ok so building a mini chopper and need some help

[gvfc2]

well its not so mini buts its smaller then the real thing. im using an already built frame. its a Schwinn stingray frame. what i need is help on the jackshaft. i mainly want to know is if there is a jackshaft speed calculator. i dont need that much torque but i want some to get atleast 250 lbs going at first and stay going. and a top speed of about 50mph or so.

I have a robin/Subaru ex27 that a got when i bought a go kart from a metal recycling place for 170. the kart and the engine were good but i needed money and sold the go kart. the engine runs really well.

im going to be putting on either a 18 or 20" car tire on the rear. so can anyone help me. i havnt bought any sprockets or the jackshaft yet so im open to all ideas

 

[DCProductions]

Here's a thread by Dougthewelder that should be similar to what you're doing: http://www.diygokarts.com/vb/showthread.php?t=5797

Speed calculator: http://www.diygokarts.com/speed-calculator.html

Here's how I use it.

-Plug in tire size and engine rpm

-Use a calculator to calculate your positive gear ratio.
-Where it says "teeth on axle" enter whatever number you calculated (between 6 and 10 should be reasonable mini bike speed)
-Where it says "teeth on clutch" input the number 1
-Then press calculate

 

[Doc Sprocket]

50 Mph on a Schwinn? May I interest you in a large, pine box? You're a braver man than I.

 

[gvfc2]

haha well i have confidence in the bike but i will be reinforcing it a bit

 

[Redline-Go-Kart]

I had a mini chopper with a 2 stroke 49cc motor on it and it goes near 70 mph... And had it for a day and sold asap!

 

[gvfc2]

well im putting a 4 stroke 256cc or so on it. so i think it should go faster if i do it right. but i want the accel not as much as the top speed. also would like low end power

 

[mckutzy]

What I experienced on my bike, it has a spare tire for a rear tire, is that you will need to have everything in the rear precisely made, or at least the best you can. I had access to a full machine shop with lathes, mills and drill press's. The rear hub will be probably the most difficult if you dont have a lathe. A hub that is imbalanced could have big problems when at speed and with weight on. The concentrically of the axle/hub/wheel will need to pretty tight aswell.

What axle style are you choosing? Live or dead? Each is going to have some challenge with that frame style.

Depending what tire you use, it may not fit the frame you want to use. I know they have a wide rear tire, but my temp spare I know wouldn't fit a stingray. You will have to remember the OD is just important as the width with sprocket and brake rotor.

Overall I reckon, you'll need to make a completely new frame, that will take into the account of the axle style, tire width(with brake and sprocket) and OD of that tire.

These are a few thing that might be under some consideration for this build. I had been researching and planning for about a year on my build prior to me starting.

 

[gvfc2]

ive been thinking of going to completely redo the back area to allow for a wider tire on it. im not sure if im going live or dead i would need to know the difference to choose which one i would go. but ive decided to go with a tav2 torque converter from gokartsusa.

 

[mckutzy]

A live axle is one that has the tire/sprocket/brake spinning WITH axle(ie a keyed shaft),
my bike for example with jackshaft and spare temp tire

A dead axle is like most motorcycles out there, the wheel/sprocket/brake spins on the axle that doesnt move( ie dead axle).

 

[gvfc2]

well in that case im going with a live axle. so what would be the complications i would have with the live axle?

 

[machinist@large]

well in that case im going with a live axle. so what would be the complications i would have with the live axle?

I'd start by reading thru the various threads on this site; starting with Mcklutzys'. A lot of collected ideas here to help keep the hair on top of your head; instead of around your feet, one handful at a time.

 

[mckutzy]

What I found...
What types of mounting that will fit your look, Ie the axle bearings(pillow blocks or flanged bearings ). The tensioning of the rear chain will also play into the method of mounting of the axle. If the blocks are fixed to the frame (like in my build) something else has to move( my jackshaft is the rear tensioner) or have a chain tensioner (this is easier but can be a pain to find some smaller sprockets with bearings).

If the axle moves, the brake has to move with it. With some motorcycles the brake bracket is mounted to the axle and a stabilizer from this to the frame, also some brakes are mounted to the frame but are allowed to move with axle although independently. Also with a brake that is firmly fixed it needs to some how center on the rotor( cars typically use pins to slide on). On mine it has a little play in the bracket to center the brake caliper on the rotor.

Having a jackshaft also needs the motor chain to be tensioned aswell. like wise moving the motor or having a chain tensioner.


machinist@large- oh thats Mckutzy, no L......... all good

 

[gvfc2]

Well i got the bike. it was smaller then i had thought. it wasnt a stingray it was an ironhorsebikes bike from when G.I. Joe was still around. well atleast in my state. so in order to fit my engine on i have to pretty much cut everything off the frame. The whole rear end has to be redone. i forgot just how big the ex 27 is.

 

[machinist@large]

machinist@large- oh thats Mckutzy, no L......... all good[/QUOTE]

 

[gvfc2]

just updating a bit. Since i dont have a pipe bender nor can i make one i have stopped working on it for. Also i dont have the money for it. I was wondering if any of you knew how to get a custom bike made street legal? my bike is pretty much going to be as big as a small chopper.

 

[mckutzy]

My bike is as big as a small motorcycle and it will most likely not pass. Here in Canada ill need to have DOT tires and brakes, lights, signals and now have day time running lights. but most of all if the inspector doesnt like it, it wont pass. your state or province inspection location location will be able to tell you what you need.

As for needing a pipe bender, I didnt need one, ya there is a few square corners, but is isnt necessarily needed. With the round tube you can still have some different corners with miters or segmented corners, it just needs braces put in the right place.

 

[gvfc2]

well just discovered i suck at welding. using flux core gasless wire. its all blotchey and its crooked. so this one i wont bother getting trying to get street legal but it will still be fun to ride around the neighborhood. im still trying to find a tire for rear. im going with a 20"x5" tire. kind of odd size and hard to find.

 

[mckutzy]

Not to discourage you in your endeavor I do hope you come up with something, It is good that you have enough knowledge now that you are not going to try something over your head.

Most of my welding was done with gas hard wire on a professional machine at my former workplace, although later my brake bracket and few other items are done with my gasless FC 120v mig, practice is the best advice to give to you for that machine. A good source of power is one of the best things for a 120v welder. Having 15 full amps for that thing to run is great to learn with. It also allows you to know what the thing is capable of doing and not.
You need to run a few spools through it and then maybe in amongst that build something for it. Also having a welder buddy also helps this go more smoothly.

I would say that you should try for something that is somewhat common for parts and some known info (my spare doughnut's bolt pattern for ex.)

 

[gvfc2]

well thanks for the advice. would anyone know where i could get either a keyed rim with tire or a cheap 20" diameter tire(thats including rim size)thats about 5" wide?

 

[gvfc2]

Ok so this is an update. I havnt worked on it for awhile because really short on cash. Iv tried getting the frame built but I suck at cutting angles that need to be straight aprt from each other. But I lost my grinder and welder (well the owner took them back) so I have to wait for awhile. I hope I can get the cash to get all the parts I need for it before I get the grinder and welder back.