Building a mini from scratch

[Backyard Builder]

This is the very beginning of the project: the plan! Today I took some paper, a pencil and a measuring tape and figured out the basic dimensions (picture yourself a guy sitting on a chair driving an imaginary minibike while trying to read the measurements... ut: )

This is the result:

Pretty crude, I know, but you gotta start somewhere! Wheelbase is 36", seat height is 24" and handlebars height is 32". I'll go buy some 1x1 square tubing this week and start building. I'm sure the plan will change some during the build, it always does. At some point when building something, things just seem to fall into place: "this fits well here", "this should go there". I'm sure the guys at Ford do the same thing. They figure out where the spare tire should go once the car is 75% done :smile:

To be continued :hammer:

 

[65ShelbyClone]

TI'm sure the guys at Ford do the same thing. They figure out where the spare tire should go once the car is 75% done :smile:

Not before they have one of those engineers hold a heater core out in front of them about waist high and say "here, design the car around this."

Chevies, however, don't involve engineering. :thefinger:

.....just subscribing to this thread and bustin' chops in the process. :thumbsup:

 

[Qucifer]

Nice drawing, looks like it will work out great. I should be getting my rear tire tomorrow, and once that happens, I will be able to finish my homemade project. http://www.oldminibikes.com/forum/showthread.php?t=903

 

[Backyard Builder]

Looks good, Qucifer.

I'll have some progress pics soon. I started working on the frame, but my parents are on vacation and took the camera :doah: . I'll have the camera back friday.

 

[delray]

Backyard Builder,are still going to use that old briggs. if so i think it will still work for you . but will have to gear it down some with a weld on or bolt on jackshaft. engine will look cool on it,but with only 2hp or so it will have a very hard time pushing you and minibike.
........................

 

[Backyard Builder]

delray - Yep, I'm using my old 2hp briggs. The gear ratio will be 5.5:1 . It's not that low but my 120 lbs carcass is not that hard to get moving so I think it will be allright. I'm pretty sure it will be no rocket but as long as I can cruise around without having to keep it at WOT, I'm a happy man!

 

[Qucifer]

Are you going to use a centrifugal clutch, or a torque converter?

 

[Backyard Builder]

Are you going to use a centrifugal clutch, or a torque converter?

Neither. I'm going with a slipping belt clutch.

 

[Qucifer]

Wow, I dont think ive ever seen one of those used on anything but riding lawnmowers before. What happens if you cant disengage the belt fast enough, and you speeding at something?

 

[Backyard Builder]

Some pictures, finally!!!

For those who may wonder why I am using square tube, the reason is simply because I prefer working with this than with round tube. I find round tube to be a PITA to work with. With square tube you just cut your angles with a chop saw, put everything on a flat surface and weld.

Qucifer - To answer your question, if I need to stop fast I just do the same as with any vehicle: release the throttle and mash the brakes. The belt is not a problem. Heck, it may even be an advantage because it gives compression braking as much as I want. But if I need to disengage the belt for whatever reason it will only take a split second because I will use a foot pedal like in a car. My left foot will operate the clutch and my right foot will operate the brake (6 inch disc brake). Some motorcycles use this setup. Finally, if something ever goes wrong, the kill switch will be right on the handlebars.

 

[Qucifer]

Well, its looking good so far. I think the square tube this is pretty cool, something different. Also digging your motor color, did you paint it?

What color are you going to paint the bike?

 

[Backyard Builder]

Well, its looking good so far. I think the square tube this is pretty cool, something different. Also digging your motor color, did you paint it?

What color are you going to paint the bike?

Thanks :smile:

I restored this engine a few weeks ago (see the complete story here: http://www.oldminibikes.com/forum/showthread.php?t=929 ) The paint is Tremclad glossy dark blue, with Tremclad red oxyde primer underneath.

The bike will be white and blue (white frame and forks, everything else blue).

 

[Qucifer]

Cool. I havent decided what color to paint my bike. Here check out my progress
http://www.oldminibikes.com/forum/showthread.php?t=903&page=4
I need to find a color that matches my motor, and wheels.

 

[delray]

thats right Backyard Builder, we where talking about a 2 speed belt systems. are you still going with that or just one belt?
...............:thumbsup:

 

[Backyard Builder]

thats right Backyard Builder, we where talking about a 2 speed belt systems. are you still going with that or just one belt?
...............:thumbsup:

Unfortunately I had to go with just one belt. The engine shaft was just too short to fit 2 pulleys, plus it would have needed an excessively wide frame. Too bad!!!

 

[TheRedNova]

How wide is the frame?

 

[Backyard Builder]

How wide is the frame?

8½" measured on the outside of the tubes.

 

[minibikeguytlc]

I can't wait to see the belt set-up! It will be a sweet looking mini bike!

 

[Backyard Builder]

Some more progress pics. Now I have a rolling chassis and the handlebars should be completed soon. The last pic shows the twist throttle that I made using the part that holds the blade on a lawnmower (now that's recycling!).

 

[TheRedNova]

Looks good!