, obviously I have to practice and I will make mistakes, but that is the fun part of the project.

Sorry, I've been away for the weekend and just read all your responses. Thank you so much to everybody.

 

[Denny]

A gas power GoKart is not a toy, ever. You can get hurt or killed on one. The trick is to build in as much safety as possible. Part of that is using quality material and parts.

 

[Speedster]

Speedster, you commented that using square tubing will be fine.

Hey, I said nothing of the kind! That was ezcome-ezgo!

 

[ezcome-ezgo]

Hey, I said nothing of the kind! That was ezcome-ezgo!

Yep it was me. Didn't catch the paper thin wall thickness.